civil and environmental science journal vol. 02, no. 01, pp. 015-023, 2019 15 analysis of runoff coefficient value on retention ponds in flores island denik sri krisnayanti 1, wilhelmus bunganaen 1 elsy e. hangge1, farah munaisyah2, nurul a. nursyam2, dian noorvy khaerudin3 1department of civil engineering, nusa cendana university, kupang, 85001, indonesia 2graduate school of civil engineering department, nusa cendana university, kupang, 85001, indonesia 3department of civil engineering, tribuwana tunggadewi university, malang, 85001, indonesia denik.krisnayanti@gmail.com received 03-11-2018; revised 27-12-2018; accepted 28-02-2019 abstract. flores island is one of four big islands in ntt province with an area ±13,540 km2 divided into 8 districts. the area is included in areas with unequal distribution of rainfall. therefore, the amount of water availability during the dry season is relatively low then require to attempts of rainwater harvesting. one of the alternatives is by building a retention pond. the important parameter in the calculation of water availability is the value of runoff coefficient. the purpose of this research is to invent the runoff coefficient value of 30 retention ponds in 8 districts of flores island. in this study use rainfall data, climatology and technical of retention basin for the analysis of run off coefficient. the analysis method uses the penman modification for evapotranspiration calculation and method f.j. mock for discharge calculation. the result in graphical model uses monthly rainfall data and land slope data. based on the analytical calculation method, the value of run off coefficient for each district in flores was ranging 0.00 0.72. the minimum value of runoff coefficient happened in november was ranging from 0.00 0.39, and the maximum value of runoff coefficient happened in january was ranging from 0.48 0.72. keywords: retention ponds; evapotranspiration; runoff coefficient 1. introduction flores island is a region that has different climatological conditions which the western flores is wetter than eastern parts. one of the effective strategies in resolving the lack of water supply in semi-arid area, that is with harvesting rainwater as build retention pond or retention basin. the important parameter to calculate of water availability at retention ponds is the coefficient of runoff. the value of runoff coefficient is a number that shows the ratio of surface runoff occurs against the volume of rainfall in a region. runoff coefficient value needed to calculate water discharge inflow to the retention ponds. mailto:denik.krisnayanti@gmail.com civil and environmental science journal vol. 02, no. 01, pp. 015-023, 2019 16 one way to resolve the problem of lack the water availability is building the retention ponds construction. retention ponds or usually called “embung” serves as a place to store the excess water during the rainy season. the excess of rainwater is stored by "embung" can be utilized during the dry season to fulfil the requirement of water for the population, cattle, and garden. besides the rainwater falls on the surface to the retention ponds, some of the water also comes from the surface runoff [9]. run off from catchment must be adequate to meet requirements. in practise, the catchment should be neither too small nor too large [5]. first, it will not meet the requirements, and second, the rapid sedimentation caused by the silt carried by the stream. the loss in storage capacity is attributed to the accumulation of sediment in the retention ponds [4]. surface runoff occurs when the rainfall is greater than the ability of the soil to absorb water. so that the excess water flows down to the river, lake, or sea. one indicator that determines the amount of surface runoff is the value of runoff coefficient. the runoff coefficient is mentioned "high" when it close to 1.00, which indicates that more rainwater becomes the surface runoff. but if the rainwater percolate as infiltration to underground then the runoff coefficient is close to 0. figure 1. the retention pond in larantuka – flores island water availability of a retention ponds are obtained from the discharge entering the catchment area due to the high intensity rainfall. those discharge influences the value of runoff coefficient that one of important factor in water conservation for planning of retention pond development. the value of the runoff coefficient in an area also variety depends on the meteorological conditions and the land cover conditions of the watershed [8]. in this study use rainfall data, climatology and technical of retention basin for the analysis of run off coefficient. the analysis method uses the penman modification for evapotranspiration calculation and method f.j. mock for discharge calculation. evapotranspiration (ep) is the combination of two separate processes, where liquid water is converted to water vapour (vaporization) from the soil, wet vegetation, open water or other surfaces, as well as from plants by transpiration through stomata [1]. potential evapotranspiration is evaporation that affected by climatic conditions. the main weather variables affecting ep are temperature, solar radiation, wind speed and vapour pressure. the calculation of evapotranspiration method uses the penman modification method and can be formulated as follows:  ed)(eaf(u)w)(1rnwcep −−+= (1) whereas: ep = potential evapotranspiration (mm/month) civil and environmental science journal vol. 02, no. 01, pp. 015-023, 2019 17 c = adjustment factor to compensate for the day and night weather effects w = temperature and elevation related weighting factor for the effect of radiation on ep rn = net radiation (rns – rnl) in mm/day (1-w) = a temperature and elevation related weighting factor and the effect of wind humidity on ep f(u) = a wind (km/day) related function = 0.27 (1 + (u/100)) ea = saturation vapor pressure at the mean air temperature in degrees centigrade (mbar) ed = mean actual vapor pressure of air in mbar = ea (rh/100) rh = relative humidity the calculate of dependable flow by fj mock method is a calculation method based on rainfall data, evapotranspiration, and local hydrological characteristics. the calculation criteria of simulation fj mock method include analysis: (a) rainfall data, (b) limited evapotranspiration, e-epet = (2) (c) water balance, δs = p – et (3) ws = δs – ss and ws = 0 if δs < ss (4) ws = 0 if δs < ss (5) (d) runoff and groundwater storage, (6) vn =k v(n-1) + 0.5(1+k) i (7) i =ws x in (8) whereas: et = limited evapotranspiration, ep = potential evapotranspiration, e = the difference between et and ep (mm) ws = excess water (mm/month) ∆s = effective rainwater (mm/month) if ∆s <0, then the surplus water = 0 ss = groundwater content (mm) δvn = deviation of groundwater storage volume (mm/month) vn = volume of ground water deposits month n (mm/month) k = qt/qo = soil recession factor (assumed 0 1) vn-1 = volume of ground water savings month (n-1) (mm/month) i = volume of ground water savings month n (mm/month) in = infiltration coefficient (assumed 0 1) (e) dependable flow, consist of [11]: base flow (bf) = infiltration (i) – deviation the volume of ground water (δvn) direct runoff (dr) = excess water (ws) infiltration (i) flow = base flow (bf) + direct runoff (dr) (f) runoff coefficient the runoff coefficient is defined as the ratio between the peak of surface runoff to the intensity of rainfall. this factor is the most variable that determine the calculation results of flood discharge. the main factors affecting the runoff coefficient are the rate of soil infiltration or percentage of impermeable land, land slope, land covering and intensity of rainfall [10]. in the calculation of surface runoff coefficient analysis used with analytical method as follows [2]: − count the average rainfall in catchment area at the given time (t), e.g. p = mm/month, 1)(n vnδv − −= n v civil and environmental science journal vol. 02, no. 01, pp. 015-023, 2019 18 − change the unit of rainfall into m/month by multiplying 1/1,000, so that the rainfall becomes p/1,000 m/month, − count the amount of water flow in the month (t) by way of: − runoff volume = n x 86,400 x q (9) whereas: n = number of days in a month q = the average of monthly discharge (m3/s) − rainfall volume = p/1,000 x a − runoff coefficient = runoff volume/rainfall volume research and development centre for water resources, previously also had conducted an analysis of the value of runoff coefficient in retention ponds. that analysis produces the graphs that could be used to determine the value of runoff coefficients [7]. the aim of this study is to know the value of runoff coefficient on 30 retention ponds in flores island with using analytical method. the calculation results compared with graph of research and development centre for water resources [7]. 2. material and methods the calculation of runoff coefficient value has done by taking sample of 30 retention ponds in flores island that built from 2010 2014. flores island has many rainfall stations but only 12 active rainfall stations [3]. this research carried out on a few of retention ponds scattered in flores island as many as 30 (thirty) small ponds. the selected retention ponds data from eight districts in flores island are: 1) east flores : belohuko, angi marak, gajak leda, and sabu leti, 2) sikka : waer koja, mageweda, napunggelang and habiheret, 3) ende : korangawe, aenangge, tanah merah, and tubu bewa, 4) nagekeo : nunu beza, kelimeli and robo alo, 5) ngada : hoboremangai, ndoraliti, ngara i, ramba i, budhai, and tanah ewer, 6) east manggarai : waekao, komba, kempo, and hedok, 7) manggarai : kondang and pedang mari, 8) west manggarai : nara i, joneng, and waecere. figure 2. layout of flores island in east nusa tenggara civil and environmental science journal vol. 02, no. 01, pp. 015-023, 2019 19 methods carried out with: a) descriptive study, i.e. by doing literature study and collecting of secondary data such as topographic maps, precipitation data, climate data and land use of the watershed; b) qualitative research, i.e. from descriptive studies were transferred in the form of charts to be used as a reference in the calculation to criteria design of retention ponds. flow chart of the method shown in figure 3. figure 3. flow chart of the research [6] 3. result and discussion the value of surface runoff coefficient is a number that shows the ratio of the amount of surface flow that occurs as a result of the amount of rainfall that falls in a region against the volume of rainfall. the coefficient values are generally different in each region, depends on the permeability and the soil ability to keep water. data of monthly rainfall taken from rainfall stations which expected to represent phenomena of rainfall that occurred retention ponds location in flores island. the calculate of runoff coefficient with analytical and uses graph of research and development centre for water resources or called ‘puslitbang’ [7] in january shown in table 1. start literature review data collecting retention ponds data: 1. topography of catchment area 2. catchment area 3. land covering hydrology data: 1. rainfall data (2001 – 2015) 2. climatology data (2001 – 2015) calculate potential evapotranspiration using penman method calculate water balance calculate limited evapotranspiration dependable flow runoff and groundwater storage runoff coefficient: a x p/1.000 q x 86.400n x the graph of runoff coefficient civil and environmental science journal vol. 02, no. 01, pp. 015-023, 2019 20 table 1. the value of runoff coefficient on 30 retention ponds in flores island in january based on the analysis data in table 1, the value of runoff coefficient between analytical method and by using ‘puslitbang’ graph on 30 retention ponds have differences of about 23.52%. only three districts have a considerable difference i.e. sikka, ende, and in part of east manggarai. for the overall calculation of surface runoff coefficient values for each district in flores island can be seen in table 2. slope of land (m/km) analytical graph sikka waer koja < 100 181.50 0.26 0.04 sikka mageweda < 100 144.56 0.37 0.01 sikka napunggelang < 100 144.56 0.37 0.01 sikka habiheret < 100 181.50 0.26 0.04 ende korangawe < 100 289.53 0.65 0.22 ende aenangge < 100 289.53 0.60 0.48 ende tana merah < 100 289.53 0.58 0.22 ende tubu bewa < 100 253.80 0.55 0.40 nagakeo nunu beza < 100 472.20 0.68 0.62 nagakeo kelimeli < 100 472.20 0.67 0.62 nagakeo robo alo < 100 472.20 0.67 0.62 west manggarai joneng < 100 220.20 0.34 0.10 east manggarai waekao < 100 160.07 0.18 0.04 east manggarai komba < 100 160.07 0.17 0.04 ngada ndoraliti < 100 525.87 0.76 0.63 ngada budhai < 100 525.87 0.76 0.63 ngada tanah ewer < 100 525.87 0.76 0.63 east flores belohuko 100 200 372.40 0.54 0.52 east flores angi marak 100 200 372.40 0.54 0.52 east flores gajak leda 100 200 372.40 0.53 0.61 east flores sabu leti 100 200 372.40 0.52 0.61 west manggarai nara i 100 200 220.20 0.36 0.34 west manggarai waecere 100 200 220.20 0.35 0.34 east manggarai kempo 100 200 160.07 0.19 0.15 east manggarai hedok 100 200 160.07 0.17 0.15 manggarai kondamari 100 200 427.40 0.73 0.63 ngada ramba i 100 200 525.87 0.75 0.63 ngada hoboremangai 100 200 525.87 0.76 0.63 ngada ngara i 100 200 525.87 0.76 0.63 manggarai pedang > 200 427.40 0.72 0.81 dis trict re te ntion ponds monthly rainfall (mm) runoff coe fficie nt civil and environmental science journal vol. 02, no. 01, pp. 015-023, 2019 21 table 2. recapitulation of the value of runoff coefficient on 30 retention ponds in flores island table 2 shows that the value of runoff coefficient in december until april have a greater value than another month. this is because the rainfall is quite high and lead to greater runoff. thus, the filling of water ponds fulfilled in that months. in august – november, almost of all the retention ponds weren’t receiving runoff from upstream due to dry season in flores island. for the graph of runoff coefficient against high of monthly rainfall and slope of the land in january april shown in figure 3. jan feb march apr may jun jul aug sept oct nov dec belohuko 0.538 0.554 0.472 0.432 0.283 0.952 0.107 0.081 0.004 0.000 0.000 0.274 angi marak 0.536 0.540 0.472 0.431 0.282 0.948 0.106 0.080 0.004 0.000 0.000 0.286 gajak leda 0.533 0.549 0.467 0.426 0.276 0.935 0.105 0.079 0.003 0.000 0.000 0.269 sabu leti 0.523 0.539 0.458 0.413 0.261 0.898 0.101 0.076 0.003 0.000 0.000 0.259 waer koja 0.264 0.314 0.262 0.333 0.367 0.126 0.574 0.010 0.002 0.000 0.012 0.239 mageweda 0.372 0.373 0.418 0.451 0.413 0.340 0.089 0.000 0.004 0.001 0.000 0.201 napunggelang 0.373 0.375 0.420 0.453 0.415 0.342 0.089 0.000 0.004 0.001 0.000 0.201 habiheret 0.261 0.324 0.279 0.350 0.380 0.131 0.120 0.010 0.002 0.000 0.019 0.251 korangawe 0.652 0.643 0.598 0.511 0.417 0.282 0.086 0.055 0.304 0.104 0.031 0.477 aenangge 0.599 0.574 0.531 0.413 0.292 0.168 0.056 0.035 0.261 0.054 0.004 0.399 tana merah 0.577 0.551 0.511 0.383 0.255 0.133 0.046 0.030 0.248 0.039 0.003 0.382 tubu bewa 0.554 0.611 0.551 0.533 0.434 0.160 0.102 0.040 0.533 0.273 0.030 0.445 nunu beza 0.680 0.645 0.542 0.548 0.374 0.482 0.386 0.228 0.208 0.153 0.383 0.633 kelimeli 0.675 0.637 0.530 0.537 0.361 0.475 0.368 0.222 0.200 0.146 0.375 0.629 robo alo 0.674 0.637 0.530 0.536 0.360 0.475 0.367 0.221 0.199 0.145 0.375 0.628 budhai 0.756 0.780 0.768 0.713 0.627 0.601 0.459 0.337 0.281 0.184 0.580 0.685 hoboremangai 0.756 0.781 0.769 0.714 0.628 0.602 0.460 0.339 0.282 0.185 0.580 0.685 ndoraliti 0.760 0.785 0.774 0.720 0.636 0.606 0.461 0.347 0.285 0.191 0.585 0.688 ngara i 0.761 0.786 0.777 0.722 0.640 0.608 0.462 0.351 0.287 0.194 0.587 0.690 ramba i 0.754 0.777 0.759 0.699 0.598 0.588 0.426 0.301 0.278 0.162 0.569 0.682 tanah ewer 0.760 0.784 0.774 0.720 0.636 0.606 0.461 0.347 0.285 0.191 0.585 0.688 hedok 0.168 0.218 0.209 0.164 0.050 0.037 0.170 0.060 0.013 0.006 0.148 0.175 kempo 0.192 0.246 0.238 0.187 0.057 0.041 0.170 0.061 0.013 0.020 0.161 0.197 komba 0.172 0.223 0.214 0.169 0.052 0.038 0.170 0.060 0.013 0.009 0.151 0.179 waekao 0.175 0.227 0.218 0.172 0.052 0.038 0.170 0.060 0.013 0.011 0.152 0.182 kondamari 0.731 0.781 0.759 0.823 0.779 0.651 0.409 0.225 0.354 0.409 0.639 0.707 pedang 0.725 0.776 0.754 0.818 0.771 0.639 0.404 0.220 0.346 0.400 0.633 0.702 embung joneng 0.343 0.212 0.228 0.233 0.152 0.077 0.037 0.089 0.011 0.002 0.000 0.197 nara i 0.355 0.230 0.241 0.241 0.166 0.082 0.039 0.102 0.013 0.002 0.000 0.211 waecere 0.346 0.216 0.231 0.235 0.155 0.079 0.037 0.092 0.012 0.002 0.000 0.200 maximum 0.761 0.786 0.777 0.823 0.779 0.952 0.574 0.351 0.533 0.409 0.639 0.707 minimum 0.168 0.212 0.209 0.164 0.050 0.037 0.037 0.000 0.002 0.000 0.000 0.175 average 0.519 0.523 0.492 0.469 0.372 0.405 0.235 0.139 0.149 0.096 0.220 0.415 monthname of retention ponds civil and environmental science journal vol. 02, no. 01, pp. 015-023, 2019 22 (a) january (b) february (c) march (d) april figure 4. graph high of monthly rainfall and slope of the land against runoff coefficient in the western part of flores island based on figure 4 can be seen that the value of runoff coefficient in january and february has a tendency higher than march april. in addition, the value of runoff coefficient is evenly distributed at the height of monthly rainfall than in march april. the difference value of calculation in january april has ranging 10 20% higher than graph data from research and development centre for water resources [7]. this is due to the transfer of land functions from forests into gardens or housing that make a lack of the catchment areas and decreasing 0,00 0,10 0,20 0,30 0,40 0,50 0,60 0,70 0,80 0,90 100 200 300 400 500 600 r u n o ff c o e ff ic ie n t monthly rainfall (mm) analysis of calculate (land slope <100 m/km) analysis of calculate (land slope 100-200 m/km) graph data (land slope <100 m/km) graph data (land slope 100-200 m/km) 0,00 0,10 0,20 0,30 0,40 0,50 0,60 0,70 0,80 0,90 100 150 200 250 300 350 400 450 500 r u n o ff c o e ff ic ie n t monthly rainfall (mm) analysis of calculate (land slope <100 m/km) analysis of calculate (land slope 100-200 m/km) graph data (land slope <100 m/km) graph data (land slope 100-200 m/km) 0,00 0,10 0,20 0,30 0,40 0,50 0,60 0,70 0,80 0,90 1,00 100 150 200 250 300 350 400 450 500 r u n o ff c o e ff ic ie n t monthly rainfall (mm) analysis of calculate (land slope <100 m/km) analysis of calculate (land slope 100-200 m/km) graph data (land slope <100 m/km) graph data (land slope 100-200 m/km) 0,00 0,10 0,20 0,30 0,40 0,50 0,60 0,70 0,80 0,90 1,00 50 100 150 200 250 300 350 400 r u n o ff c o e ff ic ie n t monthly rainfall (mm) analysis of calculate (land slope <100 m/km) analysis of calculate (land slope 100-200 m/km) graph data (land slope <100 m/km) graph data (land slope 100-200 m/km) civil and environmental science journal vol. 02, no. 01, pp. 015-023, 2019 23 green land cover. it is resulting in greater surface runoff when it rains. land-use and land-cover changes may have direct impacts on the hydrological cycle: they can cause floods, droughts, and changes in river and groundwater regimes [12]. 4. conclusions the value of runoff coefficient by analysis for 30 retention ponds in flores island is as follows: a) west flores (west manggarai, manggarai, east manggarai, ngada and nagekeo) have the average of runoff coefficient value 0.12 – 0.61. the highest average of runoff coefficient value in manggarai, ngada, and nagekeo. while other region has a low runoff coefficient value; b) east flores (ende, sikka, and east flores) have the average of runoff coefficient value 0.21 – 0.31. the value of runoff coefficient in this region lower because the eastern regions in flores of the climate are drier so that the soil characteristic is more porous. the runoff coefficient value based on analysis of calculate tends to be higher when compared with graph data from research and development centre for water resources. this is due to the transfer of land functions or change land covering in catchment area. it is resulting in greater surface runoff when it rains. acknowledgements the authors thank to the ministry of technology research and higher education indonesia in the financial support of the program of applied product research in 2015 2017. references [1] allen, r.g. pereira,l.s. raes, dirk. smith, martin. 1998. crop evapotranspiration guidelines for computing crop water requirements fao irrigation and drainage paper 56. rome. [2] asdak, c. 2010. hydrology and watershed management. gadjah mada university press, yogyakarta. [3] department of public works, ntt province. 2011. final report “planning study of 15 retention ponds in timor island, rote and alor”, pt. indra karya, kupang. [4] heitz, l.f. khosrowpanah, s. nelson, j. 2000. sizing of surface water runoff detention ponds for water quality improvement, journal of the american water resources association. volume 36, issue 3, pages 541–548. [5] lewis, b. 2014. small dams. planning, construction, and maintenance. crc press. london, uk. [6] krisnayanti,d.s. bunganaen,w. 2015. the graph analysis of run off coefficient values on small ‘embung’ design criteria in south central timor ntt. proceeding of national conference 3rd, faculty of civil engineering and planning, uii, yogyakarta. [7] kasiro, dkk. 1994. guideline for ‘small embung’ design criteria for semiarid area in indonesia. research and development centre for water resources, department of public works. jakarta. [8] sosrodarsono. 2003. hydrology for irrigation. department of public works and electric power. pt. pradnya paramita. jakarta. [9] soemarto, c. d. 1986. hydrology technique. pt. erlangga. jakarta. [10] suripin. 2004. development of sustainable drainage system. andi offset, yogyakarta. [11] sutapa, i wayan. 2015. study water availability of malino river to meet the need of water requirement in district ongka malino, central sulawesi of indonesia. international journal of engineering and technology, vol 7 no 3 jun-jul 2015. tamil nadu, india. [12] weng, q. 2001. modeling urban growth effects on surface runoff with the integration of remote sensing and gis. environmental management vol. 28, no. 6, pp. 737–748. springerverlag new york inc. civil and environmental science journal vol. 5, no. 1, pp. 001-007, 2022 1 identification of surface water treatment plant (wtp) effluent and distribution water quality in wonogiri regency, central java whindy ndaru oktaviani, ariyanti sarwono, i wayan koko suryawan* faculty of infrastructure planning, department of environmental engineering, universitas pertamina, komplek universitas pertamina, jalan sinabung ii, terusan simprug, jakarta 12220, indonesia1 *i.suryawan@universitaspertamina.ac.id received 08-09-2021; accepted 09-11-2021 abstract. this study analyzed the water treatment system into drinking water, and the quality of raw water and distribution results at perumda air minum giri tirta sari, wonogiri regency. the water treatment plant's (wtp) for surface water consists of intake, pre-sedimentation, coagulation, flocculation, sedimentation, filtration, reservoir storage, and distribution. the sludge resulting from the deposition process is still not managed. further planning is needed to control environmental pollution that may occur due to dumping sludge into streams. the quality of river raw water that has not met the quality standard is total coliform and color. measurement of water on the customer's tap shows that all the quality standards of drinking water have met the criteria to be safe for use by residents. keywords: drinking water, environment, sludge, water quality, wtp 1. introduction the availability of clean water is an absolute aspect to support all human activities. sufficient water availability in terms of quality, quantity, and continuity is essential for human survival [1]. based on government regulation number 16 of 2005, to meet the community's need for clean water with a stipulated minimum service standard is the responsibility of the district/city government. increasing water needs and conditions make it impossible for people to use groundwater and surface water directly. to get groundwater, people have to dig deep wells. using surface water directly is impossible because the water quality conditions do not physically meet clean water requirements [2]. the regency/city government formed a regional company called the regional drinking water company (pdam) from these problems. pdam is a regional owned enterprise (bumd) that provides clean water for profit to residents in an area [3]. perumda air minum giri tirta sari is a regional company providing clean water serving the wonogiri regency. perumda air minum giri tirta sari 1 cite this as: oktaviani, w. n., sarawoko, a., & suryawan, i.w.k. (2022). identification of surface water treatment plan (wtp) effluent and distribution water quality in wonogiri regency, central java. civil and environmental science journal (civense), 5(1), 1-7. doi: https://doi.org/10.21776/ub.civense.2022.00501.1 civil and environmental science journal vol. 5, no. 1, pp. 001-007, 2022 2 utilizes three raw water sources: surface water, groundwater, and spring water to meet the clean water supply. however, municipal activities will increase water pollution [4], [5]. it is necessary to process the raw water to meet health requirements and is suitable for consumption. the process of processing raw water into clean water varies with each source of raw water used. various pollutants in streams water sources need more techniques to meet quality standards [6], [7]. based on this background, a performance study of the water treatment plant (wtp) was conducted at perumda giri tirta sari drinking water to meet clean water needs in the wonogiri regency. this study aims to analyze implementing the practice of processing raw water into clean water and the quality of drinking water produced from perumda drinking water giri tirta sari. 2. material and methods field observation activities were carried out by looking at the entirety of the water treatment plant (wtp) building. the wtp building is at the kajen wtp located on jalan jambu air no. 1, kajen, giriprwo, wonogiri regency, and grobog wtp located in wonogiri district. this activity aims to learn about the work environment and water treatment in the kajen wtp and the grobog wtp. the author made joint observations with one of the staff from the production department. the activities started from the intake building to the reservoir and wtp supporting facilities such as storage rooms for chlorine gas cylinders, storage tanks, and pump rooms. literature studies were carried out through direct interviews with agency supervisors and production staff. this activity aims to obtain information about the water treatment process at perumda giri tirta sari drinking water and water treatment in general. literature studies, both interviews and online article sources, were carried out during this study. water quality data is taken from the monthly report of the perumda air minum giri tirta sari production section. the method of measuring water quality can be seen in table 1. this measurement method is carried out in a laboratory that has been standardized by the national standardization agency (bsn) so that the method used is adjusted to existing standards in indonesia. table 1. method of measuring water quality parameters parameters method total coliform dual tube mpn odor organoleptic tds tds meter turbidity turbidimeter taste organoleptic temperature digital color spectrophotometry fe spectrophotometry mn spectrophotometry nitrate as n spectrophotometry nitrite as n spectrophotometry chloride spectrophotometry ph ph meter organic substances (kmno4) titrimetry hardness (caco3) titrimetry 3. result and discussion 3.1 surface water treatment system kajen wtp is the perumda air minum giri tirta sari which utilizes the bengawan solo river as a raw water source. the water treatment process uses physical and chemical processing. the water treatment process can be seen in figure 1. water from the bengawan solo river is flowed to the intake building using three pumps, each of which can flow water with a discharge of 29 l/sec, 22 l/sec, and civil and environmental science journal vol. 5, no. 1, pp. 001-007, 2022 3 18 l/sec. the intake building is equipped with a chlorine affixing process to prevent moss growth on the installation unit. the water from the intake has then flowed into the coagulation tub with the waterfall system. the coagulant used is a liquid alum (cma) at a dose of 10 ml/s. the water is flown into a slow lane which aims to form larger flocks. there is a deposition of solids in the sedimentation unit in sludge, also known as production waste. the sedimentation basin is equipped with a settler which functions to accelerate the deposit. the water separated from the solid is drained to the filtration basin to be filtered using three medium sand media. these conditions aim to capture small particles that are difficult to settle. clean water from the filtration tub has flowed to the reservoir, and then chlorine is added as a disinfectant. some clean water reservoirs have flowed for distribution purposes, and some are stored for the tub's washing process. the intake is a building used to flow raw air to the reservoir before entering the water treatment process. the intake building is equipped with a bar screen or filters helpful in holding or filtering trash or leaves from entering the pump and clogging the air suction. the type of intake found in the kajen wtp is a channel type. the coagulation process in water treatment is collecting small particles such as clay, turbidity, and organic matter into larger particles separated by sedimentation, conventional filtration, or membranes [8]. coagulation in kajen wtp is done by adding chemicals (coagulants) to raw water. this affixing aims to bind the particles in the raw water at perumda giri tirta sari; drinking water uses liquid alum (cma) as a coagulant. the sedimentation basin consists of 2 parts, namely the settling basin and the settler bath. the use of settlers aims to help settle small flocks to not carry over to the following process [8]. the type of settler used is a tube settler. the sediment in the sedimentation basin is in the form of sludge, also known as production waste. kajen wtp uses a rapid sand filter type of filtration with three media: quartz sand, gravel, and a filtering membrane. the filtering media's replacement is carried out for 2-3 years to maximize the filtering results. figure 1. flow chart of river water treatment to drinking water in the kajen wtp, the resulting sludge is not treated before being discharged into the environment. some of the suggestions given are planning for storage and processing of production sludge, testing the civil and environmental science journal vol. 5, no. 1, pp. 001-007, 2022 4 chemical content of production sludge before being discharged into water bodies, and reusing production sludge as a mixture of building materials [9]. however, before it is further utilized, the sludge originating from the sediment tank and filter tub has flowed to the collector as a place to fill the sludge temporarily, gravity thickening unit, dewatering unit, and conditioning [10]. sewerage sludge also can contribute to carbon emissions and cause greenhouse impacts [11]. however, this requires further research regarding the chemical content contained in the production sludge. before being distributed, the treated water is collected in a reservoir and then disinfected. there are three types of disinfectants used, namely chlorine powder, chlorine tablets, and chlorine gas. there is a disinfection process in the reservoir at kajen wtp by flowing chlorine gas (cl2) to kill bacteria in the treated water. however, when the chlorine gas supply runs out or is under repair, usually the disinfection process uses chlorine powder. table 2. results of raw water quality inspection at grobog [15] no parameters raw water quality distribution water quality removal efficiency (100%) standard permenkes no. 32 of 2017 unit a. biology 1. total coliform 460 0 100 <50 /100 ml sample b. physics 1. odor odorless odorless odorless 2. tds 97 105 1000 mg/l 3. turbidity 5.44 0.77 85.8 25 ntu 4. taste tasteless tasteless tasteless 5. temperature 28.8 28.9 air temperature ±3 °c 6. color 70 <1 >98.6% 50 tcu c. chemistry 1. fe 0.15 0.04 73.3 1 mg/l 2. mn 0.4 0.05 87.5 0.5 mg/l 3. nitrate as n <1 1.8 10 mg/l 4. nitrite as n 0.01 <0.01 1 mg/l 5. chloride 14.08 11.66 17.2 800 mg/l 6. ph 8.7 7.3 6.5-8.5 7. organic substances (kmno4) 4.18 10 mg/l 8. hardness (caco3) 79.8 500 mg/l 3.2 raw water and water treatment quality before going through the processing process, the quality of raw water originating from surface water is not good enough. for example, from the examination results of the grobog wtp raw water from gajah mungkur reservoir, three parameters exceed the quality standard, namely total coliform with a content of 460 per 100 ml color with a range of 70 tcu and ph of 8.7. fathoni et al. stated that population density is an early indicator of bacteria used to determine whether water is safe or not for consumption [12]. the absence of coliform bacteria is an indicator of the quality and safety of drinking water. the lack of these bacteria is expected to indicate the absence of other pathogens [13]. the inspection of raw water quality from the grobog wtp in may 2020 can be seen in table 2. from the results of laboratory examinations carried out as in table 2, the microbiological parameters, color, and ph do not meet the quality standards contained in permenkes no. 32 of 2017 for microbiological parameters of <50 per 100 ml sample, 25 ntu color parameters, and a ph of 6.5-8.5 [14]. after it is processed and distributed to the community, water quality measurements have met the required biology, physics, and chemistry requirements. civil and environmental science journal vol. 5, no. 1, pp. 001-007, 2022 5 4. conclusions treatment of raw water into clean water has a different process according to the raw water quality. treatment of raw water originating from surface water requires the installation of an intake unit, coagulation, flocculation, sedimentation, filtration, and disinfection. water from springs only requires installing a ground capturing unit, a press release bath, filtration, and disinfection. meanwhile, water from deep wells only involves the installation of a water tapping and disinfection unit. the efficiency of water treatment on the parameters of turbidity, color, fe, mn, and chlorine reached 85.8%, >98%, 73.3, 87.5, and 17.2%, respectively. after going through the processing process, raw water that contains parameters that exceed the quality standard has met the clean water standard following the minister of health regulation no. 32 of 2017 concerning environmental health quality standards and water health requirements for hygiene, sanitation, swimming pools, souls per aqua, and public baths. acknowledgment the author would like to thank the perumda air minum giri tirta sari for this study, initiative, and support. the author also thanks to the universitas pertamina environmental engineering department admin for assistance with the administrative process. references [1] n. f. arifiani and m. hadiwidodo, “evaluasi desain instalasi pengolahan air pdam ibu kota kecamatan prambanan kabupaten klaten,” j. presipitasi, vol. 3, no. 2, pp. 78–85, 2007, doi: 10.14710/presipitasi.v3i2.78-85. [2] n. fadhilah, l. alvin, w. vembrio, and r. h. safira, “modifikasi unit proses dalam peningkatan efisiensi penyisihan amonium modification of process unit to improve ammonium removal efficiency,” jsal, vol. 7, no. 2, pp. 47–56, 2020. [3] r. triningtyas, “pelaksanaan pelayanan pdam kota malang dalam penyediaan air bersih yang sehat berdasarkan peraturan direksi pdam kota malang nomor u/06 tahun 2010. kumpulan,” j. mhs. fak. huk., 2015. [4] e. s. sofiyah and i. w. k. suryawan, “cultivation of spirulina platensis and nannochloropsis oculata for nutrient removal from municipal wastewater,” rekayasa, vol. 14, no. 1, pp. 93–97, 2021, doi: 10.21107/rekayasa.v14i1.8882. [5] a. s. afifah, i. w. k. suryawan, and a. sarwono, “microalgae production using photo-bioreactor with intermittent aeration for municipal wastewater substrate and nutrient removal,” commun. sci. technol., vol. 5, no. 2, pp. 107–111, 2020, doi: 10.21924/cst.5.2.2020.200. [6] h. hasnaningrum, b. ridhosari, and i. suryawan, “planning advanced treatment of tap water consumption in universitas pertamina,” j. tek. kim. dan lingkung., vol. 5, no. 1, p. 1, 2021, doi: 10.33795/jtkl.v5i1.177. [7] i. w. k. suryawan, q. helmy, s. notodarmojo, r. pratiwi, and i. y. septiariva, “indonesian journal of environmental management and sustainability textile dye reactive black 5 ( rb5 ) bio-sorption with moving bed biofilm reactor and activated sludge,” vol. 5, 2021. [8] n. g. pizzi, principles and practices of water supply opertions: water treatment. west quancy avenue. american water works association, 2003. [9] n. nuryanti, r. arizal, and d. arrisujaya, “kandungan kimia dari limbah lumpur instalasi pengolahan air minum untuk beton geopolimer dengan xrf chemical containt of waste water installation of drinking water treatment for geopolymer concrete by xrf,” j. sains nat., vol. 7, no. 2, pp. 48–57, 2017. [10] n. rahayu, septiya rini; arqowi pribadi; sulistiya, n. diah, and setyowati, “perencanaan unit pengolahan lumpur di instalasi pengolahan air minum x kota surabaya,” j. teknol. technoscientia, vol. 13, no. 1, pp. 76–82, 2020. [11] m. r. apritama, i. suryawan, and y. adicita, “analisis hidrolis dan jejak karbon jaringan distribusi air bersih di pulau kecil padat penduduk (pulau lengkang kecil, kota batam),” j. teknol. lingkung., vol. 21, no. 2, pp. 227–235, 2020, doi: 10.29122/jtl.v21i2.3807. civil and environmental science journal vol. 5, no. 1, pp. 001-007, 2022 6 [12] a. fathoni, s. khotimah, and r. linda, “kepadatan bakteri coliform di sungai segedong kabupaten pontianak,” j. protobiont, vol. 5, no. 1, pp. 20–23, 2016, [online]. available: https://jurnal.untan.ac.id/index.php/jprb/article/view/14810. [13] f. s. melinda, s. rudiyanti, and haeruddin, “status pencemaran perairan waduk jatibarang kota semarang pada berbagai kegiatan peruntukan,” j. maquares, vol. 8, no. 3, pp. 118–125, 2019. [14] kementerian lingkungan hidup dan kehu tanan republik indonesia, “no title,” peratur. menteri kesehat. republik indones. nomor 32 tahun 2017 tentang standar baku mutu kesehat. lingkung. dan persyaratan kesehat. air untuk keperluan hig. sanitasi, kolam renang, souls per aqua, dan pemandian umum, 2017. [15] pdam giri tirta, “water quality data is taken from the monthly report of the perumda air minum giri tirta sari production section.,” 2020. open access proceedings journal of physics: conference series civil and environmental science journal vol. i, no. 02, pp. 088-095, 2018 88 analysis of waikelo port breakwater failure through 2d wave model bambang winarta1, a. a. n satria damarnegara2, nadjadji anwar2, pitojo tri juwono1 1water resources engineering department, universitas brawijaya, malang, 65145, indonesia 2civil engineering department, institut teknologi sepuluh nopember, surabaya, 60111, indonesia bwinarta@gmail.com / bambang.winarta@ub.ac.id received 26-07-2018; revised 30-08-2018; accepted 29-09-2018 abstract. waikelo port is located in south west sumba of east nusa tenggara. the port facilities are protected by breakwater with a vertical wall construction and it was built in a relatively deep ocean at -15m of low water sea level (lws). on 21st of january 2012, an earthquake with magnitude of 6.3 richter scale occurred around sumba island and it caused cracking in the concrete wall of breakwater. then, 4 days after on 25th january 2012, a heavy wind of 20–23 knots generated a high wave around 4.0–5.0m in sumba strait. these high waves caused a critical damage on the west part of the breakwater. the damage of port facilities were getting worse when a storm called lua hit on march 2012. this study was conducted to observe the effect of the extreme event in the failure of breakwater. the result of two-dimensional (2d) wave model shows that the wave heights in the area of breakwater are varied 3.80 to 4.0m. it is quite greater than the wave design of 50 years return period (= 2.00m) which was used in breakwater design and calculation. this observable fact confirms that the failure of breakwater was caused by the continuous extreme events that exceed the design criteria. keywords: waikelo port, breakwater failure, extreme event, 2d wave model 1. introduction the reasons for breakwater failures can be classified in three major categories (a) reasons relate to the structure itself, (b) reasons relate to the hydraulic and loads conditions, and (c) reasons relate to the foundation and seabed change [1]. the possibility causes in term of the hydraulic and load conditions type are exceedance of design wave condition, concentration of wave action at certain zones along breakwater, breaking wave and impact loads and wave overtopping. waikelo port is located in north west sumba, the province of east nusa tenggara and it is used for inter island transportation. this port was established in 2011 and placed by the waikelo sea port. the waikelo port is equipped a movable bridge and protected by a vertical wall construction breakwater. the breakwater itself was constructed in -15m of lws and calculated based on the design wave of 50 years return period which was equal to 2.00m mailto:bwinarta@gmail.com mailto:bambang.winarta@ub.ac.id civil and environmental science journal vol. i, no. 02, pp. 088-095, 2018 89 figure 1. location of study, waikelo port, south west sumba, east nusa tenggara civil and environmental science journal vol. i, no. 02, pp. 088-095, 2018 90 the consecutive extreme events hit waikelo port was started on january 21st, 2012, when 6.3 richter scale earthquakes occurred around sumba island. this earthquake caused the breakwater to crack in the concrete wall as displayed in figs. 2, 3. then, the next 4 days, the second severe events occurred. a heavy wind of 20–23 knot generated a huge wave around 4.0–5.0m and struck waikelo port and also its facilities. this high wave caused the west part of the breakwater around 24.95m length fail. the next massive events happened on march 2012; a storm called lua blew waikelo port in 5 days continuously and caused crucial damage in the port facilities as shown in figs. 4, 5. by considering the chronologic extreme events as menti0ned before, the main objective of this present study is to analysis and review the breakwater failure through 2d wave propagation model. figure 2. cracking on breakwater concrete wall after an earthquake on january 21st, 2012. figure 3. significant damage of breakwater due to high wave on january 25th, 2012 figure 4. major damage of port facilities after lua storm on march 2012. figure 5. major damage on movable bridge after lua storm on march 2012. 2. wave generation and propagation heavy winds blow above the sea with enormous fetches acting for lengthy durations, possibly generating high and huge sea waves. wave storms are usually described as events of significant wave height, hs, overreaching a predetermined threshold (critical hs) with a short duration. 2.1. wind wave generation the height, length and period of wind waves in the open ocean are generated by the fetch, the wind speed, the duration of the wind blows, the distance of the wave travels and the water depth. general speaking, increasing in fetch length, wind speed and or duration will be generating a huge wind waves. then, in term of the water depth, when it is sufficiently shallow, it will also determine on the size of civil and environmental science journal vol. i, no. 02, pp. 088-095, 2018 91 wave propagation. the wind simultaneously creates waves of various heights, lengths and periods as it blows above the sea. data used in this present study was obtained from indonesia meteorological, climatological and geophysical agency (bmkg) which has located in kupang. based on bmkg record, it has increased significantly of wind speed and wave height during 10 days since 21st to 31st of january 2012 in sumba strait. bmkg recorded data informed that on january 25th, 2012 wind speed blew at 20–23 knots from north west direction with the significant wave height, hs, was at 2.50–3.00m and the maximum wave height, hmax, reached 4.0–5.0m. in order to verify recorded significant wave height data, subsequently, the wind wave heights on january 21st–31st, 2012 was calculated by considering fetch length as displayed and tabulated in fig. 6 and tabel 1. table 1. calculations of waikelo port fetch length direction north west (= 315°)  cos xi (km) xi × cos 42 0.743 69.310 51.507 36 0.809 91.338 73.894 30 0.866 77.510 67.126 24 0.914 74.966 68.485 18 0.951 77.255 73.474 12 0.978 81.628 79.844 6 0.995 77.128 76.705 0 1.000 81.476 81.476 -6 0.995 96.492 95.963 -12 0.978 105.134 102.837 -18 0.951 138.176 131.413 -24 0.914 154.359 141.014 -30 0.866 2.891 2.504 -36 0.809 2.351 1.902 -42 0.743 2.050 1.523 cos : 13.511 xi × cos : 1049.667 figure 6. mapping scheme for fetch length calculation of waikelo port civil and environmental science journal vol. i, no. 02, pp. 088-095, 2018 92 based on the calculation result as written in table 1, the effective fetch (fetcheff) can be obtained by using a simple formula as written below, fetcheff = ( ) 690.77 511.13 667.1049 cos cos ==    xi km then, recorded wind speed (u) was 23 knot or equal to 11.832m/s, thus wind stress factor (ua) = 0.71u1.23 = 14.830m/s and the significant wave height (hs) = 1.616 x 10 -2 ua fetcheff 0.5 = 2.112m. this calculated significant wave height is near to bmkg recorded data at 2.50–3.00m. furthermore, maximum wave height can be calculated using simple and practical equation proposed by goda [2] that hmax = 1.8hs = 3.80m. this value is also close to bmkg recorded data at 4.0-5.0m. 2.2. 2d wave model two-dimensional spectral wave model with energy dissipation and diffraction terms was used in this current study. it simulates a steady-state spectral transformation of directional random waves simultaneous with ambient currents in the coastal area. 2d wave model in here is based on the waveaction balance equation [3]. ( ) ( ) ( ) ( ) snn cc ncc nc y nc x nc byy g yyg yx −−      −=   +   +        22 cos 2 cos 2 (1) where: ( )   ,e n = (2) is the wave-action density as a function of frequency σ and direction θ. e(σ,θ) is spectral wave density representing the wave energy per unit water surface area per frequency interval. execution of the numerical scheme of those governing equation are explained in some literatures [3, 4]. cx, cy and cθ are the velocity characteristic with respect to x, y, and θ direction; ny and nyy symbolize the first and second derivatives of n with respect to y; c and cg are wave celerity and wave group velocity; then, κ is an empirical factor which depicted the magnitude of diffraction; εb is the energy dissipation during wave breaking parameter; s means additional sources such as: bottom friction loss, wind strength and interaction of nonlinear wave. 2.2.1. wave diffraction. the first term on the right side of equation 1 is the wave diffraction term derived from a parabolic approximation wave theory [3]. in application practice, values of κ are in between 0 with no diffraction to 4 for strong diffraction. a value of κ = 2.5 was used by [3, 4, 5] to model wave diffraction for both narrow and wide gaps between breakwaters. κ value = 4 is recommended for wave diffraction at a semi-infinite long breakwater or at a narrow gap case with the opening equal or less than one wavelength. in the case of a fairly wider gap with an opening greater than one wavelength, the value of κ is equal to 3. 2.2.2. wave reflection. the wave energy reflected at a shoreline is computed in assumptions of the incident and reflected wave angles are proportional to the shore normal direction and the reflected wave nr is assumed to be linearly relative to the incident wave ni : irr nkn 2 = (3) where kr is a coefficient of reflection, kr = 0 for no reflection and kr = 1 for full reflection. kr is defined as the ratio of reflected to incident wave height [6]. civil and environmental science journal vol. i, no. 02, pp. 088-095, 2018 93 refraction diffraction analysis were made using two dimensional 2d wave model at steady state condition with model grid 5 x 5m2 as displayed in fig. 7. 2d wave model analysis in here used bmkg data recorded on january 25th, 2012 when the wave height was varied from 4.0m–5.0m and strong wind blew from north west direction. two scenarios of wave model have been developed to simulate wave height in surround breakwater. there are 4 (four) examination points (a, b, c, d) to observe wave height generation due to significant wave height, hs, of 4.00m and 5.00m as displayed in fig. 8. figure 7. numerical model bathymetry grid for 2d wave model of waikelo port figure 8. examination points (a, b, c, d) of 2d wave model simulation in surround breakwater civil and environmental science journal vol. i, no. 02, pp. 088-095, 2018 94 3. result and discussion the simulation result of developed 2d wave model from 2 of significant wave height scenarios at 4.0 and 5.0m are displayed in figs. 9, 10, 11, and 12. figure 9. simulated wave propagation due to 4.0m of significant wave height (hs). figure 10. distribution of wave height in surround breakwater due to hs = 4.0m. figure 11. simulated wave propagation due to 5.0m of significant wave height (hs). figure 12. distribution of wave height in surround breakwater due to hs = 5.0m. based on the result of 2d wave model as shown in figs. 9, 10, 11 and 12 above, it can be seen clearly the variation of wave height in 4 examination points (a, b, c, d) in front and back side of breakwater. the details are summarized in table 2. table 2. simulated wave height in surround breakwater examination points hs = 4.0 m hs = 5.0 m front side (m) back side (m) front side (m) back side (m) a 4.31 2.22 5.87 2.73 b 4.14 1.55 4.79 1.72 c 3.82 1.53 4.65 1.64 d 3.80 1.83 4.75 1.73 civil and environmental science journal vol. i, no. 02, pp. 088-095, 2018 95 from the diffraction and refraction analyses inform that the wave height in front side of breakwater is varied from 3.80m to 5.87m. this value is much higher than 50 years return period of wave design (2.00 meters) which is used as a calculation reference of breakwater structure. 4. conclusions calculation of wave generation based on wind speed on january 25th, 2012 at 23 knot, produce significant wave height 2.11m and maximum wave height 3.80m. those calculation results are quite close to recorded data by bmkg. based on the result of 2d wave model simulation, it can be concluded that the wave height in surround breakwater is higher than wave design of 50 years return period which is used in design and calculation of breakwater structure. the reasons of waikelo port breakwater failure can be classified in reasons relate to the hydraulic and loads conditions: exceedance of wave condition and it can be categorized also in force majeure type. references [1] oumeraci h., 1994. review and analysis of vertical breakwater failures lessons learned, coastal engineering 22, pp 3-29 [2] goda y., 1985. random seas and design of maritime structure (university of tokyo press) [3] mase h., 2001. multidirectional random wave transformation model based on energy balance equation, j. coastal engineering 43(4), pp 317-337 [4] mase h., amamori h. and t. takayama t., 2005a. wave prediction model in wave-current coexisting field, proc. 12th canadian coastal conference [5] mase h., oki k., hedges t. s., li h. j. and morkoc h., 2005b. extended energy-balance-equation wave model for multidirectional random wave transformation, ocean engineering 32 (8-9), pp 961-985 [6] dean r. g. and dalrymple r. a., 1984. water wave mechanics for engineers and scientists englewood cliffs (prentice-hall, inc) open access proceedings journal of physics: conference series civil and environmental science journal (civense) vol. i, no. 02, pp. 080-087, 2018 80 analysis of drainage capacity and rehabilitation subjected to rainfall and reverse flow of marengan river as a main drain in sumenep city, indonesia evi nur cahya1, ussy andawayanti1, eva resmani2 1water resources engineering department, universitas brawijaya, malang, 65145, indonesia 2office of public work, water resources departement, sumenep residence, indonesia evi_nc@ub.ac.id received 20-07-2018; revised 23-08-2018; accepted 27-09-2018 abstract. land use changing in sumenep city in recent years has caused runoff in several locations. therefore, rehabilitations of existing channel to suit the surface runoff are needed. this paper presents capacity determination of existing drainage channels subjected to rainfall with 5-year flood discharge plan and consideration of sea tides effect to marengan river which crossed sumenep city. the proposed flood control methods in sumenep city area was also discussed. the catchment of specified rural area was modelled using swmm instrument to compare channel conditions before and after rehabilitation. channel size and height of water level in channel due to rainfall together with the effect of backwater occurred in marengan river caused by the sea tides was observed during the time. from the analysis, it was found that most of existing secondary drainage channels are uncapable to accommodate rainfall with 5-year flood discharge plan. from the available eight secondary drainage channels outlets, the last three outlets were subjected to reverse flows effect in marengan river due to sea tides. in order to reduce the occurance of surface runoff inundation, secondary drainage channel rehabilitation was planned at each outlet, and these proven capable to accommodate rainwater runoff and reverse flow as well. keywords: runoff, drainage channels capacity, swmm, reverse flow 1. introduction some of the land designated as green land has partially transformed into residential land as a result of urban development. a study of infiltration in the residential land have almost never conducted. the existing channel dimensions cannot accommodate surface runoff; therefore, it disrupts the drainage system [7]. the problems in the study area is the occurrence of surface runoff due to changes in land conversion from green land to residential land in recent years, causing some existing drainage channels to be unable to channel the runoff. marengan river, as the main drain in sumenep city, end up at the sea, as sumenep city located at the north of java sea. this caused another problem as marengan river is affected by backwater caused by the sea tides. civil and environmental science journal (civense) vol. i, no. 02, pp. 080-087, 2018 81 the objective of this study was to determine the capacity of existing drainage channels to rainfall with a 5-year return period and determine the flood control that can be carried out in the study area. 2. material and methods the data required in this study are: location map, topographic map, land use map, drainage channel network scheme, existing drainage channel data, rainfall data, population data and geometric data of marengan river as an analysis on final disposal. the study area in sumenep city sub-district is a strategic area because it is the capital of sumenep regency (figure 1). figure 1. study area of kecamatan sumenep there are three rainfall stations around the study location, namely kebonagung, parsanga and pengairan stations. the 10-year daily rainfall data is from 2006 to 2015. the location of the three rain stations is seen in figure 2. figure 2. location of the rain station in the district of sumenep city stages of analysis broadly speaking, the stages of analysis in this study consist of: hydrological analysis, analysis of dirty water discharge, plan discharge analysis based on a 5-year return period using the swmm (strorm civil and environmental science journal (civense) vol. i, no. 02, pp. 080-087, 2018 82 water management model) program, calibrating the model using the root mean square errors (rmse) method and final discharge analysis. in this study the design rain was chosen log pearson iii method [5], with the consideration that this method is more flexible and can be used for all data distribution. log 𝑥 = log 𝑥𝑖 + 𝐺. 𝑆𝑑 (1) where : x = rainfall design with certain return period xi = maximum area rainfall as much as x1, x2, x3, ...., xn g = is a constant obtained from the pearson type iii log table from the relationship between cs and return period (t). sd = standard deviation chi-square test and smirnov-kolmogorov test are used to determine whether the distribution equation chosen can represent the statistical distribution of sample data to be analyzed. equation x2 counts on chi square test with formula [6]: n 2 i=1 oj-ej x = ej  (2) x2 critical values are obtained through the chi-square table. if x2 counts <x2 critical then the analysis of rainfall distribution observations is in accordance with the theoretical model. the smirnov-kolmogorov test was conducted to determine the horizontal deviation scattered in the theoretical and empirical distribution. this horizontal deviation is expressed by δmax <δcr for a certain degree of reality, it can be concluded that the distribution hypothesis can be accepted. δmax equation in the smirnov test kolmogorov [8]: δmax = pe pt (3) δmax = maximum difference between empirical and theoretical opportunities pe = empirical opportunity pt = theoretical opportunity δcr = critical deviation (from table) the selected frequency distribution can be accepted if δmax <δcr and it and rejected if δmax > δcr. duration and frequency intensity analysis (idf) was carried out to estimate peak discharge in small catchment areas [9], using the mononobe formula as follows: i = 2/3 c 24 t 24 24 r       (4) where: i = rain intensity during concentration time (mm/hour) r24 = daily maximum rainfall wastewater discharge is a discharge that comes from household waste, buildings, agencies and so on. the amount is affected by the number of population and the average water needs of the population. as for the average population water requirement is 150 liters/person/day. while the discharge of dirty water civil and environmental science journal (civense) vol. i, no. 02, pp. 080-087, 2018 83 that must be discharged in the channel is 70% of the need for clean water so the amount of wastewater is [4]: 150 x 70% = 105 liters/person/day = 0.00121 liters/sec/person. for a population of (pn), the dirty water that is disposed of every km2 can be calculated as follows: qak = (pn.q)/a (5) which: qak = wastewater discharge (litre/sec/km2) pn = total population (person) q = total wastewater (litre/sec/person) a = area (km2) to calculate the design flood discharge the swmm software was developed by epa (environmental protection agency usa) [10], since 1971. swmm is classified as a dynamic flow rain model that is used for simulation with a continuous time span or momentary flood events. this model is most widely developed to simulate hydrological and hydraulic processes in urban areas. by using swmm, the conditions that occur in the field can be modelled by entering the parameters recorded in the actual conditions. final discharge analysis is carried out to determine the effect of backwater from the river to the channel. by comparing the water level in rivers and channels. if the water level in the river is higher than the water level in the channel, then the calculation of the effect of back water on the channel is carried out. however, if the channel water level is higher than the river water level, it is not necessary to calculate the effect of back water. this analysis uses the direct step method using equations [3]: ∆𝑥 = (𝑦2+ 𝑉2 2 2𝑔 )− (𝑦1+ 𝑉1 2 2𝑔 ) 𝐼𝑜− 𝐼𝑓 (6) in general, the analysis stages of this research consist of: hydrological analysis, dirty water discharge analysis, discharge plan analysis based on 5 year return period using swmm (storm water management model) program, model calibration using root mean square errors (rmse), and final disposal analysis. 3. result and discussion to supplement the missing or damaged data, data from other stations that have complete data and the location of the station closest to the station with missing data. from the calculation results of the maximum rainfall data of 64 mm irrigation rain station in 2007 and total rainfall data of 1,274 mm irrigation station in 2007. to ensure that the available rain data is feasible to be used in subsequent analysis, the existing data is tested statistically. the statistical analysis includes: consistency test, trend absence test, stationary test and persistence test. from the result of consistency test, it can be concluded that the rain data on the three rain gauge stations is consistent which means that in the area of influence of the station there is no environmental change and there is no change in the way of measuring during the recording of the data. in the absence of trend test, rain data on each station is tested by the absence of trend. the periodic series of two data series (rt dab tt) is independent on 5% confidence degree. and dk = 10 2 = 8, then obtained tc value equal to 1.860. from the calculation results obtained thitung for each rain station kebonagung, parsanga, and pengairan for: -0.189; 0.688; and 0.363, then tcal < tc. in addition to the ttest calculations, the absence of trends can also be determined by describing the periodic series in the graph (figure 3 to 5). thus it can be concluded that rainfall data in the period 2006 2015 recorded on the three stations have no tendency toward one direction, the direction of up or down (trend). civil and environmental science journal (civense) vol. i, no. 02, pp. 080-087, 2018 84 in this stationary test the data is divided into two groups, so that the rainfall data at the study site is divided into group i for the period 2006 2010 and ii for the yearly rain period 2011 2015. figure 3. the periodic series of rainfall data of kebonagung station figure 4. the periodic series of rainfall data of parsanga station figure 5. the periodic series of rainfall data of pengairan station test of variant stability obtained f for each rainfall data station kebonagung, parsanga and watering is 1.182; 0.330; and 0.224, while the value of fcritical = 6.39, then fcritical> fcal. so it is concluded that the rain data on the station based on the stability test of variance is stationary or homogeneous. the stability test is average obtained  and t for each rainfall data of kebonagung, parsanga and watering stations were 797.08 and (-0.54); 659.13 and 0.09; 639.72 and (-0.21). while the tcritical value for dk = 8 obtained value 1.860 then tcritical> tcal. so it is concluded that the rain data is stationary. in persistence test, ks and t values are obtained. with dk = 8 then tcritical = 1.86. from result of persistence test analysis where tcritical value > tcal hence can be concluded that available rain data is independent or does not show existence persistence. or it can be said that the data is a random data. the average maximum rainfall for the area is obtained by using data from 2 (two) influential rain gauge stations, namely: kebonagung station and pengairan station. observation period of rainfall data used for 10 (ten) years from 2006 until 2015. the calculation of the average rainfall is done by using arithmetic method. from the calculation obtained the highest rainfall is equal to 131 mm, lowest 57 mm kebonagung rain station r a in fa ll ( m m ) year parsanga rain station r a in fa ll ( m m ) year pengairan rain station r a in fa ll ( m m ) year civil and environmental science journal (civense) vol. i, no. 02, pp. 080-087, 2018 85 and average of 82 mm. from the calculation stage of rainfall design log pearson type iii, obtained rainfall design return period of 5 years of 97.84 mm. by using mononabe equations of heavy rain with short duration can be obtained. count is done with duration up to 300 minutes (5 hours). the 5-year rain depth with a duration of 1-5 hours becomes the rain input parameter in the swmm simulation (table 1). table 1. rainfall design duration return period (minutes) 5 years 60 33,92 120 21,37 180 16,31 240 13,46 300 11,60 based on the sub map of marengan river basin, the existing drainage system is divided into 8 outlet points. the outlet points are sorted by the highest elevation position measured from the upstream of the marengan river. here is the description: 1. outlet 1. this secondary drainage network passes diponegoro road general sudirman ahmad yani 2. outlet 2. this secondary drainage network passes diponegoro road general sudirman ahmad yani 3. outlet 3. this secondary drainage network passes through kh. sajad dr. wahidin. 4. outlet 4. this secondary drainage network passes dr. cipto. 5. outlet 5. this secondary drainage network passes through kh. mansyur raung, then from urip sumoharjo street (pln intersection to the east). 6. outlet 6. this secondary drainage network passes the road wahid hasyim anom sumenep market perum bumi sumekar perum satelit. 7. outlet 7. placed on the street kalimook marengan daya. 8. outlet 8. placed in marengan laok village. as for some input data required by swmm include: input of catchment data (subcatchment) here is the data input used to analyze flood discharge plans for the sumenep city catchment area. a. the boundary of sub-catchment area determination is based on the location of the secondary channel adapted to the flow direction and the boundaries of the marengan sub-watershed. b. the impervious percentage (defined as waterproof area) is determined based on google earth pro image data on imaging date 02 august 2016. c. percentage of land slope is taken based on contour map of marengan river basin. d. depressed heights are part of the pervious and impervious surfaces in which there are puddles, potentially becoming runoff, expressed in mm units. the value of puddle height for impermeable and porous areas varied according to field conditions in the field. the high value of the inundation in the impermeable area can be divided into 2 types, namely: 1.27 mm settlement and 2.54 mm/asphalt road. while for the high value of puddles on porous land can be divided into 3 types, namely: 5.8 mm paddy field, 5.7 mm of stressed field, and yard area of 2.55 mm e. infiltration is a process in which rainwater seeps into the surface of the pervious subcatchment area. swmm provides three options for modelling infiltration, the horton equation, the green ampt method, and the curve number method. this analysis uses the horton equation. f. area of catchment area. for sub-catchment area obtained from digital map using autocad application. g. outlet. it is the name of the node that receives the flow of water in the subcatchment. civil and environmental science journal (civense) vol. i, no. 02, pp. 080-087, 2018 86 h. the width of the catchment area, taken based on the width of the actual catchment area in the field. a conduit is a link that drains water from a node to another node in the drainage system in which case it can be either open or closed channels. the channel cross section can be determined through the table provided. the basic junction elevation is taken based on actual conditions in the field. as for the maximum water depth is taken based on the maximum water level on the channel. to be able to calculate the dirty water discharge data required population of sumenep city. then the population data is projected until 2033. using the equation 5 the discharge of dirty water in the secondary canal can be calculated. the gross water discharge obtained becomes the input inflow parameter in swmm. from the swmm simulation results, total flood discharge design is obtained. the discharge is an accumulation between the discharge of dirty water and the rain water discharge from upstream to downstream channel. to measure the accuracy of the forecast result of a model, a root mean square error (rmse) calibration is performed. from the calculation result of simulation flow and observation flow on channel c19 ' (outlet 3) obtained rmse value of 0.139. the value indicates that the parameter values used in the modeling approach the variation of the observed value. by comparing the discharge design and capacity of the existing channel, some channels are not able to accommodate a 5 year redischarge. for that required drainage channel rehabilitation. the strands on each channel serve as the basis for calculating the new dimension. in accordance with regulation of minister of public works no. 12/prt/m/2014 on implementation of urban drainage system [1, 2], its drainage facilities are at least 10% higher than the capacity of the drainage plan. accordingly, the discharge design obtained is multiplied by 1.1. the drainage network in need of rehabilitation includes 1, 2, 4, 5, 6, and 8 outlets. in outlet 2, besides the dimension change, alternatives of the diversion to the patrian river are also made. this is able to decrease runoff discharge at outlet 2 from initially of 7.15 m3/s to 2.77 m3/s. after conducting capacity analysis and channel rehabilitation, the final waste disposal in marengan river is done. to know the effect of backwater from river to channel by using direct stage method. there are 4 outlets that have effect on backwater, that is outlet 4, outlet 5, outlet 6, and outlet 7, with long influence of backwater respectively, 317.93 m, 677.50 m, 507.41 m, and 1523.41 m. the water level at outlet 4, outlet 5, outlet 6, and outlet 7 is affected by the rain with the 5 year recycle and the effect of backwater from the river. so, in the calculation of the new dimension of the channel, the water level due to rain with the 5-year rework period is added with the water level due to the effect of backwater from the river so that 4 outlets affected by the backflow are able to accommodate the rain with the 5-year return period and the effect of backwater from river. 4. conclusions from the results of calculations on data analysis and discussion in the previous chapter it can be drawn some conclusions, among others as follows: 1. from the calculation results obtained capacity of outlet 1 = 3.53 m3/s; outlet 2 = 2.75 m3/s; outlet 3 = 2.52 m3/s; outlet 4 = 1.21 m3/s; outlet 5 = 4.65 m3/s; outlet 6 = 6.20 m3/s; outlet 7 = 1.47 m3/s; outlet 8 = 0.60 m3/s; outlet 9 = 4.49 m3/s. only secondary drainage networks of outlets 3 and 7 are capable of accommodating rainfall runoff, while secondary drainage outlets 1, 2, 4, 5, 6 and 8 are not able to accommodate rainfall with 5 year return period discharge plan. this causes the puddle point to occur in several streets. outlet 7 is influenced by the reverse flow from the marengan river to the channel causing runoff at the outlet. for that outlet 7 requires channel rehabilitation due to the effect of backwater. 2. to reduce the inundation caused by surface runoff, rehabilitation plan of secondary drainage channel in each outlet is needed. meanwhile, to reduce the burden on the outlet 2 discharge, then use the alternative transfer of discharge to outlet 9 which empties into the river patrean. this civil and environmental science journal (civense) vol. i, no. 02, pp. 080-087, 2018 87 alternative of debit switch is able to decrease runoff discharge at outlet 2 which initially amounted to 7.15 m3/s to 2.75 m3/s. based on comparison between water level of marengan river and channel outlet, at outlets 4, 5, and 6 the influence of backwater from marengan river to channel outlet. while at outlet 7 after the channel rehabilitation, the outlet is no longer influenced by backflow. the planned new channel dimension is not only capable of accommodating rainfall runoff with a 5 year return period, but also able to accommodate debit runoff due to the effect of backwater from the marengan river. references [1] anonim 2014. tata cara penyusunan rencana induk sistem drainase perkotaan (no. 12/prt/m/2014) jakarta : kementerian pekerjaan umum [2] badan standardisasi nasional. 1994. sni 03-3424-1994 tata cara perencanaan drainase permukaan jalan. jakarta: bsn. [3] chow, v. t. 1997. hidrolika saluran terbuka (open channel hydraulics), jakarta: erlangga. [4] soehardjono. 1984. drainasi. malang: fakultas teknik universitas brawijaya. [5] soemarto, cd. 1995. hidrologi teknik. jakarta: erlangga. [6] soewarno. 2002. hidrologi, aplikasi metode statistik untuk analisa data, jilid i. bandung: nova. [7] solikin solikin, ery suhartanto, riyanto haribowo., 2017. analisis penanganan genangan pada wilayah kota banjarmasin. jurnal teknik pengairan 8 (1), 15-25, 2017. [8] sri harto, 1993. analisis hidrologi. jakarta: gramedia. [9] triatmodjo, b. 2006. hidrologi terapan. yogyakarta: beta offset yogyakarta. [10] united states environmental protection agency. 2010. storm water management model 5.0 user’s manual. https://www.epa.gov/water-research. diakses tanggal 03 agustus 2016. civil and environmental science journal vol. 4, no. 2, pp. 154-162, 2021 154 correlation between mobility and covid-19 cases in surabaya city, indonesia gholiqul amrodh alawy 1 , achmad wicaksono 1 , agus suharyanto 1 1 department of civil engineering, faculty of engineering, universitas brawijaya, malang, 65145, indonesia gholiqulaa@gmail.com 1 received 25-05-2021; accepted 29-06-2021 abstract. the number of covid-19 cases in surabaya was one of the highest in indonesia at the beginning of the pandemic. this study aims to determine the mobility and activity patterns of the people of surabaya during the covid-19 pandemic and find a correlation between people mobility and the number of covid-19 cases in surabaya city using pearson’s coefficient of correlation (pcc). the data used are mobility data at gubeng station, purabaya terminal, waru utama toll gate, and covid-19 community mobility reports. the mobility pattern of the people of surabaya city in 2020 is divided into 5 phases, namely the normal condition phase (f0), the pandemic’s initial phase (f1), the psbb phase (f2), the transition of akb phase (f3), and the akb phase (f4). this study indicates that the number of people in transit stations and residential areas has a high correlation with the number of covid-19 cases. in addition, the type of mobility that has the most effect on increasing the number of covid-19 cases is the mobility of bus transportation. keywords: activity, correlation, covid-19, mobility, transportation. 1. introduction the covid-19 pandemic began in early 2020 and entered indonesia on march 2, 2020, in depok [1]. the number of positive cases of covid-19 in indonesia continues to increase until january 26, 2021, and covid-19 confirmed patients in indonesia reached 1,000,000 more people [2]. the number of positive cases in surabaya, one of the major cities in indonesia, had a very high increase at the beginning of the pandemic. on 20 – 25 may 2020, the number of people confirmed positive for covid-19 almost doubled from 1,255 people to 2,095 people [2]. it is estimated that the high people mobility is due to the homecoming flow ahead of eid al-fitr 1441 h. the government of indonesia has tried to prevent the transmission of this virus by issuing various policies of social and transportation restrictions. human mobility is one of the main factors in spreading the virus from the affected areas [3]. at the beginning of the spread of covid-19 in wuhan city, the 1 cite this as: alawy, g.a., wicaksono, a. & suharyanto, a. (2021). correlation between mobility and covid19 cases in surabaya city, indonesia. civil and environmental science journal (civense), 4(2), 154-162. doi: https://doi.org/10.21776/ub.civense.2021.00402.5 civil and environmental science journal vol. 4, no. 2, pp. 154-162, 2021 155 number of new cases outside wuhan city substantially correlated to the volume of human mobility from wuhan to other cities [4]. the pandemic has an impact on the economy and the welfare of people in indonesia. it takes research that provides a view for transport policy makers, planners, and researchers to map the situation to restore its state [5]. this study aims to determine the relationship between covid-19 cases and the mobility of people and vehicles in surabaya. in addition, this study also examines government policies that impact the travel patterns of the people of surabaya during a pandemic. the results of this study are expected to help the central and local governments in taking policy related to transportation during the pandemic. 2. material and methods the research area is surabaya city, the center of movement and activity, and the coronavirus was first spread in east java province. the data used is secondary daily data from the beginning of covid19 cases in surabaya until the end of 2020, march 17 – december 31, 2020. the number of positive covid-19 data in surabaya and mobility data will be juxtaposed with government policies related to transportation, public transport, and social restrictions. furthermore, it can be known that the pattern of people’s mobility in 2020 can be divided into several stages/ phases. in each phase, the correlation between the number of covid-19 cases and mobility in surabaya will be calculated. this analysis aims to determine the extent of the relationship between each variable and look for the type of mobility that has the most impact on the increase in covid-19 cases in surabaya. 2.1. dataset the data used in this study is secondary data obtained from several agencies/ institutions, as shown in table 1. the data collected are the number of covid-19 positive cases, transportation policies during the pandemic, number of passengers on public transportation, volume of vehicles on toll roads, and community activities. table 1. mobility data of surabaya people used in research and institutions that provide such data. no. data institutions 1 covid-19 cases in surabaya city ministry of health republic of indonesia (https://infocovid19jatimprov.go.id/) 2 passengers and vehicles in purabaya bus station surabaya transportation department (dishub) 3 passengers in gubeng train station pt. kereta api indonesia daop viii surabaya 4 vehicles in waru utama toll gate pt. jasa marga surabaya gempol 5 community mobility reports in east java google community mobility reports (https://www.google.com/covid19/mobility/) 2.1.1. covid-19 cases. the first confirmed positive cases of covid-19 in surabaya and east java provinces were announced on march 17, 2020. the number of positive cases of covid-19 data obtained from the ministry of health of the republic of indonesia through the government of east java province. the data for covid-19 used is the number of confirmed positive cases of covid-19, while data for patients recovered, patients died, and others were not used in this study. 2.1.2. mobility in terminal and station. vehicle and passenger data in this study have been taken from gubeng station and purabaya terminal. both locations were chosen because they are the busiest land civil and environmental science journal vol. 4, no. 2, pp. 154-162, 2021 156 transportation nodes in the greater surabaya area. the train mobility data used is the data of passengers who boarded at gubeng station. while mobility data on buses used in this study are:  number of passengers and vehicles coming to purabaya terminal  number of passengers and vehicles departing from purabaya terminal 2.1.3. mobility in highway. mobility data on the road taken is the number of vehicles entering the surabaya through the waru utama toll gate. this toll gate was chosen because it is the main toll gat e to enter the surabaya area and has the highest traffic volume compared to other toll gates. 2.1.4. the activity of the community. data on people’s movement in east java province is obtained from mobility reports issued by google based on tracking of mobile phone users in a region. the covid-19 community mobility report aims to provide insights into mobility changes in response to government policies to reduce the impact of covid-19 [6]. this reporting is in the form of a percentage (%) of people in a certain activity category with a baseline that is the median size from january 3 to february 6, 2020. activity trends recorded in an area are divided into six categories of places: retail & recreation, grocery & pharmacy, parks, transit stations, workplaces, and residential. 2.2. method the correlation analysis used in this study used pearson’s coefficient of correlation (pcc) according to the equation (1) as follows: 𝑟𝑥𝑦 = 𝑛 ∑ 𝑥𝑖−∑ 𝑥𝑖 ∑ 𝑦𝑖 √𝑛 ∑ 𝑥𝑖 2 − (∑ 𝑥𝑖) 2 √𝑛 ∑ 𝑦𝑖 2 − (∑ 𝑦𝑖) 2 (1) where 𝑥𝑖 is called the independent variable, 𝑦𝑖 is the dependent variable, and n is the total sample. pearson correlations in this study are appropriate because the datasets used have interval or ratio scales. the variables to be searched for correlation are shown in table 2. table 2. research variables and their code. variables are divided into the variable number of positive covid-19 (y) and mobility variables of people/vehicles (xi). research variable code positive cases of covid-19 in surabaya y1 mobility in purabaya bus station vehicle coming x11 passenger coming x12 vehicle departing x13 passenger departing x14 mobility in gubeng train station passenger departing x21 mobility in waru utama toll gate vehicle passing x31 google community mobility report retail & recreation x41 grocery & pharmacy x42 parks x43 transit stations x44 workplaces x45 residential x46 civil and environmental science journal vol. 4, no. 2, pp. 154-162, 2021 157 the results of the correlation analysis show the close relationship between the variable number of covid-19 cases (y) and the mobility variables (xi). correlations between variables are rated from the range of -1 to 1, with 0 is no correlation, while -1 and 1 are perfect correlation. a correlation value of -1 is a perfect correlation with the opposite direction, while 1 is a perfect correlation in the same order. there is no exact condition of whether a particular correlation number indicates a high or weak correlation rate. a correlation number above 0.5 shows a high correlation, while below 0.5 a weak correlation [7]. 3. result and discussion 3.1. mobility and activity patterns changes in the mobility and activity of surabaya’s people in 2020 are due to the presence of covid19 and the government’s social restriction policies to prevent transmission of the virus. these changes can be divided into several phases that show the trends and characteristics of the community’s mobility. the mobility and activity of surabaya people in 2020 can be divided into 5 phases, normal condition phase (f0), pandemic’s initial phase (f1), large-scale social restriction phase (f2), transition of new habit adaptation phase (f3), and new habit adaptation phase (f4). each phase of community mobility in surabaya occurs at different times and is shown in table 3. table 3. mobility and activity pattern phases of surabaya people in 2020. steps are divided into five based on differences in mobility and activity patterns. no phase time 1 normal condition phase (f0) 1 january – 16 march 2020 2 pandemic’s initial phase (f1) 17 march – 21 april 2020 3 large-scale social restriction phase (f2) 22 april – 5 june 2020 4 transition of new habit adaptation phase (f3) 9 june – 8 july 2020 5 new habit adaptation phase (f4) 9 july – 31 december 2020 figure 1. fluctuations in people and vehicle’s mobility every day in 2020. the difference in mobility patterns in each phase is seen in the graph, especially in the pre-pandemic phase with the post-pandemic phase. 0 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000 passengers departing from purabaya bus station passengers departing from gubeng train station vehicles passing through waru utama toll gate f0 f1 f2 f3 f4 civil and environmental science journal vol. 4, no. 2, pp. 154-162, 2021 158 mobility and activities of surabaya people in 2020 are still normal at the beginning of the year, decreased due to covid-19, and slowly increased until the end of the year. fluctuations in people’s mobility every day in 2020 are shown in the graph in figure 1. in the chart, the mobility of people represented by vehicles passing through the waru utama toll gate, passengers departing from purabaya bus station, and passengers departing from gubeng train station. the percentage of mobility of people/vehicles in the post-pandemic phase (f1, f2, f3, f4) compared to the regular stage of prepandemic conditions (f0) is shown in figure 2. figure 2. the percentage of mobility in the post-pandemic phase (f1, f2, f3, f4) compared to the normal phase of pre-pandemic conditions (f0). figure 3. fluctuations in people and vehicle’s mobility every day in 2020. the difference in mobility patterns in each phase is seen in the graph, especially in the pre-pandemic phase with the postpandemic phase. 100.00% 100.00% 100.00% 28.15% 23.94% 70.08% 0.48% 6.22% 55.92% 11.80% 11.85% 81.96% 26.62% 28.59% 91.18% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% bus train highway normal condition phase (f0) pandemic’s initial phase (f1) psbb phase (f2) transition of akb phase (f3) akb phase (f4) -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 retail & recreation grocery & pharmacy parks transit stations workplaces residential f0 f1 f2 f3 f4 civil and environmental science journal vol. 4, no. 2, pp. 154-162, 2021 159 the pattern of community activity in some public places such as retail, recreation, grocery, pharmacy, parks, transit stations, and workplaces has fluctuations similar to mobility. unlike general public sites, the percentage of people who are in residential has the opposite pattern. changes in the rate of active people in several categories of places reported by the community mobility report in east java every day in 2020 are shown in the graph in figure 3. the percentage of people’s activity in the postpandemic phase (f1, f2, f3, f4) compared to the regular stage of pre-pandemic conditions (f0) is shown in figure 4. figure 4. the percentage of mobility in the post-pandemic phase (f1, f2, f3, f4) compared to the normal stage of pre-pandemic conditions (f0). 3.1.1. normal condition phase (f0). this phase starts from january 1, 2020, to march 16, 2020. in this phase, community activities are still normal. however, in early march, mobility decreased due to the emergence of the first case of covid-19 in indonesia. however, the decline is not significant and can still be categorized under normal conditions. 3.1.2. the pandemic’s initial phase (f1). on march 17, 2020, the first case was announced in surabaya so that people prefer not to leave the house and do activities at home. this situation causes people’s mobility to continue to decline; this phase is called the pandemic’s initial phase (f1). compared to f0, on f1 public transport using buses and trains disembarked to the remaining 28,15% and 23,94% [8] [9] respectively. vehicles crossing the motorway are also reduced to 70,08% [10] when compared to f0. 3.1.3. large-scale social restriction phase (f2). due to the increasing number of covid-19 cases, the local government finally issued a large-scale social restrictions (psbb) policy for surabaya and surrounding areas which continues to be extended until june 5, so this phase is called the large-scale social restriction (psbb) phase (f2). this policy makes people’s mobility decrease drastically to the lowest number in 2020. some public facilities and public services are closed. one of them is the purabaya bus transportation terminal temporarily suspended from april 28 to june 8, 2020. in addition, the railway station is still operating, but train passengers are very few with only 5% left compared to normal f0 conditions. -1.03 1.69 -7.16 -1.91 3.31 1.03 -28.98 -12.02 -35.50 -55.58 -30.44 16.63 -11.97 0.40 -9.30 -29.78 -18.94 9.65 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 retail & recreation grocery & pharmacy parks transit stations workplaces residential normal condition phase (f0) pandemic’s initial phase (f1) psbb phase (f2) transition of akb phase (f3) akb phase (f4) civil and environmental science journal vol. 4, no. 2, pp. 154-162, 2021 160 3.1.4. the transition of new habit adaptation phase (f3). through se gugus tugas no. 7 2020 on june 6, 2020, the government finally loosened social restrictions and began initiating new habit adaptation (akb). on june 9, 2020, all public transportation in surabaya was re-operated but still not entirely stable. this phase transitions between the condition of total social restriction in the psbb phase and the state of the loosening of social restrictions in the akb phase, so it is called the transition of the akb phase (f3). 3.1.5. new habit adaptation phase (f4). people’s mobility has started to stabilize after one month of akb policy issued, although it is still not as big in normal conditions before the pandemic. july 9, 2020, until the end of 2020, is called the akb phase (f4). although it has started to stabilize, the mobility of people in f4 is still deficient compared to the normal condition phase (f0). compared to normal conditions, bus and rail transport mobility is only 27% and 29% [3] [4]. mobility of vehicles on the highway has started to approach normal conditions before the pandemic, which is 91% compared to normal conditions [5]. 3.2. correlation between mobility and covid-19 cases in this study, correlation values between the variable number of covid-19 cases with mobility variable are using pearson’s coefficient of correlation (pcc) method. this analysis aims to find out the extent of the impact of covid-19 on the mobility of people in surabaya and vice versa. the analysis of research variable correlation is divided into two parts; the first is the correlation between the number of covid-19 cases with passenger/vehicle mobility, and the second is the correlation between the number of covid-19 cases and community activities from community mobility reports (cmr). the correlation between covid-19 cases and the passenger/vehicle mobility in each phase is shown in table 4. mobility in bus transportation (x11, x12, x13, x14) and on rail transport (x21) relatively has a high correlation with the number of covid-19 cases in surabaya in the f1, f3, and f4 phases. in f2, the correlation value tends to be small due to lockdown conditions so that people’s mobility does not have much effect on the addition of covid-19 cases in surabaya. table 4. correlation of the number of covid-19 cases with the mobility of people/vehicles in each phase. in f0, there is no correlation because there are no cases of covid-19 in surabaya. variable f0 f1 f2 f3 f4 y1 1 1 1 1 x11 -0.738 -0.409 0.847 0.580 x12 -0.661 -0.408 0.807 0.622 x13 -0.717 -0.409 0.929 0.701 x14 -0.646 -0.410 0.835 0.688 x21 -0.600 0.042 0.802 0.753 x31 -0.306 0.310 0.632 0.568 on the pandemic’s initial phase (f1) and the psbb phase (f2), the negative correlation values indicate that the relationship between the number of cases and mobility is reversed. this value shows that in the initial phases of the pandemic, the number of covid-19 cases continues to increase per day. the number of mobility decreases because people are infected by the virus and the government’s advice to work and school from home. in f1, the correlation value is relatively high, which means an increase in the number of covid-19 cases with a decrease in people’s mobility is closely related. on f3 and f4, the correlation value obtained relatively high with a positive coefficient indicates that the number of cases with mobility has a close and direct relationship. this value shows that the increasing number of people’s mobility in the new habit adaptation phase has a high relationship with civil and environmental science journal vol. 4, no. 2, pp. 154-162, 2021 161 the increase in the number of covid-19 cases in surabaya. in f3, the correlation value is higher than f4, which indicates that although mobility and community activity has increased towards normal in f4, the increase in the number of cases is not very significant and can already be controlled. furthermore, the correlation between covid-19 cases and community activities in the city in each phase is shown in table 5. table 5. correlation of the number of covid-19 cases with community activities in the city for each phase. in f0, there is no correlation because there are no cases of covid-19 in surabaya. variable f0 f1 f2 f3 f4 y1 1 1 1 1 x41 -0.269 0.480 0.457 -0.048 x42 -0.447 0.401 0.447 0.440 x43 -0.232 0.369 0.382 0.281 x44 -0.544 0.262 0.615 0.688 x45 -0.057 -0.102 -0.034 -0.090 x46 0.377 -0.292 -0.302 -0.573 in the pandemic’s initial phase (f1), variables retail & recreation (x41), grocery & pharmacy (x42), parks (x43), transit stations (x44), and workplaces (x45) were negatively correlated with the number of covid-19 cases. similar to the correlation with mobility, when covid-19 cases increase per day, the number of activities decreases. while the residential variable (x45) has a positive value, people are increasingly staying at home when the number of covid-19 cases rises. in the phase of f2, f3, and f4, variables x41, x42, x43, dan x45 correlate with the number of covid19 cases that are relatively low and positive value. this low value shows that the number of people active in the city does not affect the number of covid-19 cases. in the psbb and akb phases, the implementation of covid-19 health protocols has been implemented and adhered to in surabaya. in the akb phase (f4), the correlation value between transit stations (x44) and the number of highvalue and positive-value cases was 0.688. while the correlation between residential (x46) and the number of cases is high but negative, which is -0.573. this value shows that during akb, the number of covid-19 cases in surabaya is influenced by the number of people who are active / gathered at transit stations, as well as the lack of people who are active in residential 4. conclusions mobility and activities patterns of surabaya people in 2020 are influenced by the spread of covid19 and government policies to reduce its spread. mobility and activity patterns can be divided into 5 phases of conditions, namely normal condition phase (f0), pandemic’s initial phase (f1), large-scale social restriction phase (f2), the transition of new habit adaptation phase (f3), and new habit adaptation phase (f4). the number of positive cases of covid-19 has a high correlation to the mobility of people and vehicles in surabaya. the type of mobility that most affects the increase in covid-19 cases is mobility in bus transport modes with varying correlation values in each phase. meanwhile, the correlation between the number of positive cases of covid-19 and the activities of people obtained from community mobility reports has a relatively low correlation. however, in the f4, the number of activities in transit stations and residential areas is highly correlated to covid-19 cases. references [1] r. djalante et al., “review and analysis of current responses to covid-19 in indonesia: period of january to march 2020,” prog. disaster sci., vol. 6, p. 100091, 2020, doi: civil and environmental science journal vol. 4, no. 2, pp. 154-162, 2021 162 10.1016/j.pdisas.2020.100091. [2] gugus tugas percepatan penanganan covid-19, “laporan kasus harian satgas penanganan covid-19,” 2021. [online]. available: https://covid19.go.id/peta-sebaran. [3] s. m. iacus, c. santamaria, f. sermi, s. spyratos, d. tarchi, and m. vespe, “human mobility and covid-19 initial dynamics,” nonlinear dyn., vol. 101, no. 3, pp. 1901–1919, 2020, doi: 10.1007/s11071-020-05854-6. [4] m. u. g. kraemer et al., “the effect of human mobility and control measures on the covid-19 epidemic in china,” science (80-. )., vol. 368, no. 6490, pp. 493–497, 2020, doi: 10.1126/science.abb4218. [5] a. tirachini and o. cats, “covid-19 and public transportation: current assessment, prospects, and research needs,” j. public transp., vol. 22, no. 1, pp. 1–34, 2020, doi: 10.5038/23750901.22.1.1. [6] google, “google covid-19 community mobility reports,” 2021. https://www.google.com/covid19/mobility/. [7] s. santoso, menguasai statistik dengan spss 25. jakarta: pt. elex media komputindo, 2018. [8] dinas perhubungan kota surabaya, “data arus bus dan penumpang akap akdp unit terminal purabaya tahun 2020,” 2020. [9] pt. kereta api indonesia daop viii surabaya, “volume penumpang surabaya gubeng tahun 2020,” 2020. [10] pt. jasa marga cabang surabaya gempol, “data lalu lintas tol surabaya gempol tahun 2020,” 2020. civil and environmental science journal vol. ii, no. 02, pp. 117-127, 2019 117 inspections of hydro-geotechnical on ngancar dam runi asmaranto1, antonius suryono2, muhammad nurjati hidayat1 1 water resources engineering department, universitas brawijaya, malang, 65145, indonesia 2 bengawan solo river basin development agency, indonesia runi_asmaranto@ub.ac.id received 16-08-2019; revised 08-09-2019; accepted 20-09-2019 abstract. besides having great benefits, dam also holds enormous potential dangers. the collapsed dam will cause devastating flood along the river resulting in loss of lives, properties, damage to public facilities and environment, especially in the downstream area. for safety and prevent the occurrence of the disaster, the operational of dam should always be monitored, inspected and maintained properly continually. with a good monitoring, dam managers will discover as early as possible the problems emerging in the dam, and then perform the appropriate steps to prevent the development of the problems. this paper will perform hydro-geotechnical analysis as a review current condition of slope stability based on the result of soil investigation on present dam condition and review instrumentations installed in ngancar dam. keywords: dam inspection, hydro-geotechnical, slope stability, seepage 1. introduction ngancar dam was built in 1944 by the dutch government [1] and the function of this dam is to the needs of irrigation water in the district of wonogiri in general and the district batuwarno particular. until now ngancar dam is still able to function properly, although it declined in addressing the needs of irrigation water. ngancar dam is geographically located at 7°48’5” s and 110°53’53” e. dams condition is still functioning properly and technically adequate; dam today is still able to serve the needs of irrigation area measuring 1,300 ha [1]. in order to improve the operation and safety of dams in indonesia, the government has set a new policy, which was originally purely technical dam by giving attention to both prevention and control activities around the dam and upstream watershed-based community participation. in this study will be performed hydro-geotechnical analysis is a review of the condition of slope stability based on the results of soil investigation dam body existing conditions now, and review of instrumentation installed namely: piezometer, deformation, and seepage [2]. 2. material and methods inspection study of ngancar dam was conducted based on the latest data related to: a. measurement of topography and bathymetry data in 2016 using global bench mark (ttg-1161). b. soil data used for slope stability analysis based on drilling results in 2016 at ngancar dam civil and environmental science journal vol. ii, no. 02, pp. 117-127, 2019 118 c. visual observations of dam instrumentation conditions such as: piezometer, deformation and seepage are based on observation data of 2016. d. seepage analysis on the dam body and v-notch gauge is based on current geotechnical conditions and field observations of 2016. e. to perform the analysis is done based on the guidelines inspection/evaluation dam and the guidelines for common criteria dam design [3]. 2.1. procedure of observe piezometer make observations by using the dip meter tool. before making observations using the dip meter tool, it is necessary to check the tool by dipping the probe into the water to make sure the indicator lights are on and the tone of the sound is working [4]. the following observation steps: • lower the dip meter probe into the well to ensure the sound/sound tone and indicator light are on when the probe hits the water level. • pull the probe up slowly until the light turns off and the tone is inaudible. • moving the probe up and down slowly so as to get into the probe well with the tape measure with the measuring tape against the reference point / face well. • the reading was done several times and the average score was taken. the amount of pore pressure can be calculated by the following formula: pp = rpe – r – pte (1) pl = rpe – r (2) pp = pore pressure (mh2o) pl = piezometric level (m) rpe = reference piezometer elevation (m) r = reading (m) pte = piezometer tip elevation (m) 2.2. slope stability and seepage analysis to determine the condition of the stability of the dam slope, used the modified bishop method and janbu. the amount of seepage that comes out from the body of ngancar dam is calculated by seep / w model based on finite element. the calculation result is a flux that is the discharge (q) seepage passing through the core. the seep analysis analyzed using the seep / w 2007 program is in the maximum reservoir water level (fwl +243.98), normal water level (nwl + 243.20), and minimum water level (lwl +235). 2.3. total flow quantity this value can be computed from the nodal heads and the coefficients of the finite element equation. for example, consider a mesh with only one element, as illustrated in figure 1. the objective is to compute the total flow across a vertical section of the element. it can be re-written with the flux value isolated on one side as follows [5]: [𝐾]{𝐻} + [𝑀] ∆𝐻 ∆𝑡 = {𝑄} (3) in a steady-state analysis, the storage term [𝑀] ∆𝐻 ∆𝑡 becomes zero, and the equation can be reduced to: [𝐾]{𝐻} = {𝑄} civil and environmental science journal vol. ii, no. 02, pp. 117-127, 2019 119 figure 1. illustration of a flux section across a single element the global set of finite equations for one element is as follows: [ 𝐶11 𝐶12 𝐶13 𝐶14 𝐶21 𝐶22 𝐶23 𝐶24 𝐶31 𝐶32 𝐶33 𝐶34 𝐶41 𝐶42 𝐶43 𝐶44 ] [ 𝐻1 𝐻2 𝐻3 𝐻4 ] = [ 𝑄1 𝑄2 𝑄3 𝑄4 ] (4) from darcy’s law, the total flow between two points is [6] [7] 𝑄 = 𝑘. 𝐴 ∆𝐻 𝑙 (5) the coefficients, c, in equation (4) are a representation of 𝐾𝐴 𝑙 equation (5) therefore, the flow from node i to node j is: 𝑄𝑖𝑗 = 𝑐𝑖𝑗(𝐻𝑖 − 𝐻𝑗) in a transient analysis, because of material storage, the calculation of the total flow quantity must include the storage effect. the change in flow quantity due to the storage term can be expressed as: 1 𝑡 [ 𝑚11 𝑚12 𝑚13 𝑚14 𝑚21 𝑚22 𝑚23 𝑚24 𝑚31 𝑚32 𝑚33 𝑚34 𝑚41 𝑚42 𝑚43 𝑚44 ] [  𝐻1  𝐻2  𝐻3  𝐻4 ] = [ 𝑄1 𝑄2 𝑄3 𝑄4 ] (6) where h1,2,3,4 etc. are the changes of total head at the various nodes between the start and the end of a time step. in general, the average change of total head from node i to node j can be expressed as: ∆𝐻𝑖𝑗 = ∆𝐻𝑖+∆𝐻𝑗 2 (7) therefore, the change in flow quantity from node i to node j due to a change in storage is: 𝑄𝑖𝑗 = 𝑚𝑖𝑗 ∆𝐻𝑖𝑗 𝑡 (8) the total flow quantity from node i to node j for a transient analysis then becomes: 𝑄𝑖𝑗 = 𝐶𝑖𝑗(𝐻𝑖 − 𝐻𝑗) + 𝑚𝑖𝑗 ∆𝐻𝑖𝑗 𝑡 (9) the total flow quantity through the flux section shown in figure 1 is: 𝑄 = 𝑄21 + 𝑄24 + 𝑄31+ 𝑄34 (10) civil and environmental science journal vol. ii, no. 02, pp. 117-127, 2019 120 3. result and discussion prior to the analysis of related visual inspection, conducted a study of previous studies related to the condition of the ngancar dam. construction of this dam is built in the dutch colonial era; which is not found as built drawing, but based on previous studies obtained information that this dam is a rock-earth fill dam type with impervious core layer. the results of the study of the topography of the location and position of the dam instruments are as follows: 3.1. piezometers there are 14 pieces of piezometers, which are all types of standpipe. all of the 14 pieces are included 1-piece piezometer piezometers damaged by thick sediment covered ± 10 m in hole piezometers. coordinates of each piezometer based on the 2016 topographical measurements using global bench mark are as follows (see table 1). figure 2. inspection of stand pipe piezometer at ngancar dam table 1. location of stand pipe piezometer (spp) based on year 2016 no name coordinat spp elevation z(m) x (m) y (m) 1 pz 497685,7 9116856,334 + 245,348 2 pz.1 497614,4 9116721,507 + 244,900 3 pz.2 497646,6 9116739,878 + 244,347 4 pz.2b 497640,3 9116750,360 + 240,286 5 pz.4 497642,2 9116773,341 + 232,392 6 pz.6 497680,3 9116767,281 + 244,763 7 pz.6b 497681,9 9116770,099 + 244,780 8 pz.7 497677,8 9116769,903 + 243,167 9 pz.7b 497674,8 9116774,911 + 240,254 10 pz.9 497689,1 9116802,085 + 244,745 11 pz.10 497682,6 9116801,926 + 243,689 12 pz.12 497631,2 9116765,312 + 232,250 13 pz.18 497662 9116749,530 + 244,587 14 pz.19 497660,2 9116752,250 + 244,663 civil and environmental science journal vol. ii, no. 02, pp. 117-127, 2019 121 figure 3. annual rainfall in at ngancar dam figure 4. change the water in the piezometer against the reservoir water level from the monitoring results throughout 2015, shows that only five pieces standpipe piezometers to describe the condition of seepage in the dam body is piezometers number: 2b pz, pz 4, 9 pz, pz 10, pz 18. while other standpipe piezometers are: pz 1 pz 2 pz 6, pz 6b, pz 7, pz 7b, pz 12, pz 19 was not found water to a depth end of the piezometer, this may be due to the placement of the piezometers is less precise, so the conditions in piezometers always dry on every reservoir water level condition. the relationship of water level in the piezometers are also affected by the reservoir water level fluctuations, as seen in the following graph: 215 219 223 227 231 235 239 243 247 i ii i ii i ii i ii i ii i ii i ii i ii i ii i ii i ii i ii jan feb mart apr mei jun jul agus sep okt nop des e le va ti o n ( m ) water depth in piezometer (m) monitoring water depth in piezometer ( 2015) reservoir water level pz.2b pz.4 pz.9 pz.10 pz.18 0 50 100 150 200 250 300 350 400 450 500 i ii i ii i ii i ii i ii i ii i ii i ii i ii i ii i ii i ii jan feb march apr may june july aug sep octo nov dec r a in fa ll ( m m ) 2015 civil and environmental science journal vol. ii, no. 02, pp. 117-127, 2019 122 figure 5. regression value of piezometers to the water level in reservoir from the graph above shows that all four piezometers are: pz-2b; pz-4; pz-9; and pz-10 has a good regression coefficient with r2 > 0.5 [8]. it means that the existence of piezometers is strongly influenced by the reservoir water level fluctuations, but in piezometers pz-18 otherwise obtained relationship r2 < 0.5. this could indicate that the water level readings at the point pz -18 piezometers conditions need to be evaluated. as we know that the function is to monitor the movement piezometer phreatic flow in the body of the dam, but if the condition piezometers damage will greatly affect the results of monitoring the dam so it must be repaired in order to precisely predict the leak in the dam body both in static and dynamic load conditions 3.2. deformation instrument. at the ngancar dam, there are four (4) pieces of benchmarks to monitor deformation in which everything is in good condition. however, not is all measured periodically to determine the movement of the dam decline. in 2016 has performed repeated measurements coordinate deformation-bench mark with readings as follows: civil and environmental science journal vol. ii, no. 02, pp. 117-127, 2019 123 table 2. the newest coordinate of deformation bench mark (2016) no name bench mark coordinat utm elevation (m) x (m) y (m) 1 bm pg-1 497.611,408 9.116.720,963 244,436 2 bm pg-2 497.633,638 9.116.735,356 244,371 3 bm pg-3 497.685,564 9.116.808,763 244,622 4 bm pg-4 497.684,754 9.116.841,826 244,623 expected to this latest coordinate of benchmark used as a starting point for monitoring the movement of the dam body deformation. 3.3. seepage gauge v-notch weir is used to monitor the flow of seepage of the dam body. in ngancar dam, there are 2 pieces of v-notch weir, but not all the instruments can describe the condition of discharge of seepage in the dam body. this is because of both the instruments cannot drain the water seepage above a threshold. seepage water tends to flow through a pipe below the threshold so that the seepage capacity cannot be measured properly. things can be done is to re-position setting v-notch weir in order to function properly. . figure. 6. v-notch weir cannot measure the seepage discharge (both on the left and right of the dam). 3.4. analysis of seepage. the amount of seepage that flows from the body of ngancar dam is calculated with finite element. the result of the calculation is flux, which is the discharge (q) seep through the ngancar dam core. water reservoir boundary conditions at flood water level (fwl) +243.98, normal water level (nwl) + 243.20, and low water level (lwl) + 235. figure 7. seepage in dam body at flood water level fwl (+243.98) (a) left (b) right civil and environmental science journal vol. ii, no. 02, pp. 117-127, 2019 124 figure 8. seepage in dam body at normal water level, nwl (+ 243.2) figure 9. seepage in dam body at low water level, lwl (+235) from seepage capacity analysis using seep / w model obtained seepage capacity for each water level of reservoir, are as follows: fwl +243.98 m = 6.1236.10-3 m³/s. nwl +243.20 m = 5.517.10-3 m³/s. lwl +235 m = 2,7203.10-3 m³/s. average = 4.786.10-3 m³/s. referring to the japanese institute of irrigation and drainage, the amount of leakage passing the foundation and body of the dam should not exceed 1% of the average river flow into the reservoir [9]. is known: average discharge (q) in the river = 0.1785 m³/s 1% of average discharge (q) river = 1.785.10-3 m³/s. average seepage capacity = 1,572.10-3 m³/s. average seepage capacity (4.786, 10-3 m³/s) > 1% of the average q river (1.785.10-3 m³/s). thus it can be concluded that the seepage beneath the foundation and body of the ngancar dam is not safe and needs to be repaired immediately. this is thought to be due to weathering of limestone rocks at the foundation base 3.3. analysis of slope stability slope stability analysis is reviewed based on static and dynamic load conditions. analysis to determine the magnitude of earthquake design following the guidelines of pd-t14-2004 a [10]. analysis of the stability of the rock-earth fill dam is calculated by considering the risk factor dam safety [11] [12]. civil and environmental science journal vol. ii, no. 02, pp. 117-127, 2019 125 table. 3 calculation of risk factor on ngancar dam risk factor of ngancar dam weight of risk factor (fr) storage capacity = 4.19x106 m3 frk = 4 height of dam = 19,05 m frt = 2 evacuation need ± 1000 people fre = 8 the extent of damage in the downstream = moderate frh = 4 total of risk factor frtotal = 18 with a total risk factor (frtotal) = 18, then based on risk class table, and then ngancar dam including risk class ii (moderate). tabel 4 . dam risk class [5] total risk factor risk class (0-6) i (low) (7-18) ii (moderate) (19-30) iii (high) (> 31) iv (extreme) based on the risk class of the dam and waterworks, the criteria for the design earthquake loads in obe (optimum based earthquake) and mde (maximum design earthquake) can be determined by guidelines of pd-t14-2004. then to the ngancar dam with risk class ii (moderate), the analysis methods used in the period, t = 100 years (for "requirement without damage" obe) and the period t = 3,000 years ("requirements allowed no damage without collapse" mde). figure 10. map of peak acceleration at bedrock (return period of 100 and 3000 years) based on the location of the dam above the peak acceleration value in bedrock (sb) = 0.15 g and the amplification factor (fpga) = 1.00. peak acceleration at ground level for the return period of 100 years; pgam = fpga x sb = 1,00 x 0,15 g = 0,15 g ngancar acceleration map in base rock (sb) for 3000-year earthquake return period acceleration map in base rock (sb) for 100-year earthquake return period civil and environmental science journal vol. ii, no. 02, pp. 117-127, 2019 126 k0 = pgam / g = 0,15 x 0,981 / 0,981 = 0,15 kh = k0 x α = 0,15 x 0,50 = 0,075 peak acceleration at ground level for the return period of 3000 years mde; pgam = fpga x sb = 1,00 x 0,45 g = 0,45 g k0 = pgam / g = 0,45 x 0,981 / 0,981 = 0,45 kh = k0 x α = 0,45 x 0,50 = 0,225 the result of the calculation of slope stability for dynamic load with obe conditions as follows: table. 5 result of safety factor dynamic load, return periode t = 100 year (obe) no condition fsmin safety factor bishop janbu 0.25 0.5 0.75 1 0.25 0.5 0.75 1 1 slope : u/s-empty 1.1 1.941 1.959 1.967 1.976 1.833 1.85 1.858 1.866 2 slope : d/s-empty 1.1 1.644 1.645 1.645 1.646 1.605 1.606 1.607 1.607 3 slope : u/s lwl 1.1 1.914 1.959 1.967 1.976 1.845 1.85 1.858 1.866 4 slope : d/s lwl 1.1 1.644 1.645 1.645 1.646 1.605 1.606 1.607 1.607 5 slope : u/s – nwl 1.1 2.664 2.691 2.703 2.716 2.663 2.69 2.702 2.715 6 slope : d/s nwl 1.1 1.513 1.516 1.517 1.518 1.426 1.429 1.43 1.431 7 slope : u/s – hwl 1.1 2.664 2.691 2.703 2.716 2.663 2.69 2.702 2.715 8 slope : d/s – hwl 1.1 1.52 1.522 1.523 1.524 1.462 1.464 1.464 1.465 9 slope : u/s rapid drawdown 1.1 0.809* 0.786* 0.778* 0.758* 0.749* 0.725* 0.717* 0.698* 10 slope : d/srapid drawdown 1.1 1.627 1.628 1.629 1.63 1.606 1.607 1.607 1.608 reference: calculation and analysis note = * (safety factor < 1,1) category is not safe table 6. result of safety factor for dynamic load, return periode t = 3.000 year (mde) no condition fsmin safety factor bishop janbu 0.25 0.5 0.75 1 0.25 0.5 0.75 1 1 slope : u/s-empty 1.1 1.828 1.858 1.872 1.887 1.737 1.765 1.779 1.793 2 slope : d/s-empty 1.1 1.64 1.641 1.641 1.642 1.601 1.602 1.603 1.603 3 slope : u/s lwl 1.1 1.828 1.857 1.871 1.886 1.736 1.764 1.778 1.793 4 slope : d/s lwl 1.1 1.64 1.641 1.641 1.642 1.601 1.602 1.603 1.603 5 slope : u/s – nwl 1.1 2.495 2.538 2.559 2.581 2.496 2.539 2.56 2.582 6 slope : d/s nwl 1.1 1.498 1.502 1.504 1.506 1.412 1.415 1.417 1.419 7 slope : u/s – hwl 1.1 2.495 2.538 2.559 2.581 2.496 2.539 2.56 2.582 8 slope : d/s – hwl 1.1 1.506 1.51 1.512 1.513 1.449 1.452 1.454 1.455 9 slope : u/s rapid drawdown 1.1 0.887* 0.869* 0.858* 0.849* 0.821* 0.805* 0.794* 0.786* 10 slope : d/srapid drawdown 1.1 1.62 1.622 1.623 1.624 1.599 1.601 1.602 1.602 reference: calculation and analysis note = * (safety factor < 1,1) category is not safe from the analysis above shows that the dynamic load conditions, slope stability ngancar dam are safe against seismic load conditions return period of 100 years and 3,000 years, but both are critical civil and environmental science journal vol. ii, no. 02, pp. 117-127, 2019 127 to the rapid drawdown conditions. it makes an important record in the implementation of guidelines for operating the reservoir in order to avoid or be careful. 4. conclusion based on the analysis of hydro-geotechnical above, the dam safety conditions on ngancar dam can be concluded in the category enough, this is because some instruments existing dam has not been optimal in monitoring the safety of dams. not all piezometers functioning properly. also, the presence of the deformation instrument is not monitored continuously, in addition, to aspects of security and stability is less secure conditions of rapid drawdown. also, observations of several springs around the dam need to be done, given the amount of seepage from the spring on the right side of the dam there are bigger symptoms. references [1] anonymous, 1992. rehabilitation of additional six dams in central java, planning note ngancar dam, associated consulting engineer ace (pvt) ltd [2] pr. bamane and dr.s.s.valunjkar, 2014 dam safety instrumentation, american journal of engineering research (ajer) e-issn : 2320-0847 p-issn : 2320-0936 page 58-62 [3] anonymous, 2003 guidelines inspection/evaluation dam and the guidelines for common criteria dam design, sk dirjen sda/kkb no.05 / kpts / 2003. dam safety commission. [4] xiaoli ding and hui qin, 1998 geotechnical instruments in structural monitoring, journal of geospatial engineering, vol. 2, no.2, pp.45-56 [5] seepage modelling with seep/w, an engineering methodology july 2012 edition geo-slope international ltd. [6] e fadaei kermani and g. a barani, 2012, seepage analysis through earth dam based on finite difference method, journal of basic and applied scientific research issn 2090-4304 vol 2 (11) page 11621-11625. [7] ms abhilasha p.s and t.g antony balan, 2013, numerical analysis of seepage in embankment dams, iosr journal of mechanical and civil engineering (iosr-jmce) e-issn: 2278-1684, p-issn: 2320-334x pp 13-23. [8] crisinta eka putri, 2013, pengaruh kepemimpinan, motivasi dan lingkungan terhadap kinerja karyawan di yayasan yoseph freinademetz surabaya. jurnal ilmu & riset manajemen vol 2 no. 9 [9] sosrodarsono, suyono & takeda, kensaku. 1989. bendungan type urugan. jakarta: erlangga. [10] anonymous, 2004. stability analysis of earth fill dams due to earthquake load. guidelines of pdt14-2004. ministry public work and transport. [11] yu zhao, zi-yhi tong and qing lu, 2014. slope stability analysis using slice-wise factor of safety, hindawi publishing corporation, mathematical problems in engineering, volume 2014, article id 712145, 6 pages. [12] ammar rouaiguia and mohammed a. dahim, 2013, numerical modeling of slope stability analysis, international journal of engineering science and innovative technology (ijesit), issn: 2319-5967 civil and environmental science journal vol. 5, no. 1, pp. 045-054, 2022 45 public attitude to urban public transportation services in jember, indonesia willy kriswardhana1,*, nunung nuring hayati2, achmad reza kusdiyanto1 1 department of civil engineering, faculty of engineering, universitas jember, jember, 68121, indonesia 2 urban and regional planning study program, faculty of engineering, universitas jember, jember, 68121, indonesia *willy.teknik@unej.ac.id received 28-02-2022; accepted 03-04-20221 abstract. in this current condition, people’s interest in using public transportation in jember is decreasing with a low load factor value below 50%. it can be caused by the quality of services provided by service providers to the satisfaction of public transport users. this study aims to examine the users’ satisfaction and investigate the willingness to pay (wtp) for public transport services in jember. importance-performance analysis (ipa) method is used to determine the level of satisfaction of public transport users in jember district. the descriptive statistics are performed to understand the wtp value. the satisfaction level of public transport users is obtained from several attributes that belong to the cartesian diagram. the attributes that need improvement are the punctuality of the services, providing a sense of security and comfort and first aid facilities. the user's wtp is rp.4,000.00 rp.5,000.00. directions for future studies are presented. keywords: customer satisfaction, public transport, service quality, willingness to pay 1. introduction urban public transportation is a transport mode needed to support economic activities and urban development. urban transportation services must be implemented efficiently and effectively. the criteria for fast, safe, adequate capacity, convenience, and affordable transportation fares need to be considered in implementing good services of urban public transport. the facilities of public transport such as stops for boarding and dropping passengers that could be at any place and existing routes make this an advantage and one of the attractions for service users, unlike public transportation such as buses that have specific stops [1]. the decline in the quality of urban public transportation services is partly due to the less than optimal service from service providers [2]. public transportation in jember is one of the means of mobility for the community to meet the needs of daily life. urban public transportation in the form of lyn (8 seaters car) serves 17 1 cite this as: kriswardhana, w., hayati, n.n., & kusdiyanto, a.r. (2022). public attitude to urban public transportation services in jember, indonesia. civil and environmental science journal (civense), 5(1), 45-54. doi: https://doi.org/10.21776/ub.civense.2022.00501.5 civil and environmental science journal vol. 5, no. 1, pp. 045-054, 2022 46 transportation routes [3]. a study in jember [4] stated that public transportation in jember had a load factor of 50% in 2015. based on the criteria contained in sk 678/aj.206/drjd/2002 concerning technical guidelines for the implementation of public transportation in urban areas, public transport routes should be fixed and regular. based on department of transportation jember data, 80% of the urban public transportation system in jember needs to be improved. public interest decreased due to the fleet that was not feasible to operate. high investment costs and low potential demand make many unmaintained fleet conditions [5]. the tariffs for public transport in jember currently are idr 5,000 for the public and idr 2,500 for students. the determination of the basic tariff should be calculated based on willingness to pay (wtp). the correct calculation was expected to produce urban transportation fares that are reasonably fair for producers and consumers so that urban transportation becomes the primary choice of transportation means. the cause of the poor condition of public transport is the insufficient level of service provided by providers. this condition leads to the low satisfaction of public transport users. some factors affect the satisfaction of public transportation users, such as reliability, responsiveness, assurance, empathy, and tangible. efforts to increase the interest of public transport users in jember regency need to be carried out to solve the existing transportation problems. therefore, this study aims to determine the level of service quality and the factors that influence the interest of service users and the suitability of transportation fares based on wtp. this study contributes to the public transport study in two notable ways. first, to date, there is no study examining the public transport services performance from the user’s point of view in jember. second, in terms of survey technique, besides letting respondents filled the survey by themselves, we conducted several online meetings to guide some respondents in completing the questionnaire. this technique also beneficial to extract more information from respondents, especially when we use open questions in the survey. 2. material and methods jember is the third biggest city in east java province, indonesia. based on the indonesian statistics data, jember’s population in 2015 was 2.409 million. jember has an area of 3.293 km2. this city has an urban public transport system called “lyn”. the performance of the urban public transport system is low due to the massive ownership of two-wheeled motorized vehicles, the popularity of the ridehailing system, and the inadequate condition of supporting facilities. therefore, jember has been chosen as a case study. 2.1. data collection method data needed in this research is primary data. the primary data was obtained directly from the field by distributing questionnaires to service users. a total of 400 respondents participated in this survey— the first section of the questionnaire mainly contained socio-demographic characteristics. in the second part, respondents were asked to indicate their preferences towards the service quality of public transportation in jember. this section required respondents to rate the importance and performance of service quality using a five-points likert scale. then, an open question regarding how much they are willing to pay for the service was asked. 2.2. data analysis data analysis is carried out using importance performance analysis (ipa). ipa is a tool in analyzing the performance of services provided with the level of satisfaction or expectations of users. the results of the comparison are in the form of conformity levels, which will later determine the priority scale in handling service improvements. ipa uses the performance and importance plotting of attributes scored by users into four quadrants: civil and environmental science journal vol. 5, no. 1, pp. 045-054, 2022 47 • quadrant 1: low performance – high importance: attributes in this group show primary weaknesses. users find these attributes essential. thus, the organization should improve these attributes to raise the user’s satisfaction. • quadrant 2: high performance – high performance: attributes falling to this category show major strength that has exceeded the standard performance level. users find these attributes important, and they are satisfied with the performances. • quadrant 3: low performance – low importance: attributes in this class show a low level of performance. however, these attributes are not too important, and they do not threaten an organization. • quadrant 4: high performance – low importance: attributes falling to this category have low potential to level up users' satisfaction. although these attributes have high performances, users do not regard them as essential. the ipa method has been extensively used to investigate the user’s satisfaction towards transportation services. a study in iran [6] use ipa to investigate the service attributes of the bus. this study argues that the policymakers should improve the comfort attributes such as cleanliness, ventilation, and facilities for disabled people and the elderly. another study in aceh [7] shows that there are several attributes that needed to be improved, such as arrival time punctuality, waiting time, passenger assistance, and available seats. meanwhile, ratnasari et al. [8] uses ipa method to examine users’ satisfaction toward railway station performance. service attributes are obtained from the selection process with the general criteria needed by the community regarding existing public transportation services with a servsqual approach. there are eleven service attributes that are included in 5 variable dimensions with symbols. table 1. attributes of public transportation services in jember dimension symbol statements reliability a places of the arrival of public transportation match the route b a stop (hop on/off) closes to the main road c punctuality of arrival or departure of public transport matches the schedule responsiveness d the speed of driver responds to complaints from transportation service users e the speed of the driver responds to an emergency on the way assurance f the driver provides a sense of security and comfort while travelling g availability of accident/safety insurance empathy h the friendliness of the driver on the trip i the willingness of the driver to serve if a problem occurs on the way tangible j availability of good roads along the route k availability of health facilities/ first aid in public transportation 3. result and discussion table 2 provides a summary of the socio-demographic characteristics of the respondents. we have a balanced sampling of gender. more than half of respondents have senior high school education qualifications (65%) and are students (68%). this finding matches with the trip purpose where 59% of them are trip for school. most of the respondents have income under idr 1,000,000. civil and environmental science journal vol. 5, no. 1, pp. 045-054, 2022 48 table 2. socio-demographic characteristics characteristics number of respondents percentage gender male 198 50% female 202 50% age 10 – 18 years 53 13% 19 – 27 years 263 66% 28 – 36 years 36 9% 37 – 45 years 21 5% > 46 years 27 7% education junior high school 14 4% senior high school 261 65% vocational degree 37 9% bachelor’s degree 85 21% postgraduate degree 2 1% occupation student 270 68% civil servant 25 6% private sector 48 12% entrepreneurship 45 11% trip purpose work/business 73 18% family business 41 10% school 234 59% leisure 45 11% income (million) < idr 1 231 58% idr 1 – 2 54 13% idr 2 – 3 47 12% idr 3 – 4 43 11% idr 4 – 5 19 5% > idr 5 6 1% 3.1. validity and reliability test the validity and reliability tests are used to determine whether the data collected is valid or not by matching the calculated r-arithmetic, cronbach α and r-tables. the validity test is obtained by correlating each attribute score with the sum of the overall attribute scores offered. suppose the results of the number of attribute scores are significantly correlated with the results of each attribute. in that case, the interpretation of the attribute values can be said to be successful (table 3). the level of consistency of answers to questions that have been given to respondents can be known after conducting a reliability test. the results of the questionnaire can be said to be consistent if the reliability testing is completed. reliability test is the level of accuracy, precision, and service attributes. service attributes can be declared reliable or trustworthy if the cronbach α > 0.7 [9] (table 4). civil and environmental science journal vol. 5, no. 1, pp. 045-054, 2022 49 table 3. validity test of service attribute expectation and performance attributes r table expectation performance r arithmetic explanation r arithmetic explanation a 0.098 0.593 valid 0.695 valid b 0.098 0.662 valid 0.669 valid c 0.098 0.599 valid 0.744 valid d 0.098 0.538 valid 0.733 valid e 0.098 0.641 valid 0.754 valid f 0.098 0.577 valid 0.668 valid g 0.098 0.612 valid 0.711 valid h 0.098 0.672 valid 0.739 valid i 0.098 0.69 valid 0.761 valid j 0.098 0.682 valid 0.733 valid k 0.098 0.48 valid 0.681 valid table 4. reliability test of service attribute expectation and performance attributes expectation performance cronbach α explanation cronbach α explanation a 0.734 reliable 0.754 reliable b 0.729 reliable 0.753 reliable c 0.734 reliable 0.748 reliable d 0.737 reliable 0.750 reliable e 0.730 reliable 0.749 reliable f 0.737 reliable 0.751 reliable g 0.733 reliable 0.748 reliable h 0.729 reliable 0.750 reliable i 0.726 reliable 0.750 reliable j 0.731 reliable 0.748 reliable k 0.740 reliable 0.749 reliable 3.2. user satisfaction analysis of public transport services in jember user satisfaction of public transport services is obtained from the level of importance (expectations) and performance levels by interviewing respondents. after obtaining the results, the actions to improve the service attributes can be determined (table 5). the value of the highest level of importance for the service attribute is that the driver provides a sense of security and comfort with the symbol f, while the value of the level of importance for the smallest attribute is the speed with which the driver responds to complaints from service users with the symbol d. the average value of importance and level of performance is used to determine the coordinates of the cartesian diagram. the coordinates of each attribute have an effect on determining the grouping of the four quadrants of the cartesian diagram. on the x-axis, the quadrant axis value is obtained at the point of 2.5236, and on the y-axis, the quadrant axis value is 3.5806. the average value is obtained from the sum of the average values of x and the average of y divided by the number of service attributes. civil and environmental science journal vol. 5, no. 1, pp. 045-054, 2022 50 table 5. average value of interest level and performance level a tt ri b u te s ∑ x ∑ y a v e ra g e o f x a v e ra g e o f y a 1120 1443 2.8 3.6075 b 1084 1440 2.71 3.6 c 984 1454 2.46 3.635 d 1010 1377 2.525 3.4425 e 1049 1413 2.6225 3.5325 f 915 1500 2.2875 3.75 g 1040 1442 2.6 3.605 i 1056 1398 2.64 3.495 j 1010 1440 2.525 3.6 k 754 1433 1.885 3.5825 table 6. conformity rate value a tt ri b u te s ∑ x ∑ y c o n fo rm it y r a te p e rc e n ta g e (% ) a 1120 1443 0.7762 77.62 b 1084 1440 0.7528 75.28 c 984 1454 0.6768 67.68 d 1010 1377 0.7335 73.35 e 1049 1413 0.7424 74.24 f 915 1500 0.6100 61.00 g 1040 1442 0.7212 72.12 h 1082 1415 0.7647 76.47 i 1056 1398 0.7554 75.54 j 1010 1440 0.7014 70.14 k 754 1433 0.5262 52.62 the priority order of service improvements to achieve user satisfaction is determined by the percentage value of the level of service attribute conformity (table 6). next, we compared the value of the level of conformity with the value of the decision-making score. if the results of the level of conformity have a lower value than the value of the decisionmaking score, the attribute needs to be treated with improvement (action); if the result of the level of conformity is higher, then the attribute needs to be maintained its performance (hold). table 7. result of hold and action attribute conformity level (%) decision score hold and action a 77.6161 70.5488 hold b 75.2778 hold c 67.6754 action d 73.3479 hold e 74.2392 hold f 61.0000 action g 72.1220 hold h 76.4664 hold i 75.5365 hold j 70.1389 action k 52.6169 action in table 7, the results of hold and action are obtained from each attribute of public transportation services. attributes a, b, d, e, g, h, and i with hold results mean that attributes with a level of conformity above the decision score need to be maintained or service quality improved. while attributes c, f, and j with a level of conformity below the decision score need improvement. in figure 1, we get a cartesian diagram with four quadrants and the position of the attribute points of each quadrant. there are attributes c, f, and k in quadrant i, which means that the service attributes civil and environmental science journal vol. 5, no. 1, pp. 045-054, 2022 51 need improvements. in quadrant ii, attributes a, b, g, and j mean that the service attributes are classified as good performance and high importance, so they need to be maintained. in quadrant iv, attributes d, e, h, and i mean that the service attributes are classified as having good performance but are not considered essential by service users. figure 1. cartesian diagram of public transport service attributes figure 2. gap between performance and importance it can be seen from figure 2 that the value of the importance level of all service attributes is on average 1,400 while the value of the performance level of all service attributes is on average 1 ,000. civil and environmental science journal vol. 5, no. 1, pp. 045-054, 2022 52 this shows that all service attributes are considered important by users. all attributes are considered to have poor performance. 3.3. public transport fare based on wtp wtp analysis was conducted to determine the willingness of passengers to pay fares with service facilities provided by the owner or driver of urban public transportation. in the questionnaire, there are several choices of public transportation fares offered to range from idr 2,000 to idr 6,000. users have the freedom to choose the tariff according to their willingness to pay for the services. figure 3. wtp for public transport services the fare based on the wtp survey for urban public transport passengers in jember regency is idr 4,000 – idr 5,000. the largest percentage of passengers chose willingness to pay range in accordance with the current urban public transport operating fare, which is idr 5,000. this proves that the suitability of the current tariff is still considered good by passengers. 3.4. discussion and policy implications attributes that need improvements are the punctuality of departure and arrival of the services, the safety and comfort, and the first aid facility in the public transportation. public transportation services in most developing countries are unreliable and do not have a fixed schedule. a study in malaysia [10] argues that reliability (e.g. punctuality, frequency) is essential in choosing transport modes. this study also states that the safety factor is a major concern and needs to be improved to increase users' satisfaction with bus services. this aligns with a study in amman, jordan [10] which states that the safety of travel on public transportation is the most important factor needing improvement. in this study, many attributes are classified into quadrants ii and iv. places of arrival attribute found to be classified in quadrant ii. it indicates that customers do really care about the arrival places of the public transport, as long as the services are running on their routes, customers will be satisfied. this condition explains the condition of public transport in most developing countries, where public transport can stop everywhere at the customers' request. respondents also indicated that accident insurance is essential for them. this is aligned with a study in bandung [11] which states that respondents do not agree to pay insurance premium although they know that it is important for them. civil and environmental science journal vol. 5, no. 1, pp. 045-054, 2022 53 meanwhile, driver’s response regarding speed complaints is not important. however, a study in denmark [12] find that speeding is one factor that influences the bus accident severity level. therefore, these attributes should be maintained well to increase the number of customers. driver’s friendliness is also found to be less important for customers. nevertheless, a study in columbia [13] suggests that drivers' kindness is important and that authorities should train their brt drivers and staff to improve communication skills. 4. conclusions using a case study in jember, indonesia, eleven public transport attributes were evaluated by performing ipa. the reliability and validity test showed that attributes used in this study were acceptable. ipa results indicated that transport agencies and policymakers should improve the punctuality of the arrival and departure schedule. the safety factor is one of the essential needs to be improved to raise the satisfaction of users towards the services. in addition, public transport providers should occupy their services with the first aid facilities. wtp survey showed that respondents were satisfied with the fares. users are willing to pay in the range of idr 4,000 – idr 5,000. this value is relatively similar with the actual tariff of public transportation in jember. this study's limitation is that the attributes used were extracted from the current regulation. future studies can explore more attributes extracted from the previous studies, such as cleanliness [6] and vehicle safety against accidents [14], [15]. furthermore, including fares as a factor to investigate the satisfaction of public transport users can be a good idea [16]. other methods could give additional insights regarding the user’s satisfaction study towards transportation services, such as ordinal logistic regression [17], [18] and important-satisfaction analysis [19]. references [1] m. h and l. b. said, “analisis penyebab penurunan minat pengguna angkutan umum mikrolet di kota makassar,” vol. 3, no. 2, pp. 94–101, 2020, doi: 10.31219/osf.io/mxy26. [2] a. munawar, “perencanaan angkutan umum perkotaan berkelanjutan,” unisia, vol. 29, no. 59, pp. 53–59, 2006, doi: 10.20885/unisia.vol29.iss59.art2. [3] s. sulistyono, j. w. soetjipto, and w. hariadi, “analisis tarif angkutan umum kota jember berdasarkan biaya biaya operasi kendaraan (bok) dan pendapatan,” simp. xi fstpt, univ. diponegoro, no. october, pp. 1–11, 2008. [4] n. n. hayati, s. sulistyono, and w. sabiq, “strategi peningkatan kinerja trayek utama angkutan umum perkotaan jember,” 18th fstpt int. symp. unila, bandar lampung, august 28th, 2015, 2015. [5] s. sulistyono et al., “kebijakan penataan jaringan trayek angkutan umum perkotaan jember,” vol. 17, no. 2, pp. 99–110, 2017. [6] j. esmailpour, k. aghabayk, m. abrari vajari, and c. de gruyter, “importance – performance analysis (ipa) of bus service attributes: a case study in a developing country,” transp. res. part a policy pract., vol. 142, pp. 129–150, dec. 2020, doi: 10.1016/j.tra.2020.10.020. [7] f. fachrurrozy, e. wulandari, and y. darma, “the study of the operation of trans koetaradja public bus transportation of the corridor ii a and ii b in banda aceh city,” in iop conference series: materials science and engineering, 2020, vol. 933, no. 1, doi: 10.1088/1757-899x/933/1/012021. [8] s. d. ratnasari, w. kriswardhana, and n. n. hayati, “evaluasi standar pelayanan minimum dan tingkat kepuasan penumpang di stasiun kereta api jember dengan penerapan sistem boarding pass,” j. rekayasa sipil dan lingkung., vol. 1, no. 02, 2017, doi: 10.19184/jrsl.v1i02.6043. civil and environmental science journal vol. 5, no. 1, pp. 045-054, 2022 54 [9] i. ghozali, “aplikasi analisis multivariate dengan program ibm dan spss.,” in aplikasi analisis multivariate dengan program ibm spss 19, 2011. [10] m. n. borhan, a. n. hakimi ibrahim, d. syamsunur, and r. a. rahmat, “why public bus is a less attractive mode of transport: a case study of putrajaya, malaysia,” period. polytech. transp. eng., vol. 47, no. 1, 2019, doi: 10.3311/pptr.9228. [11] t. b. joewono and h. kubota, “safety and security improvement in public transportation based on public perception in developing countries,” iatss res., vol. 30, no. 1, 2006, doi: 10.1016/s0386-1112(14)60159-x. [12] c. g. prato and s. kaplan, “bus accident severity and passenger injury: evidence from denmark,” eur. transp. res. rev., vol. 6, no. 1, 2014, doi: 10.1007/s12544-013-0107-z. [13] l. márquez, r. pico, and v. cantillo, “understanding captive user behavior in the competition between brt and motorcycle taxis,” transp. policy, vol. 61, 2018, doi: 10.1016/j.tranpol.2017.10.003. [14] j. allen, j. c. muñoz, and j. rosell, “effect of a major network reform on bus transit satisfaction,” transp. res. part a policy pract., vol. 124, 2019, doi: 10.1016/j.tra.2019.04.002. [15] j. allen, l. eboli, c. forciniti, g. mazzulla, and j. de d. ortúzar, “the role of critical incidents and involvement in transit satisfaction and loyalty,” transp. policy, vol. 75, 2019, doi: 10.1016/j.tranpol.2019.01.005. [16] c. zhang, y. liu, w. lu, and g. xiao, “evaluating passenger satisfaction index based on plssem model: evidence from chinese public transport service,” transp. res. part a policy pract., vol. 120, 2019, doi: 10.1016/j.tra.2018.12.013. [17] g. c. l. bezerra and c. f. gomes, “the effects of service quality dimensions and passenger characteristics on passenger’s overall satisfaction with an airport,” j. air transp. manag., vol. 44–45, pp. 77–81, 2015, doi: 10.1016/j.jairtraman.2015.03.001. [18] w. kriswardhana, n. n. hayati, and r. septiana desy, “passenger satisfaction with railway station service quality: an ordinal logistic regression approach,” in matec web of conferences, 2018, vol. 181, doi: 10.1051/matecconf/201818107001. [19] r. c. p. wong, w. y. szeto, l. yang, y. c. li, and s. c. wong, “elderly users’ level of satisfaction with public transport services in a high-density and transit-oriented city,” j. transp. heal., vol. 7, 2017, doi: 10.1016/j.jth.2017.10.004. open access proceedings journal of physics: conference series civil and environmental science journal vol. 05, no. 02, pp. 107-117, 2022 107 rainwater quality improvement model as an alternative source for drinking water in mojoagung district, jombang regency galih m. fatian 1*, hari siswoyo 1, riyanto haribowo 1 1) water resources engineering department, universitas brawijaya, malang, 65145, indonesia *galihfatian@gmail.com received 21-01-2022; accepted 17-05-2022 abstract. water is a basic need for humans, yet often the quality and quantity become constrained, as happened in mojoagung district, jombang regency. during the dry season, the potential for water reserves available for use is rainwater that has been stored. however, based on laboratory tests, the quality of the stored rainwater is below the quality standard due to its high kmno4 (calium permanganate) content. hence we need a simple filter to improve the water quality. researchers have conducted experiments with the filter composition of zeolite, activated charcoal, activated sand, sterile cotton, and aquarium filter. the results of the filtration process showed a significant decrease in potassium permanganate. the filtration results from the filter with the composition of zeolite, activated charcoal, activated sand, sterile cotton, and an aquarium filter sequentially 5 cm, 10 cm, 15 cm, 4 cm, and 2 cm succeeded in reducing potassium permanganate levels from 11.73 to an average of 2.12 mg. /l. due to experimental activities, the best filter will be integrated with the rainwater harvesting system, which has been discussed with related social communities and stakeholders. keywords: filtration, kmno4, rainwater harvesting, water 1. introduction it is estimated that more than 2 billion people per day are affected by water shortages [1]. indonesia has more than 200 million of population, but 119 million do not have access to clean drinking water, while the need is estimated to increase to 15-35%/capita/per year [2]. the difficult condition of the community in accessing clean water is also a problem in jombang regency, especially during the dry season. at least six sub-districts in jombang regency have the potential to experience drought in the dry season in 2020. the six sub-districts are wonosalam district, mojoagung district, bareng district, bandarkedungmulyo district, plandaan district, and kabuh district [3]. air kita foundation has been campaigning for the use of rainwater as drinking water since 2015. so far, the community has made initial observations using tds and ph tests [4]. based on the testing of the two parameters above, the test results were obtained where the value is still within the safe limit according to the minister of health number 492/menkes/per/iv/2010 [5]. however, to state that the water is suitable for consumption, it is not only ph and tds, but several parameters must be tested according to the standards of the ministry of health. for this reason, it is necessary to conduct further research related to the rainwater harvesting structure of pemanenan air hujan (pah) in mojoagung district. meanwhile, based on previous research related to pah, where there is rainwater that does not meet the 2010 minister of health [6 – 10], an effective pah tool is needed to filter chemical pollutants in rainwater. likewise, for the research case in the mojoagung sub-district, if rainwater pollution occurs in mojoagung, it is necessary to create an effective and efficient rainwater treatment model to make rainwater suitable as a source of raw water for drinking water. mailto:galihfatian@gmail.com civil and environmental science journal vol. 05, no. 02, pp. 107-117, 2022 108 2. material and methods 2.1. location and research period the research was conducted in mojoagung district, jombang regency, which is located between 112°33'50.372"e and 7°58'8.089"l (figure 1). the research starts from april 2021 to december 2021. figure 1. mojoagung districts map [11] 2.2. tools and materials the equipment used in the research phase of the correlation between rainwater quantity and quality includes a bucket to hold rainwater directly. siemen digital conductivity tester is used to measure electrical conductivity (dhl); a thermometer is used to measure water temperature. a ph meter is used to measure the ph value in rainwater caught directly in the bucket. sterile jerry cans to collect rainwater samples directly to be taken to the health laboratory in the jombang area. the material studied at this research stage is rain taken directly. the equipment used in the effectiveness of the filter's research phase includes a two-inch pvc pipe used for modeling tools. a tube made of mica with a two-inch diameter is used as a container for placing the filter composition. the filter uses zeolite material, activated sand, activated carbon, an aquarium filter, and sterile cotton. the material used for the test material is rainwater stored for four years. then, a sterile bottle brings the filtered water sample to the laboratory. while the equipment is used in the design research stage, a compatible laptop is to be installed with the autocad 2018 program to design the application of filters in the field. next, use the excel 2010 program to compile the total cost of applying the filter. 2.3. data collection the data in this research are divided into primary and secondary data with the following details: 1. primary data 1) rainwater sample the first collection was in april 2021 at the mojoagung and penanggalan barat bmkg stations for two rainy days with four samples. the second collection of stored water was in four locations civil and environmental science journal vol. 05, no. 02, pp. 107-117, 2022 109 with four samples. 2) quality of sample they were obtained from laboratory test results on all collected samples and filtration results. 3) interviews results of interviews and deliberation with the community and related stakeholders. 4) hydrological data daily rainfall data from mojoagung and penanggalan barat bmkg stations. 2. secondary data literature studies that are directly related to research. 2.4. research stages this research is divided into several stages as follows: a) analysis of the relationship between daily rainfall and rainwater quality the rainwater quality data obtained were compared with the daily rainfall intensity on the day of sampling. this analysis results in the relationship between the quality of the rainwater that falls and its intensity on the same days. the flowchart for this step is shown in figure 2. b) determining the filter variation the composition of the filter is determined after the pollutants are known from the results of laboratory analysis of rainwater and reservoir water. this stage is described in figure 3. c) rainwater filtering process after the filter composition used in the experiment has been determined, the next step is to conduct water filtration experiments with various combinations of compositions. this filtering process is shown in figure 4. d) pah building planning process the last stage for this research is pah planning to integrate with the chosen rainwater filter. the planning and integration process is described in figure 5. all samples of the filtration experiment results were sent to the laboratory to investigate which filter effectiveness was the best. after obtaining the best filter for filtering water, the last step is to integrate the filter with the pah building, which has been designed as a result of consultation with the community and related stakeholders. civil and environmental science journal vol. 05, no. 02, pp. 107-117, 2022 110 figure 2. analysis of the relationship between daily rainfall and rainwater quality figure 3. determining the process of filter variations civil and environmental science journal vol. 05, no. 02, pp. 107-117, 2022 111 figure 4. rainwater filtering process figure 5. pah planning process civil and environmental science journal vol. 05, no. 02, pp. 107-117, 2022 112 3. results and discussion 3.1. rainwater quality and quantity the first sampling in april 2021 had quality self-test results and daily rainfall data presented in table 1 and table 2. at the same time, samples with codes mjg 1, mjg 2, png 1, and png 2 water quality laboratory test results by jombang regional health laboratory are shown in table 3. table 1. mojoagung water quality and daily rainfall data table 2. penanggalan barat water quality and daily rainfall data tables 1 and 2 indicate that there is no relationship between daily rain thickness and rainwater quality due to several things, because of the following possible reasons: 1. rainwater quality at the research site did not experience significant changes based on the self -test results in tables 1 and 2. 2. the rainfall at the rain gauge station is not recorded because the intensity is too small. based on the test results at the health laboratory in the jombang area shown in table 3, rainwater was found to have a quality that met the standard of raw water, so it did not require a filtration process. but in reality, the rainwater that falls in the mojoagung area is not used directly by the community but is accommodated for use during the dry season when water supplies are reduced. this storage period is suspected to cause changes in the characteristics of rainwater and cause a decrease in water quality. therefore, the research was developed by conducting the second stage of sampling to ensure the condition of the quality of rainwater that is accommodated by the community. this second sampling stage must be carried out during the dry season when water supply conditions are very lacking, namely in october 2021. this stage survey collects four samples in each rainwater reservoir scattered in the research location. the storage period and the water quality test for each sample are presented in tables 4 and 5. tds te mpe rature (mg/l) ( o c) (mm) 08 april 2021 6.43 10.4 30.56 10 09 april 2021 6.75 19.2 25.8 10 april 2021 5.78 26 28.42 13 april 2021 4.75 15.8 26.2 15 april 2021 4.72 26 26.46 date rainwate r quality daily rainfall ph tds te mpe rature (mg/l) ( o c) (mm) 08 april 2021 5.28 15.2 27.66 14 09 april 2021 6.82 22.8 24.3 10 april 2021 5.55 42.2 26.92 13 april 2021 4.43 16.4 23.48 15 april 2021 4.26 13.8 24.08 4 date rainwate r quality daily rainfall ph civil and environmental science journal vol. 05, no. 02, pp. 107-117, 2022 113 table 3. rainwater quality laboratory test table 4. storage periods of each sample from table 5, it can be seen that some do not meet the quality standards, which are; 1. turbidity 2. potassium permanganate (kmno4) 3. total coliform 4. and ph of the four parameters that do not meet water quality standards, the levels of potassium permanganate (kmno4) and total coliform are very prominent, indicating that the longer the storage period, the higher the value of these two indicators. for this reason, it is necessary to design a filter device that can reduce the character content of raw water that has been described in general and the content of potassium permanganate (kmno4) in particular. the next step of the research is the stage of the filtration process. mjg 1 mjg 2 png 1 png 2 i. parameters directly related to health a. chemical an-organik 1 nitrite (as no2-) mg/l 1,0 < ld < ld < ld < ld 2 nitrate (as no3-) mg/l 10 1,2 1,7 1,3 1,0 3 fluorida (f) mg/l 1,5 0,17 0,24 0,22 0,22 ii. parameters that are not directly related to health a. physical parameters 1 smells # no smell no smell no smell no smell no smell 2 total dissolved solid (tds) mg/l 1000 1,8 20,5 18,9 17,0 3 turbidity ntu scale 5 1,74 3,9 1,53 3,05 4 taste # no taste no taste no taste no taste no taste 5 temperature o c ± 30 o c 22,8 o c 23,8 o c 23,8 o c 24,1 o c b. chemical parameters 1 ferrum mg/l 1,0 0,11 0,32 0,08 0,17 2 hardness mg/l 500 25 15 15 12 3 chloride mg/l 600 3,97 4,96 3,97 3,4 4 manganese mg/l 0,5 < ld < ld < ld < ld 5 ph # 8,5 7,18 7,19 7,22 6,99 6 residual chlorine mg/l 0,2 0,06 < ld < ld < ld 7 kmno4 mg/l 10,0 3,03 2,42 2,12 1,51 parame te rs unit maximum conte nt (ld) sample code sample code sample collection storage time sample 1 june – august 2021 ± 4 months sample 2 october – december 2020 ± 12 months sample 3 june – august 2020 ± 16 months sample 4 rainy season 2017 ± 4 years civil and environmental science journal vol. 05, no. 02, pp. 107-117, 2022 114 table 5. stored rainwater quality test results 3.2. filtration modeling from the literature that has been stated, no research has been found that discusses the effectiveness of using zeolite filters, activated charcoal, and activated sand to reduce kmno4 levels. however, these materials indicate being able to reduce kmno4 levels through the adsorption process [12]. then the choice of materials for the composition of the water filter in the experiment to be carried out is as follows: a. zeolite diameter 3 mm b. activated carbon 3 mm c. activated sand 1 mm the filter effectiveness experiment was carried out using ten variations of the filter. each filter produced two samples (a total of 20), which were then checked for quality in the laboratory. variations in the composition of each filter and their filtration results are presented in tables 6 and 7. table 7 is a recapitulation of laboratory tests by labkesda jombang on the quality of the filtration experiment results from all 20 samples of filters with codes a to j1. table 7 shows how the effectiveness and efficiency of each filter. it can be seen that the lowest kmno4 results were found in samples h1 and i with a value of 1.24 mg, respectively. meanwhile, the lowest turbidity value is in sample h with a value of 13.62 ntu. the graph of the filtration results for the kmno4 content is more clearly depicted in figure 6, while the results of the turbidity value are shown in figure 7. sample 1 sample 2 sample 3 sample 4 i. parameters directly related to health a. chemical an-organik 1 nitrite (as no2-) mg/l 1,0 0.03 0.02 0.03 0.02 2 nitrate (as no3-) mg/l 10 3 fluorida (f) mg/l 1,5 0.18 0.18 0.17 0.15 ii. parameters that are not directly related to health a. physical parameters 1 smells # no smell no smell no smell no smell no smell 2 total dissolved solid (tds) mg/l 1000 94.2 88.3 91.2 83.4 3 turbidity ntu scale 5 2.13 2.52 7.73 0.85 4 taste # no taste no taste no taste no taste no taste 5 temperature o c ± 30 o c 29.4 29.8 29.1 29.1 b. chemical parameters 1 ferrum mg/l 1,0 0.05 0.05 0.05 0.05 2 hardness mg/l 500 75 55 59 69 3 chloride mg/l 600 7.4 6.9 5.9 7.9 4 manganese mg/l 0,5 0.035 0.032 0.221 0.015 5 ph # 8,5 8.71 8.41 8.14 7.74 6 residual chlorine mg/l 0,2 0.07 0.05 0.14 0.05 7 kmno4 mg/l 10,0 8.6 9.5 11.37 11.5 iii. microbiology parameter 1 total of coliform mpn/ 100 ml 0 23 33 33 46 sample code parameters unit maximum content (ld) civil and environmental science journal vol. 05, no. 02, pp. 107-117, 2022 115 table 6. experiment filter variations table 7. filterred stored water quality figure 6 and figure 7 show the filtration results for all filters. as seen in the table and figure, the filter that can reduce the best kmno4, which was originally valued at 11.5 mg/l to an average of 2.32 ((3.4 + 1.24)/2) mg/l is filter h which has an average turbidity value of 15.325 ((13.62) +17.03)/2) mg/l. the composition of filter h is zeolite, activated charcoal, activated sand, and sterile cotton; aquarium filters are 5 cm, 10 cm, 15 cm, 4 cm, and 2 cm, respectively. the filter height will be incorporated into the rainwater harvesting (pah) building scheme. filter code compositions thickness (cm) filter code compositions thickness (cm) zeolite 5 zeolite 15 activated charcoal 5 activated charcoal 5 activated sand 5 activated sand 5 zeolite 5 sterile cotton filter 4 activated charcoal 5 aquarium filter 2 activated sand 10 zeolite 5 zeolite 5 activated charcoal 10 activated charcoal 5 activated sand 15 activated sand 15 sterile cotton filter 4 zeolite 5 aquarium filter 2 activated charcoal 10 zeolite 5 activated sand 5 activated charcoal 15 zeolite 5 activated sand 10 activated charcoal 15 sterile cotton filter 4 activated sand 5 aquarium filter 2 zeolite 10 zeolite 10 activated charcoal 5 activated charcoal 10 activated sand 5 activated sand 10 sterile cotton filter 4 sterile cotton filter 4 aquarium filter 2 aquarium filter 2 9 filter i 5 filter e 6 filter f 10 filter j 1 filter a 7 filter g 2 filter b 8 filter h3 filter c 4 filter d kmno4 turbidity kmno4 turbidity (mg/l) (ntu) (mg/l) (ntu) 1 a 17.96 93.1 11 f 4.02 81.3 2 a1 13.32 233 12 f1 4.02 76.1 3 b 18.58 91.1 13 g 6.19 64.1 4 b1 11.15 290 14 g1 5.88 49.1 5 c 13.01 87.3 15 h 3.4 13.62 6 c1 4.33 271 16 h1 1.24 17.03 7 d 20.75 98.5 17 i 1.24 15.71 8 d1 13.32 115 18 i1 8.98 20.3 9 e 18.27 71.5 19 j 8.67 16.23 10 e1 8.67 78.1 20 j1 4.33 22.5 sample sample civil and environmental science journal vol. 05, no. 02, pp. 107-117, 2022 116 figure 6. filtered result of kmno4 contain figure 7. turbidity level of filtered water 3.3. pah building planning after getting which filter is the best (filter h), the next step is to integrate the filter into a rainwater harvesting (pah) building scheme based on literature studies and consultations with the community and related stakeholders. the rainwater harvesting process starts from the rainwater that falls on the roof of the house and flows through gutters to the storage reservoir and is stored. when needed to be used, water from the reservoir is channeled to the filter installed in the pah installation and then to the outlet. the type of water filter used is the slow flow type. determination of the type of slow water filter is due to several advantages, including:: 1. simple and relatively easy to implement even by ordinary people; 2. no chemical additives 3. low operating and maintenance costs; 4. operation and maintenance, such as washing the filtration material, is relatively easy. 4. conclusion the results of this research are as follows: 1. the quantity of rainwater that fell directly at the study site at the time of the study was very small, with a range of 0-14 mm. this was due to the entry of the dry season. the quality of rainwater that fell directly at the study site at the study time met the standard water standards according to the 17,96 13,32 18,58 11,15 13,01 4,33 20,75 13,32 18,27 8,67 4,02 4,02 6,19 5,88 3,4 1,24 1,24 8,98 8,67 4,33 a a1 b b1 c c1 d d1 e e1 f f1 g g1 h h1 i i1 j j1 k m n o 4 f i l t r a t i o n r e s u l t ( m g / l ) 93,1 233 91,1 290 87,3 271 98,5 115 71,5 78,1 81,3 76,1 64,1 49,1 13,62 17,03 15,71 20,3 16,23 22,5 a a1 b b1 c c1 d d1 e e1 f f1 g g1 h h1 i i1 j j1 turbidity l e ve l (ntu) civil and environmental science journal vol. 05, no. 02, pp. 107-117, 2022 117 minister of health regulation no. 492/menkes/per/iv/2010. 2. an effective filter model to improve rainwater quality (kmno4) at the research site is a filter model using a slow-flow filter scheme with a composition, aquarium filter, sterile cotton, zeolite, activated charcoal, and activated sand. for comparison, the best composition of zeolite, activated charcoal, and activated sand is 1:2:3. references [1] world health organization. 2000. the world health report 2000 health systems: improving performance. world health organization assesses the world's health systems. [2] untari, t., & kusnadi, j. 2015. pemanfaatan air hujan sebagai air layak konsumsi di kota malang dengan metode modifikasi filtrasi sederhana. jurnal pangan dan agroindustri vol. 3 no 4 p.1492-1502, september 2015. [3] https://kabarjombang.com/enam-kecamatan-di-jombang-terancam-kekeringan-bpbd-luas-danjarak-jadi-kendala-penanggulangan/, accessed on 11 desember 2020 [4] https://surabaya.tribunnews.com/2020/03/01/komunitas-air-kita-di-desa-karangwinonganjombang-beri-edukasi-tentang-manfaat-air-hujan, accessed on 11 desember 2020). [5] peraturan menteri kesehatan ri no. 492/ menkes/ per/ iv/ 2010 tentang peryaratan kualitas air minum. [6] sudarmadji, 1975. analisa unit kualitas airtanah di daerah aliran kali serayu. skripsi sarjana fakultas geografi ugm, yogyakarta. [7] sudarmadji, 1995. beberapa aspek hidrokimia hutan pinus. majalah geografi indonesia no. 16 tahun 10. september 1995. (dalam penerbitan). [8] sudarmadji. 1997. perbandingan kualitas air hujan di kotamadya yogyakarta dan daerah perdesaan sekitarnya. universitas gajah mada, yogyakarta. [9] asma irma setianingsih. 1989. kualitas air hujan di parangtritis sampa puncak gunungapi merapi dan faktor – faktor yang mempengaruhinya. skripsi sarjana program s1. fakultas geografi ugm, yogyakarta. [10] satriawan, d., 2018. analisis kuantitatif acidity level sebagai indikator kualitas air hujan di kabupaten cilacap. jurnal rekayasa sistem industri, 3(2), pp.112-116. [11] pn jombang (pn-jombang.go.id). 2022 [12] davis, m.l., 2010. water and wastewater engineering: design principles and practice. mcgrawhill education. open access proceedings journal of physics: conference series civil and environmental science journal vol. 05, no. 02, pp. 194-201, 2022 194 landslide threat analysis and slope reinforcement method with sheet pile on singaraja city boundary road – mengwitani km 37+900 right i made adi wirasana 1 , i nengah sinarta 2 , ni komang armaeni 3 1 student of civil engineering, faculty of engineering and building planning, warmadewa university, denpasar, bali, indonesia. 2 lecturer of civil engineering, faculty of engineering and building planning, warmadewa university, denpasar, bali, indonesia email: inengahsinartaftpsipil@gmail.com received: 28-07-2022; accepted 15-08-2022 abstracts. factors triggering landslides due to high rainfall intensity and long duration cause the soil to become saturated. every rainy season, the singaraja-mengwitani city road section always landslides due to the geometry of the road adjacent to the slope because it is in a hilly area. the study was carried out through field investigations with two drill points 30m deep, and slope stability analysis with geoslope software obtained the value of the existing slope safety factor of 0.939, while at the time of moderate rain for 6 hours at 0.236 based on saturated soil parameters, so it is necessary to strengthen. strengthening is carried out with an embedded long steel sheet pile 7.15m deep, with the total length of the sheet pile used being 9.15m, based on the results of the analysis after strengthening the steel sheet pile in the safety factor value of 1.674, while at the time of moderate rain for 6 hours at 1.131 then the slope is declared stable due to sf>1.0. keywords: slope stability, safety factor, geostudio, steel sheet pile. 1. introduction the intensity of rain is high with a long rain duration so that water infiltration is increasingly entering the slopes to increase the saturation rate and pore water pressure, the pore water pressure, which is initially negative value will increase to zero value and then rise so that the positive value of this change occurs quickly, especially in loamy silt soils [1]. the ancient mountains around the walls of the southern batur caldera, with constituent rocks sourced from the buyan – bratan and batur volcanic rocks, are composed of rock sand to loose and porous silt sand. these conditions tend to be easily released, so moderate rain intensity with a long frequency will cause soil movement in the form of flash floods [2]. rainfall that falls on a slope will partially infiltrate and then saturate the soil. the condition of the physical properties of the earth, marbles, and soil layers that vary between water escape and impermeability and the amount of water that inflates will affect the occurrence of landslides [3]. the mountainous area of bali-tengah, especially the ancient mountains of buyanberatan, is an area that is prone to landslides, especially during the rainy season because the area is a rain catchment area, the threat of landslides that often occur is landslides with mud and sandy rocks when the rain intensity reaches 87,32-92,27 mm / day [4]. the singaraja – mengwitani city limits road section is a region iii national road of bali province which has a length of 60,430 kilometers, the singaraja – mengwitani city boundary road section starts from simpang 4 mengwitani at km 13 + 950 to the singaraja city limit at km 74 + 380. on the singaraja city limits starting road section precisely at km 37 + 900 right, there is a high and steep slope on which one day there can be a landslide. before a mailto:inengahsinartaftpsipil@gmail.com civil and environmental science journal vol. 05, no. 02, pp. 194-201, 2022 195 landslide occurs due to high rainfall intensity, it is necessary to study or analyze the safe numbers of existing conditions and conditions after strengthening. several studies have been conducted, particularly in analyzing slope stability on slopes that fail due to high rain intensity. slope stability analysis requires an understanding of rain intensity and soil behavior in partially saturated conditions [5]. the result of the infiltration of saturated soils partly causes a change in the degree of soil saturation; an increase in the degree of saturation in a certain period will lead to landslides. this condition requires an understanding of the technical properties of partially saturated soils through an empirical approach based on rain characteristics so that it is known that changes in the degree of soil saturation to the parameters of soil shear strength (φo) and pore water stress (u). [6] in this study, a study and analysis of slope stability due to changes in soil saturation due to rainwater infiltration was carried out with the help of geoslope software. geostudio is a geotechnical software developed from canada. in this study, this program was used to analyze slope stability. analyzing the slope stability in this program we use slope / w, while the method used in this program is the plastic equilibrium limit method. in slope /w there are several boundary balance methods, including those used in this study are the bishop, ordinary, janbu and morgenstern-price methods [7] [8]. the stability of the slopes can be improved in various ways. one of them is to increase the retaining force through the existence of an earthen retaining structure by using walls or poles. in indonesia, several soil retaining constructions can be used as a countermeasure against cladding, one of which is to use a pile or sheet pile [9]. [10] the study began with hydrological analysis and the safe numbers of the existing slopes and then the analysis of the safe numbers after being given sheet pile reinforcement, this type of strengthening was carried out because the land on the existing slopes was limited. 2. materials and methods in this study, the interpretation of rock outcrops and analysis of geomorphological conditions is an explanation of the appearance of the situation and actual morphological needs in the research area, which refers to the result of the process. geological processes that have occurred in the past and present. slope stability analysis using the limit equilibrium method with the help of the slope/w and seep/w programs in geostudio 2012, based on field data and compared with conditions in the field where a slope collapses, namely the safety factor value is less than 1. value of safety factor, as a result of rainwater infiltration. 2.1. research sites locations with the potential for landslides are on the singaraja mengwitani city boundary road, precisely at km 37+900 to the right of figure 1a. the research location based on google earth and topography is shown in figures 1b&1c. the figure shows that the existing land area is relatively steep with variations in land elevation of more than 10.0 m and is located in a complex of roads. (a) (b) (c) figure 1. research location (a) top view (b) side view from the road (c) side view from the bottom of the slope civil and environmental science journal vol. 05, no. 02, pp. 194-201, 2022 196 figure 2. existing topography 2.2. analysis method rainfall data based on high rainfall analysis is based on design rainfall data in the pancasari village area, gitgit sub-district. furthermore, infiltration analysis can model seepage into the soil due to the influence of rain using a numerical method, the seep/w program from geostudio. the data analysis is shown in the table below. the results of collecting journal documents obtained are as follows: in table 1. the number representing heavy rainfall with a 2-year return period in sukasada (gitgit) district is 87.33 mm/day, respectively table 1. hyetograph of rain depth 87,325 mm/day td it ittd ∆p pt hytograph (hours) (hours) (hours) (hours) (hours) (%) (%) (mm) 1 0-1 30.27 30.27 30.27 55.03 6.75 5.89 2 1-2 19.07 38.14 7.87 14.30 10.03 8.76 3 2-3 14.55 43.66 5.52 10.03 55.03 48.06 4 3-4 12.01 48.06 4.39 7.99 14.30 12.49 5 4-5 10.35 51.77 3.71 6.75 7.99 6.98 6 5-6 9.17 55.01 3.24 5.90 5.90 5.15 amount 55.01 100 100 87.33 table 2. changes in the value of the soil shear strength parameter based on the suction value research sites sr suction pers. ho and freudlund (%) (kpa) c(kpa) 𝝋𝒃(°) pancasari village district. gitgit 70 100 48,120 23,668 80 80 45,909 27,485 90 50 34,354 31,303 93 40 23,354 32.448 96 30 10,932 33,593 98 5 7,707 34,357 civil and environmental science journal vol. 05, no. 02, pp. 194-201, 2022 197 in table 2. changes in pore water pressure result in changes to the parameters of the shear strength of the soil, namely the cohesion value and the angle of internal friction of the soil. ho and fredlund equations are used to predict the soil shear strength parameter value based on the suction value. the data was obtained from the standard penetration test (spt) from the bali province p2jn core team. the topography of the existing land area was relatively precipitous, with variations in soil elevation of more than 10.0 m, and located in a complex road segment. nevertheless, the results of soil investigations carried out from 2 drill points as deep as 30 meters show a fairly similar soil stratification; the topsoil layer is dominated by clay soil, followed by a silty-sand layer, and then overwhelmed by siltclay soil. overall, the soil stratification at the project site can be simplified. the results of field and laboratory soil tests are shown in the table, which shows soil parameters such as cohesion (c), soil volume weight (γ), saturated or dry, and soil shear angle (φ). soil parameter data by correlating the value of n-spt [8] with the correlation table je bowles, 1984 using linear interpolation. table 3. correlation results of n-spt value against the value of soil volume weight (γ) depth soil classification n-spt y1 y2 x1 x2 u.weight u.weight average kn/m3 kn/cm3 0 m 1 m blackish silty sand mixed with gravel 2.00 0 4 14 18 16.00 0.00001600 1 m 8 m yellowish brown loamy silt mixed with loose sand and gravel 2.00 0 4 14 18 16.00 0.00001600 8 m 10 m dark brown silty sand 21.00 11 30 14 18 16.11 0.00001611 10 m 24 m brownish silty sand 21.00 11 30 14 18 16.11 0.00001611 24m -30m fine to medium brown sandy loam 31.00 31 50 16 20 16.00 0.00001600 table 4. correlation results of n-spt value against cohesion value (c) depth soil classification n-spt y1 y2 x1 x2 cu c' c' average tons/m2 tons/m2 kn/cm2 0 m 1 m blackish silty sand mixed with gravel 2.00 0 2.5 0 1.25 1.00 0.67 0.000654 1 m 8 m yellowish brown loamy silt mixed with loose sand and gravel 2.00 0 2.5 0 1.25 1.00 0.67 0.000654 8 m 10 m dark brown silty sand 21.00 20 40 10 20 10.50 7.00 0.006865 10 m 24 m brownish silty sand 21.00 20 40 10 20 10.50 7.00 0.006865 24m -30m fine to medium brown sandy loam 31.00 20 40 10 20 15.50 10.33 0.010134 slope stability analysis in this study used the slope/w program with the limit plastic equilibrium method. in the slope/w program there are several boundary balancing methods, one of which is used in this study is the bishop, ordinary, janbu and morgenstern-price methods. [5] . civil and environmental science journal vol. 05, no. 02, pp. 194-201, 2022 198 table 5. correlation results of n-spt value against soil shear angle value (φ) depth soil classification c' y1 y2 x1 x2 sliding angle kn/m2 ø 0 m 1 m blackish silty sand mixed with gravel 6.54 5 10 10 20 13.08 1 m 8 m yellowish brown loamy silt mixed with loose sand and gravel 6.54 5 10 10 20 13.08 8 m 10 m dark brown silty sand 68.65 50 100 25 30 26.86 10 m 24 m brownish silty sand 68.65 50 100 25 30 26.86 24m -30m fine to medium brown sandy loam 101.34 50 100 25 30 30.13 the equations for in-ground water flow used in the seep/w software for the complete analysis of two-dimensional transients and seepage are: q y h k x h k t h m wwy y w wx x w ww +        −   +        −   =    2 (1) where mw2 = slope soil-water relationship characteristic curves; w = unit weight of water; hw = total head; kwx = soil permeability coefficient of water in the x-direction; kwy = soil permeability coefficient of water in the y-direction; q = flux boundary; t = time. the seep/w analysis uses two important soil parameters: the soil permeability coefficient function and the soil water characteristic curve (swcc). the shear strength equation for unsaturated soils required for slope stability analysis, slope/w, can be designated as equation 2. this equation is a composite of the shear strength of the soil as a result of negative pore water pressure and unsaturated soil suction. the morgenstern-price method was used to obtain the factor of safety (sf) in the slope/w analysis. ( ) ( ) bwawn uuuc  tan'tan' −+−+= (2) where = unsaturated soil shear strength; c' = cohesion; n = total normal stress; ua = pore air pressure; = internal friction angle; uw = pore-water pressure; (ua – uw) = matrix suction. soil physical parameters were adjusted to the data from geometric measurements in the terunyan village area using numerical analysis. rock lithology analysis was carried out based on interpreting the slope outcrops around the study area. slope stability analysis using morgenstern-price with pore-water pressure conditions obtained from seep/w analysis. furthermore, the safety factor analysis uses slope/w to get the value of the safety factor. three execution programs slope/w, namely: define to define the slope model, solve to analyze the calculation, and contour to display the results. this result is expected to solve the problem geotechnical problems related to soil or slope stability 3. results and discussion a slope is said to be stable if the slope does not experience movement and does not have the potential to experience movement, that is, if the magnitude of the component of the resisting force on the slope is greater than the component of the driving force of the slope with the condition that sf> 1.0 then the slope is said to be stable. 3.1. existing slope stability analysis the analysis of the existing slope stability, in this case, was carried out under two different conditions when the slope conditions were normal and when the conditions were moderate rain in the area, the civil and environmental science journal vol. 05, no. 02, pp. 194-201, 2022 199 analysis in this case was carried out using the slope/w and seep/w program with the bishop method, the load on the slope it is assumed that with a pavement load of 22 kn/m2, the design rainfall data in the pancasari village area, gitgit hyetograph sub-district, rain depth is 87,325 mm/day. in figure 3. after analyzing the existing slope with the slope/w and seep/w program with the bishop method, when normal conditions are obtained, the safety factor is 0,939 with a landslide volume of 27.962 m3, while in figure 4. shows the analysis results on the existing slope when the rainy conditions are getting a safety factor of 0,236 with a landslide volume of 30.928 m3. figure 3. results of existing slope analysis in normal conditions 3.2. slope stability analysis after steel pile sheet reinforcement slope stability analysis after reinforcement of steel sheet piles in this case was carried out under two different conditions when the slope conditions were normal and during conditions of moderate rain in the area, the analysis, in this case, was carried out using the slope/w and seep/w program with the bishop method. it is because the load on the slopes is assumed to be a pavement load of 22 kn/m2. design rainfall data in the pancasari village area, sukasada hyetograph sub-district, rain depth is 87,325 mm/day. with planned slope reinforcement using sheet pile type pu 6 size 600 x 226 x 7.5 mm with bj.33 quality, the shear bearing capacity of steel sheet pile material is obtained from vn = 11,64 kn, with a sheet pile shear reduction factor of 1,5 obtained from sni 8460:2017 geotechnical planning requirements, page 179 of 303. figure 4. results of existing slope analysis in moderate rain conditions figure 5 shows after analyzing the existing slope with steel sheet pile reinforcement using the slope/w and seep/w program with the bishop method, when normal conditions are obtained, the safety factor is 1,674 with a landslide volume of 10.874 m3, while in figure 6. shows the results analysis on existing slopes with steel sheet pile reinforcement during moderate rain conditions obtained a safety factor of 1,131 with avalanche volume of 10,874 m3. civil and environmental science journal vol. 05, no. 02, pp. 194-201, 2022 200 figure 5. results of existing slope analysis under normal conditions with steel pile sheet reinforcement figure 6. existing slope analysis results in moderate rain conditions with steel pile sheet reinforcement 4. conclusion based on the planning of retaining walls on slopes that have the potential for landslides on the singaraja city boundary, mengwitani km 37+900 right, as described above, it can be concluded as follows: the results of the analysis of the stability of the existing slope using the geostudio program with the slope/w and seep/w analysis system using the bishop method , the value of the safety factor of the existing slope when there is no rain is 0,939, while the value of the safety factor of the existing slope at the time of moderate rain is for 6 hours that is equal to 0,236. existing slopes that have a safety factor value of less than 1 are declared unsafe/unstable, so it is necessary to repair or strengthen the slopes. the value of the safety factor after strengthening the steel sheet pile under normal conditions is 1,674, while the value of the safety factor after strengthening the steel sheet pile during 6 hours of moderate rain is 1,131. so it can be concluded that steel sheet pile reinforcement is effective for slope reinforcement at the research site because the safety factor increases and is greater than 1, the slope is categorized as safe/stable. civil and environmental science journal vol. 05, no. 02, pp. 194-201, 2022 201 references [1] i. n. sinarta and i. w. ariyana basoka, "safety factor analysis of landslides hazard as a result of rain condition infiltration on buyan-beratan ancient mountain safety factor analysis of landslides hazard as a result of rain condition infiltration on buyan-beratan ancient mountain," j. phys. conf. ser., vol. 1402, no. 2, 2019, doi: 10.1088/1742-6596/1402/2/022002. [2] i. n. sinarta, "the threat level of soil movement in volcanic rocks in bali based on a comprehensive geotechnical approach," gadjah mada university yogyakarta, 2018. [3] i. g. tejakusuma, p. teknologi, s. lahan, w. dan, and m. bencana, "soil water content as landslide trigger at girimekar village bandung west java province landwater content triggers landslide girimekar village bandung regency, west java province," j. science and technology. indones., vol. 15, no. 1, pp. 34–41, 2013. [4] i. n. sinarta, a. rifa'i, t. f. fathani, and w. wilopo, "spatial analysis of safety factors due to rain infiltration in the buyan-beratan ancient mountains," int. rev. civ. eng., vol. 11, no. 2, pp. 90–97, mar. 2020, doi: 10.15866/irece. v11i2.17668. [5] i. n. sinarta, "negative pore stress as a parameter of soil mechanics on unsaturated soil slope stability," paduraksa, vol. 5, pp. 31–42, 2016. [6] d. safrina, m. sungkar, and r. p. munirwan, "slope stability analysis with bishop method and sheet pile reinforcement," j. civ. eng. student, vol. 2, no. 3, pp. 309–315, 2020. [7] geo-slope international, "seepage modeling with seep/w 2007," geostudio help., no. february, p. 307, 2010. [8] k. p. acharya, n. p. bhandary, r. k. dahal, and r. yatabe, "seepage and slope stability modelling of rainfall-induced slope failures in topographic hollows," geomatics, nat. hazards risk, vol. 7, no. 2, pp. 721–746, 2016, doi: 10.1080/19475705.2014.954150. [9] h. darjanto, h. farichah, and r. lumintang, "slope stability analysis and alternatives to handling cladding case study of ir. h. nursyirwan ismail road section, samarinda city," j. apl. tech. civil, vol. 19, no. 3, p. 215, 2021, doi: 10.12962/j2579-891x.v19i3.8495. [10] e. b. p. hendra sugih arjaya and m. i. ir siti hardiyati sp1.mt, ir indrastono da, "strengthening the slopes at the sutt sta 19 +255 toll road semarang – solo section tinalun – lemah ireng," pp. 1–13. [11] j. bowles, physical and geotechnical properties of soil, 2nd ed. chicago: mcgraw-hill company, 1984. open access proceedings journal of physics: conference series civil and environmental science journal vol. ii, no. 02, pp. 095-104, 2019 95 integrated urban drainage management for flood inundation controlling in sidokare area at sidoarjo regency evi nur cahya1, dani eko guntoro2, donny harisuseno1 1 water resources engineering department, universitas brawijaya, malang, indonesia 2 department of public work sidoarjo regency, indonesia evi_nc@ub.ac.id received 25-07-2019; revised 18-09-2019; accepted 2-09-2019 abstract. flood and inundation had become a serious problem in sidoarjo regency annually. this study aimed to apply integrated urban drainage management for flood inundation controlling at sidokare region in sidoarjo regency. this integrated drainage management consisted of retarding pond, drainage channel redesign, and pump utilization. the study region was divided into sidokare pump station, sepande, and diponegoro street catchment area. rainfall intensity during historical floods was analysed using mononobe formula and log pearson type iii method was used to analyze design rainfall. from the result of the analysis, it was found that the historical floods in study region caused by rainfall with return period of 1.01 years, with rainfall intensity of 17.55 mm/hour. it was also found that by implementing this integrated urban drainage management at sidokare region, flood could be reduced up to 100%. for sidokare pump station catchment area, the inundation management was conducted by using combination of storage pool, existing drainage channel, and the existing flood pump. for sepande catchment area, it was managed to use the combination of storage pool and the existing drainage channel. meanwhile, diponegoro street catchment area was solved by utilizing new flood pump combining with new tertiary channel and existing drainage channel. keywords: flood, inundation, flood reduction, urban drainage, integrated drainage management. 1. introduction the problem of drainage system management has became an important issue in urban areas, especially in rainy season. urban drainage system are critical and needed complex infrastructures in cities landscape [1]. base on some researchs, the city growth caused climate change, like increases in heavy rainfalls, and increase flood risk [2], especially in urban areas. changes in land use occupation, together with vegetation removal lead to greater run-off volumes flowing faster. floods and drainage concerns are related to city development [3]. it is also important for existing levees, dams, etc. to increase current watershed capacities to mitigate impacts of the floods [4]. the rapid development of urban area, resulting in the transfer of land from the temporary storage, turned into a residential area, thus contradicting the concept of sustainable development. the impact further reduces the ability of flood control facilities and infrastructure in the urban area to dry and drain water into the sea. an integrated drainage management may be the form of problem solving, and mailto:evi_nc@ub.ac.id civil and environmental science journal vol. ii, no. 02, pp. 095-104, 2019 96 development, which will affect other interests. one form of integrated drainage management in urban areas is through the creation of a storage pool, both retention, detention and a longitudinal channel. the storage pool can provide considerable benefits, because it can reduce the amount of flow discharge (run off) in the channel. it also can be a community recreation when the surrounding is arranged into a garden. it can even improve the ground water content of a region, as well as an integrated water conservation and flood control effort. problems that exist in sidoarjo regency, especially the area of sidokare is flood inundation incident that occurs almost every year in the rainy season. the floods have resulted in hundreds of homes, schools and office buildings flooded by 50 cm. inundation occurs when rainfall exceeds 100 mm/day with a duration of six hours of rain. from the existing problems, it is necessary to evaluate the condition of the catchment area in the study area, in an effort to handle the inundation in the existing area of drainage infrastructure. by analyzing the historical flood events, an integrated form of drainage management suitable for the study location is expected to be found. this study aims to determine the occurrence of historical flood and the impact of flood volume increase on the water level in afvoer sidokare. it also meant to propose the appropriate form of integrated urban drainage management, and the magnitude of flood reduction, in the sidokare area. 2. material and methods in the completion of this study, it required supporting data, as primary and secondary data, which includes rainfall data, existing drainage data channel, flow direction data, existing pump station data and drainage outlet, land use data, inundation data, and population data. stages of analysis are started by determining the catchment area (ca) of the study location. the drainage network and the catchment area of sidokare area is shown in fig. 1. calculation of the mean of area rainfall by thiessen polygon method is needed to determine the effect of certain rain stations, to the extent of the affected area. it is analyzed from rainfall data from 1995-2014 (20 years). the rainfall design is calculated using log pearson type iii method [5]. this method can be used on all data distribution without having to meet the requirements of skewness and kurtosis coefficient. the intensity of rain in urban areas can be calculated by the mononobe formula [6]. the approximate number of return period years of the design is based on the volume of floods divided by the length of the flood inundation that occurs. the rainfall discharge for urban drainage is calculated using the modified rational formula. the discharge of dirty water or disposal of the population will be considered to calculate the total debit or flood discharge plan. the capacity of the existing channel, including the main drain, is analyzed to be checked with flood discharge plan. according to these parameters, integrated handling plan for each catchment area will be proposed to solve flood inundated in the study area. 3. result and discussion the sidokare area as presented in figure 1, is divided into three catchment areas, namely catchment area of sepande (western part), catchment area of sidokare pump station (center) and catchment area of diponegoro street (the eastern part). all three catchment area outlets are flowing into afvoer sidokare as main drain. 3.1 rainfall analysis twenty-years of rainfall data, from 1995-2014, is used in hydrological analysis. however, in order to obtain reliable rainfall data, several tests are required, including consistency test with double mass curve analysis and statistical periodic series analysis, which include trend-free test, stationary test and persistence test. in the analysis, data of four rain stations around the area are used, namely durungbedug rainstation, sidoarjo rainstation, sumput rainstation and kludan rainstation. the result of the analysis shown that civil and environmental science journal vol. ii, no. 02, pp. 095-104, 2019 97 these four groups of data are consistent. meanwhile from the periodic statistical test, it showed that in the test of the absence of trend, the four stations data are independent. in the stationary test, it shown that the four stations data are stable. as for persistence test, data from three stations are random, while data from one station is not random. from these data analysis, it was found that from three stations is acceptable and reliable enough to be used in subsequent hydrological analysis. figure 1. drainage network of sidokare area figure 2. coverage of sidoarjo rain station (162) in the calculation of the rainfall area mean using the thiessen polygon method, it is found that the study area is influenced entirely by sidoarjo rain station (162), as can be seen in figure 2, where scale study area civil and environmental science journal vol. ii, no. 02, pp. 095-104, 2019 98 the rainfall data of sidoarjo rain station in the previous test has been qualified and reliable enough to be used in hydrological analysis. therefore, the other rain stations (153, 163 and 186) can be eliminated for hydrological analysis. 3.2 rainfall design using log pearson method type iii in flood engineering and water management, there is a need to determine the flood peak flow for a given t-year return period, the annual maximum of river flow quantile xt (design flood) [7]. in this study, drainage planning in residential areas in urban areas used return period of 1.01 years, 2 years and 5 years. the results of the calculation of rainfall design (xt) with log pearson method type iii for a specific return period (tr) can be seen in table 1. 3.3 rainfall intensity the calculation of the intensity of rainfall aims to see the height of the historical rain that caused the flood. according to observations, related institution and historical rainforest information, it was found that the duration of rain in the study site, the average occurred within six hours. the results of rainfall intensity calculation with the mononobe formula will be compared with the calculation of historical flood inundation to obtain the historical flood return period. table 2 shows the results of rainfall intensity analysis based on the return period. table 1. rainfall design for specific return periods table 2. rainfall intensity based on return period 3.4 return period the observation of the length of the inundation that occurred based on historical floods was for two days (2x24 hours) with the assumption that water was not increased nor decreased. from analysis of the inundation volume using contour or topographic maps, it obtained volume of 419,530.30 m3 for an inundation height of 0.50 m from the soil surface. with the flooded area of 64,068.92 m2 (29.61% of the area of sidokare), the accommodated volume is obtained as 124,213.59 m3. from this volume then reduced with the capacity of the existing drainage channel of 8427.23 m3 and the result of pumping analysis at the time of flood incident of 100,800.00 m3. the flood inundation volume is obtained as 14,986.36 m3. flood inundation volume then converted into rainfall intensity, the obtained value of historical rainfall intensity is 17.55 mm/hour. the value is close to the rainfall intensity value of the 1.01 years return period plan (16.503 mm/hour). the return period value used in the analysis are 1.01 years, 2 years and 5 years 3.5 rainfall discharge with the area of sidokare of 89.57 ha or 0.8957 km2, rainfall discharge for each catchment area for civil and environmental science journal vol. ii, no. 02, pp. 095-104, 2019 99 drainage channel is calculated using rational modification equation by entering the storage capacity coefficient (cs) as the number of corrections to the number of building blocks in urban areas. furthermore, discharge due to rain is added to the discharge of dirty water or discharge of the population, resulting in total discharge or flood discharge plan. 3.6 existing drainage channel capacity the comparison resulting in existing drainage capacity to the flood discharge plan for return period of 1.01, 2 and 5 years can be seen in table 3. table 3. comparison of existing channel capacity to flood discharge plan in specific return period 3.6.1 sepande catchment area the existing drainage channel is quite safe for flood discharge plan with the return period 1.01 years, since it is able to accommodate the entire flood discharge plan. in the other hand, for flood discharge plan with the return period 2 years and 5 years, there is one channel that is overflowing. 3.6.2 sidokare pump station catchment areare for flood discharge plan with the return period 1.01, 2 and 5 years, there are four, six and seven civil and environmental science journal vol. ii, no. 02, pp. 095-104, 2019 100 overflowing channels, respectively. 3.6.3 diponegoro street catchment area for flood discharge plan with the return period 1.01 years return period, there are three overflowing channels, while for flood discharge plan with the return period 2 and 5 years, there are four overflowing channels. 3.7 integrated urban drainage management plan integrated urban drainage management for controlling the flood inundation in sidokare district of sidoarjo regency, defined as the effort of handling inundation on urban drainage network which is done in an integrated with certain combination pattern. the proposed handling is meant to water conservation in the rainy and dry seasons. due to limited available land, widen the channel will be an appropriate choice. while deepen the channel will not be the option because the groundwater level in the rainy season is only one meter from the surface of the soil. to meet these requirements, the combination of proposed handling for the sidokare area is optimizing existing drainage channels, set up new water gate operation pattern, planning of the pool as a means of conservation of water, create new tertiary channels, operate existing flood pumps, add new flood pump, if necessary. 3.7.1 sepande catchment area the flood inundation in this catchment area is proposed to be adjusted to its condition. because it has a wide area for detention pond, the purpose suitable handling will be optimizing existing drainage channels combine with storage pools. 3.7.2 sidokare pump station catchment area in this catchment area, the handling is planned using a combination of existing drainage channels, existing storage ponds and existing flood pumps. 3.7.3 diponegoro street catchment area the proposed handling for this area is planned using a combination of existing drainage channels, new tertiary channels and new flood pumps. 3.8 storage pool the pool in this study is a detention pond during the rainy season. while in the dry season serves as a storage pool, by retaining the remaining water of the rainy season in it. so that it can be functioned as a place of fishing, parks, urban forest and water and air conservation functions. 3.8.1 storage pool at sepande catchment area the location of the plan for this storage pool is shown in figure 1 with a notation letter a which is an empty unproductive field. it is planned with the length of 100 m, and width of 60 m and height 2.5 m (measured from ground level, with 0.5 m as freeboard), with slope 1:1. this pool has a maximum capacity of 16,614 m3. its function is to serve sepande catchment area and able to accommodate the water volume of sk.1 for 2 years and 5 years return period. the purpose of making this storage pool is to reduce the secondary channel load of sk.3. the filling processes the pool in the rainy season is done by using one inlet pump unit with a capacity of 0.5 m3/sec/unit. the pump is operated when it rains heavily and the water level in the drainage channel begins to reach the freeboard. for the 1.01 years return period, this storage pool has not been functional yet, since all existing drainage channels are still able to accommodate flood discharge plans. while on the 2-year and 5-year return period, the filling process of this pool for water volume of 9,517.66 m3 and 11,401.56 m3 takes 5.29 hours and 6.33 hours, respectively. civil and environmental science journal vol. ii, no. 02, pp. 095-104, 2019 101 during the dry season, the function of the storage pool is directed to ponds for water conservation, fishing ponds and recreation for the community. there for, the rainwater that descends at the end of the rainy season should be stored entirely in the pond, and not disposed to afvoer sidokare. 3.8.2 storage pool at sidokare pump station catchment area the location of the plan for this storage pool is shown in figure 1 with a notation letter b which is also an empty field. it is planned with the length of 100 m, and width of 60 m and height 3.5 m (measured from ground level, with 0.5 m as freeboard), with slope 1:1. this pool has a maximum capacity of 21,568 m3. its function is to serve sidokare pump station catchment area and able to accommodate the water volume of ska.1, ska.2, ska. 3a and ska.4, for return period of 1.01 years (1,244.64 m3), 2 years (10,448.47 m3) and 5 years (18,742.54 m3). the filling process of the storage pool in the rainy season is carried out using two inlet pump units with a capacity of 0.5 m3/sec/unit. the pump is operated when it rains heavily and the water level in the drainage channel begins to reach the freeboard. water is pumped into the pool, is the excess water of the ska.1, ska.2, ska.3a and ska.4 channels, so it is not overflow into the streets and residential area. for a 1.01 year return period, the duration of water filling into the pool is 0.35 hours. while for the 2 and 5 years return period is 2.90 hours and 5.21 hours, respectively. it is optimal with historical flood inundation conditions caused by the duration of six hours of rain. water discharges from the catchment pool in the rainy season should be done periodically, so that the pool is not overcapacity and can accommodate water from the next rainfall. water discharges can be performed when flood in afvoer sidokare have fallen below the existing drainage outlet base elevation (+3.0 m asl), and water conditions in ska.3b and ska.3c secondary channels are empty. during the dry season, the function of the storage pool is directed to ponds for water conservation, fishing ponds and recreation for the community. therefore, the rain water that descends at the end of the rainy season should be stored entirely in the pond, and not disposed to sidokare. 3.9 new tertiary channel the making of new tertiary channels is set in the middle of the street along the way of diponegoro street. this arrangement is due to no free land at diponegoro street catchment area that allows for temporary storage ponds as an attempt to reduce flood discharge plans. the alternative to choose is to create a new tertiary channel in the middle of a residential road that serves to reduce load of existing channels and as a means of water conservation. new tertiary channels to be created are new tertiary 1 (stb.1) and new tertiary 2 (stb.2) channel. stb.1 serves to reduce the tertiary channel of ski.2. with stb.1, the excess discharge from ski.2 can be accommodated entirely by stb.1. while stb.2 serves to reduce the load of ski.4a channel. with stb.2, the excess discharge from ski.4a can be accommodated entirely by stb.2. for a 1.01 years return period, ski.2 secondary channel discharge load of 0.4244 m3/sec and overflowing because it exceeds the existing channel capacity. and it becomes reduced due to excess water of 0.0944 m3/sec into stb.1, so the ski .2 is safe from overcapacity. while on the secondary channel ski.4a, the discharge load is reduced from 0.8910 m3/sec to 0.7128 m3/sec, because the excess water of 0.7001 m3/sec goes into stb.2, so ski.4a is safe from overcapacity. likewise, the reduction of discharge load on the 2 years and 5 years return period. 3.10 flood pump a pumping station is important facility to control flood of an urban drainage system to drain urban rainwater to water bodies such as rivers [8]. the flood pump as in figure 1, is the last alternative selected in controlling flood inundation through water conservation efforts. the operation of the flood pump aims to dispose of the excess debit to the afvoer, if the drainage channel and the storage pool are not able to accommodate the flood discharge plan, as it has exceeded the existing planning. civil and environmental science journal vol. ii, no. 02, pp. 095-104, 2019 102 at sepande catchment area, the flood discharge plan can be handled with existing drainage channel and storage polls, so it no longer requires flood pump. while at the outlet of sidokare pump station catchment area, there are two existing flood pump units with each pump capacity is 0.35 m3/sec. functions can be optimized by referring to the existing standard operation procedure (sop). in flood discharge conditions the 1.01-year return period, the excess water to be pumped is 0.2561 m3/sec, derived from ska.7, ska.3b and ska.3c. this pumping aims to empty the secondary channels of ska.3b and ska.3c, so that when the water in the afvoer begins to recede, the storage pool in the sidokare pump station catchment area can be immediately channeled out to afvoer sidokare through ska.3b and ska.3c channels. for 6 hours rain duration, the time required to pump excess water with the existing pump is 2.19 hours. as for the 2 and 5 years return period, excess water to be pumped is 0.3953 m3/sec and 0.5102 m3/sec. with a duration of six hours of rain, the pumping time required with the existing pump for 3.39 hours and 4.37 hours. at diponegoro street catchment area outlet at existing condition there is only a sluice gate to be a regulatory building in the event of a flood. it is proposed to install flood pump with a capacity of 0.5 m3/sec per unit to pump water from diponegoro street catchment area to afvoer sidokare. in flood conditions of 1.01 year return period, the excess water to be pumped by 0.0023 m3/sec. for six hour rain duration, the time required to pump the excess water with a new flood pump with a capacity of 0.5 m3/sec is 0.03 hours. while, for the 2 and 5 years return period, the excess water to be pumped is 0.1061 m3/sec and 0.2683 m3/sec. with a duration of six hours of rain, it takes time to pump with a new flood pump for 1.27 hours and 3.22 hours. 3.11 afvoer sidokare capacity receiving additional flood volume based on the analysis, afvoer sidokare which has parapet (additional river bank embankment) as high as 0.50 m and the average width between the left and right parapet is 23,17 m, along 4,767.55 m from the study location to afvoer sidokare sub-basin, able to receive an additional flood volume of 55,235.47 m3. addition of flood volume from sidokare area to afvoer sidokare on 1.01 year return period is 5,579.52 m3, with afvoer water level increased 0.05 m from maximum water level. while at 2 years return period there is addition of height of water level in afvoer as high as 0.10 m, with additional flood volume equal to 10,831.92 m3. at 5 years return period, it increases the height of the water level in the afvoer as high as 0.15 m, with additional flood volume of 16,814.88 m3. 3.12 flood reduction the amount of flood reduction after handling in an integrated manner can be seen in table 4. table 4. flood reduction after handling in an integrated manner no. flood controlling system flood discharge plan (m3/s) flood reduction (%) 1.01 years 2 years 5 years 1.01 years 2 years 5 years a sepande ca 1.2631 1.3273 1.5901 1 exsisting drainage channel 1.2631 0.8867 1.0622 100 66.80 66.80 2 storage pool 0 0.4406 0.5278 0 33.20 33.20 flood reduction (%) 100 100 100 b sidokare ps ca 2.2815 2.9647 3.5516 1 exsisting drainage channel 1.9678 2.0856 2.1737 86.25 70.35 61.20 2 storage pool 0.0576 0.4837 0.8677 2.53 16.32 24.43 3 exsisting flood pump 0.2561 0.4406 0.5102 11.22 13.34 14.37 civil and environmental science journal vol. ii, no. 02, pp. 095-104, 2019 103 flood reduction (%) c diponegoro st. c 2.8853 2.7395 4.4799 1 exsisting drainage channel 2.6105 2.9710 3.2117 90.48 79.45 71.69 2 new tersiery channel 1 0.0944 0.2224 0.3318 3.27 5.95 7.41 3 new tersiery channel 2 0.1782 0.4400 0.6682 6.17 11.77 14.92 4 new flood pump 0.0023 0.1061 0.2683 0.08 2.84 5.99 flood reduction (%) 100 100 100 3.12.1 sepande catchment area the flood discharge of 1.01 year return period at sepande catchment area of 1.2631 m3/sec, can be handled entirely by using existing drainage channels (100%). while the flood discharge plan of 2-year return period (1.3273 m3/sec), should be accommodated in storage pool of 0.4406 m3/sec (33.20%) and the rest of 0.8867 m3/sec (66.80 %) flowed through existing drainage channels. similarly, for flood discharge 5-year return period (1.5901 m3/sec) should be accommodated in storage pool of 0.5278 m3/sec (33.20%), and the remaining 1.0622 m3/sec (66.80%) is channeled through existing drainage channels. so the combination of both will be able to handle the overall flood inundation (100%). 3.12.2 sidokare pump station catchment area flood discharge of 1.01 year return period at sidokare pump station catchment area is 2.2815 m3/sec, require combination of integrated handling using existing drainage channel 1,9678 m3/sec (86,25%), storage pool 0.0576 m3/sec (2.53%) and the existing flood pump of 0.2561 m3/sec (11.22%). while for flood discharge 2-year return period (2.9647 m3/sec), using existing drainage channel of 2.0856 m3/sec (70.35%), storage pool of 0.4837 m3/sec (16.32%) and existing flood pumps of 0.3953 m3/sec (13.34%). for flood discharge the 5 year return period (3.5516 m3/sec), using the existing drainage channel of 2.1737 m3/sec (61.20%), storage pool of 0.8677 m3/sec (24.43%) and the existing flood pump is 0.5102 m3/sec (14.37%). so, the combination of all three systems will be able to handle the flood inundation (100%). 3.12.3 diponegoro street catchment area flood discharge plan 1.01 year return period at diponegoro street catchment area of 2.8853 m3/sec, requires a combination of integrated handling using existing drainage channels of 2.6105 m3/sec (90.48%), new tertiary channe1 1 of 0.0944 m3/sec (3.27%), new tertiary 2 channels of 0.1782 m3/sec (6.17%) and new flood pumps of 0.0023 m3/sec (0.08%). meanwhile, for flood discharge the 2-year return period (3.7395 m3/sec), requires a combination of integrated handling using existing drainage channels of 2.9710 m3/sec (79.45%), new tertiary channel 1 of 0.2224 m3/sec (5.95%), new tertiary 2 channels of 0.4400 m3/sec (11.77%) and new flood pumps of 0.1061 m3/sec (2.84%). at the flood discharge the 5-year return period (4.4799 m3/sec), requires a combination of integrated handling using existing drainage channels of 3.2117 m3/sec (71.69%), new tertiary 1 tier 1 0.3318 m3/sec (7.41%), new tertiary 2 for 0.6682 m3/sec (14.92%) and new flood pumps of 0.2683 m3/sec (5.99%). so the combination of the four will be able to handle the puddle as a whole (100%). 4. conclusions from the results of the analysis, it can be concluded as follows: a. historical flood inundation in the area of sidokare caused by rainfall with an intensity value of 17.55 mm/hour. the value is close to the calculation of the rainfall intensity of the 1.01 year return period, which is equal to 16,503 mm/hour. b. with the parapet (additional river bank embankment) as high as 0.5 m and the integrated handling using existing drainage channels, storage pool and new tertiary channels, the civil and environmental science journal vol. ii, no. 02, pp. 095-104, 2019 104 remaining flood volume to be pumped from the sidokare area to afvoer sidokare is still in safe condition. the afvour water level at return period of 1.01 years, 2 years and 5 years, increased 0.05 m, 0.10 m and 0.15 m respectively from the maximum water level (the peak of the old embankment). c. the integrated urban drainage management system for the sidokare area is adjusted to the conditions of each catchment area. for sepande catchment area using existing drainage channels and storage pools. sidokare pump station catchment area using a combination of existing drainage channels, existing storage pool and existing flood pumps. and diponegoro street catchment area using a combination of existing drainage channels, new tertiary channels, and new flood pumps. d. reduction of flood in sidokare area after handling in an integrated manner has a success rate of up to 100%. so with the handling of the integrated management system, the problem of inundation in the study location is expected to be immediately addressed. references [1] x. dong, h. guo and s. zeng, enhancing future resilience in urban drainage system: green versus grey infrastructure, water research, vol. 124, pp.280-289 [2] semadeni davies, annette, hernebring, c., svensson g. and gustafon, 2008, the impacts of climate change and urbanisation on drainage in helsingborg, sweden: combined sewer system, journal of hydrology 350(1-2). p.114-125. [3] marcelo games miguez, aline pires verol and paulo roberto ferreira carneiro (2012). suistainable drainage systems: an integrated approach, combining hydraulic engineering design, urban land control and river revitalisation aspect, drainage systems, prof muhammad salik javaid (ed), isbn: 978-953-51-0243-4, intech [4] a javaheri and m. babbar-sebbens, on comparison of peak flow reductions, flood inundation maps, and velocity maps in evaluating effects of restored wetlands on channel flooding, ecological engineering, vol 73, december 2014, pages 132-145 [5] chow, v.t., d.r. maidment, d. r.,mays, l.w. 1988. applied hydrology, mcgraw-hill book co., singapore [6] witold g. strupczewskia, krzysztof kochaneka and ewabogdanowiczb, historical floods in flood frequency analysisi; is this game worth the candle, journal of hydrology, vol. 554, november 2017, pp. 800-816. [7] h. n phine and m. a. hira, log pearson type-3 distribution: parameter estimation, journal of hydrology, vol. 64, issues 1-4, july 1983, pp. 25-37 [8] j. yazdi, h. s. choi and j. h. kim, a, methodology for optimal operation of pumping stations in urban drainage systems, journal of hydro-environment research, vol. 11, june 2016, pp.101112. open access proceedings journal of physics: conference series civil and environmental science journal vol. 5, no. 1, pp. 096-106, 2022 96 mapping of tourism potential and assessment of development stages in sidomulyo tourism village, batu city widya rizka augusty1*, aris subagiyo1, wawargita permata wijayanti1, gunawan prayitno1 1 department of urban and regional planning, brawijaya university, malang, 65145, indonesia *riaugust@student.ub.ac.id received 20-04-2022; accepted 29-04-2022 abstract. the batu city government is currently developing a tourism village. the policy was adopted in the strategic plan of the batu city tourism office in the field of tourism product development by increasing the number of tourism villages that have the adequate infrastructure; one of them is sidomulyo village. the success of developing a tourism village can be seen in the benefits of managing a tourism village to improve the welfare of the local community. tourism villages can develop optimally if the area's potential can be identified properly. therefore, this research was conducted to identify the tourism potential of sidomulyo village and assess the stages of its development as a tourism village in batu city. the sample used in the study is the stakeholders selected by considering the sample are individuals who understand the actual conditions of the development of sidomulyo village as a tourism village and are involved in the management of tourism villages. the scoring analysis technique is used to assess the development stages with a variable in the form of a tourism village aspect. the research shows that sidomulyo tourism village is in an advanced stage based on the highest score for the attraction aspect, while the lowest for the information aspect and institutional aspect. keywords: tourism-village-aspect, development-stage, sidomulyo-tourism-village. 1. introduction the development of tourist villages today is becoming a central issue in strengthening the role of villages. the strategy to increase the potential and capacity of local resources is through the development of tourism villages [1,2]. a village can be developed into a tourism village by assessing its tourism potential [3]. not all villages can be developed into a tourism villages. the development of a tourism village must at least be equipped with aspects that refer to the tourism component. the development of tourism villages consists of attractions, amenities, accessibility, information, promotion, community readiness, and institutions [4,5]. the tourism potential of sidomulyo village makes this village encouraged by the batu city government to be developed as a tourism village [6]. sidomulyo village is a center for producing ornamental plants in batu city. as many as 60% of the people of sidomulyo village are ornamental plant farmers. almost all residents' houses sell various kinds of ornamental plants. a thousand types of flowers and ornamental plants are cultivated by residents spread over three hamlets, namely tinjumoyo, sukorembug, and tonggolari [7]. the civil and environmental science journal vol. 5, no. 1, pp. 096-106, 2022 97 agricultural production of ornamental plants owned by sidomulyo village has been going on for decades. there is potential for local wisdom, namely written batik managed directly by the batik agroindustry community in sidomulyo village. sidomulyo village has also been equipped with tourism supporting facilities such as rest areas, homestays, restaurants, food stalls, flower stalls, flower markets, gift shops, toilets, and worship facilities. the location of sidomulyo village is quite strategic, which is on the main road to selecta tourism objects, which allows tourists to stop by to visit the village [6]. in line with this potential, in 2020, sidomulyo village will be designated as a flower tourism village through the development of tourist destinations for education on flower farming. tourism development in sidomulyo village is still facing obstacles due to the weak management and management of tourism in sidomulyo village and its governance as a choice of destinations and tour packages in batu city [8]. the limitations of tourism management in sidomulyo village cause several problems. most ornamental plant product marketing still relies on flower traders who come to intermediaries without any tourism product innovations. in addition, local wisdom in the form of batik sidomulyo has not been produced and marketed optimally. whereas in the principle of developing a tourism village not only pay attention to the physical aspects of the product such as attractions, amenities, accessibility, but it is also important to pay attention to aspects of human resources, management and institutions, promotion and marketing, and investment [9]. the development of a tourism village is an effort to reduce the outflow of profits out of the region. the community can enjoy the benefits. so, the economic exchange that occurs benefits the development of the community and the region itself [10,11]. the success of developing a tourism village can be seen in how much benefit the management of a tourism village has on improving the welfare of local communities [12, 13]. tourism villages can develop optimally if the area's potential can be identified properly. the tourism problem in sidomulyo village encourages the need for planning a tourism village by utilizing its potential so that it can be profitable for the surrounding community. therefore, this research was conducted to identify the potential and development stages of sidomulyo village. 2. methods this research is included in quantitative research. the quantitative approach in this study is intended to answer the research objectives, namely assessing the development stages of the sidomulyo tourism village using scoring analysis. determination of the tourism village development stages is used to maximize the local potential of sidomulyo village. this research is located in sidomulyo village, batu district, batu city, east java (figure 2). sidomulyo village has an area of 270.82 ha, with 68% of the area being used as agricultural land for ornamental plants [14] (figure 1). the selection of the research location was based on the determination of sidomulyo village as a new tourism village in batu city based on the batu city regional spatial plan 2010-2030 [15]. figure 1. ornamental plant farm. civil and environmental science journal vol. 5, no. 1, pp. 096-106, 2022 98 figure 2. the location of sidomulyo tourism village. 2.1. sampling technique the sample used in this study is key stakeholders. the stakeholders were selected with consideration of the sample being individuals who understand and understand the actual conditions of the development of sidomulyo village as a tourism village and are involved in the management of tourism villages. the stakeholders in this research include the head of sidomulyo village, head of mulyo joyo village owned enterprises, head of sidomulyo village tourism management, chair of the sidomulyo village tourism awareness group, chair of the sidomulyo village community family welfare organization, chair of sidomulyo village community empowerment institute, chair of the sidomulyo village farmers group association, and chair of the sidomulyo village agroindustry of hand-drawn batik in sidomulyo village. 2.2. analysis technique the analytical technique used in this research is scoring analysis. scoring analysis is used in the assessment process of each indicator in the tourism village aspect using a modified likert scale with a score level of four [3]. the stages carried out in the scoring analysis to determine the development stages of sidomulyo village as a tourism village are as follows: 1. define key stakeholders 2. perform key stakeholder assessment calculations using a likert scale 3. recapitulating and classifying the assessment results of each key stakeholder the first step is to recapitulate the assessment results from each key stakeholder in one table, then classify each aspect of the tourism village into four classifications starting from pioneering, developing, advanced, to independent (table 1). next, the average calculation of the overall assessment of the tourism village aspect is carried out. the results of these calculations are interpreted as the development stages of sidomulyo village as a tourism village (table 2). civil and environmental science journal vol. 5, no. 1, pp. 096-106, 2022 99 tourism village aspect score = ⅀ tourism village aspect indicator 𝑛 (1) n = the number of data table 1. the classification of tourism village aspect scoring tourism village aspect (attractions, amenities, accessibility, information, promotion, community readiness, and institutions) score classification 1,00 – 1,75 pioneering 1,76 – 2,50 developing 2,51 – 3,25 advanced 3,26 – 4,00 independent development stages of tourism village = ⅀ tourism village aspect score 𝑛 (2) n = the number of data table 2. development stages of tourism village score development stages of tourism village 1,00 – 1,75 pioneering 1,76 – 2,50 developing 2,51 – 3,25 advanced 3,26 – 4,00 independent 3. result and discussion 3.1. result the initial determination of sidomulyo village as a tourist village is because of the potential in the form of ornamental plant production that has been going on for decades. this opportunity makes the batu city government synergize with the sidomulyo village government to realize the idea of developing existing agriculture by making sidomulyo village a flower tourism village with several tourist points about the education on ornamental plants farming. tourism development in sidomulyo village does not stop at the advantages of the ornamental plant agricultural sector. exploration of other potentials continues to be carried out, such as local wisdom in the form of hand-drawn batik and adventure tourism which can be developed to become an attraction for tourists (figure 3). the completeness of tourism supporting facilities such as rest areas, homestays, restaurants, stalls, flower stalls, flower markets, gift shops, toilets, and worship facilities continues to be pursued as a form of support for the development of the sidomulyo tourism village (figure 4). tourists can easily access sidomulyo village or its attractions (figure 5). tourist information (figure 6) and tourism promotions have also begun to be carried out offline and online to market and introduce sidomulyo tourism village to tourists. efforts to involve the community in tourism activities continue to be carried out in the development of the sidomulyo tourism village, considering that the community is one of the important aspects of tourism management. in addition, a village management agency has also been formed to optimize tourism management in sidomulyo village. finally, in 2017 sidomulyo village began to dare to declare itself as a flower tourism village, until in 2020, it was designated as a tourism village by the batu city tourism office. civil and environmental science journal vol. 5, no. 1, pp. 096-106, 2022 100 figure 3. the distribution of tourist attractions in sidomulyo village, (1) education of ornamental plant cultivation; (2) atv tour; (3) sekar mulyo flower market; (4) rose and chrysanthemum cultivation/picking tour; (5) gelora bunga mall; (6) education of batik making; (7) education of creative kokedama; (8) off-road jeep tour; and (9) apple picking tour. figure 4. the distribution of tourism amenities in sidomulyo village, (1) roudhlotul jannah mosque; (2) djoeragan cafe; (3) pring pethuk restaurant; (4) gazebo; (5) homestay; (6) rest area; (7) sidomulyo village tourism market; (8) temporary shelter; and (9) florist. figure 5. the accessibility of sidomulyo tourism village, (1) the road to the gelora bunga mall; (2) the road to the ornamental plant farming area; (3) the first gate of sidomulyo tourism village, the road to sidomulyo tourism village; (4) directional signs to tourist attractions; (5) the main road of sidomulyo tourism village; and (6) the second gate of sidomulyo tourism village. figure 6. the distribution of tourism information center in sidomulyo village (1) additional tourism information center (new) and (2) existing tourist information center. civil and environmental science journal vol. 5, no. 1, pp. 096-106, 2022 101 3.2. discussion table 3. attractions aspects assessment no. indicators stakeholders (x) mean (�̅� = ⅀𝒙𝒏/𝟖) 1 2 3 4 5 6 7 8 1 physical landscape/scenery 3 4 3 4 4 4 4 4 3,75 2 environmental hygiene 2 2 2 3 3 2 2 2 2,25 3 uniqueness of the resource (typical) 4 4 4 3 4 4 4 4 3,88 4 efforts to preserve the environment 4 4 4 3 3 2 3 3 3,25 5 diversity of tourist activities 4 3 4 4 3 3 4 3 3,50 final score (tourism village aspect score=�̅�/𝟓) 3,33 classification independent 3.2.1 attractions aspects assessment in table 3, the tourist attractions owned by sidomulyo village are included in the independent category with a final score of 3.33. this category includes the highest stage and has the potential to support the development of tourism villages. the tourist attraction of sidomulyo village is at an independent stage based on the potential of the village's physical landscape consisting of views of mountains and beautiful rural areas and community tips to be responsible for maintaining cleanliness and environmental sustainability. sidomulyo village also has ornamental plant agricultural resources, which are the village's identity, which is marked with the highest score of 3.88, namely as one of the largest ornamental plant producers in indonesia, both on a local, national level, and international scale. in addition, sidomulyo village is equipped with various tourist activities such as education of ornamental plant cultivation, education of planting techniques with moss growing media (creative kokedama), education of batik making, cultivation/picking tours of roses and chrysanthemums, apple and orange picking tours, flower markets and flower malls, off-road jeeps, and atvs. however, the final score of the attraction aspect has a value that is close to the minimum limit of the independent stage, with a difference of 0.07. this value needs to be reconsidered because obstacles are still found in the cleanliness of the village environment, marked by the lowest score of 2.25, which is due to the habit of people still littering in river bodies around settlements. this condition can certainly damage the image of sidomulyo village as a tourism village in batu city. the management of tourist attractions has also been constrained due to the development of the covid-19 pandemic. efforts to develop tourist attractions need to adapt to these limitations to optimize the benefits of the sidomulyo tourism village's tourism potential for the community's welfare. table 4. amenities aspects assessment no. indicators stakeholders (x) mean (�̅� = ⅀𝒙𝒏/𝟖) 1 2 3 4 5 6 7 8 1 availability of rest areas 4 3 3 3 3 4 4 3 3,38 2 homestay availability 4 3 4 3 3 3 3 3 3,25 3 availability of huts/gazebo 3 3 3 4 3 3 3 3 3,13 4 availability of places of worship 4 3 4 4 4 4 4 4 3,88 5 availability of restaurants 4 3 4 4 4 4 4 4 3,88 6 availability of shopping facilities 3 3 4 4 3 3 3 3 3,25 7 temporary shelter availability 2 2 3 1 2 2 2 2 2,00 final score (tourism village aspect score=�̅�/𝟕) 3,25 classification advanced civil and environmental science journal vol. 5, no. 1, pp. 096-106, 2022 102 3.2.2 amenities aspects assessment in table 4, it is shown that the tourist amenities owned by sidomulyo village are included in the advanced category with a final score of 3.25. this category is a potential stage in supporting the development of a tourism village, which is one level below the independent stage. sidomulyo village tourism facilities are at an advanced stage based on the completeness of sidomulyo village tourism support facilities, starting from rest areas, homestays, gazebos, places of worship, restaurants/shopping facilities, and temporary shelter. the highest score for the indicator of the availability of places of worship and restaurants is 3.88. facilities for places of worship are scattered throughout sidomulyo village, including around tourist attractions, with complete and well-maintained worship supporting facilities, making it easier for tourists to worship. tourists can easily find restaurants with various food menu choices, including traditional menus, which are commonly used to entertain tourists who come to sidomulyo village. however, some obstacles were still found in the temporary shelter availability indicator, marked with the lowest score of 2.00 due to insufficient temporary shelter capacity and no waste recycling efforts carried out by the local community. in addition, the condition of the gazebo is poorly maintained and has changed its function as a place for building materials so that it cannot be used properly. efforts to maintain and improve the quality of tourist amenities need to be considered so that tourists are more comfortable and stay longer in the sidomulyo tourism village. table 5. accessibility aspect assessment no. indicators stakeholders (x) mean (�̅� = ⅀𝒙𝒏/𝟖) 1 2 3 4 5 6 7 8 1 condition of the road to the village 4 4 4 4 4 3 4 4 3,88 2 condition of the road to the tourist attraction 3 3 3 3 3 3 3 3 3,00 3 availability of public transportation 2 2 2 2 2 2 2 2 2,00 4 availability of directional signs to the village 3 2 2 2 3 2 2 2 2,25 5 availability of directional signs to the tourist attraction 3 2 1 1 1 2 2 2 1,75 final score (tourism village aspect score=�̅�/𝟓) 2,58 classification advanced 3.2.3 accessibility aspect assessment in table 5, it is shown that the tourist accessibility of sidomulyo village is included in the advanced category with a final score of 2.58. this category is a potential stage in supporting the development of a tourism village, which is one level below the independent stage. the tourist accessibility of sidomulyo village is at an advanced stage based on the condition of the road to the village that is easily accessible by tourists, marked with the highest score of 3.88. the road is considered very good because it is wide and has minimal damage, making it easier for tourists to pass. the road to the tourist attraction of sidomulyo village is also in good condition and easy to pass even though it has a relatively narrow size. however, the final score for the accessibility aspect has a value close to the minimum advanced stage, with a difference of 0.07. this value needs to be reconsidered that obstacles are still found in the accessibility of sidomulyo village tourism, especially on the indicator of the availability of directional signs to the tourist attraction such as flower markets and flower malls marked with the lowest score of 1.75. directional signs to the tourist attraction of sidomulyo village are commonly found in other areas without being equipped with special designs that describe the value of the village locality and are difficult for tourists to see. the availability of public transportation facilities to tourism villages is also very limited due to people who prefer to use private vehicles. increasing the accessibility of tourism villages needs to be done to increase tourist visits to sidomulyo tourism village. civil and environmental science journal vol. 5, no. 1, pp. 096-106, 2022 103 table 6. information aspect assessment no. indicator stakeholders (x) mean (�̅� = ⅀𝒙𝒏/𝟖) 1 2 3 4 5 6 7 8 1 availability of tourist information center 2 2 2 2 2 2 2 2 2,00 final score (tourism village aspect score=�̅�/𝟏) 2,00 classification developing 3.2.4 information aspect assessment in table 6, it is shown that the tourist information owned by sidomulyo village is included in the developing category with a final score of 2.00. this category is a stage that is quite potential in supporting the development of a tourism village, which is two levels below the independent stage. tourism information in sidomulyo village is in the developing stage based on the condition of the tourist information center that has not operated optimally, marked with a score of 2.00. the sidomulyo village tourist information center is only active in serving tourists at certain times, such as during official visits or comparative studies with the government and schools. the media used to convey information is still limited to the form of banners showing the types of tourist attractions. generally, the tourism village manager will act as a tour guide by conveying offline information to tourists. the tourist information center has not gone through the digitization process using special applications such as electronic tickets or big data for sidomulyo village tourism. the development of tourist information in sidomulyo village needs to be improved to make it easier for tourists to determine travel plans. table 7. promotion aspect assessment no. indicator stakeholders (x) mean (�̅� = ⅀𝒙𝒏/𝟖) 1 2 3 4 5 6 7 8 1 availability of promotional media 3 2 3 2 3 3 3 3 2,75 final score (tourism village aspect score=�̅�/𝟏) 2,75 classification advanced 3.2.5 promotion aspect assessment in table 7, it is shown that the tourism promotion owned by sidomulyo village is included in the advanced category with a final score of 2.75. this category is a potential stage in supporting the development of a tourism village, which is one level below the independent stage. sidomulyo village tourism promotion is at an advanced stage based on the efforts made to utilize various marketing media both online in the form of websites and instagram or offline in brochures and banners. sidomulyo village also cooperates with travel agents, namely city travel associations, to market tourism villages to local and national tourists. in addition, the local community contributes to marketing the sidomulyo tourism village by word of mouth to help increase tourist visits to enjoy the village. however, the final score for the promotion aspect has a value close to the minimum advanced stage, with a difference of 0.24. this value needs to be reconsidered that obstacles are still found in the promotion of sidomulyo village tourism, such as not having formed a slogan or tagline that can describe the characteristics of the village and make it easier for tourists to remember experiences when visiting tourist villages. tourist segmentation has also not been formed, resulting in social media, both instagram and websites, in which the intended market share has not been utilized. marketing using social media has not been carried out optimally and continuously, so the images or videos presented are less attractive and less up-to-date. sidomulyo village tourism promotion needs to be improved to attract more tourists to visit the village. civil and environmental science journal vol. 5, no. 1, pp. 096-106, 2022 104 table 8. community readiness aspect assessment no. indicators stakeholders (x) mean (�̅� = ⅀𝒙𝒏/𝟖) 1 2 3 4 5 6 7 8 1 community readiness 3 4 3 3 4 2 3 3 3,13 2 society participation 3 3 3 3 4 3 3 3 3,13 3 community hospitality 3 4 4 3 4 3 3 4 3,50 final score (tourism village aspect score=�̅�/𝟑) 3,25 classification advanced 3.2.6 community readiness aspect assessment in table 8, it is shown that the community readiness of sidomulyo village is included in the advanced category with a final score of 3.25. this category is a potential stage in supporting the development of a tourism village, which is one level below the independent stage. the people's readiness of sidomulyo village is at an advanced stage based on the condition of the people who have a friendly attitude to tourists and are willing to be happy to help the needs of tourists during their visit to the sidomulyo tourism village marked with the highest score of 3.50. the community's response to the development of tourism villages was also considered good, with a score of 3.13 on the indicators of readiness and participation. the community feels that they already know about tourism development in the surrounding environment and are aware of the benefits of tourism. the community's motivation to be actively involved in tourism development is also starting to grow, indicated by the willingness of the community to be involved in the development of tourism accessibility which not only brings benefits to daily life but also makes it easier for tourists to access various tourist attractions in sidomulyo village. the readiness and involvement of the community need to be continuously improved, given the importance of the community's role as the main actor in the development of tourism villages. table 9. institutions aspect assessment no. indicators stakeholders (x) mean (�̅� = ⅀𝒙𝒏/ 𝟖) 1 2 3 4 5 6 7 8 1 availability of tourism management organizations 2 2 2 2 2 2 2 2 2,00 2 availability of tourism village awareness group 2 2 2 2 2 2 2 2 2,00 3 availability of cooperation with outside parties 4 1 3 2 3 2 3 3 2,63 final score (tourism village aspect score=�̅�/𝟑) 2,21 classification developing 3.2.7 institutions aspect assessment in table 9, it is shown that the institutions owned by sidomulyo village are included in the developing category with a final score of 2.21. this category is a stage that is quite potential in supporting the development of a tourism village, which is two levels below the independent stage. the tourism institutions of sidomulyo village are in a developing stage based on the availability of cooperation with outside parties, including the research and community service institute, which from now on is referred to as universitas brawijaya institution of research and community services, batu city tourism office, and bumiaji village and pandanrejo village. the availability of cooperation with external parties is the indicator with the highest score of 2.63. the form of external cooperation with sidomulyo village consists of assistance and knowledge sharing by universitas brawijaya institution of research and community services, assistance and assistance by the batu city tourism office, and revenue sharing from the sale of fruit picking tour tickets in the rest area with the bumiaji village and pandanrejo village which the tourism village manager handles. however, obstacles are still found in the tourism institutions of sidomulyo village, namely the availability of village management institutions and tourism village awareness group that actively serve tourists only at certain times, marked by the civil and environmental science journal vol. 5, no. 1, pp. 096-106, 2022 105 lowest score of both, namely 2.00. the tourism village management agency is active incidentally, especially when sidomulyo village receives a visit from the relevant official or when a government and school comparative study takes place; the tourism village awareness group is also incidentally active when sidomulyo village carries out training or counseling related to tourism. increasing the role and function of the tourism institutions in sidomulyo village needs to be carried out so that the tourism objectives, namely the welfare of the local community, can be achieved. table 10. assessment of tourism village development stages no. tourism village aspect tourism village aspect score tourism village development stages score (�̅� = ⅀tourism village aspect score/𝟕) classification 1 attractions 3,33 2,77 advanced 2 amenities 3,25 3 accessibility 2,58 4 information 2,00 5 promotion 2,75 6 community readiness 3,25 7 institutions 2,21 3.2.8 assessment of tourism village development stages in table 10, it is shown that the development of the sidomulyo tourism village is in an advanced stage, with a final score of 2.77. the highest score for the tourism village aspect is owned by the attraction aspect included in the independent stage category with a final score of 3.33. the lowest score for the tourism village aspect is owned by the information and institutions aspects included in the developing stage category with final scores of 2.00 and 2.21. sidomulyo tourism village is at the stage of advanced development supported by all the potential aspects of the tourism village. however, the final score for the development stage of the sidomulyo tourism village has a value that is close to the minimum advanced stage, with a difference of 0.26. it can be interpreted that several aspects of the development of the sidomulyo tourism village still have obstacles that need to be optimized. improvement efforts need to be continued, especially on aspects of tourism villages that are in the developing stage as well as aspects that have a final score close to the minimum limit of the stages below it, so that the development of sidomulyo tourism village can run optimally and reach the highest stage, namely the independent stage. 4. conclusions the results of the assessment of all key stakeholders on the seven tourism village aspects of sidomulyo village, namely; (1) tourist attractions are included in the independent category with a final score of 3.33; (2) the tourist amenities are included in the advanced category with a final score of 3.25; (3) tourism accessibility is included in the advanced category with a final score of 2.58; (4) tourist information is included in the developing category with a final score of 2.00; (5) tourism promotion is included in the advanced category with a final score of 2.75; (6) the readiness of the is included in the advanced category with a final score of 3.25; and (7) institutions are included in the developing category with a final score of 2.21. the results of the scoring analysis of sidomulyo tourism village development stages show that sidomulyo village is in the position of the advanced stage with a final score of 2.77. the highest score for the tourism village aspect is owned by the attraction aspect included in the independent stage category with a final score of 3.33. the lowest score for the tourism village aspect is owned by the information and institutions aspects included in the developing stage category with final scores of 2.00 and 2.21. improvement efforts need to be carried out, especially on aspects of tourism villages in the developing stage and those approaching the lower limit of the development stage so that the civil and environmental science journal vol. 5, no. 1, pp. 096-106, 2022 106 development of sidomulyo tourism village can run optimally and reach the highest, namely the independent stage. references [1] k. p. linggarjati; g prayitno; a. d. wicaksono, "study of community participation in development of ngadas traditional tourism village," tataloka, pp. 736-745, 2019. [2] n. s. arida; i. a. suryasih; i. g. n. parthama, "model of community empowerment in tourism village development planning in bali," iop conference series: earth and environmental science, pp. 1-7, 2019. [3] g. prayitno, d. dinanti, a. efendi, a. hayat, and p. p. dewi, "international journal of sustainable development and planning social capital of pujon kidul communities in supporting the development of the covid-19 resilience village," vol. 17, no. 1, pp. 251– 257, 2022, doi: https://doi.org/10.18280/ijsdp.170125 [4] n. w. tyas dan m. damayanti, “potensi pengembangan desa kliwonan sebagai desa wisata batik di kabupaten sragen,” journal of regional and rural development planning, pp. 74-89, 2018. [5] a. amir, t. d. sukarno dan f. rahmawati, “identifikasi potensi dan status pengembangan desa wisata di kabupaten lombok tengah, nusa tenggara barat,” jurnal perencanaan pembangunan wilayah dan perdesaan, pp. 84-98, 2020. [6] a. ramadani, “malang raya; kota batu,” 07 maret 2018. [online]. available: https://malangvoice.com/tahun-ini-pemkot-batu-fokus-kembangkan-3-desa-wisata-ini/. [7] p. d. rahma dan r. aldila, “identifikasi potensi & masalah desa sidomulyo sebagai upaya pengembangan desa wisata di kota batu,” jurnal reka buana, pp. 89-97, 2017. [8] s. asmaul, i. a. dewi, s. fajriani dan a. subagiyo, “pengembangan desa wisata bunga sidomulyo berbasis kearifan lokal di kota batu jawa timur,” universitas brawijaya, malang, 2020. [9] a. z. mutaqin, “desa wisata, pariwisata indonesia,” 07 maret 2017. [online]. available: https://wisatahalimun.co.id/pengembangan-desa-wisata. [10] i. k. widnyana, i. p. karunia, and i. p. sujana, “strategy for development of tourist village in bali island”, int. j. res. granthaalayah, pp. 324–330, 2020. [11] i. a. r. s windayani; a. marhaeni, "the effect of tourism village development on community empowerment and welfare in tourism village of panglipuran, bangli district of indonesia," russian journal of agricultural and socio-economic sciences. pp. 257-265, 2019. [12] h. hermawan, “dampak pengembangan desa wisata nglanggeran terhadap ekonomi masyarakat lokal,” jurnal pariwisata, pp. 105-117, 2016. [13] a. t. nugraha, g. prayitno, a. w. hasyim, and f. roziqin, "social capital, collective action, and the development of agritourism for sustainable agriculture in rural indonesia," evergreen, vol. 8, no. 1, pp. 1–12, 2021, doi: 10.5109/4372255 [14] pemerintah desa sidomulyo. profil desa sidomulyo tahun 2020. batu; 2020. [15] badan perencanaan pembangunan, penelitian dan pengembangan daerah. rencana tata ruang wilayah (rtrw) kota batu tahun 2010-2030. batu; 2011. open access proceedings journal of physics: conference series civil and environmental science journal vol. 5, no. 1, pp. 089-095, 2022 89 eccentricity effect on the cyclic response of braced frame typev lilya susanti1,*, ming narto wijaya1 1civil engineering department, universitas brawijaya, malang, 65145, indonesia *lilya_st@ub.ac.id received 18-04-2022; accepted 29-04-2022 abstract. eccentricity on the braced frames can sometimes not be avoided to facilitate some structural considerations, such as openings. v-type braced frames are among the most widely used bracing types because of their satisfying performance. the present study investigated the effect of eccentricity as 15 cm, and 25 cm on the reinforced concrete braced frames of 80 cm x 100 cm in dimension compared to v-type of concentric braced frame (cbf). results indicated that a frame with 15 cm of eccentricity has almost similar stress but higher strain compared to the cbf while the frame with 25 cm of eccentricity resulted in lowest stress but highest strain. as the eccentricity rises, a frame is likely to behave as a moment-resisting frame. link beams are the most critical part of the eccentric braced frame. keywords: cyclic load, eccentric braced frame (ebf), lateral load, strain, stress. 1. introduction lateral load on the structural frames is usually identified as a wind or a seismic load. it acts on the lateral axis, resulting in the flexure mechanism to the columns structure and axial or normal mechanism to the beams structure. structural hysteresis behaviour can be investigated using this loading condition, and even dissipation energy can be identified. the cyclic load application on the frame structure can reduce the axial structural capacity by 50% of the actual capacity even with only one strong cyclic load [1]. there are three types of frame structures that have been widely used worldwide so far. they are moment resisting frame (mrf), concentric braced frame (cbf) and eccentric braced frame (ebf). cbf is the most rigid structure, resulting in small ductility. discussing about lateral load, ductility has an important function. for example, the structures located in severe earthquake zones have to be designed in a fully ductile structure to maintain structural integrity against the external loads. bracing is the most efficient and easiest choice to stiffen the frame. there is an only axial mechanism inside the bracing structure [2]. some bracing types usually used as a stiffener on the frame structures are diagonal, v, inverted-v, k, x, y and many more. diagonal bracing is simple, while x-type results in the heaviest frame structure. cbf sometimes becomes over in structural rigidity, resulting in small ductility. for that reason, using ebf is a wise choice to get the satisfying structural rigidity and the fit ductility to carry the outside loads. ebf also offers flexibility for the frame structures to facilitate some architectural considerations because the bracing positions can be moved at a certain distance, such as placing the doors, windows, civil and environmental science journal vol. 5, no. 1, pp. 089-095, 2022 90 etc. some studies regarding the bracing-frame performance are the experimental study on the diagonal ebf under lateral load by setyowulan, susanti and wijaya [3], link beam on ebf by musmar [4], a comparative analysis of various bracing systems related to the earthquake-resistant design by islam, mehandiratta and yadav [5], the performance of ebf under seismic load by prasad and prasad [6] and also comparison study of bracing configuration on ebf structures by wilson, rafael and lukas [7] and by razak et al. [8]. v-type of ebf structure is one of the most widely chosen structural bracing types other than the diagonal type because of its satisfying performance. vbracing type provides an adequate rigidity compared to diagonal bracing but is not as high as x-type, which can sometimes be over rigid. satisfying structural weight results in a balanced performance, not over rigid but also providing ductility to the frame structure. performance of v-type ebf was investigated by wijaya, susanti and syafirra [9] through the study on the shear stirrup space variation under cyclic load and analytical study on the cyclic response of ebf-v structure bouwkamp, vetr and ghamari [10]. 2. material and methods the present experimental study was conducted at the structure and construction material laboratory of brawijaya university. three total models were investigated, consisting of one cbf and two ebf structures using 15 and 25 cm of eccentricity span. detailed dimensions of the present models are shown in figure 1. the mix design procedure uses the concrete grade k-175 (f'c = 14,525 mpa). to verify the suitability of the concrete grade, the experimental study used three standard concrete cylinders for each model that were compressively tested using compression testing machine to get the actual concrete compressive strength. the present research also conducted a tensile test using universal testing machine to obtain the actual steel grade for the used steel reinforcement. cbf model ebf – 15 cm model ebf – 25 cm model model's cross-section figure 1. detailed dimensions of cbf and ebf models civil and environmental science journal vol. 5, no. 1, pp. 089-095, 2022 91 the cyclic load was set using two load cells on the loading frame, placed at the lateral direction on the top of each left and right column. the bottom beam was set fixedly to the loading frame, so there was no axial and shear displacement on the bottom of both columns. to eliminate the vertical displacement at the top of column structures and the top beam, the present experiment used a steel plate with the steel bars placed between the plate and the top beam, so only lateral displacement exists. figure 2 shows the model's setting on the loading frame. figure 2. model's setting on the loading frame left and right load cells consecutively gave the lateral loads to illustrate the cyclic load. the load increment was gradually increased from 25, 50, 75 and 100% of the maximum load. the maximum load was determined using the previous experimental result of 7000 kg. each load increment was applied five times consecutively from the left and right load cells. the recorded output is the load coming from the load cell, the displacement from lvdt and the strain from the steel and concrete strain gage. two lvdt were used at the same place with the load cell. strain gages were placed at the critical parts of the frame structures. 3. result and discussion compression and tensile tests were conducted for concrete and steel bar samples applied for the mainframe models. the tensile test result showed that the steel bar samples for diameters 4 mm and 6 mm had yield stress of 422,301 mpa and 453,886 mpa while the ultimate strength reached 688,615 mpa 613,041 mpa, respectively. according to the slump test result of the concrete samples, the average slump value was 13,67 cm, which means that the concrete mixture has good workability. finally, the concrete compressive test result found that the average compressive strength of 19,52 mpa goes beyond the designed mixture is 14,525 mpa. figure 3 shows the application of cyclic loading on the frame, while figure 4 shows the load versus displacement history of the present frame models where the blue colour indicates the first phase (25% of the maximum load), orange colour shows the second phase (50% of the maximum load) and green colour indicates the third phase (75% of the maximum load). each phase consists of five times loading steps consecutively from the right, and in figure 4, it can be seen that the cbf model reached the maximum cyclic load (phase 3 – step 2/5250 kg) while ebf – 25 cm resulted in a minimum load (phase 2 – step 2/3500 kg). ebf – 15 cm is on between phase 3 – step 1/5250 kg. the highest displacement was recorded at 15 cm. hence, from the previous explanation, it can be summarized that ebf – 15 cm locking system steel bar locking system steel plate civil and environmental science journal vol. 5, no. 1, pp. 089-095, 2022 92 provides a suitable strength and ductility compared to the cbf model, which is too stiff and ebf – 15 cm, which is too weak. figure 3. cyclic loading test on the loading frame cbf ebf – 15 cm ebf – 25 cm figure 4. load-displacement behaviour compression stress and strain history can be seen in figure 5. the compressive strains were recorded from the strain gage placed inside the bottom of each frame model's right concrete column structure. blue for phase 1, orange for phase 2 and grey colour for phase 3. the strain values shown in the figure have to be multiplied by 10-6. the lowest compressive strain resulted from the cbf model (183 x 10-6) but the highest compressive stress simultaneously (216.337 mpa). ebf – 15 cm showed almost similar performance to cbf (compressive strain as 183 x 10-6 and stress as 216.257 mpa), and ebf – 25 cm resulted in a much higher compressive strain (785 x 10-6) but lowest stress as 144 mpa. from all models' compressive stress and strain history, some deviated strains result due to over high sensitivity of the strain gages. but generally, as an eccentricity increases, the compression strain increases but the stress decreases. civil and environmental science journal vol. 5, no. 1, pp. 089-095, 2022 93 cbf ebf – 15 cm ebf – 25 cm figure 5. compression stress-strain behavior a steel strain gage placed on the steel reinforcement at the bottom of the left column structure from each model was used to record the tensile strain parameter. figure 6 shows the tensile stress versus strain behavior of each frame. the tensile behavior can be seen compared to the compression strain result. the lowest to biggest maximum strains have resulted from cbf (552 x 10-6), ebf – 15 cm (959 x 10-6) and ebf – 25 cm (1130 x 10-6), respectively. it confirms the previous conclusion that the most rigid frame was cbf (tensile stress as 144.18 mpa), then followed by ebf – 15 cm (tensile stress as 216.283 mpa) and ebf – 25 cm (tensile stress as 144.18 mpa). cbf ebf – 15 cm ebf – 25 cm figure 6. tensile stress-strain behavior civil and environmental science journal vol. 5, no. 1, pp. 089-095, 2022 94 cbf, ebf – 15 cm and ebf – 25 cm models have collapsed due to failures in the different locations of the frames. ecf model could reach a higher cyclic load if the bottom beam does not collapse. the bracing and mainframe structure still has a capacity against the load. ebf – 15 cm collapsed on its link beam and column's bottom parts which means that for ebf structures, the link beam is the most critical part. it was proved by ebf – 25 cm model, where the structure was also extremely damaged on its link beam (figure 7). hence, future research should strengthen the bottom columns, beam, and link beam parts. cbf ebf – 15 cm ebf – 25 cm figure 7. frame model's failures 4. conclusions the experimental result indicated that the maximum cyclic load decreased as the eccentricity increased. ebf with an eccentricity of 15 cm showed almost similar strength to cbf. on ebf with the eccentricity of 25 cm, the maximum load decreased by 33% compared to cbf. on the other hand, strain increases as eccentricity increases. for ebf-15 cm and ebf-25 cm, the tensile strain improved by 73% and 100%, respectively, compared to cbf. compressive strain also increases by 10% and 300% for each ebf-15 cm and ebf-25 cm compared to cbf. it proved that as the eccentricity increases, the longer the link beam, the structural stiffness decreases but the ductility increases. civil and environmental science journal vol. 5, no. 1, pp. 089-095, 2022 95 references [1] e. p. popov, introduction to mechanics of solids. 1979. [2] b. s. smith and a. coull, tall building structures:analysis and design. 1991 [3] d. setyowulan, l. susanti, and m. n. wijaya, "study on the behavior of a one way eccentric braced frame under lateral load," asian journal of civil engineering, vol. 21, no. 4, feb. 2020. [4] m. a. musmar, "effect of link on eccentrically braced frames," journal of engineering sciences, vol. 40, no. 1, pp. 035–043, jan. 2020. [5] j. u. islam, m. mehandiratta, and r. yadav, "earthquake resistant design – a comparative analysis of various bracing system with rc-frame," ijedr, vol. 7, no. 3, pp. 079–085, 2019. [6] p. prasad, and b. prasad, "performance behavior of eccentrically braced steel frame under seismic loading," ijitee, vol. 8, no. 9, pp. 1077–1090, jul. 2019. [7] j. w. m. rafael, and a. y. lukas, "comparison study of bracing configuration with shear link in eccentrically braced frame steel structure," journal innovation of civil engineering , vol. 1, no. 1, pp. 007–017, apr. 2020. [8] s. m. razak, t. c. kong, n. z. zainol, a. adnan, and m. azimi, "a review of influence of various types of structural bracing to the structural performance of buildings," cenviron proc., vol. 034, no. 01010, 2017. [9] m. n. wijaya, l. susanti, and s. syafirra, "effect of shear stirrup space on short link beam of eccentric braced frame (ebf) v-type under cyclic loading," gcee proc., vol. 2447, no. 030008, 2021. [10] j. bouwkamp, m. g. vetr, and a. ghamari, "an analytical model for inelastic cyclic response of eccentrically braced frame with vertical shear link (v-ebf)," case studien in structural engineering , vol. 6, pp. 031–044, 2016. open access proceedings journal of physics: conference series civil and environmental science journal vol. i, no. 02, pp. 041-051, 2018 41 north jamrud terminal warehouse performance by the effect of halal logistics issue ita suhermin ingsih1, m. zainul arifin1, achmad wicaksono1 1civil engineering department, engineering faculty, universitas brawijaya, malang, 65145, indonesia hatagoma@gmail.com received 26-06-2018; revised 30-07-2018; accepted 30-08-2018 abstract. the government today, government business entity and mass media in indonesia are starting to pay attention to halal, since the turnover of halal products of the world has reached nearly 2 trillion dollars while indonesia is still larger to be a consumer than a manufacturer. not only foods, consumers in the world today want cosmetics to pharmaceutical products that have been halal certified. in indonesia, problems with the potential of halal market today are still hit on the discourses. indonesia still limited awareness not yet dared to action, whereas in nonmuslim countries themselves many have implemented halal supply chain. the establishment of halal hub port in tanjung priok as the first halal hub port pilot project in indonesia is the forerunner to establish halal hub port in other parts of indonesia. therefore, it is necessary to examine the needs of halal warehouse at tanjung perak port which in fact is also a major port in indonesia and is a distribution door for the central and eastern part of indonesia. the study was conducted on 190 respondents who are stakeholders of tanjung perak port. using the importance performance analysis method, the results of the research produced a quadrant graph where quadrant a is the main priority containing performance of l/u equipment in terminal, performance of l/u workers/operator in terminal, separation of halal and non-halal products in halal warehouse, sorting of halal and non-halal products that have been damaged, cold storage separation between halal and non-halal products, clean and avoid contamination between products, special training for officers in halal warehouse, and hygiene facilities for officers in warehouse/halal warehouse. quadrant b is to maintain the achievement contains 11 items, quadrant c is low priority contains 5 items, and quadrant d is excessive contains 5 items. the existence of 8 items entered in quadrant a, indicating that stakeholders at tanjung perak port are very aware with the potential of halal warehouse. keywords: halal logistic, halal warehouse, importance performance analysis 1. introduction indonesia is a country with the highest halal market potential in the world because the total population of indonesia is 257.9 million and about 85% are muslim, making indonesia has a percentage of muslims about 12.5 percent of the population around the world. but not many industries in the country that glance at business opportunities with this halal standardization. problems in indonesia with the potential of halal market today are still hit on the discourses. indonesia still limited awareness not yet dared to action, whereas in non-muslim countries themselves civil and environmental science journal vol. i, no. 02, pp. 041-051, 2018 42 many have implemented halal supply chain. conditions like this if not addressed wisely of course will make the indonesian nation as a spectator in his own country, especially in the asean economic community competition, which is not only muslim entrepreneurs but already enlivened by the international community who are non-muslim. halal (lawful) and toyyib (clean and not damaged) are very important in islam. the halal concept should not only focus on the ingredients and the processing of the products, but also on all activities from the beginning of the production till the final end to consumers [3, 11]. the halal supply chain concept has been seen as a potential business strategy that would attract a wider market comprises both muslim and non-muslim buying the halal products [8]. moreover, it has influenced other countries including the non-muslim countries to produce more halal producers [6]. the halal supply is a process of business integration and activity from the point of origin to the point of consumption under islamic law known as sharia [6]. the main objective of the halal supply chain is to regulate the halal integrity of a product to dispel doubts by muslim consumers at the point of product consumption. while halal products including: 1) food: which is the main focus of halal industry; 2) halal products and services which include cosmetics, pharmaceuticals, clothing, financial services, and logistics; 3) halal is extending upstream (such as animal feed) and downstream (such as food services) value chains and including logistic. several matters relating to halal logistics are discussed by which are less practical procedures, lack of knowledge and expertise in this field, lack of ict knowledge, lack of staff awareness, higher costs, lack of awareness of halal producers, higher service prices, lack of awareness and commitment of halal retailers, and a lack of consumer awareness of the importance of processes occurring in halal logistics [5]. proper handling and storage activities are the primary key in protecting halal products. if an industrial halal product does not use the halal warehouse, is their product really halal for consumption? at the same time, the halal product industry still claims that their halal products are due to have been labelled with halal logo on their packaging [6]. the implementation of halal logistics is still green field, especially for halal warehouse. not many warehouses ready to implement halal principle in their daily activities, also very less manufacturers and suppliers recognized halal approach as their priorities. the issues identified in this paper will be a threat to the performance of the organization if not properly managed. as a profit-oriented organization, performance normally referred to the cost minimization, profit maximization and customer satisfaction. large expenses spent without proper planning to fulfil halal requirements may lead to a perspective that the implementation of halal warehouse is not cost-effectiveness. management may decide to offer a service at higher price in order to gain more margin. consequently, it will decrease customer satisfaction due to this unreasonable price. worse yet, if consumers have to pay more unjustified price to get halal food. at the end, more manufacturers reluctant to use halal certified warehouse service and falling of interest towards the implementation of halal within warehouse provider are very much expected [8]. the halal supply chain is very important to the consumer. consumers are willing to pay more for halal products that carry the assurance of a halal logistics system [3]. the main principle in halal logistics is the segregation of halal and non-halal goods [6] through the transportation, storage and warehousing, and terminal operations [9]. the establishment of halal hub port in tanjung priok as the first halal hub port pilot project in indonesia is the embryo to establish halal hub port in other parts of indonesia such as tanjung perak surabaya which is the second largest harbor in indonesia after tanjung priok. given its status as a halal hub port (primary port) in indonesia, but with the status of the international port for the southeast asian region, major ports are still singapore port feeders, where these ports supply singapore port. in the port of tanjung perak, there are only 3 terminals that have warehouse facilities namely jamrud terminal, mirah terminal, and kalimas terminal. these warehouses are only a transit point for general cargo goods. also, so far, it started to switch to the containerization model, so that the warehouse function has been much reduced. by using this containerization system, consumers do not have certainty whether the products they use mainly for halal products are not mixed with non-halal products, so it civil and environmental science journal vol. i, no. 02, pp. 041-051, 2018 43 needs further research. in addition, the existing warehouse performance in tanjung perak is considered less than the maximum. shown with an average of level of warehouse usage called shed occupancy ratio (sor) score of 2013-2016 is 32.03% away from the standard 65%. based on the presence of halal logistic & cold storage above, it is expected that the same thing is also applied in surabaya, especially in tanjung perak. to begin with is to know about stakeholder preferences in tanjung perak port regarding the existence of halal logistics warehouse which as one component of halal hub port as well as halal and halal retail transportation. this research held at north jamrud terminal by using importance performance analysis (ipa). 2. material and methods 2.1. location and time of study the study was conducted at jamrud north terminal of tanjung perak port of surabaya, east java, indonesia from march to april 2018. jamrud terminal’s facilities are contains of ocean service, inter island, freight and passenger services such as shown in table 1. the research was carried out until the appropriate samples were obtained for further processing and analysis. implementation of data collection starts from office activity hours (at 08.00 wib) until the end of office activities (at 16.00 wib). with the intent to get data directly with interviews in leisure time that can be spent by respondents in answering questions that exist. table 1. jamrud terminal facilities no item north jamrud terminal south jamrud terminal west jamrud terminal 1 area 90.312 m2 57.912 m2 4.807 m2 2 basin depth -10 mlws -8,0 mlws -8,0 mlws 3 berth length 1.200 m 800 m 210 m 4 warehouse area 4.920 m2 5.040 m2 5 apron width 15 m 20 m 15 m 6 warehouse number 1 unit 1 unit 7 storage yard area 23.744 m2 13.639 m2 8 purpose international general cargo, international dry bulk domestic general cargo, domestic dry bulk international dry bulk domestic and cruise passenger 2.2. collecting data method primary data was collected by using analytical descriptive method, while secondary data were collecting data supported by literature study taken from sources related to this research. 2.3. data analysis method the research was used importance performance analysis called ipa (fig.2) [4]. ipa analysis method used the aid of statistical program by inputting data of average value of scoring performance score of primary warehouse survey results. importance performance analysis (ipa) conceptually is a multi-attribute model. this technique identifies the strengths and weaknesses of market supply by using two criteria namely the relative importance of attributes and consumer satisfaction. civil and environmental science journal vol. i, no. 02, pp. 041-051, 2018 44 start problems and research objectives preliminary survey data collection literature review primary data: interview survey questionnaire survey secondary data: goods traffic data warehouse facilities data data analysis importance performance analysis method (ipa) results & discussions conclusions & recommendations end figure 1. analysis process the application of the ipa technique begins with the identification of the relevant attributes to the observed situation of choice. the list of attributes can be developed by referring to the literature, interviewing, and using managerial judgments. the steps of ipa analysis as follows: 1. calculate the average assessment of the importance and performance of each service product as well as calculate the level of compliance. 𝑋𝑖̅̅̅ = ∑ 𝑋𝑖𝑘𝑖=1 𝑛 (1) 𝑌�̅� = ∑ 𝑌𝑖 𝑘 𝑖=1 𝑛 (2) 𝑇𝑘𝑖 = ∑𝑥𝑖 ∑𝑦𝑖 (3) 2. calculate the average level of importance and satisfaction for the entire product service. civil and environmental science journal vol. i, no. 02, pp. 041-051, 2018 45 𝑋𝑖̿̿̿ = ∑ 𝑋𝑖̅̅ ̅𝑘𝑖=1 𝑛 (4) 𝑌�̿� = ∑ 𝑌𝑖̅̅̅𝑘𝑖=1 𝑛 (5) 3. making ipa position’s diagram. 4. preparation of cartesian ipa diagram. 5. plot the results of the analysis of each variable into the diagram cartesian divided into four quadrants (quadrant i, quadrant ii, quadrant iii, and quadrant iv), as shown in figure 3. • quadrant i: shows the factors or attributes that are considered to affect customer satisfaction, including the elements of services that are considered very important, but the management has not implemented it in accordance with the wishes of customers so disappointing/dissatisfied. • quadrant ii: shows the essential elements of service that have been successfully implemented. for it must be maintained. considered very important and very satisfying. • quadrant iii: shows some of the less important factors affecting the customer. implementation by the company mediocre. considered less important and less satisfactory. • quadrant iv: showing factors that affect customers is less important, but excessive implementation. considered less important but very satisfactory [4]. figure 2. ipa diagram 3. result and discussion in this section will list some of the variables that have been studied, based on predetermined standards. referring to the decision letter of head of port authority office iii tanjung perak no. hh.496/01/17/op.sba.2011 dated march 14, 2011 concerning system and procedure guidance (sispro) services of ship and goods at tanjung perak main port, this research uses land side service aspect as follows: • performance of loading/unloading (l/u) equipment in terminal x1 • performance of loading/unloading workers/operator in terminal x2 • operational supervision at the terminal x3 • fleet carrier (truck/train) x4 civil and environmental science journal vol. i, no. 02, pp. 041-051, 2018 46 • line i and ii warehouse services x5 • service of goods documents. x6 some variables also refer to the previous research [2] are: • location of adjacent warehouse (taken less than 1 x 24 hours) with port. x7 • warehouse operation time following port operational time (24/7) x8 • warehouse facilities and services in line 1 and line 2 are adequate x9 • items embrace fifo system (first in first out) or first come first out x10 • loading time per ritase max 20 minutes x11 • unloading time per item max 20 minutes. x12 • the current fee system x13 while for halal products warehouse utility refers to malaysian standard no. ms 2400-2: 2010, management system requirements for warehousing and related activities, namely: • sorting of goods carried out according to the type of goods x14 • placement of food and beverages in areas appropriate to the species x15 • separation of halal and non-halal products in halal warehouse x16 • sorting of halal and non-halal products that have been damaged x17 • use of frozen food storage (cold storage) x18 • separation of cold storage between halal and non-halal products x19 • free from environmental pollution, flood and pest x20 • free of solid & liquid waste that is difficult to remove x21 • clean and avoid contamination between products x22 • easy to maintain x23 • use of special containers as waste disposal sites & dangerous goods x24 • special location for waste disposal containers & dangerous goods x25 • conducting training for periodical human resource improvement x26 • special training for officers at halal warehouse x27 • routine health inspection for warehouse/halal warehouse x28 • hygiene facilities for officers at halal warehouse/warehouse. x29 to obtain objective research results, survey had been carried out and obtained the results of questionnaires that refer to the method of science with 190 respondents. from the recapitulation data of ipa method questionnaire, it can be obtained cartesian diagram of performance and importance of logistics system at port of tanjung priok surabaya (fig.4). this diagram is divided into 4 sections/quadrants where the axis of the abscissa and ordinate that make up the quadrant is derived from the average value of the aspect as well as the item of the performance level (x) as well as the importance level (y). table 2. mean estimation of performance & importance variables var performance (x) importance (y) quadrant ipa x1 3.37 4.33 quadrant 1 x2 3.33 4.31 quadrant 1 x3 4.26 4.30 quadrant 2 x4 4.19 4.22 quadrant 4 x5 4.14 4.27 quadrant 4 x6 4.06 4.32 quadrant 2 x7 3.85 4.23 quadrant 4 civil and environmental science journal vol. i, no. 02, pp. 041-051, 2018 47 var performance (x) importance (y) quadrant ipa x8 3.83 4.37 quadrant 2 x9 3.91 4.27 quadrant 4 x10 3.92 4.30 quadrant 2 x11 3.46 4.25 quadrant 3 x12 3.37 4.21 quadrant 3 x13 3.73 4.34 quadrant 2 x14 3.61 4.34 quadrant 2 x15 3.87 4.31 quadrant 2 x16 2.08 4.32 quadrant 1 x17 2.04 4.31 quadrant 1 x18 3.76 4.22 quadrant 4 x19 2.82 4.31 quadrant 1 x20 3.63 4.30 quadrant 2 x21 3.65 4.29 quadrant 2 x22 3.47 4.30 quadrant 1 x23 3.27 4.01 quadrant 3 x24 3.59 4.31 quadrant 2 x25 3.63 4.28 quadrant 2 x26 3.47 4.22 quadrant 3 x27 2.85 4.30 quadrant 1 x28 3.15 4.16 quadrant 3 x29 3.21 4.32 quadrant 1 source: data analysis from table 2 can be drawn in the form of graph as in fig.4 where the �̅� axis is performance, and �̅� axis is of importance. the cut line uses the average value of the mean of each axis. • quadrant i (main priority) with high importance but low performance level, contains item number: x1 (performance of l/ul equipment in terminal), x2 (performance of l/u workers/operator in terminal), x16 (separation of halal and non-halal products in halal warehouse), x17 (sorting of halal and non-halal products that have been damaged), x19 (cold storage separation between halal and non-halal products), x22 (clean and avoid contamination between products), x27 (special training for officers in halal warehouse) and x29 (hygiene facilities for officers in warehouse/halal warehouse). • quadrant ii (maintain achievement) with high importance and high performance level, containing item number: x3 (terminal operational supervision), x5 (line service i and ii), x6 (goods document service), x8 (warehouse operation time), x10 (first in first out system for goods), x13 (the current cost system), x14 (the sorting of goods carried out according to the type of goods), x15 (food and beverage placement in an area appropriate to its kind), x20 (free from environmental pollution, floods and pests), x21 (free of hard & liquid waste that is difficult eliminated), x24 (use of special containers as waste disposal sites & dangerous goods), and x25 (locations specific for waste disposal containers & dangerous goods). • quadrant iii (low priority) with low importance and low performance level, contains item number: x11 (loading time per ritase max 20 minutes), x12 (unloading time per item max 20 minutes), x23 (easy to care), x26 (conducting training for the improvement of human resources periodically), x28 (health check routine for warehouse/halal warehouse) civil and environmental science journal vol. i, no. 02, pp. 041-051, 2018 48 • quadrant iv (excessive) with low importance but high performance, contains item number x4 (carrier fleet), x5 (line i and ii warehouse services), x7 (location of adjacent warehouse (less than 1 x 24 hours) by port, x9 (warehouse facilities and services in line 1 and line 2 are adequate), and x18 (use of frozen food storage (cold storage). figure 3. cartesian diagram of importance & performance from fig.4, it can be obtained 8 variables that enter in quadrant i, which are variable x1, x2, x16, x17, x19, x22, x27 and x29. those variables required special attention, in accordance with the method used, that quadrant i is "concentrate here". • x1 (performance of l/ul equipment in terminal). jamrud terminal has facilities and equipment some of which are: general forklift hmc scales hopper grab based on sispro at tanjung perak main port, the standard of loading and unloading of noncontainer goods is 50 ton/gang/hour. but in main value from 2013 to 2016 was 108,74 t/g/h, far from the specified standard. this indicates that jamrud terminal required additional equipment which are forklift, digital scales and well-trained l/u workers civil and environmental science journal vol. i, no. 02, pp. 041-051, 2018 49 the decreasing performance of b/m equipment in this terminal is due to the increasing number of incoming and outgoing general cargo in jamrud terminal. fluctuations in the amount of general goods cargo flow can be seen in figure 5. figure 4. the amount of general cargo flow in the jamrud terminal • x2 (performance of l/u workers/operator in terminal). jamrud terminal currently has a tkbm number of about 1600 people. the number is spread into several gangs, where 1 gang consists of 12 people. however, the obstacle here is that not all existing tkbm are well trained in loading and unloading activities. this constraint causes the loading and unloading time of the required goods is longer, thus affecting the dwelling time of goods at the port. • x16 (separation of halal and non-halal products in halal warehouse). jamrud terminal has not done separation activities between halal and non-halal products. this can cause doubt to the consumer of halal products, due to there is concern about mixing between the two products mentioned above without the knowledge of the owner and the recipient of the goods. • x17 (sorting of halal and non-halal products that have been damaged). as well as the sorting of halal and non-halal products that are damaged, it is still done for non-halal products. it is expected that in the future it will be done for halal products with different places. • x19 (cold storage separation between halal and non-halal products). jamrud terminal has not provided warehouse available cold storage in it. it was because the type of general cargo that entered was still raw materials or dry bulk such as soybeans, flour, and rice. while, for liquid bulk transported by truck directly from the carrier vessel. this also affects the low warehouse usage performance level of only 32.03% which is still far from the standard that is 65% • x22 (clean and avoid contamination between products). hygiene and contamination between products is particularly preferred in the accumulation of goods at the north jamrud terminal warehouse. this is done with the use of pedestrian markers and vak markers that serve as the boundary area between products, so expect no contamination between products. • x27 (special training for officers in halal warehouse). the respondents said that it is important to conduct training to halal warehouse officers. this is done for halal warehouse officers understand how to treat halal products according to islamic sharia so that halal products are not only halal but also toyyib. training is expected to be held periodically. civil and environmental science journal vol. i, no. 02, pp. 041-051, 2018 50 • x29 (hygiene facilities for officers in warehouse/halal warehouse). hygiene facilities are limited only to toilets. this is because the available warehouse is still a general warehouse, not yet a special warehouse such as halal products warehouse. if there is a special warehouse for halal products, then the existing warehouse staff should be well trained on how to treat halal products so as not to be contaminated with non-halal products. in the second quadrant contains variables that are have a good performance considered the respondents opinion, and respondents expect that the performance each variable are could be improved. operational supervision at the terminal, service of goods documents, warehouse operation time following port operational time, items embrace fifo system (first in first out) or first come first out, the current fee system, sorting of goods carried out according to the type of goods, placement of food and beverages in areas appropriate to the species, free from environmental pollution, flood and pest, free of solid & liquid waste that is difficult to remove, use of special containers as waste disposal sites & dangerous goods, and special location for waste disposal containers & dangerous goods, respondents assume during this performance variable is good. this is because what happened so far for general cargo materials such as food and beverages, the goods are shipped with containers. the respondents assume for the safety and hygiene of the product, or contamination between the products have obtained guarantee. however, this assurance is still an opinion, not a systemized guarantee. in the third quadrant shows that loading and unloading time per ritase max 20 minutes, warehouse that easy to maintain, conducting training for periodical human resource improvement, and routine health inspection for warehouse/halal warehouse has a low priority. loading and unloading (l/u) times can be accelerated if existing l/u equipment and workers can work optimally. the lack of fast loading time may be due to less loading or unloading equipment or existing equipment is still under maintenance. it indicates that the existing condition, the above variables are rarely done, so the respondent's expectation to increase the performance of the variable is very low. while in the fourth quadrant, some variables are considered excessive in the implementation or exceed the expectations of respondents, namely the provision of goods transporters i.e. truck. this is understandable, because service providers are racing with dwelling time suggested by the port operator that is 2 days. so, the provision of a fleet of freight carriers is reproduced for truck loosing activities so that the goods did not stop at the port for long periods. the location of adjacent warehouses facilitates service providers to unload their goods. the use of cold storage had been done on several warehouse service providers who special serve frozen food products. as well as for the procurement of training for warehouse staff who have periodically been implemented. 4. conclusions the results of the above research can be concluded that the performance of l/u equipment needs to be increased with the addition of loading and unloading equipment that is considered necessary forklift and digital scales. as well as the placement of well-trained l/u workers so that the time for loading and unloading can be accelerated from existing time that was above 30 minutes to one hour could be reduced to 20 minutes. the need for separation halal and non-halal products, impacts on separation of cold storage between halal products and non-halal products, the respondents still consider halal products are still limited to frozen foods such as meat. avoiding contamination and provision of hygiene facilities are expected to be improved in performance, especially for halal products that requires separate training so that halal products do not experience errors in the treatment. references [1] anonim. 2004. malaysian standard 1500:2004, halal food-production, preparation, handling and storage-general guidelines (first revision), department of standards malaysia. [2] chandra a. 2014. warehouse performance measurement using the balanced scorecard method – case studi at pt. gms jakarta. metris journal, 15 (2014): 105 – 110. [3] jaafar, h.s., n. faisol, a.r. rahman and a. muhammad, 2014. halal logistic vs halal suply chain: a preliminary insight. in the proceedings of the 2014 international halal conference, civil and environmental science journal vol. i, no. 02, pp. 041-051, 2018 51 pp: xxx. [4] j. supranto, 2006, measuring costumer satisfaction level: to increase market share, jakarta, rineka cipta. [5] karia, n., m.h.a.h. , a., n., m., & s, k. (2015). assessing halal logistics competence: an islamic-based and resource-based view. in the proceedings of the 2015 international conference on industrial engineering and operations management, 1-6. [6] ngah, a. h., zainuddin, y., & ramayah, t. 2017. modelling of halal warehouse adoption using partial least squares (pls). research gate, 2-3 (71-72). [7] omar, e. n. & jaafar, h. s. (2011). halal supply chain in the food industry a conceptual model. in business, engineering and industrial applications (isbeia), 2011 ieee symposium. [8] shadan, h., arshad, h., n. 2016. issues in halalan-toyyiban warehouse implementation. journal of applied environmental and biological sciences, 6(9s) 1-7. [9] talib, z., s. zailani and y. zainuddin, 2010. conceptualizations on the dimensions for halal orientation for food manufacturers: a study in the context of malaysia. pakistan journal of social sciences, 7 (2): 5661. [10] tan, m.i.i., r.n. razali and m.i. desa, 2012. factors influencing ict adoption in halal transportations: a case study of malaysian halal logistics service providers. international journal of computer science issues, 9 (1): 62-71. [11] zailani, s., z. arrifin, n.a. wahid, r. othman and y. fernando, 2010. halal traceability and halal tracking systems in strengthening halal food supply chain for food industry in malaysia (a review). journal of food technology, 8 (3): 74-81. civil and environmental science journal vol. ii, no. 02, pp. 128-134, 2019 128 calibration of surface runoff parameters with the hydrologic tank model using recursive digital filter and master recession curve n suryoputro1, suhardjono2, w soetopo2, e suhartanto2 1department of civil engineering, universitas negeri malang, malang, 65145, indonesia 2water resources engineering department, universitas brawijaya, malang, 65145, indonesia nugrohosuryoputro@gmail.com received 16-08-2019; revised 31-08-2019; accepted 28-09-2019 abstract. there are two basic methods to calibrate the hydrological model: (1) the trial and error procedure; (2) the automatic calibration. the problem in the calibration method is the determination of the initial value of the parameters. this poses a problem for beginner model users. this paper presents the calibration results of surface runoff parameters in the hydrological tank model using recursive digital filter method and the master recession curve. the results indicate that the recursive digital filter as a surface runoff separation method can be used for the initial approach to calibrate the tank model parameters. keywords: calibration, hydrological tank model, recursive digital filter, master recession curve 1. introduction the calibration of rainfall-runoff model parameters is an interesting issue for hydrological model researchers. some procedures and parameters can be determined directly by analysing physical data or experiments, while other procedures are performed by determining parameters based on changes in physical and climatological factors in a place [1]. the hydrological tank model is a conceptual rainfall-runoff (crr) model developed by sugawara and funiyuki in 1956 [2]. there are three objectives when calibrating the conceptual hydrological model: 1) reproduction of the hydrograph model approaching the observational hydrograph at each point of the river system, 2) the model parameters should function properly, representing the process of natural physical components, 3) there should be a realistic variation of parameter values from one location to another within a river area and with a location across the river in adjacent watershed. there are two basic methods to calibrate the hydrological model [1]. the first method is the trial and error procedure where the experience and knowledge of the model user about the effect of parameter changes on the model outcome are needed to control the model parameters. the second method is automatic calibration. in this method, various computer algorithms are used to achieve the best model output approaching the observed value. civil and environmental science journal vol. ii, no. 02, pp. 128-134, 2019 129 based on the above description, it can be concluded that the model calibration should be performed under several conditions: 1) the initial parameters of the model should be realistic in representing the processes and physical elements of nature, 2) the initial parameter values should be inputted before they are estimated using trial and error or automatically to get the optimal value. to determine a realistic initial value, it takes model users’ experience and knowledge. this poses a problem for beginner model users. in this research, the initial values of the top tank model parameters were determined based on the physical factors of infiltration in a watershed and surface runoff hydrograph. determination of parameters in the top tank with physical approach was as a binding parameter for calibration in the subsequent tanks. the calibration process was done in two stages. the first stage was the calibration of the top tank model only, while the second stage was the calibration by combining all tank models. in this research, the tank models used were in a vertical series arrangement, and there were four of them. to analyse the surface runoff from river hydrograph, two methods of baseflow separation were used in this study and compared with the output of the top tank model. the baseflow separation methods used were: 1) recursive digital filter (rdf) and 2) master recession curve (master rc) [3]. 2. material and methods 2.1. research materials and study area the research was conducted in a sub-watershed of kali bango in malang district; the watershed has an area of 239.71 km2. infiltration measurements were conducted in january to march 2017. the soil samples were analysed at the soil physics laboratory, in the department of soil science, faculty of agriculture, universitas brawijaya. 2.2. model and method description 2.2.1. tank model. the hydrological tank model is a conceptual rainfall-runoff model. this model consists of a series of linear tanks arranged in series or parallel with the outlet holes on the sides and bottom of the tank. the tank model relates the discharge as a function of the influence of precipitation, evaporation, and water storage in the soil at the previous time so that the conceptual model developed is non-linear deterministic. the tank model simulates the watershed by replacing a number of storages with a series of tanks. the tank model parameters are grouped into two types: 1) parameters of outlet coefficient on the sides and the bottom of the tank, 2) parameters soil water storage. the total outflow from the outlet on the (q) side of each tank is considered as the accumulation of water flow from the system in the watershed and the equation is as follows: q(t) = qa1(t) + qa2(t) + qb(t) + qc(t) + qd (1) the equation of water balance in the tank model d/dt h(t)= p(t)q(t) (2) where p denotes the rainfall (mm/day), e denotes the evapotranspiration (mm/day), q is the total runoff (mm/day), h is the height of water storage (mm), and t is the time (day). at the initial time (t=1), the initial height of water storage in tank a (ha (1)), tank b (hb (1)), tank c (hc (1)) and tank d (hd (1)) was determined. for the next step (t+1), the storage in each tank was updated as follows: ha (t+1) = ha (t) + p (t) – qa1 (t) – qa2 (t) – ia (t) (3) hb (t+1) = hb (t) + ia (t) – qb (t) – ib (t) (4) hc (t+1) = hc (t) + ib (t) – qc (t) – ic (t) (5) hd (t+1) = hd (t) + ic (t) – qd (t) (6) civil and environmental science journal vol. ii, no. 02, pp. 128-134, 2019 130 figure 1. schematic plan of tank model 2.2.2. recursive digital filter (rdf) method. many hydrograph separation techniques are used to identify different flow components of total flow. these components are thought to represent the flow systems in a watershed, generally representing surface flow, intermediate flow, and groundwater flow. the use of the digital filter method is more suitable for the separation of the baseflow from the hydrograph of continuous flow over a long period of time. digital filter is a method of hydrograph separation by using a numerical algorithm (digital filter) to separate river hydrograph into high-frequency component (direct run) and low frequency (baseflow). there are currently various models and computer programmes for estimating baseflow, one of which is hydrooffice. it is based on the recursive digital filter (rdf) method, which uses 6 rdf methods (table 1). table 1. rdf filter for analysing baseflow no filter name filter equation reference 1 one parameter algorithm 𝑞𝑏(𝑖) = 𝑘 2 − 𝑘 𝑞𝑏(𝑖−1) + 1 − 𝑘 2 − 𝑘 𝑞(𝑖) (chapman and maxwell, 1996) 2 boughton twoparameter algorithm 𝑞𝑏(𝑖) = 𝑘 1 + 𝑐 . 𝑞𝑏(𝑖−1) + 𝐶 1 + 𝐶 (𝑞(𝑖) + 𝛼𝑞 𝑞(𝑖−1) (boughton,1993; chapman and maxwell, 1996) 3 ihacres threeparameter algorithm 𝑞𝑏(𝑖) = 𝑘 1 + 𝐶 𝑞𝑏(𝑖−1) + 𝐶 1 + 𝐶 (𝑞(𝑖) + 𝛼𝑞 𝑞(𝑖−1)) (jakeman and hombarger, 1993) 4 lyne and hollick algorithm 𝑞𝑓(𝑖) =∝ 𝑞𝑓(𝑖−1) + (𝑞(𝑖) − 𝑞(𝑖−1)) 1+∝ 2 (lyne and hollick, 1979; nathan and mcmahon, 1990) 5 chapman algorithm 𝑞𝑓(𝑖) = 3𝛼 − 1 3 − 𝛼 𝑞𝑓(𝑖−1) + 2 3 − 𝛼 (𝑞(𝑖) − 𝛼𝑞(𝑖−1)) (chapman, 1991) 6 ewma 𝑞𝑏(𝑖) = 𝛼𝑞(𝑖) + (1−∝)𝑞𝑏(𝑖−1) (thularam and ilahee, 2008) source: [3] civil and environmental science journal vol. ii, no. 02, pp. 128-134, 2019 131 description: q(i): the original streamflow on the ith day, qb(i): the original baseflow on the ith day, qb(i-1): the baseflow before the ith day, qf(i): the direct runoff on the ith day, k: the filter parameter given by the recession constant, α: filter parameter, c: a parameter that allows the shape of the separation to be altered, i: daily time interval 2.2.3. master recession curve (master rc) method. malik [4] has developed a technique of hydrograph separation using the interactive solution of several linear and exponential equating members. this method uses the parameters from a set of simple linear and exponential equations. the exponential equation is described by q0 as the initial streamflow and α as the recession coefficient, while the linear equation is described by q0 as the initial discharge and β as the recession coefficient. the main idea of this method is based on a simple understanding of the reality of the hydrological system that the same streamflow should reflect the same water saturation (piezometric) level in the system. the principles of hydrograph separation based on the master recession curve are shown in figure 2, where each streamflow on the right side of the figure corresponds to the value of a particular recession curve. the figure also shows how each streamflow value can be divided into several sub-regimes, depending on its position on the master recession curve. however, understanding of the hydrologic system (the same streamflow reflects the same water saturation or piezometric level in the watershed/aquifer) is a crude simplificati. figure 2. principles of hydrograph separation based on the master rc [3] 3. results and discussion 3.1. results 3.1.1. infiltration coefficient. the coefficient of infiltration was analysed by referring to the largest coefficient of infiltration i.e. forest. based on the slope of land and soil texture, the coefficient value of water flow in the forest was (c) = 0.25, so the infiltration coefficient for the forest was 0.75. the value of infiltration coefficient for other land uses in the watershed was determined by using the comparison of infiltration rate between forest and other land uses and it was multiplied by the forest infiltration coefficient of 0.75 (table 2). civil and environmental science journal vol. ii, no. 02, pp. 128-134, 2019 132 table 2. infiltration coefficients of the tank model in bango watershed land use land area (km2) percentage infiltration coeff. (not units) (not units)housing 44.43 19% 0.12 plantation 124.00 52% 0.28 rice field 49.35 21% 0.01 forest 21.93 9% 0.75 total 239.71 100% the average infiltration coefficient tank model of bango watershed = 0.24 3.1.2. parameter values and calibration of tank model. the calibration of tank model parameters for the bango watershed can be seen in table 3 and figure 3. the optimisation results of the tank model parameters showed the nash-sutcliffe coefficient value of 0.22. table 3. tank model parameters parameter tank-1 tank-2 tank-3 tank-4 hi 0.13 600 1600 2599 hi,2 55.06 0.00 0.00 0.00 αi,2 0.27 0.00 0.00 0.00 hi,1 4.89 15.04 30.02 0.00 αi,1 0.25 0.00 0.00 0.01 bi 0.23 0.11 0.05 0.00 figure 3. results of tank model calibration compared to observation discharge 3.1.3. surface runoff from tank model, rdf, and master rc. the separation of flow by tank model, rdf, and master rc method can be seen in figure 4. table 3. tank model parameters parameter tank-1 tank-2 tank-3 tank-4 hi 0.13 600 1600 2599 hi,2 55.06 0.00 0.00 0.00 αi,2 0.27 0.00 0.00 0.00 hi,1 4.89 15.04 30.02 0.00 αi,1 0.25 0.00 0.00 0.01 bi 0.23 0.11 0.05 0.00 hujan evaporasi hi,2 bi hi,1 hi gw i2 i,1 qi,1,2 rainfall evaporation 0,00 100,00 200,00 300,00 400,00 500,00 600,00 700,00 800,00 900,000,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 jan feb mar apr may jun jul aug sep oct nov dec r ai n fa ll (m m ) d is ch ar ge ( m 3 / se c) 10 daily period rainfall observed simulated civil and environmental science journal vol. ii, no. 02, pp. 128-134, 2019 133 3.2. discussion as shown in figure 5, the difference between the surface runoff resulting from the tank model and that of the master rc analysis is quite far. in other words, the master rc method cannot be used as a preliminary approach to direct runoff parameter calibration in the hydrological tank model. based the comparison between the surface runoff resulting from the tank model and that of the rdf analysis, it can be seen that the difference is quite good (figure 6). in other words, the rdf method can be used as a preliminary approach to direct runoff parameter calibration in the hydrological tank model. the value of runoff coefficient is almost similar to the research conducted by researchers [5, 6, 7], where the runoff coefficient is one-tenth and located between 0.0 1.0. figure 4. surface runoff from tank model, master rc, and rdf figure 5. comparison of tank model discharge to master rc discharge indarto [8] has conducted rdf research in east java, indonesia using 6 rdf methods (oneparameter, boughton two parameters, chapman, ihacres, lyne & hollick, and ewma filters) for the separation of base flow. the study shows that all rdf methods can be used, however, three algorithms (ihacres, lyne & hollick, and ewma filters) perform better than others methods. the result also shows the setting of parameters values from calibrated watershed is transferable to other adjacent watersheds. furthermore, most watersheds on these regions are considered influenced by strong contribution of baseflow both for rainy and dry seasons. 0,00 2,00 4,00 6,00 8,00 10,00 12,00 14,00 16,00 0,00 5,00 10,00 15,00 ta nk m od el d is ch ar ge (m 3 / s) rdf discharge (m3/s) rdf vs tank model civil and environmental science journal vol. ii, no. 02, pp. 128-134, 2019 134 figure 6. comparison of tank model discharge to rdf discharge interpretation of streamflow variations in terms of catchment characteristics has been a major theme in hydrology for many years in order to improve catchment and stream management. two of the main tools for this task are baseflow separation and recession analysis [9, 10, 11, 12]. baseflow separation aims to separate streamflow into two components (quickflow and baseflow), where quickflow is direct runoff following rainfall, and baseflow is delayed streamflow during periods without rain. recession analysis aims to model the decrease of streamflow during rainless periods to extract parameters descriptive of water storage in the catchment. the problem in the recession analysis is the determination of the starting point of recession in hydrograph, this will lead to misleading results. different analyzes of the recession curves also show that the general consensus has not yet been reached on how best to analyze recessions in river flows [13]. the consequences of these problems cause the inaccuracy of flow recession curve results. 4. conclusions from the analysis results of the two methods of surface runoff separation, it can be concluded that the rdf method can be used for the initial approach to calibrate the tank model parameters. this can speed up and simplify the use of the tank model. references [1] anderson e 2002 calibration of conceptual hydrologic models for use in river forecasting (http://www. nws.noaa.gov, visited 17 june 2017) [2] sugawara m and fuyuki m 1956 a method of revision of river discharge by means of a rainfall model (collection of research papers about forecasting hydrologic variables) [3] gregor m and malík p 2012 flowcomp 2.0 user’s manual. hydro office (bratislava) [4] malík p 2010 podzemná voda 16(1) 113-124 [5] ngoci t a, chinh l v, hiramatsu k and harada m 2011 j. fac. agr 56 (2), 335–341 [6] sulianto and setiono e 2012 jurnal teknik industri 13 85–92 [7] surya r a, purwanto m y j, sapei a and widiatmaka 2014 j environment and earth science 4(14) 107-117 [8] indarto, ratnaningsih a, and wahyuningsih s 2017 arpn journal of engineering and applied sciences 12(12) 37723778 [9] hall f r 1968 water resour. res. 4 975–983 [10] brutsaert w, and nieber j l 1977 water resour. res 13 637–643 [11] tallaksen l m 1995 j. hydrol. 165, 349–370 [12] smakhtin v u 2001 j. hydrol. 240 147–186 [13] stewart m k 2015 hydrol. earth syst. sci. 19 2587–2603 0,00 2,00 4,00 6,00 8,00 10,00 12,00 14,00 16,00 0,00 5,00 10,00 15,00 ta nk m od el d is ch ar ge (m 3 / s) master rc discharge (m3/s) master rc vs tank model civil and environmental science journal vol. 5, no. 1, pp. 008-016, 2021 8 analysis of flood peak discharge based on watershed shape factors muhadi1, lily montarcih limantara1, tri budi prayogo1 1water resources engineering department, faculty of engineering, universitas brawijaya, malang, 65145, indonesia1 *hadykraton2013@gmail.com received 30-01-2021; accepted 15-11-2021 abstract. regression analysis can develop unit hydrograph modeling by approaching the peak discharge (qp) and time to peak (tp) parameters. the main aim of this study is to design a model of peak discharge based on watershed shape factors. the watersheds used in this study are bontojai watershed, jonggoa watershed, kampili watershed, maccini sombala watershed, and jenelata watershed, which have slopes criteria below 10% and have complete recorded data of automatic water level recorder (awlr) and automatic rainfall recorder (arr). the validation results of corrected peak discharge data produce root mean squared error (rmse). then, the peak discharge model was conducted by regression analysis and validated with observed unit hydrographs. the results of this study indicate that the coefficient of determination r2 is 0.963. it means that the independent variable (x), namely the area of the watershed, the length of the main river, and the shape factor of the watershed, influences the peak discharge (qp) of 96.3%. keywords: peak discharge, model, observed hydrographs, shape factor, regression 1. introduction the lack of hydrograph data availability becomes a constraint for water construction planning. the unavailability of the data can be caused due to damaged recording devices, negligence of officers, damaged data so that it is illegible or lost [1], or the recording device has not been installed. these constraints mean that the hss models will provide considerable benefits. hss can provide critical information for evaluating water safety structures (hydraulic structures) and risks based on planning [2]. among practitioners, the application of this model is intended to analyze the design flood using rain data input. however, so far, practitioners in indonesia are still very dominant/fanatical about using hss nakayasu because considered the most practical, even though the application of this model for java island still requires calibration of several parameters [3]. 1 cite this as: muhadi., limantara, m., & prayogo, t.b. (2022). analysis of flood peak discharge based on watershed shape factors. civil and environmental science journal (civense), 5(1), 8-16. doi: https://doi.org/10.21776/ub.civense.2022.00501.2 civil and environmental science journal vol. 5, no. 1, pp. 008-016, 2021 9 limantara [4] tried to make a relatively simple hss limantara model by including the exact physical factors of the watershed, including the length of the main river: l, the area of the watershed: a, the mean slope of the river: s, the coefficient of the roughness of the watershed: n, the length of the river from the center of gravity of the watershed to the outlet: lc. given that hss models are researched and established in areas where the characteristics of the watershed are much different from the applied watershed, they often provide inaccurate analysis results. the impact will further lead to inefficiency in determining the dimensions of the water structures. the hydrological conditions in each area are unique, so not all existing methods and concepts can be used to solve hydrological problems in every watershed. [5]. the watershed shape factor (fd) gives a better result to be used and developed further in hss modeling [6]. the watershed shape factor is the watershed's physical characteristics and is defined as the value of the comparison between the perimeter of the watershed boundary (km) to the area of the watershed (km2). by observing the shape factor of the watershed, parameters of hss models can be made, including peak discharge (qp) and time to peak (tp), which are a function of the watershed shape factor. in this study, a peak discharge (qp) and time to peak (tp) model will be made based on the shape factor analysis of the watershed (fd). this model is expected to produce relatively simple mathematical model equations. there is no need to apply parameter calibration to produce a hydrograph model that characterizes the characteristics of studied watersheds. 2. materials and methods 2.1 data required the data required for this analysis, namely the studied watersheds map with a minimum scale of 1: 500.000, discharge data recorded by awlr including the relevant discharge curve, hourly rain data from arr, manual daily rainfall station data for watersheds that do not have arr, slope data and forest area data. 2.2 observed unit hydrographs: collins method observed unit hydrograph of the watershed is calculated by collins method, with the following calculation stages: 1. stage hydrograph is converted into discharge hydrograph with calibration. 2. baseflow is separated from the hydrograph by one of the empirical ways: straight line method [5]. 3. adequate rainfall that causes flooding is analyzed using the infiltration index  (phi index). 4. an arbitrary unit hydrograph is determined by determining the ordinates with a certain quantity. 5. the initial unit hydrograph (trial and error) is multiplied by all the adequate rainfall except for the most significant effective rainfall. 6. the direct runoff hydrograph obtained above is subtracted from the measured direct runoff hydrograph. the direct runoff hydrograph generated by the maximum rainfall is obtained, the second unit hydrograph (trial and error) is obtained. 7. the second unit hydrograph is compared with the initial unit hydrograph. if there is still a large difference (following the specified error standard), then the fifth and sixth stages are repeated based on the final unit hydrograph. 8. and so on until the most negligible possible difference is obtained between the final unit hydrograph and the previous unit hydrograph. looking for hydrograph units of observation for each watershed, for example, for jonggoa watershed, is obtained by the average of observed unit hydrographs ordinate at the same hour, the peak discharge, and the time to reach the peak discharge, with the following stages: 1. calculate the average time to peak and average peak discharge. civil and environmental science journal vol. 5, no. 1, pp. 008-016, 2021 10 2. calculate the dimensionless observed unit hydrograph (t/tp and q/qp) for each watershed. 3. calculate the dimensionless average observed unit hydrograph. 4. calculate the average of the observed unit hydrograph. 2.3 physical parameters of watershed that influence the model the factors that influence the model will be determined based on the coefficient of determination. the model was analyzed using the regression method with several alternatives based on the independent variables used (five, four, three, two, and one independent variable). in this analysis, peak discharge (qp) is a fixed variable. at the same time, the watershed's physical characteristics (a, l, and fd) are independent variables. thus, many alternatives will be generated. 2.4 analysis of peak discharge (qp) regression model on watershed shape factors the selection of the model is based on a rational model with the following criteria [7]: 1. independent and dependent variables have a reasonably strong correlation. the correlation coefficient r between 0.60 – 1.00 and the most significant coefficient of determination (r2). 2. the slightest estimate for the standard error (sey) value. 3. there is a significant influence between the independent and dependent variables in the regression model, and the f-test is used. 4. the deviation test in the selected hydrograph model is based on the observed unit hydrograph with a reasonably low deviation level. after analyzing by using peak discharge (qp) as a variable, the peak discharge value (qp) can be calculated using the regression model equation. this model will be corrected and validated with the peak discharge (qp) calculated by observed unit hydrographs using the root mean squared error (rmse) method. as for the validation method formula used in this study, namely: rmse = √ ∑ (xi yi)²ni=1 n (1) with: xi = observation data (actual data) yi = estimation data (estimation result data) n = the number of data table 1. physical parameters of watersheds for observed unit hydrographs calculation parameter watershed bontojai jonggoa kampili maccini sombala jenelata area of watershed (km2) 277.957 128.620 630.431 666.690 222.945 length of the river (km) 31.001 18.749 54.677 9.621 31.239 slope 0.0258 0.0613 0.0232 0.0186 0.0173 3. results and discussion 3.1 observed unit hydrographs: collins method physical parameters of watershed in calculating the observed unit hydrographs, several physical parameters of the watershed are required in the calculation, namely the area of the watershed, the length of the river, and the slope. analysis of physical parameters will be calculated for each studied watershed. civil and environmental science journal vol. 5, no. 1, pp. 008-016, 2021 11 based on table 1, then can be said that the area of the watershed, the length of the river, and the slope in each watershed have different values. however, it still belongs to the predetermined watershed category. maccini sombala is the largest watershed of several studied watersheds, with an area of 666.690 km2. kampili has the longest main river with a length of 54.677 km. therefore, the watershed with the most significant slope is jonggoa with 0.0613. this data will be used for further analysis. length of the awlr and arr recorded data paired water level data recorded on the awlr and hourly rainfall data recorded by arr are used to determine the flood hydrograph with the highest single peak, which will be used for the hydrograph simulation process of the observed unit hydrographs. therefore, it is necessary to determine the length of the data used in this analysis. based on table 2, the length of the recorded data available for each studied watersheds is different. the range of arr and awlr data used in this study is seven until ten years. this data will be used for further hydrograph calculations. time and discharge of observed unit hydrographs after obtaining the mean of peak discharge (qp) and time to peak (tp) values from the hso for each year, it can be said that the value of the time and discharge relationship to form the results of the observed unit hydrographs from the collins method. table 2. length of the awlr and arr recorded data watershed year bontojai 2011 – 2017 jonggoa 2008 – 2017 kampili 2008 – 2017 maccini sombala 2008 – 2017 jenelata 2011 – 2017 table 3. observed unit hydrographs of bontojai watershed t/tp q/qp t q 0.00 0.00 0.00 0.000 0.08 0.08 0.16 3.557 0.23 0.21 0.44 8.991 0.31 0.29 0.59 12.072 1.00 1.00 1.90 41.926 1.69 0.52 3.21 22.000 2.31 0.21 4.40 8.689 3.04 0.00 5.78 0.043 3.08 0.00 5.86 0.119 2.67 0.00 5.07 0.000 table 4. observed unit hydrographs of jonggoa watershed t/tp q/qp t q 0.00 0.00 0.00 0.000 0.06 0.05 0.14 0.714 0.21 0.21 0.47 3.351 1.00 1.00 2.20 15.846 1.58 0.49 3.47 7.842 2.20 0.32 4.85 5.116 2.71 0.29 5.96 4.540 2.92 0.29 6.42 4.520 2.53 0.29 5.56 4.608 2.83 0.20 6.23 3.118 3.04 0.16 6.69 2.467 3.33 0.16 7.33 2.458 3.63 0.08 7.98 1.216 3.92 0.06 8.62 0.977 4.21 0.00 9.26 0.000 based on table 3 to table 7 and figure 1 to figure 5, the peak discharge value (qp) and time to peak (tp) can be calculated. bontojai watershed has a peak discharge of 41.926 m3/s with a time to peak of 1.9 hours, jonggoa watershed has a peak discharge of 15.846 m3/s with a time to peak of 2.2 hours, the kampili watershed has a peak discharge of 67.731 m3/s with a time to peak of 3.4 hours, maccini sombala watershed has a peak discharge of 30.692 m3/s with a time to peak of 7.5 hours, and jenelata watershed has a peak discharge of 13.859 m3/s with a time to peak of 3.8 hours. civil and environmental science journal vol. 5, no. 1, pp. 008-016, 2021 12 table 6. observed unit hydrographs of maccini sombala watershed t/tp q/qp t q 0.00 0.00 0.00 0.000 0.08 0.02 0.56 0.517 0.12 0.07 0.89 2.061 0.23 0.19 1.72 5.730 0.25 0.28 1.91 8.672 0.34 0.35 2.52 10.702 0.47 0.43 3.52 13.339 0.54 0.50 4.06 15.314 0.69 0.67 5.21 20.618 0.85 0.90 6.35 27.480 1.00 1.00 7.50 30.692 1.15 0.85 8.65 26.111 1.31 0.68 9.79 20.934 1.46 0.47 10.94 14.549 1.61 0.36 12.08 10.985 1.62 0.34 12.16 10.401 1.71 0.30 12.82 9.126 1.77 0.27 13.28 8.386 1.90 0.26 14.23 8.006 2.01 0.22 15.08 6.647 2.00 0.19 15.00 5.743 2.10 0.17 15.75 5.195 2.20 0.16 16.50 4.874 2.30 0.15 17.25 4.658 2.40 0.15 18.00 4.496 2.50 0.14 18.75 4.406 2.60 0.07 19.50 2.162 2.70 0.03 20.25 1.042 2.80 0.02 21.00 0.624 2.90 0.01 21.75 0.441 3.00 0.01 22.50 0.351 3.10 0.01 23.25 0.261 3.20 0.01 24.00 0.219 3.30 0.00 24.75 0.129 3.40 0.00 25.50 0.086 3.50 0.00 26.25 0.043 3.60 0.00 27.00 0.000 table 7. observed unit hydrographs of jenelata watershed t/tp q/qp t q 0.00 0.00 0.00 0.000 0.09 0.01 0.35 0.076 0.18 0.02 0.69 0.223 0.27 0.03 1.04 0.355 0.36 0.04 1.38 0.488 0.45 0.05 1.73 0.620 0.18 0.05 0.69 0.739 0.17 0.10 0.66 1.359 0.38 0.19 1.44 2.532 0.50 0.35 1.91 4.735 0.53 0.54 2.00 7.293 1.00 1.00 3.80 13.589 1.47 0.84 5.60 11.419 1.95 0.68 7.40 9.253 2.42 0.53 9.20 7.185 2.90 0.42 11.01 5.767 3.08 0.32 11.70 4.320 3.49 0.24 13.28 3.325 4.10 0.19 15.57 2.591 3.90 0.15 14.83 2.015 4.27 0.12 16.21 1.583 3.57 0.09 13.56 1.181 3.83 0.06 14.54 0.850 4.08 0.04 15.51 0.580 3.57 0.04 13.57 0.477 3.77 0.03 14.32 0.360 3.97 0.02 15.07 0.312 3.88 0.02 14.76 0.281 4.83 0.02 18.34 0.230 5.05 0.01 19.19 0.167 5.28 0.01 20.05 0.124 6.00 0.01 22.80 0.098 6.25 0.01 23.75 0.072 6.50 0.00 24.70 0.058 6.75 0.00 25.65 0.043 7.00 0.00 26.60 0.029 7.25 0.00 27.55 0.014 7.50 0.00 28.50 0.000 explanation: t = time (hour), tp = time to peak (hour), q = discharge (m3/s), qp = peak discharge (m3/s), t = time (hour). civil and environmental science journal vol. 5, no. 1, pp. 008-016, 2021 13 figure 1. the curve of collins for bontojai watershed figure 2. the curve of collins for jonggoa watershed figure 3. the curve of collins for kampili watershed figure 4. the curve of collins for maccini sombala watershed figure 5. the curve of collins for jenelata watershed 3.2 physical parameters of watershed that influence the model with peak discharge (qp) as the independent variable and the area of the watershed (a), most extended river length (l), watershed shape factor (fd), namely as a comparison between the edge (k) and the area of the watershed (a) as the dependent variable, it will generate several alternative regression equations. this alternative selection is based on the rationalization of models and criteria. from the results of morphometric map analysis using gis applications, several physical parameters of the watershed were obtained, such as the area of the watershed (a), the length of the main river (l), the perimeter of the watershed (p), and the shape factor of the watershed (fd). based on table 8, it can be said that the shape factor (fd) influences the result of peak discharge value. 0 10 20 30 40 50 1 2 3 4 5 6 7 8 9 10 d is c h a rg e ( m 3 /s ) time (h) 0 5 10 15 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 d is c h a rg e ( m 3 /s ) time (h) 0 10 20 30 40 50 60 70 80 1 2 3 4 5 6 7 8 9 10 11 12 13 14 d is c h a rg e ( m 3 /s ) time (h) 0 5 10 15 20 25 30 35 1 3 5 7 9 1113151719212325272931333537 d is c h a rg e ( m 3 /s ) time (h) 0 2 4 6 8 10 12 14 16 1 3 5 7 9 1113151719212325272931333537 d is c h a rg e ( m 3 /s ) time (h) civil and environmental science journal vol. 5, no. 1, pp. 008-016, 2021 14 table 8. physical parameters of watershed that influence the peak discharge (qp) model no watershed tp qp a l p fd hour (m3/s) km2 km km 1 bontojai 1.90 40.471 277.957 31.95 91.79 0.41434 2 jonggoa 2.20 15.846 128.620 18.75 58.638 0.46983 3 kampili 3.40 67.731 630.431 54.68 152.422 0.34083 4 maccini sombala 7.50 30.692 666.690 69.29 201.00 0.20726 5 jenelata 3.80 13.589 222.946 31.24 82.035 0.41609 3.3 peak discharge (qp) regression model on watershed shape factor statistical analysis in microsoft excel is used for choosing the model. the model is obtained by trial and error with various regression models. from the trial and error results of various regression models, the regression model with the ln function has the highest value of coefficient determination of r squared. this shows that the equation generated from the model is the best of the other regression models that have been tried. figure 6. the results of regressions analysis based on figure 6, the results of the peak discharge (qp) model are obtained as follows: 1. has a regression equation model: qp = a4,3 x l-5,034 x fd-0,085 x e-3,347 2. this peak discharge model has a coefficient of determination r2 of 0.963. it means that the independent variable (x), the area of the watershed, the length of the main river, and the form factor of the watershed are affecting the peak discharge (qp) value with 96.3%. table 9. comparison of trial regression models no regression types equation models r2 1 linear regression qp = -91.27 + 0.241a + 1.18l + 221.45fd 0.907 2 log regression qp = 0.035 + a4.3 l5.03 fd 0.09 0.963 3 multiplication regression (ln) qp = a4.3 x l-5.034 x fd-0.085 x e-3.347 0.964 4 logest regression qp = 64.31 x 1.01a x 0.91l x 0.29fd 0.798 civil and environmental science journal vol. 5, no. 1, pp. 008-016, 2021 15 validation of peak discharge (qp) model model validation is calculated in the same sub-watersheds, but using data input of peak discharge model formula that has been corrected to peak discharge that calculated by using observed unit hydrographs collins method. table 10. recapitulation of peak discharge (qp) model and peak discharge (qp) collins no watershed qp model qp collins qp model -collins (qp model-collins)2 1 bontojai 32.684 40.471 -7.787 60.632 2 jonggoa 17.225 15.846 1.378 1.900 3 kampili 75.246 67.731 7.515 56.478 4 maccini sombala 30.296 30.692 -0.396 0.157 5 jenelata 14.182 13.589 0.593 0.352 total 1.304 119.519 based on table 10, it can be said that the value of the peak discharge model has results that are close to the observed peak discharge. maccini sombala watershed has the smallest difference in peak discharge value between the model and the actual peak discharge of 0.396. it means that the modeling results describe the actual measured discharge conditions. although, bontojai watershed has the most significant difference in peak discharge value between the model and the actual peak discharge that is 7.787. therefore, it is necessary to examine the accuracy of the model for all watersheds. to show the accuracy value of peak discharge calculated from the regression modeling a validation test was conducted using rmse method. rmse =√ 119.519 5 = 4.89 (2) the root mean square error (rmse) value of the model peak discharge is 4.89. it shows that the value can be considered small or close to zero (0). in other words, this modeling has a reasonably good validity value. 4. conclusion the peak discharge value (qp) in the model in the five watersheds has almost the same value compared to the observed unit hydrograph (hso) analysis results. by using statistical regression analysis, the result shows that the coefficient determination of the peak discharge model in the jeneberang river area explained that the independent variable (x) is affecting the value of peak discharge. furthermore, the independent variable (x) are the watershed's area, the length of the main river, and the watershed shape factor. to obtain optimal research results, use linear zero regression statistical analysis and adding complete das morphometric variables for further research are suggested. references [1] sobriyah, sudjarwadi, s. harto, and d. legono, “input data hujan dengan sistem grid menggunakan cara pengisian dan tanpa pengisian data hilang pada sistem poligon thiessen,” in kongres vii & pertemuan ilmiah tahunan (pit) xviii hathi, 2001, pp. 66– 76. [2] b. zhao, y.-k. tung, k.-c. yeh, and j.-c. yang, "storm resampling for uncertainty analysis of a multiple-storm unit hydrograph," j. hydrol., vol. 194, no. 1, pp. 366–384, 1997, doi: https://doi.org/10.1016/s0022-1694(96)03112-5. [3] a. a. hoesein and l. m. limantara, “kalibrasi parameter hidrograf satuan sintetik nakayasu di sub das lesti, genteng, dan amprong, jawa timur,” 1993. [4] l. m. limantara, “model hidrograf satuan sintetis untuk das-das di sebagian indonesia,” civil and environmental science journal vol. 5, no. 1, pp. 008-016, 2021 16 disertasi doktor, univ. brawijaya, 2006. [5] s. harto, analisis hidrologi. jakarta: gramedia pustaka utama, 1993. [6] soewignyo, “kajian pengaruh faktor bentuk das terhadap parameter hidrograf satuan sintetik sungai-sungai di jawa timur,” in kongres vii & pertemuan ilmiah tahunan (pit) xviii hathi, 2001, pp. 98–103. [7] soewarno, hidrologi aplikasi metode statistik untuk analisa data, jilid 1soe. bandung: penerbit nova, 1995. civil and environmental science journal vol. 4, no. 2, pp. 163-172, 2021 163 health protocol in penataran train during the covid-19 pandemic nur aldi firmansyah, achmad wicaksono, m. ruslin anwar civil engineering department, faculty of engineering, universitas brawijaya, malang, 65145, east java, indonesia aldi68574@gmail.com received 01-06-2021; accepted 13-07-2021 abstract. penataran train decreased the number of passengers by 77.13% in april 2020, which resulted in a reduction in travel frequency and change origin-destination during the covid-19 pandemic. this study aims to determine the characteristics of the penataran train passengers and obtain policy recommendations about service standards and travel requirements based on respondents' choices using descriptive statistics. questionnaires were distributed to 417 penataran train passengers during new adaptation period. this study indicates that the frequency of trips during the new adaptation period is lower than before the pandemic. only 10.55% of respondents give the reason that the risk of transmitting covid-19 on the penataran train is lower than other transportation. the maximum seating capacity is reduced to 50% according to respondent's perceptions. wearing a mask, keep a distance, and wearing long-sleeved clothing can still be carried out because they are considered necessary as requirements for passenger travel. the genose c19 test letter is not recommended to be used as a document requirement because most respondents with low income do not want additional costs. keywords: covid-19 pandemic, health protocol, new adaptation period, penataran train1 1. introduction covid-19 is a contagious disease that attacks the human respiratory system and has become a major health threat to society. it is transmitted through direct contact, spread by coughing or sneezing from an infected person [1] [2]. in indonesia, the spread of the coronavirus is very fast, from the first patient on march 2, 2020 [3], to reaching one and half million cases on march 29, 2021 [4], and now the cases are still increasing. the government has taken mitigation to prevent infection and transmission of covid-19, namely large-scale social restriction policy in several cities. several activities have been limited in the implementation, such as schooling, working, social and cultural activities, and traveling [5]. this policy 1 cite this as: firmansyah, n.a., wicaksono, a. & anwar, r. (2021). health protocol in penataran train during the covid-19 pandemic. civil and environmental science journal (civense), 4(2), 163-172. doi: https://doi.org/10.21776/ub.civense.2021.00402.6 mailto:aldi68574@gmail.com civil and environmental science journal vol. 4, no. 2, pp. 163-172, 2021 164 resulted in decreased mobility in various sectors. of the 34 provinces in indonesia, the highest decline in mobility at 25 provinces has occurred at the transport station. in contrast, residential areas show increased mobility during the new adaptation period [6]. it shows that people in indonesia are still afraid to travel, especially when using public transportation. many people may avoid public transport because it can be considered a breeding ground for the virus, and it is difficult to avoid contact with other passengers [7]. the penataran train is one of the trains affected by covid-19. the decrease in the number of passengers reached 23.54% in march 2020, 77.13% in april 2020, and 7.10% in may 2020 [8]. as a result, this train experienced a reduction in the frequency of travel and changes in origin-destination for three-step until finally, it entered a new adaptation period. at this time, the implementation of health protocols was strictly carried out, and reduced seating capacity as recommended physical distancing must also be fulfilled. to minimize the risk of spreading covid-19 on trains, passengers must improve hand hygiene and use protective equipment such as face masks. in addition, the operator must also check passenger temperatures, clean seats using the disinfectant liquid, and adjust the distance between passengers to at least two seats [9]. the coronavirus outbreak (covid-19) has not ended, but indonesia's economy must continue, especially in the public transportation sector, one of which is rail transportation. the most important thing is to prepare the best scenario for train facilities and infrastructures that are humanist, clean, healthy, and safe by observing established health protocols. this study aims to determine the characteristics of the respondent of the penataran train before the covid-19 pandemic and the new adaptation period. in addition, policy recommendations related to service standards and travel requirements were given based on respondents' choices. table 1. secondary data from several institutions and regulations no institutions or regulations required data 1 indonesian railways company operational area 8 surabaya • implementation of the covid-19 health protocol on the penataran train 2 decree of minister of health of the republic of indonesia no. hk.01.07/menkes/382/2020 • health protocol policies in transportation modes for operators, workers, and passengers 3 regulation of minister of transportation of the republic of indonesia no. pm 18 and pm 41 of 2020 • transportation controls was carried out during travel • limiting the number of passengers on each mode of transportation 4 circular letter of minister of transportation of the republic of indonesia no. se 14 and se 15 of 2020 • limiting the number of passengers on local train • health protocol policies that must be implemented by train passengers • health protocol facilities that must be provided by the operator 5 circular letter of minister of transportation of the republic of indonesia no. se 27 of 2021 • health protocol policies that must be implemented by train passengers during travel • health requirement policies for local train passengers 6 circular letter of the covid-19 handling task force of the republic of indonesia no. 12 of 2021 • health protocol policies that must be implemented by passengers during travel • health requirement policies for domestic travelers • monitoring, controlling, and evaluating covid-19 health protocol policies on public transportation civil and environmental science journal vol. 4, no. 2, pp. 163-172, 2021 165 2. research methods the research location was conducted in the surabaya gubeng station and malang station. in addition, this research was also conducted during the penataran train trip. the questionnaire was filled out online using the google form application. this research was held for four months, from january to april 2021. research respondents were passengers who had traveled using the penataran train during the covid-19 pandemic, aged 17 to 65 years old. the number of samples in this study was 417 people. there are two sampling techniques used in this study, namely simple random sampling and incidental sampling [10]. the data collection methods are primary and secondary surveys. the primary survey conducted was field observation by directly observing the implementation of health protocols on the penataran train and questionnaire surveys by distributing questionnaires to passengers. the secondary survey was carried out by collecting data and information from several institutions and regulations, as shown in table 1. the data analysis used descriptive statistic, which explain the characteristics and travel behavior of the respondents. 3. result and discussion 3.1. implementation of the covid-19 health protocol policy regulators and operators are required to arrange the best scenario, which is called health protocol, to restore confidence and reduce the concern of passengers about the spread of the covid-19 virus on trains. during the new adaptation period, the government has the task to make new regulations related to health protocols that must be completed on public transportation, while operators are required to complete and implement health protocols when operating their vehicles. indonesia railways company, as the dominant operator of the railways in indonesia, has implemented the covid-19 health protocol policy, which follows the regulations of the ministry of health [11], the ministry of transportation [12] [13] [14] [15] [16], and the task force for the acceleration of handling covid-19 [17]. health protocols that have been implemented in the operation of the penataran train, such as: 1. the crew trains use personal protective equipment such as mask, face shield, and gloves; 2. the conductor and railway police check passengers' temperature and health every three hours; 3. the conductor and railway police check passengers' health protocol every one hour; 4. on trip cleaning clean interior of the train with disinfectant liquid; 5. limiting seat capacity by putting cross signs on seats; 6. the operator provides hand sanitizers that are placed in easily visible spot; 7. the conductor instructs passengers to keep obeying health protocol via train audio; 8. the operator provides isolation space for passengers who have abnormal body temperature and health problems; and 9. travel requirements that passengers must fulfill, such as: a. wearing a medical or three-ply mask; b. keeping the distance according to the seat number; and c. wearing a jacket or long sleeve clothes. 3.2. characteristics of respondents during the covid-19 pandemic figure 1-4 illustrates the respondents' characteristics based on age, high education level, occupation, and monthly income. figure 1 explains that most respondents were 21-30 years old, with a percentage of 70.74%. it proves the results of direct observations in the field that productive people dominated the passengers of the penataran train during the new adaptation period. figure 2 explains that the respondents are dominated by passengers with senior high school level (45.80%) and undergraduate (36.69%). while the most occupations are students (35.49%) and private employees (33.09%), as shown in figure 3. there is a correlation between age, high education level, and occupation. two groups dominate respondents: respondents aged 21-30 years old who still have the status as a university student civil and environmental science journal vol. 4, no. 2, pp. 163-172, 2021 166 0.00% 0.48% 3.60% 9.59% 15.59% 70.74% >60 51-60 41-50 31-40 17-20 21-30 0.24% 0.96% 4.80% 11.51% 36.69% 45.80% elementary junior high graduate diploma undergraduate senior high 2.64% 4.08% 4.32% 20.38% 33.09% 35.49% unemployment others self employed public servant private employee student 0.24% 3.84% 4.80% 19.42% 24.70% 47.00% > 10 8 9.99 6 7.99 4 5.99 2 3.99 < 2 with the latest education senior high school and respondents aged 21-30 years who are private employees with an undergraduate education background. figure 4 shows that most respondents' monthly income is below idr 2,000,000 with 47.00%. it is evidenced by the fact that some respondents are students who do have no income, only a monthly stipend from their parents. figure 1. respondent characteristics based on age. figure 2. respondent characteristics based on high education level. figure 3. respondent characteristics based on occupation. figure 4. respondent characteristics based on monthly income. based on figure 5, the highest travel frequency before the pandemic and new adaptation period was 1-3 times a month. the frequency of trips during the new adaptation period is lower than before the pandemic; this is due to restrictions on out-of-home activities and restrictions on traveling out of town by the local government. figure 5. comparison of travel frequency between before pandemic and new adaptation period. 16 310 44 16 310 359 28 5 25 0 100 200 300 400 never 1 3 times 4 6 times 7 9 times 10 times or more before pandemic new adaptation period civil and environmental science journal vol. 4, no. 2, pp. 163-172, 2021 167 figure 6 shows that most travel destinations before the pandemic and new adaptation period were social or family activities. as a local train, penataran train has more stop stations than commercial trains, which are suitable for transportation to attend social activities or go to homecoming. during the covid19 pandemic, the government suggested doing distance or online learning. figure 6. comparison of travel frequency between before pandemic and new adaptation period. figure 7. comparison of the reason for using penataran train before the pandemic and new adaptation period. based on figure 7, the most reason for using the penataran train before the pandemic and new adaptation period is cheaper cost. the penataran train is one of the trains that get public service obligations from the government, making the price more affordable than other trains and other public transportations. the lack of activity during the covid-19 pandemic impacts reduced income by some people; therefore, they choose cheap transportation to carry out their mobility. only 10.55% of respondents gave the reason that the risk of transmitting covid-19 on the penataran train is lower than other transportation, which means passengers feel that health protocols have not been appropriately implemented. during the new adaptation period, the frequency of trips 1-3 times a month was dominated by passengers with social or family activities and followed by shopping or tour activities, as shown in table 2. while the frequency of trips more than 3 times a month was dominated by working or trading activities. these results indicate that most respondents have followed local government recommendations regarding restrictions on activities outside the home. activities carried out are only important and urgent, such as going to work and doing business. 16 94 155 38 114 0 86 191 26 114 0 50 100 150 200 250 never working/trading social/family school/college shopping/tour before pandemic new adaptation period 16 92 81 63 59 100 6 00 62 82 57 65 106 1 44 0 20 40 60 80 100 120 never easier access higher safety shorter time more comfortable condition cheaper cost no choice lower covid-19 transmission before pandemic new adaptation period civil and environmental science journal vol. 4, no. 2, pp. 163-172, 2021 168 table 2. travel frequency by purpose working/ trading school/ college social/ family shopping/ tour total 1-3 times 52 23 174 110 359 4-6 times 13 0 12 3 28 7-9 times 3 1 1 0 5 10 times or more 18 2 4 1 25 total 86 26 191 114 417 table 3 shows that cheaper cost becomes the strongest reason for respondents to choose the penataran train on the frequency of trips 1-9 times a month. whereas on the frequency of trips ten times or more a month, some respondents considered that the penataran train had higher safety during the trip. respondents who consider the penataran train as transportation with lower covid-19 transmission travel only 1-3 times a month. it is indicated that this train cannot be regarded as safe from the spread of covid-19. table 3. travel frequency by reason for choosing penataran train easier access higher safety shorter time more comfortable condition cheaper cost no choice lower covid-19 transmission total 1-3 times 53 67 47 61 90 1 40 359 4-6 times 3 6 4 3 8 0 4 28 7-9 times 1 1 1 0 2 0 0 5 10 times or more 5 8 5 1 6 0 0 25 total 62 82 57 65 106 1 44 417 3.3. respondents' priorities on service standards and travel requirements fifteen services must be completed on the penataran train according to transportation policies during the new adaptation period. respondents must choose one service that is considered the most important during the trip, that the results are shown in table 4. in this figure, it can be seen that the seating capacity limitation was chosen by most respondents with a percentage of 48.44%, followed by a physical distancing facility with signs on the floor (11.27%) and cleaning trains with disinfectants liquid (10.31%). from 15 services that have to be chosen by the respondents, 8 services have been implemented, and 7 others are not yet available on the penataran train. distancing facilities with signs on the floor is the second most preferred service by respondents but are not yet available on the penataran train. operators can add this service to the health protocol on the penataran train. the purpose of providing this service is to reduce the spread of the covid-19 virus when passengers queue on the train. the seating capacity of the penataran train is 70% of the total number of seats [14]. before the covid-19 pandemic, the seating capacity on each train was 159 passengers, while during the new adaptation period decreased to 74 passengers. figure 8 shows the best maximum seating capacity according to the respondent's perception. as many as 54.20% of respondents chose a maximum capacity of 50% of the number of seats. meanwhile, the maximum capacity of 70%, which has been implemented in the penataran train, is in second place with 23.74%. figure 9 is a recommended seat map if a maximum capacity of 50% is run on the penataran train. with this change in seating capacity, the operator can increase ticket prices, or the government can increase subsidies to cover the difference between train revenue and operating costs. civil and environmental science journal vol. 4, no. 2, pp. 163-172, 2021 169 table 4. most important passenger service based on respondent's perception type of service number of voters seating capacity limitation 48.44% distancing facilities with signs on the floor 11.27% cleaning train with disinfectant liquid 10.31% checking the implementation of passenger health protocols 9.35% hand sanitizer facilities in the train 4.32% check passengers' body temperature and health 4.32% medical personnel during the trip 2.64% windows that open to increase air circulation from the outside 2.40% separation facility between passengers over 50 years old with other passengers 1.92% information about protocols to prevent the spread of covid-19 via audio 1.20% selling personal protective equipment on the train 0.96% crew trains always use personal protective equipment 0.96% information about protocols to prevent the spread of covid-19 via visual 0.96% isolation room on the trip 0.72% divider cover in the train dining room 0.24% figure 8. maximum passenger capacity in penataran train during the new adaptation period. figure 9. map of train seats with a maximum capacity of 50%. during the new adaptation period, passengers are also required to carry out health protocols to prevent transmission of covid-19. at this time, health protocols that passengers must carry out are 54.20% 13.67% 23.74% 2.88% 0.72% 4.80% maximum 50% maximum 60% maximum 70% maximum 80% maximum 90% maximum 100% civil and environmental science journal vol. 4, no. 2, pp. 163-172, 2021 170 wearing a mask, keeping the distance, and wearing long-sleeved clothing or a jacket. document requirements such as rapid antigen / pcr / genose c19 test results are only required for long-distance train travel, not for local or agglomeration train travel [16] [17]. figure 10 shows the respondents' perceptions regarding the travel requirements that must be fulfilled during this period. three travel requirements were used as questions in the questionnaire. in addition, the genose c19 test was also questioned by respondents to measure the extent of the respondent's ability to comply with this requirement. the result shows that most respondents choose three health protocols that needed to be implemented. on the other hand, most respondents considered that the genose c19 test was not necessary to be a travel requirement. figure 9. passenger travel requirements in penataran train during new adaptation period based on respondent's perception. table 5 shows the correlation between respondents 'perceptions about the genose c19 test as a travel requirement and the respondents' monthly income. most respondents with incomes below 2 million consider the genose c19 test unnecessary as a travel requirement. respondents answered that it is necessary to have an average income of idr 3,972,424, while respondents responded that it is unnecessary and has an average income of idr 2,285,516. these results indicate that low-income passengers are unwilling to increase their travel costs to pay for the genose c19 test. in addition, these results reinforce that the most reason for using the penataran train is cheaper cost, which passengers need affordable public transportation during the covid-19 pandemic. therefore, the genose c19 test letter does not need to be used as a requirement for the penataran train trip. table 5. correlation between respondent's perceptions about genose c19 test and monthly income. necessary unnecessary total < 2 million 58 138 196 2 3.99 million 32 71 103 4 5.99 million 41 40 81 6 7.99 million 18 2 20 8 9.99 million 15 1 16 > 10 million 1 0 1 total 165 252 417 39.57% 53.00% 71.70% 81.77% 60.43% 47.00% 28.30% 18.23% medical certificate with a negative result of the genose c19 test wearing a jacket or long sleeve clothes keeping the distance (physical distancing) wearing a medical or 3 ply mask necessary unnecessary civil and environmental science journal vol. 4, no. 2, pp. 163-172, 2021 171 4. conclusions respondents were dominated by passengers aged 21-30 years (70.74%), with the latest education being senior high school (45.80%), being a student (35.49%), and having monthly income less than idr 2.000.000 (47.00%). the frequency of trips during the new adaptation period is lower than before the pandemic. social or family activities are the most preferred travel purpose; on the other hand, school or college activities are the least chosen. the frequency of trips, ten times or more monthly, is dominated by passengers with the travel purpose of working or trading. the most preferred reason for using the penataran train is cheaper cost and is followed by higher safety. respondents who considered the penataran train to be a place with lower covid-19 transmission were only 10.55% of the respondents. health protocols on the penataran train must be added, such as distance facilities with signs on the floor for queuing passengers. most respondents want the maximum seating capacity on each train to be 50%; if this recommendation is implemented, the operator can increase its ticket price. the government can increase the subsidy to cover the difference between train revenues and operating costs. wearing a mask, keeping the distance, and wearing long-sleeved clothing or a jacket are still considered necessary for the penataran train trip. most respondents with incomes below 2 million disagree if the genose c19 test letter was used as a document required for using the penataran train due to additional costs outside the ticket costs. references [1] h. a. b. s. rothan, "the epidemiology and pathogenesis of coronavirus disease (covid-19) outbreak," autoimmunity, no. 109, 2020. [2] s. chavez, "coronavirus disease (covid-19): a primer for emergency physicians," emergency medicine, 2020. [3] m. h. sukur, b. kurniadi, haris and r. faradillahisari, "penanganan pelayanan kesehatan di masa akademi covid-19 dalam perspektif hukum kesehatan," inicio legis, vol. i, no. 1, 2020. [4] t. f. f. t. a. o. h. covid-19, "the covid-19 situation in indonesia," 29 3 2021. [online]. available: https://covid19.go.id/. [accessed 26 5 2021]. [5] m. o. h. r. o. indonesia, "regulation of the minister of health of the republic of indonesia no. 9/2020 about large-scale social restriction guidelines for accelerating the handling of coronavirus disease 2019 (covid-19)," ministry of health republic of indonesia, jakarta, 2020. [6] c.-1. c. r. google, "covid-19 community mobility report," 24 january 2021. [online]. available: https://www.google.com/covid19/mobility/?hl=id. [accessed 15 february 2021]. [7] j. d. vos, "the effect if covid-19 and subsequent social distancing on travel behavior," transportation research interdisciplinary perspectives, vol. 5, pp. 100121-100123, 2020. [8] i. r. company, interviewee, the volume passanger of penataran train on january 2019 december 2020. [interview]. 22 february 2021. [9] m. hu, h. lin, j. wang, c. xu, a. j. tatem, b. meng, x. zhang, y. liu, p. wang, g. wu, h. xie and s. lai, "risk of coronavirus disease 2019 transmission in train passengers: an epidemiological and modeling study," clinical infectious diseases, vol. 72, no. 4, pp. 60410, 2021. [10] sugiyono, metode penelitian kuantitatif, kualitatif, dan kombinasi (mixed methods), bandung: alfabeta, 2018. [11] m. o. h. r. o. indonesia, "decree of the minister of health of the republic of indonesiano hk.01.07/menkes/382/2020 about protocol of health for the community in place and civil and environmental science journal vol. 4, no. 2, pp. 163-172, 2021 172 public facilities for prevention and control of coronavirus disease 2019 (covid-19)," the ministry of health republic of indonesia, jakarta, 2020. [12] m. o. t. r. o. indonesia, "regulation of the minister of transportation of the republic of indonesia no. 18/2020 about transportation control in order to prevent the spread of corona virus disease 2019 (covid-19)," the ministry of transportation republic of indonesia, jakarta, 2020. [13] m. o. t. r. o. indonesia, "regulation of the minister of transportation of the republic of indonesia no. 41/2020 on changes to the regulation of the minister of transportation of the republic of indonesia no. 18/2020 on transportation control in order to prevent the spread covid-19," the ministry of transportation republic of indonesia, jakarta, 2020. [14] m. o. t. r. o. indonesia, "circular letter no. 14/2020 on guidelines and technical instructions for rail transportation in new adaptation period to prevent the spread of coronavirus disease 2019 (covid-19)," the ministry of transportation republic of indonesia, jakarta, 2020. [15] m. o. t. r. o. indonesia, "amendment to the circular letter of the minister of transportation no. 14/2020 on guidelines and technical instructions for rail transportation control in new adaptation period to prevent the spread covid-19," the ministry of transportation republic of indonesia, jakarta, 2020. [16] m. o. t. r. o. indonesia, "circular letter no. se 27/2021 on instruction for implementing people' travel by rail transportation during the pandemic corona virus disease 2019 (covid-19)," the ministry of transportation republic of indonesia, jakarta, 2021. [17] t. f. t. a. h. covid-19, "circular letter no. 12/2021 on provision for travel of domestic during the pandemic coronavirus disease 2019 (covid-19)," government of indonesia, jakarta, 2021. civil and environmental science journal vol. 5, no. 1, pp. 017-025, 2022 17 impact on the existence of new toll road section due to mode choice between transportation mode using modal split methods (case study: tulungagung-surabaya) muhammad alfian nasril b1,*, wahju herijanto2, hera widyastuti2 1 master of civil engineering, sepuluh nopember institute of technology, tulungagung, east java 2 transportation engineering and management, sepuluh nopember institute of technology, surabaya, east java *alfiannasrill@gmail.com received 09-01-2022; accepted 07-02-20221 abstract. the java-trans highway is almost connected from west to the east of java island and now, there is a new section that will be built, those are kertosono-kediri section and kediritulungagung section. the impact from these construction in the future will shorten the travel time. tulungagung-surabaya buses which use the highway only take 3-3,5 hours of travel time with route combinations between national and highway roads. this research aims to find the model of mode choice proportion between bus, non-toll bus, cars, and train due to tulungagungsurabaya’s highways in 2023. the travel attributes used in this research are travel time and travel cost between bus, non-toll bus, cars, and train. then, the model could predict the mode choice proportion in the future, after the construction finished. the method for modelling is modal split which uses power function (α) and deterrence function (β). mode choice model that is used is a modal split with power function (α) with nmae values 0,5284 which is close to 0. the interpretation of nmae value is the smaller the value the better the model, because the model would represent the existing condition in which the model could predict future condition. keywords: modal split, mode choice, nmae 1. introduction one of the land connections to surabaya city and another city is toll-road. toll road which connects surabaya city is now connected from jakarta, malang, madura, and situbondo. according to the media [1] in 2023 the toll road from tulungagung to surabaya will be open. today, the section construction from kertosono to kediri is in progress. soon, the section will continue from kediri to tulungagung. the existence of a new section from kertosono to tulungagung directly would change the pattern of mode choice [2]. 1 cite this as: nasril, m.a., herijanto, w., & widyastuti, h. (2022). impact on the existence of new toll road section due to mode choice between transportation mode using modal split methods (case study: tulungagung-surabaya). civil and environmental science journal (civense), 5(1), 17-25. doi: https://doi.org/10.21776/ub.civense.2022.00501.3 civil and environmental science journal vol. 5, no. 1, pp. 017-025, 2022 18 there are a lot of options to go to surabaya from tulungagung. for example, there are 2 types of buses which use toll roads and non-toll roads. between those 2 options are given choices about travel time and travel cost. bus that uses a toll road just needs 3-3.5 hours to do one trip from tulungagung to surabaya. otherwise, buses that do not use toll-roads need about 3.5-4 hours or one trip from tulungagung to surabaya. especially after tulungagung to surabaya is fully connected with a toll-road. every transportation mode will go faster than before. the differentiation of travel time, travel distance, and travel cost would change the mode choice between transportation modes. in this research, the subject for this mode choice purpose are bus, private car, and train. mode choice is a part of decision making in transportation modelling that inflicts a lot of identifications, such as a relevant mode transportation performance, appropriate mode choice, level of service, and evaluation of mode performance [3]. the owner or developer focuses on travel cost and time [4]. the main problem in this research is the existence of a toll road new section between kertosono to tulungagung as a new competition that causes a different mode choice between bus, car, and train. the aspect of mode choice that is used in this research is the differentiation between travel cost and travel time. this research aims to get a model for mode choice between bus, car, and train after a new section of kertosono-tulungagung finishes in 2023rd. 2. material and methods this section contains work steps that would be used to guide this research. this section aims to make this research go well, systematically, and could reach the goals. 2.1. time and location this research is located in gayatris’s bus station and tulungagung train stop in tulungagung district. this research is done in a couple days (weekdays and weekend) for doing a survey. because of pandemic covid-19, the survey uses google form. table 1. scenarios which use for stated preferences survey scenarios x1 if economic bus or non-toll bus still exist and did not use toll-road x2 if trains still exist without travel time and travel cost changes. x3 vip bus or toll bus use combination routes like tulungagung-kertosono not using toll-road and kertosono-surabaya using toll road. x4 if vip bus or toll bus use combination routes like tulungagung-kediri not using toll-road and kediri-surabaya using toll road. x5 if vip bus or toll bus directly goes from tulungagung to surabaya using toll road. x6 if cars use combination routes like tulungagung-kertosono not using toll-road and kertosono-surabaya using toll road. x7 if cars use combination routes like tulungagung-kediri not using toll-road and kediri-surabaya using toll roads. x8 if a car directly goes from tulungagung to surabaya using a toll road. 2.2. research survey in this research, the method of survey is stated and revealed preferences. revealed preferences and stated preferences are included in the discrete choice experimental (dce) method. the preparation of the dce should be carried out in 3 phases. the first phase is conducting a literature review and survey at the research site which aims to obtain the variables on the questionnaire that have been used in the past in the analysis of mode selection. the second phase is to conduct interviews with experts in mode selection analysis with the aim of controlling the feasibility of the questionnaire. the last phase is conducting an interview experiment with respondents with the aim of adjusting the variables that have civil and environmental science journal vol. 5, no. 1, pp. 017-025, 2022 19 been used with field conditions [5]. stated preferences methods made based on hypotheses which adjusted with transportation users [6]. hypothesis made based on determined generalised cost according to mode route. attributes which are used in hypothesis construction are based on travel cost, travel time, and variation of route. all the scenarios based on years of 2023rd after a new section of toll road was already built. the following table which is used for the scenario for stated preferences method is shown on table 1. 2.3. analysis of data collected data which was obtained from the stated preferences survey is being processed and then being analysed using statistical methods. this research uses modal split with power and difference function to get a model of tulungagung-surabaya mode choice proportion between modes. 2.3.1. deciding mode transportation generalised cost. cost determination is based on type of mode. for passenger car, the generalised cost are toll road cost, vehicle operation cost, and value of time. otherwise, for public transportation, generalised cost which used are ticket cost and value of time. if written in the form of formula is as follows: 𝐺𝑒𝑛𝑒𝑟𝑎𝑙𝑖𝑠𝑒𝑑 𝑐𝑜𝑠𝑡 = 𝑎0 + 𝑎1𝑥1 + 𝑎2𝑥2 with, ● 𝑎0 = toll cost (rp) ● 𝑎1 = vehicle operation cost (rp/km) ● 𝑥1 = travel distance (km) ● 𝑎2 = value of time (rp/hours) ● 𝑥2 = travel time (hours) for public transport generalised cost is as follows: 𝐺𝑒𝑛𝑒𝑟𝑎𝑙𝑖𝑠𝑒𝑑 𝑐𝑜𝑠𝑡 = 𝑎0 + 𝑎1𝑥1 with, ● 𝑎0 = ticket cost (rp) ● 𝑎1 = value of time (rp/hours) ● 𝑥1 = travel time (minutes) 2.3.2. mode choice using mode split methods. mode choice model in this research is using modal split with two different kind of function that is power function (α) and difference function (β) which is written in this form of formula [7]: power function (α) 𝑃𝑀𝑜𝑑𝑒1 = 𝐶𝑀𝑜𝑑𝑎1−𝛼𝑀𝑜𝑑𝑒1 𝐶𝑀𝑜𝑑𝑒1−𝛼𝑀𝑜𝑑𝑒1 + 𝐶𝑀𝑜𝑑𝑒2−𝛼𝑀𝑜𝑑𝑒2 + 𝐶𝑀𝑜𝑑𝑒3−𝛼𝑀𝑜𝑑𝑒3 + 𝐶𝑀𝑜𝑑𝑒4−𝛼𝑀𝑜𝑑𝑒4 deterrence function (β) 𝑃𝑀𝑜𝑑𝑒1 = 𝐸𝑋𝑃(−𝛽𝑀𝑜𝑑𝑒1. 𝐶𝑀𝑜𝑑𝑒1) 𝐸𝑋𝑃(−𝛽𝑀𝑜𝑑𝑒1. 𝐶𝑀𝑜𝑑𝑒1) + 𝐸𝑋𝑃(−𝛽𝑀𝑜𝑑𝑒2. 𝐶𝑀𝑜𝑑𝑒2) + 𝐸𝑋𝑃(−𝛽𝑀𝑜𝑑𝑒3. 𝐶𝑀𝑜𝑑𝑒3) + 𝐸𝑋𝑃(−𝛽𝑀𝑜𝑑𝑒4. 𝐶𝑀𝑜𝑑𝑒4) in the beginning of analysis is using assumption of the power function, α =1 and the deterrence function, β = 0,00001. then, the proportion value of mode choice with those assumption is minus by the proportion of existing mode choice, in this case the value of proportion of existing mode choice is got from survey. the deviation value between model assumption and existing is absolute. then, add up civil and environmental science journal vol. 5, no. 1, pp. 017-025, 2022 20 all the values of the deviation and find the average. this average value we call it mae indicator, then the mae value divides with the average of existing mode choice proportion. the result is nmae. nmae is an error indicator of the model. the smaller the value, the model can be said to be close to the existing condition. to get the model close to the existing condition, the function value should be calibrated to get the minimum value of nmae. the calibration is using a tool from excel which is named excel solver. the method in excel solver that is used is grg nonlinear. the steps to use the excel solver are: 1. load the excel solver by option > file > add-in > add-in excel > to > add-in solver then tick the add-in solver option. 2. open the excel solver by clicking data > excel solver, then the excel solver window should appear. 3. choosing the nmae and put it in the “set objective” column. 4. choosing “min '' or minimal parameters to get the smallest possibilities of nmae value. 5. choosing the function value (power or deterrence function) and put it in the “by changing variable cells” column that soon will change by itself because of the analysis. in this step, the function values are calibrated. 6. choosing “grg nonlinear” method of solving in the “solving method” column. 7. final step, click on the “solve” to find the calibrated value of difference or power function, 8. after the analysis completed, the function value will be changed and the value will be used in the model or the value has been calibrated. 3. result and discussion 3.1. number of samples defining the number of samples in this research is using the slovin formula. the population being used is the population of public transportation users in tulungagung. the number of samples is based on average daily passenger [7] but in this research is used average annual passenger which give the same result like average daily passenger. the average of annual passenger number of public transportation users in tulungagung are 2.417.401. e value or error value is 10% and the number of samples are: 𝑛 = 𝑁 1 + 𝑁𝑒 2 = 2417401 1 + 2417401(0.1)2 = 100 𝑠𝑎𝑚𝑝𝑙𝑒 from slovin formula we got 100 minimum samples. but, in this research we used 200 samples, in case to avoid invalidity. table 2. generalised cost of tulungagung-surabaya route o-d distance to toll gate (km) toll road distance (km) bus ticket toll cost travel time (hours) car car bus tulungagungsurabaya 4.5 152.65 idr 50,000 idr 149,007 2.02 2.06 value of time vehicle operational cost vot x distances generalised cost car bus car bus car bus idr 18,269 idr 20,471 idr 2,780 idr 36,915 idr 42,132 idr 623,000 idr 93,000 3.2. generalised cost of tulungagung-surabaya route in the years of 2023rd, after all the sections connected, calculation of generalised cost is shown in the table 2. the generalised cost calculation divided into 3 calculation scenarios, i.e., gc tulungagung civil and environmental science journal vol. 5, no. 1, pp. 017-025, 2022 21 surabaya, tulungagung-kertosono-surabaya, and tulungagung-kediri-surabaya. travel speed assumption is 60 km/hours. table 3. generalised cost of tulungagung-kertosono-surabaya route o-d distance to toll gate (km) toll road distance (km) bus ticket toll cost travel time (hours) car car bus tulungagungkertosono-surabaya 64.6 80.75 rp30,000 rp85,060 2.62 3.16 value of time vehicle operational cost vot x distances generalised cost car bus car bus car express bus rp18,269 rp20,471 rp2,780 rp47,945 rp64,744 rp538,000 rp95,000 table 4. generalised cost of train and non-toll bus o-d travel distances (km) train ticket travel time (hours) value of time generalised cost train train train tulungagung-surabaya (train) 143 idr 18,000 5.11 idr 9,320 idr 66,000 o-d travel distances (km) bus ticket travel time (hours) value of time generalised cost bus bus bus tulungagung-surabaya (non-toll bus) 145.35 idr 25,000 3.63 idr 20,471 idr 100,000 3.3. characteristic of transportation user the characteristics of tulungagung-surabaya transportation users are obtained from a survey. we got 201 respondents and the characteristic are divided into sex, age, last education, job, salary, trip purposes, and vehicle ownership. sex characteristic of transportation user is dominated by female with 111 people and another 90 people is male. then, age characteristic is dominated by 21-30 years old with 149 people or 74% and the smallest user is 41-50 years old with 6 people or 6%. the last user education is dominated by bachelor degree with 102 people or 51% and the smallest user is master degree job with 7 people or 3% from total data. the job background is dominated by a student with 85 people or 42% and the smallest user is professional job with 4 people of 2% from total data. then, the user characteristic about salary is dominated by user with un-salary user or jobless with 63 people or 31% and the smallest user is 6-8 million rupiah per month with 7 people or 4% from total data next is about the purpose of the trip. it is dominated by family or social purpose with 65 people or 32% and the smallest respondent is about business trip with 14 people or 7% from total data. 3.4. mode choice using modal split in the beginning of the mode choice analysis is data grouping. the purpose of data grouping is for determining the total of origin-destination respondents. but, in this research, we do not use origin destination as a grouping method, because there is too much origin and destination that makes the data would not group. this research uses travel distance from home to the mode location and from the drop point to final destination. the data is categorical and makes it into the average value of distance. the distance and average are shown in table 5 below. civil and environmental science journal vol. 5, no. 1, pp. 017-025, 2022 22 table 5. data grouping categories distance categories average less than 3 km 3 km 3-5 km 4 km 5-7 km 6 km 7-10 km 8.5 km 10-12 km 11 km more than 12 km 12 km the next analysis is calculating extra cost that will add into the generalised cost in every mode. this additional cost is a cost for doing a trip from home to the mode location and from the drop point to final destination. the value of time being used is the value of time of the motorcycle. because, from the survey result, the most vehicle that has been used for a trip from home to the mode location and from the drop point to final destination is a motorcycle. travel speed assumption is about 40 km/hours then from it, we got the travel time. then, the generalised cost is travel time times value of time. table 6. extra cost for generalised cost categories of distance from origin to mode location (a) categories of distance from the drop point to destination (b) average of (a) vot (rp/minutes) travel time (minutes) vot x tt (a) avera ge of (b) travel time (minutes) vot x tt (b) 10-12 km 10-12 km 11 221.51 16.5 idr 3,655 11 16.5 idr 3,655 10-12 km 5-7 km 11 221.51 16.5 idr 3,655 6 9 idr 1,994 10-12 km 7-10 km 11 221.51 16.5 idr 3,655 8.5 12.75 idr 2,824 10-12 km less than 3 km 11 221.51 16.5 idr 3,655 3 4,5 idr 997 3-5 km 10-12 km 4 221.51 6 idr 1,329 11 16.5 idr 3,655 3-5 km 3-5 km 4 221.51 6 idr 1,329 4 6 idr 1,329 3-5 km 5-7 km 4 221.51 6 idr 1,329 6 9 idr 1,994 3-5 km 7-10 km 4 221.51 6 idr 1,329 8.5 12.75 idr 2,824 3-5 km less than 3 km 4 221.51 6 idr 1,329 3 4.5 idr 997 3-5 km more than 12 km 4 221.51 6 idr 1,329 12 18 idr 3,987 5-7 km 10-12 km 6 221.51 9 idr 1,994 11 16.5 idr 3,655 5-7 km 3-5 km 6 221.51 9 idr 1,994 4 6 idr 1,329 5-7 km 5-7 km 6 221.51 9 idr 1,994 6 9 idr 1,994 5-7 km 7-10 km 6 221.51 9 idr 1,994 8.5 12.75 idr 2,824 5-7 km less than 3 km 6 221.51 9 idr 1,994 3 4.5 idr 997 5-7 km more than 12 km 6 221.51 9 idr 1,994 12 18 idr 3,987 7-10 km 10-12 km 8,5 221.51 12.75 idr 2,824 11 16.5 idr 3,655 7-10 km 3-5 km 8,5 221.51 12.75 idr 2,824 4 6 idr 1,329 7-10 km 5-7 km 8,5 221.51 12.75 idr 2,824 6 9 idr 1,994 7-10 km 7-10 km 8,5 221.51 12.75 idr 2,824 8.5 12.75 idr 2,824 7-10 km more than 12 km 8,5 221.51 12.75 idr 2,824 12 18 idr 3,987 less than 3 km 10-12 km 3 221.51 4,5 idr 997 11 16.5 idr 3,655 less than 3 km 3-5 km 3 221.51 4,5 idr 997 4 6 idr 1,329 less than 3 km 5-7 km 3 221.51 4,5 idr 997 6 9 idr 1,994 less than 3 km 7-10 km 3 221.51 4,5 idr 997 8.5 12.75 idr 2,824 less than 3 km less than 3 km 3 221.51 4,5 idr 997 3 4,5 idr 997 more than 12 km 10-12 km 12 221.51 18 idr 3,987 11 16.5 idr 3,655 more than 12 km 3-5 km 12 221.51 18 idr 3,987 4 6 idr 1,329 more than 12 km 5-7 km 12 221.51 18 idr 3,987 6 9 idr 1,994 more than 12 km 7-10 km 12 221.51 18 idr 3,987 8.5 12.75 idr 2,824 more than 12 km less than 3 km 12 221.51 18 idr 3,987 3 4.5 idr 997 more than 12 km more than 12 km 12 221.51 18 idr 3,987 12 18 idr 3,987 the extra cost could be a factor for a mode choice. research in barcelona stated if extra cost influences the mode choice. when travel cost for car increase, there is a probability for rail based transportation increase by a passenger than a car [8] civil and environmental science journal vol. 5, no. 1, pp. 017-025, 2022 23 the extra cost above will be added into the generalized cost in every scenario. for example, the 3rd scenarios said “if toll-bus uses combination route tulungagung to kertosono without toll road and kertosono to surabaya uses toll road”, then the generalised cost used is generalised cost for tulungagung-kertosono-surabaya like table 3 above. then, add the extra cost for each group data. details about the calculation are shown below. ● the average origin to the mode location (a) = 11 km ● vot = idr 222/minute ● average travel time (40 km/jam) = 16.5 minutes ● vot x travel time (a) = idr 3,655 ● the average distance from drop point to destination (b) = 6 km ● average travel time (40 km/jam) = 9 minutes ● vot x travel time (b) = idr 1,994 according to table 3, the generalised cost of every mode is shown below. ● generalised cost toll bus = idr 95,000 ● generalised cost non-toll bus = idr 100,000 ● generalised cost car = idr 538,000 ● generalised cost train = idr 66,000 with extra cost, the final generalised cost is shown below ● generalised cost toll bus + extra cost = idr 100,649 ● generalised cost non-toll bus + extra cost = idr 105,649 ● generalised cost car + extra cost = idr 543,649 ● generalised cost train + extra cost = idr 71,649 calculation on the above is just for one data in one scenario. there are 201 respondents times 8 scenarios, so there are 1500 results from a calculation like the above. the value of generalised cost + extra cost on the above later will be used to determine the model of mode choice. first, we need to determine the value of power (α) and difference (β) function. use assumption with the power function (α) is 1 and the difference function (β) is 0.0001. the reason behind this assumption that there is no effect from the differentiation of generalised cost. then, the model is shown below. 1. power function (α) 𝑃𝑡𝑜𝑙𝑙𝑏𝑢𝑠 = 𝐺𝐶𝑡𝑜𝑙𝑙𝑏𝑢𝑠−𝛼 𝑡𝑜𝑙𝑙𝑏𝑢𝑠 (𝐺𝐶𝑡𝑜𝑙𝑙𝑏𝑢𝑠−𝛼 𝑡𝑜𝑙𝑙𝑏𝑢𝑠 + 𝐺𝐶𝑛𝑜𝑛𝑡𝑜𝑙𝑙𝑏𝑢𝑠−𝛼 𝑛𝑜𝑛𝑡𝑜𝑙𝑙𝑏𝑢𝑠𝑠 + 𝐺𝐶𝑐𝑎𝑟−𝛼 𝑐𝑎𝑟 + 𝐺𝐶𝑡𝑟𝑎𝑖𝑛−𝛼 𝑡𝑟𝑎𝑖𝑛) 𝑃𝑡𝑜𝑙𝑙𝑏𝑢𝑠 = 𝑅𝑝 100,649−1 (𝐼𝐷𝑅 100,649−1 + 𝐼𝐷𝑅 105,649−1 + 𝐼𝐷𝑅 543,649−1 + 𝐼𝐷𝑅 71,649−1) = 0.11772 = 11.7% 2. deterrence function (β) 𝑃𝑡𝑜𝑙𝑙𝑏𝑢𝑠 = 𝐸𝑋𝑃(−𝛽𝑡𝑜𝑙𝑙𝑏𝑢𝑠. 𝐺𝐶𝑡𝑜𝑙𝑙𝑏𝑢𝑠) 𝐸𝑋𝑃(−𝛽𝑡𝑜𝑙𝑙𝑏𝑢𝑠. 𝐺𝐶𝑡𝑜𝑙𝑙𝑏𝑢𝑠) + 𝐸𝑋𝑃(−𝛽𝑛𝑜𝑛𝑡𝑜𝑙𝑙𝑏𝑢𝑠. 𝐺𝐶𝑛𝑜𝑛𝑡𝑜𝑙𝑙𝑏𝑢𝑠) + 𝐸𝑋𝑃(−𝛽𝑐𝑎𝑟. 𝐺𝐶𝑐𝑎𝑟) + 𝐸𝑋𝑃(−𝛽𝑡𝑟𝑎𝑖𝑛. 𝐺𝐶𝑡𝑟𝑎𝑖𝑛) 𝑃𝑡𝑜𝑙𝑙𝑏𝑢𝑠 = 𝐸𝑋𝑃(−0.00001. 𝐼𝐷𝑅 100,649) 𝐸𝑋𝑃(−0.00001. 𝐼𝐷𝑅 100,649) + 𝐸𝑋𝑃(−0.00001. 𝐼𝐷𝑅 105,649) + 𝐸𝑋𝑃(−0.00001. 𝐼𝐷𝑅 543,649) + 𝐸𝑋𝑃(−0.00001. 𝐼𝐷𝑅 71,649) = 0.3030 after the value of the two functions found, those function should be calibrated so that the model should be fit with the existing condition. in this research, the calibration method uses normalised mean absolute error or nmae. then, step for calibrating is shown below: 1. change the existing mode choice number form into percentage. 2. subtract the proportion of existing mode choice with the model proportion, (β)=0,0001 and (α)=1. the result should be an absolute number. 3. all of the result from that subtraction is added and find the mean, it is called mae. 4. calculate the average of existing mode choice proportion. civil and environmental science journal vol. 5, no. 1, pp. 017-025, 2022 24 5. determine the nmae value by dividing the mae with the average number of existing mode choice proportion. the proportion value from two functions is calibrated so that the model should resemble the existing condition. the calibration analysis is using excel solver, as mentioned above. for the calibration of power function (α) ● mean absolute error (mae) (α) = 0.1321 ● mean | y-ŷ | (α) = 0.2500 ● nmae power function (α) = 0.5284 for the calibration of deterrence function (β): ● mean absolute error (mae) (β) = 0.1793 ● mean | y-ŷ | (β) = 0.1346 ● nmae deterrence function (β) = 1.3328 from the calibration calculation, we have to choose the smallest nmae value, because the value closer to 0, the better model. the nmae from power function value (0.5284) above is the smallest one. so, we can get a conclusion if the power function is more resemble the existing condition, then a difference function. so, the mode choice model for tulungagung to surabaya due to toll road are: 𝑃𝐵𝑢𝑠 𝑃𝑎𝑡𝑎𝑠 = 𝐺𝐶𝐵𝑢𝑠𝑃𝑎𝑡𝑎𝑠−0.01987 (𝐺𝐶𝐵𝑢𝑠𝑃𝑎𝑡𝑎𝑠−0.01987 + 𝐺𝐶𝐵𝑢𝑠 𝑁𝑜𝑛𝑇𝑜𝑙−3.07143 + 𝐺𝐶𝑀𝑃−0.03891 + 𝐺𝐶𝐾𝐴−0.00032) 𝑃𝐵𝑢𝑠𝑁𝑜𝑛𝑇𝑜𝑙 = 𝐺𝐶𝐵𝑢𝑠𝑁𝑜𝑛𝑇𝑜𝑙−3.07143 (𝐺𝐶𝐵𝑢𝑠𝑃𝑎𝑡𝑎𝑠−0.01987 + 𝐺𝐶𝐵𝑢𝑠 𝑁𝑜𝑛𝑇𝑜𝑙−3.07143 + 𝐺𝐶𝑀𝑃−0.03891 + 𝐺𝐶𝐾𝐴−0.00032) 𝑃𝑀𝑃 = 𝐺𝐶𝑀𝑃−0.03891 (𝐺𝐶𝐵𝑢𝑠𝑃𝑎𝑡𝑎𝑠−0.01987 + 𝐺𝐶𝐵𝑢𝑠 𝑁𝑜𝑛𝑇𝑜𝑙−3.07143 + 𝐺𝐶𝑀𝑃−0.03891 + 𝐺𝐶𝐾𝐴−0.00032) 𝑃𝐵𝐾𝑒𝑟𝑒𝑡𝑎𝐴𝑝𝑖 = 𝐺𝐶𝐾𝐴−0.00032 (𝐺𝐶𝐵𝑢𝑠𝑃𝑎𝑡𝑎𝑠−0.01987 + 𝐺𝐶𝐵𝑢𝑠 𝑁𝑜𝑛𝑇𝑜𝑙−3.07143 + 𝐺𝐶𝑀𝑃−0.03891 + 𝐺𝐶𝐾𝐴−0.00032) 4. conclusions a. the socio-economy characteristics of respondents for the tulungagung-surabaya route are dominated by female sex with a percentage of 55%, ages between 21-30 years with a percentage of 74%, the last education is d4/bachelor with a percentage of 51%, the type of work is a student with a percentage of 42%, dominated by people who have no income, because the average student with a percentage of 31%, the purpose of traveling is for family/social needs with a percentage of 32%, and as many as 93% of mode users surveyed own a motorized vehicle. transportation mode that been used are travel time and travel cost. the socio-economy condition is just for how is the user characteristic and not affected the model. b. the model obtained is using the power function with given nmae value of 0.5284 with the following equation: 𝑃𝐵𝑢𝑠 𝑃𝑎𝑡𝑎𝑠 = 𝐺𝐶𝐵𝑢𝑠𝑃𝑎𝑡𝑎𝑠−0.01987 (𝐺𝐶𝐵𝑢𝑠𝑃𝑎𝑡𝑎𝑠−0.01987 + 𝐺𝐶𝐵𝑢𝑠 𝑁𝑜𝑛𝑇𝑜𝑙−3.07143 + 𝐺𝐶𝑀𝑃−0.03891 + 𝐺𝐶𝐾𝐴−0.00032) 𝑃𝐵𝑢𝑠𝑁𝑜𝑛𝑇𝑜𝑙 = 𝐺𝐶𝐵𝑢𝑠𝑁𝑜𝑛𝑇𝑜𝑙 −3,07143 (𝐺𝐶𝐵𝑢𝑠𝑃𝑎𝑡𝑎𝑠 −0.01987 + 𝐺𝐶𝐵𝑢𝑠 𝑁𝑜𝑛𝑇𝑜𝑙 −3.07143 + 𝐺𝐶𝑀𝑃 −0.03891 + 𝐺𝐶𝐾𝐴 −0.00032 ) 𝑃𝑀𝑃 = 𝐺𝐶𝑀𝑃−0,03891 (𝐺𝐶𝐵𝑢𝑠𝑃𝑎𝑡𝑎𝑠 −0.01987 + 𝐺𝐶𝐵𝑢𝑠 𝑁𝑜𝑛𝑇𝑜𝑙 −3.07143 + 𝐺𝐶𝑀𝑃 −0.03891 + 𝐺𝐶𝐾𝐴 −0.00032 ) 𝑃𝐵𝐾𝑒𝑟𝑒𝑡𝑎𝐴𝑝𝑖 = 𝐺𝐶𝐾𝐴−0,00032 (𝐺𝐶𝐵𝑢𝑠𝑃𝑎𝑡𝑎𝑠 −0.01987 + 𝐺𝐶𝐵𝑢𝑠 𝑁𝑜𝑛𝑇𝑜𝑙 −3.07143 + 𝐺𝐶𝑀𝑃 −0.03891 + 𝐺𝐶𝐾𝐴 −0.00032 ) civil and environmental science journal vol. 5, no. 1, pp. 017-025, 2022 25 acknowledgements we say thank you to department of transportation of tulungagung and pt kai which allowed us to collect data from them and give us permission to do survey. references [1] otomotifnet.com (2021), tol kediri-tulungagung beroperasi akhir 2023, lokasi exit tol di sini, https://otomotifnet.gridoto.com/read/232684795/tol-kediri-tulungagung-beroperasi-akhir2023-lokasi-exit-tol-di-sini [2] kusumawati, a. i. (2019). probabilitas pengguna moda bus dan kereta api pada rute cirebon jakarta pasca pembangunan tol cipali dengan pendekatan model logit biner. jurnal ilmiah indonesia, 4(5), 1–12 aditya, v. s., mariam, t., krishna rao, k. v., 2017. mode shift behaviour of commuters due to the introduction of new rail transit mode. transportation research procedia 25, 2603-2618. [3] monczka, r., trent, r. and handfield, r. (2005), purchasing and supply chain management, thomson south-western, mason, oh. [4] meixell, m. j., & norbis, m. (2008). a review of the transportation mode choice and carrier selection literature. the international journal of logistics management, 19(2), 183–211. [5] kløjgaard, m. e., bech, m., & søgaard, r. (2012). designing a stated choice experiment: the value of a qualitative process. journal of choice modelling, 5(2), 1–18. [6] sjafruddin, a., lubis, h. a. r. s., & setiawan, b. (2016). model pemilihan moda angkutan penumpang pesawat terbang dan kapal cepat dengan data sp (stated preference) (studi kasus: rute palembang batam). journal of civil engineering. [7] tamin, ofyar z., (1997), perencanaan & pemodelan transportasi, itb, bandung. [8] b. artanto dan m. s. surbakti, “analisa probabilitas perpindahan moda transportasi dari bus ke kereta api rute medan-kotapinang menggunakan metode stated preference,” j. rekayasa konstr. mek. sipil, vol.1, no.2, pp. 95–107, 2018. [9] j. asensio, “transport mode choice by commuters to barcelona’s cbd,” urban stud., 2002 civil and environmental science journal vol. 4, no. 2, pp. 202-207, 2021 202 bali cattle cultivation in ayunan village abiansemal district, badung ni made ayu gemuh rasa astiti1*, i wayan wesna astara1, i gusti agung putu eryani1 1 warmadewa university, denpasar, 80235, indonesia1 *ayugemuh@gmail.com received 22-07-2021; accepted 17-09-2021 abstract. ayunan village, is located in abiansemal sub-district, badung regency, bali. bali cattle are germplasm that must be preserved, for that we are collaborating with the bali karang ayu and karya laksana cattle groups in ayunan village. the maintenance of bali cattle in partners is very constrained by capital, feed and management of balinese cattle maintenance is not carried out professionally because it is managed in a family, traditional way and is not a main source of livelihood. bali cattle maintenance is only a sideline to fill spare time on the sidelines of farming time. the management of cow dung and manure has not been managed properly, which should still be managed into organic fertilizer, sold to farmers so that it can increase the income of farmers, so the solution we offer is to provide assistance and consultation as well as demonstration plots regarding good and correct management of balinese cattle rearing. to increase bali cattle production. the results of this community service activity can increase production, productivity as well as produce organic fertilizer from cow dung that can be sold so as to increase the income of balinese cattle farmers in the two bali cattle groups that we partner with. keywords: bali cattle, ecotourism, organic fertilizer, partner group 1. introduction ayunan village, is located in abiansemal sub-district, badung regency, bali. this village is about 20 km to the north from denpasar city, to the tourist attraction village of sangeh and taman ayun or about 3 kilometers from the village of mengwi taman ayun, where the population is more dominant as farmers and raise balinese cattle. the pattern of rearing bali cattle is still traditional and as a sideline between farming time [1]. ayunan village has the potential to be developed as a tourism village for rearing and using balinese cattle for plowing (traditional metekap). 1 cite this as: astiti, n.m.a.g.r, astara, i.w.w & eryani, i.g.a.p (2021). bali cattle cultivation in ayunan village abiansemal district, badung. civil and environmental science journal (civense), 4(2), 202-207. doi: https://doi.org/10.21776/ub.civense.2021.00402.10 civil and environmental science journal vol. 4, no. 2, pp. 202-207, 2021 203 figure 1. the atmosphere of the village of ayunan abiansemal badung. bali cattle are germplasm that must be preserved which is supported by government policies. this is a golden opportunity for cattle breeders in bali, because bali is one of the sources of bali cattle breeds and the only area that is believed to have pure bali cattle genetics, [2]. more efficient marketing will be able to provide higher prices for farmers. thus, a more efficient marketing system must absolutely be considered, so that cattle farms are able to provide higher additional income for farmers. this increase in income will encourage them to raise more cattle. in addition, it will encourage farmers to carry out maintenance in a better way, [3, 15]. the results of discussions with potential partners, it was found that several production distribution processes including the procurement of production facilities at partner locations can be said to have no problems. the location which tends to be close to the city center and sub-district center as well as the government's increasing attention to road infrastructure is very supportive or makes the distribution process not an obstacle. the cattle rearing management process that has occurred in the partners has taken place although it is still very simple. planning for the production of organic fertilizer from cow dung has already taken place, but that's just the planning limit has not been implemented. direct observations in the karang ayu and karya livestock groups, such as in ayunan village, abiansemal district, show that partner bali cattle rearing activities are very constrained by capital, feed, cattle rearing management, processing and manure drainage and how to increase farmers' income from bali cattle rearing business [16]. the main problems and will be the focus of problem solving are the low management ability of bali cattle, low productivity in processing livestock manure into organic fertilizer and low business efficiency and business sustainability of organic fertilizer products from livestock manure. the results of this activity are expected to increase production and productivity and produce organic fertilizer from cow dung that can be sold so as to increase the income of balinese cattle farmers in ayunan village. based on observations that have been made to partner livestock groups, for the sake of their sustainability and existence it is very feasible to receive continuous guidance and assistance from higher education institutions so that they can increase the capacity, quality and income of balinese cattle farmers through processing superior balinese cattle products in ayunan village, coaching and improving management of balinese cattle maintenance, processing of cow dung into organic fertilizer as well as marketing of organic fertilizer products and other interrelated aspects that are able to provide increased income for farmers, with increasing incomes for automatic breeders, balinese cattle breeders will become prosperous. 2. materials and methods the descriptive research methodology was employed in this study to describe the extent of bali cattle cultivation in ayunan village abiansemal district, badung. furthermore, descriptive research. is civil and environmental science journal vol. 4, no. 2, pp. 202-207, 2021 204 defined as study conducted for conditions or other objects and the results of which are delivered in the form of a research report. one of the descriptive research approaches that has been employed is: a) according to [17] the survey method is a study that tries to acquire data by assessing samples from the accessible population. in the field, by observing, measuring, and recording data. b) the interview method is a meeting of two persons to exchange information and ideas through direct question and response between the researcher and the responder, with the goal of concentrating the meaning on a certain issue [18] and obtaining in-depth data, information, and facts. based on the identification of the problems faced by partners and the solutions offered, the method of implementing the activities: 1. provide assistance and consultation regarding the management of good and correct maintenance of bali cattle to increase production of bali cattle, both for fattening and breeding. 2. assistance in the preparation of rations related to ration raw materials, so it is hoped that the provision of optimal rations can increase bali cattle production. 3. assist and practice the provision of high nutritional value animal feed so that cattle grow optimally. 4. procurement of lawn mowers, grass holders, hoes and scops so as to speed up farmers' search for forage for livestock. 5. counselling and assistance on the use of digital marketing. 3. results and discussion. after conducting several meetings with partners, an agreed schedule of activities to be carried out was agreed. partners propose several activity schedules that are tailored to their activities, so that the training does not interfere with the activities of partners. the implementation of community service activities for raising cattle properly and correctly and providing bali cattle feed in partner livestock groups is carried out in several stages so that both breeders and cattle do not experience stress [12, 14]. based on observations that have been made to partner livestock groups, for the sake of their sustainability and existence it is very feasible to receive continuous guidance and assistance from higher education institutions so that they can increase the capacity, quality and income of balinese cattle farmers through processing superior balinese cattle products in ayunan village, coaching and improving management of balinese cattle maintenance, processing of cow dung into organic fertilizer as well as marketing of organic fertilizer products and other interrelated aspects that are able to provide increased income for farmers, with increasing incomes for automatic breeders, balinese cattle breeders will become prosperous. 1. in relation to the management of partner bali cattle breeding, it can be described the condition of each partner: bali cattle rearing management in partners is not carried out professionally because it is managed in a family and traditional way and is not the main source of livelihood, bali cattle rearing is only a sideline filler free time on the sidelines of farming time, which now mostly uses labor, both in land cultivation, seeding, and harvesting. likewise, related to bookkeeping such as diaries, cash books, calculation of production costs, calculation of profit or loss are not yet available properly. regarding hr management, it is still unclear where the division of work is not clear between one another. 2. partners do not yet have good cattle rearing system due to limited knowledge and capabilities of farmers. 3. management of cow dung and manure has not been managed properly, which should still be managed into organic fertilizer and sold to farmers so that it can increase the income of cattle farmers. 4. the management of cow dung and manure has not been managed properly, which should still be managed into organic fertilizer and sold to farmers so that it can increase the income of cattle farmers. civil and environmental science journal vol. 4, no. 2, pp. 202-207, 2021 205 5. the facilities owned by partners are in the form of makeshift cowsheds. partner problem 1. based on the results of observations on the two partners, there are several problems that become obstacles including: the division of work in cattle rearing is not clear because the management of cattle rearing is carried out in a modest manner and uses family workers and cattle rearing only as a sideline to fill spare time on the sidelines of farming. so, it is not the main business or livelihood of the partners. 2. owned equipment such as a grass sickle, a basket where the grass has run out of economic life. partners cannot afford the equipment, so often in the search for animal feed takes a long time to slash. 3. there is no cow dung drain, which causes odor and the cowshed becomes dirty. 4. this cow dung has not been processed as organic fertilizer which can provide additional income for farmers, so it needs the help of tools to process cow dung into organic fertilizer. need to be given knowledge of marketing agricultural products so that farmers do not focus on the field. solution the purpose of this program is to help partners "karang ayu and karya laksana" in terms of overcoming the problems faced related to business development. from the problems that have been identified, the solutions for solving the problems offered are: 1. establishment and design of bali cattle rearing management. 2. preparation of work plans and socialization of bali cattle rearing management programs. 3. assist in the process of raising bali cattle. 4. procurement of some equipment that has been damaged such as sickles, baskets, shovels and buckets to facilitate the provision of cattle feed 5. dissemination of digital marketing in the covid-19 era. the stages of implementing the activities that have been planned can be described as follows. in this activity the team provided an explanation of good and proper cattle maintenance and feeding bali cattle feed. the form of science and technology given to partner 1 (coral ayu livestock group) and partner 2 (karya livestock farmers group), in general: a) provide an understanding of bali cattle rearing management through intensive socialization of b) pppud activities to equalize perceptions and strengthen partner group institutions. c) provide cattle rearing management training to the community, especially to partner groups. so far, there is no public knowledge, especially on marketing issues related to natural resources cultural tourism [9, 11]. d) provide training on making organic fertilizer in partner groups from cow dung. e) provide socialization to partner groups related to the importance of packaging and labeling of organic fertilizer products produced. f) provide socialization to partner groups related to the system of management and arrangement of natural resources as well as complementing natural resource facilities and the preparation of governance and management of natural resource tourism. g) provide materials, socialization, and understanding of natural resource tourism supporting facilities, english, handicrafts, monitoring activities and promotional activities. provide an understanding of the importance of promoting products produced through provincial level events even [10, 13] civil and environmental science journal vol. 4, no. 2, pp. 202-207, 2021 206 figure 2. fumigation activity in cow shed 4. conclusion bali cattle cultivation in the swing village has been implemented well, almost 95% of farmers are responsible for their livestock. and the management of cow dung by drying has been done, farmers focus on production but have not been able to market their fertilizer products. it is suggested by farmers that the implementation of this pkm can continue, especially in the field of marketing, because farmers have not been able to sell their products, only able to process and produce fertilizers. acknowledgment the author would like to thank all those who have helped in completing this research reference [1] monografi dan data kependudukan desa ayunan kecamatan abiansemal, badung 2019 [2] astiti, nmagr; rukmini, ni ketut sri dan ni ketut mardewi. 2018. teknik budidaya sapi bali di desa selat badung. laporan pkm institusi universitas warmadewa denpasar [3] profil kemlompok tani ternak karang ayu. 2018. desa ayunan. kecamatan abian semal kabupaten badung. [4] astiti, ni made ayu gemuh rasa astiti. 2018. pengantar ilmu peternakan. warmadewa university press. denpasar. [5] astiti, ni made ayu gemuh rasa. 2018. sapi bali dan pemasarannya. warmadewa university press denpasar. [6] annonimous. 2008.teknologi, alat dan mesin peternakan. modul diklat teknis substantif peternakan tingkat dasar. teknologi peternakan dan alsin.dinas peternakan propinsi jawa barat. [7] astiti, nmagr, putri risa andriani dan nks rukmini. 2020. ateknik pemasaran sapi bali di kelompok ternak sari sedana. laporan pkm institusi universitas wamadewa, denpasar. [8] astiti, nmagr, nks rukmini dan putri risa andriani. 2019. utilization of fermented rice strow for bali cowfeed in the sari lestari. prociding of 2nd warmadewa research and development seminar. wards page 126-130. [9] astiti, n. m. a. g. r. (2018). sapi bali dan pemasarannya. jayapangus press books, i-106. [10] darmawi, d. (2011). pendapatan usaha pemeliharaan sapi bali di kabupaten muaro jambi. jurnal ilmiah ilmu-ilmu peternakan, 14-22. [11] sampurna, i. p., & suatha, i. k. (2010). pertumbuhan alometri dimensi panjang dan lingkar tubuh sapi bali jantan. jurnal veteriner, 11(1), 46-51. [12] widagdyo, k. g. (2017). pemasaran, daya tarik ekowisata, dan minat berkunjung wisatawan. esensi: jurnal bisnis dan manajemen, 7(2), 261-276. civil and environmental science journal vol. 4, no. 2, pp. 202-207, 2021 207 [13] aryunda, h. (2011). dampak ekonomi pengembangan kawasan ekowisata kepulauan seribu. jurnal perencanaan wilayah dan kota, 22(1), 1-16. [14] oktavianie, d. a. (2018). breeding engineering, producing and marketing laboratory mice (mus musculus) as animal research. journal of innovation and applied technology, 4(2), 727-730. [15] sardjadidjai, r., & sitorus, s. r. p. (1995). transmigration program with animal ilushandry model in indonesia. buletin peternakan= bulletin of animal science (special edition), (1995). [16] sidebang, a. a., sembiring, i., mirwandhono, e., & tafsin, m. (2017). marketing efficiency analysis of beef cattle in animal market suka village tigapanah subdistrict karo district. jurnal peternakan integratif, 5(1). [17] azuar juliandi, dkk, metodologi penelitian bisnis, medan: umsu press, 2014. [18] sugiyono, (2014) metode penelitian pendidikan pendekatan kuantitatif, bandung: alfabeta, 123. civil and environmental science journal vol. ii, no. 02, pp. 076-083, 2019 76 el-nino effect on reservoir volumetric (a case study of the batujai dam on the island of lombok) i wayan yasa1*, m bisri2, m solichin2, ussy andawayanti2 1civil engineering faculty, mataram university, west nusa tenggara, indonesia 2water resources engineering department, universitas brawijaya, malang, 65145, indonesia yasaiwayan68@gmail.com received 16-07-2019; revised 31-07-2019; accepted 20-08-2019 abstract. el-nino has been occurred from 1952 to 2016 with the types of weak, medium, strong and very strong. the event of el-nino has significant impact on all aspects of economy, social, industry and agriculture. there is a decrease in the quantity of water resources such as in the reservoir where the reservoir inflow becomes very small and the water outflow becomes high. at the event of very strong el-nino is occurred some of the reservoirs will dry. the aim of the research is to investigate the deficit capacity of the reservoir in the event of el-nino. the data analyzed in this article were the volume of the half-month reservoir, especially in the event of el-nino events. the analysis of frequency deficit probability was using weibull probability and log pearson type iii distribution. the results show significant decrease in reservoir water volume over a very long-time period. the reservoir volume never reached maximum water level and persists for almost one year. the deficit of reservoir volumes reached was 16,01x106 m3, 18.64x106 m3, and 21,07x103 m3 for weak, moderate, and very strong el-nino, respectively. keywords: el-nino, impact, reservoir, volumetric 1. introduction climate is the average quantity of weather physical phenomena, which is the extreme variation of seasons that take place locally, regionally or globally. in a certain area the weather can change rapidly from day to day even from hour to hour. these changes may include, among other things, the occurrence of temperature changes, the phenomenon of the shift in the occurrence of precipitation, the phenomenon of changes in wind intensity and the accumulation of clouds. climate change with all its causes has factually occurred at the local, regional and global. the increasing of emissions and greenhouse gas (ghg) concentrations resulted in global warming, followed by rising sea levels due to the expansion and melting of ice in the polar regions [1]. the rising of sea levels will increase the energy stored in the atmosphere leading to climate change such as el-nino and la-nina [3, 4]. the phenomenon of el-nino and la-nina is very influential on weather conditions/climate in indonesian region which has a geographical archipelago. the air/wind circulation between asian and australian continents and pacific and atlantic oceans is quite high which placed indonesia under a highly vulnerable to the effects of climate change. this is indicated by the occurrence of various disaster events. mailto:yasaiwayan68@gmail.com mailto:yasaiwayan68@gmail.com civil and environmental science journal vol. ii, no. 02, pp. 076-083, 2019 77 as it is located in the eastern part of indonesia west nusa tenggara province is very vulnerable to the el-nino phenomenon. with almost 80% area is covered by dry land problems of water resources provision become the main priority problem to be solved. in such efforts the government has made a breakthrough by building facilities and infrastructure of water resources supplier. currently the government has built 9 reservoirs which is three of the reservoirs were built in lombok and six reservoirs in sumbawa. the most common problem identified in these six reservoirs is that they are reservoir suffers drought during el-nino events. in the worst case at the peak of dry season, the capacity of some reservoirs below the dead storage. the inflow component includes river flows and rainfall, while the outflow component is including water for irrigation, fresh water and lost water from reservoir. the occurrence of climate change in the form of el-nino affects the water volume of the reservoir, thus affecting the operation pattern of the reservoir. the deficit of water reservoir at the time of el-nino is crucially important to anticipate the water supply condition, which may also be used indicate the occurrence of el-nino. there are two main purpose of this research: firstly, to identify the decrease of deficit volumetric based on the type of el-nino. secondly to provide information related to the return period of deficit reservoirs volumetric. 2. material and method the study was conducted at batujai dam, west nusa tenggara province figure 1. map of reservoir batujai location on lombok island batujai reservoir is built on penujak river which flows from the slopes of kundo and empties into the lombok strait with a river length of 54 km and a catchment area of 169 km2. penujak river has characteristic of a large difference in river flow between dry and rainy seasons. in the rainy season the average monthly discharge can reach tens of cubic meters per second so it is a wastable potential to the sea, whereas in the dry season the average monthly debit can reach 0.1 m3/s or even less. the gross capacity reaches the value of 25x106 m3, effective 23 x106 m3 and minimum capacity 1.4 x106m3. the phenomenon of global climate change is caused by the warming of the surface temperature of the eastern pacific waters. el-nino occurs in 2-7 years and lasts up to 12-15 months [7]. the characteristic of el civil and environmental science journal vol. ii, no. 02, pp. 076-083, 2019 78 nino is the periodic rise in temperatures in the pacific region and the increased air pressure differences between darwin and tahiti [5]. one of the main challenges in dealing with climate change is how to link knowledge of impact with the adaptation actions [9]. in indonesia, el-nino events occur almost throughout the region and become a routine problem in the provision of water resources. various anticipations have been made but often fail. the seasonal change event of el-nino has a very strong effect on drought events. furthermore, chuthamat [3] reported that drought events can occur regionally and extensively covering several parts of the state. figure 2 shows climate change has occurred since 1950 until the year 2017 in the form of el-nino and la-nina events. el-nino is a low-intensity rainfall below average and la-nina is a high above average rainfall. el-nino and la-nina were reviewed based on anomalies of sea surface temperature (sst anomalies). events are defined as 5 consecutive overlapping 3-month periods at above the +0.5° anomaly for warm events (el-nino) and at or below the -0.5o anomaly for cold (la-nina). there are several types of el-nino and la-nina which include weak (with a 0.5 to 0.9 sst anomaly), moderate (1.0 to 1.4), strong (1.5 to 1.9) and very strong (≥ 2.0) [9]. : el-nino : la-nina figure 2. el-nino and la-nina years recently, the potential impacts of climate change have been a major concern in the management of water resources. climate change is indicated by the increasing of temperature of the earth's surface with a more extreme tendency [8]. bhuvaneswari [2] reported that el-nino has occurred since 1972, 1982, 1987, 1991, 1997, 2002 and 2004. el-nino events are very influential on the hydrological process with the occurrence of a very significant flow reduction. furthermore, keener [5] stated that el-nino has implications for the increasing uncertainty of water supply that affects the regulation of the allocation of water resources into complexes. one of the ways in which the construction of reservoirs is expected can be used as an anticipatory effort [7]. civil and environmental science journal vol. ii, no. 02, pp. 076-083, 2019 79 log 𝑋 = 𝐿𝑜𝑔 𝑋 ̅̅ ̅̅ ̅̅ ̅̅ ̅ + 𝑘 × 𝑆log 𝑥 𝐿𝑜𝑔 𝑋 ̅̅ ̅̅ ̅̅ ̅̅ ̅ = 1 𝑁 ∑ 𝐿𝑜𝑔 𝑋𝑛𝑖=1 . 𝑆log 𝑥 = √ ∑ ( 𝐿𝑜𝑔 𝑋 − 𝐿𝑜𝑔 𝑋̅̅ ̅̅ ̅̅ ̅̅ 𝑛𝑖=1 ) 2 𝑁 − 1 reservoir is a very important facility in the water supply system and has many functions to hold water during the rainy season. the reservoir function is not only limited to the physical side such as capacity and flow but also depends on the needs and operating patterns. further, shiau [8] noted that reservoir is an important facility in multi-sector water supply system with the main function is to regulate the fluctuating surface water flow. reservoirs have multipurpose uses, such as flood control, recreational activities, hydroelectric and water supply, which may conflict each other [9], water reservoir management must consider natural variability, especially climate change and land use change. in the analysis of the possibility of occurrence of a hydrologic event in future, statistical analysis is an important tool that can be used. statistical analysis has the advantage of using measurable hydrological data, therefore it is still considered to have good validity. some common frequency distribution equation used in hydrology include normal distribution, normal logs, gumbel, pearson and log pearson type iii. mean:  = − = i i i xn x 1 1 (1) standard deviation; ( )1 / 1 1 2 −             =   = = n nxx s i i n i ii (2) coefficient of variation: − = x s c v (3) skeweness :  = − − −− = n i is xx snn n c 1 3 3 )( )2)(1( (4) kurtusis :  = − − −−− = n i is xx snnn n c 1 4 4 )( )3)(2)(1( (5) furthermore, the magnitude of the reliable value of a hydrological even can be determined using the following can be equation. 1+ = n m p (6) where: p : probability n : amount of data. m : serial number of data the following equations are used to calculate the design deficit volumetric by the log pearson type iii method: (7) (8) (9) civil and environmental science journal vol. ii, no. 02, pp. 076-083, 2019 80 𝐶𝑠 = 𝑁 ∑ ( 𝐿𝑜𝑔 𝑋 − 𝐿𝑜𝑔 𝑋 ̅̅ ̅̅ ̅̅ ̅̅ ̅)3𝑛𝑖=1 ( 𝑁 − 1 )( 𝑁 − 2 )( 𝑆log 𝑥 ) 3 𝐿𝑜𝑔 𝑋 ̅̅ ̅̅ ̅̅ ̅̅ ̅ (10) where: log x : logarithm of data : the mean logarithm of data slog x : standard deviation from the data logarithm cs : coefficient of skewness k : frequency factor 3. results and discussion the weak el nino events occurred in 1994, 2004, 2005, 2006 and 2007. although those events were classified as weak but they have significant impact on water volume reservoir. the decrease in water volume of the reservoir occurs simultaneously and never reached the effective capacity over a long-time period. the largest decrease in reservoir volume occurred in december at 16.01x106 m3. decreasing the volume of the reservoir at the time of weak el-nino does not lead to the provision of irrigation water is significantly reduced. the reservoir volume can still provide water because inflow from the river is still available. the weak el-nino pattern almost shows the same trend from year to year. the reservoir volume is reduced more extreme for only 4 months but does not interfere with the operation of the reservoir. figure 3. the volumetric deficit of the reservoir at the time of weak el-nino in the case of moderate el-nino events the changes in reservoir volume are more extreme than the weak el-nino. the extreme decrease in reservoir volume starts from april to december. in this event the volume of the reservoir is always below the effective but not under the minimum storage. the reservoir deficit volume from the effectiveness limit reaches 16.67x106 m3, thus almost every el-nino event occurs. the decrease in reservoir volume occurs very extreme and has an impact on the fulfillment of irrigation water. the duration of the decrease in reservoir volume is quite long for almost 6 months. the pattern of occurrence of moderate el-nino shows the same pattern both time and reduced reservoir volume. the moderate el-nino event has occurred 5 times in 1991, 1992, 2002, 2003 and 2009. 0,00 5,00 10,00 15,00 20,00 25,00 30,00 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 m c m 1/2 month 1994 2004 2005 2006 2007 max volume efektif volume min volumevolume effective civil and environmental science journal vol. ii, no. 02, pp. 076-083, 2019 81 figure 4. the volumetric deficit of the reservoir at the time of moderate el-nino the strong el-nino event has occurred in the period 1982 1983, the period 19971998 and 2015. the impact of el-nino has caused a very extreme reservoir volume deficit. during the occurrence of elnino the water volume of the reservoir is under the effective volume of the reservoir. in 1983 and 2015 the deficit of reservoirs reached the minimum reservoir or dead storage. the maximum deficit of the reservoir from the effective crater is 21.07x106 m3. the decreasing rate of the reservoir volume is quite high with a long period of 9 months. if the el-nino occurs in the following years it will have an impact on the drought and affect the physical building of the reservoir. figure 5. the volumetric deficit of the reservoir at the time of very strong el-nino 0,00 5,00 10,00 15,00 20,00 25,00 30,00 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 m c m 1/2 month 1991 1992 2002 2003 2009 max volume efektif volume min volume 0,00 5,00 10,00 15,00 20,00 25,00 30,00 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 m c m 1/2 month 1982 1983 1998 2015 max volume efektif volume volume effective volume effective civil and environmental science journal vol. ii, no. 02, pp. 076-083, 2019 82 the return period indicates a magnitude of the occurrence likely to be equal of exceeds over that time span. return period are often used in water planning to determine the magnitude of the design discharge. in this study, the return period deficit of reservoir defects was analyzed for each el-nino type. some return period deficit reservoir defects include 1, 2, 5, 10, 20 and 50 years. the volumetric deficit of the reservoir for each el-nino event predicted using the log pearson type iii is shown in figure 6. it was clearly shown that on the 5-year period the deficit reservoir is large enough for all el-nino types. reservoir deficit are strong el-nino of 18.98x106 m3, moderate 11.24 x 106 m3 and weak 13.13 x106 m3. while the extreme drought of the reservoir is going to be occurred at the time of the 10 periods. figure 6. return period deficit of reservoir volumetric 4. conclusions the el-nino events may have a significant decrease in deficit reservoirs where reservoir volumetric never reaches an effective storage volume. during the el-nino event, the strong deficit of the reservoir volume can reach under the volume of the dead storage. the maximum deficit volume of the reservoirs in each type el-nino is 16.01x103 m3, 18.99 x103 m3and 21.07 x103 m3 for week, moderate and strong el-nino respectively. the length of time for el-nino events are different, where el-nino moderate and el-nino strong are longer than weak el-nino. probability occurring el-nino events that cause reservoir volume to reach the minimum volume that is in the repeat period above 5 years 5. acknowledgments the authors wish to thank department of public works west nusa tenggara province for data throughout the study. we do appreciate to anonymous reviewers and editor for their valuable comments and suggestions. 6. references [1] ahidul i, thian y.g. 2015 potential combined hydrologic impacts of climate change and el niño southern oscillation to south saskatchewan river basin, journal of hydrology [2] bhubaneswar k., geethalakshmi v. 2013 the impact of el niño/southern oscillation on hydrology and rice productivity in the cauvery basin, india: application of the soil and water assessment tool, weather and climate extremes [3] chuthamat c., adebayo j. adeloye, and soundharajan b.s. 2016 inflow forecasting using artificial neural networks for reservoir operation, iahs, 373, 209–214 [4] jie-lun c, yu-shiue t. 2012 reservoir drought prediction using support vector machines, applied mechanics and materials vol. 145 (2012) pp 455-459 [5] keener v.w., feyereisen g.w., lall u., jones j.w., bosch d.d., r. lowrance r. 2010 elniño/southern oscillation (enso) influences on monthly no3 concentration, stream flow and 0,00 5,00 10,00 15,00 20,00 25,00 30,00 35,00 40,00 0 5 10 15 20 25 30 35 40 45 50 m c m return periode strong el-nino moderat el-nino weak el-nino civil and environmental science journal vol. ii, no. 02, pp. 076-083, 2019 83 precipitation in the little river watershed, tifton, georgia (ga) journal of hydrology, 381 (2010) 352–363 [6] neil m.w., casey m. b., kye m. b., yasir h. k. 2013 reservoir performance and dynamic management under plausible assumptions of future climate over seasons to decades, climatic change (2013) 118:307–320 [7] shu-yi l., chi-chung c., shih-hsun h. 2010 estimating the value of el niño southern oscillation information in a regional water market with implications for water management, journal of hydrology [8] shiau j.t. 2003 water release policy effects on the shortage characteristics for the shihmen reservoir system during droughts, water resources management 17: 463–480, 2003 [9] uriel f. h. a., mélanie t., robert l. 2014 impacts and adaptation to climate change using a reservoir management tool to a northern watershed: application to lièvre river watershed, quebec, canada, water resour manage, 28:3667–3680 open access proceedings journal of physics: conference series civil and environmental science journal vol. 5, no. 1, pp. 055-063, 2022 55 cafe market share using satellite image data and google database in malang city abdul wahid hasyim1,*, eddi basuki kurniawan1, wulan dwi purnamasari1 1 urban and regional planning engineering department, universitas brawijaya, malang, 65145, indonesia *awahidhs@ub.ac.id received 13-04-2022; accepted 29-04-2022 abstract. cafes in malang city have a very large quantity. almost every main road corridor in malang city has a small, medium, or large cafe. in a competitive situation, location factors can be critical, making it very important. therefore, a study is needed to analyze the market share of cafes in malang city from its spatial elements. this study aims to determine the spatial factors that affect the market share of cafes based on sample data in the form of upper-middle-class cafes in malang city. the variables used to measure the market share of the café sample spatially are proximity to universities, building density, road hierarchy, rating, and several competitors. this study uses google satellite image data sources and remote sensing methods for processing spatial data and analyzes it using multiple linear regression analysis. based on the analysis results, it is known that all variables are positive. the variables that have the most influence on the market share of the café sample are building density, university proximity, and road hierarchy. keywords: café, market share, google database, remote sensing 1. introduction malang city is a city located in east java, indonesia. the city is located 90 km south of surabaya and is the second-largest city in east java after surabaya, and is one of the largest cities in indonesia by population. in addition, malang city is also considered a city located in a strategic area. the malang city area has much potential in terms of physical condition, location, and function. it will impact the economic growth of malang city itself [1]. the strategic form is natural and artificial tourism facilities, attracting tourists to visit malang city. learning facilities and facilities in malang city have caused malang city to be nicknamed the city of education, which has a service scale up to the national level. so that many students from outside malang city attend education, especially education at public or private universities [2]. the high number of people entering malang city due to several factors causes the total population of malang city to increase rapidly. of course, this event is the main trigger for increasing economic activity in various sub-sectors in malang city [3]. previous researchers have predicted the growth of the city of malang with an artificial neural network (ann) model using molusce, a qgis plugin. the study aims to describe the town's growth in malang city over 24 years and to predict the city's future development civil and environmental science journal vol. 5, no. 1, pp. 055-063, 2022 56 using the ann model for 2027. the results show that the built area will increase by 11.79% from 2015 to 2027. in 2027, the built area will cover the city by 73.21% of the city area [4]. spatially, one of the strongest impacts is the amount of land that has the potential to be used for business activity. one manifestation of this impact is the emergence of businesses in the cafe and restaurant sector. cafes in malang city have a very large quantity. almost every main road corridor in malang city has a small, medium, or large cafe. based on gdp malang city (2021) data, café and restaurant is one of the sectors contributing the highest grdp in malang city. so this sector should get better attention from several stakeholders, especially the government and private parties. the location of each cafe will also determine the amount of opportunity for the sale of beverage products provided. if the cafe's location is close to the center of the youth crowd, it is considered to have the potential to dominate the market share [5]. existing the distribution of cafes in malang tends to be closer to the center of the educational area. such as soekarno hatta street, close to brawijaya university, sigura-gura corridor street, close to itn university, and jalan ijen corridor, close to malang state university. it causes these cafes to have very tight competitiveness. every cafe often has to innovate to produce more attractive and unique visual cafes to win the so-called market share [6]. location factors can be critical in a competitive situation, making it very important [7]. so that business actors will correctly determine the potential location for establishing a café business and not fall in its market share. previous studies also found that the business area is closely related to the success of the business [8]. this study aims to determine the spatial factors that affect the market share of cafes based on sample data in the form of upper-middle-class cafes in malang city. 2. material and methods the research location of this research is in malang city. geographically, malang city is located in the southern part of the eastern part of java island and has an area of 145.28 km². malang city is situated between 440-667 meters above sea level. malang city is located in the middle of malang regency, which is situated at 112.06°-112.07° east longitude and 7.06°-8.02° south latitude. the satellite image data used in this study is google satellite imagery with a zoom specification of level 22 and has natural color. satellite image data is processed radiometrically (colour correction) to provide an overview of the existing surface of malang city and slightly processed geometrically to provide a higher level of accuracy. the main purpose of using google satellite image data is to make precise and accurate variable data needed in this study, such as building density and the distance of the café to the university. the sample used in this study is a middle-class cafe and above. it is indicated by several factors such as rating, number of reviews, and the cafe's physical condition, which can be found on the google maps database. databases on google maps, especially cafes in malang city, will be extracted into shapefiles that can be inputted into gis software. then the data will be selected according to the middle and upper cafe criteria. table 1 is the criteria for middle and upper cafes. table 1. criteria for upper-middle café criteria penilaian 1. review number of middle and upper cafe reviews > 500 reviews 2. rating café has a rating value of >4 3 physical condition cafe the middle and upper cafe has several facilities (such as café parking area, wifi, toilets, waiters, etc.) and modern interior/exterior design) civil and environmental science journal vol. 5, no. 1, pp. 055-063, 2022 57 the variables used in this study are the factors that are thought to be the determinants of market share in the spatial element based on the theoretical studies that have been carried out. table 2 shows the variables used in the study. table 2. research variable variables categories required data 1. x1 : distance of cafe to university 4 : close to 3 universities 3 : close to 2 universities 2 : close to 1 university 1 : far from university • shp data selected café location • buffer 1 km per location point • university area shp 2. x2 : building density 4 : 75%-100% 3 : 50%-75% 2 : 25%-50% 1 : 0%-25% • shp data for the selected café location • buffer 1 km per location point • malang city building shp 3 x3 : road hierarchy 4: arteries 3: collector 2: collector 1: neighborhood road • shp data for the selected café location • shp of malang city road agency 4 x4 : rating café rating data on google map database 5 x5 : number of rivals 4: no rivals 3: there is 1 rival 2: there are 2 rivals 1: more than 3 rivals • shp data for the selected café location • buffer 1 km per location point 6 y : number of reviews (assumed as number of visitors) café review data on google map database to determine the effect of the independent variable on the dependent variable, an analytical method is used that can describe the equation model. the analytical method used is multiple linear regression analysis. the classical assumptions were first tested on the compiled data at the multiple linear regression analysis stages. suppose the data has passed the classical assumption test. in that case, the data is feasible to be processed to produce an equation model. the resulting equation model will also undergo a model feasibility test process so that the model is possible to use. 3. result and discussion several data acquisition scenarios have been designed according to research needs. data compiled using several methods, gis and remote sensing, will be rearranged to form a data variable. these variables will later be reprocessed using multiple linear regression analysis to find a model of the influence of variables on the market share of cafes in malang city. 3.1. distribution of malang city café data on the distribution of cafes in malang city is obtained by extracting the google map database into a file with shp format that can be inputted into gis software. the extracted cafe location data is civil and environmental science journal vol. 5, no. 1, pp. 055-063, 2022 58 the distribution of cafes in malang city without any prior selection. so, hundreds of cafe locations in malang city are included in the list (figure 1). figure 1. sample café location map based on the selection of cafe location points, 36 upper-middle-class cafes were found that matched the specified criteria. most of these cafes are spread out in lowokwaru district, with 16 cafes. in klojen district there are 13 cafés; in blimbing district there are two cafes; in sukun district and kedungkandang district there is one café each. 3.2. distance from café to university the proximity of the café to the university is assessed based on the proximity of the university area to the café within a one km radius (figure 2). the use of a one km radius is based on the provisions of the walking distance that indonesian residents, especially young people, can accept. figure 2. sample map of university proximity to starbucks café in malang townsquare civil and environmental science journal vol. 5, no. 1, pp. 055-063, 2022 59 based on the results of identification using gis software, it is obtained that the scoring results of the categorization of the proximity of the university to each cafe sample are obtained. most of the sample cafes in malang (15 cafes) are included in the category close to 1 university or a score of 2. meanwhile, there is only one university, namely ub coffee, for those in the category close to 3 universities or more. 3.3. building density building density is measured based on the number of buildings contained in a one km buffer from each café point (figure 3). figure 3. sample map of building density around café amsterdam coffee figure 4. street hierarchy map at simpang luwe café & resto as a sample based on the results of the calculation of building density in a one km buffer in each sample of cafes in malang city, it was found that most of them were at a building density of 75%-100% or with a score of 4. or a score of 1 only 1 cafe, namely classic chocolate. 3.4. path hierarchy road hierarchy is also assessed as a factor that can determine market share from a spatial point of view. it is related to the ease of accessibility of visitors to the cafe location. the higher the road class, the easier it is for cafe visitors to visit the cafe location. the determination of the road hierarchy score is based on the road class in front of the cafe. the identification of the road hierarchy in each sample of cafes in malang (figure 4) found that most of them had collector class road access or a score of 3. the number of cafes with collector class road access was 13 cafes, while only five cafes with arterial road class accessibility. 3.5. rating the rating of the sample cafe in malang city was mostly has a rating between 4.3 to 5. the number of cafes with this rating is 25 café. the highest rating are amsterdam coffee, beryl coffee, starbuck blimbing, dialoogi space & coffee, starbuck ijen street, and starbucks malang town square, each of which has a rating of 4.7. meanwhile, the lowest malang cafe sample rating with a rating value of 4.3 civil and environmental science journal vol. 5, no. 1, pp. 055-063, 2022 60 is cafe litchi, social palace café, dnr café, upnormal coffee roatser, kepo gelato & café, and simpang luwe cafe & resto. 3.6. number od rivals the number of café rivals is based on the location of the selected sample rival café in a one km buffer as a measure of café proximity (figure 5). the existence of other cafes in the same class at locations below one km from the main cafe location will also affect the market share of the café [9]. so the variable number of competitors is essential for this study. figure 5. rival café location map within one km radius identifying the competitor's number in each cafe sample found that most of the cafe samples were in category 1. it had many competitors or was said to be close to each other in a one km buffer. it raises the assumption that most café samples compete with each other by location. 3.7. regression multiple linear regression analysis aims to calculate the value of the influence of each independent variable on the dependent variable. however, it is necessary to test the classical assumptions on the compilation of research variable data before that. the following are the results of the classical assumption test carried out on the compilation of data in this study. a. autocorrelation table 3. research variable model r std. error of the estimate durbin watson 1 0.890a 0.28577263 2.055 based on the table 3 model summary, it can be seen that the durbin watson value is 2.055. this figure is compared with the durbin watson table with the limit values of dl and du on the number of samples n = 33 and the number of variables or n = 5. the result is avoiding the problem of autocorrelation. civil and environmental science journal vol. 5, no. 1, pp. 055-063, 2022 61 b. multicollinearity test table 4. coefficients model sig. collinearity statistics tolerance vif 1 (constant) 0.000 x1 0.002 0.376 6.002 x2 0.000 0.307 2.205 x3 0.045 0.147 6.878 x4 0.000 0.139 8.062 x5 0.001 0.454 8.213 table 4 shows that the value of vif (variance inflation factors) on all predictor variables is less than 10. the independent variables used avoid multicollinearity problems. c. normality test a normality test determines whether the data used has been normally distributed. normally, the significance value is less than 5% or 0.05. table 5. kolmogorov smirnov unstandardized residual n 33 normal parameters a,,b mean 0.0809 std. deviation 0.30216 kolmogorov-smirnov z 1.349 asymp. sig. (2-tailed) 0.054 based on the kolmogorov smirnov test on research data using spss [10], it can be seen that the research data is normal distributed. it is indicated by the sig value exceeding 0.05 or 5%, namely 0.054. a sig value of more than 0.05 means that it is not significant or means that the data is relatively the same as the average, so it is normal. d. heteroscedasticity test table 6. glesjer model standardized coefficients t sig. beta 1 (constant) 3.012 0.003 x1 -0.053 -0.584 0.560 x2 0.036 0.294 0.769 x3 -0.010 -0.055 0.956 x4 -0.127 -0.696 0.487 x5 0.125 1.247 0.214 based on table 6, it can be concluded that the research data does not experience heteroscedasticity problems. it is because the sig value of each independent variable exceeds 0.05, which means it is not significant. so that all variables do not experience symptoms of heteroscedasticity. civil and environmental science journal vol. 5, no. 1, pp. 055-063, 2022 62 e. model the data used does not experience problems in the classical assumption test. the data is ready to be carried out with multiple linear regression analysis. the model results from the multiple linear regression analysis processes are as follows. y = 160 + (0,276) x1 + (0,476) x2 + (0,281) x3 + (0,003) x4 + (0,100) x5 information : y = number of visitors x1 = distance of cafe to university x2 = building density x3 = path hierarchy x4 = rating x5 = number of rivals to determine whether the model is feasible to predict the number of cafe visitors as a win in market share, the model has carried out a feasibility test with three stages: model reliability test, regression coefficient test, and coefficient of determination test. the following are the results of the model's feasibility test a. model reliability test table 7. anova model sum of squares df mean square f sig. 1 regression 50.483 7 7.212 82.837 0.000 a residual 17.848 205 0.087 total 68.331 212 based on table 7, it can be seen that the sig value is 0.000, which means it is smaller than the significance level value of 5% or 0.05. so it can be concluded that the regression model is feasible to explain how much influence all independent variables have on the number of visitors. b. regression coefficient test based on table 4, it can be seen that in the sig column, all independent variables have a probability value of less than a significance value of 5% or 0.05. it means that all independent variables have a significant influence with a 95% confidence level on the dependent variable, namely the number of visitors. hence, all variables free deserves to be made accessible. c. coefficient of determination test table 8. model summary model r r square adjusted r square 1 0.860 a 0.739 0.730 based on table 8, it can be concluded that the proportion of the influence of all independent variables is 0.739 or 73.9% on the dependent variable, namely the number of visitors. it shows in the model summary table in the r square column. civil and environmental science journal vol. 5, no. 1, pp. 055-063, 2022 63 4. conclusions the most influential variable in the number of visitors is the density of buildings, with a coefficient value of 0.476. building density is indicated as the intensity of population activity. the denser a location is, the higher the intensity of its activities. it will also have the potential to bring in café visitors. while the variable that has the least effectiveness is the café rating, with a coefficient value of 0.003. the café rating as a value for the quality of products and services is only known when potential visitors look at the google map and not as a factor related to location. the second most influential variable is the road hierarchy, with a coefficient value of 0.281. the road hierarchy indicates the ease of accessibility to the cafe location. the higher the class or street hierarchy, the higher the potential for the café to be visited. so for a cafe to win market share in an area, the spatial aspects that need to be prioritized are the density of buildings and the road hierarchy. because these two variables have the highest positive influence value in this study. it should be emphasized that the variables used in this study are spatial aspects. at the same time, the winning of market share is not determined from the spatial aspect but by many factors such as marketing strategy, product and service quality, and others. references [1] a. w. hasyim, a. b. pandiangan, and w. sasongko, “perbedaan harga pasar lahan dan ketetapan harga lahan oleh pemerintah (njop) di kecamatan sidoarjo,” urband reg. planning. brawijaya univ., 2020. [2] pramadani, “pengaruh materialisme, prestise dan kelompok referensi terhadap keputusan pembelian konsumen pada kafe mewah di kota malang,” j. ekon. dan bisnis univ. brawijaya, 2014. [3] a. w. hasyim and h. i. . gusti, “faktor-faktor yang mempengaruhi pertumbuhan lahan di kabupaten manggarai timur,” urband reg. planning. brawijaya univ., 2019. [4] a. nugroho, a. hasyim, and f. usman, "urban growth modelling of malang city using artificial neural network based on multi-temporal remote sensing," civ. environ. sci., vol. 001, no. 02, pp. 052–061, 2018, doi: 10.21776/ub.civense.2018.00102.2. [5] r. f. lusch and m. d. patrick, retail management. ohio : south western publishing co., 1990. [6] j. griffin, customer loyalty : menumbuhkan dan mempertahankan kesetiaan pelanggan. jakarta: erlangga, 2005. [7] h. hani, dasar-dasar manajemen produksi dan operasi. yogyakarta : bpfe, 2000. [8] n. indarti, "business location and success: the case of internet café business in indonesia," gadjah mada int. j. bus., vol. 6, no. 2, p. 171, 2004, doi: 10.22146/gamaijb.5543. [9] m. suyanto, marketing strategy top brand indonesia. yogjakarta: andi offset., 2007. [10] i. ghozali, aplikasi analisis multivariate dengan program sps. semarang: universitas diponegoro, 2005. open access proceedings journal of physics: conference series civil and environmental science journal vol. 5, no. 1, pp. 078-088, 2022 78 the characteristics of combustion of non-catalyst rubber seed oil (hevea brasilliensis) combustion with variations of methanol mixture rachmat subagyo1,*, nina ambarwati1, muchsin2 1 mechanical engineering department, universitas lambung mangkurat, banjarbaru, 70714, indonesia. 2 mechanical engineering department, universitas tadulako, palu, 94148, indonesia. *rachmatsubagyo@ulm.ac.id received 13-04-2022; accepted 29-04-2022 abstract. this study aims to analyze the characteristics of the combustion of a mixture of rubber seed oil with methanol using droplets. the observed characteristics are flame temperature, ignition delay time, combustion rate, and visualization (high heat and flame colour). the variation of the mixture used in this study was a mixture of rubber seed oil and methanol with mixed percentages of 0%, 10%, 20%, 30%, 40%, and 50%. the droplet tool used for research is a tool designed by the researcher. the results showed that the highest flame temperature value was found in the 0% mixture, 114oc, and the lowest was in the 50% mixture, namely 79.67ºc. the highest ignition delay time value is in the 0% mixture, which is 3.33 s, and the lowest is at 50%, which is 2.21 s. the highest combustion rate value at 50% mixture is 0.517 mm2/s and the lowest at 0% is 0.317 mm2/s. the highest flame height in the 0% mixture was 42.6 mm, and the lowest at 50% was 23 mm. keywords: droplets, rubber seed oil, ignition delay time, characteristics of combustion. 1. introduction the supply of petroleum in the world is getting depleted in indonesia due to the increasing human need for petroleum energy. this condition is also triggered by the increasing demand for oil energy in the transportation sector or the industrial sector in indonesia. therefore, there is a need for new renewable energy sources as a substitute for petroleum fuel [1]. alcoholic fuels such as ethanol, methanol, butanol, and propanol can also be used as alternative vehicle fuels. one is processing rubber seeds into diesel engine fuel through an extraction process. due to several factors, the oil obtained from the rubber seed extraction process is further processed to obtain suitable diesel fuel [2]. based on the explanation above, research on rubber seed oil with a mixture of methanol will be conducted to determine its combustion characteristics and its use on a larger scale. the combustion characteristics to be carried out include ignition delay time, flame visualization, flame temperature, and burning rate. rubber seeds, if used, will be quite profitable because they are very abundant. south kalimantan is one of the rubber-producing provinces (hevea brasilliensis), with an area of ± 239,442 ha in 2012. mailto:rachmatsubagyo@ulm.ac.id civil and environmental science journal vol. 5, no. 1, pp. 078-088, 2022 79 rubber seeds contain 40-50% oil, where the composition of palmitic acid is 13.11%, stearic acid is 12.66%, arachidic acid is 0.54 %, oleic acid 39.45%, linoleic acid 33.12%, and the rest is lemark lane acid. oleic, linoleic, and linolenic acids are very beneficial for health, as a source of omega 3, 6, and 9 fatty acids. in contrast, palmitic and stearic acids have the potential to be used as fuel of good quality [3]. methanol has the chemical formula (ch3oh) and is the simplest form of alcohol. in atmospheric conditions, it is a light, volatile, colorless, flammable, and toxic liquid with a characteristic odor (smells lighter than ethanol). methanol has one carbon bond, so it is easier to obtain glycerol separation. combustion is a rapid oxidation process in fuel with the production of heat and light. the release of light and heat from a fire. complete combustion occurs when there is sufficient oxygen supply, and usually, combustion requires air to take place completely [4]. droplet combustion is also called non-premixed combustion. it occurs because the fuel contained in the droplets mixes with the air. the droplets will evaporate to spread the fuel vapor with the air and produce a flame when heated. flame temperature is the maximum temperature of the fuel flame that occurs when there is no heat leakage around it. the adiabatic flame temperature is needed to determine how much heat occurs when other fuels with lower calorific values will cause a decrease in flame temperature and vice versa. the flame temperature value is directly proportional to the heat possessed by the fuel [4]. ignition delay time is the time it takes for fuel to ignite when it receives heat. the value of the combustion delay is very important for fuel because the higher the combustion lag time, the longer it will take for fuel to ignite; this will cause a reaction delay. combustion causes symptoms of decreased performance of an engine [4]. the average combustion rate is the speed at which the fuel burns when it starts burning until it runs out. the formula for the average combustion rate is the quotient of the average droplet diameter and the time of flame evolution. it is measured from the temperature signal in seconds and has the equation mm2/second [5]. 2. material and methods the research was carried out from april 15 to may 31, 2021. the manufacture of biodiesel from rubber seeds and the testing process were conducted at the laboratory mechanical engineering, faculty of engineering, university of lambung mangkurat banjarbaru. tools and materials used: injection with a volume of 1.0 ml, the heating element with a coil diameter of 1.30 mm, datalogger, thermocouple type-k, t-transformer model: oska-60-12, combustion chamber and ruler, camera specification camera 50mp, f/1.8 with autofocus, tripot, sample bottle, water heater, measuring cup and digital balance type dj6001a. ingredients used: 90 ml rubber seed oil and 30 ml methanol (figure 1). civil and environmental science journal vol. 5, no. 1, pp. 078-088, 2022 80 figure 1. research installation 2.1. manufacturing of raw material collecting rubber seeds found in community plantations in sidomulyo village, wanaraya subdistrict, barito kuala regency. then do the separation of the rubber seed shell and take the contents. after that, the rubber seeds are mashed with a blender machine; the crushed rubber seeds are then dried. the dried rubber seeds are collected for further extraction to obtain pure rubber seed oil. the method used is reflux extraction; this extraction is carried out at the fmipa lambung mangkurat university lab with a mixture of 300 ml of solvent and 150 grams of crushed rubber seeds; when reflux extraction is complete, distillate for 1 hour to separate the solvent content from the oil (figure 2). 2.2. test sample preparation preparation of rubber seed oil obtained by using the reflux extraction method [6,7]. methanol can be found in chemical shops in the area near the study. 2.3. test sample making preparing rubber seed oil and methanol, prepare variations of the methanol mixture with a ratio of 0%, 10%, 20%, 30%, 40%, and 50% of 5 ml of rubber seed oil for each sample. prepare 50 ml of pure rubber seed oil and heat to a temperature between 50 degrees celsius; measure with a thermocouple. mixing rubber seed oil that has been heated with methanol in each variation. rubber seed oil that has been heated and mixed with methanol is deposited for 24 hours. 2.4. testing procedure place the camera (figure 1.5) at a predetermined distance of 50 cm. dropping rubber seed oil with the same drops, all samples that have been completed are varied using a droplet dropper at the point provided. turn on the heating element within 5 seconds then the heating element is shifted to near a predetermined point. observing the visualization of the flame, which includes the height and color of the fire, using the camera that has been provided with a predetermined distance of 50 cm. observe the 1 2 3 4 5 6 8 9 10 annotation : 1. transformer 2. heating element 3. ruler 4. combustion chamber 5. camera 6. tripot 7. oil dropper 8. type-k thermo thermocouple 9. data logger 10. laptops 7 civil and environmental science journal vol. 5, no. 1, pp. 078-088, 2022 81 temperature on the data logger generated from each sample. observe the ignition delay time of each sample. observe the burning rate of each sample. observe and record the results of each test. figure 2. flowchart civil and environmental science journal vol. 5, no. 1, pp. 078-088, 2022 82 3. result and discussion the effect of the percentage of the mixture of rubber seed oil with methanol on the flashpoint can be seen in figure 3. figure 3. the effect of the amount of rubber seed oil mixed with methanol on the flashpoint figure 3 describes the effect of the percentage of rubber seed oil with methanol on the flashpoint temperature. the lowest flash point value is shown at the percentage of 50% methanol mixture with a temperature value of 79.67ºc, while the highest flash point value is shown at the percentage of 0% methanol mixture with a temperature value of 114ºc. the graph above shows that the higher the percentage of rubber seed oil and methanol mixture, the temperature will decrease. the flashpoint value of methanol is smaller than that of rubber seed oil, where methanol itself has a flashpoint value of 11oc. the addition of methanol can also cause the calorific value of the fuel mixture to decrease. flashpoint is influenced by the rate of evaporation (volatility) influenced by the nature of the fuel. the effect of the amount of rubber seed oil mixed with methanol on the ignition delay time can be seen in figure 4. figure 4. the influence of the percentage of the mixture of rubber seed oil with methanol on ignition delay time 114 101 99 91,3 85,3 79,67 0 20 40 60 80 100 120 0% 10% 20% 30% 40% 50% t e m p e ra tu re (o c ) percentage of methanol mixture (%) 3,33 2,62 2,45 2,42 2,4 2,21 0 0,5 1 1,5 2 2,5 3 3,5 0% 10% 20% 30% 40% 50% t im e (s ) percentage of methanol mixture (%) civil and environmental science journal vol. 5, no. 1, pp. 078-088, 2022 83 figure 4 describes the percentage of the mixture of rubber seed oil with methanol at the ignition delay time. the graph above shows that the lowest ignition delay time is shown at 50% mixture percentage with a duration of 2.21 s, while the highest ignition delay time is shown at 0% mixture percentage with a duration of 3.33 s. the graph above shows that the higher the percentage of rubber seed oil + methanol mixture, the lower the ignition delay time value. the flashpoint value of methanol is lower than rubber seed oil, where the flashpoint value of methanol itself is 11ºc. the flashpoint is the fuel's flashpoint at the lowest temperature; the lower the flash point value, the faster the ignition time. the evaporation rate affects ignition delay time; the faster the evaporation and burns also lower the ignition delay time value. the effect of the percentage of the mixture of rubber seed oil with methanol on the burning rate can be seen in figure 5. figure 5. the effect of a mixture of methanol and rubber seed oil on the burning rate figure 5 describes the effect of the percentage of mixing rubber seed oil with methanol on the burning rate. the lowest average burning rate value is indicated at the percentage of the mixture of 0% with a duration of 0.317 s. in comparison, the highest burning rate appears at the percentage of 50% mixture with a duration of 0.517 s. figure 5 shows that the higher the percentage of rubber seed oil + mixture of methanol, the higher the buring rate will be. the oxygen content in methanol can accelerate the combustion reaction, with the addition of methanol will increase the oxygen concentration in the fuel. with each addition of volume-based methanol, the oxygen concentration in the fuel will increase. the increase in oxygen in the fuel can lead to better combustion quality and faster combustion reactions so that the value of the combustion rate is higher. 0,317 0,373 0,419 0,44 0,454 0,517 0 0,1 0,2 0,3 0,4 0,5 0,6 0% 10% 20% 30% 40% 50% b u rn in g r a te ( m m 2 /s ) persentage of methanol mixture (%) civil and environmental science journal vol. 5, no. 1, pp. 078-088, 2022 84 figure 6. the effect of a mixture of rubber seed oil and methanol on fire height figure 6 explains the effect of the percentage of mixing rubber seed oil with methanol on high heat. the lowest fire height is shown at the 50% mixture percentage, which is 23 mm, while the highest fire height is shown at the 0% mixture percentage, which is 42.6 mm. figure 6 reveals that the higher the percentage of rubber seed oil + methanol mixture, the lower the flame height. the rate of evaporation and diffusion of fuel affects the flame height. pure rubber seed oil is slower at evaporation and diffusion of fuel but burns faster. if the percentage of the methanol mixture added is higher, the combustion reaction rate will increase [8-10]. the reaction rate affects the flame time and flame height; the higher the combustion reaction rate, the relatively shorter flame time produced, and the lower the resulting flame height. the image below shows the visualization of the fire of a mixture of rubber seed oil and methanol with mixed percentages of 0%, 10%, 20%, 30%, 40%, and 50%. figure 7. visualization of fire percentage mix 0% figure 7. shows that the mixture of rubber seed oil + and methanol with a percentage of 0% takes 3.50 s to reach the maximum height with a fire height of 42.6 mm. the dominant flame colour is yellow. extinguished at 4.10 s. 42,6 40,3 30 28,6 25 23 0 5 10 15 20 25 30 35 40 45 0% 10% 20% 30% 40% 50% t h e f ir e h e ig h t (m m ) persentage of methanol mixture (%) civil and environmental science journal vol. 5, no. 1, pp. 078-088, 2022 85 figure 8. visualization of fire mixed percentage 10% figure 8 shows that a mixture of rubber seed oil + methanol with a 10% percentage takes 2.75 s to reach the maximum height with a fire height of 40.3 mm, and the dominant color of the fire is yellow; after reaching the maximum height, the fire gradually decreases until it is extinguished at 3.48 s. figure 9. visualization of flame percentage of methanol mixture 20% figure 9 shows that a mixture of rubber seed oil + methanol with a percentage of 20% takes 2.60 s to reach the maximum height with a flame height of 30 mm, and the dominant colour of the fire is yellow after reaching the maximum height, the fire gradually decreases until it is extinguished over time 3.10s. civil and environmental science journal vol. 5, no. 1, pp. 078-088, 2022 86 figure 10. visualization of flame percentage of 30% methanol mixture figure 10 shows that a mixture of rubber seed oil + methanol with a percentage of 30% takes 2.52 s to reach the maximum height with a fire height of 28.6 mm, and the dominant colour of the fire is yellow; after reaching the maximum height, the fire gradually decreases until it is extinguished at 2.95 s. figure 11 visualization of flame percentage of 40% methanol mixture figure 11 shows that a mixture of rubber seed oil + methanol with a percentage of 40% takes 2.43 s to reach the maximum height with a fire height of 25 mm, and the dominant colour of the fire is yellow after reaching the maximum height, the fire gradually decreases until it is extinguished over time 2.86s. civil and environmental science journal vol. 5, no. 1, pp. 078-088, 2022 87 figure 12 visualization of flame percentage of methanol mixture 50% figure 12 shows that a mixture of rubber seed oil + methanol with a percentage of 50% takes 2.37 s to reach the maximum height with a flame height of 23 mm, and the dominant colour of the fire is yellow after reaching the maximum height, the fire gradually decreases until it goes out in time 2.51 s. figure 13. comparison of maximum fire height in each mixture with percentages of 0%, 10%, 20%, 30%, 40%, and 50% from figure 13, it can be seen that the mixture of rubber seed oil + methanol has a different flame duration and time to reach the maximum height. the value of the longest flame time is indicated by a mixture of 0% methanol with a value of 4.10 s, and the fastest is indicated by a mixture of 50%, which is 2.51 s. for fuel with a percentage of 50% to reach the maximum fire height, it takes a faster time than fuel with other percentages; this is due to the burning rate with a percentage of 0% lower than the civil and environmental science journal vol. 5, no. 1, pp. 078-088, 2022 88 percentage of other mixtures. in the condition of the fire colour of the fuel with a percentage of 0% to 50%, the colour of the fire resulting from burning is predominantly yellow. 4. conclusions the more methanol mixture in rubber seed oil, the more flashpoint value decreased; this was due to the flammable nature of methanol because it had a low flash point value where the flashpoint value of methanol itself was 11ºc. with the increasing percentage of the methanol mixture, the ignition delay time value decreased because the flashpoint value of methanol was smaller than rubber seed oil; the lower the flash point value, the faster the combustion. the higher the percentage of the mixture of methanol to rubber seed oil, the higher the resulting burning rate; this is because the oxygen content in methanol can accelerate the combustion reaction; the addition of methanol will increase the oxygen concentration in the fuel. the results of the high flame test increase the percentage of the rubber seed oil + methanol mixture; the lower the flame is because the methanol mixture increases the rate of the combustion reaction, the reaction rate affects the flame time and flame height. references [1] sasongko, m. n. (2018). pengaruh prosentase minyak goreng bekas terhadap karakteristik pembakaran droplet biodiesel. flywheel : jurnal teknik mesin untirta, iv(volume iv nomor 2, oktober 2018), 8–13. http://jurnal.untirta.ac.id/index.php/jwl/article/view/3656. [2] mulyadi, e. (2011). proses produksi biodiesel berbasis biji karet. jurnal rekayasa proses, 5(2), 40–44. https://doi.org/10.22146/jrekpros.1898. [3] hakim, a., & mukhtadi, e. (2018). pembuatan minyak biji karet dari biji karet dengan menggunakan metode screw pressing: analisis produk penghitungan rendemen, penentuan kadar air minyak, analisa densitas, analisa viskositas, analisa angka asam dan analisa angka penyabunan. metana, 13(1), 13. https://doi.org/10.14710/metana.v13i1.9745. [4] mesin, t., konversi, k., brawijaya, u., & teknik, f. (2018). uji karakteristik pembakaran droplet biodiesel dari hasil transesterifikasi minyak goreng bekas skripsi. [5] wardana, i. n. g. (2010). karakteristik pembakaran droplet minyak jarak pada berbagai suhu minyak. 89, 659–664. [6] t. a. seadi et al., biogas handbook. 2008. [7] s. achinas, v. achinas, and g. j. w. euverink, "a technological overview of biogas production from biowaste," engineering, 2017. [8] y. yin et al., "effect of char structure evolution during pyrolysis on combustion characteristics and kinetics of waste biomass," j. energy resour. technol. trans. asme, vol. 140, no. 7, 2018. [9] p. mullinger and b. jenkins, industrial and process furnaces: principles, design and operation: second edition. 2013. [10] d. h. qi, l. m. geng, h. chen, y. z. bian, j. liu, and x. c. ren, "combustion and performance evaluation of a diesel engine fueled with biodiesel produced from soybean crude oil," renew. energy, 2009. http://jurnal.untirta.ac.id/index.php/jwl/article/view/3656 https://doi.org/10.22146/jrekpros.1898 https://doi.org/10.14710/metana.v13i1.9745 civil and environmental science journal vol. 02, no. 01, pp. 035-043, 2019 35 determining infiltration rate from infiltration measurement with flooding method by turftech infiltrometer d noorvy khaerudin1, andre primantyo2, ryan rahardika2 1civil engineering department, tribhuwana tunggadewi university, malang, indonesia 2water resources engineering department, universitas brawijaya, 65145 malang, indonesia dianoorvykhaerudin@gmail.com received 15-12-2018; revised 21-01-2019; accepted 10-03-2019 abstract. the density of the soil in this study estimate parameters with a dry bulk density. variation of soil density based on urban land us and then grouped into heavy, medium, and high-density soil. the rate of infiltration testing is performed by using turftech infiltrometer. and then analyzed with an infiltation horton modification models. the specification of turftech double ring infiltrometer are 6.03 cm for inner ring diameter and 10.79 cm for outer ring diameter. the result of infiltration rate observations is infiltration rate for higher density soil and land slope had low influences. the results showed that the turftech ifiltrometer that is used produced well results with 87% accuracy compared with the horton equation infiltration rate model. for the measurement results feasibility, then the turftech infiltrometer unable to represent for the land slope and density, because from the regression test the relationship between land slope and density toward infiltration rate was not significant and obtained average of 38% from the obtained r2. keywords: density soil, land slope, landuse, turftec infiltromete, urban landflow 1. introduction the water that falls on the soil surface will flow as the flow of runoff and some will go into the ground. this condition is strongly influenced by various things, including the following: the intensity of rainfall, the porosity of the soil, the soil mass density, soil water content, soil texture, soil structure, density soil, the slope of the land, the content of soil organic matter, and the vegetation surface [5]. hydrological cycle is the movement of water into the air, then falls to the earth's surface again as rain. the rain that falls to the ground most any are directly flows to the sea and some seeped into the ground. the water that seeped into the ground is called infiltration. infiltration is the part that is missing on the flow of runoff that occurs [2]. the concept of urban drainage especially at surface runoff, in water balance concept, tell that infiltration is a factor of rainwater loss in the urban drainage process [1], so the need for the study of the consequences of losing because the process of infiltration. mailto:dianoorvykhaerudin@gmail.com civil and environmental science journal vol. 02, no. 01, pp. 035-043, 2019 36 this assessment can be done in various ways. how the measurement that is include with flooding and sprinkling [4]. the flooding methode is to inundate the lands in a tube to get high water is constant. while sprinkling ways is to use a piece of land which is conditioned [10], then artificial rain was made to consider the value of the magnitude of the loss and runoff infiltration happens. 2. material and methods 2.1 material the method of detension is used more to know the rate of infiltration directly in the field [12]. weakness in these tools is the depth of observation is limited to 20 centimeters in size, so the water detention on operational measurement is limited. yet with limitations and weaknesses that this research was conducted to find out how the accuracy in terms of size and the diameter and depth of the tool in the measurement of the rate of infiltration is produced. infiltration rate observations in the field will be calibrated with the model equations of horton with the equation as follows: f = fc + (fo – fc) e-kt; i ≥ fc dan k = constan description: f = rate of infiltration at time t (mm/min) fc = the rate of infiltration when constant (mm/min) fo = the rate of infiltration of the beginning (mm/min) k = constant geophysical t = time e = 2.718 the equation is used because of horton's equation in general can illustrate the process of infiltration rate that occurs mainly in the field of masculinity [6]. infiltration capacity is the ability of soil to absorb water in the surface or surface water flow in the inner corner, which by itself with a permeation surface water flow that would be very influential. obviously the larger the infiltration capacity then the flow of water at ground level was further reduced. in contrast, the small capacity of infiltration caused the abundance of soil pores are clogged, then the flow of surface water increases or increases [3]. sarief [11] suggests that the higher the density of the soil, then the infiltration will be getting smaller. the density of this land can be caused by the influence of rainfall pressure on the soil surface. the ground is covered by plants usually have a greater rate of infiltration than land surface that is open [8]. this is caused by rooting plants that cause higher soil porosity, so more water and increase on a surface covered by vegetation, it can absorb the energy of the rain and mashed so it was able to maintain a high infiltration rate [9]. 2.2 methods this research was carried out at 4 locations that have the texture of silt loam soil. the data retrieved is the primary data that are the direct observation in the field. the analysis is done with statistics linking the analysis of influence of soil density against the infiltration rate of the measurement results, the slope of the land against the infiltration rate and the rate of infiltration between measurements in the field with the measurement results with the horton equation turftech infiltrometer [7,13]. measurement by using the tool turftec infiltrometer is easy to do, because the tool easy to carry everywhere and strongly support in determining the rate of infiltration in the field. this tool uses the concept of a double ring (double ring infiltrometer). its size varies. for this research tool used has an inside diameter 6.03 cm and 10.79 cm to outer diameter. the tools used can be seen more clearly in figure 1. civil and environmental science journal vol. 02, no. 01, pp. 035-043, 2019 37 the use of this tool helps planners determine the mobilization of design of urban drainage. at issue is whether the size of the tool, using the concept of the double ring affects the results of the measurement of the rate of infiltration. therefore, in this research aims to know the accuracy of the tool turftec infiltrometer with 3 parameters are taken, i.e. density, slope, and her grain size. external condition that occurs will be found in research done in the field. observations of other parameters is done, namely by taking soil samples and tested for numbers pore, moisture content of the start and end, the weight of soil type, soil grain composition between the sand, mud and dust. this is intended so that the analysis can reach its limitations. the influential parameters required are used to find out the rate of infiltration is the density of soils, land slope, soil grain size composition. the density of the ground known by measuring the weight of the contents is soil dry soil at the site of research using the tool sandcone, figure 2. the slope of the land is known beda by measuring the height between the point location measurements at a distance of 100 meters using a theodolite, whereas soil grain size composition known by testing in soil science laboratories. figure 1. turftec infiltrometer figure 2. sand cone execution of measurements was done at 5 locations in malang research randomly. each location research repeated with three observation points in the same location. the purpose of this study is to know how the rate of infiltration of the variation of density, grain size and slope the ground (sand, silt, and clay). 3. results and discussion the results of soil testing at the laboratory obtained a variety of constituent composition of soil grains. the large number of granular composition test results obtained from the hydrometer in the laboratory. for details on the calculation of the hydrometer all locations can be seen in attachment. each location has a composition research of soil granules of different compilers. grain size composition of soil can be classified according to the usda (united states department of agriculture) obtained the following results. table 1. composition and soil texture location research soil grain size (φ) soil texture sand (%) silt (%) clay (%) madyopuro 32.4 50.7 16.9 silt loam tlogomas 25.6 52.2 22.2 silt loam sukun 22.8 57.6 19.6 silt loam bunulrejo 37.8 47.6 18.6 silt loam gor ken arok buring 6.0 68.1 25.9 silt loam civil and environmental science journal vol. 02, no. 01, pp. 035-043, 2019 38 the results of the laboratory tests at the ground, land size composition of the research for the largest silt was 68.1% and a low of 47.6%, while for the highest level of clay was 25.9%, lowest 16.9%, so that the average for the level of composition for the sand is 24.92%, silt was 55.24%, and clay was 20.64%. but the location of the samples taken all belongs on the silt loam soil texture. table 2. the results of the analysis of parameters influencing infiltration rate location reasearch water bulk porosity degree of saturation (sr) slope (s) content(w) density (ɣd) (n) (%) (gr/cm3) (%) madyopuro 16.39 1.64 33.9 0.795 0.0063 tlogomas 21.68 1.62 35.2 0.997 0.0020 sukun 33.25 1.13 51.3 0.731 0.0018 bunulrejo 23.30 1.36 45.2 0.701 0.0007 gor ken arok buring 17.70 1.60 38.5 0.734 0.0002 the use of turfthec infiltrometer to measure the rate of infiltration and infiltration capacity is known to its accuracy by doing research through the application of variables that affect the process of infiltration in the soil. land that has the capability of holding water is the fraction of clay. whereas the lands are containing high dust that can hold water available for plants [11]. coarse-textured soils have a high infiltration capacity, while the textured soil soil infiltration capacity have small delicate, so with a fairly low rainfall will cause surface runoff [8]. 3.1 the results of measurement and calculation of infiltration rate the measurement in field retrievied the alue of the rate of infiltration (f), the value of the initial infiltration rate (fo), and the value of constanly infiltration rate (fc). the data will be analyzed using the method of horton. table 3. data measurment and calculation result no t test (minute) high water level (cm) increments t (minute) difference in the down (cm) difference in dow (mm) f guest (mm/minute) start 0 13.5 1 3 12.7 3 0.80 8.00 2.6667 2 6 12.3 3 0.40 4.00 1.3333 3 9 12 3 0.30 3.00 1.0000 4 12 11.7 3 0.30 3.00 1.0000 5 15 11.4 3 0.30 3.00 1.0000 6 18 11.2 3 0.20 2.00 0.6667 7 21 11 3 0.20 2.00 0.6667 8 24 10.8 3 0.20 2.00 0.6667 9 27 10.6 3 0.20 2.00 0.6667 10 30 10.4 3 0.20 2.00 0.6667 11 33 10.2 3 0.20 2.00 0.6667 12 36 10 3 0.20 2.00 0.6667 13 39 9.8 3 0.20 2.00 0.6667 14 42 9.6 3 0.20 2.00 0.6667 15 45 9.4 3 0.20 2.00 0.6667 according to table 3, depicts the results of measurement on site bunulrejo. infiltration rate constant (fc) is 0667 mm/minute. as for fo (the initial infiltration rate) is 2,667 mm/minute. the civil and environmental science journal vol. 02, no. 01, pp. 035-043, 2019 39 process of infiltration from rate start fo up to start constant is in 18 minutes. the calculation to get the equation of horton can be seen in table 4 below. table 4. infiltration rate equation calculations with formulas horton time (minute) f (mm/minute) fc f-fc log (f-fc) 0 3 2.6667 0.6667 2.0000 0.3010 6 1.3333 0.6667 0.6667 -0.1761 9 1.0000 0.6667 0.3333 -0.4771 12 1.0000 0.6667 0.3333 -0.4771 15 1.0000 0.6667 0.3333 -0.4771 18 0.6667 0.6667 0.0000 21 0.6667 0.6667 0.0000 24 0.6667 0.6667 0.0000 27 0.6667 0.6667 0.0000 30 0.6667 0.6667 0.0000 33 0.6667 0.6667 0.0000 36 0.6667 0.6667 0.0000 39 0.6667 0.6667 0.0000 42 0.6667 0.6667 0.0000 45 0.6667 0.6667 0.0000 fc = 0.6667 fo = 2.6667 k = 0.1917 (k = -1/0.434*m) (k = -1/(0.434*-12.09) e = 2.718 f = fc+(fo-fc)e-kt based on the above calculations, so then produced a curve in figure 4, i.e. the rate of infiltration equation curves with the formula horton. the formula for the area of bunulrejo is horton f = 0.67 + (2.667-0.667)e-0.1917t or f = 0.67 + 2 e-0.1917t and then created a table of the results of analysis, calculation of f measurements, f observations, and f horton formula, it could see at table 5. 0 1 2 3 0 10 20 30 40 50 i n f il t r a t io n r a t e ( m m /m in u t e ) time (minute) f horton (mm/minute) f measurment (mm/minute) f = 0,67+2,00e-0,1917t figure 3. parameter k for horton's formula figure 4. infiltration rate of measurement and calculation of horton formula y = -12.029x + 5.857 log (f-fc) ti m e ( m m in ) civil and environmental science journal vol. 02, no. 01, pp. 035-043, 2019 40 table 5. the value of the rate of infiltration of f calculation, f measurement, and f the f horton no t test (minute) f measurment (mm/minute) f calculation (mm/minute) f horton (mm/minute) start 0 1 3 2.6667 1.9890 1.7921 2 6 1.3333 1.4460 1.2999 3 9 1.0000 1.2000 1.0230 4 12 1.0000 1.0512 0.8672 5 15 1.0000 0.9487 0.7795 6 18 0.6667 0.8724 0.7302 7 21 0.6667 0.8126 0.7024 8 24 0.6667 0.7642 0.6868 9 27 0.6667 0.7239 0.6780 10 30 0.6667 0.6897 0.6730 11 33 0.6667 0.6601 0.6702 12 36 0.6667 0.6342 0.6687 13 39 0.6667 0.6113 0.6678 14 42 0.6667 0.5908 0.6673 15 45 0.6667 0.5723 0.6670 based on a comparison of the rate of infiltration measurements with models horton (figure 5) can note that the model could be used in horton prediction value of the rate of infiltration in the field because of the difference in value is not so much with the measurements in the field, i.e. have a swift determination of 87.2%. the mean value of that formula can be used to calculate the horton the rate of infiltration parameters with soil texture. but for the other parameters, such as slope needs to be tested again. analysis to observe infiltration capacity is using several parameters. the parameters are the soil texture, soil treatment, and slope. 0 1 2 3 0 10 20 30 40 50 i n fi lt r a ti o n r a te (m m /m in u te time (minute) f calculation (mm/minute) f horton (mm/minute) figure 5. infiltration rate in measurment, calculation, and horton formula civil and environmental science journal vol. 02, no. 01, pp. 035-043, 2019 41 figure 6. influence of clay against the result f (mm/min) figure 7. the influence of water content against the result f (mm/min) from figure 6 above obtained value r2 = 0.260 means that 26% of the capacity of infiltration is affected by the composition of clay. this shows the curve of the relation between the percentage of clay and infiltration capacity above likely deserves to be used with a value of r2 is significant. it can be seen from the distribution of the data shows that the larger the value of infiltration capacity then the smaller content of clay in the soil. in fact many of the supposed lack of composition in soil clays then will also affect the magnitude of the rate of infiltration. but this is because the land is not necessarily clay composition, but there are still other soil constituents such as sand and silt. with a very small grain size then it will have a very pore space meetings and causing the clays are if exposed to water will easily in saturated conditions, so that at least the content of clay in the soil will not effect much against the magnitude of the rate of infiltration. figure 8. the influence of soil porosity against to infiltration rate (mm/min) figure 9. the influence of sr against to f (mm/min) from figure 8 above obtained value r2 = 0.018 means 1.8%. this curve shows the relationship between porosity and infiltration capacity of above is not feasible for use because it has a very low r2. previously explained that the porosity is a large number of pore space in soil. in fact, should be the more pore space in the soil then the rate of infiltration will be even greater, and vice versa. the pore spaces of note on the land there are three constituent elements, namely the land itself, the water and the air. water and air are the element that occupies a space pore. the larger pore spaces in the soil, it will be more and more of the elements water and air that will occupy a space pore. on testing the rate of infiltration on soil water that seeped into the unknown land would occupy pore space. while in figure 9 the obtained value r2 = 0.447 means 44.7%, showing the curve of the relation between the degree of saturation and infiltration capacity above deserves to be used as it has the r2. civil and environmental science journal vol. 02, no. 01, pp. 035-043, 2019 42 keep in mind to degrees of saturation or sr = 1 is saturated with ground water, while sr = 0 is the ground with dried state. therefore, in accordance with the actual theory explaining that the lower the value of the degree of saturation means ground in very dry conditions, then the rate of infiltrasinya will be even greater and in the greater degree of saturation value means land in a state of saturation of the water, then the rate of infiltrasinya will be getting smaller. from figure 10 obtained a value of r2 = 0.029 means 2.9% the capacity of infiltration is affected by slope parameter. this shows the relationship between the slope of the curves and infiltration capacity of above is not feasible for use because it has a very low r2. this is due to the measurement of the rate of infiltration performed on site with a small slope or can be said to be the location of the flat. besides measuring the rate of infiltration in the field who use the tool turftec infiltrometer has a very small measurement area. so, although performed on the steep slope of the site and will not affect the great small rate of infiltration. the slope of the land may be aware that the more oblique or steep a location, then that will effects is the rate of surface runoff, while the rate of infiltrasinya will not affect much. as for figure 11 gained value r2 = 0.046 means 4.6% density and capacity of infiltration above is not feasible for use because it has a very low r2. based on the test results, low density had a lower rate of infiltration than locations with high density and medium. in fact, should be the smaller the value soil density of a location. figure 10. the influence of slope towards the result f figure 11. the influence of bulk density against f (mm/min) 4. conclusions formula rate equation is horton infiltration well for field testing by parameters of soil conditions and the measurement method with dos flooding. it is based on the rate of infiltration testing of measurement results, the results of the calculation of the formula results, and horton to reach 87.2%. influence of parameters of soil conditions, porosity, soil texture, no significant effect against the rate of infiltration with measurements using turftec infiltrometer. this is due to the size of the infiltrometer turftec sink only 10 cm. the density and the slope are not signifan effect on the rate of infiltration of the results of measurements and calculations of horton, so it can be inferred that the tools can not be used turftech infiltrometer to measure the rate of infiltration with the parameters of the soil conditions, density, and slope. acknowledgement this research is funded by kemenristek dikti as a doctoral scholarship program at brawijaya university. the author appreciates the help from hydrological laboratory in brawijaya university. references [1] bedient. (2008). hydrology and floodplain analysis. canada: prentice hall, pearson education international. civil and environmental science journal vol. 02, no. 01, pp. 035-043, 2019 43 [2] d.m, f. (1997). the influence of slope angle on final infitration rate for interill conditions. geoderma, elsevier, 181-194. [3] ben-zvi, a. (2013). bypassing determination of time of concentration. journal of hydrologic engineering, 1674-1683. [4] beven*, k. (2004). robert e. horton’s perceptual model of infiltration processes. hydrological processes, 3447–3460. [5] e.m, w. (1990). engineering of hydrology. uk: maecillan education uk. [6] gavin, kenneth, and jianfeng xue. 2008. “a simple method to analyze infiltration into unsaturated soil slopes.” 35: 223–30. [7] hjelmfelt, a. (1978). influence of infiltration on overland flow . journal of hydrology, 179185. [8] kenneth c. ames, e. l. (2001). preliminary assessment of infiltration rates and effects on water quality of selected infiltration media for use in highway runoff retention basins in washington state. olympia, washington: washington state department of transportation research office. [9] lipiec. (2006). soil porosity and water infiltration as influenced by tillage. soil and tillage research. [10] li, ming-han, and paramjit chibber. 2008. “overland flow time of concentration.” (2060): 133–40. [11] noorvy, d. (2014). effect of density soil to water recharge (infiltration) in urban overland flow. international confference on suistanable built environment. (pp. (pp. 87-94).). yogyakarta: : universitas islam indonesia. [12] maximilian, john et al. 2011. “coupled simulation of surface runoff and soil water flow using multi-objective parameter estimation.” 403: 141–56. [13] rong-her chen(*), k. j.-m. (2011). experiment on the stability of granular soil slopes by rainfall infiltration. italian journal of engineering geology and environment , 301-311. open access proceedings journal of physics: conference series civil and environmental science journal vol. 02, no. 01, pp. 001-014, 2019 1 analysis of the correlation between land use changes in sub watershed wuno toward lifetime of wuno reservoir, sigi district, central sulawesi province wardani yuliana1, suhartanto ery1, haribowo riyanto1 1 water resources engineering department, universitas brawijaya, malang, 65145, indonesia uly86.yw@gmail.com received 03-01-2019; revised 11-01-2019; accepted 22-01-2019 abstract. wuno reservoir is located in sigi biromaru district, sigi regency, central sulawesi province. it is planned for 50 years. this analysis to known the condition of ideal land use so that the life time of the reservoir reaches 50 years. trend of land use change, erosion and sediment rate estimation using the arcswat model. during 2008-2016, natural forest land use showed a downward trend, while mixed gardens, shrubs, fields and settlements showed an increasing trend. the erosion rate in 2008-2010 increased by 72.5%, in 2010-2012 it increased by 1.45%, in 2012-2014 decreased by 0.09% and in 2014-2016 increased by 0.98%. in 20082016 low behi area was reduced by 3.74%, medium behi was increasing by 14.11%, behi high increased by 16.57% and behi very high increased by 12.64%. this shows that the rate of erosion and the extent of behi are influenced by changes in land use. based on the results of analyzing the lifetime of the reservoir, changes in land use also affect the reduced useful life of the reservoir. vegetative land conservation efforts are adjusting forest areas so that rate of erosion decreases by 62.75%. mechanical land conservation efforts in the form of the construction of 6 check dams so that weight of sediment decreases by 89.24%. keywords: arcswat, land use, erosion rate, bank erosion hazard index, reservoir lifetime. 1. introduction erosion is a moving or transporting land or parts of land from one place to another by natural media [4]. the occurrence of erosion is determined by climatic factors (rainfall intensity), topography, soil characteristics, vegetation cover, and land use [9]. land use changes have resulted in an increase in the value of land erosion, surface runoff, critical watershed condition and an increase in the amount of sediment which has resulted in a reduced lifetime of the reservoir [1, 2, 10, 12, 13, 14]. wuno reservoir is located in oloboju village, sigi biromaru district, sigi regency, central sulawesi province. wuno reservoir utilizes the wuno and konju rivers. located in the wuno subwatershed, palu river basin and included in the palu lariang river basin. its use is to meet the needs of irrigation water for 1,500 ha of rice fields and 500 ha of shallot farming, and to supply raw water needs [6, 7] with 50 years of lifetime. increased erosion occurred in the wuno sub-watershed in 1992 to 2006 [5]. during the period of 1 (one) year the sediment potential in the wuno river increased by civil and environmental science journal vol. 02, no. 01, pp. 001-014, 2019 2 6,270 m3 [6, 7]. the wuno river is suitable for raw water because there are not many residential arears. residential areas sometimes have toxicity levels that are high enough to affect the aquatic habitat and these toxicity levels should be managed [8]. increased erosion and sediment will have an impact on the reduced useful life of the reservoir [3]. based on the results of analyzing, the rate of erosion and the extent of behi are influenced by changes in land use. land use changes also affect the reduced useful life of the reservoir. vegetative land conservation efforts are adjusting forest areas so that rate of erosion decreases by 62.75%. mechanical land conservation efforts in the form of the construction of 6 check dams so that weight of sediment decreases by 89.24%. 2. material and methods 2.1. material the data used in this study include daily 2002-2015 rainfall data, palolo rain station and sibalaya rain station, digital elevation model (dem) map, land use map in 2008, 2010, 2012, 2014 and 2016, map of soil types, map of central sulawesi province forest areas and soil samples for each land use and soil type 2.2. methods 2.2.1. hydrological analysis consistency test the data consistency test is conducted to find out whether there are data irregularities in the available rain data, so that it can be known whether the data is suitable for use in further hydrological analysis or not. in this study 2 (two) methods were carried out, namely (1) double mass curve; (2) rescaled adjusted partial sums (raps). rainfall station location affects the consistency of data, this is indicated by the designed rainfall difference for each definite recurrence time is relatively small [11]. homogeneity test a series of hydrological data presented chronologically as a function of the same time is called a periodic series. generally published field data are debit data, rainfall data, etc., are basic data as hydrological analysis material. the data is arranged in the form of a periodic series, so that before being used for further analysis must be tested. testing the data it means is: (1) test of absence of trend; (2) stationary test; (3) persistence test. the three stages of testing are often referred to as data filtering (data screening). abnormalities test (outliers) outliers is data that deviates too far from other data in a data set. the existence of these data outliers will make the analysis of a series of data biased, or not reflect the actual. outliers test done to find out whether the maximum data and minimum data from the available data sets are suitable for use or not. 2.2.2. soil water assessment tool analysis (swat) measurement and estimation of erosion is difficult to do precisely because the process of events and the factors that influence them is very complex. but with some assumptions and simplifications, erosion measurement and estimation can be done with an acceptable level of approach. there are various ways of observing or measuring erosion that occur, among others, by direct observation in the field, interpretation of topographic maps and aerial photographs and direct measurements with experiments. in this study the erosion rate is calculated by the swat model. the swat model calculates erosion based on the usle modification formula [4]: civil and environmental science journal vol. 02, no. 01, pp. 001-014, 2019 3 sed = 11.8 (qsurf x q peak x a hru )0.56 k x c x p x ls x cfrg (1) with: sed = sediment yield (ton) qsurf = surface runoff volume (mm/ha) q. peak = peak discharge (m3/sec) a hru = watershed area (ha) k = soil erodibility c = plant factors p = land management factors ls = slope factor cfrg = soil material roughness factor 2.2.3. bank erosion hazard index analysis the score of the erosion hazard value is stated in the bank erosion hazard index (behi), which is defined as follows [4]: 𝐵𝐸𝐻𝐼 = 𝑃𝑜𝑡𝑒𝑛𝑠𝑖𝑎𝑙 𝐸𝑟𝑜𝑠𝑖𝑜𝑛 (𝑡𝑜𝑛.ℎ𝑎−1.𝑦𝑒𝑎𝑟−1) 𝑇 (𝑡𝑜𝑛.ℎ𝑎−1.𝑦𝑒𝑎𝑟−1) (2) with t is the magnitude of erosion that can still be left behind. the bank erosion hazard index can be determined as set out in the t value assessment guide for land in indonesia (table 1). table 1. bank erosion hazard index classification bank erosion hazard index value classification < 1.0 1.01 – 4.0 4.01 – 10.0 > 10.01 low medium high very high 2.2.4. reservoir lifetime analysis the lifetime of the reservoir is the time when the reservoir can be used to hold water and distribute it. reservoir utilization age in terms of full dead storage by sediments. deposition time from various elevations is cumulative to get the age of the reservoir. the lifetime of the reservoir can be calculated by the equation: 𝑇 = 𝑉 (𝐿×𝑆×𝐸) (3) with: t = lifetime of reservoir (year) v = dead storage volume (m3) l = watershed area (km2) s = erosion intensity = vs/l vs = the average volume of sediment entering the reservoir (ton/year) = ws/γd ws = the weight of the average sediment that enters the reservoir (ton/year) γd = the dry weight of the sediment deposits = 0.963 ton/m3 e = efficiency of reservoir catches civil and environmental science journal vol. 02, no. 01, pp. 001-014, 2019 4 2.2.5. land conservation direction vegetative methods or ways to utilize the role of plants in the effort to control erosion and/or preservation of soil, in the implementation can include the following activities: (a) forest restoration (reforestation) and reforestation, (b) planting cover crops, (c) planting crops in contour lines, (d) planting plants in strips, (e) rotating crops and (f) mulching and utilization of plant litter. in this research, vegetative handling efforts were carried out were forest restoration or forest area adjustment. forest area adjustment refers to map of central sulawesi forest area. check dam building (controlling dam) is a building built in river grooves with construction of soil filling material reinforced with a waterproof coating. check dam buildings have functions other than as sediment capture buildings, as well as building river bed control. 3. result and discussion 3.1. hydrological analysis consistency test the method of testing with the dual mass curve method is to compare the long-term annual rainfall data from a raindrop station with the average rainfall data of a group of rain stations in the same period. if the test results state the data at a station is consistent, it means that there is no environmental change in the station's area of influence and no change in how to measure it during the recording of the data. figure 1. double mass curve chart of palolo station rain data figure 2. dual mass curve chart of sibalaya station rain data table 2. consistency test results of double mass curve method no rain station consistency test result gradient (r2) linier regression (y) angel gradient (tg α) 1 2 3 4 5 6 1 palolo 0.9896 y = 0.9621x 343.4 43.89° consistent 2 sibalaya 0.9896 y = 1.0286x + 442.9 45.81° consistent from figure 2, figure 3 and table 2 it can be concluded that the rainfall data at palolo and sibalaya stations is consistent data. civil and environmental science journal vol. 02, no. 01, pp. 001-014, 2019 5 if the rain station that affects the study area is less than 3 (three), then the test of the consistency of rainfall data is done by the method raps (rescaled adjusted partial sums). the recapitulation of the results of the consistency test of the raps method is presented in table 3. table 3. consistency test results raps method no rain station consistency test raps method q/n0.5 count < q/n0.5 table dan r/n0.5 count < r/n0.5 table result q/n0.5 count q/n0.5 table r/n0.5 count r/n0.5 table 1 2 3 4 5 6 7 1 palolo 0.72 1.07 0.96 1.26 consistent 2 sibalaya 0.55 1.07 0.88 1.26 consistent from table 3 above shows that value q/n0,5 count < value q/n0,5 table and value r/n0,5 count < value r/n0,5 table, so that it can be concluded that the rainfall data at palolo and sibalaya stations is consistent data. homogeneity test in this study, the annual rainfall data of the rain station were tested for the absence of trends with the spearman method using 2-sided t-test. recapitulation of test results is presented in the following. table 4. trend absence test results no. rain station trend absence test (t count < t table) result t count value t table value 1 2 3 4 5 1 palolo -1.367 2.179 trend absence 2 sibalaya 0.391 2.179 trend absence from table 4 above shows that the value of t arithmetic < value of t table, so it can be concluded that the rainfall data on palolo and sibalaya stations includes independent data (rt and tt are not interdependent). periodic series is called stationary if the values of the statistical parameters (mean and variant) are relatively unchanged (stable) from the period or the time series. if one of the statistical parameters is found to change from the part of the period or the amount of time available, the periodic series is called not stationary. non-stationary periodic series indicates that the data is not homogeneous or not the same type. testing the variance value from the periodic series can be done with the f-test. recapitulation of test results is presented in the following. table 5. stationary test results no rain station stationary test f count < f table dan t count < t table result variability stability stability of average value f count f table t count t table 1 2 3 4 5 6 7 1 palolo 2.24 3.79 -0.41 2.18 homogeneous 2 sibalaya 0.61 3.79 0.37 2.18 homogeneous civil and environmental science journal vol. 02, no. 01, pp. 001-014, 2019 6 from table 5 above shows that the calculated f value < f table value and t count value <t table value, so it can be concluded that the rainfall data at palolo and sibalaya stations has a variant and a stable average. the persistence test is an independent test of each value in a periodic series. first, the number of serial correlation coefficients must be calculated with the spearman method, then the calculation of the persistence test with the t-test is carried out. recapitulation of test results is presented in the following. table 6. recapitulation of the test of presence no rain station presence test (t count < t table) result t count value t table value 1 2 3 4 5 1 palolo -0.330 2.201 random 2 sibalaya -1.405 2.201 random figure 3. palolo station outliers test chart. figure 4. sibalaya station outliers test chart 0 20 40 60 80 100 120 140 a n n u a l r a in fa ll d a ta ( m m ) year maximum daily rainfall (mm) upper limit lower limit 0 20 40 60 80 100 120 140 160 180 200 a n n u a l r a in fa ll d a ta ( m m ) year maximum daily rainfall (mm) upper limit lower limit civil and environmental science journal vol. 02, no. 01, pp. 001-014, 2019 7 from table 6 above shows that the value of t count < t table value, so it can be concluded that the rainfall data at palolo and sibalaya stations shows the absence of trends, variants and homogeneous/stable/same type, and are random (randomness), independent. abnormalities test (outliers) outliers test is used to find out whether the maximum data and minimum data from the available data sets are suitable for use or not. from figure 3 and figure 4 it is found that the rainfall data for palolo and sibalaya stations is still in the range of thresholds. so, it can be concluded that the rain data is of high quality. figure 5. land use changes graphic in 2012 up to 2014 the area of natural forest that was converted into residential, natural forest, fields/moor, mixed plantations and shrubs covering an area of 125.94 ha. the biggest change became shrub land area of 36.48 ha (28.97%). in addition to being a field/moor area of 34.74 ha (27.58%), it became a mixed plantation of 28.22 ha (22.41%) and a settlement of 26.5 ha (21.04%). year 2014 to 2016 the area of natural forest that has changed function into residential, natural forest, fields/moor, mixed gardens and shrubs covering an area of 148.5 ha. the biggest change was the scrub land area of 45 ha (39.30%). besides that, it is a mixed garden covering 39 ha (34.06%), being a dry field area of 25.25 ha (22.05%) and a settlement of 5.25 ha (4.59%) (figure 5). erosion rate the swat simulation results, the erosion rate value continues to increase in each year period. the increase in erosion rate in 2010 was 72.5%, the period of 2010-2012 was 1.45%, 2012-2014 decreased by 0.09% and the period of 2014-2016 increased by 0.98%. it can be concluded that the period of 2008-2010 occurred over land conversion on natural forest land. new land clearing on 148.5 ha of mixed crops, shrub shrubs, farms/settlements and settlements. the biggest switch functions to be a mixed garden of 84.25 ha (figure 6 and figure 7). civil and environmental science journal vol. 02, no. 01, pp. 001-014, 2019 8 figure 6. graph of monthly erosion rate comparison of 2008, 2010, 2012, 2014 and 2016 figure 7. relation graph of changes in land use to the average erosion rate in this study an analysis of changes in land use to the extent of behi was carried out. changes in land use in this case are indicated by cn values. from the analysis, it was found that the increase in cn value resulted in an increase in the average erosion rate. so, it can be concluded that changes in land use that occur in the wuno sub-watershed greatly affect the rate of erosion that will occur. sediment from the swat simulation results it can be seen that there was an increase in the amount of sediment during 2008 to 2016. the largest increase occurred in the period 2008-2010, the amount of sediment produced increased by 114.6%. the period of 2010-2012 increased by 1.04%, 2012-2014 increased by 1.65% and 2014-2016 increased by 1.85% (figure 8). 3.2. bank erosion hazard index analysis the magnitude of the erosion hazard value is stated in the bank erosion hazard index (behi), which is defined by the potential erosion value (tons/ha/year) divided by the amount of erosion that can still be left. from the results of the 2008 behi classification, it can be seen that there are 4 (four) classes of erosion hazard indices in the wuno sub-watershed, namely low, medium, high and very high. civil and environmental science journal vol. 02, no. 01, pp. 001-014, 2019 9 from the table above, it can be seen that behi is very high, all of which occurs in the land use field/upland, settlements, mixed crops and shrub shrubs, while low behi takes place entirely in the use of natural forest lands. this shows that land use is very influential on behi (table 7). figure 8. graph of monthly sediment weight comparison of 2008, 2010, 2012, 2014 and 2016 table 7. recapitulation of behi no behi 2008 2010 2012 2014 2016 area (ha) % area (ha) % area (ha) % area (ha) % area (ha) % 1 2 3 4 5 6 7 8 9 10 11 12 1 low 12,906.50 78.55 12,769.70 77.72 12,638.80 76.92 12,523.00 76.22 12,424.00 75.61 2 medium 1,239.35 7.54 1,297.06 7.89 1,346.44 8.19 1,372.03 8.35 1,414.21 8.61 3 high 477.46 2.91 512.83 3.12 535.12 3.26 555.54 3.38 556.56 3.39 4 very high 1,807.69 11.00 1,851.41 11.27 1,910.64 11.63 1,980.43 12.05 2,036.23 12.39 sum 16,431 100 16,431 100 16,431 100 16,431 100 16,431 100 in this study an analysis of changes in land use to the extent of behi was carried out. changes in land use in this case are indicated by cn values. from the analysis, it was found that the increase in cn value resulted in an increase in the behi of medium, high and very high. on the contrary, the increase in cn value has an effect on the decrease in the low behi area. so, it can be concluded that changes in land use that occur in the wuno sub-watershed are very influential on the behi area that will occur figure 9 – 17). civil and environmental science journal vol. 02, no. 01, pp. 001-014, 2019 10 figure 9. behi land use distribution map for 2008 figure 10. behi land use distribution map for 2010 figure 11. behi land use distribution map for 2012 figure 12 behi land use distribution map for 2014 figure 13. behi land use distribution map for 2016 figure 14. graph of relation of changes in land use to very high behi. civil and environmental science journal vol. 02, no. 01, pp. 001-014, 2019 11 figure 15. graph of relation of changes in land use to high behi figure 16. graph of relation of changes in land use to medium behi. figure 17. graph of relation of changes in land use to low behi. 3.3. reservoir lifetime analysis the parameters used to calculate the useful life of the reservoir are the volume of dead reservoir (m3), area of watershed (km2), average weight of sediment entering the reservoir (ton/year), content of dry sediment deposits (0.963 ton/m3) and sediment capture efficiency. in addition to sediment capture civil and environmental science journal vol. 02, no. 01, pp. 001-014, 2019 12 efficiency, other parameters are known. to calculate the efficiency of sediment capture, the brune method and churchill method are used. from the nomogram of brunne and churchill equations, the sediment trapped is 98% of the volume of sediment entering the reservoir. so that the sediment released is only 2%. figure 18. graph of relation of changes in land use to reservoir lifetime. from the calculation above, it was found that the wuno reservoir use age using the brune method was 9.52 years while using the churchill method was 9.52 years (figure 18). in this study an analysis of changes in land use to the useful life of reservoirs was carried out. changes in land use in this case are indicated by cn values. the useful life of the reservoir is shown using the brune and churchill methods. 3.4. land conservation direction vegetative method in this research, vegetative handling efforts were carried out were forest restoration or forest area adjustment. adjustment of forest area refers to map of forest areas of central sulawesi province. the results of overlaying the map of the central sulawesi province forest area with land use in 2016, there is a mismatch of forest functions. on the map of the central sulawesi province forest area the land designated as limited production forest, but in the field is a mixed garden and shrub. in addition there is a land designated as protection forest, in the field is used as a mixed garden. to determine the extent to which the effectiveness of vegetative methods in reducing sedimentation that occurred in the wuno sub-watershed, a simulation was carried out based on the map of the central sulawesi province forest area. from the simulation results, the amount of sediment produced is 209,942.15 tons/year. the amount of sediment decreased by 353,605.52 tons/year (62.75%) compared to 2016. where the amount of sediment in 2016 was 563,547.67 tons/year. this has a positive impact on the amount of sediment entering the reservoir. the smaller the amount of sediment that enters the reservoir every year will certainly extend the useful life of the reservoir. mechanical method based on the reservoir utilization age, the useful life of wuno reservoir is 9.52 years, while the reservoir is planned to be operational for 50 years. by trial and error, to reach the age of 50 years plan, the weight of sediment that can enter the reservoir every year is 105,000 tons/year from the total civil and environmental science journal vol. 02, no. 01, pp. 001-014, 2019 13 weight of sediment in 2016 of 563,547.67 tons/year. thus, the sediment that must be prevented from entering the reservoir is 458,547.67 tons/year (figure 19). placement of buildings or locations of sediment control structures is placed in areas that contribute large sediments to the river based on sub-watersheds that have a high and very high erosion hazard index. at the sub-watershed outlet with a high and very high erosion hazard index, a check dam will be planned. figure 19. comparison of 2016 land use sediment amounts with vegetative land management. from the analysis results obtained 6 (six) check dam locations with the total volume of sediment collected is 502,920.12 tons/year or 484,312.07 m3/year (figure 20). figure 20. map of check dam location. civil and environmental science journal vol. 02, no. 01, pp. 001-014, 2019 14 4. conclusions based on the results of analyzing, the rate of erosion and the extent of behi are influenced by changes in land use. land use changes also affect the reduced useful life of the reservoir. vegetative land conservation efforts are adjusting forest areas so that rate of erosion decreases by 62.75%. mechanical land conservation efforts in the form of the construction of 6 check dams so that weight of sediment decreases by 89.24%. references [1] achsan. 2015. analisis kecenderungan sedimentasi waduk bili-bili dalam upaya keberlanjutan usia guna waduk. thesis. jurnal teknik pengairan 6 (1), p 30-36. [2] ahmed moustofa ahmed moussa. 2012. predicting the depositian in the aswan high dam reservoir using a 2-d model. ain shams university, 4, p 143-153 [3] asmaranto, r., suhartanto, e., yuanita, m. 2012. aplikasi model avswat 2000 untuk memprediksi erosi, sedimentasi dan limpasan di das sampean. jurnal teknik pengairan 2 (1), p 79-85. [4] arsyad, sitanala. 2006. konservasi tanah dan air. bogor: ipb press [5] balai pengelolaan daerah aliran sungai dan hutan lindung palu poso. 2006. erosi das wuno tahun 1992 – 2006. [6] balai wilayah sungai sulawesi iii. 2015. fs waduk wuno. [7] balai wilayah sungai sulawesi iii. 2016. dd bendungan wuno. [8] haribowo, r., yoshimura, m., sekine, m., imai, t., yamamoto, k., higuchi, t., kanno , a. 2017. behavior of toxicity in river basins dominated by residential areas. contemporary engineering sciences 10 (7), p 305-315. [9] kartasapoetra g., et all. 1987. teknologi konservasi tanah dan air. jakarta: pt. bina aksara. [10] md shahriar pervez, geoffrey m. henebry. 2015. assessing the impacts of climate and land use and land cover change on the freshwater availability in the brahmaputra river basin. journal of hydrology: regional studies, 3, p 285-311. [11] suhartanto, e., haribowo, r. 2011. application of kagan-rodda method for rain station density in barito basin area of south kalimantan, indonesia. journal of applied technology in environmental sanitation 1 (4), . [12] suharyanto, a., suhartanto, e., pudyono, p. 2013. the use of satellite remote sensing data and geographic information systems on critical land analysis. agrivita, journal of agricultural science 35 (2), p 119-126. [13] sulfandi. 2015. studi pengaruh perubahan tataguna lahan di das mamasa terhadap usia guna waduk plta bakaru. jurnal teknik pengairan 7 (1), p 139-149. [14] temesgen gashaw, taffa tulu, mekuria argaw, abeyou w. worqlu. 2018. modeling the hydrological impacts of land use/land cover changes in the andassa watershed, blue nile basin, ethiopia. science of the total environment, 619–620, p 1394-1408. template jurnal teknik pengairan civil and environmental science journal vol. 4, no. 2, pp. 115-126, 2021 115 estimation of flow discharge model at temef watershed east nusa tenggara using trmm satellite data aprianto nomleni1, ery suhartanto1, donny harisuseno1 1water resources engineering department, faculty of engineering, universitas brawijaya, malang, 65145. indonesia. anto_nom@yahoo.com1 received 22-03-2021; accepted 04-05-2021 abstract. data collection based on satellite trmm (tropical rainfall measuring mission) presents one of the best alternatives in estimating rainfall. trmm technology can minimize manual rainfall recording errors and improve rainfall accuracy for hydrological analysis. the analysis method used in this research is divided into 3 (three) stages, hydrological analysis, statistical analysis and artificial neural network analysis. the trmm jaxa analysis results in the temef watershed area obtained trmm jaxa satellite rainfall relationship to observation data shows rainfall patterns between the two data are interconnected. however, for cases with very high observation rainfall, trmm rainfall data tend to be low. from the statistical method analysis, the relationship between observed rainfall and trmm jaxa rainfall obtained results with a "very strong" interpretation indicated by the results of 9 years calibration and 1 year validation where the selected equation is a polynomial equation (y = 0.0123x2 + 1.5553x + 20.222). rain data correction results simulated with debit data to see the relationship between rain and discharge that occurred, this analysis using artificial neural network with backpropagation method, the results showed a "strong" interpretation where statistically the value of nash-sutcliffe efficiency (nse) is 0.920. the coefficient correlation is 0.877 and the relative error that occurred is 2.62%. keywords: artificial neural network, flow discharge, trmm jaxa 1. introduction east nusa tenggara province has four large islands, one of which is the island of timor with an area of ±14.200 km2 [1]. climate conditions in east nusa tenggara are close to australia, wind currents containing a lot of moisture from asia and the pacific ocean in the east nusa tenggara region, so that the rainy days in east nusa tenggara are fewer than in areas close to asia [7,13]. east nusa tenggara has dry climates, namely: climate type d3 (3-4 wet months and 4-6 dry months), climate type d4 (3-4 wet months and > 6 months dry), climate type e3 (6 dry months) [12]. therefore, rainfall occurs in thunderstorms only a few times, causing flash floods and uncontrollable erosion, water is quickly dumped into the sea and little seeps into the ground. 1 cite this as: nomleni, a., suhartanto, e., & harisuseno, d. (2021). estimation of flow discharge model at temef watershed east nusa tenggara using trmm satellite data. civil and environmental science journal (civense), 4(2), 115-126. doi: https://doi.org/10.21776/ub.civense.2021.00402.2 civil and environmental science journal vol. 4, no. 2, pp. 115-126, 2021 116 based on data from presidential decree no. 12 of 2012. one of the rivers in the province of east nusa tenggara, precisely in the south central timor regency is included in the benanain river region and noelmina river region. during the dry season, the large river area is relatively dry, while during the rainy season the water volume increases [18]. as a region with low rainfall, rainfall data in east nusa tenggara are often incomplete. obstacles and problems that are still often encountered are the lack of space and time for observation of rainfall data, as well as the availability of time series and rainfall data that is not long enough and incomplete. in addition, the number of rain stations is uneven, and the lack of observers. observation and data recording system is still done manually, data collection from certain areas to the central level is still hampered and running slowly, and the data format is not yet standard [10]. satellite-based rainfall capture presents an alternative way that can measure rainfall through spacecraft sensors and algorithms [11]. satellite-based rainfall data are widely used due to the relatively high accuracy rate [14], e.g. tropical rainfall measuring mission (trmm) or multi-satellite rainfall product analysis (tmpa) data. trmm satellite used is jaxa (japan aerospace exploration agency) with data type gsmap near-real-time which has a spatial resolution of 0.1° x 0.1° lat/long and temporal resolution of 1 hour [2]. water discharge data in indonesia are still inadequate. this is due to various factors, including floods and landslides, as well as damage to hydrological temperature measurement stations caused by labor. one of the watersheds with insufficient data is the temef watershed in tts regency, east nusa tenggara. flood conditions during the rainy season in the temef watershed caused material losses, especially in and around malacca regency. while the hot conditions in the dry season, resulting in drought. this indicates a problem of debit fluctuations. the calculation of water availability is necessary to determine the capacity of the water source [9]. the latest discharge analysis in the field of hydrology in indonesia is the artificial neural network method [8]. conveying artificial neural network (ann) is a form of artificial intelligence that has been widely applied in the field of water resources. the application of ann in the field of water resources has been widely used for discharge analysis [17]. the rain-flow simulation method in discharge analysis can describe the hydrological process. hence, the quality and quantity of rainfall data become the main consideration to acquire high accuracy of estimated discharge in a river [4-6]. rainfall will be divided into several processes, some will experience evaporation, others become surface runoff, and some become infiltration and percolation [3]. the stages of building an artificial neural network (ann) model are training and testing [16]. the ann (artificial neural network) method is expected to identify the characteristic parameters of watersheds and most appropriately used in areas such as an east nusa tenggara province, especially areas with low rainfall [15]. 2. materials and methods 2.1 materials the research objects reviewed were trmm jaxa data and rainfall stations located in south central timor regency and north central timor regency. there are 3 observation rainfall stations in the object of research, namely nifukani, batinifukoko, and noelnoni (figure 1). data in the research includes trmm jaxa data (2009-2018) gsmap_nrt version 6 which can be accessed through trmm jaxa (ftp://hokushai.eorc.jaxa.jp), rainfall data obtained from the public works office of east nusa tenggara province (2009-2018), tma discharge data (2009-2018), topographic and administrative map data sourced from the public works north central timor district office. civil and environmental science journal vol. 4, no. 2, pp. 115-126, 2021 117 figure 1. temef watershed timor tengah selatan regency 2.2 methods 2.2.1 hydrological analysis a. consistency test the purpose of the consistency test is to determine the irregularities that occur in each rain station post with the other rain station posts in the vicinity, this test uses a double mass curve for observation and trmm jaxa stations [3,9,18]. b. homogeneity test the homogeneity was employed to ensure the number of populations to be measured is homogeneous. the homogeneity test was conducted on both observation stations and trmm jaxa rainfall data includes trend absence test, stationary test, and persistence test [3,9,18]. c. regional rainfall analysis of average rainfall area has an objective to obtain a value that presents the amount of rain in one particular region. the thiessen polygon method was used to analyze average areal rainfall [9]. 2.2.2 statistical analysis statistical analysis includes calibration analysis, verification, and validation using statistical analysis [9], this analysis uses several statistical functions including the following: civil and environmental science journal vol. 4, no. 2, pp. 115-126, 2021 118 a. nash sutcliffe efficiency (nse) : 𝑁𝑆𝐸 = 1 − ∑ (𝑥𝑖 − 𝑦𝑖 ) 2𝑛 𝑖=1 (𝑥𝑖 − 𝑦𝑖 ) 2 with: xi = observation data (actual data) yi = estimation data (estimation result data) xi = average observation data n = the number of data b. correlation coefficient 𝑟 = 𝑛 ∑ 𝑥𝑖 𝑦𝑖 − ∑ 𝑥𝑖 ∑ 𝑦𝑖 𝑛 𝑖−1 𝑛 𝑖−1 𝑛 𝑖−1 √𝑛 ∑ 𝑥𝑖 2 −𝑛𝑖−1 (∑ 𝑥𝑖 𝑛 𝑖−1 ) 2 √𝑛 ∑ 𝑦𝑖 2 −𝑛𝑖−1 (∑ 𝑦𝑖 𝑛 𝑖−1 ) 2 xi = observation data (actual data) yi = estimation data (estimation result data) n = the number of data c. root mean squared error (rmse) 𝑅𝑀𝑆𝐸 = √ ∑ (𝑥𝑜𝑏𝑠,𝑖 − 𝑦𝑚𝑜𝑑𝑒𝑙,𝑖 ) 𝑛 𝑖−1 2 𝑛 xi = observation data (actual data) yi = estimation data (estimation result data) n = the number of data d. relative error 𝐾𝑅 = ∑ (𝑥 − 𝑦)𝑛𝑖−1 ∑ 𝑦 𝑥 100 xi = observation data (actual data) yi = estimation data (estimation result data) 2.2.3 artificial neural network (ann) ann (artificial neural network) analysis uses a matlab program that serves to model field debit data [3,15]. this data input consists of rainfall, amount of rainy day, and runoff coefficient data. the present study employed the backpropagation method which is a method to solve complicated problems because it has a good level of accuracy [16,17]. 3. results and discussion 3.1 trmm and observation data based on the results of trmm jaxa analysis and observation obtained graphs of the relationship of the two data. the graph and comparison shows that observation rains occur higher than trmm rain for conditions with high rain intensity at the end and the beginning of the year, this happened at three rainfall stations (figure 2) civil and environmental science journal vol. 4, no. 2, pp. 115-126, 2021 119 figure 2. graph observed rainfall data and trmm jaxa batinifukoko station result in the comparison of data from the batinifukoko station and trmm station shows that the trmm data is quite low, the resulting data are less than 100 mm, this data is relatively consistent every year, while the observation data shows that rain data varies with an intensity of up to 200 mm (figure 3). figure 3. comparison of observed rainfall data and trmm jaxa batinifukoko station the results of the observation rainfall graph and trmm rainfall for the nifukani station show low rainfall data at the trmm station when the rainfall at the observation station is high (figure 4). and comparing the distribution of trmm rainfall data and observation that are less consistent, results of trmm rainfall are below 100 mm, observation rainfall intensity reached 100 mm to 200 mm (figure 5) 0.0 50.0 100.0 150.0 200.0 250.0 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 r a in fa ll ( m m ) time (years) trmm rainfall observation rainfall station 0.0 50.0 100.0 150.0 200.0 250.0 0.0 50.0 100.0 150.0 200.0 250.0 o b se rv a ti o n r a in fa ll ( m m ) trmm rainfall (mm) civil and environmental science journal vol. 4, no. 2, pp. 115-126, 2021 120 figure 4. graph observed rainfall data and trmm jaxa nifukani station figure 5. comparison of observed rainfall data and trmm jaxa nifukani station the results of the observation rainfall graph and trmm for the noelnoni station show low rainfall data at the trmm station when the rainfall at the observation station is high (figure 6). and comparing the distribution of trmm rainfall data and observation that are less consistent (figure 7) 0.0 50.0 100.0 150.0 200.0 250.0 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 r a in fa ll ( m m ) time (years)trmm rainfall observatio rainfall staton 0.0 50.0 100.0 150.0 200.0 250.0 0.0 50.0 100.0 150.0 200.0 250.0 o b se rv a ti o n r a in fa ll ( m m ) trmm rainfall (mm) civil and environmental science journal vol. 4, no. 2, pp. 115-126, 2021 121 figure 6. graph observed rainfall data and trmm jaxa noelnoni station figure 7. comparison of observed rainfall data and trmm jaxa noelnoni station 3.2 data correction data calibration was conducted upon uncorrected trmm rainfall data and corrected trmm rainfall data by dividing the data into 4 groups with a comparison of 10 years of data or uncorrected data and 7:3 years, 8:2 years, 9:1 years. trmm rain data analysis is done by calibration method with data length for 10 years with uncorrected data, obtained observation rain data relationship for 10 years and trmm jaxa data, namely "weak". obtained several statistical analysis values, namely root mean squared error (rmse) = 31.934; nash sutcliffe efficiency (nse) = -0.285; relative error (kr) = 74.022 % and correlation coefficient (r) = 0.542. so based on the results above it is necessary to re-verify to get equations with good interpretation value (table 1). based on calibration analysis of uncorrected trmm data with rain station post data with four methods, namely rmse, nse, relative error, and correlation coefficient it can be concluded that calibration results show "weak" interpretation. calibration analysis of 10 years, 9 years, 8 years, and 7 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 r a in fa ll ( m m ) time (years) trmm rainfall observation rainfall station 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 o b se rv a ti o n r a in fa ll ( m m ) trmm rainfall (mm) civil and environmental science journal vol. 4, no. 2, pp. 115-126, 2021 122 years, as well as validation analysis of rain data of 3 years, 2 years, and 1 year were conducted to obtain correction equations for rain data (table 2). table 1. data calibration summary results period calibration validation equation selected equation type numberof years value r2 verification montly 7 years 0.3077 3 years y = -0.0142x2 + 1.71x + 20.03 polynomial 8 years 0.2980 2 years y = -0.0121x2 + 1.572x + 20.101 polynomial 9 years 0.3032 1 year y = -0.0123x2 + 1.555x + 20.222 polynomial 10 years 0.3184 the scatter plot validation results for each rain data are shown in the graphic image of the rainfall relationship below, this graph illustrates the results of equations obtained from validation of 3 years, 2 years, and 1 year. figure 8 figure 9 and figure 10 showing the scatter plot validation graph. 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 0.00 20.00 40.00 60.00 80.00 o b sr e v a ti o n r a in fa ll ( m m ) trmm rainfall (mm) 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 0.00 20.00 40.00 60.00 80.00 100.00 o b se e r v a ti o n r a in fa ll ( m m ) trmm rainfall (mm) r2 =0.668 figure 8. scatter plot validation for correct data period 3 years polynomial equations 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 0.00 20.00 40.00 60.00 80.00 100.00 o b se r v a ti o n r a in fa ll ( m m ) trmm rainfall (mm) figure 9. scatter plot validation for correct data period 2 years polynomial equations figure 10. scatter plot validation for correct data period 1 year polynomial equations r2 =0.733 r2 =0.877 civil and environmental science journal vol. 4, no. 2, pp. 115-126, 2021 123 table 2. data validation summary results period number of years rmse nse kr r value interpretation value interpretation monthly 3 years 20.16 0.674 meet 7.03 % 0.668 weak 2 years 18.65 0.782 meet 3.44 % 0.733 strong 1 year 13.699 0.920 meet 2.62 % 0.877 very powerful 0 year 31.933 -0.285 does not meet 74.02 % 0.542 weak from table 2, the results of the calibration data for 9 years verification and validation 1 year create equal relationships r2 higher than others (7:3. 8:2. and 10 years). the verification results to get the relationship r2 = 0.877. shows that the correlation is very good, that is above 0.60. the data validation obtained the equation y = -0. 0123x2 + 1.555x + 20.222 (polynomial equation) with the interpretation of "very strong". the rmse value is influenced by the amount of data and the difference between the observed data and the simulation data. the longer the data range, the greater the effect of the rmse value. validation with a data length of 3 years has the greatest value compared to data lengths of 2 years and 1 year. the method of 1 year, 2 years, and 3 years indicates the interpretation of "fulfilling". based on the criteria of the nse method, if the nse value is closer to the value of 1 then the better the model. while the result of validation is > 0.5. so it can be concluded that the results meet and the model is good for validation of 1. 2 and 3 years. the amount of relative error value of correcting data validation in all periods and time frames ranges from about 2.00% 7.00% so it can be said that corrected trmm rainfall data has a relatively small error rate when compared to observation post rainfall data. the result of the correlation coefficient method shows the relationship between trmm rainfall data and observation post rainfall data is relative "very strong" in the period and the time span of 1 year. the coefficient value is closer to the value of 1. the better the correlation between the two data. based on the analysis resulting from the comparison between uncorrected trmm data validation and corrected trmm data, it can be concluded that the corrected trmm data is closer to the rainfall value of the rain station post which is considered as the correct data. thus, it can be concluded that trmm rainfall data can be used as an alternative hydrological data for use in planning in the field of water resources. the result of 9 years of data verification and 1-year data validation is considered as the result with the best data relationship so that it is used for advanced analysis. equation y = -0. 0123x2 + 1.555x + 20.222 (polynomial equation) is used to correct trmm rain data that occurs. 3.3 artificial neural network analysis rain data are simulated by a discharge that comes out using the artificial neural network (ann). from the data is prepared variables for input matlab data (figure 11), sample data, and target data containing variables, including corrected trmm rainfall, flow coefficients, and rainy days. the data are simulated to get the discharge data that occurs. the results of the analysis showed train data validation data and test data and show the same pattern, proved that the result of the iteration is good (figure 12). the results of the neural network training state analysis are good, it is obtained from the number of iterations (figure 13) and reliability of discharge with a correlational relationship for training was 0.989, and test results are 0.99 "very good" (figure 14). civil and environmental science journal vol. 4, no. 2, pp. 115-126, 2021 124 table 3. result of summary of trmm jaxa rain data validation (9:1) to debit data nse kr r value interpretation value interpretation debit 10 years 0.887 meet 9.04 % 0.827 strong from table 3, these results are validated with sample data that will look at the relationship of data used results, so that it can be concluded that corrected trmm rain has a "strong" interpretation figure 11. backpropagation method in artificial neural network analysis figure 12. results of neural network performance analysis figure 13. results of neural network training state analysis figure 14. results of neural network regression analysis civil and environmental science journal vol. 4, no. 2, pp. 115-126, 2021 125 where the nse relationship is 0.887. the correlation coefficient of discharge and precipitation is 0.827 and the relative error is 9.04 so that the trmm data has a correlation relationship with the debit data that occurs in the field. 4. conclusion from the results of the analysis can be concluded that the relationship of trmm jaxa satellite rainfall to observation data shows a pattern and intensity approaching between the two rainfall data, but observation rainfall data shows higher intensity than trmm data. overestimate occurs in observational rainfall compared to trmm rainfall, especially during the rainy season in the end and the beginning of the year. trmm satellite data tend to underestimate in the rainy season and is quite close to observation data in the dry season. the results of verification and validation with a "very strong" interpretation are indicated by the results of 9 years verifiable and 1-year validation where the results of verification of 9 years data show a correlation between observed rainfall and trmm jaxa rainfall is 0.877. 1-year validation indicates "very strong" interpretation with an nse value is 0.920, relative error is 2.63%, and rmse is 13.699 with selected equation is a polynomial equation (y = 0.0123x2 + 1.5553x + 20.222). the results of 8 data verification and 2-year validation showed a "strong" interpretation. where the correlation between observed rainfall and trmm rainfall was 0.733. 2-year validation indicates "strong" interpretation with an nse value is 0.782. relative error is 3.44%, and rmse is 20.16 with the selected equation is a polynomial equation (y = -0.0121x2 + 1.572x + 20.101). the results of 7 years of verification and 3 years of validation showed a "weak" interpretation. where the correlation between observational rainfall and trmm rainfall was 0.668. 3year validation obtained nse value is 0.674, relative error 7.03 %, and rmse is 20.16 with the selected equation is a polynomial equation (y = -0.0142x2 + 1.71x + 20.03). while for data results without correction shows a "weak" result with a low correlation value of 0.542 and a large relative error of 74.02%. results of discharge in ann method based on rain from trmm jaxa (japan aerospace exploration agency) simulation training and artificial neural network testing showed "strong" results where nse relationship was 0.887. coefficient of discharge and precipitation correlation was 0.872 and relative error was 9.045. reference : [1] badan pusat statistik (bps), 2018. propinsi nusa tenggara timur dalam angka, 0215-2223 [2] earth observation research center (eorc), japan aerospace exploration agency (jaxa), (2018) user’s guide for global rainfall map in near-real-time by jaxa global rainfall watch (gsmap_nrt), version 3.2 [3] ery suhartanto, evi nur cahya, lu’luil maknun, analisa limpasan berdasarkan curah hujan menggunakan model artifical neural network (ann) di sub das brantas hulu, jurnal teknik pengairan, vol 10. no 2 (2019), pp. 134-144. doi https://doi.org/10.21776/ub.pengairan.2019.010.02.07 [4] harisuseno, d. (2020a). kajian kesesuaian rumus intensitas hujan dan kurva intensitas durasi frekuensi ( idf ) di wilayah kampus universitas brawijaya , malang. media komunikasi teknik sipil, 26(2), 247–257 [5] harisuseno, d., suhartanto, e., & cipta, d. m. (2020). rainfall-streamflow relationship using stepwise method as a basis for rationalization of rain gauge network density. international journal of recent technology and engineering, 8(5), 3814–3821. https://doi.org/10.35940/ijrte.e6617.018520 [6] harisuseno, d., wahyuni, s., & dwirani, y. (2020). penentuan formulasi empiris yang sesuai untuk mengestimasi kurva intensitas durasi frekuensi. jurnal teknik pengairan, 11(1), 38– 48. https://doi.org/10.21776/ub.pengairan.2020.011.01.06 [7] harisuseno. (2020). meteorological drought and its relationship with southern oscillation index (soi), civil engineering journal, vol. 6, no. 10, pp. 1864–1875. civil and environmental science journal vol. 4, no. 2, pp. 115-126, 2021 126 [8] hasihardaja, sugeng (2005) pemodelan curah hujan-limpasan menggunakan artificial neural network (ann) dengan metode backpropagation, civil engineering journal vol.12 no 4. [9] lufi suryaningtyas, suhartanto ery, rispiningtati, hydrological analysis of trmm (tropical rainfall measuring mission) data in lesti sub watershed, jurnal, vol 3. no 1 (2020), pp. 18-30 doi https://doi.org/10.21776/ub.civense.2020.00301.3 [10] mamenun et al (2014) validasi dan koreksi data satelit trmm pada tiga pola hujan di indonesia, jurnal meteorologi dan geofisika vol. 15 no. 1-2014 : 13-23 [11] maulana, h., suhartanto, e., & harisuseno, d. (2019). analysis of water availability based on satellite rainfall in the upper brantas river basin. international research journal of advanced engineering and science, 4(2), 393–398. [12] oldeman, r.l., irsal las, and muladi. 1980. the agro-climatic maps of kalimantan, maluku, irian jaya, and bali west and east nusa tenggara contrib. no.60. centr. res. inst.agrc. bogor. [13] priyanto dwi, 2016 strategies to return east nusa tenggara as a source of beef cattle, jurnal litbang pertanian vol 35 no 4 december 2016:167-168 [14] sahoo, a.k., shefeld, j., pan, m., wood, e.f., 2015. evaluation of the tropical rainfall measuring mission multi-satellite precipitation analysis (tmpa) for assessment of large-scale meteorological drought. remote sens. environ. 159. 181–193. [15] syarief fathoni, very dermawan, ery suhartanto, analisis efektivitas kerapatan jaringan pos stasiun hujan di das kedungsoko dengan menggunakan jaringan saraf tiruan (artificial neural network), jurnal teknik pengairan, vol 7. no 1 (2016), pp. 129 – 138. [16] tarigan, g, h et al,. (2014) analisa prediksi data debit runtun waktu menggunakan jaringan syaraf tiruan algoritma backpropagation (studi kasus das indragiri); jom engineering faculty; volume 1 no. 2 october 2014. [17] vd oktoprianica, e suhartanto, s wahyuni, analisa curah hujan terhadap debit limpasan menggunakan metode jaringan syaraf tiruan (jst) backpropagation di das welang, (2020) jurnal teknik sipil 9 (2), 301-314. [18] welkis et al, (2020), characteristics of flood water level based on hydrologic soil group analysis in temef watershed, iop conference series: earth and environmental science, 437 (2020) 012005. open access proceedings journal of physics: conference series civil and environmental science journal vol. i, no. 02, pp. 062-069, 2018 62 rainwater harvesting as alternative source for wudlu water in indonesia gatot eko susilo1 1civil engineering dept., universitas lampung, bandar lampung, 35145, indonesia gatot89@yahoo.ca received 01-08-2018; revised 31-08-2018; accepted 24-09-2018 abstract. indonesia is the country with the largest muslim population in the world. and as a country with muslim big population clean water for wudlu or purification must be available. rainwater holds potential as an alternative source of wudlu water. rainwater harvesting (rwh) for religious water supply is still very rare studied. based on this, the research in this paper aims to calculate the potential supporting capacity of rainwater as an alternative source of wudlu water. supporting capacity of rainwater harvesting (scrwh) in this study was calculated by simulating inflow and outflow behavior at a rainwater harvesting facility in a mosque. case study takes place at nurul iman mosque in southern lampung. the mosque has an area of 168 m2 and able to accommodate 300 worshipers. research show that the most effective reservoir size in the rwh facility in the observed mosque is between 15 to 30 m3 with scrwh for wet years between 65% and 70% and for dry years between 44% and 53%, respectively. the availability of wudlu water in a mosque basically cannot be expected 100% comes from rain water only. in the application of rwh in a mosque the maintenance of the rwh facility must be undertaken well. keywords: rainwater harvesting, alternative source, muslim, wudlu water. 1. introduction indonesia is a country rich in natural resources, including water resources. the sources of water in indonesia are mostly from forest areas, mountains, and areas that have a high intensity of rainfall. these water sources then flow into rivers and lakes or other bodies of water that many people use to meet daily needs. based on the release issued by map of the world in 2014 indonesia is still included in the category of 10 countries that have the largest freshwater reserves in the world. in the release, indonesia was ranked 7th with freshwater reserves of 2019 billion cubic meters. this position is still above india, peru, and venezuela whose reserves are slightly below 2000 billion cubic meters [6]. nevertheless, indonesia is still overshadowed by the future crisis of water supply. as a developing country whose population is growing rapidly from year to year, the need for clean water is also always increasing dynamically. on the other hand, the existence of water sources increasingly more threatened by human activities themselves. this causes a limited amount of water that can be utilized for life. deforestation causes flooding in the rainy season and drought in the dry season. at the same time, the continuous water pollution by industry and human activities makes more and more fresh water waste and unusable. civil and environmental science journal vol. i, no. 02, pp. 062-069, 2018 63 to face the future water supply crisis, environmental improvement needs to be done. the replanting of critical forests, restoration and maintenance of rivers, and community empowerment for the environment are methods that can be taken to preserve water quality and quantity. however, dynamic population growth still requires us to seek other water sources as an alternative source of water that can meet the needs of freshwater for the community. as a country whose bulk rainfall is quite large, around 2000 to 3000 mm/year [11], rainwater harvesting (rwh) is a viable option. rwh has been adopted and developed in many parts of the world where conventional water supply systems can no longer meet the water needs of the people [3]. rwh is basically a human activity for collecting and storing rainwater from various catchment areas such as roofs or other surfaces. rwh is an alternative to renewable clean water and is ideal for fulfilling domestic water supply [1]. based on the cia world factbook, the total population of indonesia in 2015 is 255.64 million people. with that amount, indonesia became the fourth most populous country in the world after china, india, and the united states. of the total population, about 87% of the indonesian population is muslim. at the present time indonesia is a country with the largest muslim population in the world. as a predominantly muslim country, one of the freshwater needs in the future is the need for water for islamic worship (wudlu). based on the literal translation, wudlu means clean and beautiful. while doing wudlu means using water on certain limbs in certain ways to remove mild dirt on the body. based on islam, wudlu is one of the requirements for the validity of prayer. or in other words people who pray without wudlu then the prayer are not valid. physically, the procedure of doing wudlu begins by washing both hands from the wrist up to the fingertips. this step is continued with gargling to clean the mouth. further step is washing the inside of the nose until clean. the next procedure is to wash the whole face and proceed with washing hands from elbows to fingertips. wudlu continued by wiping the forehead up to the crown of the head. the final part of the wudlu is to clean the ears thoroughly and wash the feet from the soles of the feet to the top of each ankle. every step is undertaken three times and should be done in sequence. the water requirements for each person's wudlu vary depending on the culture and availability of water. based on the ministry of public works of the republic of indonesia, the per capita wudlu water requirement is 16.2 liters per day. if this amount is divided by the number of prayers 5 times a day then this means a muslim need 3.24 liters of water for each wudlu. water used for wudlu is clean fresh water and water that can be used for wudlu according to islam is: rain water, sea water, water coming out of the spring-water, well water, river water, dew and snow. sea water is the greatest potential for wudlu water. but rarely people use sea water for wudlu because of psychological factors. the choice for other wudlu water sources is rain water. with considerable intensity every year in indonesia, rain water can be used as alternative source of wudlu water besides well water and river water commonly used during this time. although indonesia has significant rainfall intensity every year, the application of rainwater harvesting to be used as wudlu water has not been so popular. though actually began to appear some mosques began to lack wudlu water for the congregation. rainwater harvesting (rwh) is an activity to catch rainwater on a surface and channel it to be stored and used for various purposes. in countries rich in water, rwh facilities are made to conserve ground water. in arid or dry countries, rwh is applied to seek alternative domestic water sources. rainwater utilization through the application of rwh for religious water supply is still very rare. based on this, the research in this paper aims to calculate the potential supporting capacity of harvesting rainwater as an alternative source of wudlu water. supporting capacity of rainwater harvesting in this study was calculated by simulating inflow and outflow behaviour at a rainwater harvesting facility in a mosque. 2. material and methods a. rainwater harvesting facility for wudlu water supply in general, basic rainwater harvesting facilities (rwh) in a building consists of four parts. the first part is the rain catching section. this part of the water catchment area is the roof of the building. the civil and environmental science journal vol. i, no. 02, pp. 062-069, 2018 64 second part is the collecting and sending part of the rainwater. this section is responsible for collecting and sending rainwater from the catchment area to the reservoir. the third part is the rainwater storage section. this section is a reservoir that stores rainwater collected before use. the fourth part is the distribution. this section is in the form of pipes and pumps that function to distribute water from the reservoir to the service area. filters are a secondary part of an rwh facility. filters are installed in the rainwater collection section to separate the rainwater with debris and downstream of the reservoir to separate the rain water with fine dirt and remove the odor. the rwh facility in the mosque for wudlu water supply is not much different from the basic facilities of rwh. illustration of rwh facility in the mosque for wudlu water supply can be seen in the following figure: b. supporting capacity of rainwater harvesting to assess the success of a rainwater harvesting (rwh) application in a building, it is necessary to calculate the supporting capacity of the rwh (scrwh). scrwh is the ratio between the days whose water requirements can be met by rwh with the total number of days in a year. scrwh ranges from 0 to 100%. for example, a building in 2012 has a scrwh of 50%, meaning that within year 2012 the rwh of the building is capable of supplying water for 183 days from all days of the year (366 days). scrwh is highly dependent on the intensity of annual rainfall and the dimensions of rainwater storage reservoirs. to obtain the scwrh value, a water balance simulation involving the inflow, outflow and storage relationships must be performed. in detail the formula in rwh simulation is given as [4, 5, 7, 8, 9, 10]: st = st-1 + it – ot for 0 < st < smax (1) where: st = reservoir volume on day t (m3) st-1 = reservoir volume on day t-1 (m3), it = inflow on day t (m3) ot = is outflow on day t (m3) smax = maximum storage capacity (m3). the inflow is formulated as follows it = c.rt.a.1000 (2) where: c = runoff coefficient for roofs, the range value is ranged between 0.8 and 1.0 [2] rt = volume of rainfall on day t (mm) a = the area of roof (m2). the outflow for day t is calculated using formula below: the outflow is formulated as follows ot = nd (3) n = number of building occupants d = water demand per person per day if the reservoir volume on day t is greater than 0 then that day is considered as the day whose water demand has been fully supply by rainwater. civil and environmental science journal vol. i, no. 02, pp. 062-069, 2018 65 figure 1. rwh facility in the mosque for wudlu water supply c. case study the case study in this research takes place at nurul iman mosque which is located in dusun ii of sindangsari, natar village, natar district, south lampung regency. the mosque is a building with an area of 168 m2, two storeys, and able to accommodate as many as 300 worshipers. the first floor of the mosque is used for prayers and the second floor is the study room and library. rainfall data is taken from branti airport located not far from the study location. figure 2. location of study the data used in this study is the daily rainfall data of 2015 and 2016. year 2015 is considered to represent a dry year because annual rainfall is less than 2000 mm (1628.1 mm). year 2016 is considered to represent the wet year because its annual rainfall is more than 2000 mm (2317.6 mm). the performance of the data is given in figure 3 below. the simulation for calculating scrwh is done with the following data: • each wudlu every pilgrim spends about 5 liters of water. • every day there are 5 times of prayer: isya, subuh, zuhur, ashar, and maghrib. • at every isya prayer number of mosque pilgrims is 15% of the mosque's maximum capacity • at every subuh prayer the number of pilgrims is 5% of the mosque's maximum capacity • at every zuhr prayer the number of mosque worshipers is 10% of the mosque's maximum capacity • at every asr prayer the number of mosque worshipers is 5% of the mosque's maximum capacity • at every maghrib prayer the number of mosque worshipers is 20% of the mosque's maximum capacity civil and environmental science journal vol. i, no. 02, pp. 062-069, 2018 66 • on every friday every zuhr prayer the number of mosque pilgrims is 100% of the mosque's maximum capacity • in every year there are two prayers of the feast that is held by the pilgrims who number 100% of the mosque's maximum capacity especially in the month of ramadan, the congregation of the mosque changed to: • at every isya prayer number of mosque pilgrims is 60% of the mosque's maximum capacity • at every subuh prayer the number of pilgrims is 20% of the mosque's maximum capacity • at every zuhr prayer the number of mosque worshipers is 20% of the mosque's maximum capacity • at every asr prayer the number of mosque worshipers is 20% of the mosque's maximum capacity • at every maghrib prayer the number of mosque worshipers is 60% of the mosque's maximum capacity based on the data above, the wudlu water demand at the nurul iman mosque during the years 2015 and 2016 is given in figure 4. figure 3. daily rainfall data of branti airport for year 2015 and 2016 3. result and discussion simulations are operated using reservoir dimensions that vary from 4 to 50 m3. figure 5 shows the scrwh generated by various reservoir dimensions. the graph also shows that the most effective reservoir dimension is between 15 to 30 m3 with scrwh for wet years between 65% and 70% and for dry years between 44% and 53%, respectively. if the middle value is drawn then the most effective reservoir dimension is 22.5 m3 with scrwh 67.5% and 50.5% for wet and dry years, respectively. the fluctuation of water volume in the reservoir based on this reservoir dimension is presented in figure 6. figure 6 shows that from december to june the reservoir is always filled with water in both wet and dry years. in the dry year the reservoir will have minimum water savings in mid-june to middecember. in the wet year the minimum water savings occur only during the peak of the dry season in mid-july to mid-september. worship done in the month of ramadan in nurul iman mosque requires wudlu water is greater than the other months. ramadan is one of the months on the islamic calendar. in this month all muslims perform fasting and other more intensive worship in the mosque. the arabic calendar has a different time calculation with the international calendar based on the calculation of the christian calendar. therefore, the commencement of the month of ramadan each year is also different on the international calendar. this will also affect the water volume of the rwh civil and environmental science journal vol. i, no. 02, pp. 062-069, 2018 67 reservoir. if the month of ramadan falls in the rainy season then the influence on the fluctuation of water volume in rwh reservoir will not be too large. conversely, if the month of ramadan falls in the dry season then the volume of water in the reservoir rwh will reach a minimum point. figure 4. scrwh generated dimension from the simulation using various reservoir dimensions figure 5. the fluctuation of water volume in the reservoir using 22.5 m3 reservoir dimensions scrwh of mosque nurul iman will become even greater if not everyone takes wudlu water in the mosque. based on field surveys on friday or prayer in ramadhan, only 30% of pilgrims take wudlu water in the mosque. the rest of the pilgrims have done wudlu first in their homes. based on these circumstances, the scrwh of nurul iman mosque will be 58.90% and 82.79% for dry year and wet year, respectively, with a reservoir dimension of 22.5 m3. land availability is a matter to consider in making the rwh reservoir. reservoirs with dimensions of 22.5 m3 can be built in various shapes. reservoirs can be built on the ground, underground, or partly above the ground and partially underground. taking into account the area of land available in masjid nurul iman, the following recommended sizes for reservoirs with these dimensions are: • reservoir with length 4 m, width 3 m and height 2 m (volume 24 m3) civil and environmental science journal vol. i, no. 02, pp. 062-069, 2018 68 • reservoir with length 5 m, width 2 m and height 2,5 m (volume 25 m3) • reservoir with length 4 m, width 2 m and height 3 m (volume 24 m3) • reservoir with length 3 m, width 3 m and height 2,5 m (volume 22,5 m3) reservoir should be made of masonry plates or of thin concrete (ferrocement). reservoir should also be coated with anti-leaking paint to avoid water seepage and leaks. reservoir should also be equipped with facilities for maintenance such as manhole, stairs, and drainage holes. the availability of wudlu water in a mosque basically cannot be expected 100% comes from rain water only. in dry seasons, reservoirs must be filled with well water or ground water to avoid deficiency of wudlu water. to maintain the availability of wudlu water, people around the mosque should not take water from the mosque for daily necessities such as for bathing, washing, and sanitary purposes. another important thing to note in the application of rwh in a house of worship is the maintenance of the rwh facility itself. maintenance must be done periodically to maintain the smooth operation of rwh facilities. in a mosque surrounded by many trees, gutters are components that must be taken care of. the falling leaves that accumulate in the gutter will make the drainage channel become clogged and the rainwater cannot flow into the reservoir. conclusions the potential support of rainwater as an alternative source of wudlu water in indonesia has been discussed above. the conclusion is that rainwater can be used as an alternative source of clean water in the future to supply various water needs including wudlu water needs. harvesting of rainwater in the mosques for wudlu water use in indonesia is still rare. therefore, it is time to introduce rainwater harvesting system in order to overcome the clean water crisis, especially for wudlu, in the future. rainwater harvesting technology is not a difficult and expensive technology. there is no need for an expert in constructing a rainwater harvesting facility. the important thing to remember from a rainwater harvesting application is the maintenance of the rainwater harvesting facility itself. maintenance must be done periodically to maintain the smooth operation of rwh facilities acknowledgements the author wishes to convey his infinite gratitude to the department of civil engineering, lampung university for his support of this research. the authors also wish to express their gratitude to the students who assisted with the completion of this research. references [1] abdulla, f. a., and al-shareef, a. w. 2009. roof rainwater harvesting systems for household water supply in jordan. desalination, 243:195–207. [2] fewkes a. 1999. the use of rainwater for wc flushing: the field testing of a collection system. building and environment, 34(6), 765–772. [3] handia, l., tembo, j. m., and mwiindwa, c. 2003. potential of rainwater harvesting in urban zambia. physics and chemistry of the earth, vol. 28:893–896. [4] kahinda jm, taigbenu ae, and boroto rj. 2010. domestic rainwater harvesting as an adaptation measure to climate change in south africa. physics and chemistry of the earth, vol. 32(15-18), pp. 1050–1057. [5] khastagir a, and jayasuriya n. 2010. optimal sizing of rain water tanks for domestic water conservation. journal of hydrology, 381(3–4), pp. 181–188. [6] map of the world, 2017. top ten countries with the largest renewable water supply. website: https://www.mapsofworld.com/world-top-ten/world-top-ten-fresh-water-supplymap.html. [7] poedjiastoeti h, and syahputra b. 2006. determination of the maximum peak hour and daily maximums on the domestic water use pattern in kalasan, sleman, yogyakarta. proceeding of lecturer research, research institute of sultan agung university, yogyakarta, indonesia. [8] susilo ge, yamamoto k. and imai t. 2011. the identification of rainwater harvesting potency civil and environmental science journal vol. i, no. 02, pp. 062-069, 2018 69 in supporting freshwater availability under the effect of el nino. proceeding iwa – aspire international conference, october 2011, tokyo – japan. [9] susilo ge. 2015. experience in rainwater harvesting application at household scale in bandar lampung, indonesia. proceeding of the 1st young scientist international conference of water resources development and environmental protection, malang, indonesia, 5-7 june 2015 [10] susilo ge, efendi r, desmawati e, and nalaralagi a. 2017. promoting rainwater harvesting as an alternative of freshwater source for public sanitation. journal of asian institute of low carbon design (2017), pp. 201–207. [11] widyanti, e. 2015. curah hujan indonesia, pengembangan media pembelajaran geografi. website: http://eka-widiyanti.blogspot.co.id/2015/04/curah-hujan-indonesia.html. 25 january 2018 (20.30 wib). open access proceedings journal of physics: conference series civil and environmental science journal vol. i, no. 02, pp. 052 061, 2018 52 urban growth modelling of malang city using artificial neural network based on multi-temporal remote sensing agung bayu nugroho1, abdul wahid hasyim2, fadly usman2 1 master degree of civil engineering department interest of urban and regional planning, universitas brawijaya, malang, 65145, indonesia 2 urban and regional planning engineering department, universitas brawijaya, malang, 65145, indonesia xceedrift@gmail.com received 23-08-2018; revised 03-09-2018; accepted 20-09-2018 abstract. in this study, the prediction of urban growth was simulated by artificial neural network (ann) model using molusce, plugin of qgis. objectives of this study is to illustrate the urban growth in malang city over time span of 24 years and also to predict the future of urban growth using ann model for the year 2027. land cover maps were extracted for 2003, 2009 and 2015 via remote sensing images from landsat etm+ and oli, respectively. the overall classification accuracy and kappa coefficient for all classified maps were over 85% and 0.76, respectively. according to the simulation result, 1049.58 ha of vegetation and 241.29 ha of bare land in 2015 would experience a transition to built-up areas in 2027. then, the built-up areas would experience an increase by 11.79% from 2015 to 2027. in 2027, the built up areas would covered the city by 73.21% of the city area. there was a trend in increasing of built-up areas during the period 2003 to 2027. overall, the result shows that urban growth models by using ann model can be a considerable option for future changes according to past and current factors. keywords: urban growth, artificial neural network, land cover, built-up areas, molusce. 1. introduction according to the un’s data, 68% of world's population is estimated to be residing in urban areas in the year 2050 [1]. furthermore, it has been predicted that by the middle of the 21 century, 7 out of 10 world’s population would live in urban areas [2]. recently, urban growth has been a main issued in land cover changes that have consequences in degradation of vegetation and environment [3]. urban growth can be monitoring by observing built-up areas in a certain period of time [4]. observation of land cover changes over time is important as a consideration in urban development planning. [5]. remote sensing has the ability to get data related to built-up areas or non-built-up areas in an area which is extracted from satellite image data [6]. in this study, change detection would be performed to identify land cover changes in malang city from 2003 through 2015. predicting process of land cover map in the year 2027 also would be performed by artificial neural network (ann) model using molusce, plugin from qgis. then, by comparing two built up areas from 2003 through 2015 and 2027 as the result of the simulation, the urban growth of malang city can be examined. civil and environmental science journal vol. i, no. 02, pp. 052 061, 2018 53 2. material and methods 2.1. study area malang city is located at east java in indonesia. administratively, the location is surrounded by malang regency. malang city consist of five districts that including lowokwaru, kedungkandang, klojen, sukun and blimbing. this city is the second largest city in east java. this city is also known as the city of education due to many various educational institutions that found in this city. this situation makes this city as a destination for migrants from other regions. furthermore, the development trend of this city which also leads to industrial and tourism city [7]. figure 1. study area in malang city 2.2. data collection and preprocessing this study used satellite image data that were obtained from landsat 7 etm+ and landsat 8 oli. according to usgs, these data were included in the “tier 1” category where appropriate for time-series analysis [8]. to achieve the objectives of this study, satellite image data in 2003, 2009 and 2015 were collected from the usgs website. aster dem was also obtained to get elevation data for slope calculation. due to scan lines error, the image of the year 2009 (month of july) was corrected by filling gaps with images from another month (month of august). 2.3. classification and accuracy assessment supervised classification was performed by using maximum likelihood classification technique to identify land cover classes. training samples has been selected by observing false-colour tone map. four land cover categories including bare land, built-up areas, vegetation and water bodies were used in this study. the validation of the land cover maps were calculated by measuring accuracy and kappa coefficient. google earth has a main role in calculating of accuracy assessment. google earth can be considered as a powerful source that has appropriate accuracy and inexpensive [9]. by using level confidence 95% and accuracy 90%, as sampling parameters, there were obtained 159 samples. a random set of point was generated in the land cover maps for 2003, 2009 and 2015. google earth was used to identifying each point by synchronize it with erdas 2014. 2.4. change detection in land cover categories change detection was carried out to determine land cover changes from 2003 to 2009 and 2009 to 2015. that method was performed by using molusce plugin from qgis. the result of this processing generated raster maps with 16 transition of land cover classes that displayed in post-classification matrix table. in the calculation process, those maps later were converted to vector data. the same method was also used to identify the change detection from 2015 to 2027. civil and environmental science journal vol. i, no. 02, pp. 052 061, 2018 54 2.5. land cover modelling and validation by using molusce, plugin of qgis, if the year of 2015 was targeted to be predicted in which to validate the ann model parameters, land cover maps for year 2003 and 2009 were used. figure 2 shows ann diagram model that was used for simulation in this study [10]. spatial variables maps including distance from main road, distance from river, distance from existing built-up areas in 2009 and slope were also used in the same process. the validation process was performed to determine the association between 2015's predicted map and 2015's real (actual) map. when the year 2027 was targeted, land cover maps for year 2003 and 2015 were used. in this process, spatial variables to be used were the same as in the validation process except in the distance from existing built up areas in 2009 which replaced with distance from existing built-up areas in 2015. the validation was performed by determining accuracy and kappa coefficient. once the ann model parameters were obtained, those were used to predict 2027's land cover map. simulation process were done separately for each district in malang city due to gain more simulation result related to urban growth and then recombined them again after the simulation has been done. urban growth can be analysed by calculating the amount of built-up areas in the city [4]. figure 2. diagram of artificial neural network model four spatial variables that were used in this study (table 1) were collected after comparing spatial variables from many literatures [11,12,13,14,15,16,17]. distance from main road and distance from existing built up areas for both year 2009 and 2015 were processed by using euclidian distance tool in arcgis. distance from river was prepared by using boolean approach through processing via arcgis and idrisi selva. slope was processed by using fuzzy set membership function in idrisi selva and arcgis. distance from main road and slope were defined as static factor. distance from river was also used the same definition due to the existence that almost unchanged in recent years. distance from existing built-up areas was defined as dynamic factor, which used different data for simulation that targeted for 2015 (validation of ann model) and 2027. table 1. spatial variables variable spatial description distance from existing built up areas areas that close to existing built-up areas are more appropriate for urban development than areas far from built-up areas distance from main road areas that close to main road are more appropriate for built-up areas than areas far from main road distance from river areas within 50 m of river are considered inappropriate for built-up areas slope areas that close to zero percent of slope are more appropriate for builtup areas and areas with slope greater than 15% are inappropriate civil and environmental science journal vol. i, no. 02, pp. 052 061, 2018 55 3. result and discussion 3.1. land cover classification, accuracy assessment and change detection overall accuracy of land cover maps for 2003 (figure 3), 2009 (figure 4) and 2015 (figure 5) were 86%, 92%, and 93%, respectively (table 3). three of them have kappa coefficient above 0.76 that shows good values [18]. according to table 2 and 3, there were increases by 9.41% and 10.41, during the period 2003 to 2009 and from 2009 to 2015, respectively. in another category, vegetation in malang city decreased by 8.12% from 2003 to 2009 and 6.91% from 2009 to 2015. bare land also decreased by 1.26% from 2003 to 2009 and 3.37% from 2009 to 2015. another land cover category such as water bodies only get a small percentage decreased compared to vegetation, built-up areas and bare land. overall, it can be explained that when there was an increase in built-up areas there was a tendency to decrease over bare land and vegetation for the period 2003 to 2009 and 2009 to 2015. table 2. land cover statistic of malang city, 2003-2009 year 2003 2009 changes rate land cover category ha % ha % ha % bare land 778.10 7.01 637.73 5.75 -140.37 -1.26 built-up areas 4616.31 41.60 5660.16 51.00 +1043.85 +9.41 vegetation 5640.65 50.83 4739.44 42.71 -901.21 -8.12 water bodies 62.43 0.56 60.16 0.54 -2.27 -0.02 table 3. land cover statistic of malang city, 2009-2015 year 2009 2015 changes rate land cover category ha % ha % ha % bare land 637.73 5.75 263.94 2.38 -373.79 -3.37 built-up areas 5660.17 51.00 6815.15 61.41 1154.98 +10.41 vegetation 4739.44 42.71 3972.13 35.79 -767.31 -6.91 water bodies 60.16 0.54 46.29 0.42 -13.87 -0.13 table 4. post-classification matrix of land cover transition in malang city from 2003 to 2009 (in hectare) 2009 2003 land cover category bare land built-up areas vegetation water bodies bare land 134.42 449.07 192.99 1.62 built-up areas 80.80 4333.21 195.32 6.98 vegetation 418.64 867.80 4306.44 47.78 water bodies 3.87 10.09 44.70 3.78 table 5. post-classification matrix of land cover transition in malang city from 2009 to 2015 (in hectare) 2015 2009 land cover category bare land built-up areas vegetation water bodies bare land 45.40 377.26 214.26 0.81 built-up areas 94.37 5315.96 227.60 22.24 vegetation 122.72 1102.28 3494.27 20.16 water bodies 1.44 19.65 35.99 3.08 civil and environmental science journal vol. i, no. 02, pp. 052 061, 2018 56 figure 3. actual land cover maps for the year 2003. figure 4. actual land cover maps for the year 2009 figure 5. actual land cover maps for the year 2015 figure 6. simulated land cover map for the year 2015 according to table 4, there were 867.8 ha, 449.07 ha, and 10.09 ha of land cover transition from vegetation to built-up area, bare land to built-up area and water bodies to built-up area for the period 2003 to 2009, respectively. there were many increasing in the same categories by 1102.28 ha, 377.26 civil and environmental science journal vol. i, no. 02, pp. 052 061, 2018 57 ha and 19.65 ha for the period 2009 to 2015, respectively. therefore, it can be explained that the vegetation provided the greatest contribution in increasing of built-up areas in malang city for the period 2003 to 2009 and from 2009 to 2015. 3.2. land cover modelling and validation the validation process was performed for each district by measuring kappa coefficient. ann model parameters that were used for each district simulation were shown in table 6. the accuracy for each district in malang city was above 86% while the kappa coefficient value for each district was varies. lowokwaru, blimbing, and kedungkandang districts have kappa coefficient value above 0.6 that considered as substantial category. another two districts, klojen and sukun, have kappa coefficient 0.44 and 0.56 that still considered as moderate category. since, kappa coefficient that has a value below 0.4 considered poor [18], overall ann model parameters for each district can still be used to predict the future land cover. figure 6 shows that simulated land cover map of 2015 have been joined from each district as the result of simulation. after validating the model, the land cover map of 2027 was predicted by using 2003 and 2015 land cover map with several spatial variables (distance from main road, distance from river, slope and distance from existing built up areas in 2015). figure 7 shows the predicted land cover for the year 2027. table 6. ann model parameters for land cover prediction in 2027 district n total sample hidden layer learning rate momentum max iteration lowokwaru 1 2569 32 0.01 0.05 1000 blimbing 2 2202 53 0.01 0.05 1000 klojen 1 1052 32 0.01 0.1 1000 sukun 1 2450 32 0.01 0.05 2000 kedungkandang 1 4560 32 0.01 0.1 2000 figure 7. simulated land cover map for the year 2027 figure 8. urban growth in malang city from 2003 to 2027 civil and environmental science journal vol. i, no. 02, pp. 052 061, 2018 58 table 7. land cover statistic of malang city, 2015-2027 year 2015 2027 change rate land cover category ha % ha % ha % bare land 263.94 2.38 18.69 0.17 -245.25 -2.21 built-up areas 6815.15 61.41 8124.09 73.21 1308.95 +11.79 vegetation 3972.13 35.79 2928.40 26.39 -1043.73 -9.41 water bodies 46.29 0.42 26.32 0.24 -19.97 -0.18 table 8. post-classification matrix of land cover transition in malang city from 2015 to 2027 (in hectare) 2027 2015 land cover category bare land built-up areas vegetation water bodies bare land 18.33 241.29 4.32 0.00 built-up areas 0.00 6815.06 0.09 0.00 vegetation 0.36 1049.58 2922.19 0.00 water bodies 0.00 18.17 1.80 26.32 according to table 7, built-up areas increased by 11.79% representing 1308.95 ha in the year 2027. another three of land cover categories, bare land, vegetation and water bodies decreased by 2.21%, 9.41% and 0.18%, representing 248.04 ha, 1021.ha and 21.95 ha, respectively. based on table 7, there was an increase in built-up areas from 6815.15 ha to 8124.09 ha during the period 2015 to 2027. there were 1049.58 ha of vegetation that have transformed into built-up areas from 2015 to 2027 (table 8). there was a degradation of continuous vegetation loss with increasing rates 8.12%, 6.91%, 9.41%, between 2003-2009, 2009-2015 and 2015-2027, respectively. according to table 4, 5 and 8, a lot of vegetation experiences a transition into built-up areas rather than into other land cover categories such as bare land and water bodies. figure 9. built-up areas change in each district of malang city from 2003 to 2027 (in hectare) civil and environmental science journal vol. i, no. 02, pp. 052 061, 2018 59 figure 10. percentage of built-up areas in each district of malang city from 2003 to 2027 figure 11. percentage of built-up areas in malang city from 2003 to 2027 according to figure 8, figure 9 and figure 10, there was a trend of increasing built-up areas in each district in malang city from 2003 to 2027. kedungkandang was a district with the biggest built-up areas despite the percentage was the lowest from 2003 to 2027. on the contrary, klojen was a district with biggest percentage of built-up areas though the size was the lowest. blimbing was the second largest district in the largest percentage of built areas in the year 2027. based on the simulation result, blimbing and klojen almost covered their areas by built-up areas, representing 95.62% and 98.41% of their total areas in 2027, respectively. the district that has largest vegetation areas was kedungkandang. the district has 2038.90 ha of vegetation areas. figure 11 shows that the built-up areas would covered 73.21% of malang city areas in the year 2027 after increasing 31.61% from the year 2003. 4. conclusions civil and environmental science journal vol. i, no. 02, pp. 052 061, 2018 60 this study shows that simulation approaches by using ann model can be a considerable option to predict land cover future changes and the direction of spatial distribution in malang city. three landsat data that were obtained in 2003, 2009 and 2015 were classified by using supervised classification. land cover change detection was determined by using post-classification matrix. in general, based on the data on land cover changes, it was explained that vegetation contributed greatly in increasing of built up areas in malang city from 2003 to 2027. there was a trend of increasing built-up areas during the period 2003 to 2027. the predicted land cover map in 2027 by ann model indicated that the built up areas would continue increasing up to 73.21% of the city areas. however, if the urban growth data was compared in the 12 year intervals, in the period 2003 to 2015 and 2015 to 2027, the built-up areas would experience an increase by 19.81% and 11.79%, respectively. there was a decrease in the percentage of built-up areas by 8.02% in the last period compared with the first period. blimbing and klojen were two districts that would almost covered their areas with built-up areas in 2027 based on simulation result. kedungkandang would have the lowest of built-up areas by 48.75% in 2027 based on the simulation result. overall, the results of this study can be used as an option to be considered by city planners, government and all decision makers that involved in the decision making process for preparation of city spatial planning and environmental sustainability. references [1] un, 2018. world urbanization prospects : the 2018 revision. https://esa.un.org/unpd/wup/publications/files/wup2018-keyfacts.pdf [2] un-habitat. 2013. state of world's cities 2012/2013. prosperity of cities. (earthscan : london). [3] xian, g. z. 2016. remote sensing application for the urban environment (crc press: new york) [4] bhatta, b. 2012 urban growth analysis and remote sensing : case of kolkata, india 1980-2010 (springer : new york) [5] lavender s. and lavender a. 2016. practical handbook of remote sensing (crc press : new york) [6] giri c.p.,2012. remote sensing of land use and land cover : principles and application (crc : press : new york) [7] malik, n. 2016. dinamika pasar tenaga kerja indonesia (umm press : malang) [8] usgs. 2016. landsat collection 2016. https://landsat.usgs.gov/sites/default/files/documents/ special_iss3_2016.pdf [9] tilahun a. and teferie b. 2016. accuracy assessment of land use land cover classification using google earth. american journal of environmental protection 2015; 4(4): p 193-198 [10] livingstone d.j. 2008. artificial neural network method and application (humana press) [11] megahed y., cabral p., silva j., caetano m. 2015. land cover mapping analysis and urban growth modelling using remote sensing techniques in greater cairo region—egypt. sprs int. j. geo-inf. 2015, 4, p 1750-1769 [12] araya h. y. and cabral p.. 2010. analysis and modeling of urban land cover change in setúbal and sesimbra, portugal. remote sens. 2010, 2, p 1549-1563 [13] vaz e. and arsanjani j.j.. 2015. predicting urban growth of the greater toronto area coupling a markov cellular automata with document meta-analysis. journal of environmental informatics 2015 [14] ozturk d. 2015. urban growth simulation of atakum (samsun, turkey) using cellular automata-markov chain and multi-layer perceptron-markov chain models. remote sens. 2015, 7, p.5918-5950 [15] triantakonstantis d. and stathakis d. 2015. urban growth prediction in athens, greece, using artificial neural networks. international journal of architectural and environmental engineering vol:9, no:3, 2015 [16] moghaddam k.h. and samadzadegan f. 2009. urban simulation using neural networks and civil and environmental science journal vol. i, no. 02, pp. 052 061, 2018 61 cellular automata for land use planning. real corp 2009: cities 3.0 – smart, sustainable, integrative [17] rahman m.t.u., tabassum f., rasheduzzaman m., saba h., sarkar k.. derfous j., uddin s.z., islam a.z.m.z. 2017. temporal dynamics of land use/land cover change and its prediction using ca-ann model for southwestern coastal bangladesh. environ monit assess (2017) 189:565 [18] hay s.i., randolph s.e., rogers d.j. 2000. remote sensing and geographical information systems in epidemiology (academic press: new york) open access proceedings journal of physics: conference series civil and environmental science journal vol. 05, no. 02, pp. 225-234, 2022 225 priority mapping for handling environmental road using gis in gerung district, west lombok regency hafiz hamdani1, heni pujiastuti1 1 civil engineering study program and faculty of engineering, muhammadiyah mataram university, mataram, 83115, indonesia hafiz.hamdani@ummat.ac.id, hpujiastuti@ummat.ac.id received 28-08-2022; accepted 25-10-2022 abstract. improving road access is very important to support human activities. one is improving the quality of environmental roads in gerung district, west lombok regency. however, priority handling is needed to make it with the fund availability that cannot cover the entire segment simultaneously. a surface distress index (sdi) survey is used in this paper to determine priority handling. an sdi survey is a method to classify road damage based on the road surface condition. this paper intends to determine the number of environmental roads in gerung district, to know the priority of handling with an sdi survey, and create a handling priority map using gis. the results found that the number of environmental roads in gerung district was 987 sections spread over 11 villages and three sub-districts. the classification of road conditions determines the handling priority of environmental roads: good, medium, lightly damaged, and heavily damaged. the number of routes based on this classification is 568 segments for good conditions, 131 segments for medium needs, 200 parts for lightly damaged, and 88 sections for heavily damaged conditions. in the map, each road segment is assigned with color identity according to its requirements and handling priorities using qgis. keywords: environmental road, handling priority, sdi survey, qgis. 1. introduction road infrastructure is often linked with the development of a region. the link opens underdeveloped areas and triggers growth in developing areas [1]. the road is very commonly an infrastructure that supports people's daily activities and mobility. it connects one place to another, one area to another, and even one island to another. high and repeated traffic volume will decrease road quality. it impacts traffic flow safety, comfort, and smoothness [2]. it is necessary to improve road quality by improving the road surface layer and/or the road base layer. the increase in population will make the expansion of housing and settlements. west lombok regency is one of the areas experiencing significant population growth. the development of land will also create new road access. the essential new access road that will form is the environmental road. it’s a road with low average speed and short distance trips. decreasing road quality will undoubtedly reduce the comfort and safety of road users. with limited funds to handle the environmental road quality improvement, it should have a valid handling priority. mailto:hafiz.hamdani@ummat.ac.id mailto:henipujiastuti@gmail.com civil and environmental science journal vol. 05, no. 02, pp. 225-234, 2022 226 assessing the road handling priority needs various methods that can use. a surface distress index (sdi) survey was used in this paper to decide on priority handling. sdi survey is a method to classify road damage based on the road surface condition. this method requires the surveyor to understand the concept of road damage based on experience and have good instincts in determining the damage in the field. sdi classified road damage by conducting actual surveys in the area. it’s elementary both in reviewing and processing data. furthermore, the priority of handling can be determined based on the classification of road damage resulting from field data processing. a good presentation of data is required to make it easier to read and understand for people related to the field. the presentation of data is mostly done with graphs, tabulated s, and bar charts. not a few also present data in the form of maps. a map is a good alternative for presenting data. various software can be used to create a map, and qgis is one of them. qgis is a commonly used geospatial information system (gis) based software. this software is relatively easy to use, especially for beginners though. in addition, this software is freely accessible to the public, or it is not paid. it has been widely used in various scientific fields. for example, in the health sector, qgis is used for mapping the distribution of various diseases; telecommunications field qgis is used for inventory of telecommunications networks and many more. the revenue source of a regency is from taxes and regional levies. improving the quality of the whole road at one time requires very large funds. therefore, it is necessary to improve the quality of roads gradually. therefore, this research aims to create a handling priority map using gis. handling priority map. priority maps for road handling will make it easier for users to determine which roads will be repaired based on the level of damage. therefore, improving the road quality will be more efficient and on target. in addition, this map can be used as a data bank to find out how many roads need to be handled. 2. methods this research was held on february 01 – july 31 2022, with gerung district in west lombok regency as the study case location. gerung is one of a district in west lombok regency, which consists of 11 villages and three sub-districts with an area of 62.29 km2. it’s also the capital of west lombok regency. this makes gerung an attraction for location studies, where the capital district is still dominated by rural areas, and it’s still under development status. 2.1. field data collection preliminary research is needed on road surface conditions by conducting a visual survey by viewing and analyzing the road damage that occurs as a reference to rehabilitation and maintenance activities by the level and damage type [3]. this paper's field data were taken on all environmental roads in gerung district. the tools used to support the implementation of activities include gps, por meter, roller meter, sdi survey form and stationery. then the data obtained include: tracking data, the condition of the existing road surface, and vertical alignment for every 50m length. 2.2. data processing processing data was held in 2 stages. the first step is determining the classification of environmental road segments using the sdi method. and then, based on the result of the first step, a map was made using qgis software. 2.2.1 surface distress index (sdi) method directorate general of highways developed methods to determine the maintenance type. the methods are based on visual observations. surface distress index (sdi) is one of the methods by visual check on the crack’s total area, the width average of the cracks, the number of holes, and the depth of vehicle ruts [4]. furthermore, based on the inspection, it will be processed using the assessment standards that have been made by the directorate general of highways in figure 1, civil and environmental science journal vol. 05, no. 02, pp. 225-234, 2022 227 rcs cracks total area average cracks widths sdi surface distress index potholes number average depth of vehicle ruts figure 1. calculation of the sdi method sdi method has several types of damage, namely [5]: a. cracks cracks are a symptom of pavement surface damage. this crack will allow water to enter the layer below it and cause extensive/severe damage. based on the shape of the cracks are divided into meanders, lines, blocks, crocodile skin and parabolas. b. potholes this damage is shaped like a bowl that can accommodate and absorb water on the road shoulder. potholes occur on the surface with poor drainage systems. c. rutting this damage occurred in the trajectory of the wheels and is caused by excessive vehicle loads, causing vehicle ruts. standard road conditions in the surface distress index (sdi) method can be seen in table 1 below, table 1. road conditions based on sdi value no. road conditions sdi value 1 good <50 2 medium 50-100 3 lightly damage 100-150 4 heavily damage >150 in getting the sdi value in surveying road conditions, four supporting elements are used: % of the crack area, average crack width, potholes number/km, and rut depth average [4], [6-7]. the calculation shown in tables 2 to 5 is as follows: table 2. valuation of crack area no. crack are category sdia value 1 none 2 < 10% 5 3 10% – 30% 20 4 > 30% 40 civil and environmental science journal vol. 05, no. 02, pp. 225-234, 2022 228 table 3. valuation of crack width no. crack width category sdib value 1 al u e 1 none 2 fine < 1 mm 3 medium 1 mm – 3 mm 4 width >3 mm sdia value *2 table 4. valuation of hole number no. hole number category sdic value 1 none 2 < 10/km sdib value + 15 3 10/km – 50/km sdib value + 75 4 >50/km sdib value + 225 table 5. valuation of rut depth no. rut depth category sdid value 1 none 2 <1 cm depth sdic value + 5 x 0,5 3 1 cm – 3 cm depth sdic value + 5 x 2 4 >3 cm depth sdic value + 5 x 4 2.2.2 qgis software today's development of information system software is no longer limited to tabular data processing, where data is stored in database tables managed by dbms (database management system) software. still, it has been developed for spatial or spatial data processing. [8]. gis (geographic information system) is a system that presents images, analyses, and displays data based on the condition of the earth. gis technology is very useful for various groups of people to explain events, plan strategies, and predict what will happen. [9]. gis has several capabilities, including: [10-11]: a. data location mapping the actual location data on the earth’s surface will be mapped into several layers, each representing a collection of objects that have similarities. b. quantity mapping gis can map quantity, something to do with quantity, such as where is the most or which is the least. this is will make it easier to observe statistical data than ordinary databases. c. density mapping density maps can change the form of concentration into units that are easier to understand and uniform. for example, dividing the area into 10 km2 wide squares using different colors to describe each density class will make it easier to read. density mapping is very useful for large amounts of data, such as censuses or regional statistical data. d. change mapping by including time variables, gis can be created for historical maps. this history can be used to predict future conditions and can also be used for policy evaluation. mapping the storm's path can be used to predict where the storm will go. e. mapping what's inside and outside civil and environmental science journal vol. 05, no. 02, pp. 225-234, 2022 229 an area gis is also used to monitor what is happening and what decisions will be made by mapping what is in and outside the area. 3. result and discussion 3.1 research location this research was located in gerung district in west lombok regency. this district contains 11 villages and three sub-district. gerung is the capital of west lombok regency, with 62,29 km2 of area. and research location is shown in figure 2 as follows, figure 2. research location 3.2 sdi value after obtaining survey and measurement data, data processing is held using the sdi method. the average value for the sdi value of environmental roads in the gerung district is 65.01. based on the classification of road conditions on sdi values ranging from 50-100, overall environmental roads in gerung district are in medium condition. the average sdi value for each village and sub-district is in table 6 as follows: table 6. environmental roads condition based on average sdi value no. area name sdi value average condition 1 mesanggok village 89.96 medium 2 suka makmur village 63.69 medium 3 gapuk village 48.38 good 4 taman ayu village 60.00 medium 5 kebon ayu village 40.98 good 6 banyu urip village 109.03 lightly damage 7 tempos village 77.92 medium 8 giri tembesi village 99.83 medium 9 babussalam village 77.29 medium lombok islands map gerung district civil and environmental science journal vol. 05, no. 02, pp. 225-234, 2022 230 no. area name sdi value average condition 10 beleka village 20.19 good 11 dasan tapen village 26.48 good 12 gerung selatan sub-district 59.14 medium 13 gerung utara sub-district 69.25 medium 14 dasan geres sub-district 47.66 good table 6 shows that from 14 review locations, there were 5 locations known as good conditions, 8 locations at medium conditions, and 1 location at lightly damaged conditions. 3.3 mapping with qgis the components displayed on the map must be informative and clear, following map-making needs. in this paper, several main components are shown on the priority map for handling environmental roads as follows: 1. region boundaries, 2. environmental road network, 3. primary road network, 4. river network, 5. contour line, 6. toponym, 7. coloring the environmental road network according to field conditions. the color gradation gives the environmental road network colors according to actual conditions. yellow color for the good condition, orange for medium conditions; red for lightly damaged conditions; and maroon for heavily damaged condition. in this case, giving the color of the road network also pays attention to the colors for other components so that they can be seen clearly by making the priority map for handling this environmental road network. furthermore, the environmental road network map can be seen in figures 3 to 6 as follows, figure 3. priority map for handling environmental roads in gerung district civil and environmental science journal vol. 05, no. 02, pp. 225-234, 2022 231 figure 4. priority map for handling environmental roads in banyu urip village with average lightly damaged conditions figure 5. priority map for handling environmental roads in mesanggok village with average medium conditions civil and environmental science journal vol. 05, no. 02, pp. 225-234, 2022 232 figure 6. priority map for handling environmental roads in beleka village with average good conditions based on figures 3 to 6, it can be seen the condition of each road segment by referring to the color identity that has been given. the priority for handling environmental roads is roads with heavily damaged, lightly damaged, and medium. from the 987 identified roads, there were 568 segments with good condition, 131 segments in medium condition, 200 with light damage, and 88 with heavy damage. based on the data above, the average condition of the gerung district environmental road is medium. it has 88 heavily damaged and 200 lightly damaged segments to be a priority of handling (figure 3). figure 4 shows that banyu urip village has an average lightly damaged condition of the environmental road. banyu urip has 108 total segments, and it contains 39 segments in good condition, 20 segments for medium conditions, 29 for lightly damaged, and 20 for heavily damaged conditions. figure 5 shows that mesanggok village has an average medium condition of environmental roads. mesanggok has 63 total road segments, and it contains 35 segments in good conditions, 11 for medium conditions, 5 for lightly damaged, and 12 for heavily damaged conditions. and figure 6 shows that beleka village has an average good condition of the environmental road. beleka has 77 total road segments; it contains 67 segments of good condition, 10 segments for lightly damaged, and one for heavily damaged condition. from the previously described data, each road segment's condition is already known. to apply the priority of handling environmental roads, it can be done with two alternatives by adopting the presenting existing data, as follows: 1. priority handling can be applied based on the condition level. in this case, priority handling will apply from the worst one. the worst condition in this paper is known as heavy damage condition. in other words, priority handling applied from the worst condition from all locations in gerung district; 2. priority handling can be applied based on the average condition of each sub-district and village in the gerung district. according to table 6, sdi value of each sub-district and village can be arranged from the highest to the lowest one to determine the priority of handling. sdi value is linear to the road surface condition. because the higher sdi value is, the worst condition it's civil and environmental science journal vol. 05, no. 02, pp. 225-234, 2022 233 going to be. the lowest sdi value is, then the road surface condition will be better. in another word, priority handling is applied from the average condition of each sub-district and village in the gerung district. determination of color gradations in gis is very useful to providing identity on the area, distribution area of a condition, or condition of a certain area and point. in f. juniardi's (2014) research entitled development of a geographical information system for regency transportation infrastructure kapuas hulu based on the web, a map is generated for all types of public transportation available in kapuas hulu district. each type of transportation mode is given as a symbol and placed according to the point location. the map also gave different colors to the identity of each village and sub-district. in this paper, the use of color gradation determination is used to show the level of environmental road surface damage in each village and sub-district. 4. conclusions sdi method is quite easy to apply to determine the actual condition of road sections. it contains parameters that are easy to understand and used as a reference during field inspections. for environmental roads in gerung district, there are 987 environmental roads identified with the following conditions: 568 segments with good conditions 131 segments with medium condition, 200 segments with lightly damaged, and 88 segments with heavily damaged. furthermore, quantum gis makes it very easy to create priority maps for environmental road management. besides being free, this application also does not require high device specifications to run it. facilitating the map reading, each road segment is assigned a color identity according to the conditions and priority of handling. the color identities are yellow for good condition, orange for medium condition, red for lightly damaged condition, and maroon for heavily damaged condition. acknowledgements the authors would like to thank those who helped complete this research, especially the surveyors and the west lombok regional development agency, who have shared secondary data as support for making maps. the authors also thank the journal editors who have participated in directing this paper to be better. references [1] syafii, m. suprapto., e. anggara d., “evaluation of road network based on geographic information system, case study: local roads in karanganyar regency,” proc. of the 19th international symposium of fstpt islamic university of indonesia, ch. 9,october, pp. 1665– 1673, 2016. [2] ichsan, evaluation study of the level damage to the road surface to determine the type of handling with a rating system according to directorate general of highways (case study: bireuen takengon road). thesis. syiah kuala university, aceh. 2014. [3] r. yahya, m. yusri b.a., a. suraji, a. halim, “analysis of road damage using the pavement condition index (pci) and surface distress index (sdi),” proc. conference on innovation and software of science and technology (ciastech), october, pp. 355–361, 2019. [4] g. aptarila, f. lubis, a. saleh, “analysis of road damage using sdi method of taluk kuantan west sumatra province boundary,” siklus journal of lancang kuning university, vol. 006, no. 02, pp. 195–203, october. 2020. [5] ministry of public works, construction and building manual about road maintenance procedures. 2011. [6] e. minarti, observation of road damage from the value of the surface distress index (sdi) and the value of the international roughness index (iri) (case study: the national road section calang-teunom km. 150 to km. 157. thesis. syiah kuala university, aceh. 2014. civil and environmental science journal vol. 05, no. 02, pp. 225-234, 2022 234 [7] u. thoatin, a. setyawan, m. suprapto, “the use of internal roughness index (iri), surface distress index (sdi) and pavement condition index (pci) methods to assess road conditions in wonogiri regency,” proc. semnastek, november, pp. 001–009, 2016. [8] f. juniardi, h. azwansyah, “road management information system in ketapang city,” elkha journal of tanjungpura university, vol. 005, no. 02, pp. 012–017, october. 2013. [9] s.a. adelino, w. hartono, a.p. saido, “mapping for environmental road maintenance in surakarta city using a geographic information system,” matriks teknik sipil e-journal of sebelas maret university, vol. 003, no. 01, pp. 017–021, march. 2015. [10] f. juniardi, h. azwansyah, “development of a web-based geographic information system for the transportation infrastructure of kapuas hulu regency,” elkha journal of tanjungpura university, vol. 006, no. 01, pp. 006–011, march. 2014. [11] f. juniardi, h. azwansyah, “development of a geographic information system for village road management in kapuas hulu district,” elkha journal of tanjungpura university, vol. 007, no. 01, pp. 036–041, march. 2015. open access proceedings journal of physics: conference series civil and environmental science journal vol. 5, no. 1, pp. 064-077, 2022 64 mathematical model distribution of some water quality parameters in the reservoir r w sayekti1,*, moh. sholichin1, m. bisri1, heri suprijanto1, nadya a. nathania1 1water resources engineering department, universitas brawijaya, malang, 65145, indonesia *rini_ws@ub.ac.id received 13-04-2022; accepted 29-04-2022 abstract. sutami reservoir is one of the largest reservoirs in east java province and is very useful in the life of people in malang. however, the water quality of sutami reservoir currently degrades due to waste. this study aims to determine water quality using the pollution index method and mathematical modeling. polynomial regression is the most suitable mathematical model. it was obtained by statistical testing and adjusted based on population index data. sutami reservoir is classified as a reservoir with a eutrophic trophic status. the load capacity in eutrophic conditions at the monitoring station revealed that the levels exceeded the maximum pollution load limit. the relevant authorities need to take action to overcome the waste problems which contribute to the degradation of water quality in sutami reservoir. keywords: water quality, pollution index, mathematical model, regression 1. introduction the water quality (wq) of watershed systems is affected by high anthropogenic pressures, including domestic wastewater discharges and industrial and agricultural activities [1]. the deterioration of the water environment has led to the reduction of available water resources and damaged a healthy aquatic ecosystem. the water environment system is very complicated and depends on weather, water body hydraulic characteristics, pollutant discharge, and the aquatic biological impact. therefore, it is necessary to predict the water quality evolution process [2]. the main purpose of the water quality monitoring system is to generate sufficient and timely information to establish water quality management plans and make environmental policies [3]. sutami reservoir or also known as karangkates reservoir, is one of the largest reservoirs in east java, built-in 1964-1973. this reservoir is located in karangkates village, sumberpucung, malang regency. it has three main benefits: the first as a flood control reservoir for the 50-year return period, the second as a provider of irrigation water sources in the downstream area with a discharge of 24 m3/second in the dry season to serve 34,000 ha. the last one is a hydropower plant with 488 million kwh/year [4]. in addition, this reservoir is used as a tourist attraction and freshwater fisheries. the sutami reservoir gets its water source from the brantas river. the current condition of the brantas river has decreased the quantity and quality of its water. in the upstream area of the brantas river, there is environmental damage and the conversion of protected forest functions into agricultural, civil and environmental science journal vol. 5, no. 1, pp. 064-077, 2022 65 industrial, and other building areas. it causes the river water quality to decrease due to pesticides and chemical fertilizers. in addition to the consequences of agriculture, the increase in water pollution is also caused by domestic waste and industrial waste disposal. according to the president director of perum jasa tirta i, around 60% of the waste that pollutes the brantas river comes from household waste. the rest comes from industrial waste and toxic and hazardous materials. under these conditions, the reservoir water will be polluted by these wastes, namely organic agricultural waste, domestic and industrial waste, and other toxic or hazardous materials. it can worsen the condition of the reservoir water in the sutami reservoir because this reservoir gets its water supply from the brantas river [5]. due to the increasing pollution of the sutami reservoir, it is necessary to determine the water quality status and the pollution load capacity. a water quality model is the mathematical representation of pollutant fate and transport within a water body that may be coupled with a mathematical expression of the movement of pollutants from land movement from land-based sources to a water body [6]. process-based hydrodynamic and water quality models have been widely applied for simulating and predicting temperature dynamics and constituent transport in surface water bodies such as lakes, rivers, and estuaries [7], [8], [9], [10], [11], [12], [13]. the linear regression analyses are used for the water quality parameters. they measure higher and better levels of significance in their correlation coefficient. the systematic calculation of regression analysis provides indirect means for the fast monitoring of water quality [14]. this study aimed to determine water quality, water quality status, and mathematical modelling (regression analysis) of water quality status in sutami reservoir. 2. material and methods 2.1. study location sutami reservoir is located in karangkates village, sumber pucung district, malang regency (figure 1). the water quality monitoring is carried out by perum jasa tirta i. the water quality monitoring stations in the sutami reservoir are divided into 3, namely the upstream sutami reservoir monitoring station, the middle sutami reservoir monitoring station, and the downstream sutami reservoir monitoring station. the upstream sutami reservoir monitoring station is divided into two depths, namely depth i (0.3 m) and depth ii (4 m). the middle sutami reservoir monitoring station is divided into three depths, namely depth i (0.3 m), depth ii (5 m), and depth iii (10 m). at the downstream sutami reservoir monitoring station, it is divided into three depths, namely depth i (0.3 m), depth ii (5 m), and depth iii (10 m) (figure 2). figure 1. research site map civil and environmental science journal vol. 5, no. 1, pp. 064-077, 2022 66 figure 2. details of the depth of the sutami reservoir monitoring station 2.2. data collection field data are essential for models to predict assumed scenarios or future events [15]. this study uses secondary data. the data collection used in this study to obtain a mathematical model of the water quality status of the sutami reservoir is as follows: 1. rainfall data around the sutami reservoir consisting of st. kalipare, st. geophysics, st. sumberpucung, st. kepanjen, st. ngajum, st. karangsuko, and st. gondanglegi in 2010-2019. 2. data on water quality bod, cod, do, nh3-n, tss, and ph in the upper sutami reservoir at depth i (0.3 m) and depth ii (4 m) in 2015-2019. 3. data on water quality bod, cod, do, nh3-n, tss, and ph in the middle sutami reservoir at depth i (0.3 m), depth ii (5 m), and depth iii (10 m) in 2015-2019. 4. data on water quality bod, cod, do, nh3-n, tss, and ph in the sutami downstream reservoir at depth i (0.3 m), depth ii (5 m), and depth iii (10 m) in 2015-2019. 2.3. work steps in general and concise, the steps in this research are as follows: a. collecting rainfall data at rainfall stations around the sutami reservoir consisting of st. kalipare, st. geophysics, st. sumberpucung, st. kepanjen, st. ngajum, st. karangsuko, and st. gondanglegi to determine the average rainfall area using the arithmetic mean method. the average or arithmetic method is very simple in determining the average rainfall in a certain area [16]. b. determine the dry season in the area around the sutami reservoir. in determining the dry season, using the bmkg rules, the dry year is the amount of rainfall less than 85% of the average rainfall observed [17]. c. collecting water quality data in the sutami reservoir at each water quality monitoring station. d. grouping the water quality data in the sutami reservoir at each water quality monitoring station for the dry season. civil and environmental science journal vol. 5, no. 1, pp. 064-077, 2022 67 e. conduct a data homogeneity test at each water quality monitoring station using the f test. the amount of f is in the form of a ratio (ratio). fcr values can be obtained from table f for various values of level of significance (α) [18]. f. analyzing water quality at each water quality monitoring station using the pollution index method [19]. g. determine the water quality status at each monitoring station according to water quality standards [20]. h. determining water quality modeling at each monitoring station according to linear regression models, exponential regression models, logarithmic regression models, polynomial regression models, and multiple regression models [21]. 2.4. the formulas used in this article a. trend test with mann-whitney test the following is the correlation coefficient formula using the mann and whitney method: statistical parameter value calculation formula: u1 = n1 × n2 + ( n1 n2 ) × (n1 + 1) − rm (1) u2 = n1 × n2 − u1 (2) z = u−(n1n2) 2 ( 1 12 {n1n2(n1+n2+1)}) 1 12 (3) b. variant stability test the following is the formula for the variance stability test (f-test): f = 𝑁1.𝑆1 2(𝑁2−1) 𝑁2.𝑆2 2(𝑁1−1) (4) c. stationer test the following is the formula for the stability test of the average value (t-test): σ = ( 𝑵𝟏.𝑺𝟏 𝟐 +𝑵𝟐.𝑺𝟐 𝟐 𝑵𝟏+𝑵𝟐−𝟐 ) 𝟏 𝟐 (5) t = 𝑿𝟏̅̅̅̅ −𝑿𝟐̅̅̅̅ 𝝈( 𝟏 𝑵𝟏 + 𝟏 𝑵𝟐 ) 𝟏 𝟐 (6) d. fisher's test in this study, the analysis of variance used the f test (fisher's test) f = (𝑛−𝑘).∑ 𝑛1(𝑋𝑖̅̅ ̅−�̅�) 2𝑘 𝑖=1 (𝑛−𝑘).∑ ∑ (𝑋𝑗𝑖̅̅̅̅̅−�̅�)2 𝑗=𝑛𝑗 𝑗=1 𝑘 𝑖=1 (7) where; u1, u2 = statistical parameter for each group rm = maximum rating total value n1, n2 = total data for each group z = test coefficient s1, s2 = standard deviation of group 1 data, the standard deviation of group data 2 f = f test count value t = t test count value 𝑋1,̅̅̅̅ 𝑋2,̅̅̅̅ = the average value of group 1 data, the average value of group 2 data civil and environmental science journal vol. 5, no. 1, pp. 064-077, 2022 68 3. result and discussion 3.1. hydrological test and determination of seasonal division 3.1.1. double mass curve consistency test to test the consistency of the data, one of them can use multiple mass curve analysis. this multiple mass curve analysis is for annual rainfall data from an area. multiple mass curves are one of the graphical methods for testing the consistency and similarity of hydrological data types from a rainfall station [21]. in the consistency test, it is illustrated on line 45 on the scatter diagram. determine if there is a change in the slope of the scatter diagram. suppose the graph shows a point with a change in slope. in that case, it is necessary to correct the recording of rain data using a correction factor. the double mass curve test results show that the maximum annual daily rainfall for the seven stations is 1354 mm – 3785 mm, with an average of 2198. the following are the analysis results using the multiple mass curve test (table 1). table 1. hydrological analysis with double mass curve test year annual rainfall data (mm) st. kalipare st. geofisika st. sumberpucung st. kepanjen st. ngajum st. karangsuko st. gondanglegi 2010 3017 3238 3049 3228 3265 3214 3225 2011 1621 1680 1551 1673 1716 1602 1572 2012 2117 2139 1983 2084 2145 2009 2052 2013 2599 2470 2677 2749 2742 2645 2550 2014 1543 1973 1681 1549 1625 1560 1354 2015 1879 1731 1972 1972 2041 1991 2031 2016 3092 3785 3231 3319 3272 3239 3323 2017 2627 2066 2356 2290 2345 2244 2240 2018 1514 1397 1613 1720 1598 1544 1671 2019 1677 1685 1809 1719 1697 1640 1646 3.1.2. absence of trend test with mann-whitney test the mann-whitney correlation test tests two data groups to determine whether the data come from the same population. by using equation (1-3), it was found that the value of z count. based on the table of tc values for normal distribution [21], for a 5% confidence degree, the value of zc = -1.96 is obtained because z count < z table. therefore, the results obtained that the hypothesis was accepted. the measurement station data was data that came from the same population. thus the rain station data comes from the same population (table 2). 3.1.3. stationer test with variant stability test a stationary test is used to test the stability of the variance and the average of hydrological data. from the test results, it will be known whether the value of the data variance is homogeneous or not. at the degrees of freedom dk1 = n1 – 1 = 4 and dk2 = n2 – 1 = 4 and the degree of confidence is 5%, the f table is 6.39. using equation (4), the calculated f value is smaller than the f table value = 6.39. then the hypothesis is accepted (table 3). civil and environmental science journal vol. 5, no. 1, pp. 064-077, 2022 69 table 2. hydrological analysis with the mann-whitney test mann whitney test rainfall station kalipare geofisika sumber pucung kepanjen ngajum karangsuko gondanglegi rm 29 34 31 28 32 28 29 u1 11 6 9 12 8 12 11 u2 14 19 16 13 17 13 14 z count -0.31 -1.36 -0.73 -0.10 -0.94 -0.10 -0.31 z table 1.96 1.96 1.96 1.96 1.96 1.96 1.96 result accepted accepted accepted accepted accepted accepted accepted table 3 shows that the rain data at seven rain stations around the sutami reservoir are accepted, meaning the variance value is stable or homogeneous. table 3. hydrological analysis with variant stability test (f test) f test rainfall station kalipare geofisika sumberpucung kepanjen ngajum karangsuko gondanglegi n1.s1(n2-1) 4306664 9144898 8183346 13743466 10860026 12459010 15008674 n2.s2(n1-1) 15548514 9878444 7332564 11037090 8480386 9272980 11732524 f count 0.28 0.93 1.12 1.25 1.28 1.34 1.28 f table 6.39 6.39 6.39 6.39 6.39 6.39 6.39 result accepted accepted accepted accepted accepted accepted accepted 3.1.4. stationer test with stability test average value by using equation (5-6), the results obtained for the degrees of freedom dk = n1 + n2 -2 = 5 + 5 – 2 = 8, and the degree of confidence 0.025 in the two-way test, the t-table value = 2.31. the value of t count is smaller than the t table value = 2.31. then the hypothesis is accepted. it is found that the rainfall data at seven rain stations around the sutami reservoir are all accepted, which means the variance value is stable or homogeneous. (table 4). table 4. hydrological analysis with average value stability test (t-test) t-test rainfall station kalipare geofisika sumberpucung kepanjen ngajum karangsuko gondanglegi α 787.70 771.02 696.33 880.00 777.42 824.09 914.15 t -0.16 0.86 -0.45 0.12 0.56 0.15 -0.40 t table 5% 2.31 2.31 2.31 2.31 2.31 2.31 2.31 result accepted accepted accepted accepted accepted accepted accepted 3.1.5. determination of season determination of the dry and wet seasons is based on the regional average rainfall, which is calculated using the arithmetic mean method. according to bmkg, the wet (w) year is the rainfall greater than 115% of the observed average. the dry year (d) is less than 85% of the observed average rainfall [17]. the following is the result of determining the distribution of seasons in the sutami reservoir area (table 5). civil and environmental science journal vol. 5, no. 1, pp. 064-077, 2022 70 table 5. the analysis of the seasons determination year month/rainfall (%) annual rainfall jan feb march apr may jun jul aug sep oct nov dec 2010 86 105 101 122 75 65 48 34 107 87 147 66 87 2011 71 65 46 89 40 7 0 0 0 25 87 106 45 2012 114 99 111 70 50 3 3 0 0 20 59 150 57 2013 117 145 88 64 92 90 2 0 0 24 90 179 75 2014 98 58 67 52 41 44 1 0 0 0 73 156 50 2015 102 127 102 167 52 5 0 0 0 0 57 108 60 2016 114 164 101 117 92 75 36 26 95 114 154 105 99 2017 173 119 137 155 44 29 50 1 14 51 153 112 87 2018 137 150 127 75 27 58 9 0 18 2 126 126 71 2019 151 123 159 93 58 1 0 0 0 0 29 115 61 average 116 116 104 100 57 37 17 6 24 32 97 122 result w w w w d d d d d d w w the calculation above shows that november – april is the wet month, and june–october is a dry month. this dry month determines water quality status because the research only focuses on the dry. 3.2. water quality analysis the quality of the reservoir water flow regime or the level of water pollution is defined by several physical, chemical, and biological-microbiological materials and various other unique indicators [22]. 3.2.1. water quality test testing of water quality data is carried out by testing the homogeneity of the data or commonly called analysis of variance. the homogeneity test of this data is necessary before determining the water quality status. the homogeneity test of this data is used to determine the uniformity of the data because it was taken from several points for six years, from 2015 to 2020. in this study, the analysis of variance used the f test (fisher's test). table 6 is an example of an f test that has been carried out at several depths. because f count < f table, the data is homogeneous. the same is found in all ranges of years of observation and depth. table 6. analysis of water quality homogeneity test variance (f test) monitoring station parameter fcount ftable summary sutami reservoir depth i (0,3 m) bod 0.438 19.43 homogenous cod 0.474 19.43 homogenous do 0.058 19.43 homogenous nh3-n 0.078 19.43 homogenous tss 2.932 19.43 homogenous ph 0.574 19.43 homogenous civil and environmental science journal vol. 5, no. 1, pp. 064-077, 2022 71 3.2.2. determination of water quality status by pollution index method the analysis of determining the water quality status is carried out monthly with a class ii water quality class. according to the pollution index method, the water quality index value of the sutami reservoir for the upstream-middle-downstream sutami reservoir monitoring station from 2015 to 2019 are as follows (figure 3-5). figure 3. pollution index values at the upstream sutami reservoir monitoring station figure 3 shows the pollution index values at the upstream sutami reservoir monitoring station. the analysis was carried out at a depth of 0.3 m and 4. sampling was taken from may-october, assuming it was in the dry season. because the majority index value is 1.0 < pij < 5.0, it can be categorized as lightly polluted. figure 4. pollution index values at middle sutami reservoir monitoring station figure 4 shows the pollution index values at middle sutami reservoir monitoring station. the analysis was carried out at three depths, namely 0.3 m, 5 m, and 10. it is because the depth of the reservoir in the middle is deeper than in the upstream. sampling is still the same, taken in may-october, assuming it is in the dry season. due to the majority index value being 1.0 < pij < 5.0 can be categorized as lightly polluted. civil and environmental science journal vol. 5, no. 1, pp. 064-077, 2022 72 figure 5. pollution index values at the sutami downstream reservoir monitoring station figure 5 shows the same results as figures 3 and 4. the sutami downstream reservoir monitoring station water is included in the lightly polluted category. although currently, all observations are still in the lightly polluted category, it should be noted that the level of pollution is increasing from year to year. the pollution index in 2015 was around 0.9, but by the end of 2019, it rose to around 2.4. it needs attention from the authorities to prevent the pollution index from increasing. from the results of determining the water quality status using the pollution index method, the percentage of water pollution in the sutami reservoir is as follows (table 7). tabel 7. percentage of water quality status in 2015 to 2019 monitoring station class monitoring station upper sutami reservoir middle sutami reservoir downstream sutami reservoir 0,3 m 4 m 0,3 m 5 m 10 m 0,3 m 5 m 10 m meets quality standards 13% 10% 10% 7% 7% 10% 13% 3% lightly polluted 87% 90% 90% 93% 93% 90% 87% 97% conclusion lightly polluted lightly polluted lightly polluted lightly polluted lightly polluted lightly polluted lightly polluted lightly polluted the table above shows that the percentage of water that meets the quality standard is very small, ranging from 3%-13%, while lightly polluted is 87%-93%. 3.2.3. mathematical modelling of water quality status with regression model determination of the water quality characteristics of the sutami reservoir consists of; determining the status of water quality using the pollution index method, which is then carried out by mathematical modeling using a regression model; as well as determining the trophic status (total-p parameter), which is used to determine the carrying capacity of the total-p pollutant load in the sutami reservoir. determination of water quality characteristics of the sutami reservoir for three monitoring point locations with each depth. modeling the water quality status is determined after determining the water quality status using the pollution index method. the modeling used is the linear regression model, polynomial regression civil and environmental science journal vol. 5, no. 1, pp. 064-077, 2022 73 model, logarithmic regression model, exponential regression model, and multiple regression model (power). the following is the result of analyzing the mathematical model of water quality status (table 8-10 and figure 6-7). table 8. mathematical modeling of water quality status for upstream sutami reservoir monitoring station mathematical model upstream monitoring station 0.3 m 4 m linear regression y = 0.0497x + 0.9638 y = 0.0479x + 1.1074 r2 = 0.6822 r2 = 0.6693 polynomial regression y = -0.0001x2 + 0.0529x + 0.9464 y = -0,002x2 + 0,1089x + 0,7818 r2 = 0.6824 r2 = 0.7368 exponential regression y = 0.9976e0.032x y = 1,0809e0,0313x r2 = 0.6133 r2 = 0.5711 logarithmic regression y = 0.4587ln(x) + 0.592 y = 0,507ln(x) + 0,5881 r2 = 0.5432 r2 = 0.6996 multiple regression (power) y = 0.7687x0.3043 y = 0,7443x0,3446 r2 = 0.5162 r2 = 0.6479 from table 8 above, it is found that the r2 value that is the largest or close to 1 for the upstream monitoring station 1st depth (0.3 m) is a polynomial regression model with an r2 value of 0.6423 and for the upstream monitoring station, 2nd depth (4 m) is a polynomial regression model with an r2 value of 0.7368 so that the most suitable regression model with the variation of the pij value of the upper sutami reservoir is the polynomial regression model. table 9. mathematical modeling of water quality status for middle sutami reservoir monitoring station mathematical model middle monitoring station 0.3 m 5 m 10 m linear regression y = 0,0535x + 0,9124 y = 0,0454x + 1,1249 y = 0,0443x + 1,2099 r2 = 0.7204 r2 = 0.6570 r2 = 0.6382 polynomial regression y = -0,0009x2 + 0,0813x + 0,764 y = -0,0005x2 + 0,0595x + 1,0494 y = -0,0009x2 + 0,0736x + 1,0535 r2 = 0.7326 r2 = 0.6610 r2 = 0.6556 exponential regression y = 0,95e0,0351x y = 1,1378e0,0277x y = 1,1958e0,027x r2 = 0.6625 r2 = 0.5616 r2 = 0.5501 logarithmic regression y = 0,5278ln(x) + 0,428 y = 0,4358ln(x) + 0,7436 y = 0,4632ln(x) + 0,7439 r2 = 0.6546 r2 = 0.5656 r2 = 0.651 multiple regression (power) y = 0,6524x0,3699 y = 0,8909x0,2709 y = 0,8608x0,3004 r2 = 0.6850 r2 = 0.5007 r2 = 0.6346 civil and environmental science journal vol. 5, no. 1, pp. 064-077, 2022 74 table 9 shows that the r2 value is the largest or close to 1 for the middle monitoring station in the 1st depth (0.3 m), which is a polynomial regression model with an r2 value of 0.7326, for the 2nd depth (5 m) it is a polynomial regression model with an r2 value of 0.6570, and for 3rd depth (10 m) it is a polynomial regression model with an r2 value of 0.6556 so that the most suitable regression model with variations in the pij value of the central sutami reservoir is the polynomial regression model. table 10. mathematical modeling of water quality status for downstream sutami reservoir monitoring station mathematical model downstream monitoring station 0.3 m 5 m 10 m linear regression y = 0,0463x + 1,0683 y = 0,0509x + 1,0633 y = 0,0364x + 1,3856 r2 = 0.6902 r2 = 0.7585 r2 = 0.6577 polynomial regression y = -0,0001x2 + 0,0499x + 1,0489 y = -0,0021x2 + 0,1165x + 0,7132 y = -0,0008x2 + 0,0623x + 1,2473 r2 = 0.6905 r2 = 0.8371 r2 = 0.6785 exponential regression y = 1,0917e0,0288x y = 1,0732e0,0321x y = 1,3903e0,0203x r2 = 0.6060 r2 = 0.6933 r2 = 0.6050 logarithmic regression y = 0,4445ln(x) + 0,6789 y = 0,5421ln(x) + 0,5027 y = 0,3868ln(x) + 0,9868 r2 = 0.5950 r2 = 0.8039 r2 = 0.6940 multiple regression (power) y = 0,82x0,2944 y = 0,7299x0,3546 y = 1,0803x0,2278 r2 = 0.5909 r2 = 0.7913 r2 = 0.7109 figure 6. depiction of the mathematical model in the sutami reservoir (side view) civil and environmental science journal vol. 5, no. 1, pp. 064-077, 2022 75 table 10 revealed that the r2 value, which is the largest or close to 1 for the downstream monitoring station 1st depth (0.3 m), is a polynomial regression model with an r2 value of 0.6905, for the 2nd depth (5 m) is a polynomial regression model with an r2 value of 0.8371, and for 3rd depth (10 m) is a polynomial regression model with an r2 value of 0.7109. so that the most suitable regression model for the variation of the pij value of the sutami hilir reservoir. obtained a regression model with the highest r2 value at the upstream, middle, and downstream sutami reservoir monitoring stations for each depth (8 points of depth), namely the polynomial regression model. it means that the most suitable regression model for the variation of pij data is the polynomial regression model. it shows that this polynomial regression model is in the form of a curved line that tends to increase over time and then flatten to decrease at the end of the period. it means that the trend of the level of pollution tends to continue to rise and starts to stabilize until it decreases at the end of the period studied. figure 7. depiction of the mathematical model in the sutami reservoir (top view) figure 7 summarizes the results of research that has been carried out, namely that at all sampling locations, the best mathematical model is polynomial regression, and the reservoir water quality condition is lightly polluted. 4. conclusions this research has succeeded in determining water quality status using the pollution index method and mathematical modeling. the levels of parameters bod, cod, do, and ph has exceeded the existing quality standard values. meanwhile, the levels of tss and nh3-n parameters have not exceeded the existing quality standard values. the status of water quality using the pollution index method is in the lightly polluted category. the value of the total-p capacity that enters the sutami reservoir exceeds the maximum quality standard. the polynomial regression model is the most suitable mathematical model for the pollution index method data (pij). this research can be used as a reference for the management to determine the steps in managing industrial and residential areas and limiting the use of pollutant materials. civil and environmental science journal vol. 5, no. 1, pp. 064-077, 2022 76 acknowledgments the authors share their appreciation of the sponsorship of this study to the faculty of engineering, the university of brawijaya, research and community service (bppm-ft ub); public works and water resources of malang regency, jasa tirta 1 public corporation, and bpdas brantas for providing secondary data for this research. references [1] f. khorashadi zadeh, j. nossent, b. t. woldegiorgis, w. bauwens, and a. van griensven, "a fast and effective parameterization of water quality models," environ. model. softw., vol. 149, no. january, p. 105331, 2022, doi: 10.1016/j.envsoft.2022.105331. [2] c. liu, c. pan, y. chang, and m. luo, "an integrated autoregressive model for predicting water quality dynamics and its application in yongding river," ecol. indic., vol. 133, p. 108354, 2021, doi: 10.1016/j.ecolind.2021.108354. [3] i. t. telci, k. nam, j. guan, and m. m. aral, "optimal water quality monitoring network design for river systems," j. environ. manage., vol. 90, no. 10, pp. 2987–2998, 2009, doi: 10.1016/j.jenvman.2009.04.011. [4] i. kasiro et al., “indonesian large dams [bendungan besar di indonesia],” p. 394, 1995. [5] eko widianto, “brantas river is getting more and more worrying [sungai brantas makin memprihatinkan],” mongabay situs berita lingkunan, 2019. . [6] k. h. cho, y. pachepsky, m. ligaray, y. kwon, and k. h. kim, "data assimilation in surface water quality modeling: a review," water res., vol. 186, p. 116307, 2020, doi: 10.1016/j.watres.2020.116307. [7] s. weinberger and m. vetter, "using the hydrodynamic model dyresm based on results of a regional climate model to estimate water temperature changes at lake ammersee," ecol. modell., vol. 244, pp. 38–48, 2012, doi: 10.1016/j.ecolmodel.2012.06.016. [8] l. zhao et al., "three-dimensional hydrodynamic and water quality model for tmdl development of lake fuxian, china," j. environ. sci. (china), vol. 24, no. 8, pp. 1355–1363, 2012, doi: 10.1016/s1001-0742(11)60967-4. [9] m. bayer, t.k., burns, c.w. & schallenberg, "application of a numerical model to predict impacts of climate change on water temperatures in two deep, oligotrophic lakes in new zealand," hydrobiologia, vol. 713, pp. 53–71, 2013, doi: 10.1007/s10750-013-1492-y. [10] f. p. bernd wahl, "effect of climatic changes on stratification and deep-water renewal in lake constance assessed by sensitivity studies with a 3d hydrodynamic model," limnol. oceanogr., vol. 59, no. 3, pp. 1035–1052, 2014, doi: 10.4319/lo.2014.59.3.1035. [11] b. j. et al. soulignac, f., vinçon-leite, b., lemaire, "performance assessment of a 3d hydrodynamic model using high temporal resolution measurements in a shallow urban lake," env. model assess, vol. 22, pp. 309–322, 2017, doi: 10.1007/s10666-017-9548-4. [12] h. mohammed, h. m. tornyeviadzi, and r. seidu, "modelling the impact of weather parameters on the microbial quality of water in distribution systems," j. environ. manage., vol. 284, no. may 2020, p. 111997, 2021, doi: 10.1016/j.jenvman.2021.111997. [13] aleksandra ziemińska-stolarska and magdalena kempa, “modeling and monitoring of hydrodynamics and surface water quality in the sulejów dam reservoir, poland,” water, vol. 13, no. 3, p. 296, 2021, doi: 10.3390/w13030296. [14] k. saikrishna, d. purushotham, v. sunitha, y. s. reddy, d. linga, and b. k. kumar, "data for the evaluation of groundwater quality using water quality index and regression analysis in parts of nalgonda district, telangana, southern india," data br., vol. 32, p. 106235, 2020, doi: 10.1016/j.dib.2020.106235. [15] j. kim, d. seo, m. jang, and j. kim, "augmentation of limited input data using an artificial neural network method to improve the accuracy of water quality modeling in a large lake," j. hydrol., vol. 602, no. march, p. 126817, 2021, doi: 10.1016/j.jhydrol.2021.126817. [16] b. triatmodjo, applied hydrology [ hidrologi terapan]. yogyakarta: beta offset, 2008. civil and environmental science journal vol. 5, no. 1, pp. 064-077, 2022 77 [17] water resources and construction education and training center [pusat pendidikan dan pelatihan sumber daya air dan konstruksi], water allocation training reservoir operation module [modul operasi waduk pelatihan alokasi air]. bandung: ministry of public works and public housing [kementrian pekerjaan umum dan perumahan rakyat], 2017. [18] l. montarcih and w. soetopo, applied statistic for water resources engineering [statistika terapan untuk teknik pengairan]. malang: cv. citra malang, 2014. [19] the ministry of environment and forestry, statute of the state minister of the environment number 115 of 2003 concerning guidelines for determining the status of water quality [keputusan menteri negara lingkungan hidup nomor 115 tahun 2003 tentang pedoman penentuan status mutu air]. indonesia: ministry of public works and public housing [kementrian pekerjaan umum dan perumahan rakyat], 2003. [20] the republic of indonesia, government regulation of the republic of indonesia number 82 of 2001 concerning water quality management and water pollution control [peraturan pemerintah republik indonesia nomor 82 tahun 2001 tentang pengelolaan kualitas air dan pengendalian pencemaran . indonesia: state secretariat, 2001. [21] soewarno, hydrological data analysis: using statistical and stochastic methods: hydrological series [analisis data hidrologi : menggunakan metode statistika dan stokastik: seri hidrologi]. yogyakarta: graha ilmu, 2015. [22] d. sisinggih, s. wahyuni, and f. hidayat, reservoir sedimentation [sedimentasi waduk], 1st ed. malang: ub press, 2021. open access proceedings journal of physics: conference series civil and environmental science journal vol. 05, no. 02, pp. 129-143, 2022 129 rationalization of rainfall station density in the jatiroto subwatershed using ground and satellite rainfall data anggit gilang megantara1, sri wahyuni1*, lily montarcih limantara1 1 water resources engineering department, brawijaya university, malang, 65145, indonesia yuniteknik@ub.ac.id received 14-06-2022; accepted 27-09-2022 abstract. this study uses ground and chirps data to rationalize the density of rainfall stations in the jatiroto sub-watershed, lumajang regency. this study aimed to determine the suitability of the chirps satellite rainfall data to the measurement data. in addition, it determines the density of rainfall stations based on wmo standards. also, the kagan-rodda method uses measurement and satellite data to determine rainfall station recommendations' results. the method used for the suitability test uses the value of rmse, nse, correlation coefficient, and relative error. and the wmo standard for analyzing the number of rainfall station. knowing the rationalization and recommendations for placing rainfall stations using the kagan-rodda method by considering wmo standards, root mean square error, and interpolation errors. the results obtained include the appropriateness of satellite data, the number of rainfall stations at the research location according to wmo standards, and recommendations for rainfall stations based on kagan-rodda. keywords: appropriateness test, wmo, kagan-rodda, topography, regression analysis 1. introduction hydraulic structure planning requires a good hydrological analysis [1]. hydrological analysis requires rainfall data. the rainfall must be able to represent the conditions in the area and have good data quality. the data quality that will be taken for calculation of the analysis is influenced by the number of hydrological rainfall station that monitors a watershed. the jatiroto sub-watershed is one of the sub-watersheds located in lumajang regency, east java. this sub-watershed is one of the areas prone to flooding. the flood occurred because the jatiroto river could not accommodate the rainfall in the area. the jatiroto sub-watershed has an area of 322 km2 and has nine rainfall stations. the distribution of rainfall stations in the jatiroto sub-watershed is uneven, with no existing rainfall stations upstream of the sub-watershed. the quality of rainfall data in the subwatershed is not good enough because there are still missing rainfall data. this is due to the dysfunction of measuring instruments and human error, which causes an error in the measurement rainfall station. suppose ground rainfall data cannot be fulfilled. in that case, it can also be considered rainfall data from satellites such as chirps rainfall data [2]. so this study uses the chirps rainfall data in the following analysis. regarding operational costs, the more rainfall stations, the higher the maintenance costs. from these problems, optimal analysis is needed to determine the number of rainfall stations in the watershed. civil and environmental science journal vol. 05, no. 02, pp. 129-143, 2022 130 this study aimed to determine the suitability of the chirps satellite rainfall data to the measurement data. in addition, it determines the density of rainfall stations in the jatiroto sub-watershed based on wmo standards. also, the kagan-rodda method uses measurement and satellite data to determine rainfall station recommendations' results. 2. material and methods 2.1. study location this research is located in the jatiroto sub-watershed (figure 1). the watershed is included in the bondoyudo-bedadung watershed area. the jatiroto sub-watershed is located in lumajang regency, east java. this sub-watershed is located at the coordinates of 112º50' 00” 113º 22' 00” e dan 7º 52' 00” 8º 23' 00” s. the jatiroto sub-watershed has nine rainfall stationsincluding blimbing, gedang mas, kali penggung, kaliboto, maleman, plandingan, pondokwaluh, rojopolo and watuurip. figure 1. study location 2.2. data collection the data used in this study is secondary data obtained from the department of public works for water resources, east java province, and through the google earth engine. the data needed to complete this research are as follows: 1. ground rainfall data for 15 years in the jatiroto sub-watershed (2006-2020) 2. chirps satellite rainfall data for 15 years (2006-2020) 3. location data and the coordinates of rainfall stations in the jatiroto sub-watershed 4. map of jatiroto sub-watershed 2.3. work steps in general and concise, the steps in this research are as follows: a. collect the rainfall data. rainfall data used is ground rainfall data and chirps satellite rainfall data. ground rainfall data were obtained from nine existing rainfall stations. chirps satellite rainfall data was obtained from downloading rainfall data from nine existing rainfall station points. b. fill in the missing rainfall data. if there is missing ground rainfall data, then fill in the missing rainfall data first. c. next, the consistency test and hydrological statistical test were carried out. this study uses the consistency test of multiple mass curves, the f and t stationary test, the persistence test with spearman test, and the outliers test. civil and environmental science journal vol. 05, no. 02, pp. 129-143, 2022 131 d. the appropriateness test of uncorrected data is analyzed by calculating the rmse, nse, correlation coefficient, and relative error. then a regression analysis was carried out to obtain better quality data to get the corrected rainfall data. the appropriateness test of corrected satellite data was repeated by calculating the rmse, nse, correlation coefficient, and relative error. e. calculate the regional average rainfall using the thiessen polygon method to determine the area of influence of each rainfall station and calculate the average rainfall value. f. evaluate the density of the existing rainfall station based on the wmo standard to determine whether the existing rainfall station has fulfilled the standard. g. analyze the density of rainfall stations based on the kagan-rodda method to determine the recommended point for the kagan-rodda rainfall station based on wmo standards. 2.4. the formulas used the formulas used in this study include the following: a. reciprocal method px = ∑ ���������∑ �������� b. double mass curve consistency test s = � � = arctan � c. the absence of trend test �� = 1 − �6 ∑ (��)�� !"#$ − # % d. stationary test &'()�* = #"�"�(#� − 1)#����(#" − 1) �'()�* = ,"--− ,�---. / 10" + 10�/ e. persistence test �'()�* = �� 2 3 − 21 − �� �5 "� f. the appropriateness test rmse = 6∑ (7 89 )����� � nse = 1 − ∑ (7 89 )�����∑(7 87:;:<*<)� r = = ∑ 7 9 8 ∑ > ? ∑ 9 �@�a� .�a� .�6"c× ∑ 7��8(∑ 7��)�e���e��� 6= ∑ 9��8 (∑ 9��)�e���e��� kr = ∑ (f 89 )e���∑ 7 e��� g 100% g. coefficient of variation (cv) cv = hi� h. relative root mean square error (z1) z1 = jk . l�"8 :(m)n om.�p√rs(m)√�t%� i. interpolation error (z3) z3 = jk . uv"$ w1 − x(y)z + y.c�:(m)6r�i(y) [ j. the length of kagan-rodda l = 1,07 . 6_� where: px = missing rainfall data in rainfall station x pi = rainfall data on surrounding stations in the same period li = distance between rainfall station i and rainfall station x s = gradient kp = spearman rank correlation coefficient ,"-- = the average rainfall sample 1 ,�-- = the average rainfall sample 2 ks = serial correlation coefficient m = n – 1 qi = estimated data r(d) = correlation coefficient for station distance d civil and environmental science journal vol. 05, no. 02, pp. 129-143, 2022 132 n = the amount of data dt = the difference between rt and tt tt = the rank of time rt = ranking of hydrological variables in a time series t = t-test count value s1 = standard deviation of sample 1 s2 = standard deviation of sample 2 n1 = the size of sample 1 n2 = the size of sample 2 r(o) = correlation coefficient for short station distances d = distance between rainfall stations(km) d(o) = correlation radius cv = coefficient of variation a = area of watershed (km2) z1, z3 = relative root mean square error (%) and interpolation error (%) l = the length of kagan-rodda (km) 3. result and discussion 3.1. filling in missing rainfall data the method used to fill in the missing rainfall data is the reciprocal method. the reciprocal method is better because it considers the distance between rainfall stations in that location [3]. the following is an analysis of the calculation of estimated missing rainfall data at blimbing rainfall station in october 2012: table 1. calculation of missing rainfall data at blimbing rainfall station in october 2012 with the reciprocal method rainfall station rainfall data (pi) distance (li) li2 1/li2 p/li2 maleman 0 5.61 31.50 0.03 0.00 plandingan 30 5.89 34.73 0.03 0.86 rojopolo 0 6.64 44.11 0.02 0.00 amount 0.08 0.86 px 10.38 3.2. consistency test a consistency test is carried out to analyze whether the data has deviations or not due to the influence of errors during data recording. the consistency test in this study used the multiple mass curve method. the data is said to be consistent if it fulfills the resulting angle of 45°[4]. the following are the results of the calculation of the rainfall station data consistency test in the jatiroto sub-watershed: table 2. consistency test of the rainfall data rainfall station uncorrected α correction factor (fc) corrected α remarks ground data chirps ground data chirps blimbing 41.45 43.81 1.13 1.04 45.00 consistent gedang mas 47.74 47.62 0.91 0.91 45.00 consistent kali penggung 44.51 47.62 1.02 0.91 45.00 consistent kaliboto 50.10 45.91 0.84 0.97 45.00 consistent maleman 43.83 40.70 1.04 1.16 45.00 consistent plandingan 38.25 42.10 1.27 1.11 45.00 consistent pondokwaluh 43.29 43.25 1.06 1.06 45.00 consistent rojopolo 44.09 45.23 1.03 0.99 45.00 consistent watuurip 49.50 47.40 0.85 0.92 45.00 consistent civil and environmental science journal vol. 05, no. 02, pp. 129-143, 2022 133 3.3. stationary test the stationary test was carried out to know the stability of the variance value and the stability of the average value of the data. to determine the stability of the variance value using the f-test method and the stability of the average value using the t-test. suppose the calculation results in the rejected null hypothesis. the data has an unstable and inhomogeneous variance [5]. the data is stationary and homogeneous if the calculated value is smaller than the critical value [6]. the expected result of the stationary test is homogeneous data, namely data that is stable in the value of the variance and the average value. in this stationary test, rainfall measurements and rainfall data from the chirps satellite are used. stationary test results can be seen in table3. table 3. f stationary test of rainfall data no rainfall station α ground rainfall chirps rainfall remarks fcount fcritical fcount fcritical 1 blimbing 5% 0.49 4.21 0.62 4.21 stable variance 2 gedang mas 5% 0.47 4.21 0.88 4.21 stable variance 3 kali penggung 5% 0.99 4.21 0.88 4.21 stable variance 4 kaliboto 5% 0.99 4.21 0.84 4.21 stable variance 5 maleman 5% 0.07 4.21 0.83 4.21 stable variance 6 plandingan 5% 0.37 4.21 0.85 4.21 stable variance 7 pondokwaluh 5% 0.45 4.21 0.82 4.21 stable variance 8 rojopolo 5% 0.75 4.21 0.58 4.21 stable variance 9 watuurip 5% 0.57 4.21 0.84 4.21 stable variance table 4. t stationary test of rainfall data no rainfall station α ground rainfall chirps rainfall remarks tcount tcritical tcount tcritical 1 blimbing 5% -0.26 ±2.16 0.20 ±2.16 stable average 2 gedang mas 5% 0.75 ±2.16 0.27 ±2.16 stable average 3 kali penggung 5% 0.80 ±2.16 0.27 ±2.16 stable average 4 kaliboto 5% 0.30 ±2.16 0.21 ±2.16 stable average 5 maleman 5% -1.23 ±2.16 0.30 ±2.16 stable average 6 plandingan 5% -0.28 ±2.16 0.24 ±2.16 stable average 7 pondokwaluh 5% 0.17 ±2.16 0.30 ±2.16 stable average 8 rojopolo 5% -0.04 ±2.16 0.12 ±2.16 stable average 9 watuurip 5% -0.17 ±2.16 0.16 ±2.16 stable average 3.4. appropriateness test an appropriateness test is a procedure for evaluating a data model to illustrate the level of uncertainty in the model and predict a hydrological analysis. the appropriateness test was carried out to determine the comparison between satellite rainfall data and ground rainfall data. the appropriateness test was carried out in two stages. there are the uncorrected data appropriateness test and the corrected data appropriateness test. the appropriateness test for uncorrected data was carried out by calculating the rmse [7], nse [8], correlation coefficient [9], and relative error [10]. furthermore, regression analysis was carried out to improve the data quality. several regression equations will be used in the regression analysis, including linear, exponential, logarithmic, polynomial, and power regression. this civil and environmental science journal vol. 05, no. 02, pp. 129-143, 2022 134 regression will produce a regression equation, and one equation will be selected with the largest correlation coefficient value. this appropriateness test uses rainfall data with a value in that the data used is not equal to zero. the regression equation cannot be performed if there is a zero value. table 5 shows the results of the analysis of the uncorrected data appropriateness test. table 5. the appropriateness test of uncorrected data rainfall stations rmse nse kr r value interpretation % value interpretation stasiun blimbing 471 0.69 satisfactory 4.86 0.92 very strong stasiun gedang mas 542 0.53 satisfactory 5.28 0.76 strong stasiun kali penggung 423 0.50 satisfactory 1.13 0.71 strong stasiun kaliboto 353 0.67 satisfactory 4.97 0.84 very strong stasiun maleman 1007 0.36 satisfactory 10.31 0.70 strong stasiun plandingan 334 0.73 satisfactory 4.06 0.88 very strong stasiun pondokwaluh 346 0.73 satisfactory 6.99 0.90 very strong stasiun rojopolo 339 0.71 satisfactory 2.24 0.85 very strong stasiun watuurip 336 0.53 satisfactory 2.47 0.75 strong based on the calculation table for the uncorrected data suitability test, all nse interpretations have fulfilled all of them, and the interpretation of the correlation value is strong to very strong. however, the highest interpretation of the nse is only in the compliant category, so the data is corrected using regression analysis to obtain data of better quality. regression analysis uses five equations [11] to choose one equation with the largest r-value. figure 2 is an example of correcting data using regression analysis for the blimbing rainfall station. (a) (b) (c) (d) civil and environmental science journal vol. 05, no. 02, pp. 129-143, 2022 135 (e) figure 2. regression analysis with scatter plot in blimbing rainfall station 3.5. regression analysis the correction factor of the chirps satellite data is used to determine the magnitude of the x and y parameters which act as correction factors in the equation of the measurement data line and the chirps data. the line equation used is determined from the pattern of the rain measurement data series and chirps, as well as the correlation coefficient. next, the correction factor will correct the rainfall data using a predetermined equation by entering the chirps data into the equation. it is because the value of the largest correlation coefficient has a strong relationship and is almost close to the ground rainfall data. the largest correlation coefficient (r) value will be used to select the equation to correct the chirps satellite rainfall data. based on the regression analysis results for the blimbing rainfall station, the largest correlation coefficient value is 0.96 with a polynomial regression equation. so, the polynomial equation is used as an equation to get the corrected data. after the corrected data is obtained, the data appropriateness test is repeated for the corrected rainfall data. 3.6. the corrected data appropriateness test after obtaining the corrected data by correcting the regression equation with the largest correlation coefficient value, the corrected data appropriateness test was carried out by calculating the rmse, nse, correlation coefficient, and relative error. table 6 shows the results of the corrected data suitability test analysis. table 6. the corrected data appropriateness test rainfall station rmse nse re r value interpretation % value interpretation blimbing 254 0.91 good 3.67 0.96 very strong gedang mas 575 0.47 satisfactory 12.93 0.76 strong kali penggung 463 0.40 satisfactory 9.37 0.71 strong kaliboto 360 0.67 satisfactory 5.70 0.84 very strong maleman 880 0.51 satisfactory 8.96 0.73 strong plandingan 322 0.75 satisfactory 6.67 0.90 very strong pondokwaluh 273 0.83 good 1.67 0.91 very strong rojopolo 309 0.75 good 1.81 0.87 very strong watuurip 302 0.62 satisfactory 2.31 0.78 strong based on the corrected data appropriateness test analysis, the highest interpretation has changed from “satisfactory” to “good”. the interpretations of nse values that change from “satisfactory” to “good” include blimbing, pondokwaluh, and rojopolo. however, there is an nse value after correction whose value decreases, proving that not all corrected data can result in better data quality. but, the corrected civil and environmental science journal vol. 05, no. 02, pp. 129-143, 2022 136 data is closer to the ground rainfall data; the correlation value evidences this for the corrected data, which increases for each rainfall station. 3.7. regional average rainfall analysis the calculation of the regional average rainfall is used to obtain a rainfall value representing the rainfall value in the sub-watershed. there are several methods to calculate the regional average rainfall, such as the average method, thiessen polygon, and isohyet method. this study estimates the regional average rainfall using the thiessen polygon method. the thiessen polygon is used because the thiessen method is more accurate than the average method. the thiessen method is used in areas with uneven rainfall station distribution [12]. the jatiroto sub-watershed has an uneven distribution of rainfall stations, so this method is used in this analysis. this thiessen method will consider a certain weight at each rainfall station, which means that each rainfall station is deemed to represent rainfall in a watershed with a particular area, it is a weighting factor for rainfall at the rainfall station concerned. table 7 shows areas of influence using thiessen polygon method in the jatiroto sub-watershed. meanwhile, tables 8 and 9 show the regional average rainfall between ground and chirps. table 7. area of influence rainfall station rainfall station area thiessen coefficient percentage (%) rainfall station area thiessen coefficient percentage (%) km2 km2 blimbing 40.33 0.13 12.53 plandingan 11.89 0.04 3.69 gedang mas 30.16 0.09 9.37 pondokwaluh 5.89 0.02 1.83 kali penggung 122.52 0.38 38.05 rojopolo 42.25 0.13 13.12 kaliboto 31.99 0.10 9.93 watuurip 36.97 0.11 11.48 maleman 0.00 0.00 0.00 table 8. ground regional average rainfall table 9. chirps regional average rainfall year rainfall year rainfall 2006 1949 2006 1579 2007 2411 2007 1702 2008 2164 2008 1869 2009 2236 2009 1762 2010 3159 2010 3017 2011 1892 2011 1980 2012 1224 2012 1650 2013 2579 2013 2582 2014 1683 2014 1685 2015 1287 2015 1605 2016 3422 2016 3096 2017 2212 2017 2237 2018 1893 2018 1678 2019 1457 2019 1456 2020 2279 2020 2106 3.8. wmo analysis analyzing the density of rainfall stations can use the world meteorological organization (wmo) standard of reference. there is a minimum density value that wmo has mentioned, namely by considering the area of influence mentioned by wmo. thiessen polygon can calculate the area of influence of a watershed. civil and environmental science journal vol. 05, no. 02, pp. 129-143, 2022 137 based on the standards of the wmo, areas in the form of tropical mediterranean mountain plains can be represented by at least one rainfall station in every 100-250 km2 area [13]. suppose it refers to the standard that has been set. in that case, it can be concluded that the ideal number of rainfall stations needed in the jatiroto sub-watershed, which has an area of 322 km2 is 2-3 rainfall stations. table 10 shows the area of the influence of the rainfall station and its description. table 10. area of influence of rainfall station rainfall station area area of rainfall station in ideal condition rainfall station area area of rainfall station in ideal condition km2 100-250 km2 km2 100-250 km2 blimbing 40.33 not ideal plandingan 11.89 not ideal gedang mas 30.16 not ideal pondokwaluh 5.89 not ideal kali penggung 122.52 ideal rojopolo 42.25 not ideal kaliboto 31.99 not ideal watuurip 36.97 not ideal maleman 0.00 not ideal from the analysis table of the area of influence of each rainfall station, it can be concluded that just one rainfall station that fulfills the ideal conditions set by wmo is the kali penggung rainfall station which has an area of influence of 123 km2. the other rainfall stations have not fulfilled the ideal conditions set by wmo, so it is necessary to rationalize the density of rainfall stations in the jatiroto sub-watershed. 3.9. rainfall station density rationalization analysis using the kagan-rodda method one method that can be used to rationalize the density of rainfall stations is the kagan-rodda method. the kagan rodda method uses statistical analysis calculations. it considers the density of the rainfall station network with a relative root mean square error (z1), which should not exceed 10% [14], and also an interpolation error (z3). kagan stated that the network of eligible rainfall stations met the specified error criteria. according to kagan [14], the criteria for placing rainfall stations depend on the distance between rainfall stations(l), which is obtained from the relationship between rainfall station distances and the rainfall correlation of each rainfall station. the first step in performing the kagan-rodda analysis is calculating the variation coefficient. table 11 shows the results of the calculation of the coefficient of variation of the measurement data and chirps data data. table 11. the calculation of coefficient of variation overview parameter value ground data amount 31844.99 xaverage 2123.00 std deviation 619.82 coef. of variation 0.29 chirps satellite data amount 29193.90 xaverage 1946.26 std deviation 500.46 coef. of variation 0.26 civil and environmental science journal vol. 05, no. 02, pp. 129-143, 2022 138 from the calculation of the coefficient of variation, it can be concluded that the coefficient of variation of the chirps data is lower than the coefficient of variation of the ground rainfall data. it causes the chirps rainfall data to be more homogeneous than the ground rainfall data. next, the correlation coefficient between rainfall stations was calculated for the ground and chirps rainfall data. the correlation coefficient is determined by calculating the correlation value. the correlation coefficient will be used as a parameter of the relationship graph in the next analysis. the following is an example of calculating the correlation coefficient for the blimbing and gedang mas rainfall stations using measurement rainfall data. r = � ∑ �� �8 ∑ �� ∑ �������������6`� ∑ ��8w∑ ������ z�a� ∑ ��8w∑ ����� z�� ��� b���� c r = ("c×dde"f"gd)8($y"hd×�ec"y) 6w("c×f"c$hg"h)8$y"hd�z×(("c×dfg�hg"")8�ec"y�) r = 0.75 the correlation coefficient in all the rainfall stations is calculated for both ground rainfall dan chirps rainfall. after calculating the correlation coefficient, then calculating the distance between rainfall stations. the arcmap software is used for determining the distance between rainfall stations. the following table shows the results of calculating the distance between rainfall stations in the jatiroto sub-watershed. table 12. the distance between rainfall stations rainfall stations the distance between rainfall stations (km) blimbi ng gedan g mas kali penggu ng kalib oto male man plandin gan pondokw aluh rojop olo watuu rip blimbing 11 12 10 6 6 9 7 13 gedang mas 11 4 6 16 16 17 5 12 kali penggung 12 4 3 18 16 16 6 9 kaliboto 10 6 3 16 13 13 5 6 maleman 6 16 18 16 6 10 12 18 plandinga n 6 16 16 13 6 4 11 14 pondokw aluh 9 17 16 13 10 4 12 11 rojopolo 7 5 6 5 12 11 12 10 watuurip 13 12 9 6 18 14 11 10 after obtaining the correlation coefficient and the value of the distance between rainfall stations, these values are plotted in a relationship graph. the relationship graph will be used to determine the values of r(0) and d(0) in the following kagan-rodda analysis. in the relationship graph, the distance between stations is the x variable, and the correlation coefficient is the y variable. the following is a graph of the relationship between distance and correlation coefficient for ground rainfall and chirps data. civil and environmental science journal vol. 05, no. 02, pp. 129-143, 2022 139 figure 3. relationship graph of ground rainfall figure 4. relationship graph of chirps rainfall based on the graph shown above, the measurement data produces the equation y = 0.9513-0.024x. so it can be determined that the value of r(0) = 0.9513 and the value of the correlation radius d(0) = 41.67. the following is a calculation of the value of d(0) for measurement data: x(y). i @ss(m) = 0.9513-0.024x 8ii(m) = -0.024d �(y) = "y.y�g �(y) = 41.67 km in the same way, the d(0) value for chirps data is also calculated, and the d(0) value is 500 km. next, the value of d0 is used and becomes the input for calculating z1, and z3 also determines how many rainfall stations are needed. the z1 dan z3 used were by the previously analyzed wmo standards. tables 13 and 14 show the calculation results for z1 and z3 for ground and chirps rainfall. table 13. z1 dan z3 of ground rainfall n cv r(0) a (km2) d(0) a1/2 n1/2 (a/n)1/2 z1 z3 1 0.29 0.951 322.01 41.67 17.94 1.00 17.94 11.22% 13.98% 2 0.29 0.951 322.01 41.67 17.94 1.41 12.69 7.11% 11.93% 3 0.29 0.951 322.01 41.67 17.94 1.73 10.36 5.49% 10.89% 4 0.29 0.951 322.01 41.67 17.94 2.00 8.97 4.58% 10.23% 5 0.29 0.951 322.01 41.67 17.94 2.24 8.03 3.98% 9.75% 6 0.29 0.951 322.01 41.67 17.94 2.45 7.33 3.56% 9.38% table 14. z1 dan z3 of chirps rainfall n cv r(0) a (km2) d(0) a1/2 n1/2 (a/n)1/2 z1 z3 1 0.26 0.989 322.01 500 17.94 1.000 17.9445 3.58% 3.83% 2 0.26 0.989 322.01 500 17.94 1.414 12.6887 2.37% 3.33% 3 0.26 0.989 322.01 500 17.94 1.732 10.3603 1.87% 3.08% 4 0.26 0.989 322.01 500 17.94 2.000 8.97225 1.59% 2.92% 5 0.26 0.989 322.01 500 17.94 2.236 8.02502 1.40% 2.81% 6 0.26 0.989 322.01 500 17.94 2.449 7.32581 1.26% 2.73% based on the table for calculating z1 and interpolation error z3, it is found that for the jatiroto subwatershed area of 322 km2, according to the kagan-rodda method, three rainfall stations are needed. civil and environmental science journal vol. 05, no. 02, pp. 129-143, 2022 140 the value of the z1 of the ground rainfall data is 5.49%, and the z3 is 10.89%. while the value of z1 for the chirps data is 1.87%, and the value of the z3 is 3.08% for the chirps rainfall. the determination of the three rainfall stations has been adjusted to the wmo standard. figure 5 shows the relationship between the number of rainfall stations with z1 and z3 ground rainfall and the chirps rainfall. figure 5. z1 and z3 ground and chirps data figure 5 shows that the rainfall data from the chirps satellite has an average error (z1) and an interpolation error (z3) which is smaller than the measured rainfall. it is because there is no significant difference between chirps rainfall. because the correlation is strong, the resulting smoothing error (z1) and interpolation error (z3) is smaller. in addition, the value of z1 and z3 in the chirps satellite rainfall data is smaller than the ground rainfall data because the coefficient of variation (cv) value in the chirps satellite rainfall data is smaller. it proves that the chirps satellite rainfall data has a more evenly distributed (homogeneous) value than the ground rainfall data [15]. the next step is to determine the length of the kagan-rodda net triangle, which be used to draw the kagan-rodda net triangle. after the calculation, the length of l kagan-rodda in the jatiroto subwatershed was 11.09 km. l kagan rodda for ground rainfall data and chirps yielded the same value. it is because the variables that affect the kagan-rodda value are only the area of the watershed and the number of rainfall stations. the area and the number of rainfall stations of ground data and chirps are the same, producing the same value. it resulted in the rationalization of rainfall stations for ground rainfall data and chirps, yielding the same recommendations. next, create kagan-rodda nets by determining the reference stations. in this study, model 1 used blimbing rainfall station as a reference, and model 2 used kali penggung as a reference. figures 6 and 7 show the kagan-rodda nets and thiessen polygons for the blimbing reference station. 0% 2% 4% 6% 8% 10% 12% 14% 16% 0 1 2 3 4 5 6 z 1 & z 3 the number of rainfall station z1 of field rainfall z3 of field rainfall z1 of chirps rainfall z3 of chirps rainfall civil and environmental science journal vol. 05, no. 02, pp. 129-143, 2022 141 figure 6. kagan rodda net model 1 figure 7. thiessen polygon model 1 model 1 produces three recommendations for rainfall stations, including blimbing station as a reference station, station a and station b. each area of influence of the recommended rainfall station is shown in table 14. table 14. area of influence model 1 station area of influence (km2) weight area of influence (%) blimbing 83.899 26.1 a 130.277 40.5 b 107.829 33.5 based on the influence area, it can be concluded that there are still recommended rainfall stations that do not meet the ideal conditions of blimbing station, which has an influence area of less than 100 km2. then the second model was tried, and kali penggung acted as a reference station. figures 8 and 9 show the kagan-rodda net and the thiessen polygon map of the kali penggung as reference station. figure 8. kagan rodda net model 2 figure 9. thiessen polygon model 1 model 2 produces three recommendations for rainfall stations, including kali penggung station as a reference station, station a and station b. each area of influence of the recommended rainfall station is shown in table 15. civil and environmental science journal vol. 05, no. 02, pp. 129-143, 2022 142 table 15. area of influence model 2 station area of influence (km2) weight area of influence (%) kali penggung 117.515 36.5 a 104.429 32.4 b 100.062 31.1 based on the influence area of the second model, it can be concluded that all rainfall stations recommended by kagan-rodda have met the ideal wmo conditions. each of which has an area of influence between 100-250 km2. thus, the second model can be considered in rationalizing rainfall stations in the jatiroto sub-watershed. table 16 shows the recapitulation of the rainfall station coordinates recommended by the second model of the kagan rodda method. table 16. coordinate point of kagan-rodda recommendations kagan-rodda stations coordinate existing stations coordinate south latitude east longitude south latitude east longitude kali penggung -8° 4' 59.2" 113° 20' 54.66" gedang mas -8° 5' 12.19" 113° 18' 51.52" kali penggung -8° 4' 59.2" 113° 20' 54.67" kaliboto -8° 6' 32.18" 113° 21' 59.87" watuurip -8° 7' 19.02" 113° 24' 59.33" a -8° 0' 16.82" 113° 23' 36.05" b -8° 9' 41.58" 113° 18' 13.22" blimbing -8° 11' 14.65" 113° 19' 1.81" maleman -8° 13' 58.97" 113° 17' 40.96" plandingan -8° 13' 40.74" 113° 21' 6.3" pondokwaluh -8° 13' 18.72" 113° 23' 21.12" rojopolo -8° 7' 41.38" 113° 19' 37.56" 4. conclusions based on the analysis that has been done, it can be concluded that it is necessary to rationalize the rainfall stations in the jatiroto sub-watershed. it is because the density of the rainfall station does not meet wmo standards, and the rainfall stations are not evenly distributed. according to wmo standards, the jatiroto sub-watershed, with an area of 322 km2 requires 2-3 rainfall stations. rationalization was carried out using the kagan-rodda method, resulting in three recommendations for rainfall stations. the kagan-rodda recommendation maintains the kali penggung station, adds one rainfall station upstream of the sub-watershed, namely station a, and moves blimbing rainfall station to station b. kagan recommendation results in an area of influence that all meets wmo standards. civil and environmental science journal vol. 05, no. 02, pp. 129-143, 2022 143 acknowledgements the author would like to thank to the department of public works of water resources of east java province and the upt of water resources development of lumajang regency. references [1] z. r. alfirman. l. m. limantara. and s. wahyuni. “rasionalisasi kerapatan pos hujan menggunakan metode kagan-rodda di sub das lesti.” j. tek. sipil. vol. 8. no. 2. pp. 153– 164. 2019. [2] misnawati. r. boer. t. june. and a. faqih. “perbandingan metodologi koreksi bias data curah hujan chirps.” limnotek perair. darat trop. di indones.. vol. 25. no. 1. pp. 18– 29. 2018. [online]. available: https://limnotek.limnologi.lipi.go.id/index.php/limnotek/article/view/224 [3] i. w. yasa. m. b. budianto. and n. m. k. santi. “analisis beberapa metode pengisian data hujan yang hilang di wilayah sungai pulau lombok.” spektrum sipil. vol. 2. no. 1. pp. 49–60. 2015. [online]. available: https://spektrum.unram.ac.id/index.php/spektrum/article/view/42 [4] r. w. sayekti. s. wahyuni. m. bisri. m. j. ismoyo. and n. a. nathania. “mathematical model distribution of some water quality parameters in the reservoir.” vol. 5. no. 1. pp. 64–77. 2022. [5] 1995 soewarno. “rilid 2”. [6] n. salsabila. l. m. limantara. and j. sidqi. “banjir sulsel 3.” vol. 1. no. 2. pp. 736–749. 2021. [7] m. h. le. v. lakshmi. j. bolten. and d. du bui. “adequacy of satellite-derived precipitation estimate for hydrological modeling in vietnam basins.” j. hydrol.. vol. 586. no. november 2019. p. 124820. 2020. doi: 10.1016/j.jhydrol.2020.124820. [8] a. g. mengistu. t. a. woldesenbet. and y. d. taddele. “evaluation of observed and satellitebased climate products for hydrological simulation in data-scarce baro -akob river basin. ethiopia.” ecohydrol. hydrobiol.. vol. 22. no. 2. pp. 234–245. 2022. doi: 10.1016/j.ecohyd.2021.11.006. [9] q. wang. j. xia. d. she. x. zhang. j. liu. and y. zhang. “assessment of four latest long-term satellite-based precipitation products in capturing the extreme precipitation and streamflow across a humid region of southern china.” atmos. res.. vol. 257. no. 8. p. 105554. 2021. doi: 10.1016/j.atmosres.2021.105554. [10] s. wahyuni. d. sisinggih. and i. a. g. dewi. “validation of climate hazard group infrared precipitation with station (chirps) data in wonorejo reservoir. indonesia.” iop conf. ser. earth environ. sci.. vol. 930. no. 1. 2021. doi: 10.1088/1755-1315/930/1/012042. [11] h. y. chen and c. chen. “evaluation of calibration equations by using regression analysis: an example of chemical analysis.” sensors. vol. 22. no. 2. 2022. doi: 10.3390/s22020447. [12] t. torres. “penentuan jarak antar stasiun hujan dengan metode kagan rodda di das kedunglarangan kabupaten pasuruan provinsi jawa timur.” vol. 7. no. 1. p. 111. 2017. [13] l. sigar. c. ranesa. l. m. limantara. and d. harisuseno. “analisis rasionalisasi jaringan pos hujan untuk kalibrasi hidrograf pada das babak kabupaten lombok tengah.” j. tek. pengair.. vol. 6. no. 1. pp. 46–54. 2015. [14] s. h. br.. analisis hidrologi. jakarta: gramedia pustaka utama. 1993. [15] soewarno. aplikasi metode statistika untuk analisis data hidrologi. yogyakarta: graha ilmu. 2014. open access proceedings journal of physics: conference series civil and environmental science journal vol. 05, no. 02, pp. 202-214, 2022 202 risk mitigation of toll road development (a case study of transsumatera toll road) i wayan mandia1, putu ika wahyuni 2*, i nengah sinarta 3 1,2,3 master's program in infrastructure and environmental engineering, postgraduate program, warmadewa university, bali, indonesia * ikawahyuni9971@gmail.com received 05-08-2022; accepted 25-10-2022 abstract. to achieve the level of infrastructure performance as a middle-income country by 2025, as well as to catch up with the backwardness of infrastructure, specifically for toll road projects, the government targets that by 2021 indonesia will have 5200 km of toll roads. hence, there is a significant increase of 3000 km. the government, especially in the development of toll road infrastructure, gives a more significant portion to the purely private sector, bumn, and public private partnership government business entity cooperation. risk analysis is carried out by structuring risk using the rbs (risk breakdown structure) method and multiplying the impact value and frequency to get the risk level value for each risk factor. the results of the analysis obtained from rbs are further analyzed based on the practical experience of project implementers to determine their actions in overcoming risks, then analyzed and discussed again using a table comparing the amount of risk, comparison of the level of importance of risk (importance level) and the level of risk based on the payment system. the results obtained from this study can be seen as the most significant influence on the soil structure at the construction site. soil structure is a serious concern at the project site, affecting the project's cost, quality, and time. based on the analysis, the most effective handling of soft soil uses a piled slab with the highest score of 90.90, a pile slab of 85.6, and a stone column of 81.9. keywords: construction, toll road, risk, soft soil. 1. introduction the government claims to have built 718 km of toll roads since 2014, so that in 2019 the length of toll roads owned by indonesia will be 2200 km and added to 5200 km in 2024. in addition to increasing the budget for toll road construction, the government also has ambitions to increase the ranking of infrastructure development. from rank 82 in 2010 to 52 in 2018 and will continue to be improved. the construction of toll roads will be spread on the island of java, connecting all provinces in java, sumatra island as the artery of the trans sumatra route, and kalimantan island, which will be prepared to become the state capital. in addition to increased development funds, the government has even issued supporting regulations. amendments such as pp no 15 of 2005 on toll roads, [1] on changes to the previous regulation by adding two wheels may cross on toll roads or toll bridges, pp no 43 of 2013 on increasing the investment feasibility of toll roads built by the private sector and pp 30 of 2017 concerning the expiration of the concession period and the feasibility of the investment achieved. civil and environmental science journal vol. 05, no. 02, pp. 202-214, 2022 203 the role of the private sector in the construction of toll roads in indonesia was started in 1987 with the signing of the concession authorization agreement (pkp) with pt. jasa marga, which at that time was the toll road authority in indonesia, was 553 km long. the development of toll road construction in indonesia was halted in 1998 due to the monetary crisis and continued until 2005. the development of toll roads in other countries with many similarities in geographical and demographic conditions with indonesia, namely malaysia. the construction of toll roads in malaysia began in 1990 and currently has 3800 km. while indonesia has been building since 1978 until now, it is still far behind. toll road infrastructure projects are perilous due to high initial investment costs, high construction risk, long concession terms, and high operating and maintenance costs. as a result, private partners must generate sufficient income to repay investment costs, interest, and corporate profits. with a normal license period (20-30 years). many factors influence the low capacity of toll road development in indonesiaone of which is the risk factor in the implementation of toll road projects ([1]). the risks occur due to the following constraints: 1. not all these projects interest investors, as not all toll road projects are economically viable. the government has undertaken initiatives such as the infrastructure he summit to make the projects offered economically viable and investable. the indonesian government has introduced an infrastructure guarantee policy to increase the creditworthiness of infrastructure projects. to encourage private sector participation in infrastructure development in indonesia, pt. government decree no. 35/2009 on state equity participation will increase creditworthiness and provide guarantees to reduce project risk, thereby attracting more private investment, enhancing bankability, and increasing the number of ppp projects in indonesia. facilitate competition among potential bidders in the bidding process. [2]. 2. the land acquisition process dominates several toll road projects that have stalled. for example, the bekasi-cawang-kampung melayu (becakayu) toll road has been delayed for ten years. another toll road that stalled for 21 years is the bociwi ciawi-cigombong toll road, whose construction began in 1997 [3]. 3. investors are concerned that investing during long concession periods is risky. it is described in [4] and identified 53 risks in full concession toll road projects. these risks include site risk, design risk, construction, operational testing, sponsorship risk, revenue risk, flexibility risk, interface risk, etc., during feasibility studies, implementation and operation. the performance of toll road projects in indonesia is strongly influenced by the risks borne by investors/private/state-owned enterprises. the risks in question are risks that have been prepared during the preparation of the feasibility study, including planning risk, implementation risk, operational risk, and the overall risk of the toll road investment project. the complexity of risk allocation requires different handling. other research from [5] said risk management and internal control over the procurement of construction services should be conducted by all parties interested in risk control. [6] describes the highest number of risks originate from project activities, which indicates that the risks, especially at the implementation stage, arise more because the technical work in the field is very close to the environment around the project and all its activities. the risk variable that has the most influence on the implementation of road construction projects, which are the top three average values (mean) in the results of the analysis of this study, is the contractual risk variable, with the sub-variable being unilateral termination by the owner if the contractor does not carry out the obligations according to the contract; technical risk variable with sub-variable of material availability that arrived in the field different from that ordered; natural/natural risk variable with erratic weather sub variable based on [7]. risk analysis is carried out by structuring risk using the rbs (risk breakdown structure) method and multiplying the impact value and frequency to get the risk level value for each risk factor. the results of the analysis obtained from the rbs were further analyzed based on the practical experience of project implementers to determine their actions in overcoming risks, then analyzed and discussed again using a table comparing the amount of risk, comparison of the level of importance of risk civil and environmental science journal vol. 05, no. 02, pp. 202-214, 2022 204 (importance level) and the level of risk based on the payment system. the results obtained from this study are the type of risk. the level of risk at each stage of the project for a project with a combined lump sum contract system and unit price also depends on the type of work, project location, work complexity, and level of ability (experience) of the contractor, not only in the kind of contract used [8]. in a construction project, there must be risks. risk is a consequence of uncertain conditions. in construction projects, the risk can not be predicted as well because there is a lot of uncertainty in predicting problems [8]–[10]. for example, the land acquisition process in the indonesian toll road project has a high level of uncertainty. land acquisition activities could be completed quickly, while some have been very slow for years. it depends on several problems in the field, such as the project's priority, the availability of compensation money, community participation, the limited resources of the national land agency, and the time to complete the land acquisition claims in the district court and supreme court. the duration of a land acquisition depends on some main parties, i.e., the national land agency, the district court or supreme court, and the ministry of public works and housing [9]. another research regarding risk analysis at the toll road construction implementation stage uses descriptive methods and ahp (analytical hierarchy process) to determine the most dominant risk from the multiplication between likelihood and consequence. then the most prevalent risk is mitigated [11]. in the analysis of business assessment and risk management on investment feasibility decisions by considering uncertainty, it is obtained that risk variables that affect the feasibility study results include the inflation rate, forecast error of lhr volume, initial lhr volume, construction costs, and o&m costs. [12]. 2. material and methods 2.1. project management body of knowledge most pmbok guidelines, such as the critical path method (crm) and work breakdown structure (wbs), are unique to project management. project management knowledge includes 9 (nine) knowledge areas, namely: 1. project integration management 2. project scope management 3. project time management 4. project cost management 5. project quality management 6. project human resource management 7. project communications management 8. project risk management 9. project procurement management as well as 4 (four) additional knowledge areas for construction management projects, namely: 1. project safety management 2. project environment management 3. project investment management 4. project claim management specifically, project financing is crucial because the government has a shortage of the financing, so it requires cooperation and support from various parties. project financing, commonly known as project financing, is a type of large-scale financing scheme generally for the long term. in a project financing scheme, there is usually a group of investors who then act as shareholders of a newly formed company which is then known as a unique purpose entity or special purpose vehicle, abbreviated as spv. the spv company is then expected to design, build, and manage an infrastructure project. civil and environmental science journal vol. 05, no. 02, pp. 202-214, 2022 205 2.2. project management body of knowledge risk mitigation is an action or response to risks that occur during the project cycle. the countermeasures are not meant to eliminate the risks that occur but to minimize the frequency and consequences of the risks that occur (residual risk). according to flanagan and norman, in norken et al. [4], risk mitigation is carried out in several stages: holding, reducing, transferring, and avoiding risks. risk ownership is determined based on the party considered responsible and able to control and provide treatment for risks that arise during the project cycle. once the risk has been allocated, the less likely it is that disputes will arise between the parties involved. 2.3. toll road investment risk a risk is a situation that an individual or business faces with potential harm. below are some of the definitions proposed in the literature that are expected later to better understand the concept of risk. [13] proposed some risk definitions as follows: 1. risk is the chance of loss. 2. chance of loss is usually used to indicate a situation with an openness to loss or a possible loss. 3. risk is the possibility of loss. 4. possibility means the probability of an event being between zero and one. 5. risk is uncertainly the definition of risk conveys an understanding that risk is related to uncertainty. two types of uncertainty can be categorized as natural or accidental uncertainty and uncertainty due to human behavior or technology. natural or random uncertainties are caused by natural phenomena such as earthquakes, heavy rains, strong winds, and other natural disasters, which are difficult to predict due to their random nature. approaches can be statistical or probabilistic (including random elements). at the same time, technical uncertainty stems from human behavior caused by uncertainty in sampling, measurements, limited data, data analysis, or inadequate models and estimates [13]. [14] explained that in the risk analysis of the pekanbaru-dumai toll road construction, four main risks were identified, namely: 1. financing risk 2. development risk 3. equipment risk 4. force majeure risk 2.4. risk mitigation construction projects are unique, limited by cost, quality, and time. when carrying out construction projects, issues often arise that affect cost, quality, and time. therefore, according to this case, there is a very high need to research risk management [15]. the construction of toll roads can improve transportation efficiency and the economy of a region. however, t implementation of toll road construction will not be free from risks [8]. risk mitigation is an action or response to risks that occur during the project cycle. the countermeasures are not meant to eliminate the risks that occur but to minimize the frequency and consequences of the risks that occur (residual risk). according to flanagan and norman (in [16]) risk mitigation is carried out in several stages, namely, by holding, reducing, transferring, and avoiding risks [16]. risk ownership is determined based on the party considered responsible and able to control and provide treatment for risks that arise during the project cycle. once the risk has been allocated, the less likely it is that disputes will arise between the parties involved. several things can be done in dealing with risks, namely: 2.4.1. retaining risk (risk retention) risk-taking attitudes are closely related to the rewards involved in risk. measures are taken to accept/mitigate this risk, as the effects of the adverse event are still tolerable. civil and environmental science journal vol. 05, no. 02, pp. 202-214, 2022 206 2.4.2. reducing risk (risk reduction) risks are mitigated by examining the risks themselves, implementing preventative measures at the source of the risks, and combining measures to prevent them from collapsing. however, this measurement may leave residual risk that needs to be evaluated. 2.4.3. transfer of risk (risk transfer). suspension of risk transfer is through insurance of the risk arising from the transfer of part or all of the risk to another party. risky businesses and jobs are delegated to those who can manage and control them. 2.4.4. avoiding risk (risk avoidance) a risk-averse attitude is a way of avoiding losses by avoiding lossy activities. risk aversion can be done through denial. an example of risk aversion in construction projects is the termination of a contractual relationship (breach of contract). 2.5. soft soil in sumatra toll road construction soil always has an essential role in a construction work site. soil is the supporting foundation of a building, the construction material, or sometimes the cause of external forces on the building. the land has 3 (three) leading roles in transportation infrastructure buildings, namely as support, material, and load for transportation infrastructure buildings. as a supporting role, the land must have a carrying capacity that can support transportation infrastructure buildings that are on it. if the soil is compressed, the resulting subsidence of the building does not cause the transportation infrastructure to be damaged. figure 1. distribution map of indonesian soft soil (green color) [16] the main problems in constructing roads on soft clay are the subgrade's relatively low bearing capacity and relatively significant and long-lasting compression, as shown in figure 1. the distribution of soft soil is found in several areas in indonesia. if the subgrade is not repaired first, the infrastructure built on it will potentially be damaged before reaching the planned age. 2.6. soil improvement according to [17] about soil improvement is a process of improving the characteristics of compressibility, bearing capacity, permeability, and resistance to liquefaction of the soil in situ where the foundation of a building or infrastructure will be erected, so that the characteristics of the soil change permanently and have compressibility, bearing capacity, permeability, and stability or adequate liquefaction resistance and reach a safe level. the purpose of soil improvement is to increase density, civil and environmental science journal vol. 05, no. 02, pp. 202-214, 2022 207 soil stiffness, and liquefaction resistance to avoid excessive settlement, significant consolidation, and risky embankment stability. there are nine ways to improve soil, namely: 1. soil repair with cement (soil cement) 2. soil improvement with lime (soil lime) 3. soil improvement with ash (soil ash) 4. soil improvement with a chemical solution (solvent stabilization) 5. soil improvement by compaction 6. soil improvement with consolidation 7. soil improvement using the dewatering technique 8. soil improvement with land replacement (replacement) 9. soil improvement with permeation resin 2.7. expert test with delphi method the delphi method is a systematic method of collecting opinions from a panel of experts through a series of questionnaires, with a feedback mechanism through "rounds" of questions while maintaining the anonymity of the respondents' (experts') answers. the delphi method is a modification of the brainwriting and questioning methods. brainwriting is similar to brainstorming. it can generate new ideas, encourage creative problem-solving, and develop innovative solutions. but instead of discussing ideas out loud, brainwriting allows people to write down ideas and share them anonymously [18]. this method uses panels in a communication exercise through several written questionnaires. the delphi method was developed in the early 1950s to seek expert opinion [19]. most delphi policies relate to statements, arguments, comments, and discussions. we establish multiple methods of evaluating ideas expressed by groups of respondents and a rating scale for selecting these guidelines. b. ideas, interests, desirability, beliefs, and appropriateness of various policies and topics [20]. 2.8. research flow the research process begins with compiling a frame of mind in the form of a flow chart sequentially, starting from the search for data, the analysis process, and ending with the results of the study in the form of conclusions, as shown in figure 2. based on figure 2, the first step is conducting literature studies, selecting risk variables. and continued with the delphi method & risk assessment using experts' opinions, and continued with selecting the most influential risk and then choosing the method of handling. civil and environmental science journal vol. 05, no. 02, pp. 202-214, 2022 208 figure 2. research flowchart 3. result and discussion 3.1. research variables and instruments a variable is a concept that can be assumed as a range of values. a variable is a measurable amount that can vary or change easily, as seen in table 1. table 1. sources of construction risk for sumatra toll road construction [21] variable indicator number matrix toll road sector construction risk full concession soil structure risk 1 contamination/pollution to the site environment 2 disruption of biodiversity in forest areas/conservation areas 3 barriers to public transportation access 4 disruption of the comfort of the community around the project area 5 unclear output specifications 6 failed to maintain security and safety on site 7 increase in construction costs 8 poor contractor/subcontractor performance 9 default contractor/sub-contractor 10 design error 11 late completion construction 12 civil and environmental science journal vol. 05, no. 02, pp. 202-214, 2022 209 variable indicator number operational test risk (testing & commissioning) 13 changes in the scope of work 14 3.2. identification and risk analysis of sumatra toll road project implementation risk identification is an analysis process to systematically and continuously find risks (potential losses) that challenge the company. risks can be identified based on risk sources, events, and impacts. a source of risk is a condition that may increase the likelihood that the risk will materialize. an event is an occurrence that produces an influence or effect that can be either adverse or beneficial. risk identification is the initial stage of risk management which aims to describe and detail the types of risks that may occur from the activities or activities we will continue. each activity will identify uncertainties (potential losses, errors, discrepancies) that may occur, guided by "what can go wrong" from what will be done. risk identification can be carried out from the description of the planned activities to be carried out and guided by changes/uncertainties from various existing risk sources. identification of construction risks on toll roads by pt.pii. based on the risk identification carried out previously, an analytical risk rubric was created, which will later be given to experts in determining the most significant risks that occur in the construction of the sumatra toll road. this study uses the delphi method involving eight respondents. the results of this study have a range of values from 1 to 5. a value of 5 is for a very appropriate answer, a value of 4 is for an appropriate answer, a value of 3 is for a reasonably appropriate answer, a value of 2 is for a wrong answer, and a value of 1 is for a highly inappropriate answer. 3.2.1. stage 1 questionnaire in stage 1, there are 14 questions. from the results obtained, it can be seen that most of the respondents agree and even strongly agree that the risk of soil structure is the heaviest in the construction of the trans sumatra toll road. furthermore, the lowest risk is a design error can be seen in figure 3. figure 3. analysis of the biggest risks of toll road construction stage 1 expert test (research result) 3.2.2. stage 2 questionnaire the lowest result is that design errors can be eliminated when compiling the phase 2 questionnaire. so there are 13 questions at the time of the expert test with the phase 2 questionnaire. trans sumatra civil and environmental science journal vol. 05, no. 02, pp. 202-214, 2022 210 toll road. furthermore, the lowest risk is increased construction costs and failures due to contractor/subcontractor defaults can be seen in figure 4. figure 4. analysis of the biggest risks of toll road construction stage 2 expert test (research result) 3.2.3. stage 3 questionnaire the two lowest results from the questionnaire phase 2, namely the increase in construction costs and construction failures due to contractor/sub-contractor defaults, can be eliminated so that 11 final questions will be analyzed again using the delphi method. the expert test results show that the soil structure risk is the most challenging in implementing the sumatra toll road construction project, as seen in figure 5. figure 5. analysis of the biggest risks of toll road construction stage 1 expert test (research result) 3.3. result of data processing all civil engineering buildings stand on the ground. soil is the foundation for civil engineering buildings. the crucial thing in the soil is the presence of loading either by the construction itself or by civil and environmental science journal vol. 05, no. 02, pp. 202-214, 2022 211 traffic and other forces due to shear or earthquake. the type of soil and the consolidation behaviour of each of these types significantly affect the settlement of the construction. construction subsidence that occurs during construction is above the ground, and if it is not planned or calculated in the construction calculations, it will result in construction damage. the handling of soft soil is crucial in the transsumatra toll road project because most of the soil types in the project are soft soil. based on expert testing that has been carried out in stages, it can be seen that the most significant influence is on the soil structure at the construction site. soil structure is a serious concern at the project site, affecting the project's cost, quality, and time. furthermore, it is discussed in detail regarding handling the soil structure at the research site. 3.4. improvement method based on the literature study, it is stated that the soft soil problem can be solved by several methods, including pvd preloading, stone column, and pile slab. 3.4.1. pvd preloading. prefabricated vertical drain (pvd) is a soil improvement method that accelerates the consolidation process by shortening the drainage path of pore water in soft soil layers so that that water can be dissipated quickly. in addition, using pvd maximizes the radial direction's consolidation by placing high-permeability materials in the soil. 3.4.2. stone coumn column stone or stone column is a type of deep soil improvement (deep replacement) where aggregate/mortar is used as a replacement material in the soft soil layer, which is then compacted by vibrating and formed in rows like columns. 3.4.3. pile slab a pile slab foundation is a foundation structure supported by a pile group system and tied by a pile cap which is used to hold and transmit the load from the superstructure into the soil with the bearing capacity to hold it. 3.5. aspects of assessment according to [22], controlling cost-effective projects can be done in several ways, including: 1. detailed and completely defined scope of work 2. project risk analysis 3. accurate cost estimation and determination of budget guidelines 4. cost performance analysis and forecasting 5. performance measurement analysis 6. scope change control system 7. checking and correcting action 8. cost control procedure based on some of these treatments, simplification, and analysis of which method has the most positive impact on the construction of this toll road, the analysis is based on the assessment of work tools, resources, maintenance, implementation, time, technique, and cost. in addition, the analysis is based on experts' testing to provide the best assessment. in a construction project, several aspects that can be seen in table 2. civil and environmental science journal vol. 05, no. 02, pp. 202-214, 2022 212 table 2. analysis of the most influential aspects (research result) no. aspect respondent final score 11 10 9 8 7 6 5 4 3 2 1 1 maintenance 11 14 14 17 15 17 15 17 10 20 15 15 2 implementation 15 19 16 12 17 11 17 12 12 10 14 14 3 time 10 12 10 12 10 8 6 10 12 13 10 10 4 method 30 28 23 24 27 28 20 29 25 20 26 25 5 cost 28 23 30 20 20 24 22 23 26 27 32 25 6 working equipment 3 2 5 7 8 5 7 0 5 0 3 4 7 resource 2 2 2 5 2 3 7 5 5 5 0 4 8 ease of getting material 1 0 0 3 1 4 6 4 5 5 0 3 100 100 100 100 100 100 100 100 100 100 100 100 figure 6. influence analysis chart (research result) tools, resources, and ease of getting materials. these three aspects are further discussed as follows: 1. work tools work equipment has the most negligible weight of 3%, and the opinion of experts has the most negligible weight because the work tool has entered the implementation aspect. hence, the nonspecific aspect of the tool directly affects the construction of toll roads. 2. resources resources are included in the technical and implementation aspects, so the weight of resources is also tiny because other aspects represent them. 3. ease of getting materials materials have the most negligible aspect weight, similar to work tools, where materials are included in the implementation. civil and environmental science journal vol. 05, no. 02, pp. 202-214, 2022 213 3.6. field analysis results table 3. in-depth study of construction method (research result) no aspect weight value score pvd + preloading stone column pile slab pvd + preloading stone column pile slab 1 maintenance 15% 80 90 100 12 13.5 15 2 implementation 14% 80 70 95 11.2 9.8 13.3 3 time 10% 80 70 100 8 7 10 4 method 33% 80 80 100 26.4 26.4 33 5 cost 28% 100 70 28 28 25.2 19.6 85.6 81.9 90.9 based on table 3 regarding an in-depth study of the handling of soil structure, in this discussion, three methods of handling soft soils are taken, namely pvd preloading, stone column, and pile slab. tests are based on maintenance, implementation, time, technique, and cost. these parameters were obtained based on direct discussions with the resource persons. furthermore, the weighting/assessment of each parameter is carried out for each improvement method used. based on the assessment carried out, it was obtained that the highest value was obtained by the pile slab method at 90.9, then by the pvd+preloading method at 85.6, and the last was the stone column at 81.9, the most significant value indicating that this method is the best to be implemented in the field. however, it should be noted that this method may change at any time due to other unknown factors, so each development segment needs to be reviewed to adjust the method used. 4. conclusions from the results of the analysis and discussion conducted, the conclusions that can be drawn from this research are: 1. based on expert tests, the soil condition is known that the biggest problem in the construction of the indralaya-prabumulih toll road. 2. an analysis of the factors that can increase costs during and after construction is carried out to determine the method. from this analysis, it is known that: construction costs with the selection of construction type have an effect of up to 25%, then the implementation method affects 25%, and maintenance affects 14% 3. in the selection of risk management, use the opinion of experts who already have experience in the related field 4. the most effective handling of soft soil based on the analysis uses a piled slab of 90.90. the pile slab is 85.6, and the stone column is 81.9. based on the previous discussion, suggestions that can be given to improve further research are as follows: 1. analysis should be added with comparisons in other areas. 2. only three models were carried out in reviewing the handling model, and analysis with other handling models was needed to determine how far the boat was. references [1] pemerintah, “peraturan pemerintah (pp) tentang perubahan peraturan pemerintah nomor 15 tahun 2005 tentang jalan tol,” jakarta, 2009. [2] & i.-a. d. b. world bank, asian development bank, kemitraan pemerintah swasta panduan refrensi versi 2.0. terjemahan oleh indonesia infrastructure guarantee fund. jaakarta: pt. penjamin infrastruktur indonesia. 2014. civil and environmental science journal vol. 05, no. 02, pp. 202-214, 2022 214 [3] y. hardiyan, “setelah mangkrak 21 tahun, presiden jokowi resmikan tol ciawi-cigombing,” ekonomi bisnis, 01-dec-2018. . [4] indonesia infrastructure guarantee fund, “kerjasama pemerintah swasta di indonesia acuan alokasi risiko,” pt. penjamin infrastruktur indonesia, 2014. . [5] e. darma, “analisis manajemen risiko dan pengendalian intern pada pengadaan jasa konstruksi (studi kasus pengadaan jasa konstruksi pada skpd di lingkungan pemerintah provinsi sumatera barat),” j. pembang. nagari, vol. 2, no. 2, pp. 16–28, 2017. [6] c. yuliana, “manajemen risiko kontrak untuk proyek konstruksi,” rekayasa sipil, vol. 11, no. 1, pp. 9–16, 2017. [7] r. hidayati, m. natalia, f. adibroto, and r. saskia, “analisis variabel-variabel risiko pada pelaksanaan proyek konstruksi jalan,” j. ilm. rekayasa sipil, vol. 14, no. 2, pp. 46–56, 2017. [8] a. setiawan, e. walujodjati, and i. farida, “analisis manajemen risiko pada proyek pembangunan jalan tol cisumdawu (studi kasus: development of cileumyi-sumedang dawuan toll road phase i),” 2014. [9] k. putri and p. marzuki, “model of land acquisition productivity performance for toll road projects in indonesia,” civ. environ. sci., vol. 003, no. 02, pp. 84–94, oct. 2020. [10] a. nurdiana and b. setiabudi, “aplikasi manajemen risiko pada proyek jalan tol semarangsolo ruas bawen-solo,” 2018. [11] n. rahmawati and a. t. tenriajeng, “analisis manajemen risiko pelaksanaan pembangunan jalan tol (studi kasus : proyek pembangunan jalan tol bekasi-cawang-kampung melayu),” rekayasa sipil, vol. 14, no. 1, 2020. [12] e. v. dewi and n. a. wessiani, “analisis penilaian usaha dan manajemen risiko pada keputusan kelayakan investasi dengan mempertimbangkan ketidakpastian (studi kasus : akuisisi jalan tol oleh pt. x),” j. tek. its, vol. 10, no. 2, pp. 121–128, 2021. [13] e. j. voughan, fundamental of risk and insurance, 2nd ed. new york: john willey & sons, inc., 2018. [14] m. zulfiqar and a. sandhyavitri, “analisis risiko pembangunan jalan tol pekanbaru-dumai pada tahap konstruksi (studi kasus jalan tol pekanbaru-dumai),” j. online mhs. bid. tek. dan sains, vol. 1, no. 1, 2014. [15] i. nyoman, m. jaya, d. k. sudarsana, g. a. kade, and i. wiratni, “manajemen risiko terhadap pelaksanaan proyek konstruksi hotel di kawasan sarbagita,” j. spektran, vol. 7, no. 1, pp. 51– 57, 2019. [16] i. norken, i. b. n. purbawijaya, and i. g. n. o. suputra, pengantar analisis dan manajemen risiko pada proyek konstruksi. denpasar: universitas udayana press, 2015. [17] badan standarisasi nasional, persyaratan perancangan geoteknik sni 8460:2017. jakarta: badan standarisasi nasional, 2017. [18] anonim, “brainwriting enabling everyone to share their creative ideas.” . [19] a. zatar, p. b. katili, and suparno, “penentuan kriteria kualitatif penentu dalam pemilihan objek audit internal menggunakan metode delphi (studi kasus: dana pensiun pt. x),” j. tek. ind. j. ilmiah, keilmuan dan penerapan tek. ind., vol. 4, no. 1, 2016. [20] h. linstone and m. turoff, the delphi method: techniques and applications. 2002. [21] pt penjamin infrastruktur indonesia, acuan alokasi risiko 2020. jakarta: pt penjamin infrastruktur indonesia, 2020. [22] m. natalia et al., “identifikasi faktor-faktor penyebab cost over run pada proyek konstrusi jalan di sumatera barat.,” jirs, vol. 16, no. 1, pp. 28–38, 2019. civil and environmental science journal vol. 4, no. 2, pp. 173-182, 2021 173 study of water management development in petung swamp areas at the province of east kalimantan agus adi pramono1, suhardjono1, moch. sholichin1 1 water resources engineering department, universitas brawijaya, malang, 65145, indonesia agusadi001@gmail.com received 28-06-2021; accepted 09-08-20211 abstract. swamp area usually seen at the debouchment that close to the sea. swamp area can be used for farming area if it has a proper water management system. however, water management at the swamp area is hard to do and can be potentially become over drained in some areas. the aim of this study is to locate the potential areas that are able to occur over drained at petung swamp irrigation system and able to find solutions of the problems. the first step to do is doing survey to know the condition of the channel, finding hydrological data, and tidal data. the hydrological data are intended to get modulus drain discharge. the next step is running data with hecras application to get the result of water channel profile of all channels. after that, analyzing the groundwater level could be done and meet the conclusion whether the channel is having over drained or not. the result of this study is the areas of petung swamp irrigation that mostly having over drained condition are at the headwaters because the tide cannot reach the upper areas. the areas also have no floodgates, so the water journey couldn’t be occurred and not evenly distributed. keywords: groundwater level, over drained, swamp area, tides 1. introductions the increasingly limited productive land is one of the problems faced by the government in achieving the national food security program. with a lot of land conversion from technically irrigated land to nonagricultural land, it is also a factor in reducing agricultural crop production [1]. in the other hand, swamp areas are one of the nature wealth that is able to functioned that it can become one of the sources of growth that is considered capable of encouraging the pace of economic development and the prosperity of its people [2]. the main problem of the less significant development of swamp areas into agricultural is the quality and the amount of the water availability on those swamp lands. in addition, the poor condition of drainage system also capable to cause toxic substance which are harmful to the roots and causing 1 cite this as: pramono, a.a., suhardjono & sholichin, m. (2021). study of water management development in petung swamp areas at the province of east kalimantan. civil and environmental science journal (civense), 4(2), 173-182. doi: https://doi.org/10.21776/ub.civense.2021.00402.7 civil and environmental science journal vol. 4, no. 2, pp. 173-182, 2021 174 agricultural failure on the swamp. thus, or the success of agriculture in swamps is water management at the micro and macro levels in swamps [3]. the development of agricultural land in tidal swamp areas must pay attention to all supporting aspects in order to be successful. in tidal swamp land, agricultural land is easily contaminated by heavy metals due to stagnant wastewater. the presence of heavy metals in tidal water must get serious attention because it has serious impacts, including: the potential for carcinogens and metals have conservative properties that tend to accumulate in the human body [4, 10]. in order to avoid the wastewater stagnant, draining the water on the swamps area is t he most important thing to do, therefore the land is suitable for cultivation. however, on its process is potentially happen the over drained issues. over drained condition for a long time can cause peatlands to become dry and unable to absorb water again, because they experience irreversible drying conditions. this very dry condition also has the potential to cause land fires [5]. on this study, the analysis is done to figuring out the swamp land condition of petung swamp irrigation whether experiencing the over drained condition or not by doing the analyzation with the help of hecras application that is useful to knowing the water level of the canal and then the groundwater level will be known. after knowing the status, the aim of this study is to finding some solutions and recommendations for the problems before it gets harder to handle. furthermore, the solutions that given on this study are to make the water system management better so it can help the government program of achieving the national food security. the optimum groundwater level to avoid the dryness and land fire is about 60 – 100 cm. for the effort to maintain the the stability of the groundwater level remains shallow (± < 70 cm), it is necessary to install water gates [6]. 2. materials and methods this study was conducted by conducting an analysis to obtain the groundwater level on the land so that it can determine whether the land is experiencing over drain or not. in the analysis, the hecras application is used to assist in modeling so that the water level of the canal is obtained which will further be used as one of the parameters in calculating the groundwater level using the modified ellips kirkham method. in the analysis to get the groundwater level on the land, soil conductivity data is also needed obtained from soil drilling in the field at several points. 2.1. land hydrotopographic hydrotopographic is a condition that shown the water level to the topography around it. the type of land hydro topography at the swamp areas affect the type of water system used in order to optimize the performance of the existing channel [7]. the hydrotopographic category is an indication of the extent to which the possibility of overflowing water can inundate the land, and conversely the existing inundation can be drained. based on the category, tidal swamp land is divided into 4 categories, namely categories a, b, c, and d. category a is swamp land that is flooded by tidal water during the dry and rainy seasons. category b is swamp land that is overflowed by tidal water only during the rainy season. category c is land that is not flooded with high tide all the time. while category d is swamp land that is not at all flooded by tides. 2.2. ellips kirkham model modification one of the ways that can be used in determining the groundwater level is to use a modified method of the kirkham ellipse model [8]. in the research conducted by ngudiantoro, it is slightly different from that conducted by kirkham. in ngudiantoro's research, the modeling is done more simply, with the following assumptions: (1) elliptical model for groundwater table introduces the concept of mirror image, (2) the depth of the channel to the impermeable layer, and civil and environmental science journal vol. 4, no. 2, pp. 173-182, 2021 175 (3) the slope of the land surface is relatively small. the equations used in the modification method of the kirkham ellipse model are as follows: ……………………………………………………………… (1) with: h(x) = groundwater level above the impermeable layer at a distance x from the channel (m); hw = water level in the channel above the impermeable layer (m); r = rainfall (mm/day); et = evapotranspiration (mm/day); k = soil hydraulic conductivity (mm/day); x = distance from channel (m); 2s = distance between channels (m); l = channel width (m). figure 1. the illustration of the modified ellips kirkham model the figure above is explaining the illustration for the calculation of finding the groundwater level between 2 channels. the illustration above is explaining the assumpsion of the modified model of ellips kirkham formula. the modified formula looks simpler than the actual formula. the calcu lation takes approximately in the middle between 2 channels, so it can make the calculation easier. 2.3. over drained over-draining is a condition where the disposal of excess water in swamps occurs excessively so that the groundwater level decreases [11]. the occurrence of over-drained in the long term can cause dry conditions do not return. irreversible drying is a peat condition with a moisture content of <100%. in this condition, peat no longer has the ability to absorb water and nutrients, so it can no longer be planted. in this condition, peat will easily burn and be carried away by water [9]. some ways that can be done to reduce the risk of over draining are as follows: 1. adjust the distance between the drainage channels. 2. operate the sluice gate in the channel, in order to maintain the groundwater level and the pyrite layer will always be in anaerobic condition. 3. making long storage at the upstream of the channel. tertiary channel tertiary channel civil and environmental science journal vol. 4, no. 2, pp. 173-182, 2021 176 4. conduct water management on peatlands. 3. result and discussion hydrotopographic analysis needs to be carried out at the beginning of the analysis to determine whether the petung swamp land is included in the radish swamp or tidal swamp land. if the petung swamp irrigation system falls into the category of lowland swamp land, then the next calculation only uses rainfall. meanwhile, if the petung swamp irrigation area is included in the tidal swamp category, then the tidal height of sea water is one of the parameters included in the next calculation. in determining the hydrotopographic category, it is necessary to analyze the land surface elevation in the field and the highest tide level. the highest tide height obtained from the survey results for 15 days was 2.29 m. 3.1. figure from the analysis carried out, in figure 2, it can be seen that the study location, namely the petung swamp irrigation area main channel i and main canal ii, is included in the overflow type c (green shading) covering an area of 459.4 ha which is land still affected by tides the sea and overflow type d (blue shading) covering an area of 87.26 ha which is land without any influence from tides and has the potential to be over drained. for further, it is necessary to do an analysis using hecras to find out how far the influence of tides on the channel in main channel i and ii petung swamp irrigation system. figure 2. petung swamp irrigation area hydrotopographic map hec-ras analysis was carried out for each stake in the field. the results obtained from the analysis using the hec-ras application are in the form of a channel water level profile (figures 3 and 4). civil and environmental science journal vol. 4, no. 2, pp. 173-182, 2021 177 figure 3. example of channel water level profile results in hec-ras modeling (main channel i). figure 4. example of channel water level profile results in hec-ras modeling (main channel ii). from the figures above, the cross section in some stakes are showed that water fills the channel, like in the stakes p.216 b from main channel i. therefore, the cross section in some stakes are showed have less water, like in the stake p.142 from main channel ii. 3.2. table in the groundwater table profile analysis, all the stakes that have been made in the field are inputted and analyzed in the hecras application. the results of the hecras modeling will be one of the parameters in the calculation of the groundwater level using the modified kirkham elliptical model along with other parameters, namely evapotranspiration, effective rainfall, and soil conductivity. the following is a recapitulation of the height of the canal water level profile at all stake points. table 1. channel water level profile recapitulation no channel stake point hw (m) 1 s drain induk 1 p.216 b 1.83 p.243 b 0.95 p.253 0.89 civil and environmental science journal vol. 4, no. 2, pp. 173-182, 2021 178 no channel stake point hw (m) p.261 1.76 p. 92 b 1.73 2 main channel 2 p.131 b right 1.64 p.131 b left 1.64 p. 25 b right 1.85 p.25 b left 1.85 p. 11 a right 1.29 p. 11 a left 1.29 3 ss1ki sdp 1-2 ka p.325 a left 1.24 p.325 a right 1.24 4 ss2ki sdp 1-2 ka cp. 14 1.38 sdp 1-2 ka 5 ss1ka sdp 1-2 ki p.328 right 1.2 p.328 left 1.2 sdp 1-2 ki 6 ss1ka sdp 2-2 ka p.313 a right 1.17 p.313 a left 1.17 7 ss1ki sdp 2-2 ka p.311 a left 0.92 p.311 a right 0.92 8 ss2ka sdp 2-2 ka bm ptg 10 1.18 9 ss2ki sdp 2-2 ka p.34 b 1.14 sdp 2-2 ka 10 ss1ka sdp 2-2 ki p.361 a right 1.88 p.361 a left 1.88 11 ss1ki sdp 2-2 ki p.343 left 1.58 p.343 right 1.58 sdp 2-2 ki 12 ss1ki sdp 1-1 ka p.90 a 1.79 13 ss1ki sdp 1-1 ka p.366 right 1 p.366 left 1 sdp 1-1 ka 14 ss1ka sdp 2-1 ka p.377 a left 1.83 p.377 a right 1.83 15 ss1ki sdp 2-1ka p.447 a right 2.34 p.447 a left 2.34 16 ss2ki sdp 2-1 ka p.377 a right 1.83 p.377 a left 1.83 sdp 2-1 ka no channel stake point hw (m) 17 ss1ka sdp 3-1 ka p.441 a right 1.7 p.441 a left 1.7 18 ss1ki sdp 3-1 ka p.439 a left 1.72 p.439 a right 1.72 19 ss2ka sdp 3-1 ka p.385 right 1.22 p.385 left 1.22 20 ss2ki sdp 3-1 ka p.385 left 1.22 p.385 right 1.22 21 ss3ka sdp 3-1 ka p.354 a 1.75 22 ss3ki sdp 3-1 ka p.354 a 1.75 sdp 3-1 ka 23 ss1ka sdp 3-2 ka p.297 a right 1.52 p.297 a left 1.52 24 ss2ka sdp 3-2 ka p.43 a-1 1.5 sdp 3-2 ka 25 ss1ka sdp 3-2 ki p.487 right 1.45 p.487 left 1.45 26 ss1ki sdp 3-2 ki p.345 a left 1.21 p.345 a right 1.21 sdp 3-2 ki 27 ss1ka sdp 4-1 ka p.428 a right 1.55 p.428 a left 1.55 28 ss2ka sdp 4-1 ka p.396 right 1.3 p.396 left 1.3 29 ss1ki sdp 4-1 ka a.18-a left 0.81 a.18-a right 0.81 30 ss2ki sdp 4-1 ka p.426 a left 1.35 p.426 a right 1.35 31 ss3ki sdp 4-1 ka p.396 left 1.3 p.396 right 1.3 sdp 4-1 ka 32 ss1ka sdp 5-1 ka a.24-a right 0.78 a.24-a left 0.78 33 ss1ki sdp 5-1 ka a.27-a left 0.75 a.27-a right 0.75 34 ss2ka sdp 5-1 ka p.418 right 1.11 p.418 left 1.11 35 p.417 a left 1.37 civil and environmental science journal vol. 4, no. 2, pp. 173-182, 2021 179 no channel stake point hw (m) ss2ki sdp 5-1 ka p.417 a right 1.37 36 ss3ka sdp 5-1 ka p.405 0.4 37 ss3ki sdp 5-1 ka p.405 0.4 sdp 5-1 ka no channel stake point hw (m) 38 ss1ka sdp 6-1ka a.32 right 0.65 a.32 left 0.65 39 ss2ka sdp 6-1 ka cp.24 0.71 sdp 6-1 ka the height of the canal water level profile (hw) that has been calculated on table 1, are used to be one of the parameters at calculating ground water level by ellipse kirhkam method. the groundwater level analysis was carried out using the modified kirkham ellipse model method. in the calculation it is assumed that the elliptical model for the groundwater table intrudes the concept of mirror image (figure 1). with a value of k = 180576 mm/day, the following is a recapitulation of the results of the groundwater level. table 2. groundwater level recapitulation no channel stake point h(x) (m) 1 s drain induk 1 p.216 b 3.402 p.243 b 0.931 p.253 0.823 p.261 3.128 p. 92 b 3.043 2 s drain induk 2 p.131 b right 2.746 p.131 b left 2.755 p. 25 b right 3.477 p.25 b left 3.495 p. 11 a right 1.709 p. 11 a left 1.725 3 ss1ki sdp 12 ka p.325 a left 1.583 p.325 a right 1.592 4 ss2ki sdp 12 ka cp. 14 1.962 sdp 1-2 ka 5 ss1ka sdp 1-2 ki p.328 right 1.499 p.328 left 1.478 sdp 1-2 ki 6 ss1ka sdp 2-2 ka p.313 a right 1.413 p.313 a left 1.403 7 ss1ki sdp 22 ka p.311 a left 0.886 p.311 a right 0.891 8 ss2ka sdp 2-2 ka bm ptg 10 1.426 9 ss2ki sdp 22 ka p.34 b 1.349 no channel stake point h(x) (m) sdp 2-2 ka 10 ss1ka sdp 2-2 ki p.361 a right 3.608 p.361 a left 3.585 11 ss1ki sdp 22 ki p.343 left 2.564 p.343 right 2.543 sdp 2-2 ki 12 ss1ki sdp 11 ka p.90 a 3.257 13 ss1ki sdp 11 ka p.366 right 1.035 p.366 left 1.039 sdp 1-1 ka 14 ss1ka sdp 2-1 ka p.377 a left 3.400 p.377 a right 3.417 15 ss1ki sdp 21ka p.447 a right 5.540 p.447 a left 5.513 16 ss2ki sdp 21 ka p.377 a right 3.399 p.377 a left 3.406 sdp 2-1 ka 17 ss1ka sdp 3-1 ka p.441 a right 2.934 p.441 a left 2.943 18 ss1ki sdp 31 ka p.439 a left 3.003 p.439 a right 3.012 19 ss2ka sdp 3-1 ka p.385 right 1.534 p.385 left 1.533 20 ss2ki sdp 31 ka p.385 left 1.534 p.385 right 1.533 civil and environmental science journal vol. 4, no. 2, pp. 173-182, 2021 180 no channel stake point h(x) (m) 21 ss3ka sdp 3-1 ka p.354 a 3.116 22 ss3ki sdp 31 ka p.354 a 3.116 sdp 3-1 ka 23 ss1ka sdp 3-2 ka p.297 a right 2.365 p.297 a left 2.365 24 ss2ka sdp 3-2 ka p.43 a-1 2.305 sdp 3-2 ka 25 ss1ka sdp 3-2 ki p.487 right 2.165 p.487 left 2.155 26 ss1ki sdp 32 ki p.345 a left 1.521 p.345 a right 1.512 sdp 3-2 ki 27 ss1ka sdp 4-1 ka p.428 a right 2.461 p.428 a left 2.454 28 ss2ka sdp 4-1 ka p.396 right 1.737 p.396 left 1.740 29 ss1ki sdp 41 ka a.18-a left 0.684 a.18-a right 0.685 30 ss2ki sdp 41 ka p.426 a left 1.860 p.426 a right 1.871 31 p.396 left 1.737 no channel stake point h(x) (m) ss3ki sdp 41 ka p.396 right 1.740 32 ss1ka sdp 5-1 ka a.24-a right 0.644 32 33 ss1ka sdp 5-1 ka ss1ki sdp 51 ka a.24-a left 0.637 a.27-a left 0.597 33 34 ss1ki sdp 51 ka ss2ka sdp 5-1 ka a.27-a right 0.591 p.418 right 1.267 34 35 ss2ka sdp 5-1 ka ss2ki sdp 51 ka p.418 left 1.276 p.417 a left 1.915 35 36 ss2ki sdp 51 ka ss3ka sdp 5-1 ka p.417 a right 1.926 p.405 0.186 37 ss3ki sdp 51 ka p.405 0.186 sdp 5-1 ka 38 ss1ka sdp 6-1ka a.32 right 0.460 38 39 ss1ka sdp 6-1ka ss2ka sdp 6-1 ka a.32 left 0.448 cp.24 0.531 sdp 6-1 ka the table above is calculating the groundwater level (hx) each stakes of the channel. the calculation is using the modified kirkham elliptical model along with other parameters, namely evapotranspiration, effective rainfall, and soil conductivity. after obtaining the groundwater level at each stake point that calculated in table 2, the groundwater level profile is drawn. the description of the groundwater table is carried out to be able to estimate whether the land is over-drained or not. land is said to be over drained if the groundwater level is > 70 cm below the land. from the results of the analysis, it was found that over drained occurs a lot in the upstream part, namely in the primary channel at main canal i peg p.253 and p.243 b, secondary channel 2 right and left sdp 3-1 ka, secondary channel 1 left sdp 4 -1 ka, secondary channel 1 right and left sdp 51 ka, secondary channel 3 right and left sdp 5-1 ka secondary channel 1 and 2 right sdp 6-1 ka. as for main channel ii, only one channel is overdrained, namely secondary channel 1 left sdp 2-2 ka. the following is an example of depicting a groundwater table to get the status of whether the land is over drained or not. civil and environmental science journal vol. 4, no. 2, pp. 173-182, 2021 181 figure 5. example of groundwater profile modeling over drained condition from figure 5, there is an example of cross section that shows the groundwater level is not up to the standard (<70 cm) below the surface. therefore, the land in sdp 1 p.243 b, ss1 ki sdp 5-1 ka, and ss3 ki sdp 5-1 ka experiencing over drain. 4. conclusion from the analysis carried out by depicting hydrotopographic maps, it is known that the study locations, namely main canal i and ii of petung swamp irrigation area fall into the category of transitional lowland swamp. this means that the channel is still affected by the tides. in addition, from the analysis using hec-ras, it was found that the influence of the tides only reaches along the main channel. so, it can be said that the results of the hec-ras analysis are in accordance with the depiction of the hydrotopographic map. from the survey results in the field, it can be seen that the dimensions of the channel in the petung swamp drainage channel are more than adequate to accommodate the discharge that passes through the channel. however, there are no sluice gates at every intersection or meeting point of water which causes water regulation in the petung swamp irrigation area to cause problems on agricultural land. in addition, water sources for irrigation of swamps, which come from tides and rainfall, cannot be used effectively, especially during the dry season which is prone to water shortages and can cause over-drained problems in swamps. from the analysis, it can be seen that some parts of agricultural land are over drained. namely on the primary channel to the secondary channel on the main channel i and the secondary channel ss 1 ki sdp 3-2 ka on the main channel ii. thus, it can be classified the types of overflow in the rawa petung irrigation area, namely, type c overflow in main drainage channels in mains i and ii, and primary channels in main canal ii. meanwhile, the primary channel in main canal i and all secondary channels in petung swamp irrigation area are overflow type d because they are not affected by tides. the solution that can be done to overcome the problem of over-draining in petung swamp land is to build an automatic sluice gate (flapgate) at the channel crossing point along the main channel ii so that the door can open automatically when there is high tide and close automatically when the water is low. in addition, it is also necessary to add a stoplog at every intersection from the primary to the secondary channel so that the interpreter can regulate the water and maintain the stability of the groundwater level. it is also necessary to build a reservoir in the secondary channel to accommodate rainwater in the rainy season and can be used in the dry season if there is a shortage of water. with the problem channel mapped, the treatment can be carried out effectively. if the handling can be done properly and evenly, then the government's program of achieving the national food security can be achieved. reference [1] panggabean, e. w., & wiryawan, b. a. (2016). strategy for development of swamp irrigation land in the tidal swamp area of belawang south kalimantan. journal of irrigation, vol. 11 no. 1, 1-10. civil and environmental science journal vol. 4, no. 2, pp. 173-182, 2021 182 [2] ar-riza, & alkasuma. (2008). tidal swamp farming and its development strategy in the era of regional autonomy. journal of land resources, vol. 2 no. 2, 95-104. [3] imanudin, m., bakri, armanto, e., indra, b., & ratmini, s. (2018). land and water management option of tidal lowland reclamation area to support rice production. journal of wetlands environmental management, vol. 6 no. 2, 93-109. [4] mariana, z. t., mahbub, m., & hayati, a.(2015). sustainable land management support organic farming in tidal swamp area of south kalimantan: water quality. journal of wetlands environmental management, vol 3 no. 2, 95-100. [5] pandjaitan, n. h., & hardjoamidjojo, s. (1999). study of physical properties of peatlands in relationship with drainage for agricultural land. agricultural engineering bulletin, vol. 13 no. 03 , 87-96. [6] agus, f., anda, m., jamil, a., & masganti. (2014). indonesian peatlands. bogor: iaard press. [7] herawati, h., yulianto, e., & azmeri. (2020). the effect of hydrotopography and land use on tertiary channels in the rawa pinang dalam area. scientific journal, vol. 20 no. 1, 1-10. [8] ngudiantoro, pawitan, h., ardiansyah, m., purwanto, m. y., & susanto, r. h. (2010). modeling of groundwater level fluctuations in tidal swamp type b/c: case in south sumatra. postgraduate forum. vol. 33 no. 2, 101-112. [9] dariah, a., maftuah, e., & maswar. (2016). peatland characteristics. guidelines for the sustainable management of degraded peatlands, 16-29. [10] haribowo r., andawayanti u., lufira r.d. 2019. effectivity test of an eco-friendly sediment trap model as a strategy to control erosion on agricultural land. journal of water and land development. no. 42 (vii–ix) p. 76–82. doi: 10.2478/jwld-2019-0047. [11] permata, v. y., siswoyo, h., & haribowo, r. (2021). mapping of groundwater flow pattern and its quality index based on microbiological parameters in klojen district, malang city, east java, indonesia.civil and environmental science journal (civense), 4(2), 106-114. doi:https://doi.org/10.21776/ub.civense.2021.00402.1 civil and environmental science journal vol. 4, no. 2, pp. 183-191, 2021 183 development zoning of bindu river ecotourism based on eco culture i gusti agung putu eryani1*, i nyoman nuri arthana2, ni made ayu gemuh rasa astiti3 1 civil engineering department, faculty of engineering and planning, warmadewa university, denpasar, 80239, indonesia 2 department of architecture, faculty of engineering and planning, warmadewa university, denpasar, 80239, indonesia 3 animal husbandry department, agriculture faculty, warmadewa university, denpasar, 80239, indonesia *eryaniagung@gmail.com received 08-07-2021; accepted 09-08-20211 abstract. bindu river ecotourism is a tourist attraction that has natural potential as a place of recreation in the denpasar city area. apart from its potential there are still problems that exist in bindu river ecotourism. if zoning is not carried out in its development, the natural potential of the area that has been arranged can be reduced, for this reason, zoning is needed in its development to determine areas in the bindu river ecotourism area that are in accordance with the land use and development potential. based on the delineation and the existing potential, the bindu river ecotourism area is divided into a conservation zone and a recreation zone. for the conservation zone, it can be developed into several more zones in the upstream part, it can be developed into a zone for the development of the function of protecting water resources, a zone for the development of the function of protecting flora and fauna as well as limited recreational functions. while the recreation zone can also be developed into several more zones. the upstream recreation zone can be developed into a recreation function development zone and the downstream recreation zone can be developed into an educational function development zone. keywords: eco culture, river ecotourism, sustainable development, zoning 1. introduction rivers as one of the water resources have important benefits and roles in human life. the river that crosses the residential area is quite dense, nowadays its condition shows a tendency to get worse every year. increasing economic development activities, changes in land use, and increasing population growth have resulted in high pressure on the river basin on the environment [1]. high population growth and rapid development activities in riverside areas such as settlements and so on cause ecological pressure on ecosystems and river resources to increase as well. this pressure can 1 cite this as: eryani, i.g.a.p., arthana, i.n.n. & astiti, n.m.a.g.r. (2021). development zoning of bindu river ecotourism based on eco culture. civil and environmental science journal (civense), 4(2), 183-191. doi: https://doi.org/10.21776/ub.civense.2021.00402.8 civil and environmental science journal vol. 4, no. 2, pp. 183-191, 2021 184 certainly threaten the existence and sustainability of river ecosystems and resources, either directly or indirectly. ecotourism-based tourism area management can create sustainable tourism [2]. sustainable ecotourism planning is to help conservation to survive without changing the basic mission of ecotourism and its unique status in the global environmental scheme [3]. one of the important steps needed in anticipating this problem is to develop a comprehensive master plan for the development and revitalization of river ecosystems and resources [4]. currently, the denpasar city government organizes several rivers in denpasar into a public space. one of them is bindu river ecotourism which has been developed as a recreational object in denpasar city as part of the denpasar city clean river program since 2010 [3]. before being laid out, bindu river ecotourism often functioned as a household waste disposal site. the current condition in bindu river ecotourism is dominated by soft cape so that it can give a natural impression. bindu river ecotourism is located in banjar ujung, kesiman village, east denpasar district, denpasar city. bindu river ecotourism is an ecotourism-based tourism object which was just inaugurated on march 24, 2017 [4]. bindu river ecotourism is a tourist attraction that has the potential as a place of recreation for children, adolescents, parents, and families. bindu river ecotourism provides buoys, tires, and canoes for playing facilities in the waters of the bindu river tourist attraction. bindu river also provides several outdoor fitness facilities, several children's play facilities, and a neatly arranged garden. apart from the potential offered by bindu river ecotourism, there are still problems that exist in the bindu river including river water which has a lot of sediment, the lack of public awareness to care about the surrounding environment, and the lack of exposure by the public makes only the surrounding community know. if zoning is not carried out in its development, the natural potential of the bindu river ecotourism area that has been arranged can be reduced, for this reason, zoning is needed in its development to determine areas in the bindu river ecotourism area that are in accordance with the land use and development potential. 2. material and methods 2.1. research location this research was conducted at the bindu river ecotourism located in banjar ujung, kesiman village, east denpasar district, denpasar city (figure 1). bindu river is an ecotourism-based tourism object which was just inaugurated on march 24, 2017. figure 1. research location civil and environmental science journal vol. 4, no. 2, pp. 183-191, 2021 185 2.2. research tools and materials in this study, the tools used were drones, gps, cameras, google earth pro. drones, meters, cameras are used to see potential locations adapted to possible development zones. google earth pro is used to match the mapping results from the survey with imagery at the location, then used for zoning mapping based on the coordinates mapped during the survey. while the materials used in the form of primary data and secondary data. primary data was obtained from the results of a direct survey at the location around the bindu river ecotourism. while the secondary data used in the form of a literature review is used as the theoretical basis for determining zoning. 2.3. data analysis methods this research is descriptive quantitative research, where this research begins with problem analysis, then data collection is carried out, both primary and secondary data. primary data is taken by conducting a field survey to see the existing condition and then mapping the potential for regional development. based on this data, the delineation of the area is carried out to determine the development zones that can be carried out, then match the potential of the area with the appropriate development zone based on its potential. the results of the division of these zones can be used as a reference for the government and also bindu river ecotourism managers to develop the bindu river ecotourism area in the future so that the existing potential can be used sustainably to increase the economic level of the surrounding area without damaging the existing ecology. 3. result and discussion 3.1. the existing condition of bindu river ecotourism the length of the bindu river watershed is ± 1300 m, with an area of ± 22,100 m2. bindu river is located in east denpasar district, kesiman village. it consists of several banjars, namely: banjar dukuh, banjar ujung, banjar abianangka kaja and banjar abianangka kelod (figure 2). currently, the bindu river has been managed and developed as an ecotourism area. the ecotourism society defines it as responsible travel to natural areas that conserves the environment and improves the well-being of local people. a walk in the rainforest is not ecotourism unless the trip benefits the environment and the people who live there. a rafting trip is only ecotourism if it raises awareness and funds to help protect watersheds. a loose interpretation of this definition allows many companies to promote themselves as something they are not [5]. figure 2. the existing condition of the bindu river ecotourism area civil and environmental science journal vol. 4, no. 2, pp. 183-191, 2021 186 in the northern part of the bindu river ecotourism area, there is a parking area that can be used by the community when visiting the bindu river area which is usually used for car parking due to its large location, while the southern parking area is usually used for motorbike parking areas. then in the river area of the bindu river ecotourism, a bridge has been built with the inscription bindu river ecotourism which is usually used by visitors to take photos, and there is a culinary area that is usually used for visitors to enjoy food during recreation. however, during the covid-19 pandemic, this culinary area is not too crowded so only a few stalls are operating. the bindu river has considerable potential as river ecotourism in the middle of the city. it is still rare that a river in the middle of a city with identical problems can be arranged in such a way that it can be used as river ecotourism. 3.2. bindu river ecotourism problems although it has great tourism potential, currently the bindu river still has several problems, such as the existence of riverbank areas that have not been properly managed so that when the water rises during heavy rains, the risk of flooding will be even greater coupled with sediment shipments from upstream parts of the river, which causes siltation of the bindu river thereby reducing the river's storage capacity (figure 3). if the development of bindu river ecotourism is not managed properly, the development of the bindu river as ecotourism can threaten the sustainability of the bindu river ecosystem. figure 3. bindu river ecotourism problems 3.3. bindu river ecotourism area delineation the determination of the delineation of the area is based on the length of the existing development segment that has been previously determined, the physical condition of the environment, and the administrative boundaries of the banjar or environmental scale. based on these considerations, delineation of the area is determined, as shown in figure 4. figure 4. bindu river ecotourism area delineation civil and environmental science journal vol. 4, no. 2, pp. 183-191, 2021 187 based on the results of the delineation above, it can be seen that the bindu river development area is included in 4 (four) banjar/environmental administrative areas, namely; banjar dukuh, banjar ujung, banjar abiannangka kaja, and banjar abianangka kelod, with the length of the watershed used as long as 1300 meters or 1.3 km and an area of 22,100 m2 or 2.2 ha. 3.4. the basic concept of bindu river ecotourism development based on eco culture ecotourism aims to minimize environmental impacts, contribute to the economic development of local communities, and finance conservation and sustainable development programs [5]. therefore, the development of ecotourism as an industry or economic sector must be planned following the environment (human and natural). environmental vulnerabilities should be carefully considered and properly integrated into the area planning under the protection requirements. otherwise, the mental consequences of the environment will outweigh the short-term benefits of socio-economic development [6]. based on the consideration of the physical environment, socio-cultural conditions of the community, and the potential for activities that can be developed, the development of bindu river ecotourism can be carried out on an eco-culture basis. eco culture is a combination of the word ecological which is abbreviated as eco or in indonesian it is ecology and the word culture which in indonesian is culture. ecology can be defined as the study of the interrelationships between living things and their environment. eco or ecology is a combination of physical conditions that include the state of natural resources such as land, water, solar energy, minerals, and flora and fauna that grow on land and in the ocean, with institutions that include human creations such as decisions on how to use the physical that environment. all decisions made by all parties involved are always oriented to the balance of nature. meanwhile, culture is a means of the work, taste, and creation of the community. eco culture is a development and design concept that is oriented towards culture and the balance of nature. the consideration of establishing eco culture as the basic concept of developing the bindu river also aims to ensure the sustainability of the bindu river area as a city tourist destination. thus all forms of activities and arrangements in the context of development carried out must always be oriented to local culture and environmental sustainability. development must be carried out by utilizing the local potential and paying attention to the surrounding environment, both the physical and non-physical environment. 3.5. development zoning of bindu river ecotourism based on eco culture suparno [7] explained that the purpose of preparing a zoning plan is to divide the area into zones that are compatible with mutually supportive (compatible) designations and activities and separate them from incompatible activities. the determination of the zone is focused on the main activities and priorities for the use of coastal resources to facilitate control and utilization. sustainable development is a development process that optimizes the use of natural resources and human resources, by harmonizing natural resources with humans in development. [8]. the basis of ecotourism zoning must be based on regional ideology [9]. since the main task of bindu river ecotourism is the preservation and recreation of natural landscapes, the development of environmental management methods that are adequate for local environmental conditions and cultural traditions. according to the seville strategy, biosphere reserves must fulfill three functions: 1) conservation contribution to the preservation of landscapes, ecosystems, species, and genetic varieties; 2) development promote sustainable economic, social, cultural, and environmental development; 3) scientific and technical functions support for pilot projects, environmental education, training in the field of environment, research, monitoring related to local, regional, national, also global issues of environmental conservation, and sustainable development. civil and environmental science journal vol. 4, no. 2, pp. 183-191, 2021 188 figure 5. development zoning of bindu river ecotourism based on eco culture several studies confirm the importance of ecotourism for biodiversity conservation [10][11][12]. so in the development of the bindu river ecotourism area, it is necessary to pay attention to the concept of sustainability. therefore, based on its potential, the bindu river ecotourism area is divided into two zones, namely the conservation zone and the recreation zone (figure 5). a conservation zone is an area designated for the preservation and protection of water, flora, and fauna. while the recreation zone is an area designated for utilization through the development of recreational and educational activities. 3.6. conservation zone development concept for the conservation zone, it can be developed into several more zones, upstream can be developed into a zone for the development of the function of protecting water sources, where this zone can be used for water protection both in terms of quality and quantity. to support water protection in this zone, water cleaning facilities and water treatment facilities can be added. this zone will later become a guard for water catchment that falls so that it does not immediately become runoff so that the potential for flooding that occurs downstream of the bindu river can be reduced. in the middle part of the conservation, the zone can be developed as a zone for the development of flora and fauna protection functions, where for the function of flora and fauna protection it can be in the form of animal-friendly vegetation, animal breeding, and rare plant nurseries such as the gumi banten park (a place to plant plants that can be used for religious ceremonies), animal parks, fishing recreation, yoga facilities (elderly). conservation zone in bindu river ecotourism can be seen at figure 6. civil and environmental science journal vol. 4, no. 2, pp. 183-191, 2021 189 figure 6. conservation zone development 3.7. recreation zone development concept the recreation zone can also be developed into several more zones. the upstream part of the recreation zone can be developed into a recreation function development zone where at this location several development activities such as water recreation facilities and culinary facilities can be carried out. meanwhile, downstream of the recreation zone can be developed into a zone for the development of educational functions by carrying out several fish hatchery activities, agriculture, outbound, creative business training, art training, co-working space, and water galleries. recreation zone in bindu river ecotourism can be seen at figure 7. figure 7. recreation zone development by developing a conservation zone in the upstream area of the bindu river ecotourism area, it is hoped that it can become a water catchment area and water protection. during the rainy season, the area can catch rainwater and store it for the dry season. if this conservation area is damaged, then when it rains with a large intensity, the water will flow directly downstream, this coupled with the relatively flat civil and environmental science journal vol. 4, no. 2, pp. 183-191, 2021 190 slope conditions of the area will cause a large potential for flooding so that it can damage the existing ecotourism facilities downstream. and the recreation zone is intended for environmental-based tourism that can be done to increase the economic potential of bindu river ecotourism and as a tourist location for city people who are tired of daily routines but there is no recreation area in the middle of the city. 4. conclusions based on the results of the study, it can be concluded several things as follows. 1) bindu river is a tourist attraction that has the potential as a place of recreation for children, teenagers, parents, and families. the bindu river provides buoys, tires, and canoes for playing facilities in the waters of the bindu river tourist attraction. bindu river also provides several outdoor fitness facilities, several children's play facilities, and a neatly arranged garden. apart from the potential offered by the bindu river, there are still problems that exist in the bindu river including river water which has a lot of sediment, the lack of public awareness to care about the surrounding environment, and the lack of exposure by the public makes only the surrounding community know. 2) based on the delineation and the existing potential, the bindu river ecotourism area is divided into a conservation zone and a recreation zone. for the conservation zone, it can be developed into several more zones in the upstream part, it can be developed into a zone for the development of the function of protecting water resources, a zone for the development of the function of protecting flora and fauna as well as limited recreational functions. while the recreation zone can also be developed into several more zones. the upstream recreation zone can be developed into a recreational function development zone and the downstream recreation zone can be developed into an educational function development zone. acknowledgements the authors express gratitude to the acknowledgments submitted to warmadewa university who have supported the completion of this paper and all parties who helped the completion of this paper. references [1] d. widodo, b. lupiyanto, r., dan wijaya, “pengelolaan kawasan sungai code berbasis masyarakat,” j. sains dan teknol. lingkung., vol. 2, no. 1, 2010. [2] d. s. ida ayu made and luh putu kirana pratiwi, “strategy for ecotourism development in efforts to improve community welfare in ayung river flow (case study of bindu river ecotourism, kesiman village, denpasar city),” seas (sustainable environ. agric. sci., vol. 5, no. 1, pp. 1–6, 2021, doi: 10.22225/seas.5.1.3143.1-6. [3] h. hartoyo and u. supardi, membedah pengelolaan administrasi pbb dan bphtb. jakarta: mitra wacana media, 2010. [4] c. birawa and r. m. sukarna, “zonasi ekowisata kawasan konservasi pesisir di kecamatan katingan kuala, kabupaten katingan, provinsi kalimantan tengah melalui pendekatan ekologi bentang lahan,” j. ilmu kehutan., vol. 10, no. 19–32, 2016. [5] h. aliani, s. babaie kafaky, a. saffari, and s. m. monavari, “land evaluation for ecotourism development—an integrated approach based on fuzzy, wlc, and anp methods,” int. j. environ. sci. technol., vol. 14, no. 9, pp. 1999–2008, 2017, doi: 10.1007/s13762-017-12915. [6] f. hajizadeh, m. poshidehro, and e. yousefi, “scenario-based capability evaluation of ecotourism development–an integrated approach based on wlc, and fuzzy–owa methods,” asia pacific j. tour. res., vol. 25, no. 6, pp. 627–640, 2020, doi: 10.1080/10941665.2020.1752752. [7] suparno, “zonasi wilayah pesisir dan pulau kecil sebagai salah satu dokumen penting untuk disusun pemerintah daerah provinsi/kabupaten/kota,” j. mangrove dan pesisir, vol. 11, no. 1, pp. 1–8, 2009. civil and environmental science journal vol. 4, no. 2, pp. 183-191, 2021 191 [8] suardi, “problematika penerapan prinsip sustainable development dalam pengelolaan lingkungan hidup dan implikasinya terhadap pemenuhan ham,” j. ilmu huk., vol. 8, no. 4, pp. 614–628, 2014. [9] d. astanin, “functional zoning of ecological tourism areas by degree of regulation of building and planning activities,” e3s web conf., vol. 138, 2019, doi: 10.1051/e3sconf/201913801013. [10] s. r. sutcliffe and m. l. barnes, “the role of shark ecotourism in conservation behaviour: evidence from hawaii,” mar. policy, vol. 97, no. august, pp. 27–33, 2018, doi: 10.1016/j.marpol.2018.08.022. [11] p. a. quezada-sarmiento, j. del c. macas-romero, c. roman, and j. c. martin, “a body of knowledge representation model of ecotourism products in southeastern ecuador,” heliyon, vol. 4, no. 12, 2018, doi: 10.1016/j.heliyon.2018.e01063. [12] s. snyman, “the role of private sector ecotourism in local socio-economic development in southern africa,” j. ecotourism, vol. 16, no. 3, pp. 247–268, 2017, doi: 10.1080/14724049.2016.1226318. open access proceedings journal of physics: conference series civil and environmental science journal vol. i, no. 02, pp. 070-079, 2018 70 potential use of aquatic plants in constructed wetlands for simultaneous removal of phosphate and cod from laundry wastewater marcorio a tefa1, donny harisuseno1, riyanto haribowo1 1water resources engineering department, universitas brawijaya, malang, 65145, indonesia riyanto_haribowo@ub.ac.id received 27-07-2018; revised 01-09-2018; accepted 26-09-2018 abstract. one component of household wastewater that has a bad impact on the environment is waste that comes from washing which uses detergent, due to a fairly high phosphate and chemical oxygen demand (cod) concentration. the purpose of this study was to determine the potential of using aquatic plants to reduce phosphate and cod levels from laundry waste. this research was carried out using constructed wetlands model of laboratory scale using the combination of flow types of subsurface flow systems (sfs) and the type of vertical flow system (vfs) with a waste residence time of 5 days and 10 days. based on the results, for model i, the average percentage of cod levels reduction is 67.62% and phosphate is 13.89%, while in model ii, the average percentage of cod reduction is 59.93% and phosphate is 14.36%, after 10 days of waste residence time. aquatic plants used in the modeling of constructed wetland can grow and reproduce well, this can be indicated by the growth of new shoots and flowers of these plants. keywords: constructed wetland, cod, detergent waste, phosphate 1. introduction as a cleaning material, detergent is a product of technological advances that utilize chemicals containing phosfat, silicate, coloring agents and fragrance ingredients [1]. around the 1960s, early generation detergents emerged using alkyl benzene sulfonate (abs) surface-activating chemicals (surfactants) which were able to produce foam [2]. in many countries in the world the use of abs has been banned because of its nature which is difficult to describe by microorganisms on the surface of the land, but in indonesia the regulations regarding the use of abs has not been clearly implemented. some reasons for the use of abs in detergent products among others the cheap price, the stability in the form of cream/pasta and the abundant foam [3]. detergents containing abs is a relatively harsh detergents, because it is included in the non-biodegradable or difficult to decomposed by microorganisms. in addition to surfactants, important ingredients in detergent content is builders. builders function to increase the efficiency of washing from surfactants by deactivating minerals that cause water hardness. the most used builders in detergents is phosphate [4, 6, 7]. civil and environmental science journal vol. i, no. 02, pp. 070-079, 2018 71 currently, a simpler alternative waste treatment has been developed, namely an artificial wetland system by utilizing sunlight and plants that function to filter out pollutants with the help of microorganisms that grow in roots without adding chemicals and the process goes naturally [5]. this method is easy to implement and safe to use with a relatively small negative impact and does not require large costs. wetlands proved to be able to reduce levels of biological oxygen demand (bod), cod, total suspended solids (tss), nitrogen (n) and phosphate (p), and also coli bacteria significantly [8, 9]. there are several ways that can be done to treat wastewater. natural biological processing is one of the alternative processing that does not require high costs, namely by utilizing aquatic plants, wherein the content of organic material that is available will be used as nutrients in the metabolic process by aquatic plants [10, 11, 16]. aquatic plants have the ability to absorb nutrients which are pollutants (organic and inorganic) from wastewater, for their metabolic purposes. the use of aquatic plants to treat wastewater using a constructed wetland system utilizes the symbiosis between soil microorganisms and the roots of aquatic plants that will release oxygen. microbes contained in wastewater will use oxygen to decompose organic matter, so that in this process mutual symbiosis occurs in two living creatures in this wastewater treatment. in this study, the aquatic plants used were sagittaria montevidensis (water lilies) and canna sp (kana) [12, 13]. from this study, it is expected to found out how the differences between the effectiveness of constructed wetland using sagittaria montevidensis (water lilies) and constructed wetlands using canna sp (kana) plants, to reduce cod and phosphate levels in detergent waste, and how physical changes occur in aquatic plants. 2. material and methods 2.1. wetland modeling design the research was conducted in laboratory of water and land, department of water resources engineering, faculty of engineering, universitas brawijaya. waste water used in modeling is detergent waste water (domestic waste), which is tested first in the laboratory before being modeled on constructed wetland. constructed wetlands are modeled with plastic container tanks with dimensions: length = 60 cm; width = 35 cm; and height = 55 cm (figure 1). the selection of container tanks with these dimensions is based on constructed wetland design criteria, namely: a) detention time design parameters using type flow of sub surface flow between 5-10 days. b) the water depth parameters for construction range from 0.1 to 1.0 m. c) the type of plant used has the length of root zone between 15 61 cm and this type of plant can be used in wetland planning with free surface and sub surface flow types. the test plants used were sagittaria montevidensis (water lilies) and canna sp (kana). conditioning is carried out for 2 weeks, during which time the plant is considered able to adapt to its new media. acclimatization is carried out by gradually being replaced with existing wastewater for 2 weeks. the replacement of ordinary water with waste water is by adding waste water and reducing the volume of the water until the waste water reaches 100%. after the specified time, a healthy test plant is planted into the test reactor. the taking of the test plant from the acclimatization site must be with the soil so as not to damage the root of the plant, then removed from the roots of the plant by immersing it in water while removing the soil attached to the roots. if the roots are clean, plants can be planted on wetland media with a depth of 10 cm from the base. this study uses 2 models of constructed wetland: 1. model i the pool is filled with the vegetation of the sagittaria montevidensis plant combined with filter media, namely soil, sand, gravel, with the planned composition and volume. then flowed with detergent wastewater from washing result manually. the processing zone is filled with soil civil and environmental science journal vol. i, no. 02, pp. 070-079, 2018 72 substrate = 0.0263 m3; sand = 0.0175 m3; gravel = 0.0086 m3, and sagittaria montevidensis plant. filter media in the form of soil, sand and gravel are arranged in a plastic container, which is bounded by a wire screen, according to the size and volume planned. 2. model ii the arrangement, size and volume of the filter media are the same as in the design of constructed wetland model i. the basic difference in this model is the type of plant, which is using canna sp (kana), with the aim to be compared with model i. figure 1. modeling design of constructed wetland (side view). this type of flow applied to the constructed wetland modeling is the vertical flow system (vfs) flow type. modeling is divided into 3 zones, namely inlet zone, processing zone (wetland), and outlet. the inlet and outlet zones are filled with small to medium sized gravels, with the aim of avoiding the blocking so that the flow can run smoothly. in the processing zone, it is filled with aquatic plants and substrate/filter media in the form of sand and soil. waste water is flowed into the system, with the smallest possible discharge, so that the detention/ residence time of the waste in the constructed wetland is longer. this process is carried out for 10 days for each model. determination of 10 days assumes that with this time it is considered sufficient to observe the efficiency of the reduction of waste pollutants. 2.2. parameter testing chemical parameter testing is carried out per 5 days, whereas analysis of the changes that occur in plants is carried out after 10 days of waste residence/ detention time. after that, 3 (three) repetitions were carried out on each model, by replacing the plants and substrate/filter media. this is intended to determine the validity of the results obtained in previous studies. the sequence of parameter testing is: measurement of cod, measurement of phosphate [14] and analysis of plant changes. 2.3. data analysis the data obtained is used as a basis to conduct an analysis which refers to the literature study. data presentation in the form of tabulations and graphs, so that from the changes in the numbers of each parameter can describe the efficiency of processing system with the constructed wetland. percentage of reduction (%) = ( ) % 100 x c 0 10 c c− where: c0 = initial parameter concentration c1 = parameter concentration on the reactor effluent cmcm cmc m c m c m c m c m c m 5 inlet 10 50 10 tanaman air pasir 1 0 1 tanah outlet 3 1 5 3 0 sekat kawat 2 5 wire divider aquatic plants sand soil civil and environmental science journal vol. i, no. 02, pp. 070-079, 2018 73 the reduction percentage of each reactor is presented in the form of graphs and tables so that it can be seen the magnitude of the decrease in each parameter [15]. 3. result and discussion 3.1. cod parameters reduction based on testing in the laboratory, obtained the initial sample results from the parameters of cod and phosphate in detergent wastewater, namely 752 mg/l and 42.56 mg/l. the amount of the initial sample number of the cod and phosphate parameters in detergent wastewater is included in the "strong" category for the characteristics of indonesian domestic wastewater. thus, it is necessary to treat the wastewater, to reduce the levels of cod and phosphate contained therein. figure 2. cod parameter changes in model i figure 3. cod parameter changes in model ii changes that occur are cod levels have decreased after going through the processing/ treatment process in constructed wetland modeling on model i, with a residence time of 5 days and 10 days, from 3 repetitions (figure 2). for the 5-day residence time, the largest decrease in cod levels in the third experiment, namely equal to 332 mg/l from the initial sample of 752 mg/l or experiencing a civil and environmental science journal vol. i, no. 02, pp. 070-079, 2018 74 decrease in percentage of 44.15%. for the 10-day residence time, the biggest decrease in cod levels was in the second experiment, which was 520 mg/l from the initial sample of 752 mg/l or experienced a decrease in percentage of 69.15%. cod levels have decreased, both for 5 days and 10 days, from each experiment (figure 3). for the 5-day residence time, the biggest decrease in cod levels was in the second experiment, namely equal to 272 mg/l from the initial sample of 752 mg/l or experienced a decrease in percentage of 36.17%. for the 10-day residence time, the biggest decrease in cod levels was in the third experiment, namely as much as 460 mg/l from the initial sample of 752 mg/l or experienced a decrease in percentage of 61.17%. from both treatments it can be concluded that the longer the contact time of wastewater with filtration media and plants used in the modeling of constructed wetland, the more optimal the absorption process of cod levels in the wastewater. 3.2. phosphate parameters reduction phosphate levels decreased, both for 5 days and 10 days, from each experiment (figure 4). for a 5day residence time, there was the same decrease in phosphate levels from the three trials, namely equal to 2.95 mg/l from the initial sample of 42.56 mg/l or experienced a decrease in percentage of 6.93%. for the 10-day residence time, the largest reduction in phosphate levels was at the first trial, which was 7.09 mg/l from the initial sample of 42.56 mg/l or experiencing a decrease in percentage of 16.66%. figure 4. phosphate parameters change in model i figure 5 describes the change in phosphate parameters in model ii, from the initial sample of 42.56 mg/l. phosphate levels have decreased after going through the processing/treatment process in constructed wetland modeling in model ii, with a residence time of 5 days and 10 days, from 3 times the repetition process. for a 5-day residence time, the greatest decrease in phosphate levels in the first and second trials, ie equal to 4,14 mg/l from the initial sample of 42.56 mg/l or experiencing a decrease in percentage of 9.73%. for the 10-day residence time, the largest decrease in phosphate levels was in the second experiment, namely equal to 6.5 mg/l from the initial sample of 42.56 mg/l or experienced a decrease in percentage of 15.27%. similar to cod concentration, the longer the contact time of wastewater with filtration media and plants used in modeling constructed wetland, the more optimal the absorption process of phosphate levels in the wastewater. civil and environmental science journal vol. i, no. 02, pp. 070-079, 2018 75 figure 5. phosphate parameters change in model ii from the results of the research obtained, it can be concluded that both constructed wetland modeling succeeded in reducing the levels of cod and phosphate in detergent wastewater, both for the waste residence/detention time of 5 days and 10 days for three repetitions. although, it can be seen that there are differences in the results of the parameters of each trial/experiment (3 repetitions). differences in numbers and percentage of decline that occur from each experiment, due to the initial sample parameters cod and phosphate from detergent waste water measured and used as a comparison only in the initial drainage. this causes, it is very possible that there is a difference in the levels of cod and phosphate from detergent wastewater used for subsequent drainage. but by looking at the difference in numbers and the percentage of decline that is not too large from each experiment, the results of this study can be said to be valid after going through the process of three repetitions. 3.3. comparison of the decreases in cod and phosphate levels constructed wetland modeling in this study consists of two models. each model uses the same substrate/filter media (gravel, sand and soil), with sagittaria montevidensis (model i) aquatic plants and canna sp (model ii) aquatic plants. therefore, with the differences in the use of aquatic plants in this study, it is intended as a comparison to determine the extent of the difference in the decrease in cod and phosphate levels in detergent wastewater from both constructed wetland modeling. 3.3.1. cod level from the results of laboratory tests, it can be seen that the difference in cod levels occurred in the modeling of constructed wetland model i and model ii from each experiment (3 repetitions). from the analysis results (figure 6) it can be seen that, the decrease in cod levels for the 5-day residence time in model i was greater than the model ii. the biggest difference in the decline occurred in the third experiment, namely the difference in the percentage of reduction equal to 14.89%. while the difference in the average percentage of decrease in each experiment (3 repetitions) of the two constructed wetland modeling models is 9.13%. for the 10-day waste detention time, the same as for the 5-day waste residence time, the decrease in cod levels in model i was also greater than in model ii. the biggest difference in the decline of the two models occurred in the second experiment, with a difference in the reduction percentage equal to 10.64%. while the difference in the average percentage of reduction in each experiment (3 times repetition) of the two constructed wetland modeling models is 7.69% (figure 7). thus, it can be concluded that modeling of constructed wetland model i using sagittaria montevidensis aquatic plants is better in reducing cod levels in detergent wastewater, when compared with the modeling of civil and environmental science journal vol. i, no. 02, pp. 070-079, 2018 76 constructed wetland model ii that uses canna sp aquatic plants, although the comparison is not too large. figure 6. comparison of laboratory test results of cod parameters for 5 days figure 7. comparison of laboratory test results of cod parameters for 10 days 3.3.2. phosphate levels from the results of laboratory tests, it can be seen that the difference in phosphate levels occurs in the modeling of constructed wetland model i and model ii from each experiment (3 repetitions). the decrease in phosphate levels for the 5-day residence time in model ii is greater than model i. the biggest difference in the decline occurred in the first and second experiments, namely the difference in the percentage reduction equal to 2.8%. whereas in the third experiment, the difference in the percentage of decline was smaller, namely 1.39%. thus, the difference in the average percentage of decrease in each experiment (3 times repetition) from the two models of constructed wetland modeling equal to 2.33% (figure 8). for a 10-day residence time, there is a comparison of the phosphate parameter reduction which varies from both constructed wetland modeling on the three conducted experiments. in the first experiment, the decline that occurred in model i was greater, namely by the difference in the reduction percentage 2.77%. but in the second and third trials, the decline that occurred in model ii was greater, namely by the difference in the reduction percentage 2.77% in the second experiment and 1.39% in the civil and environmental science journal vol. i, no. 02, pp. 070-079, 2018 77 third experiment. the average percentage of reduction from each experiment (3 repetitions) in model ii was also greater, namely by the difference in the reduction percentage 0.47% (figure 9). figure 8. comparison of laboratory test results of phosphate parameter for 5 days therefore, based on the difference in the average percentage of decline that occurs, it can be concluded that the modeling of constructed wetland model ii which uses canna sp aquatic plant, is better in reducing phosphate levels in detergent wastewater, when compared to the modeling of constructed wetland model i that uses sagittaria montevidensis aquatic plants, although the ratio is very small. in general, the percentage of reduction in cod parameters is greater than the percentage of reduction in phosphate parameters. the residence time of the waste is very influential on the reduction of the tested parameters level, the longer the residence time, the greater the decrease that occurs. the percentage of reduction in cod parameters in model i was greater than the percentage of reduction in cod parameters in model ii, both for the waste residence time of 5 days and 10 days, with a difference in the percentage of reduction 67.62% and 59.93%. the percentage of reduction in phosphate parameters in model ii was greater than the percentage of reduction in phosphate parameters in model i, both for waste time of 5 days and 10 days, with a difference in the percentage of reduction 6.93% and 9.26%. figure 9. comparison of laboratory test results of phosphate parameter for 10 day civil and environmental science journal vol. i, no. 02, pp. 070-079, 2018 78 3.4. changes in plant growth the growth of both aquatic plants used in the installation of constructed wetland modeling can reproduce well. this can be indicated by the growth of new shoots on plants and flowers from these plants during the wastewater treatment process up to the last observation (figure 10). aquatic plants used can reproduce properly because the nutrient requirements in detergent wastewater treatment plants are sufficiently available such as phosphate ions dissolved in wastewater which is then tied first by the soil. the ph and temperature conditions in the constructed wetland modeling are relatively normal, which allows the chemical process to support photosynthesis of sagittaria montevidensis and canna sp plants to run normally. figure 10. shoots and flowers on aquatic plants 4. conclusions from the results of laboratory tests and calculations, both constructed wetland modeling models have been proven able to reduce the levels of cod and phosphate in detergent wastewater. the effectiveness of constructed wetland using sagittaria montevidensis plant (model i) is better in reducing cod levels, while for canna sp (model ii) it is more effective in reducing phosphate levels in detergent wastewater. aquatic plants used in constructed wetland modeling can grow and reproduce well, this can be indicated by the growth of new shoots and flowers from these plants during the wastewater treatment process up to the last observation. for optimal conditions, constructed wetland modeling should be done in an open area, where plants used in constructed wetland modeling can make direct contact with sunlight, so that the photosynthesis process can be maximized, in conjunction with the absorption of nutrients contained in the modeling processing zone. in the future, further research will be carried out by considering the stability of the inlet discharge, the variation of waste residence time, the arrangement of the substrate/filter media and the use of other aquatic plants. references [1] alan w. maki, donald b. porcella, richard h. wendt, 1984. the impact of detergent phosphorus bans on receiving water quality. water research, volume 18, issue 7, 1984, pages 893-903. [2] agustin n. m. bagyo, winarti andayani, christina tri suhani, 2014. radiolysis of alkyl benzene sulfonat (abs) in aqueous solution. radiation physics and chemistry, volume 69, issue 4, march 2004, pages 317-319. [3] anggraheni, e. 2004. studi tentang aerasi pada instalasi pengolahan air mikro untuk memenuhi kebutuhan air bersih rumah tangga. skripsi s1. teknik pengairan. universitas civil and environmental science journal vol. i, no. 02, pp. 070-079, 2018 79 brawijaya. malang. [4] kusuma, r.t., 2005. studi penurunan cod dan bod5 air limbah domestik dengan menggunakan subsurface constructed wetland dengan menggunakan tanaman kana-studi kasus di kampus teknik lingkungan its. tugas akhir, jurusan teknik lingkungan its, surabaya. [5] yuanita, c. 2003. pengaruh variasi media tanaman terhadap penurunan kandungan organic (pv) dan tss pada pengolahan efluen iplt keputih, sukolilo surabaya dengan menggunakan tanaman cattail (typha latifolia) menggunakan system constructed wetlands. tugas akhir jurusan teknik lingkungan its. surabaya. [6] riyanto haribowo, minami yoshimura, masahiko sekine, tsuyoshi imai, koichi yamamoto, takaya higuchi, ariyo kanno., 2017. behavior of toxicity in river basins dominated by residential areas. contemporary engineering sciences 10 (7), 305-315. [7] h yamashita, r haribowo, m sekine, n oda, a kanno, y shimono, w shitao, t higuchi, t imai, k yamamoto., 2012. toxicity test using medaka (oryzias latipes) early fry and concentrated sample water as an index of aquatic habitat condition. environmental science and pollution research 19 (7), 2581-2594. [8] zhao zhimiao, song xinshan, wang yuhui, wang daoyuan, wang suyan,he yuan, ding yi, wang wei, yan denghua, wang junfeng., 2016. effects of algal ponds on vertical flow constructed wetlands underdifferent sewage application techniques. ecological engineering 93 (2016) 120–128. [9] jih ming chyan, chien jung lin, yu chi lin, yi an chou., 2016. improving removal performance of pollutants by artificial aerationand flow rectification in free water surface constructed wetland. international biodeterioration & biodegradation, volume 113, september 2016, pages 146-154. [10] huaqing liu, zhen hu, jian zhang, huu hao ngo, wenshan guo, shuang liang, jinlin fan,shaoyong lu, haiming wu., 2016. optimizations on supply and distribution of dissolved oxygenin constructed wetlands: a review. bioresource technology, volume 214, august 2016, pages 797-805. [11] demin zhou, hong zhang, chengliang liu., 2016.wetland ecohydrology and its challenges. ecohydrology & hydrobiology 16 (2016) 26–32. [12] robert l knight, william e walton, george f o’meara, william k reisen, roland wass., 2003. strategies for effective mosquito control in constructed treatment wetlands. ecological engineering, volume 21, issues 4–5, 31 december 2003, pages 211-232. [13] c. ramprasad, chris shirley smith, fayyaz a. memon, ligy philip ., 2017. removal of chemical and microbial contaminants from greywater using a novel constructed wetland: grow. ecological engineering, volume 106, part a, september 2017, pages 55-65. [14] wilfred w. scott., 1920. standard methods of chemical analysis. d. van nostrand company. [15] cooper, p., 1999. wetland system for water pollution control. wath scie pergamon. germany. [16] r haribowo, v dermawan, sn yudha., 2018. application of artificial neural network for defining the water quality in the river. civil and environmental science journal 1 (01), 12-18, 2018. open access proceedings journal of physics: conference series civil and environmental science journal vol. 4, no. 2, pp. 106-114, 2021 106 mapping of groundwater flow pattern and its quality index based on microbiological parameters in klojen district, malang city, east java, indonesia veronika yulia permata1, hari siswoyo1, riyanto haribowo1 1department of water resources engineering, faculty of engineering, universitas brawijaya, malang, 65145, east java, indonesia veronikayuliapermata@gmail.com1 received 22-03-2021; accepted 26-04-2021 abstract. groundwater is one source of fulfilling water needs for the klojen district, the most populous district in malang city. population density affects the condition of groundwater quality because it causes pollution. the possibility of groundwater quality contamination can be identified by mapping the flow pattern and determining the quality level according to its use as drinking water. the purpose of this study is to map the groundwater quality index according to its flow pattern. flow patterns based on groundwater-surface contours can indicate the direction of flow and the direction of pollution. the quality of groundwater according to its use as drinking water was identified using the weighted arithmetic water quality index (wawqi) method. based on the research results, the research location's flow pattern generally flows from north to south. according to the flow pattern, groundwater quality is getting worse, as indicated by an increase in the index value. keywords: flow pattern, groundwater, mapping, water quality 1. introduction klojen district is one of the districts in malang city with 8.83 km2 and 101,410 people, making it the most densely populated district. the family's drinking water source in klojen district comes from 4156 protected wells, but only 1180 wells meet the requirements [1]. population density affects the number of sources of pollutants that affect water quality conditions and can cause various diseases, including diarrhea. in 2016, klojen district found 2986 cases of diarrhea disease [1]. today, water pollution is increasing, accompanied by rapid industrial development, which causes clean water on earth to become unbalanced [2]. the possibility of groundwater quality contamination can be identified by mapping the flow pattern and identifying the quality level according to its use as drinking water. groundwater flow patterns can indicate the direction of flow from one area to another. the determination of groundwater flow patterns is based on groundwater contour, a relationship line from 1 cite this as: permata, v. y., siswoyo, h., & haribowo, r. (2021). mapping of groundwater flow pattern and its quality index based on microbiological parameters in klojen district, malang city, east java, indonesia. civil and environmental science journal (civense), 4(2), 106-114. doi: https://doi.org/10.21776/ub.civense.2021.00402.1 civil and environmental science journal vol. 4, no. 2, pp. 106-114, 2021 107 places with the same water level. determination of the contour lines of the groundwater table was carried out by using the linear interpolation method. the direction of groundwater flow is determined by cutting the contour line perpendicularly (90˚) from the high contour to the lower contour [3]. according to its use, the identification of groundwater quality as drinking water can be done using the weighted arithmetic water quality index (wawqi) method. this method has the advantage that the number of parameters used is less than all water quality parameters for a particular use and can explain groundwater suitability for human consumption [4]. this methodical approach is based on the three most common factors, that is: (1) selection of parameters that have a significant impact on water quality; (2) determining the sub-index for each parameter that changes the non-dimensional scale value of the different unit variables; (3) aggregation of sub-indices via arithmetic mean [4]. this method has been used in several studies by previous researchers in many other countries to identify groundwater quality [5,6,7,8,9,10]. each previous study used different water quality parameters and guidelines. the guidelines used are following the standards of the country where each study is located. in this study, the guidelines used are based on permenkes ri no. 492/2010 [11], and the parameters used are parameters whose presence affects the amount of microbiology in the water. the purpose of this research is to map the index of groundwater quality according to its flow pattern. this study's results are expected to provide information to government agencies and the community in their efforts to deal with groundwater pollution. figure 1. location of the study area. civil and environmental science journal vol. 4, no. 2, pp. 106-114, 2021 108 2. materials and methods 2.1. materials 2.1.1. study location. the location of the study is in klojen district, malang city. the groundwater wells studied were 12 wells, which are the points with the highest and lowest groundwater levels of each flow path (figure 1). 2.1.2. data and equipment. the data used in this study include: (1) map of indonesia's earth; (2) well location coordinates; (3) the elevation of the soil surface in the well; (4) groundwater samples. map of the earth of indonesia at a scale of 1: 25000 obtained from the geospatial information agency website, which is used to determine the research location's boundaries. the coordinates of the resident wells are determined using the global positioning system (gps) of the garmin 73 gps model. the groundwater level is obtained by measuring the difference between the well walls' height and the water surface's depth using a roll meter. the material used in this study is a sample of water from a resident's well. water sampling was carried out on september 28-30, 2020. the equipment used to conduct this research included: digital thermometer tp 3001 model for measuring water temperature, ph meter model ph02 to measure the degree of acidity of water, tds meter model tds testers 139 for measures total dissolved solids in water (tds). the groundwater sample was taken using a 1-litre polyethylene bottle container and then put in a styrofoam box. the groundwater samples were then tested in the laboratory to identify the do, bod, cod, turbidity, total coliform, and escherichia coli content. 2.2. methods 2.2.1. groundwater flow pattern mapping. the initial step taken was a preliminary survey to determine the location of the dug wells belonging to the residents and measure the groundwater level. the coordinates of the well location and ground elevation were obtained using gps. the measurement of the well water surface from the well's edge was carried out using a raffia rope and measured with a roll meter. the calculation to get the groundwater level is based on the following equation [12]: groundwater′surface elevation = ground elevation + h – p (1) where: h = height of the well wall (m) p = depth of well water (m) after obtaining the groundwater level elevation based on equation 1, mapping is carried out to obtain a groundwater flow pattern map. earth map digitized to obtain a well distribution map. the well coordinate data and groundwater level elevation were then processed with the surfer 13 computer program and integrated with the research location's boundary map to produce a groundwater flow pattern map. 2.2.2. groundwater quality analysis. groundwater sampling is carried out at the part with the highest and lowest elevations of each flow path. groundwater sampling was carried out at 12 points evenly distributed throughout the research location and was carried out based on the indonesian national standard (sni) 6989.58: 2008 section 58: groundwater sampling methods. groundwater samples were taken from wells with a volume of 1 litre. the groundwater sample container used is made of polyethylene. temperature, ph, and tds parameters were measured directly in the field because these parameters change quickly with the surrounding environmental conditions. parameters of bod, cod, do, turbidity, total coliform, and escherichia coli were tested at the laboratory of perum jasa tirta i malang. bod parameters were tested using the apha 5210 b-1998 method, cod parameters were tested using the electrometric method, do parameters were tested using the spectrometric method, the civil and environmental science journal vol. 4, no. 2, pp. 106-114, 2021 109 turbidity parameters were tested using the turbid metric method, the microbiological parameters (total coliform and escherichia coli) were tested using the double tube method. the results of the content of various parameters that have been measured and tested are then analyzed. analysis of the groundwater quality index's value was carried out using the weighted arithmetic water quality index (wawqi) method. the quality standard used refers to the minister of health regulation no. 492 of 2010 concerning drinking water quality requirements. the steps for calculating the wawqi method are as follows [5]: 𝐾 = 1/ [∑ 1 𝑣𝑠 𝑛 𝑛=1 ] (2) 𝑊 = 𝐾 𝑣𝑠 [∑ 1 𝑣𝑠 𝑛 𝑛=1 ] (3) 𝑞 = (𝑣𝑎−𝑣𝑖) (𝑣𝑠−𝑣𝑖) × 100 [∑ 1 𝑣𝑠 𝑛 𝑛=1 ] (4) 𝑊𝑄𝐼 = 𝐴𝑛𝑡𝑖𝑙𝑜𝑔 (∑ 𝑊𝑛 log 𝑞𝑛𝑛𝑛=1 ) [∑ 1 𝑣𝑠 𝑛 𝑛=1 ] (5) where: w = weighting factor k = constat proportionality q = quality rating va = laboratory test value vi = ideal value of each water quality parameter (for ph = 7, for other parameters = 0) vs = standard value of each water quality parameter wqi = water quality index the rating of water quality according to this wqi is given in table 1 [5]. table 1. class classification based on wawqi wqi value rating of water quality grading 0 25 excellent a 26 50 good b 51 75 poor c 76 100 very poor d >100 unsuitable for drinking purpose e the groundwater quality index value was then mapped using the surfer 13 computer program and integrated with the flow pattern map to produce a map. the groundwater flow path, integrated with the quality index value is used to determine the relationship between the two and determine pollution movement. in calculating the water quality index value using the weighted arithmetic water quality index method, the coliform and escherichia coli parameters cannot be included in the formula because indonesia has a standard value for this parameter 0. dividing by 0 results in an undefined value. do, bod, and cod parameters also cannot be used in the analysis of water quality index values because they are not included in the parameters of drinking water quality requirements according to the indonesian minister of health regulation no. 492/2010. the parameters used in calculating the index value are ph, temperature, tds, and turbidity. the parameters used in calculating the index value are then analyzed for their correlation with other parameters (do, cod, bod, total coliform, and escherichia coli). the formula for the linear correlation coefficient (r) is as follows: civil and environmental science journal vol. 4, no. 2, pp. 106-114, 2021 110 𝑟 = ∑ (𝑥𝑖−𝑥) ⦁ (𝑦𝑖−𝑦) 𝑛 𝑖=1 √[∑ (𝑥𝑖−𝑥) 2𝑛 𝑖=1 ]⦁[∑ (𝑦−𝑦) 2𝑛 𝑖=1 ] (6) where: ¯x = mean of xi ¯y = mean of yi n = the amount of data from the x and y variable pairs the correlation test was carried out having two hypotheses to determine the correlation. the hypothesis h0 is the correlation coefficient of 0, or there is no correlation between the two things being compared. hypothesis h1 is that the correlation coefficient is not equal to 0 or a possible correlation between the two. hypothesis testing is done by calculating the t value with the following formula: 𝑡 = |𝑟| × √𝑛−2 √1−𝑟2 (7) the t count value is compared with the critical value of tcr from the table for degrees of freedom v = n-2 and α (level of significance) = 5%. if t < tcr, then h0 is accepted; otherwise, h0 is rejected [13]. figure 2. groundwater flow pattern map 3. results and discussion a groundwater flow pattern map is generated based on the depiction of groundwater-surface contours (figure 2). based on the flow pattern map that has been produced, groundwater flows from high elevation to low. there are two paths flow from the north to the south, namely the kl3 kd3 path and civil and environmental science journal vol. 4, no. 2, pp. 106-114, 2021 111 the o2 kd3 path; one path that flows from the north west to the southeast, namely the p1 p2 p3 s2 path; one path that flows from the southwest to the northeast, namely the rc2 rc1 path; one path that flows from the north to the southeast, namely the gk1 b1 b2 path; one path that flows from the north to the southwest, namely the k1 ka2 ka1 ka4 ka3 path; one path which flows from the northwest to the east, namely the k1 su1 path. according to the groundwater level contour, the groundwater flow pattern in klojen district generally flows from north to south. based on the resulting groundwater flow pattern, groundwater sampling was then carried out at 12 wells points. groundwater quality with temperature, tds and ph parameters is measured directly in the field using a digital thermometer, tds meter and ph meter. the parameters included in calculating the water quality index value are ph, temperature, tds, and turbidity. the results of the calculation of the water quality index value are tabulated in table 2. table 2. results of water quality index value calculation no. well code urban village wqi rating 1 p1 penanggungan 53.14 poor 2 kl3 klojen 50.66 good 3 ka3 kasin 71.97 poor 4 o2 oro oro dowo 68.88 poor 5 s2 samaan 60.03 poor 6 rc2 rampal celaket 57.76 poor 7 rc1 rampal celaket 50.24 good 8 kd3 kidul dalem 58.80 poor 9 su1 sukoharjo 56.64 poor 10 b2 bareng 54.37 poor 11 k1 kauman 36.02 good 12 gk1 gading kasri 54.34 poor the index value of groundwater quality for drinking water with ph, temperature, tds, and turbidity at the study site ranged from 36.02 to 71.97, which are in two categories: good quality (26-50) and poor (51-75). based on the groundwater quality index value, the three urban villages with “good” quality include klojen, rampal celaket southern area, and kauman. meanwhile, nine urban villages with “poor” quality include penanggungan, kasin, oro-oro dowo, samaan, rampal celaket northern area, kidul dalem, sukoharjo, bareng, and gading kasri. groundwater with “poor” quality means that it is of poor quality but can still be used for drinking water is only recommended. the best water quality index value is in the k1 well in kauman urban village, which is 36.02 or the quality level of "good" and the only well that has a ph value according to the quality standard of 6.734 or is very close to neutral. the turbidity value of well k1 is 1.1 ntu, indicating that the water in the well is clear. the ph and turbidity values are very influential in calculating water quality index values because they have a considerable weight. the distribution of the water quality index values according to the flow path is depicted in figure 3. the decline in water quality occurred on path 1 that connecting wells p1 p2 p3 s2, marked by an increase in the index value (from 53.14 to 60.03). similar conditions also occur on path 3 connecting wells gk1 b1 b2 with an increase in the index value from 53.34 to 54.37. the index value of paths 1 and 3 are still in the same classification class, namely “poor” quality. a very significant decrease in water quality occurred on paths 5 and 6. it was indicated by an increase in the water quality index value on these paths. path 5 connects the wells k1 ka2 ka1 ka4 ka3, flowing from the north to the southwest. as shown in figure 3, the area with a high groundwater level, civil and environmental science journal vol. 4, no. 2, pp. 106-114, 2021 112 namely k1 well is included in the “good” category (index value 36.02) and the area with a low groundwater level, namely ka3 well is included in the “poor” category (value index 71.97). similar conditions also occur on path 6, which connects wells k1 su1 and flows from the northwest to the east. the area with a high groundwater level, namely k1, is included in the “good” category (index value 36.02) and the part of the area with a low groundwater level, namely su1 well, is included in the “poor” category (index value 56.64). decreasing water quality also occurs on path 4, which connects kl3 kd3 that flow from north to south. the area with high groundwater level, namely kl3 is included in the “good” category (index value 50.66) and the area with a low groundwater level, namely kd3 well, is included in the “poor” category (index value 58.80). figure 3. distribution map of groundwater quality index an increase in groundwater quality, marked by a decrease in the water quality index’s value, occurred on path 2. path 2 connecting rc2 rc1 flowing from the southwest to the northeast experienced a decrease in the value of the water quality index, namely from the “poor” category (index value 57.76) becomes “good” (index value 50.24). this condition also occurs on path 7, which connects wells o2 kd3 with an index value of 68.99 to 58.88 so that they are still in the same classification class, namely “poor” quality. the presence or absence of bacteria determines the quality of water for drinking water or human consumption. based on permenkes ri no. 492/2010, microbiological content should not be present in drinking water. the microbiological conditions at the study sites are shown in figure 4. the lowest microbiological content was in the rc2 well (total coliform 7 mpn/100ml and escherichia coli 4 mpn/100ml), which had excellent environmental conditions because it was far from pollutant sources and separated from the toilet. the disposal of liquid waste in the rc2 well is 50 meters civil and environmental science journal vol. 4, no. 2, pp. 106-114, 2021 113 away. meanwhile, the highest microbiological content was in the o2 well (total coliform 265 mpn/100ml and escherichia coli 84 mpn/100ml). the o2 well as poor environmental conditions because it is 1 meter near the toilet, 20 meters away from the septic tank, and is in a densely populated settlement. the mismatch between the water quality index's value and the amount of microbiology occurred in kauman urban village (well k1). k1 had the lowest index of 36.02 and the highest amount of microbiology of 349 mpn/100ml. the liquid waste from the house is discharged directly into the river without being accommodated by the septic tank, the distance between the well and the pollutant source is only 10 meters. microbiology is much influenced by the concentration of hydrogen with an optimum ph of 6.0 8.0 [14]. the ph value in the k1 well is 6.734, allowing growth and microbiological development in the well, but this ph value is a good condition if intended as drinking water. considering that ph is the parameter with the most significant weight in assessing the water quality index, the index value results are also good. to reduce the amount of microbiology necessary to carry out a drinking water treatment process by heating or boiling. figure 4. distribution map of microbiological parameters the water quality index value then tested for correlation with other parameters (do, bod, cod, total coliform, and escherichia coli. this correlation is to determine the closeness of the relationship between these parameters. table 3. correlation test analysis simple correlation test r t count t table h0 water quality index value do 0.496 1.807 2.23 accepted bod -0.195 0.627 accepted cod 0.479 1.725 accepted total coliform 0.104 0.330 accepted escherichia coli 0.026 0.083 accepted analysis of the correlation between the value of the water quality index and other parameters resulted in the conclusion that no correlation or relationship influenced each other. this conclusion is obtained from testing the significance to test the hypothesis, which is done by comparing the values of t tables civil and environmental science journal vol. 4, no. 2, pp. 106-114, 2021 114 and t arithmetic. if the t table is smaller than the t count, then the hypothesis is accepted because the t count value is in the receiving area, so there is no relationship between the index value and all other parameters. 4. conclusions the groundwater flow pattern in the research location generally flows from the northern part (penanggungan urban village), which has the highest groundwater level (+485.9 m asl) to the south (kasin urban village) with the lowest groundwater level (+426.2 m asl). the groundwater quality in the study location based on its flow pattern from north to south is getting worse. groundwater quality decrease can be shown based on the wqi value and the content of microbiological parameters, wherein the northernmost area (penanggungan urban village), the wqi value is 53.14 with a microbiological amount of 151 mpn/100ml (consisting of 84 mpn/100ml coliform and 67 mpn/100ml escherichia coli), while in the south area (kasin urban village) the wqi value was 71.97 with a microbiological number of 349 mpn/100ml (consisting of 265 mpn/100ml coliform and 84 mpn/100ml escherichia coli). to prevent groundwater contamination, government agencies conduct regular quality monitoring and the community limits activities that can make the high risk of groundwater contamination. references [1] a. t. r. nuswantari, buku putih sanitasi kota malang tahun 2014. malang, pemerintah kota malang, 2014. [2] r. haribowo, m, yoshimura, m, sekine, k, yamamoto, t, higuchi, a, kanno, “behavior of toxicity in river basins dominated by residential areas”. contemporary engineering sciences, 10(7), pp. 305-315, 2017. [3] adji, nugroho, dan santosa., karakteristik akuifer dan potensi airtanah graben bantul, gajah mada university press, 2014. [4] t. shweta, s. bhavtosh, s. prashat, d. rajendra., “water quality assessment in terms of water quality index”, american journal of water resources vol. 1 no. 3: 34 -38, 2013. [5] s. kumar, “assessment of ground water quality using water quality index”, international journal of innovative research in advanced engineering, issue 3, vol. 2, 2015. [6] s. harsan et al, “assessment of water quality index of groundwater quality in chunnakam and jaffna town, sri lanka”, vingnanam journal of science 13:1-2, 2017. [7] d. chandra., s. satist., s. asadi., and s. raju., “estimation of water quality index by weighted arithmetic water quality index method: a model study”, international journal of civil engineering and technology 8.4: 1215-1222, 2017. [8] ewaid, sallam, hussein, and s. abed., “water quality index for al-gharraf river, southern iraq”, the egyptian journal of aquatic research 43.2 : 117-122, 2017. [9] panday et al, “assessment of water quality of river narmada using water guality index (wqi)”, iaetsd journal for advandce research in applied science vol. 5, 2018. [10] h. siswoyo., d. rifki., “pemetaan pola aliran dan indeks kualitas air tanah di kecamatan tanggulangin kabupaten sidoarjo”, jurnal mahasiswa jurusan teknik pengairan 2.1: 7, 2018. [11] peraturan menteri kesehatan republik indonesia, persyaratan kualitas air minum no 492 tahun 2010., jakarta: percetakan negara, 2010. [12] e. a. amah, m. a. agbebia, “determination of groundwater flow direction in ekintae limestone quarry near mfamosing, south-eastern, nigeria,” international journal of geology, agriculture and environmental sciences., vol – 3, issue – 6, december 2015. [13] l. montarcih, statistika hidrologi terapan untuk teknik pengairan. malang: penerbit citra, 2014. [14] mudatsir, “faktor – faktor yang mempengaruhi kehidupan mikroba dalam air”, jurnal kedokteran syiah kuala, vol.7, no.1, 2007. open access proceedings journal of physics: conference series civil and environmental science journal vol. 05, no. 02, pp. 159-170, 2022 159 effect of variation of mixture (wood gelam+rice husk) on biopellet on the value of temperature, rate, and pressure of combustion rachmat subagyo1, andy nugraha1, hajar isworo2, trendy pratama1, m. zainul rusdi1 1mechanical engineering department, universitas lambung mangkurat, banjarbaru, 70714, indonesia 2 mechanical engineering department, politala, pelaihari, tanah laut, indonesia rachmatsubagyo@ulm.ac.id, hajarisworo@politala.ac.id, andynugraha@ulm.ac.id received 02-07-2022; accepted 15-07-2022 abstract. the increasing demand for energy causes the depletion of fossil fuels. to overcome this, it is necessary to utilize biomass and biomass waste. this study aimed to simulate the effect of bio-pellet density on the temperature, rate, and pressure of combustion made from a mixture of gelam wood and rice husk. the method uses ansys simulation with a literature review. the results showed that the increasing composition of rice husks affected the decreasing combustion rate. it was due to the calorific value of the pellets making up the material, where the lower calorific value of rice husk affects the combustion rate. pellets with a large density affect the combustion rate, extending the burning time. the pressure of pellet molding influences the density of pellets; the greater the pressure makes the fuel denser and denser. the highest combustion air pressure occurs at 100% gelam composition and the lowest at 100% husk composition. it shows that adding rice husk composition reduces the combustion pressure, and vice versa applies to adding gelam composition. keywords: biomass waste, bio-pellet, gelam wood, rice husk, combustion rate 1. introduction the increasing demand for energy causes the depletion of fossil fuels. to overcome this, it is necessary to utilize biomass and biomass waste as alternative fuels [1]. along with the development of renewable energy, the demands for innovation are increasing to maximize the potential for utilizing energy derived from nature for alternative energy. one of these alternative energies, namely wood pellets [2]. wood pellets are an alternative energy source from biomass. pellets are obtained from sawdust, shavings, and wood chips [3]. apart from that, wood pellets can be mixed with rice straws, husks, leaf litter, twigs, or plant parts that are considered waste [4]. in addition, wood pellets can be an alternative energy source for electrical energy because they can save fossil fuels whose numbers are dwindling [5]. mailto:rachmatsubagyo@ulm.ac.id mailto:hajarisworo@politala.ac.id civil and environmental science journal vol. 05, no. 02, pp. 159-170, 2022 160 the advantage of wood pellets compared to other wood fuels, such as wood chips, is that they have a higher calorific value of 4.3 million cal/ton, while wood chips have a calorific value of 3.4 million cal/ton [6]. another advantage of wood pellets compared to wood chips is that wood pellets have a higher price [7]. the most abundant plant in south kalimantan, gelam wood, with the potential for wood production in 2006, was 55,745.78 m3. data from the forestry service of south kalimantan province notes that the potential for gelam production in barito kuala regency per year reaches 20,000 m3, making the district the largest producer of gelam in south kalimantan. kayu gelam, or melaleuca cajuputi is a species that grows naturally in swamp forests and is found abundantly in peat swamp forests of south kalimantan [8]. gelam wood has high specific gravity and has the potential to be used as raw material for charcoal and wood pellets [9]. the demand for wood pellets from year to year always increases, driven by policies to reduce greenhouse gas emissions and increase the use of renewable energy [10]. there is an imbalance between the production and consumption of wood pellets to meet demand. it can be added to waste from rice straws, husks, leaf waste, twigs, or plant parts which are considered waste [11]. currently, the utilization of rice husk waste is still very small. rice husk waste, in general, will be burned by farmers who create pollutants in the air and can interfere with public health [12]. on the other hand, rice husk, often seen as agricultural waste, has great potential to be used as biomass energy [13]. the biomass produced by rice husks can produce solid biofuels such as pellets [14]. husk as biomass can be used for various needs such as industrial raw materials, animal feed, and fuel [15]. for example, in the rice milling process, usually about 20% 30% of husks can be obtained, bran between 8% 12%, and milled rice between 50% 63.5% of the weight of the grain [16]. the largest rice production area in south kalimantan is barito kuala (batola) regency. barito kuala (batola) regency is an area that has an area of 3,284 kilometers with the capital city marabahan, is one of the regencies in south kalimantan province where most of the people work as farmers or are engaged in the agricultural sector. barito kuala regency has the largest harvested area and rice production in south kalimantan (kalsel). data from the central statistics agency (bps) of south kalimantan province using the area sample framework (ksa) method, batola regency has a harvested area of 66,995 hectares. from the harvested area, batola regency became the largest contributor to rice production, reaching 263,000 tons more dry-milled unhulled rice (gkg) from january to september 2018. the abundance of rice production will certainly contribute to the abundance of rice husks. the abundant availability of rice husks and gelam wood in batola regency makes the potential for their use as raw material for rice husk wood pellets very large [17]. the combination of gelam wood and rice husks into wood pellets can be done because pellets derived from husks have a calorific value of 3090.64 – 4049.05 cal/g [18]. in addition, the pressure in the molding can also affect the physical properties and combustion characteristics [1]. so that by varying the pellet molding pressure, it is expected to obtain wood pellets of rice husk with the best physical properties and combustion characteristics. more in-depth research is needed to find out the characteristics of wood pellets from gelam-rice husk wood [19]. the topics raised in this study are in line with the research master plan (rip) of lambung mangkurat university in the leading fields of wetlands and the leading topics of energy security, advanced materials, and infrastructure. the resulting gelam-rice husk pellets can be directed to applying applicable research results and play a role in providing alternative energy options to replace fossil fuels [20]. the combustion temperature of the pellet also affects the structure and changes the chemical composition and structure of the pellet [21]. according to [22], the combustion efficiency and emission performance of cfb bio pellets were tested using 2-dimensional cfb combustion modeling. the model efficiently simulates the results associated with excess air value, which is the verified main parameter. the oc combustion efficiency changes between 82.25 and 98.66% due to excess air, increasing from 10 to 116% with a maximum error of about 8.59%. the efficiency of rice husk civil and environmental science journal vol. 05, no. 02, pp. 159-170, 2022 161 burning changed between 98.05 and 97.56% as the operating speed increased from 1.2 to 1.5 m/s with a maximum error of about 7.60%. co and nox emissions increase with increasing carbon and operating speed [23]. increased excess air results in slightly higher levels of nox emissions. many combustion products occur in the upper zone due to high volatility. the temperature variations in the burning of rice husk pellets can affect the combustion properties, decrease the water content, and increase the ash content [20]. previous studies that only discussed rice husks did not use a mixture of other materials, such as galam wood. the effect of solids on the speed and temperature of combustion in a mixture of galam wood and rice husks has not been discussed. this study aims to simulate the effect of the density of bio pellets on the speed and temperature of combustion made from a mixture of galam wood and rice husks. 2. material and methods 2.1. material wood pellet is a material made from wood that is compacted so that the fuel can burn for a long time. wood pellets can also be used as alternative energy for home or industrial scale. this wood pellet is made from wood waste or parts with no economic value. so the manufacture of wood pellets can increase the selling value of this wood waste. this wood pellet has enormous potential in the industrial sector because it can be used as alternative or renewable energy that can replace current conventional materials. gelam is a plant that is tolerant of extreme land conditions such as acidity and high salinity [24]. gelam wood is hardwood with a specific gravity of 0.85, durable class iii and strong class ii. gelam wood is used for boats, building construction, poles, bridges, and energy wood [25] and can potentially be developed as a raw material for wood pellets and as a producer of high-quality liquid smoke [26]. wood pellets made from gelam wood can produce a calorific value of 4100 cal/g [27]. as a raw material for wood pellets, gelam wood can be combined with biomass, such as rice husks. rice husk is a karyolytic hard layer material consisting of two interconnected parts, namely the lemma and palea. rice husk results from the rice milling process, where the rice grains are separated from the husks. the husk is often called waste, so this material can be used to become biomass. rice husk has physical properties, which include a density of 122 kg/m3 and silica burning ash of 86.9097.30% [28]. in south kalimantan, the potential for rice husk waste is very large and has the potential to be used as fossil fuels in the form of solid fuels. it should mention the time and place of research in the first part. all materials and methods that used such chemicals for analysis, treatment, and experimental design must be stated clearly and briefly. state the objectives of the work and provide an adequate background, avoiding a detailed literature survey or a summary of the results. a theory section should extend, not repeat, the background to the article already dealt with in the introduction and lays the foundation for further work. a calculation section represents a practical development from a theoretical basis. 2.2. methods this research method uses ansys simulation by searching for temperature, rate, and combustion pressure variables. the formulas used in this simulation are obtained from combustion formulas that are commonly used. the percentage of gelam and husk mixture is determined as shown in table 1. the fuel density is the ratio between the mass of the fuel and its volume. the density of fuel affects the length of combustion time [29]; the higher the density of a material, the longer the combustion process. for the calculation of the density of the mixture, it is shown in table 1. the wood and husk thermal conductivity values are 0.21 [30] and 0.071 [14], respectively. civil and environmental science journal vol. 05, no. 02, pp. 159-170, 2022 162 table 1. density of mixture gelam and rice husk no. gelam percentage (%) rice husk percentage (%) the density of the mixture (kg/m3) rated thermal conductivity of wood (w/m k) husk thermal conductivity value (w/m k) 1. 100 0 1159.67 0.12 0.071 2. 80 20 978.65 3. 60 40 797.62 4. 50 50 707.11 5. 0 100 254.56 solid fuel combustion has several characteristics, namely: combustion rate, combustion temperature, and combustion pressure. the burning rate is the amount of wood pellet mass lost in a certain time interval. higher combustion temperatures can increase the reaction rate and cause shorter combustion times. the combustion rate is calculated as follows: burning rate = burning pellet mass burning time ( gr detik ) (1) the wood pellet burning temperature is the temperature that occurs during the wood pellet burning process. the temperature of the wood pellet will continue to rise and reach its maximum point along with the number of parts of the wood pellet that are burned and will decrease along with the number of parts of the wood pellet that becomes ash. thermal conductivity: 𝑄 = 𝑚 𝑥 𝐶𝑝 𝑥 ∆𝑇 (2) with δt= t1-t0 where: t1 = combustion temperature (k) δt = difference in combustion temperature-initial temperature (k) t0 = initial temperature (k) that, combustion temperature (t1)= 𝑄 𝑚𝑐𝑝 + 𝑇0 (3) ideal gas equation: 𝑃2 𝑃1 = ( 𝑉1 𝑉2 ) 𝑘 (4) combustion pressure is the pressure that occurs on wood pellets as a result of the ongoing combustion process. combustion pressure is strongly influenced by the material being burned and the temperature that occurs during the combustion process. combustion pressure: 𝑃2 𝑃1 = ( 𝑉1 𝑉2 ) 𝑘 (5) where: p1 = initial pressure (atm) p2 = pressure after combustion (atm) v1 = initial volume (m 3) v2 = volume after combustion (m 3) 3. result and discussion the combustion process generates heat which in turn raises the combustion temperature. when a mixture of gelam and rice husks is pelletized, then pressed and glued using an adhesive, the combustion temperature is almost the same, as shown in figure 1. in addition, the pressure in pellet molding can also affect the physical properties and combustion characteristics [1]. so that by varying civil and environmental science journal vol. 05, no. 02, pp. 159-170, 2022 163 the pellet molding pressure, we get wood pellets with the best physical properties and combustion characteristics [19]. the advantage of pellet formation on two materials is that they can provide mutual benefits and cover the weaknesses of the two materials. the calorific value of low rice husks will increase when subjected to the process of pressing and adding adhesive so that the value of the combustion temperature increases. figure 1. graph of burning temperature of wood pellets for rice husks the difference in combustion temperature between gelam and husk 100% when the pellet is formed is only about ±1 k as shown in figure 1. it can be concluded that the combustion temperature value is stable. making pellets is very significant to increase the calorific value of combustion of mixed materials that have a low calorific value such as rice husks. pellet raw materials can be taken from useless materials such as gelam waste and rice husk waste which are widely available around us. gelam wood has a calorific value of 4100 cal/g [28] and rice husks of 3300 cal/g [32]. the addition of the percentage of gelam does not increase the combustion temperature as well as the addition of the percentage of rice husks; this is very beneficial when considering the lower calorific value of rice husks. likewise, the thermal conductivity value also does not affect the combustion temperature because the thermal conductivity value in gelam is much higher when compared to rice husks, as shown in figure 1. figure 2. graph of the burning rate of wood pellets for rice husks 270 275 280 285 290 295 300 305 1 2 3 4 5c o m b u st io n t e m p e r a tu r e ( k ) gelam wood pellet composition+rice husk (%) pellet composition (1. gelam 100%), (2. gelam 80%: husk 20%), (3. gelam 60%: husk 40%), (4. gelam 50%: husk 50%) dan (5.husk 100%). 0 50 100 150 200 250 300 350 1 2 3 4 5 b u r n in g r a te ( m /s ) gelam wood pellet composition + rice husk (%) pellet composition (1. gelam 100%), (2. gelam 80%: husk 20%), (3. gelam 60%: husk 40%), (4. gelam 50%: husk 50%) dan (5. husk 100%). civil and environmental science journal vol. 05, no. 02, pp. 159-170, 2022 164 figure 2 shows the relationship between variations in the mixture of gelam and husks in the composition (0-100%), where the gelam composition (100%) has the largest combustion rate value, and the burning rate decreases when the amount of rice husks increases. when the composition of rice husks increases until it reaches 100%, the value of the combustion rate decreases; this is influenced by the calorific value of the pellets making up the material. the calorific value of rice husk, which is lower than the calorific value of gelam wood, affects the combustion rate. in addition, other factors that affect the rate of pellet combustion include particle size, air flow velocity, temperature, type of fuel, pressure, oxygen concentration, and the nature of the elementary reactions that occur [28]. figure 3. graph of the combustion pressure of the wood-husk wood pellets the pellet combustion pressure in the composition variations shows different values, as shown in figure 3. the 100% gelam composition value has the highest pressure value, which decreases with increasing husk composition in the pellet composition. the high combustion pressure is caused by the high calorific value of the fuel. combustion pressure is also influenced by grain size and pressure of wood pellet printing because it will affect the rate and direction of air flow used in the wood pellet burning process. the high combustion pressure also indicates the more complete the combustion process that occurs. (a) (b) 0 10000 20000 30000 40000 50000 60000 70000 1 2 3 4 5 c o m b u st io n p r e ss u r e (p a ) gelam wood pellet composition+ rice husk (%) pellet composition (1. gelam 100%), (2. gelam 80%: husk 20%), (3. gelam 60%: husk 40%), (4. gelam 50%: husk 50%) dan (5. husk 100%). civil and environmental science journal vol. 05, no. 02, pp. 159-170, 2022 165 (c) (d) (e) figure 4. the results of the ansys simulation of pellet combustion temperature in the variation of the mixture (gelam wood + rice husk): (a). 100% gelam composition, (b). gelam composition 80%: rice husk 20%, (c). 60% gelam composition: 40% husk, (d) 50% gelam composition: 50% husk and (e). 100% husk composition the pellet combustion process is influenced by the composition of the ingredients that make it up. in this study, two materials were used, namely gelam wood and rice husk, which have different properties. the pellet combustion temperature in the mixed composition (0-100%) is shown in figure 4. the appearance of the simulation results shows the dominance of different colors in the composition of 100% gelam (green), 80% gelam (yellow), 60% gelam (red), gelam 50% (green), and gelam 0% (blue). in this simulation, the combustion temperature is relatively the same; the value is not different. a good combustion temperature is a homogeneous temperature on the entire surface of the pellet, where the ignition process starts from the highest temperature on the pellet's surface. then the temperature propagates to the closest area, until all the pellets are burned out. there is a difference in figure 4(a-d) in the composition of 100-50% gelam; it appears the appearance of a red color (circle mark); this indicates the gelam powder gives a combustion effect with a higher heating value. the decrease in gelam in the pellet mixture indicates a decrease in calorific value, as shown in figure 4(e). the size of the flame affects the rate of the combustion process, where the larger the flame causes the fuel to run out faster. a good flame is if the fuel has a large combustion rate and can last longer. the simulation results show that in the 100% gelam mixture, figure 5(a) circle marks, the flame is quite good with the best burning rate, followed by the 80-60% composition, figure 5(a,b,c). in the 050% dark mixture condition, figure 5(d,e) circle marks, the fire appears to be getting bigger, indicating the pellet burns faster so that the fuel runs out quickly. in this process, pellets that have a large density affect the rate of pellet combustion, thereby prolonging the burning time. the pressure of pellet molding influences the density of pellets; the greater the pressure, the denser the fuel and the greater the density. civil and environmental science journal vol. 05, no. 02, pp. 159-170, 2022 166 (a) (b) (c) (d) (e) figure 5. the results of the ansys simulation of the burning pellet rate in the variation of the mixture (gelam wood + rice husk): (a). 100% gelam composition, (b). gelam composition 80%: rice husk 20%, (c). 60% gelam composition: 40% husk, (d) 50% glam composition: 50% husk and (e). 100% husk composition combustion pressure affects the stability of the combustion process and combustion temperature [33], where the more evenly the combustion pressure, the better the combustion process. the effect of pressure on the combustion temperature is that when the air pressure is higher, the combustion temperature produced is more maximal. the simulation results show that the highest combustion air pressure occurs at 100% gelam composition (6.a) and the lowest at 100% husk composition (6.e). it shows that the addition of rice husk composition reduces the combustion pressure. it appears in the gelam composition of 100-60% (5a,b,c) the combustion pressure is high at the ends of the pellet (circle sign) in contrast to the case of 50-0% gelam composition (circle sign) the combustion pressure at the pellet tip begins to decrease (circle sign). the pressure on the 0% gelam pellet (5e) is the lowest (circle civil and environmental science journal vol. 05, no. 02, pp. 159-170, 2022 167 sign) so that on the pellet with 0%, the stability of the combustion process is disturbed so that the flame becomes unstable. (a) (b) (c) (d) (e) figure 6. simulation results of ansys combustion pressure on the variation of the mixture (gelam wood + rice husk): (a). 100% gelam composition, (b). gelam composition 80%: rice husk 20%, (c). 60% gelam composition: 40% husk, (d) 50% glam composition: 50% husk and (e). 100% husk composition 4. conclusions the results of this study indicate: the addition of the percentage of gelam does not increase the combustion temperature as well as the addition of the percentage of rice husks; this is very beneficial when considering the lower calorific value of rice husks. in the increasing composition of rice husks, the combustion rate decreases; this is influenced by the calorific value of the pellets making up the material. where the lower calorific value of rice husk affects the rate of combustion. pellets with a large density affect the rate of pellet burning, thereby prolonging the burning time. the density of pellets is affected by the pressure of pellet molding; the greater the pressure makes the fuel denser and civil and environmental science journal vol. 05, no. 02, pp. 159-170, 2022 168 large density. the highest combustion air pressure occurs at 100% gelam composition and the lowest at 100% husk composition. it shows that adding rice husk composition reduces the combustion pressure and vice versa applies to adding gelam composition. acknowledgments lambung mangkurat university's acknowledgment for funding this research with the dipa university budget scheme for the fiscal year 2022 number: sp dipa023.17.2.677518/2022 dated 17 november 2021. following the decree of the chancellor of lambung mangkurat university no: 458/un8/pg /2022, march 28, 2022. references [1] amrullah, a., syarief, a., & saifudin, m. (2020). combustion behavior of fuel briquettes made from ulin wood and gelam wood residues. international journal of engineering, transactions b: applications, 33(11), 2365–2371. https://doi.org/10.5829/ije.2020.33.11b.27. [2] rima riyanti, ulinnuha latifa, y. s. (2021). multitek indonesia : jurnal ilmiah. 6223(january), 121–130. [3] schipfer, f., kranzl, l., olsson, o., & lamers, p. (2020). the european wood pellets for heating market price developments, trade and market efficiency. energy, 212, 118636. https://doi.org/10.1016/j.energy.2020.118636. [4] vera, i., goosen, n., batidzirai, b., hoefnagels, r., & van der hilst, f. (2022). bioenergy potential from invasive alien plants: environmental and socio-economic impacts in eastern cape, south africa. biomass and bioenergy, 158(january), 106340. [5] siwale, w., frodeson, s., berghel, j., henriksson, g., finell, m., arshadi, m., & jonsson, c. (2022). influence on off-gassing during storage of scots pine wood pellets produced from sawdust with different extractive contents. biomass and bioenergy, 156(december 2021), 106325. https://doi.org/10.1016/j.biombioe.2021.106325 [6] arsad, e. (2014). sifat fisik dan kimia wood pellet dari limbah industri perkayuan sebagai sumber energi alternatif (carakteristic physical and chemistry of wood pellet from industrial disposal of wood as sources energy alternatif). jurnal riset industri hasil hutan, 6(1), 1–8. [7] sylviani, & suryandari, e. y. (2013). potensi pengembangan industri pelet kayu sebagai bahan bakar terbarukan studi kasus di kabupaten wonosobo (potential development of wood pellets as renewable fuel, case study of wonosobo district). penelitian sosial ekonomi kehutanan, 10(4), 235–246. [8] girsang, m. a. p. (2019). analisa karakteristik bahan bakar alternatif biopelet dari serbuk kayu dan sekam padi terhadap lama waktu pembakaran. 1–18. [9] zadravec, t., rajh, b., kokalj, f., & samec, n. (2022). the impact of secondary air boundary conditions on cfd results in small-scale wood pellet combustion. fuel, 324(pa), 124451. https://doi.org/10.1016/j.fuel.2022.124451 [10] winaya, i. s., sujana, i. g., & tenaya, i. (2010). formasi gas buang pada pembakaran fludized bed sekam padi. jurnal energi dan manufaktur, 4(1), 2–6. [11] sidabutar, v. t. p. (2018). kajian peningkatan potensi ekspor pelet kayu indonesia sebagai sumber energi biomassa yang terbarukan. jurnal ilmu kehutanan, 12(1), 99. https://doi.org/10.22146/jik.34125 [12] umrisu, m. l., pingak, r. k., & johannes, a. z. (2018). pengaruh komposisi sekam padi terhadap parameter fisis briket tempurung kelapa. jurnal fisika : fisika sains dan aplikasinya, 3(1), 37–42. https://doi.org/10.35508/fisa.v3i1.592 [13] ulfa, d., lusyiani, l., & a.r. thamrin, g. (2021). kualitas biopellet limbah sekam padi (oryza sativa) sebagai salah satu solusi dalam menghadapi krisis energi. jurnal hutan tropis, 9(2), 412. https://doi.org/10.20527/jht.v9i2.11293 [14] ciptaningtyas, drupadi; suhardiyanto, h. (2016). ifat hermo isik rang ekam. sifat thermo-fisik civil and environmental science journal vol. 05, no. 02, pp. 159-170, 2022 169 arang sekam, 10(2), 1–6. [15] bandara, j. c., jaiswal, r., nielsen, h. k., moldestad, b. m. e., & eikeland, m. s. (2021). air gasification of wood chips, wood pellets and grass pellets in a bubbling fluidized bed reactor. energy, 233, 121149. https://doi.org/10.1016/j.energy.2021.121149 [16] jeklin, a. (2017). jurnal ilmiah: energi & kelistrikan. sekolah tinggi teknik pln, 9(2), 1–23. [17] huang, x., hu, z., miao, z., jiang, e., & ma, x. (2020). chemical looping gasification of rice husk to produce hydrogen-rich syngas under different oxygen carrier preparation methods. international journal of hydrogen energy, 45(51), 26865–26876. https://doi.org/10.1016/j.ijhydene.2020.07.116 [18] gilvari, h., van battum, c. h. h., van dijk, s. a., de jong, w., & schott, d. l. (2021). largescale transportation and storage of wood pellets: investigation of the change in physical properties. particuology, 57, 146–156. https://doi.org/10.1016/j.partic.2020.12.006 [19] manatura, k., lu, j. h., wu, k. t., & hsu, h. te. (2017). exergy analysis on torrefied rice husk pellet in fluidized bed gasification. applied thermal engineering, 111, 1016–1024. https://doi.org/10.1016/j.applthermaleng.2016.09.135 [21] djomdi, fadimatou, h., hamadou, b., nguela, l. j. m., christophe, g., & michaud, p. (2021). improvement of thermophysical quality of biomass pellets produced from rice husks. energy conversion and management: x, 12, 100132. https://doi.org/10.1016/j.ecmx.2021.100132 [22] mian, i., li, x., dacres, o. d., wang, j., wei, b., jian, y., zhong, m., liu, j., ma, f., & rahman, n. (2020). combustion kinetics and mechanism of biomass pellet. energy, 205, 117909. https://doi.org/10.1016/j.energy.2020.117909 [23] gungor, a. (2010). simulation of emission performance and combustion efficiency in biomass fired circulating fluidized bed combustors. biomass and bioenergy, 34(4), 506–514. https://doi.org/10.1016/j.biombioe.2009.12.016 [24] saosee, p., sajjakulnukit, b., & gheewala, s. h. (2022). environmental externalities of wood pellets from fast-growing and para-rubber trees for sustainable energy production: a case in thailand. energy conversion and management: x, 14(december 2021), 100183. https://doi.org/10.1016/j.ecmx.2022.100183 [25] giesen, w. (2015). case study: melaleuca cajuputi (gelam) – a useful species and an option for paludiculture in degraded peatlands. sustainable peatlands for people & climate (sppc) project. wetlands international. p 16. [26] ramadhoni, f. (2016). penebangan marak, hutan kayu gelam di muba berkurang. sriwijaya post. [27] alpian, prayitno, t.a., sutapa, j.p.g. & budiadi. (2014). kualitas asap cair batang gelam (melaleuca sp.). jurnal penelitian hasil hutan, 32(2), 83-92. https://doi.org/10.20886/jphh.2014.32.2.83-92 [28] herry irawansyah, andy nugraha, moh noer afifudin, muhammad, & rizqi nor al’arisko. (2022). pengaruh variasi ukuran serbuk (mesh) dan persentase perekat tapioka terhadap sifat fisik pellet kayu gelam. multitek indonesia: jurnal ilmiah. volume: 15 no. 2, hal. 13 22. doi : 10.24269/mtkind.v15i2.4194 [29] dwi rasy mujiyanti, dahlena ariyani, nurul paujiah, muna lisa, & rizky pradana n.e. (2021). isolasi dan karakterisasi abu sekam padi lokal kalimantan selatan menggunakan ftir dan xrd. prosiding seminar nasional lingkungan lahan basah. volume 6 nomor 2. [30] nasukhah, awal laili yuanita and mahardhika, aditya yusuf. (2018). pengaruh massa jenis briket arang tempurung kelapa terhadap waktu pembakaran dan konversi panas menjadi listrik menggunakan thermoelectric converter (tec). sarjana thesis, universitas brawijaya. [31] i̇smail özlüsoylu, abdullah i̇stek, 2019, the effect of hybrid resin usage on thermal conductivity in ecological insulation panel production, 4th international conference on engineering technology and applied sciences (icetas) april 24-28 2019 kiev ukraine. [32] a syarief, a nugraha, m n ramadhan, fitriyadi, and g g supit. (2021). the effect of the percentage of alaban waste and rice husk waste with tapioca adhesive on the physical civil and environmental science journal vol. 05, no. 02, pp. 159-170, 2022 170 properties. iop conf. series: earth and environmental science. doi:10.1088/17551315/758/1/012019. [33] gilang wahyu ramadhan, basyirun, 2020, pengaruh tekanan udara terhadap temperatur pembakaran oli bekas pada kompor, jurnal dinamika vokasional teknik mesin 5(2):163-168 doi: 10.21831/dinamika.v5i2.34804 https://www.researchgate.net/journal/jurnal-dinamika-vokasional-teknik-mesin-2598-392x http://dx.doi.org/10.21831/dinamika.v5i2.34804 open access proceedings journal of physics: conference series civil and environmental science journal vol. 05, no. 02, pp. 118-128, 2022 118 bearing capacity of large drilled shafts fully embeded in claystone and sandstone layers muhammad an al marwaji 1, yulian firmana arifin 2,3* 1 senior geotechnical engineer, banjarmasin, indonesia. 2 engineer profesion education, university of lambung mangkurat, banjarbaru, 70714, indonesia. 3 wetland based material research center, university of lambung mangkurat, banjarmasin, 70123, indonesia. *y.arifin@ulm.ac.id received 20-04-2022; accepted 27-09-2022 abstract. this paper analyzes the bearing capacity of large-diameter drilled shafts fully embedded in the claystone and sandstone layers. the foundations used are the drilled shafts for the pulau balang bridge pylons built across the balikpapan bay. three bored pile foundations with a planned diameter of 2 meters by 60 meters were used. the bearing capacity of the foundation in the field was carried out using the osterberg cell test. the foundation's upper side's bearing capacity is 32.77, 27.26, and 114.46 mn, and the lower parts are 26.98, 27.16, and 50.25 mn, respectively. the results show that the method closest to the upper part of the oc test is the method suggested by kulhawy and phoon, with a value of c = 0.5. as for the lower part, the closest approach combines the kulhawy and phoon and the rowe and armitage methods. the kulhawy and phoon (1993) and rowe and armitage (1987) methods for the main claystone layer and the o'neil and reese (1993) and rowe and armitage (1987) methods for the main sandstone layer are the combinations of methods that come close to the total bearing capacity of the field. keywords: claystone, sandstone, drilled shaft, bearing capacity, osterberg cell test. 1. introduction analysis of the bearing capacity of the foundation of drilled shafts requires a very high cost for both the implementation and the instrumentation. thus, many formulas are made based on data from field testing results in large construction projects. researchers need to help publicize existing methods' use to get more information about how reliable and valid these methods are for a certain situation. numerous approaches have been presented for determining the bearing capacity of the shaft and foundation end. these methods consider many things, such as parameters of rock strength, rock mass stiffness, and interface roughness [1], the possibility of slip occurring at the pierrock interface under load conditions [2], and the discontinuity effect [3]. carrubba [4] says that the pile's response during axial load depends on the strength of the rock, the length of the socket in the rock layer, and the length of the shaft in the soil. some of them suggested new methods, some made modifications, and some reported the suitability of using those methods. the most common formula for conducting analysis is to match the computation with the results of field tests such as the loading test [1]–[3] and the biaxial test civil and environmental science journal vol. 05, no. 02, pp. 118-128, 2022 119 [5]. o'neil [6] states that calculating the bearing capacity of piles requires sharp knowledge of the significant geotechnical effects and construction phenomena and the performance of foundations designed in related geological formations. therefore, publishing a bearing capacity analysis is recommended, especially for massive constructions. this study uses the results of testing the bored pile foundation on the construction of the balang island bridge, connecting penajam paser utara regency, which has been decided as the new capital of indonesia, with tempadung, balikpapan municipality in east kalimantan. the balang island bridge superstructure is a twoto 402 m long stayed bridge with two pylons standing on four pile caps and 144 bored piles in total. balang island has two pile caps and two more on the tempadung side. steel pipe casings protect the top of the seabed, but the rest of the piles, all the way to the bottom, are unprotected. bored piles are installed in the sandstone and claystone layers. there are 144 bored piles in total. two pile caps are located on balang island, and two others are on the tempadung side. bored piles are designed using steel pipe casings for the top of the seabed, and the rest of the piles, up to the bottom, do not use protection. some bored piles are installed in the sandstone and claystone layers. the drill tools used were zhongrui airlift, buma airlift, and zhongrui suction, with a diameter of 1.8 m. there is no difference between the design and the actual diameter of the part mounted to the casing. however, there is an indication of a change in diameter at the bottom without the casing. the amount of concrete used in the construction process demonstrates this. necking, which results in a smaller pile diameter, and bulging, which results in a larger pile diameter, are two examples of this change in diameter. although the pile's diameter increases due to bulging, this phenomenon is still considered damage to the foundation. chan [7] reports that mixing soil material due to the collapse of the hole wall can result in a reduced pile bearing capacity. wakil and kassim [8] stated that bulging can increase the bearing capacity of the foundation even though it is still considered a defect in the pile. therefore, changes in diameter are also considered in this analysis. pile integrity tests must be carried out to ensure that no other material is mixed with concrete due to the collapse of the hole wall [7]. crosshole sonic logging (csl) is one method for checking pile integrity. this method has proven accurate and reliable for finding pile defects [9]. in this project, the same process (i.e., csl) was carried out, and no abnormalities were found in the boring pile shaft. the method commonly used to obtain the field-bearing capacity of bored piles located above the sea is the osterberg cell test (oc test), also known as the biaxial test method [10] [11]. in constructing the suramadu bridge in indonesia, this method determined how much load the large diameter borings could hold [5]. the purpose of this article is to analyze the bearing capacity of bored pile foundations using commonly used formulas. three bored piles were used, each with biaxial test instruments. changes in diameter as a result of the drilling process are also considered. 2. material and methods 2.1. geomaterial properties two deep borings with undisturbed sampling located close to the piles tested were performed, namely bh1 and bh2. the geotechnical rock properties obtained from bh1 and bh2, including unit weight, unconfined compression (qu), rock quality designation (rqd), rock mass modulus of elasticity (emass), and the ratio between rock mass and intact rock secant modulus of rock, are presented in figures 1(a), 1(b), 2(a), and 2(b), respectively. in addition, samples were taken to determine the rqd of the rock formations, which is one of the most important factors in determining the bearing capacity of the shaft. the two test points exhibit significantly different data, with bh1 demonstrating the dominant soil layer as claystone, while bh2 demonstrates the dominant soil layer as sandstone. the qu in bh1 is less than 4 mpa than the qu in bh2, reaching a value of 10 mpa. rqd is also higher on the bh2 than it is on the bh1. emass attains a pressure of 1000 mpa in bh2. the emass in bh2 is significantly larger than in bh1, reaching a peak of only 300 mpa. civil and environmental science journal vol. 05, no. 02, pp. 118-128, 2022 120 figure 1. geotechnical rock properties of bh1 figure 2. geotechnical rock properties of bh2 2.2. osterberg cell test three oc tests were performed on three piles with a diameter of 2 m, named pile1, pile2, and pile3, with a total length of 68.68 m, 68.68 m, and 53.8 m, respectively. in the implementation of oc test work, the loadcell is placed at a relatively different level for each pile tested. for example, the load cell of pile1 is located at 57.68 m from the pile head. for pile2 and pile3, loadcells are placed at a depth of 57.7 m and 44.8 m, respectively. figures 3(a) and 3(b) show the sketches of loadcell locations in the foundations for pile1, pile2, and pile3, respectively. this resulted in each loadcell receiving a load due to the overlying concrete of 2627 kn, 2626 kn, and 2040 for pile1, pile2, and pile3, respectively. loading and unloading were carried out according to astm d114381 [12] (i.e., a quick load test for individual piles) with a maximum load of 2×18,000 kn. the maximum load is determined based on the capacity that must be held by each 18000 kn pile. 0 10 20 30 40 50 60 70 0 10 20 30 d e p th ( m ) unit weight (kn/m3) claystone claystone claystone sandstone sandstone sandstone clayeysand 0 2 4 qu (mpa) 0 10 20 30 40 50 60 70 0 50 100 rqd (%) d e p th ( m ) 0 250 500 emass (mpa) 0.0 0.5 1.0 emass/ei bh-1 0 10 20 30 40 50 60 70 0 10 20 30 d e p th ( m ) unit weight (kn/m3) claystone sandstone sandstone siltyclay 0 10 20 30 qu (mpa) 0 10 20 30 40 50 60 70 0 50 100 rqd (%) d e p th ( m ) 0 2500 5000 emass (mpa) 0.0 0.5 1.0 emass/ei bh-2 civil and environmental science journal vol. 05, no. 02, pp. 118-128, 2022 121 3. results and discussions figure 4 shows the oc test results for the three foundations, which are indicated by the relationship between load and displacement. the maximum upward displacement of each pile at a load of 18000 kn is 1.7 mm, 5.67 mm, and 2.93 mm for pile1, pile2, and pile3. the maximum downward displacement for pile1, pile2, and pile3 is 3.75 mm, 6.92 mm, and 6.13 mm, respectively, at a maximum load of 18000 kn. however, the maximum load given is not the maximum load at collapse. failure load was determined based on the criteria adopted by fhwa [13], which is located at a displacement of 5% of the foundation diameter (0.05d) if the shaft plunging cannot be achieved. this criterion looks at the statistical tests that are the easiest and most reliable compared to methods like davisson, de beer, and curve shape [14]. figure 3. sketchs of pile and load cell positions pile1, pile2, and pile3 the relationship curves between load and displacement in figure 4 were fitted by the equation suggested by carubba [4]. the model is based on a hyperbolic transfer function approach (equation 1). figure 4. upward and downward displacement obtained from oc tests +3.50 -23.525 -27.525 -65.15 seabed top bored pile steel casing load cell 1 1 .0 0 m +3.40 hwl pile-1 +3.50 -23.379 -27.739 -65.18 1 1 .0 0 m pile-2 a b e d -12.99 -17.14 -50.30 seabed top bored pile steel casing load cell 9 .0 0 m +3.40 hwl pile-3 civil and environmental science journal vol. 05, no. 02, pp. 118-128, 2022 122 𝑓(𝑧) = 𝑤(𝑧) 𝑎+𝑏𝑤(𝑧) (1) where: f(z) is the mobilized resistance along a shaft portion or at the shaft base, and w(z) is the corresponding displacement. the a is the reciprocal of the initial slope parameter, and the b is the limit strength parameter. using equation 1 and the failure load at 0.05d, the oc test's bearing capacity can be found in table 1. table 1. bearing capacity of shafts predicted from oc tests data pile upward downward total 1/a 1/b qs (mn) 1/a 1/b qe *) (mn) (mn) (kn) 1 22.44 33.26 32.77 12.67 27.57 26.98 59.75 59,750 2 7.97 28.23 27.26 6.58 28.33 27.16 54.42 54,420 3 6.00 141.46 114.46 4.21 57.05 50.25 194.70 194,700 *) including side resistance of shaft under loadcell 3.1. determination of actual diameter of bored pile the actual diameter of the hole is not measured directly using a tool but is based on the volume of concrete embedded in the hole. the mean diameter is calculated using equation 2. 𝐷𝑎𝑣𝑒𝑟𝑎𝑔𝑒 = √(( ∆v ∆h ) ∗ 4 π ) (2)) wherev is the volume of the concrete inserted into the borehole, and h is the depth difference before and after the concrete is shed (after the tremie is spaced). figure 5 is an example of the average diameter calculated using equation 2. pile cap 1 and pile cap 2 (close to bh1) are located on one pylon, while pile cab 3 is located on another (close to bh2). in figure 5, d134, d169, and d235 are pile1, pile2, and pile3, respectively. generally, the shaft diameter is larger than the design diameter (i.e., 2.00 m). the biggest change occurred at the base of the pile bores, caused by water flushing. the diameter of the piles' tips in pile cab1 and 2 is greater than those in pile cab3. this is because the two pile groups are located in the claystone layer at a depth of 4050 m with qu < 2 mpa (considerably weak). the pile3 base is located on a relatively hard sandstone layer at a depth of 3540 m with a qu of 510 mpa. figure 5. calculated bore diameter (a) pile cab 1, (b) pile cab 2, and (c) pile cab 3. -65 -60 -55 -50 -45 -40 -35 -30 -25 -20 1 2 3 4 d e p th ( m ) diameter (m) d1-30 d1-31 d1-32 d1-33 d1-34 ddesign casing -65 -60 -55 -50 -45 -40 -35 -30 -25 -20 1 2 3 4 d e p th ( m ) diameter (m) d1-68 d1-69 d1-70 d1-71 d1-72 ddesign casing -50 -45 -40 -35 -30 -25 -20 -15 1 2 3 4 d e p th ( m ) diameter (m) d2-31 d2-32 d2-34 d2-35 d2-36 ddesign casing(a) (b) (c) civil and environmental science journal vol. 05, no. 02, pp. 118-128, 2022 123 3.2. bored pile bearing capacity 3.2.1. bearing capacity of the upper side of the load cell several methods have been suggested for calculating bored pile bearing capacity. one formula often used is recommended by o'neill and reese [15] (equation 3). this approach was applied by aashto and numerous other studies to determine the bearing capacity of drilled piles [10], [13], [16]. 𝑓𝑠 𝑝𝑎 = 0.65 𝑅 √ 𝑞𝑢 𝑝𝑎 (3) where: fs denotes friction resistance and pa is the atmospheric pressure of 101.3 kpa. qu is the mean value of uniaxial compressive strength for the rock layer, and e is an empirical reduction factor which is a function of the estimated ratio of rock mass modulus to the modulus of intact rock (em/er). the value depends on the rqd of the rock, as shown in table 2, and the reduction factor is obtained from table 3. table 2. modulus ratio (em/er) based on rqd (o’neill et al.) [17] rqd em/er (%) closed joint open joints 100 1.00 0.60 70 0.70 0.10 50 0.15 0.10 20 0.05 0.05 table 3. reduction faktor (r) (o’niell and reese) [15] em/er r 1.0 0.5 0.3 0.10 0.05 1.0 0.8 0.7 0.55 0.45 tables 4 and 5 illustrate the calculation process for the upper side bearing capacity component of piles1 and 2, respectively, using equation 3. the total qs obtained are 50.795 kn and 48.328 kn. using the same procedures as for pile‒3, the total qs acquired is 94.725 kn. as can be seen, the total qs obtained for piles‒1 and 2 are remarkably similar, owing to the use of the same drill data and nearly identical foundation diameters. however, the total qs of pile 3 are nearly double that of the others because it was constructed on sandstone‒dominated soil with higher qu and rqd data. table 4. bearing capacity calculation of pile1 using o’neil et al. [17] method table 5. bearing capacity calculation of pile2 using o’neil et al. [17] method williams and pells [1] suggested using the line of best fit of the  and qu data for mudstone, shale, and sandstone (equation 4). several studies have used this equation to assess the bearing capacity of bored piles [18]–[21]. a graph digitizer and a statistical analyzer were used to fit the data that can be approximated by equation 5. moreover, the  is determined using a bestfit equation, as shown in equation 6. the effect of  is negligible when the mass modulus is close to the intact modulus. williams 5.0 7.1 2.26 3.50 65 0.67 0.87 335 16,791 4.9 2.26 3.50 65 0.67 0.87 335 11,745 1.1 2.17 3.58 84 0.84 0.93 366 2,653 1.9 2.17 3.58 84 0.84 0.93 366 4,839 4.7 2.17 2.69 68 0.75 0.89 304 9,632 1.4 2.2 1.47 68 0.75 0.89 224 2,233 3.9 2.20 0.44 59 0.48 0.78 108 2,902 total 50,795 neglected qs (kn) d (m) qu (mpa) rqd (%) em/er r fs (kpa) l (m) 5.0 2.07 5.0 2.07 3.50 65 0.66 0.86 333 10,916 7.0 2.00 3.50 65 0.66 0.86 333 14,554 3.0 2.00 3.58 84 1.19 1.08 423 7,978 3.6 2.00 2.69 68 0.75 0.89 304 6,952 2.4 2.13 1.47 68 0.75 0.89 224 3,541 6.0 2.13 0.44 59 0.50 0.79 108 4,387 total 48,328 neglected qs (kn) d (m) qu (mpa) rqd (%) em/er r fs (kpa) l (m) civil and environmental science journal vol. 05, no. 02, pp. 118-128, 2022 124 and pells [1] proposed a safety factor of 2.5 to reduce the effect of scattering data to obtain . a is a reduction factor for rock socket skin friction, and  is a reduction factor for discontinuity. fs =   qu (4) 𝛼 = 0.107 + 0.351 𝑞𝑢 (5) 𝛽 = 0.043 + 0.96 ( 𝐸𝑚 𝐸𝑖 ⁄ ) 0.328 (6) however, alshenawy et al. [22], stark et al. [16], and rezazadeh and eslami [23] used an equation that kulhawy and phoon [22] came up with to get the shaft side shear that is written in equation 7. fs pa = c  qu 2pa (7) where qu is the uniaxial compressive strength, pa is atmospheric pressure equal to 101.3 kpa, and c is a dimensionless factor reflecting variations in the intact strength and roughness of the rock. sockets that are artificially roughened have a lower limit of c = 0.5, a reasonable lower limit of 1, a mean of 2, and an upper limit of 3. tables 6 and 7 summarize the example results of the two methods for calculating the friction bearing capacity of the bored pile. the results obtained are much different from the two approaches. the results are almost four times as different as the two approaches. it can be seen that kulhawy and phoon's method [22] is highly dependent on the . if the average value is used (i.e., 2), the fs obtained is 126.133 kn, which is close to that analyzed using williams and pell's approach [1]. table 6. bearing capacity calculation of pile1 using williams and pells [1] table 7. bearing capacity calculation of pile1 using kulhawy and phoon [22] 3.2.2. bearing capacity of the lower side of the load cell two components must be analyzed at the bottom side of this load cell, i.e., side friction and endbearing capacities. shaft friction is calculated by using the three methods above, i.e., o’neil et al. [17], williams and pells [1], and kulhawy and phoon [22] methods (equations 37). table 8 summarizes all the calculation results, including upper and lower part calculations. this result is consistent with the results of the previous calculation, where the bearing capacity calculated by the william method yields the highest value, followed by o’neil, and the smallest, which is analyzed by the kulhawi method. despite having the same pile lengths and calculations using the same soil data (i.e., bh1), piles‒1 and 2 have different bearing capacity values due to the difference in the installed diameter, as shown in figure 5. table 8 also shows that pile‒3 has the highest bearing capacity due to the dominant sandstone soil layer with shear strength parameters that exceed the data in piles‒1 and 2. 5.0 7.1 2.26 3.50 0.48 0.27 0.80 755 37,842 4.9 2.26 3.50 0.80 0.27 0.94 885 31,038 1.1 2.17 3.58 0.84 0.27 0.95 911 6,606 1.9 2.17 3.58 0.84 0.27 0.95 911 12,051 4.7 2.17 2.69 0.61 0.30 0.86 695 22,037 1.4 2.2 1.47 0.68 0.41 0.89 534 5,315 3.9 2.20 0.44 0.38 0.97 0.74 316 8,519 total 123,408 neglected qs (kn) d (m) qu (mpa) em/ei r  fs (kpa) l (m) 5.0 7.1 2.26 3.50 65 0.50 211 10,558 4.9 2.26 3.50 65 0.50 211 7,385 1.1 2.17 3.58 84 0.50 213 1,544 1.9 2.17 3.58 84 0.50 213 2,816 4.7 2.17 2.69 68 0.50 185 5,855 1.4 2.2 1.47 68 0.50 136 1,357 3.9 2.20 0.44 59 0.50 75 2,013 total 31,528 neglected d (m) qu (mpa) rqd (%) c fs (kpa) qs (kn) l (m) civil and environmental science journal vol. 05, no. 02, pp. 118-128, 2022 125 3.2.3. end bearing capacity end bearings are calculated using the rowe and armitage [2], aashto [13], and zhang and einstien [3] formulas. additionally, rowe and armitage [2][16] proposed an equation for determining the base shaft's maximum bearing capacity (equation 8). qe = 2.5 qu (8) where qe denotes the drilled shaft's end bearing. table 8. summary of calculation results of skin friction bored piles methods upper side (kn) lower side (kn) pile1 pile2 pile3 pile1 pile2 pile3 o’neill and reese [15] 50,795 48,328 94,725 17,014 21,424 29,456 williams and pells [1] 123,408 100,645 278,814 32,875 38,404 79,013 kulhawy and phoon [22] (c=0.5) 31,528 25,594 55,580 14,329 14,329 18,417 aashto [13] recommends calculating the end-bearing capacity using equation 9. qe=nms qu (9) where nms is a parameter related to the quality and type of rock mass. aashto [13] and zhang [24] [25] provide detailed nms values. zhang and einstein [3] [20] recommend equations to predict the end bearing capacity of drilled shafts socketed into rock based on the analytical relationship and field data tests. equations 10–13 should be used to create a foundation with a minimum embedment ratio of 3.0 [3]. lower bound: qe = 3.0 qu (10) upper bound: qe = 6.6 qu (11) mean: qe = 4.8 qu (12) table 9 summarizes the results of the end-bearing capacity analysis using equations 8–12. as can be seen from the table, the end bearing capacity calculated using the rowe and armitage [2] method yields the highest value. the remaining two, on the other hand, produce smaller values. the aashto method considers the rock rqd at the pile's tip, specified by the nms parameter. piles‒ 1 and 2 have a combined rqd of 76%, with a good quality rock mass with an nms of 0.32. meanwhile, at the end of pile‒3, the rqd is 53%, including the appropriate rock category with an nms of 0.075. this parameter significantly reduces the bearing capacity of the pile tip. the third method recommended by zhang and einstien [3][20] is based on the rock's undrained compressive strength. so, even though the coefficient number used by zhang and einstein [3] is higher than in the other two methods, the result is the smallest bearing capacity. tabel 9. end bearing capacities using zhang and einstien [3] pile rowe and armitage [2] (kn) aashto [13] (kn) zhang and einstien [3] (kn) pile‒1 13,999.09 1,659.15 787.00 pile‒2 10,258.38 1,215.81 576.71 pile‒3 61,550.28 1,709.73 1,412.64 based on the osterberg cell test result, comparisons were made with calculations using the methods of o'neill and reese [15], williams and pells [1], and kulhawy and phoon [22]. for the upper side of the loadcell, the friction bearing capacity of pile1 and pile2 implanted in claystone dominant soil (qu < 5 mpa) is very close to the results calculated by the kulhawy and phoon [22] method with c = 0.5. likewise, pile3 with a qu > 5 mpa is very close to the value of c = 1. for the upper side of the loadcell, the bearing capacity of friction pile1 and pile2 embedded in soil with claystone dominant (i.e., qu < 5 mpa) is 32.77 mpa and 27.26 mpa, respectively. these are civil and environmental science journal vol. 05, no. 02, pp. 118-128, 2022 126 very close to the results of calculations by the kulhawy and phoon [22] method with c = 0.5 (i.e., 31.528 mpa and 25.594 mpa, respectively for pile1 and pile2). for pile3 with a qu > 5 mpa, the oc test results (i.e., 114.46 mpa) are very close to the analytical results for the value of c = 1 (i.e., 111.16 mpa). the shaft bearing capacity of a pile with a qu < 5 mpa calculated by the method of o'neill and reese [15] produces 1.5–1.8 times greater than the results of the oc test. this method's calculations are closer to the bearing capacity of pile3 implanted in the dominant sandstone layer with a qu > 5 mpa. this is in line with the value suggested by o'neil [6], where the value is divided between soil and other materials at su/pa = 2.5, or about 5.06 mpa. by dividing the calculation results by a safety factor of 2.5 as williams and pells [1] suggested to reduce the scatter in the determination, the bearing capacities are 41.936 kn, 40.258 kn, and 111.526 kn for pile1, pile2, and pile3, respectively. pile3. the results of this calculation are close to the results of the oc test, but the condition of the oc test is the ultimate bearing capacity. therefore, there must be a higher safety factor (e.g., five) for both conditions when william and pells' method [1] is used. the best way to figure out how the methods work together is to add up the frictional and pile-end bearing capacities, as shown in table 10. bold values indicate those that are closest to the total field bearing capacity. the closest combination of methods for piles constructed on a claystone dominant layer is a combination of methods by kulhawy and phoon [22] and rowe and armitage [2]. this combination makes a difference of 0.18 and 7.79 percent for piles‒1 and 2, respectively. in the kulhawy and phoon [22] method, the coefficient c significantly affects the side friction piles. in this analysis, the coefficient of c used is the lower limit of 0.5. while the end bearing is the rowe and armitage [2] method, which multiplies the undrained compressive strength of rock with an empirical coefficient of 2.5. for pile-3, primarily installed on sandstone, the results of o'neill et al. [17] and rowe and armitage [2] are the closest to the field. although the bearing capacity calculated from the data and field test results is generally divided by different safety factors, the factor for the field test results (i.e., 2) is generally smaller than the analysis result (at least 2.5) based on sni 8460 [26]. therefore, these findings are still appropriate for use. table 10. the combination of methods used in this study pile‒1a pile‒2a pile‒3a pile‒1b pile‒2b pile‒3b pile‒1c pile‒2c pile‒3c pile‒1d 81,808 170,282 59,856 pile‒2d 80,010 149,307 50,181 pile‒3d 185,731 419,377 135,547 pile‒1e 69,468 157,942 47,516 pile‒2e 70,968 140,265 41,139 pile‒3e 125,891 359,537 75,707 pile‒1f 68,596 157,070 46,644 pile‒2f 70,329 139,626 40,500 pile‒3f 125,594 359,240 75,410 note: a (o’neill et al) [17], b (williams and pells) [1], c (kulhawy and phoon) [22], d (rowe and armitage) [2], e (aashto) [13], f (zhang and einstien) [3]. 4. conclusions an analysis of the bearing capacity of largediameter bored piles in claystone and sandstone layers has been presented. the following are some of the points that can be concluded: 1. in the analysis, the actual diameter of the bored pile in the field must be considered, particularly the diameter at the foundation's base. civil and environmental science journal vol. 05, no. 02, pp. 118-128, 2022 127 2. for drilled shafts installed in claystone layers with a qu < 5 mpa, the bearing capacity of pile1 and pile2 upper sides is 32.770 kn and 27.260 kn, respectively. the method closest to this calculation is the method suggested by kulhawy and phoon (1993), with a value of c = 0.5. 3. the results of the upperside foundation in the sandstone layer with a qu > 5 mpa are most closely matched by the method of o'neil and reese (1993). 4. the bearing capacity of the bored pile analyzed by the kulhawy and phoon (1993) and rowe and armitage (1987) methods, namely for the frictional and tip resistances in the claystone dominant layer, is close to that obtained from field tests. in the sandstone layer, the best ways to figure out the shaft and end bearing capacity are those suggested by o'neil and reese (1993) and rowe and armitage (1987). acknowledgements the authors would like to thank the ministry of public works and housing, especially cmo of the pulau balang bridge mr. asyfak bismoseno, for giving them information about the project. references [1] a. f. williams and p. j. n. pells, “side resistance rock sockets in sandstone, mudstone, and shale.,” can. geotech. j., vol. 18, no. 4, pp. 502–513, 1981, doi: 10.1139/t81-061. [2] r. k. rowe and h. h. armitage, “design method for drilled piers in soft rock.,” can. geotech. j., vol. 24, no. 1, pp. 126–142, 1987, doi: 10.1139/t87-011. [3] l. zhang and h. h. einstein, “end bearing capacity of drilled shafts in rock,” j. geotech. geoenvironmental eng., vol. 124, no. 7, pp. 574–584, 1998, doi: 10.1061/(asce)10900241(1998)124:7(574). [4] p. carrubba, “skin friction on large-diameter piles socketed into rock,” can. geotech. j., vol. 34, no. 2, pp. 230–240, 1997, doi: 10.1139/cgj-34-2-230. [5] m. irsyam, a. sahadewa, a. boesono, and soebagyo, “pengaruh strength reduction tanah clay-shale akibat pelaksanaan pemboran terhadap nilai daya dukung pondasi tiang di jembatan suramadu berdasarkan analisis hasil tes oc,” j. tek. sipil, vol. 14, no. 2, pp. 69– 82, 2007. [6] m. w. o’neill, “side resistance in piles and drilled shafts,” j. geotech. geoenvironmental eng., vol. 127, pp. 3–16, 2001. [7] h. c. chan, “non-destructive testing of concrete piles using the sonic echo and transient shock methods,” university of edinburgh, 1987. [8] a. z. el wakil and m. kassim, “bulging as a pile imperfection,” alexandria eng. j., vol. 49, no. 4, pp. 387–391, 2010, doi: 10.1016/j.aej.2010.07.004. [9] d. sibit and g. handayani, “the crosshole sonic logging (csl) measurement system to measure the quality of physical model of bored pile,” j. phys. conf. ser., vol. 739, no. 1, 2016, doi: 10.1088/1742-6596/739/1/012051. [10] x. yu, m. y. abu-farsakh, s. yoon, c. tsai, and z. zhang, “implementation of lrfd of drilled shafts in louisiana,” j. infrastruct. syst., vol. 18, no. 2, pp. 103–112, 2012, doi: 10.1061/(asce)is.1943-555x.0000084. [11] h. g. poulos, “tall building foundations: design methods and applications,” innov. infrastruct. solut., vol. 1, no. 1, pp. 1–51, 2016, doi: 10.1007/s41062-016-0010-2. [12] astm-d1143, “standard test method for piles under static axial compressive load,” am. soc. test. mater., vol. 4, no. 8, pp. 1–12, 2010. [13] d. a. brown, j. p. turner, and r. j. castelli, drilled shafts: construction procedures and lrfd design methods, no. fhwa nhi-10-016. new york, 2010. [14] nchrp, “load and resistance factor design (lrfd) for deep foundations,” washington d.c., 2004. [15] m. w. o’neill and l. c. reese, drilled shafts: construction procedures and design methods. fhwa-if-99-025, 1999. civil and environmental science journal vol. 05, no. 02, pp. 118-128, 2022 128 [16] l. stark t. j., assem, p, “improvement for determining the axial capacity of drilled shafts in shale in illinois,” illinois, 2013. [17] m. w. o’neill, f. c. townsand, k. m. hassan, a. buller, and p. s. chan, load transfer for drilled shafts in intermediate geomaterials. 1996. [18] a. alshenawy, w. hamid, and a. alnuaim, “skin friction behavior of pile fully embedded in limestone,” arab. j. geosci., vol. 11, no. 2, pp. 1–7, 2018, doi: 10.1007/s12517-018-3386-9. [19] s. k. martin and k. syngros, “bored pile construction challenges in highly variable limestone for a supertall building,” in international conference on deep foundations, seepage control and remediation (41st annual), 2016. [20] t. y. chin and c. c. meng, “foundation design and construction in limestone formation: a malaysian consultant’s experience,” in international symposium on advances in foundation engineering (isafe 2013), 2013. [21] e. l. juvencio, f. r. lopes, and a. l. l. s. nunes, “an evaluation of the shaft resistance of piles embedded in gneissic rock,” soils and rocks, vol. 40, no. 1, pp. 61–74, 2017. [22] a. alshenawy, w. hamid, and a. alnuaim, “skin friction behavior of pile fully embedded in limestone,” arab. j. geosci., vol. 11, no. 2, pp. 1–7, 2018, doi: 10.1007/s12517-018-3386-9. [23] s. rezazadeh and a. eslami, “empirical methods for determining shaft bearing capacity of semideep foundations socketed in rocks,” j. rock mech. geotech. eng., vol. 9, no. 6, pp. 1140–1151, 2017, doi: 10.1016/j.jrmge.2017.06.003. [24] l. zhang, drilled shafts in rock: analysis and design. leiden: a.a.balkema publishers, 2004. [25] l. zhang, “determination and applications of rock quality designation (rqd),” j. rock mech. geotech. eng., vol. 8, no. 3, pp. 389–397, 2016, doi: 10.1016/j.jrmge.2015.11.008. [26] sni8460, “standar nasional perancangan geoteknik,” badan stand. nas. indones., pp. 1–323, 2017. civil and environmental science journal vol. 05, no. 02, pp. 183-193, 2022 183 the impact of the age of the driver of freight transport on the probability of being involved in a traffic accident (case study on the krian – taman sidoarjo road) dwi risdianto1*, hera widyastuti1 1department of civil engineering, faculty of civil, planning, and geo engineering, institut teknologi sepuluh nopember, surabaya, east java, indonesia dwirisdianto06@gmail.com received 08-07-2022; accepted 27-09-2022 abstract. a traffic accident is one of the traffic problems that cause deaths, injuries, and material loss. the high number of traffic accidents indicates the low level of road traffic safety. krian – taman sidoarjo road has become one of the black site areas. according to data from the sidoarjo resort police, there have been 66 traffic accidents from 2015 to 2020. the majority of accidents involve freight transport compared to passenger transport. therefore, it is necessary to research the factors of freight transport drivers that affect the possibility of traffic accidents on the krian – taman sidoarjo road. methods of data collection using questionnaires to drivers of freight transportation. while the analytical method used is descriptive analysis and logistic regression using data from questionnaires. the research shows that the older the driver, the higher the probability of being involved in a traffic accident. keywords: freight transport, age, probability of traffic accident 1. introduction traffic accidents have become a global issue, where almost 1,35 million people die yearly, and 50 million people are seriously injured [1]. most victims who died from traffic accidents were in their teens and productive ages, that is, the age of 5 – 29 years [1]. of the number of victims of traffic accidents, 90% occur in developing countries, including indonesia. traffic accidents are the third biggest killer in indonesia after coronary heart disease and tuberculosis (tbc) [2]. according to data from the indonesian national police in 2017, an average of 3 people die every hour due to traffic accidents in indonesia. the data also states that a large number of accidents is caused by several factors, including 61% by the human factor (related to the ability and character of the driver), 9% by vehicle factors (related to meeting technical requirements and roadworthiness) and 30% by infrastructure factors and environment [3]. the human factor is the most dominant cause of traffic accidents. one of the causes that often occur is traffic violations, such as: violating road signs and markings, speeding, overloading and over-dimension, and so on. traffic accidents are events that are difficult to predict when and where they will occur. accidents do not only result in trauma, injury, or disability but also death [4]. the impacts caused by traffic accidents include deaths and injuries, material losses [5], and traffic jams. in addition, traffic jams can cause a loss of time value and waste fuel and the environment on the road [6]. civil and environmental science journal vol. 05, no. 02, pp. 183-193, 2022 184 efforts made by the government to reduce the number of traffic accidents in indonesia by launching the decade of action for road safety 2011 – 2020 and the national general plan for road safety 2011 – 2035. this program is the result of joint work between relevant agencies (ministry of transportation, ministry of public works, indonesian national police, ministry of health, ministry of national education, ministry of home affairs, ministry of industry, ministry of finance, and national planning and development agency). the national general plan for road safety is structured as government responsibility to ensure road traffic safety [7-8]. sidoarjo regency is one of the regencies located in east java province, which is directly connected to surabaya city, gresik regency, pasuruan regency, and mojokerto regency. sidoarjo is one of the main supports for surabaya city and is included in the gerbangkertosusila area. based on the sidoarjo resort police, in 2019, the fatality of the victim dying was 219 people [9]. one of the recent traffic accidents is on the krian – taman sidoarjo road, a national road connecting mojokerto regency and surabaya city, east java. traffic conditions on this road are quite congested, dominated by motorbikes and freight transport. this road is a route for trucks to transport goods from krian to surabaya and its surroundings because the land use around krian and trosobo is an industrial and warehousing area. based on data from the sidoarjo resort police, from 2015 to 2020, there were 66 traffic accidents on the krian – taman road, which resulted in 33 deaths, 19 serious injuries, and 30 minor injuries. of the 66 accidents involving freight transport, about 68 vehicles and passenger transport, 28 vehicles [10]. the high number of traffic accidents on the krian – taman road has resulted in this road being known as “the black site area”. the main problem in this study is that freight transport contributes more to traffic accidents than passenger transport. so it is necessary to improve the factors that cause it [11]. the human factor plays an important role in reducing the number of traffic accidents on the road. therefore, this research’s object is the driver of freight transport. the study aims to identify the causative factors and to know the model and the probability of traffic accidents on the krian – taman sidoarjo road. 2. material and methods this section includes procedures, procedures, or work stages used to obtain research purposes. this section aims to make research run more smoothly, systematically, and credibly. 2.1. time and location this research is conducted in the service unit of motor vehicle weighing trosobo sidoarjo. the basis of consideration is that every freight transport crossing krian – taman sidoarjo road must carry out inspections and weigh vehicles according to applicable regulations. research implementation time for several days (weekdays) during operating hours. 2.2. data collection stage this stage aims to obtain the information needed to achieve the research purposes. techniques used to collect data in this study include interviews, questionnaires, and documentation. 2.2.1. primary data. this data is obtained from interviews or direct questions and answers to respondents and filling out questionnaires through google forms. respondents are randomly taken to freight transport drivers passing through krian – taman sidoarjo road. the technique used is to reveal a preference. • number of samples the population used in the study were all freight drivers who passed on the krian – taman sidoarjo road. while taking the number of samples refers to the average daily traffic of freight transport at the service unit of motor vehicle weighing trosobo sidoarjo. in calculating the number of samples using the slovin formula. the average daily traffic of freight transport in 2020 at the service unit of motor vehicle weighing trosobo sidoarjo (n) is 3.558 [12]. error tolerance limit or margin of error (e) is 10%. so that the number of samples (n) is obtained: civil and environmental science journal vol. 05, no. 02, pp. 183-193, 2022 185 𝑛 = 𝑁 1 + 𝑁𝑒2 = 3.558 1 + 3.558 (0,1)2 = 100 𝑠𝑎𝑚𝑝𝑙𝑒𝑠 the minimum number of samples required in this study is 100 samples. however, to anticipate incomplete/ invalid respondents’ answers, 150 samples are used. 2.2.2. secondary data. this data is used to support research. these data include: 1. data on traffic accidents from 2015 to 2020 on the krian – taman sidoarjo road (police resort sidoarjo). 2. daily traffic freight transport data (service unit of motor vehicle weighing trosobo sidoarjo). 3. data of violations freight transport (service unit of motor vehicle weighing trosobo sidoarjo). 4. data of krian – taman sidoarjo road. 2.3. data analysis stage primary and secondary data from the field survey are then processed for further analysis. secondary data is used to describe the characteristics of traffic accidents on the krian – taman sidoarjo and the causal factors. at the same time, the primary data from the questionnaire results have then analyzed the characteristic of the respondents using descriptive statistics in the form of pie charts. finally, we are using logistic regression analysis to determine the model and probability of traffic accidents on the krian – taman sidoarjo road. 2.3.1. traffic accidents data analysis. this analysis will describe the causes of traffic accidents and the characteristics of traffic accidents on the krian – taman sidoarjo road. 1. analysis of traffic accidents causes the method used in the fishbone diagram. in this study, the causes of traffic accidents are divided into 4 (four), namely: human, vehicle, road, and the environment [13], as shown below: figure 1. fishbone diagram of traffic accidents on the krian – taman sidoarjo road. 2. analysis of traffic accidents characteristics the method used is the “5w + 1h” approach issued by the department of settlements and regional infrastructure [14], namely: why (factor of accident), what (type of vehicle), where (location of accident), who (involvement of road users), when (time of occurrence) and how (type of vehicle movement). civil and environmental science journal vol. 05, no. 02, pp. 183-193, 2022 186 2.3.2. analysis of respondents’ characteristics. this analysis will describe the characteristic of drivers of freight transport passing through the krian – taman sidoarjo road using descriptive statistical methods in the form of pie charts. 2.3.3. analysis of traffic accident modeling and probability. this analysis used logistic regression with the help of spss software. the first step that must be taken is determining the independent and dependent variable. table 1. independent and dependent variable in research. independent variable x1 = age dependent variable y = involvement in traffic accident on the krian – taman sidoarjo road in determining the model of logistic regression equation using the following formula: π (𝑥) = 𝑒𝛽0 + 𝛽1 𝑥1+ …...+ 𝛽𝑝 𝑥𝑝 1 + 𝑒𝛽0 + 𝛽1 𝑥1+ …...+ 𝛽𝑝 𝑥𝑝 (1) with : p = number of predictor/ independent variable x1, x2, ..., xp = independent variable β = independent variable coefficient furthermore, to determine the estimated probability of traffic accidents using the following formula: 𝑔(𝑥) = 𝑙𝑛 ( 𝜋 (𝑥) 1 − 𝜋 (𝑥) ) = 𝛽0 + 𝛽1 𝑥1 + . . . . . + 𝛽𝑝 𝑥𝑝 (2) 𝑙𝑜𝑔𝑖𝑡(π(𝑥)) = 𝜋 (𝑥) 1 − 𝜋 (𝑥) = 𝛽0 + 𝛽1 𝑥1 + . . . . . + 𝛽𝑝 𝑥𝑝 (3) after the above calculation, it will produce an exponential value that will be used to calculate the estimated probability value with the following formula: 𝜋0 (𝑥) = 1 1 + exp 𝑔(𝑥) (4) 𝜋1 (𝑥) = exp 𝑔(𝑥) 1 + exp 𝑔(𝑥) (5) furthermore, the feasibility test of the logistic regression model was carried out using the hosmer and lemeshow test (goodness of fit). 3. result and discussion 3.1. traffic accident data analysis 3.1.1. analysis of traffic accident causes. based on the analysis of traffic accident causes using a fishbone diagram, the following figure is obtained: civil and environmental science journal vol. 05, no. 02, pp. 183-193, 2022 187 figure 2. fishbone diagram analysis of traffic accidents causes on the krian – taman sidoarjo road. 3.1.2. analysis of traffic accident characteristics. based on the analysis of the traffic accidents characteristics on the krian – taman sidoarjo road from 2015 to 2020 with pie charts, the following figure is obtained: figure 3. percentage chart of traffic accidents causes (why) figure 4. percentage chart of vehicle type involved in traffic accidents (what) figure 5. percentage chart of traffic accidents location (where) figure 6. percentage chart of road users’ gender in traffic accidents (who). figure 7. percentage chart of road users’ age in traffic accidents (who). figure 8. percentage chart of road users’ jobs in traffic accidents (who). civil and environmental science journal vol. 05, no. 02, pp. 183-193, 2022 188 figure 9. percentage chart of traffic accidents day (when). figure 10. percentage chart of traffic accidents hour (when). figure 11. percentage chart of vehicle movement types during traffic accidents (how). the majority of traffic accidents caused on the krian – taman sidoarjo road are human factors, with 44 accidents (66%). the main causes of human factors including sleepy, speeding, lack of vigilance, loss of control, and traffic violations [15]. most vehicle types involved in traffic accidents on the krian – taman sidoarjo road are freight transport, with as many as 68 vehicles (47%); this is because the krian – taman road is an industrial area that is the route for freight transport to take and receive goods from the factory to their destination [16]. most traffic accidents location occurred on trosobo road (direction mojokerto – surabaya) as many as 20 incidents (30%); this is because the geometric condition in trosobo road flyover often causes loaded trucks and buses to experience brake failure [16]. the majority of road users in traffic accidents in krian – taman sidoarjo are male, as many as 143 people (89%); this is because the average person driving a freight transport vehicle is male [17]. the majority of road users aged in traffic accidents in krian – taman sidoarjo are in the age range of 26 to 45 years (adults), as many as 90 people (56%); this is because this age is a productive age for people to work and carry out daily travel activities [18]. the majority of road users job in traffic accidents on the krian – taman sidoarjo are drivers, as many as 71 people (45%); this is because the driver is a job mostly on the road, so the risk level of having a traffic accidents is higher than in other jobs [19]. most of traffic accidents day in krian – taman sidoarjo are on wednesdays and thursdays, with 13 incidents (20%); this is because the two days are working days where the traffic flow through the krian – taman sidoarjo road is high quite [15]. most of traffic accidents hour in krian – taman sidoarjo are in the morning (05.00 – 10.00) as many as 22 accidents (33%); this is because these hours are the time for people to carry out activities in the morning (school, work, etc.) [18]. the majority of vehicle movement types during traffic accidents in krian – taman sidoarjo are front-rear collisions with as many as 20 vehicles (30%); this is because the road conditions are quite wide and divided by the median and the low side barriers make road users accelerate at high speed so that the front of the vehicle has a high potential for accidents [20]. 3.2. analysis of respondents’ characteristics based on the results of the questionnaire to 150 respondents obtained the following characteristics: figure 12. distribution chart of respondents’ age. figure 13. distribution chart of respondents’ gender. figure 14. distribution chart of respondents’ education. civil and environmental science journal vol. 05, no. 02, pp. 183-193, 2022 189 figure 15. distribution chart of respondents’ job. figure 16. distribution chart of the average respondents’ income per month. figure 17. distribution chart of respondents’ freight transport vehicle types. figure 18. distribution chart of respondents’ vehicle load. figure 19. distribution chart of respondents’ vehicle ownership. figure 20. distribution chart of respondents’ reasons for using freight transport. the characteristics of the respondents of freight transport drivers on the krian – taman sidoarjo road are dominated by the age of 26 to 45 years about 85 people (56,7%), with the male respondents about 149 people (99,3%). the last education of respondents is senior high school/ equivalent about 96 people (64%), and 98 people (65,3%) were jobs as drivers. the respondents’ average income is rp. 2.500.000,up to rp. 5.000.000,per month is about 109 people (72,7%). the most type of freight transport vehicle is medium trucks with open/ closed/ tank (conf. axis 1.2 and permitted vehicle weight: 5.500 to 12.000 kg) about 49 people (32,7%), with vehicle load including general goods (general cargo, metal, wood, palletized/ packaged cargo, vehicles with side curtain covers and flat glass) about 75 people (50%). the vehicle owned by the company was about 75 people (50%), and the reason for using freight transport is that it was more profitable about 76 people (50,7%). 3.3. analysis of traffic accidents modelling and probability 3.3.1. testing the independent variables on the dependent variable of the occurrence of traffic accidents. based on the test results of the independent variable to dependent variable in spss software obtained: table 2. variable test results. independent variable p-value/ sig. explanation age (x1) .004 significant table 2 above shows that the age variable has a significant effect on the occurrence of traffic accidents because it has sig. < α that is 0,004 < 0,05. 3.3.2. model and probability of each independent variable on the occurrence of traffic accidents. the age variable that has a significant effect is then used to determine the model and probability of the results of the logistic regression test. civil and environmental science journal vol. 05, no. 02, pp. 183-193, 2022 190 • variable of age (x1) table 3. the results of the logistic regression test for the variable of age (x1). variables in the equation b s.e. wald df sig. exp (b) 95.0% c.i. for exp (b) lower upper step 1a x1 .062 .021 8.498 1 .004 1.063 1.020 1.108 constant -3.127 .941 11.031 1 .001 .044 a. variable (s) entered on step 1: x1. 𝑙𝑜𝑔𝑖𝑡 (𝑝) = −3,127 + 0,062 age for respondents aged 20 years, the probability obtained is: 𝑝 = 𝑒−1,887 1 + 𝑒−1,877 = 13,16% by using the above formula, table 4 is obtained below. table 4. probability of traffic accident. age logit (p) probability of being involved in the traffic accident 20 -1.887 13.16% 25 -1.577 17.12% 26 -1.515 18.02% 28 -1.391 19.92% 30 -1.267 21.98% 32 -1.143 24.18% 33 -1.081 25.33% 34 -1.019 26.52% 35 -0.957 27.75% 36 -0.895 29.01% 38 -0.771 31.63% 40 -0.647 34.37% 41 -0.585 35.78% 42 -0.523 37.22% 43 -0.461 38.67% 44 -0.399 40.16% 45 -0.337 41.65% 46 -0.275 43.17% 47 -0.213 44.70% 48 -0.151 46.23% 50 -0.027 49.33% 51 0.035 50.87% 52 0.097 52.42% 54 0.221 55.50% civil and environmental science journal vol. 05, no. 02, pp. 183-193, 2022 191 age logit (p) probability of being involved in the traffic accident 55 0.283 57.03% 56 0.345 58.54% 58 0.469 61.51% 60 0.593 64.41% table 4 shows that the older the driver, the higher the probability of being involved in a traffic accident. 3.3.3. logistic regression model testing. to test the feasibility of the logistic regression model using the hosmer and lemeshow test (goodness of fit), assuming: h0: the model can explain the data h1: the model is unable to explain the data test statistics: • h0 is accepted if sig. > 0,05 or h1 is rejected if sig. < 0,05 • h0 is accepted if chi-square count < chi-square table table 5. hosmer and lemeshow test for the logistic regression test for the age variable. hosmer and lemeshow test step chi-square df sig. 1 3.641 7 .820 in table 5 above, the value of sig. = 0,820 > 0,05 and chi-square count = 3,641 < chi-square table = 14,06741 so that h0 is accepted. with a 95% confidence level, it can be said that the logistic regression model used can explain data and deserves to be interpreted. table 6. model summary for the logistic regression test for the variable of age. model summary step -2 log likelihood cox & snell r square nagelkerke r square 1 190.912a .060 .081 a. estimation terminated at iteration number 4 because parameter estimates changed by less than ,001. in table 6 above, the value of nagelkerke r square = 0,081, so it can be said that the independent variable can explain the dependent variable by 8,1% so that other variables influence the rest by 100% 8,1% = 91,9%. 4. conclusions the characteristics of the respondents of freight transport drivers on the krian – taman sidoarjo road are dominated by the age of 26 to 45 years, about 56,7%, gender is male about 99,3%, the last education is senior high school/ equivalent, about 64%, the drivers’ jobs about 65,3%, the average income per month is rp. 2.500.000,up to rp. 5.000.000,about 72,7%, types of freight transport vehicle is a civil and environmental science journal vol. 05, no. 02, pp. 183-193, 2022 192 medium truck with open/closed/tank about 32,7%, vehicle load is in the form of general goods about 50,0%, vehicle ownership status is the company about 50% and the reasons for using the land mode to transport goods is more profitable about 50,7%. from the study results, it is known that the age variable affects the occurrence of traffic accidents by modelling: logit (p) = -3,127 + 0,062 age. the older the driver, the higher the probability of being involved in a traffic accident. acknowledgments we thank you very much for the assistance, data, and survey support in the field to the service unit of motor vehicle weighing trosobo sidoarjo and police resort sidoarjo. references [1] world health organization. "global status report on road safety 2018: summary", who, geneva, 2018. [2] nasional kompas.com, "perkenalkan pembunuh terbesar ketiga di tanah air", 2021. [online]. https://nasional.kompas.com/read/2016/04/27/08010021/perkenalkan.pembunuh.terbesar.keti ga.di.tanah.air.?page=all [3] kominfo.go.id, "rata rata tiga orang meninggal setiap jam akibat kecelakaan jalan," 2021. [online]. https://kominfo.go.id/index.php/content/detail/10368/rata-rata-tiga-orang-meninggalsetiap-jam-akibat-kecelakaan-jalan/0/artikel_gpr [4] f.d. hobbs, "perencanaan dan teknik lalu lintas," universitas gajah mada, yogyakarta, 1995. [5] fahza, a. and widyastuti, h. "analisis daerah kecelakaan lalu lintas pada ruas jalan tol surabaya gempol," jurnal teknik its, vol. 8, no. 1, pp. e54-e59, 2019. [6] a.d. fatikasari and c.a. prastyanto, "analisis biaya kerugian kemacetan jalan akibat adanya kerusakan pada kendaraaan berat di jalan primer (studi kasus: ruas jalan surabaya mojokerto)," jurnal aplikasi teknik sipil, vol. 19, no. 2, pp. 107-116, 2021. [7] pemerintah republik indonesia, "undang undang nomor 22 tahun 2009 tentang lalu lintas dan angkutan jalan pasal 203," sekretariat negara, jakarta, 2009. [8] pemerintah republik indonesia. "rencana umum nasional keselamatan (runk) jalan 2011 2035," sekretariat negara, jakarta, 2011. [9] investigasi.today, "polresta sidoarjo berupaya tekan angka kriminalitas dan budayakan masyarakat tertib lalu lintas", 2020 [online]. available: https://investigasi.today/tahun-2020polresta-sidoarjo-berupaya-tekan-angka-kriminalitas-dan-budayakan-masyarakat-tertib-lalulintas/ [10] kepolisian resort sidoarjo, "data kecelakaan lalu lintas kab. sidoarjo tahun 2015 2020. kepolisian resort sidoarjo", sidoarjo, 2021. [11] l. ambarawati, h. sulistio, g.h. negara, and z. hariadi, "karakteristik dan peluang kecelakaan pada mobil pribadi di wilayah perkotaan," jurnal rekayasa sipil, vol. 4, no. 2, pp. 124-135, 2010. [12] satuan pelayanan uppkb trosobo, "data lalu lintas harian angkutan barang tahun 2020," satuan pelayanan uppkb trosobo, sidoarjo, 2020. [13] austroads, "road safety audit (2nd edition)," sydney, australia: austroads incorporated, 2002. [14] departemen permukiman dan prasarana wilayah, "pedoman penanganan lokasi rawan kecelakaan lalu lintas nomor pd t-09-2004-b," departemen pekerjaan umum, jakarta, 2004. [15] n. utomo, "analisa faktor penyebab kecelakaan lalu lintas pada segmen jalan by-pass krian balongbendo (km. 26+000 km. 44+520)," jurnal teknik sipil kern, vol. 2, no. 2, pp. 7384. 2012. [16] s.a. arianto and a.a.g. kartika, "studi kelayakan pembangunan jalan layang (fly over) pada ruas jalan sepanjang krian km 16+540 17+680 ditinjau dari segi teknik lalu lintas dan ekonomi" jurnal teknik pom its, vol. 1, no. 1, pp. 1-6, 2012. civil and environmental science journal vol. 05, no. 02, pp. 183-193, 2022 193 [17] y. chang, c. li, t. lu, k.d. artanti, and w. hou, "risk of injury and mortality among driver victims involved in single-vehicle crashes in taiwan: comparisons between vehicle types," international journal of environmental research and public health, no. 17, pp. 1-8, 2020. [18] herawati, "karakteristik dan penyebab kecelakaan lalu lintas di indonesia tahun 2012," jurnal warta penelitian perhubungan, vol. 26, no. 3, pp. 133-142, 2014. [19] b.d. hartanto, "analisis perilaku pengemudi truk serta kontribusinya pada kecelakaan," jurnal penelitian transportasi darat, vol. 23, no. 1, pp. 79-87, 2021. [20] e. widjajanti, "karakteristik kecelakaan lalu lintas pada jalan tol jagorawi km 19 km 40 kabupaten bogor", jurnal teknik sipil, vol. 5, no. 1, pp. 76-88, 2021. civil and environmental science journal vol. 4, no. 2, pp. 127-140, 2021 127 analysis of cross-section capacity of jambi river at muaro jambi temple about various flood return period using hec-ras software putri mayasari1, freddy ilfan1, yasdi1, rimba2 1environmental engineering department, faculty of science and technology, jambi university, 36361, indonesia 2public works and public housing office of jambi province, jambi, 36129, indonesia pmayasari0712@gmail.com1 received 24-03-2021; accepted 25-05-2021 abstract. jambi river is one of the rivers located in the muaro jambi temple complex area, muaro jambi regency, jambi province. muaro jambi temple is one of the tourist attractions in jambi province. this study aims to find the capacity of jambi river tested by planned flood discharge utilizing (synthetic unit hydrograph) hss nakayasu method for a return period of two, five, ten, twenty-five, fifty and hundred years. hec-ras software used to analyse the water level in the jambi river towards the flood potential that causes the submerging of the kedaton temple building. this research used the log pearson type iii method to calculate the planned rain return period and used the nakayasu synthetic unit method to calculate the planned flood discharge. the analysis showed that the jambi river could not load the flood discharge in the five, ten, twenty-five, fifty, and one hundred years return period at several measurement points: river sta-1, river sta-2 and river sta-5. the floodwater level did not cause the kedaton temple building to be flooded from the simulation result. keywords: cross-section capacity, design flood discharge, hec-ras, hydraulic analysis, hydrology analysis, water level 1. introduction floods are a type of natural disaster caused by water and interfere with human activities. floods are the most frequent natural disaster that happened in indonesia and caused losses to human life and the environment that occur due to overflowing rivers, reservoirs, and lakes that inundate the lowlands. floods also occur because rainwater is trapped in a cavity and becomes a puddle, changes in land use that trigger sedimentation/silting in the cross-sectional area of the river [2]. floods also occur because 1 cite this as: mayasari, p., ilfan, f., yasdi & rimba. (2021). analysis of cross-section capacity of jambi river at muaro jambi temple about various flood return period using hec-ras software. civil and environmental science journal (civense), 4(2), 127-140. doi: https://doi.org/10.21776/ub.civense.2021.00402.3 mailto:pmayasari0712@gmail.com civil and environmental science journal vol. 4, no. 2, pp. 127-140, 2021 128 the water flow rate/volume in a river or drainage channel exceeds its flowing capacity [1]. floods usually occur during the rainy season or when it rains [8]. floods happened at jambi province in 2003 and brought on several districts flooded. one of them is muaro jambi regency [3]. floods involved most of the houses around muaro jambi temple complex were flooded, muaro jambi regency was flooded, but the floods did not inundate kedaton temple around the jambi river. jambi river is one of the rivers located in muaro jambi temple complex area, more precisely in muaro jambi regency, muara jambi village, jambi, jambi province. muaro jambi temple is one of the tourist attractions and cultural reserve in jambi province and needs to be preserved. this study analyses the cross-section capacity and water level of floods in jambi river towards design flood discharge for the return period of two years, five years, ten years, twenty-five years, fifty years, and one hundred years. furthermore, this study also analyzes the water level in the jambi river based on the simulation results of hec-ras software towards the flood potential that causes the submerging of the kedaton temple building. 2. materials and methods figure 1. the map of research location and cross-section measurement point 2.1 materials 2.1.1 research location this research is located in jambi river, muaro jambi temple complex area around kedaton temple, muaro jambi regency and geographically located in latitude 1° 28.723's and longitude 103° 38.634'e (figure 1). the research began by conducting a preliminary survey in the jambi river area along with kedaton temple, muaro jambi temple. then, collect the rainfall data as secondary data from sumatra rivers regional office vi and meteorology, climatology, and geophysics agency of civil and environmental science journal vol. 4, no. 2, pp. 127-140, 2021 129 muaro jambi regency. then cross-sectional measurements were carried out in the jambi river as primary data. 2.1.2 data collection technique this research used primary data and secondary data. primary data collection is the photos of the condition of the jambi river and measuring the cross-section of the river along 1024 meters. the secondary data in this research are daily rainfall data from 2009 until 2019 sourced from sumatra rivers regional office vi (bwss vi) and daily rainfall online data from 2009 until 2019 sourced from meteorology, climatology, and geophysics agency (bmkg). 2.2 methods the analysis in this research is divided into two types, the first is the hydrological analysis and the second is hydraulic analysis. the hydrological analysis is divided into several calculation steps; (1) calculating the empty rainfall data, (2) calculating the consistency test of the rain data using the raps methods, (3) calculating the area average rainfall using the arithmetic methods, (4) calculating the design rain using the log pearson type iii methods and (5) calculating the amount of rain design used the nakayasu synthetic unit hydrograph (hss nakayasu) methods. the methods used in this research are as follows. 2.2.1 the calculation of planned rain in this research, the calculation of planned rain used the log pearson type iii methods for return period 2-years, 5-years, 10-years, 25-years, 50-years, and 100-years. most of the distribution log pearson type iii used in hydrology calculation analysis, especially in maximum data analysis. the equation used in calculating the amount of rain using the log pearson type iii method is as follows: log(𝑋𝑡 ) = log(𝑋) ̅̅ ̅̅ ̅̅ ̅̅ ̅ + 𝑘 ∗ (𝑆�̅�) (1) information: log (xt) : the value of x in the log that expected to occur in the return period t years log (x) : mean of the log values (x) k : the value from the table is a function of the return period and the coefficient of variation. sd : standard deviation figure 2. nakayasu synthetic unit hydrograph 2.2.2 the calculation of design flood discharge the calculation of design flood discharge used the nakayasu synthetic unit hydrograph methods. the nakayasu synthetic unit hydrograph methods are the hydrograph was developed based on several rivers in japan. this method only used two parameters; they are the river catchment area civil and environmental science journal vol. 4, no. 2, pp. 127-140, 2021 130 and the river length. the equations used in the nakayasu synthetic unit hydrograph methods are (figure 2) 𝑄𝑃 = 1 3.6 ( 𝐴𝑅𝑒 0.3𝑇𝑝+𝑇0.3 ) (2) 𝑇𝑝 = 𝑡𝑔 + 0.8 𝑇𝑟 (3) 𝑡𝑔 = 0.4 + 0.058 𝐿 for l > 15 km (4) 𝑡𝑔 = 0.21 𝐿 0.7 for l < 15 km (5) 𝑇0.3 = á𝑡𝑔 (6) 𝑡𝑟 = 0.5 𝑡𝑔 𝑢𝑝 𝑡𝑜 𝑡𝑔 (7) the hydrograph form can be seen from the following equation: a rising limb (qn) (0 < t < tp) 𝑄𝑡 = ( 𝑡 𝑇𝑝 ) 2.4 (8) b recession limb 1 (tp < t < tp + t0.3) 𝑄𝑟 = 𝑄𝑝 × 0.3 (𝑡−𝑇𝑝)/𝑇0.3 (9) c recession limb 2 (tp < t0.3 < t < tp + t0.3 + 1.5t0.3) 𝑄𝑡 = 𝑄𝑝 × 0.3 [(𝑡−𝑇𝑝)+(0.5𝑇0.3)]/(1.5𝑇0.3) (10) d recession limb 3 (t > tp + t0.3 + 1.5 t0.3) 𝑄𝑡 = 𝑄𝑝 × 0.3 [(𝑡−𝑇𝑝)+ (1.5𝑇0.3)]/(2𝑇0.3) (11) information: qp = peak flood discharge a = watershed area (km2) re = effective rainfall (1 mm) tp = duration from the beginning of flood until the top of the hydrograph (hour) t0.3 = duration from peak flood to 0.3 times peak discharge (hour) tg = concentration time (hour) tr = time unit of rainfall (hour) á = the coefficient of watershed characteristic usually taken 2 l = the length of the main river (km) after doing hydrological analysis, the next step is to calculate using hydraulic analysis to find the cross-section capacity of the jambi river and the floodwater level using the hec-ras software. 2.2.3 hec-ras software hec-ras software is an application that used for modelling the flows in the river. hec-ras is an acronym from hydrologic engineering centers river analysis system (ras), made by hydrologic engineering center (hec) and one division in institute for water resources (iwr), under the auspices of u.s. army corps of engineers (usace) (istiarto,2010). hec-ras is software for modelling a dimension of steady or unsteady flow. hec-ras software has four components for one dimension model, they are: • steady flow water surface component • unsteady flow simulation • sediment transport/movable boundary conditions civil and environmental science journal vol. 4, no. 2, pp. 127-140, 2021 131 • water quality analysis the calculation of the basic of cross-section the bottom of a cross-section of the water level can be estimated from one cross-section to the next by using the energy equation using an iteration procedure with an iterative procedure called the standard step method. rivers usually have a changing cross-section area and non-prismatic shape. the energy loss in the channel is a loss of energy due to basic friction or changes in the cross-section shape. the energy loss can be formulated as follows: 𝑌2 + 𝑍2 + á2𝑣2 2 2𝑔 = 𝑌1 + 𝑍1 + á 1𝑣1 1 2𝑔 + ℎ𝑒 (12) which is: y1. y2 = pressure height (m) z1. z2 = height (m) 𝑉1 2 2𝑔 . 𝑉2 2 2𝑔 = high height (m) á1. á2 = velocity coefficient ℎ𝑒 = energy loss (m) 3. results and discussion 3.1 hydrology analysis 3.1.1 the maximum rainfall data the first step for hydrology analysis is selecting the maximum rainfall data for each rain station to find design rainfall amount and design flood discharge. the researcher used the maximum rainfall data for 11 years from 2009-2019 sourced from sumatra rivers regional office vi (bwss) and daily rainfall online data from 2009 until 2019 sourced from meteorology, climatology, and geophysics agency (bmkg) and can be seen in figure 3. figure 3. the maximum rainfall data 3.1.2 data consistency test data consistency test is a hydrology analysis for finding the correctness of field data influenced by several factors such as the location of rain gauge stations changes and rain measurement procedures changes (figure 4). one of the methods of data analysis is the raps method. the raps method is a data resilience check or a data consistency check that uses the cumulative value of the deviation from the rain data 0 20 40 60 80 100 120 140 160 180 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 r a in fa ll year bwss bmkg civil and environmental science journal vol. 4, no. 2, pp. 127-140, 2021 132 series to the average rainfall value. the results of data consistency test calculations using the raps method at the bmkg and bwss vi rain gauge stations can be seen in table 1. figure 4. the map of rainfall gauge station location based on table 1. the consistency result test of rainfall using raps method in the rain gauge station bwss vi and bmkg muaro jambi obtained q count> q table and the value of r count> r table the rainfall data is consistent. table 1. raps test recapitulation results no rain gauge station raps test results information q/n0.5count q/n0.5table r/n0.5count r/n0.5table 1 simpang iii sipin stations bwss vi 1.786 3.807 1.630 4.295 data are consistent 2 climatology stations muaro jambi bmkg 2.313 3.807 2.270 4.295 data are consistent 3.1.3 regional rainfall analysis regional rainfall analysis in this research used the arithmetic method because only use two rainfall gauge stations which are quite close. the calculation of rainfall in the muaro jambi area using the arithmetic method can be seen in figure 5. civil and environmental science journal vol. 4, no. 2, pp. 127-140, 2021 133 figure 5. regional rainfall 3.1.4 the planned rain the planned rainfall is rain with a certain return period (t) expected to occur in a drainage area. meanwhile, the return period is a hypothetical time where an event with a certain value, for example, is planned rainfall. the calculation of the rain plan in this research uses several return periods, they are 2-years, 5-years, 10-years, 25-years, 50-years, and 100-years. the first step to calculate the planned rainfall is counting the statistical parameters consisting of several parameters. they have calculated the average rain, standard deviation, skewness coefficient (cs), kurtosis coefficient (ck), coefficient of variation (cv) to determine the type of distribution following the characteristics of the rainfall data. the calculation of the rainfall data statistical parameters shows that the rainfall data is not tied to any parameter, so the most suitable distribution is the log pearson type iii method. the calculated, planned rainfall results for the return period of 2-years, 5-years, 10-years, 25-years, 50-years, and 100-years using the log pearson type iii method can be seen in figure 6. figure 6. maximum design rainfall of log pearson type iii method 99.3 123.9 71.5 119 88.15 74.25 94.75 87.7 120 100 100.65 0 20 40 60 80 100 120 140 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 regional rainfall 96.653 112.932 121.472 130.883 137.12 142.802 0 20 40 60 80 100 120 140 160 2 5 10 25 50 100 d e si g n r a in fa ll return period (t) year log pearson iii civil and environmental science journal vol. 4, no. 2, pp. 127-140, 2021 134 3.1.5 distribution compatibility test the distribution compatibility test in this study used the chi-square test and the smirnov kolmogorov test. the distribution suitability test aims to describe the relationship between the depth of rain or discharge and the probability value. the calculation of the distribution fit test using the chi squared test shows that all distributions follow the rainfall data because the calculated x2cr value is smaller than the x2 table so that the pearson iii log distribution is suitable for analyzing the planned rainfall. to test the distribution compatibility using the smirnov kolmogorov test, all distributions follow the rainfall data because the d max value is smaller than the critical value (do) obtained from the table so that the pearson iii log distribution is suitable for analyzing the planned rainfall. 3.1.6 net rain net rain is the component of total rain that produces direct runoff, which is also influenced by the c value (runoff coefficient). the calculation of net rain or effective rain is one of the hydrological analysis to determine the flood discharge using the unit hydrograph method. to determine the runoff coefficient in this study, suyono's flow coefficient was used. the flow coefficient is a value or quantity used to determine the amount of surface runoff, which is determined based on a drainage area condition characteristic of the rain that falls in the area. the results of the calculation of net rain can be seen in table 2. table 2. hourly net rain number hour ratio cumulative hourly rain (mm) (%) (%) 2 5 10 25 50 100 1 0.50 43.679 43.679 17.955 23.102 25.86 28.935 30.995 32.884 2 1.00 11.353 55.032 4.667 6.005 6.72 7.521 8.056 8.547 3 1.50 7.964 62.996 3.274 4.212 4.71 5.276 5.651 5.996 4 2.00 6.340 69.336 2.606 3.353 3.75 4.200 4.499 4.773 5 2.50 5.354 74.690 2.201 2.832 3.17 3.547 3.799 4.031 6 3.00 4.680 79.370 1.924 2.475 2.77 3.100 3.321 3.523 7 3.50 4.185 83.555 1.720 2.213 2.48 2.772 2.970 3.151 8 4.00 3.803 87.358 1.563 2.011 2.25 2.519 2.699 2.863 9 4.50 3.498 90.856 1.438 1.850 2.07 2.317 2.482 2.633 10 5.00 3.248 94.104 1.335 1.718 1.92 2.151 2.304 2.445 11 5.50 3.038 97.141 1.249 1.607 1.80 2.012 2.156 2.287 12 6.00 2.859 100.000 1.175 1.512 1.69 1.894 2.029 2.152 design rain (mm) 96.65 112.93 121.47 130.88 137.12 142.80 flow coefficients 0.43 0.47 0.49 0.51 0.52 0.53 effective rain (mm) 41.11 52.89 59.20 66.24 70.96 75.28 3.1.7 analysis of watershed area analysis of watershed area for finding the large of watershed area that would be inputted data in calculation of design flood discharge. watershed area determination is using the help of google earth software. based on the results of the analysis, it was obtained that the watershed area was 10 km2 and the length of the main river was 5.61 km. the results of the delineation of the watershed can be seen in figure 7. civil and environmental science journal vol. 4, no. 2, pp. 127-140, 2021 135 figure 7. watershed area of jambi river figure 8. nakayasu synthetic unit hydrograph 3.1.8 planned flood discharge analysis (nakayasu synthetic unit hydrograph method) the calculation of flood discharge in this research uses the synthetic hydrograph unit method, because the watershed area is <2.5 km2. the synthetic hydrograph method used in this research is the nakayasu method, because it only uses physical data of the watershed, where the length of the river and the area of the river basin. the results of the planned flood discharge calculations using the nakayasu method can be seen below a. watershed physical input parameters the large of watershed area : 10 km2 river length : 5.61 km effective rain : 1.000 mm. hydrograph parameters (α) : 2. 0 10 20 30 40 50 60 70 0 5 10 15 20 25 30 d is c h a r g e ( m 3 /s ) time (hour) q 2 years q 5 years q 10 years q 25 years q 50 years q 100 years civil and environmental science journal vol. 4, no. 2, pp. 127-140, 2021 136 b. nakayasu synthetic unit hydrograph parameters time lag (tg) = 0.21 𝐿0.7 = 0.21 × 5.610.7 = 0.702 hours time reduced (tr) =1∗𝑇𝑔 = 1∗0.702 = 0.702 hours time peak (tp) = 𝑡𝑔 + 0.8 𝑇𝑟 = 0.702 + (0.8 ∗ 0.702) = 1.264 hours t0.3 = 𝛼∗𝑡𝑔 = 2∗0.702 = 1.405 hours peak discharge (qp) = 1 3.6 ( 𝐴𝑅𝑒 0.3𝑇𝑝+𝑇0.3 ) = 1 3.6 ( 10∗1.000 0.3∗1.264+01.405 ) = 1.557 m3/s the flood discharge plan uses the nakayasu method for a 2-year return period of 35.106 m3/s, for a 5-year return period of 45.101 m3/s, for a 10-year return period of 50.396 m3/s, for a 25-year return period, amounting to 56.298 m3/s, for the 50-year return period of 60.332 m3/s and for the 100-year return period of 63.987 m3/s. the results of the calculation of the flood discharge using the nakayasu synthetic hydrograph method can be seen in figure 8. 3.2 hydraulics analysis 3.2.1 analysis of cross-section capacity and water level of flood using hec-ras software hydraulics analysis in this research aims to find the capacity of jambi river tested by flood discharge nakayasu synthetic unit hydrograph for return period 2-years, 5-years 10-years, 25-years, 50-years, and 100-years using hec-ras software. the result is there is runoff at several measurement points for return period 2-years, 5-years, 10-years, 25-years, 50-years, and 100-years. simulation result from hec-ras software for a return period of 100-years can be seen in figure 9, figure 10 dan figure 11. figure 9. river sta 5 (measurement point 1) according to figure 9, figure 10 and figure 11 can be seen the figure of jambi river cross-section at river sta-5 (measurement point 1), river sta-4 (measurement point 2) and river sta-1 (measurement point 5) for return period 100 years that the water level exceeds the elevation of the left and right cliffs of the river so that runoff occurs at several measurement points. this is due to differences in elevation in the upstream and downstream of the river, causing backwater to flow. in addition, this is due to differences in the shape of the river cross-section at each measurement point. the three-dimensional cross-section shape of the simulation results of the hec-ras software can be seen in figure 12. 0 5 10 15 20 25 -1.0 -0.5 0.0 0.5 1.0 1.5 jambi river plan: plan 02 08/06/2021 river sta 0+000 station (m) e le v a ti o n ( m ) legend eg q 100 years ws q 100 years ground bank sta . 0 3 3 .033 . 0 3 3 civil and environmental science journal vol. 4, no. 2, pp. 127-140, 2021 137 figure 10. river sta 2 (measurement point 4) figure 11. river sta 1 (measurement point 5) figure 12. 3 dimension cross-section (perspective xyx) 0 10 20 30 40 50 60 -3 -2 -1 0 1 2 jambi river plan: plan 02 08/06/2021 river sta 0+297 station (m) e le v a ti o n ( m ) legend eg q 100 years ws q 100 years ground bank sta . 0 3 3 .033 . 0 3 3 0 5 10 15 20 25 30 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 jambi river plan: plan 02 08/06/2021 river sta 0+1024 station (m) e le v a ti o n ( m ) legend eg q 100 years ws q 100 years ground bank sta . 0 3 3 .033 . 0 3 3 5 4 3 2 1 jambi river plan: plan 02 08/06/2021 legend ws q 100 years ground bank sta civil and environmental science journal vol. 4, no. 2, pp. 127-140, 2021 138 3.2.2 water level analysis in jambi river based on simulation result using hec-ras software towards flood potential that causes submerging of kedaton temple hec-ras software simulation results show that the cross-section capacity of the jambi river and the water level of each return period. furthermore, it is necessary to compare the elevation of the kedaton temple building using the help of google earth software with the flood water level at the measurement point in front of kedaton temple. they are the third measurement point (river sta-3), the fourth measurement point (river sta-2) and the fifth measurement point (river sta-1). the results of elevation measurements can be seen in figure 13. figure 13. elevation comparison measurement results the comparison shows that the elevation of the temple building is higher than the elevation of the flood water level so that it does not cause the kedaton temple building to be flooded. the results of the elevation comparison for the 100-yearreturn period on river sta-3 (measurement point 3), river sta-2 (measurement point 4) and river sta-1 (measurement point 5). can be seen in table 3. table 3. comparison of temple elevation with water level river sta profile w.s. elevation (m) temple elevation (m) information distance from segment to temple (m) 3 q 100 years 1.610 20 not submerged 107 4 q 100 years 1.570 20 not submerged 122 5 q 100 years 1.270 20 not submerged 330 4. conclusion the results show a runoff in the 5 year and 10-yearreturn period at the fourth measurement point (river sta-2). furthermore, in the 25 year, 50-yearand 100-yearreturn period, runoff occurs at the first measurement point (river sta-5), the fourth measuring point (river sta-2) and the fifth measuring point (river sta-1). based on the analysis of the flood water level obtained from the hec-ras software compared with the results of comparing the elevation of kedaton temple using google earth civil and environmental science journal vol. 4, no. 2, pp. 127-140, 2021 139 software, it does not cause the kedaton temple building to be flooded. in the future, conduct further research using data on the effect of the batanghari river discharge on all ancient tributaries or canals found in the muaro jambi temple complex with analysis using unsteady flow in the hec-ras software as an analysis tool and including several variables. other to produce countermeasures that need to be carried out on ancient tributaries or canals in the muaro jambi temple complex. 5. acknowledgements acknowledgements are addressed to the sumatra rivers regional office vi (bwss vi), cultural heritage conservation center (bpcb), public works and public housing (pupr) office of jambi province, youth community of environmental lovers in muaro jambi and friends at environmental engineering, and jambi university who have helped a lot in conducting research, support and data collection used in research both primary data and secondary data. references [1] a. rosyidie, “banjir: fakta dan dampaknya, serta pengaruhnya dari perubahan guna lahan,’’ jurnal perencanaan wilayah dan kota, vol. 24, no. 3, pp 241-249, dec. 2013. [2] a. sudrajat and m. fajar, “analisis kondisi eksisting penampang sungai cisangkuy hilir menggunakan hec-ras 4.1.0,” jurnal teknik lingkungan, vol 18 no. 1, pp 43-53, april. 2012. [3] bakhori, s. https://nasional.tempo.co/read/35452/separuh-wilayah-jambi-terendam-banjir. accessed 03 january 2020 [4] b. triatmodjo, hidrologi terapan,. beta offset: yogyakarta., 2009. [5] d. r. rivaldy, “evaluasi kapasitas penampang sungai tugurara kota ternate terhadap debit banjir,” jurnal sipil statik, vol. 6 no.6, pp 397-410, issn: 2337-6732, jun. 2018. [6] f. l. mamuaya, j. s. f. sumarauw, and h. tangkudung, “analisis kapasitas penampang sungai roong tondano terhadap berbagai kala ulang banjir,” jurnal sipil statik., vol. 7, no. 2, pp 179-188, issn: 2337-6732, feb. 2019. [7] f. prawaka, a. zakaria, and s. tugiono. “analisis data curah hujan yang hilang dengan menggunakan metode normal ratio, inversed square distance, dan cara rata-rata aljabar (studi kasus curah hujan beberapa stasiun hujan daerah bandar lampung)’’, vol. 4, no. 3, pp 397-406, issn: 2303-0011, sep. 2016. [8] f. taslim, sukarno and l. hendratta, “analisis kapasitas penampang sungai ongkag dumoga dengan metode hss itb dan hec-ras,” jurnal sipil statis, vol 7 no 2, pp 923-932, issn:2337-6732, august. 2019. [9] g. w. brunner, “hec-ras 5.0 reference manual. u.s. army corps of engineer.” hydrologic engineering center., 2016. [10] i. m. kamiana, teknik perhitungan debit rencana bangunan air, graha ilmu: yogyakarta., 2011. [11] istiarto, “simulasi aliran 1-dimensi dengan bantuan paket hidrodinamika hec-ras, jenjang dasar: simple geometry river,” universitas gadjah mada, yogyakarta., 2010. [12] kastamto, “prediksi morfologi dasar sungai akibat variasi tutupan vegetasi tebing sungai way sekampung,” vol. 3, no. 2, pp 310-311, 2012. [13] m. belladona, “pemetaan daerah genangan dan kajian genangan banjir pada kawasan komersial di kelurahan rawa makmur,” majalah teknis simes vol. 11, no. 1 jun. 2017. civil and environmental science journal vol. 4, no. 2, pp. 127-140, 2021 140 [14] n. yuniastiti and m. a. marfai, “prakiraan debit banjir rencana dalam analisis kapasitas tampung banjir kanal barat, provinsi dki jakarta,”jurnal bumi indonesia, vol. 4, no. 2, pp 20-29, 2015. [15] standar nasional indonesia. tata cara perhitungan debit banjir rencana. (sni 2415-2016). jakarta: badan standardisasi nasional, 2016. open access proceedings journal of physics: conference series civil and environmental science journal vol. 05, no. 02, pp. 215-224, 2022 215 effect of volume fraction hybrid composite duck feathers (anas plathycus borneo) rat purun fiber (eleocharis dulcis) with matrix polyester on tensile and bending strength akhmad syarief1, fadliyanur1, dhanu suryanta1, andy nugraha1, aulia aufa ramadhasari1, bayu setiawan1 1mechanical engineering department, lambung mangkurat university, banjarbaru, 70714, indonesian akhmad.syarief@ulm.ac.id, fadliyanur@ulm.ac.id, dhanu.suryanata@ulm.ac.id, andy.nugraha@ulm.ac.id, auliaaufar041201@gmail.com, setiawanbayu077@gmail.com received 05-08-2022; accepted 23-10-2022 abstract. alabio ducks (anas plathycus borneo) developed in the alabio area of hulu sungai utara regency, south kalimantan, with a duck population in 2006 recorded at 3,487,002 heads. so far, alabio ducks have only been used for meat and eggs, even though the feather part of this one poultry can also be used as a composite raw material because of its relatively strong and elastic nature. to improve the quality of the composite, duck feathers are combined with rat purun fibers (eleocharis dulcis) to become hybrid composites. fraksi volume hybrid composite duck feathers and rat purun fiber are as follows 10% : 90 %, 20% : 80%, 30% : 70%, 40% : 60%, 50% : 50%, 60% : 40%, 70% : 30%, 80% : 20%, 90% : 10%. this study used experimental methods. from the results of the study, it is known that the value of tensile and tensile strength stress and bending strength decreased as the percentage of rat purun fibers decreased compared to the percentage of duck feathers. keywords: alabio ducks, purun rats, hybrid composite, tensile strength, bending strength, 1. introduction alabio ducks are flasma nutfah in the south kalimantan region that developed in the alabio area of hulu sungai utara regency of south kalimantan, with the population of alabio ducks in south kalimantan in 2006 recorded at 3,487,002 head. alabio ducks are one of the local indonesian duck families with a geographically original distribution in south kalimantan province. they have been determined through the decree of the minister of agriculture number 2921/kpts/ot.140 /6/2011 dated june 17, 2011. alabio ducks have distinctive characteristics that are not possessed by ducks from other nations, as seen in figure 1. therefore, they are a genetic resource for indonesian livestock that needs to be maintained and preserved. mailto:fadliyanur@ulm.ac.id mailto:dhanu.suryanata@ulm.ac.id mailto:auliaaufar041201@gmail.com civil and environmental science journal vol. 05, no. 02, pp. 215-224, 2022 216 figure 1. male alabio ducks so far, the focus of using alabio ducks has only been on the meat and eggs, while other parts, such as the fur are not used at all and are often only considered waste and burned. even though the feather part of this one poultry can also be used. duck feathers can turn out to be able to bring profits for duck breeders who are creative in utilizing duck feathers [1]. alabio duck feathers can be used as composite raw materials with the purun tikus plant (eleocharis dulcis). the mouse purun plant is an upright perennial herbaceous with an elongated stem, brownish to black. it has roots, stems, reducing leaves, and flowers. erect stems are unbranched, grayish to shiny green in color, with a length of 50-200 cm with a thickness of 2-8 mm [2]. the leaves shrink to the basal part of the midrib, like a membrane, and the tip is asymmetrical, reddish-brown to mauve, as seen in figure 2. figure 2. rat purun plant traditionally, the rat purun plant is used for industrial raw materials for furniture (chairs and tables) and household crafts (mats and woven bags). however, with the development of science and technology, the rat purun plant can be used as a composite raw material by taking the fibers contained in the stems and leaves [3]. rat purun fibers and duck feathers as reinforcing elements largely determine the mechanical properties of the composite because it passes on the load distributed by the matrix. volume orientation is a factor affecting the mechanical properties of composites [4]. rat purun fibers in the form of continued and duck feathers combined with polyester as a matrix are expected to produce maximum composite mechanical properties to support the concentration of alternative composites [5]. to find out the mechanical properties of composites, bending and tensile testing can be carried out. civil and environmental science journal vol. 05, no. 02, pp. 215-224, 2022 217 tensile testing is the most frequently carried out on an object. usually, in a material is listed the value of strength or tensile grace and the hardness number tensile testing is carried out on a separate or universal tensile testing machine for the principle of testing is that on a test object of a certain size is given a regular and even tensile load. [6] figure 3. tensile testing machine the tensile strength can be calculated by the equation: [7] 𝜎 = 𝐹 𝐴0 ( 𝑁 𝑚𝑚2 ) (1) where:  = engineering stress (voltage) (mpa), f = the load exerted in the direction perpendicular to the specimen (n), ao = the initial cross-sectional area before the specimen is given a load (mm2). the equation can calculate composite strain: 𝜀 = ∆𝐿 𝑙0 ×100% (2) where: ε = enginerring strain (strain) (%), lo = the length of the first specimen before being given a charge (mm), δl = length gain (mm). based on the curve of the test results, the elastic modulus, e (gpa), can be calculated by the equation: 𝐸 = 𝜎 𝜀 (3) where: e = modulus of elasticity (gpa),  = engineering stress (voltage) (mpa), ε = enginerring strain (strain) (%). the test aims to determine the bending strength of a material by bending testing the composite material. bending testing refers to the astm d790 standard with static test conditions. bending strength or curved strength is the largest bending stress that can be accepted due to external loading without undergoing large deformations or failures. the magnitude of bending strength depends on the type of material and loading. as a result of bending testing, the upper part of the specimen is subjected to pressure, while the bottom will experience tensile stress. in composite materials its compressive strength is higher than in its tensile strength. unable to withstand the received tensile stress, the civil and environmental science journal vol. 05, no. 02, pp. 215-224, 2022 218 specimen will break. it resulted in a failure in the composite test. the bending strength on the upper side equals the value of the bending strength on the lower side. bending strength can be formulated as follows: 𝜎 = 3𝐹𝐿 2𝑏𝑑2 (4) the following formula can calculate the modulus of bending elasticity: 𝐸𝑏 = 𝐿3 ×𝑚 4𝑏𝑑3 (5) 2. materials and methods 2.1 materials in this study, researchers used duck feather waste and rat purun fibers from alabio, sungai pandan district, hulu sungai utara regency, south kalimantan province, to become composite reinforcing raw materials. duck feathers wasted on every duck meat sold in the market is one of the global issues in almost every country. the duck feather waste produced by the livestock industry is between 2 million and 3 million pounds annually. most of them burn the waste, burying it and mixing it back into animal feed—those methods are costly and contradictory. in indonesia itself, duck livestock is a popular business, so the duck fur waste produced is quite a lot. however, duck feather waste in indonesia still sounds new and cannot be utilized optimally. rat purun fiber (eleocharis dulcis) is one of the alternative natural fibre materials. in the scientific manufacture of composites, composite materials with these materials have not yet existed, so this composite is expected to provide added value economically [8]. traditionally it is only used for industrial raw materials furniture (chairs and tables) and household crafts (mats and woven bags). [2] the stems in rat purun differ from rice straw stalks, where rice straw stalks have bones of air cavity segments. but generally, it can be equated in its use as a composite manufacturing material. as for the good requirements to use: 1) have a sufficient level of drought (water content is only 14-16% only). please don't get it exposed to rain or splashing water though. because when it contains too much water, it has the potential to live mushrooms and small insects. 2) it looks brilliant on his skin as a sign that he has sufficient strength and has not deflated his air cavity. when stored for too long, the color changes to pale or older, depending on how it is stored. a long storage period can cause the air cavity to deflate. density checks can also be done by stacking them and then stepping on them; if they deflate immediately, the quality is not good. but the quality is good if it deflates for a moment and then comes back again. 3) the thickness (diameter of the cavity), on average, is the same, therefore, what needs to be chosen is the length of the main stem. it is estimated that it takes the main trunk length to be about 20 cm after cleaning from the branches. 4) have the same weight on average. [3] 2.2 methods the material is washed thoroughly with water and dried. then the selection of duck feathers and rat purun fibers with an average diameter of 0.5 mm was carried out. the process of making hybrid composites, all fibers are made with a random model, by the hand lay-up method, the volume fraction of hybrid composites from duck feathers and rat purun fibers, namely (10% : 90%), (20% : 80%), (30% : 70%), (40% : 60%), (50% : 50%), (60% : 40%), (70% : 30%), (80% : 10%), (90% : 10%). the volume fraction of polyester used is 50% of the mold volume. after completing the manufacture of the hybrid composite, tested its mechanical properties, including tensile and bending strength testing. civil and environmental science journal vol. 05, no. 02, pp. 215-224, 2022 219 2.2.1 research procedures the material that will be used as a filler is in the form of duck feathers and rat purun fibers that have been cleaned using clean water and dried. for rat purun fibers it is pounded using wood until it becomes fiber, then dry it again, and then decomposed it using a comb or hand. the material used for this mold is glass with a thickness of 10 mm; this is because the printout is easier to remove. the test specimens were made one by one, as many as 54 pieces, with details of 27 pieces for tensile tests and 27 pieces for bending tests. the standard test carried out is astm with the following details: [9] 1) tensile test using astm e8 standard. the size of the mold made is a length of 200 mm, a width of 185 mm, and a thickness of 10 mm 2) hardness test using astm d 790-2 standard. the size of the mold made is a length of 205 mm, a width of 200 mm, and a thickness of 10 mm 3) in order not to make errors in the manufacture of the test object, the mold size is made a little larger, which is 1-5 mm figure 4. tensile test dimensions tensile test astm e8 based on the test standard used, namely astm d790, the shape of the specimen and its size can be seen as shown below: [9] figure 5. dimensions of astm d790 bending test specimen 3. result and discussion the research that has been carried out shows the results in figure 6 for tensile strain testing. this test shows that the strain occurring in the tensile test process is formed from the stress applied to the loading test specimen from the outside. from figure 6. a graph of the relationship between the volume fraction of duck feathers and rat purun fibers to the tensile strength of hybrid composite obtained that the highest tensile strength of 4.37 mpa was obtained at the volume fraction (10%: 90%). in comparison, the lowest strength of 3.70 mpa was obtained at the volume fraction (90%: 10%). the above results show that the volume fraction of duck feathers and rat purun fibers (10%: 90%) provides greater tensile strength than in other more volume fractions. it shows that the volume fraction (10%: 90%) of rat purun fibers and matrices can be distributed properly and evenly at the time of the composite manufacturing process so that the bond between rat purun fibers and their matrices can take place perfectly. therefore, it can directly increase the tensile strength of the rat purun fiberreinforced composite. the volume fraction (90%: 10%) provides a smaller tensile strength than the other volume fractions. it is because rat purun fibers can withstand large loads while duck feathers cannot withstand large loads and have the potential to reduce the strength of composites when combined with rat purun fibers into hybrid composites [10]. civil and environmental science journal vol. 05, no. 02, pp. 215-224, 2022 220 figure 6. graph of the relationship of volume fractions to tensile strength figure 7. graph of the relationship of volume fractions to tensile strain figure 7 shows that the highest tensile strain of 0.0112% is obtained at the volume fraction (10%: 90%), while the lowest tensile strain of 0.0070% is obtained at the volume fraction (90%: 10%). based on the results above, it is known that the greater the fraction of rat purun fiber, namely at a fraction of 90%, the greater the tensile strain value increases. this large strain indicates that in composites with a larger fraction of fibers, there is a good fiber interface bond [11] so that when given the loading, it does not immediately break [12]. figure 8 shows that the highest modulus of elasticity of 528.25 gpa was obtained at the volume fraction (90%: 10%), while the lowest of 391.64 gpa was obtained at the volume fraction (10%: 90%). the volume fraction (90%: 10%) produces a good composite material. 3,20 3,40 3,60 3,80 4,00 4,20 4,40 4,60 10% : 90% 20% : 80% 30% : 70% 40% : 60% 50% : 50% 60% : 40% 70% : 30% 80% : 20% 90% : 10% t e n si le s tr e n g th v a lu e ( m p a ) volume fraction (duck feathers : rat purun fiber) . 0,0000 0,0020 0,0040 0,0060 0,0080 0,0100 0,0120 10% : 90% 20% : 80% 30% : 70% 40% : 60% 50% : 50% 60% : 40% 70% : 30% 80% : 20% 90% : 10% t e n si le s tr a in (% ) volume fraction (duck feathers : rat purun fiber) . civil and environmental science journal vol. 05, no. 02, pp. 215-224, 2022 221 figure 8. graph of the relationship of volume fractions to the modulus of elasticity figure 9. graph of the relationship of volume fractions to bending strength figure 9 is a graph of the relationship between the volume fraction to the bending strength obtained; the result is that at the volume fraction (10%: 90%), a bending strength value of 105.5 mpa was obtained, but after the volume fraction (10%: 90%) there was a decrease in bending strength. the lowest volume fraction (90%: 10%) with a value of 14.25 mpa. the increased volume fraction of duck feathers does not change the bending strength but instead experiences a decrease in bending strength [13]. duck feathers cannot withstand large loads when combined with rat purun fibers into a hybrid composite [14]. in figure 10. graph of the relationship of volume fractions to modulus of bending elasticity shows that composites with a volume fraction of 90%: 10% have the highest modulus value of elasticity of 0.0060 gpa, and the lowest value of the modulus of elasticity is found in the volume fraction of 10%: 90% with a modulus value of elasticity of 0.0016 gpa. 0,00 100,00 200,00 300,00 400,00 500,00 600,00 10% : 90% 20% : 80% 30% : 70% 40% : 60% 50% : 50% 60% : 40% 70% : 30% 80% : 20% 90% : 10% m o d u lu s o f e la st ic it y ( g p a ) volume fraction (duck feathers : rat purun fiber) . 0,00 20,00 40,00 60,00 80,00 100,00 120,00 10% : 90% 20% : 80% 30% : 70% 40% : 60% 50% : 50% 60% : 40% 70% : 30% 80% : 20% 90% : 10% b e n d in g s tr e n g th ( m p a ) volume fraction (duck feathers : rat purun fiber) . civil and environmental science journal vol. 05, no. 02, pp. 215-224, 2022 222 figure 10. graph of the relationship of volume fractions to modulus of bending elasticity the modulus of elasticity of hybrid composite duck feathers and rat purun fibers increases as the volume fraction of rat purun fibers decreases. the above shows that the increasing volume fraction of rat purun fibers produces a brittle or rigid composite material [15], which is due to the process of forming composites in sheet form so that the mixing process is uneven, and the number of catalysts is large and also the fabrication process is still manually [16]. the fault that occurs in tensile testing is a brittle fault with fibers pulled out; in bending tests, the fault's shape is a tenacious fault with shorter pull-out fibers. it can be seen in figures 11 and 12. figure 11. macro photo of fault form tensile testing specimen figure 11 of the composite fault cross-section with a volume fraction of 10%: 90% shows that the composite has the highest strength value with a tensile strength value of 4.37 mpa. above there appears to be a brittle fracture; when the matrix breaks, the fibers also break along with the matrix. it is due to the lack of perfect fiber bonding, and this event matrix is marked with many fiber pull-outs. fiber pulls out is a way to measure the strength of the interface bond between a single fiber and a matrix. pull-out fiber tests; the ends of the fibers are embedded in the matrix. the fibers are pulled, and the matrix is held or pulled in the direction opposite the direction of the fiber pulling. where this fiber pull-out mechanism occurs because the bond between the fiber and the matrix weakens when the load given continues to increase [17]. when the matrix fails, the fibers can still bear the load, so the faulting process does not occur simultaneously [18]. 0,0000 0,0010 0,0020 0,0030 0,0040 0,0050 0,0060 0,0070 10% : 90% 20% : 80% 30% : 70% 40% : 60% 50% : 50% 60% : 40% 70% : 30% 80% : 20% 90% : 10% m o d u lu s o f b e n d in g e la st ic it y (g p a ) volume fraction (duck feathers : rat purun fiber) . civil and environmental science journal vol. 05, no. 02, pp. 215-224, 2022 223 figure 12. macro photo of bending test specimen fault shape figure 12 composite fault cross-section with a volume fraction of 10%: 90% is that the composite has the highest strength value with a bending strength value of 105.5 mpa. at the volume fraction of 10%: 90% is still visible at some point, there is a pull-out failure shown in figure 4.6; in addition to the pull-out found in the composite that reduces the bending force, it turns out that after the implementation of different magnification, debonding is seen in the composite [19]. debonding is the release of binding force between the fiber and the matrix. debonding occurs due to the lack of binding power between the fiber and the matrix. so that when there is pressure, the matrix is separated from the fiber [20]. 4. conclusions the study results concluded that the value of tension and strain tensile strength and bending strength decreased along with the decrease in the percentage of rat purun fibers compared to the percentage of duck feathers. the form of fault that occurs in tensile testing is a brittle fault with fibers pulled out; in bending testing, the shape of the fault that occurs is a brittle fault with shorter pull-out fibers. acknowledgements acknowledgments to lambung mangkurat university for funding this research with the dipa university budget scheme for fiscal year 2022 number: sp dipa023.17.2.677518/2022 dated november 17, 2021. following the decree of the chancellor of lambung mangkurat university no: 458/un8/pg /2022, march 28, 2022. references [1] ae purkuncoro, s djiwo, t rahardjo. pemanfaatan komposit hybrid sebagai produk panel pintu rumah serat bulu ayam (chicken feather) dan serat ijuk (arenga pinata) terhadap sifat mekanik dan sifat thermal komposit hybrid matrik polyester. universitas muhammadiyah surakarta. 2014. [2] totok wianto, ishaq, akhmad faisal, abdulah hamdi. rekayasa tumbuhan purun tikus (eleocharis dulcis) sebagai substitusi bahan matrik komposit pada pembuatan papan partikel. jurnal fisika flux, vol. 8, no.2, agustus 2011. [3] akhmad syarief.. uji lentur komposit polyester-serat purun tikus (eleocharis dulcis). jurnal info teknik. fakultas teknik universitas lambung mangkurat banjarbaru. 2012. [4] a eko purkuncoro, b widodo, a subardi. penggunaan fraksi volume komposit serat batang pisang kepok (musa paradisiaca) orientasi sudut acak dengan matrik polyester terhadap sifat mekanik seminar nasional inovasi dan aplikasi teknologi di itn malang. 2018. [5] pell, yeremias m, pengaruh fraksi volume terhadap karakterisasi mekanik green composite widuri – epoxy. prosiding seminar nasional sainsdan teknik, universitas nusa cendana, 2012. [6] jones, mrobert, mechanic of composite materials, second edition, handbook. 1975 [7] gibson, f ronald. principles of composite material mechanics, mcgrawhill. 1994. [8] agil s. pengaruh fpraksi volume terhadap sifat mekanik komposit widuri–polyester. jurusan teknik mesin, fakultas sains dan teknik, universitas nusa cendana. [9] astm d790-02, standard test methods for flexural properties of unreinforced and reinforced plastics and ,electrical insulating materials. https://publikasiilmiah.ums.ac.id/xmlui/handle/11617/5441 https://publikasiilmiah.ums.ac.id/xmlui/handle/11617/5441 https://publikasiilmiah.ums.ac.id/xmlui/handle/11617/5441 https://scholar.google.co.id/scholar?oi=bibs&cluster=12565259136173075485&btni=1&hl=en https://ppjp.ulm.ac.id/journal/index.php/infoteknik/article/view/1801 http://eprints.itn.ac.id/3466/ http://eprints.itn.ac.id/3466/ http://eprints.itn.ac.id/3466/ civil and environmental science journal vol. 05, no. 02, pp. 215-224, 2022 224 [10] bakri, mohammad iqbal, mohammad rifki., analisis variasi panjang serat terhadap kuat tarik dan lentur pada komposit yang diperkuat serat agave angustifolia haw, jurnal mekanikal, vol. 3 no. 1: 240-244. 2012. [11] mohammad alfian ilmy , salahuddin junus , ahmad adib rosyadi. pengaruh fraksi volume fiber glass terhadap sifat mekanik komposit fiber glass/epoxy dengan metode vari. jurnal stator, volume 1 nomor 1, januari 2018. [12] akhmad syarief, ahmad yafi’e. sifat material polyester hybrid composite-batang bemban (donax canniformis). scientific journal of mechanical engineering kinematika 2 (2), 97-104. 2018 [13] aminur. muhammad hasbi. yuspian gunawan. proses pembuatan biokomposit polimer serat untuk aplikasi kampas rem. seminar nasional sains dan teknologi fakultas teknik universitas muhammadiyah jakarta 2015. [14] akhmad syarief, muhammad amin. pengaruh variasi fraksi volume komposit polyester-serat kulit jagung (zea mays) terhadap kekuatan impak, bending, dan tarik. scientific journal of mechanical engineering kinematika 1 (1), 1-10. 2018. [15] kasman nogo, wenseslaus bunganaen, yeremias m. pell. pengaruh fraksi volume terhadap sifat bending komposit widuri – polyester. ljtmu: vol. 02, no. 02, oktober 2015, (37-44). [16] bakri, mohammad iqbal, mohammad rifki., analisis variasi panjang serat terhadap kuat tarik dan lentur pada komposit yang diperkuat serat agave angustifolia haw, jurnal mekanikal, vol. 3 no. 1: 240-244. 2012. [17] anggi febrianto. karakteristik sifat mekanik biokomposit serat kelapa dengan matrik plastik biodegredabel dari pla (poli lactic acid). repository universitas jember. 2014. [18] akhmad syarief, dhenny sumantri, ahmad robittah, syafa’at prayogi (2022). effect of alkalization duration and the orientation of fiber on composites of polyester reinforced fibre of terap tree (artocarpus elasticus) on impact and bending strength. international journal of mechanical engineering technologies and applications (mechta). vol.3 no 1, january 2022. [19] akhmad syarief, aa basyir, andy nugraha. pengaruh orientasi serat dan waktu alkalisasi pada laminates composite polyester-serat bemban (donax canniformis) terhadap kekuatan bending, impact dan bentuk patahan. info-teknik 22 (2), 209-226. [20] akhmad syarief, raliannoor, hajar isworo, a'yansabitah. voids analysis on polyester matrix composites reinforced with a combination of bambusa bluemena fiber and fiber glass from tensile test results. iop conf. series: materials science and engineering 1034 (2021) 012144. icomera 2020 https://scholar.google.co.id/citations?view_op=view_citation&hl=id&user=1lec1kwaaaaj&citation_for_view=1lec1kwaaaaj:hqojcs7dif8c https://scholar.google.co.id/citations?view_op=view_citation&hl=id&user=1lec1kwaaaaj&citation_for_view=1lec1kwaaaaj:hqojcs7dif8c https://scholar.google.co.id/citations?view_op=view_citation&hl=id&user=1lec1kwaaaaj&cstart=20&pagesize=80&citation_for_view=1lec1kwaaaaj:8k81kl-mbhgc https://scholar.google.co.id/citations?view_op=view_citation&hl=id&user=1lec1kwaaaaj&cstart=20&pagesize=80&citation_for_view=1lec1kwaaaaj:8k81kl-mbhgc https://scholar.google.co.id/citations?view_op=view_citation&hl=id&user=1lec1kwaaaaj&cstart=20&pagesize=80&citation_for_view=1lec1kwaaaaj:rhptsmosybkc https://scholar.google.co.id/citations?view_op=view_citation&hl=id&user=1lec1kwaaaaj&cstart=20&pagesize=80&citation_for_view=1lec1kwaaaaj:rhptsmosybkc https://scholar.google.co.id/citations?view_op=view_citation&hl=id&user=1lec1kwaaaaj&cstart=20&pagesize=80&citation_for_view=1lec1kwaaaaj:rhptsmosybkc civil and environmental science journal vol. 02, no. 01, pp. 024-034, 2019 24 hydraulic performance of concrete block pavement under high rainfall intensities laksni sedyowati1, eko indah susanti1 1 department of civil engineering, university of merdeka malang, malang, 65146, indonesia laksni.sedyowati@unmer.ac.id received 15-11-2018; revised 10-01-2019; accepted 04-03-2019 abstract. high rainfall intensity will generate different response on the concrete block pavement (cbp) performance. a study found that larger openings of cbp did not lead more water penetrated. in other study, larger openings can lead greater decrease in runoff velocity. the correlation between the openings, water penetration and runoff velocity has remained unclear. in this study, we investigated hydraulic performance of cbp as an impact of surface roughness condition, under high rainfall intensities, saturated sub-base layer, and various slope surfaces. we conducted experiment using a 2 m by 6 m of rectangular cbp layer with herringbone 90o and basket-weave pattern. we used a modified dye tracing method in view to monitor the surface flow velocity under various high rainfall intensities. the results showed that hydraulic performance of surface runoff in the cbp layer was more influenced by the surface roughness condition. the roughness condition was very sensitive to the change in surface configuration of the cbp. the relationship between rainfall intensity, surface slope and roughness number followed polynomial functions. a further study is required to investigate the appropriate quality of cbps, which have high durability applied over a steep slope surface and under high rainfall intensities. keywords: low impact development, sustainable urban drainage system, source control, storm water management, paving blocks, roughness coefficient 1. introduction the use of concrete block pavement (cbp) has many advantages, such as able to penetrate the rainwater into the blocks, easy in installing, and has aesthetics value. to date, the usage of cbp has been so vary and widely spread. people used the cbp as road, driveway, park, carpark, sidewalk, etc. however, cbp performance in penetrating water has some limitations. it can be effective under some conditions, as follows: 1) the infiltration rate of the sub-base is more than the rainfall intensity [3]; 2) the sub-base has not reached saturated condition; and 3) there is no clogging. unfortunately, the cbp performance under adverse conditions did not been properly investigated. high rainfall intensity will generate different response on the cbp performance. there will be much water flowing on the cbp surface as runoff, because the infiltration rate is less than the rainfall intensity. more runoff will occur when the sub-base reached saturated condition. water flows over the cbp surface passing the gap between pavers. mailto:laksni.sedyowati@unmer.ac.id civil and environmental science journal vol. 02, no. 01, pp. 024-034, 2019 25 there have been some researches on the effects of cbp openings on surface runoff discharge and velocity. a study found that larger openings did not lead more water penetrated [1]. contrastingly, in other study larger openings can lead greater decrease in runoff velocity when the rainfall intensity and the slope surface were getting large [2]. although more water was flowing over the surface, the runoff velocity will decrease with the increase of rainfall intensity and surface slope. therefore, there is no general conclusion about the correlation between the openings, water penetration and runoff velocity. however, a study conducted by pagliara [4] on a flume by 7.5 m long, 0.35 wide and 0.60 m deep, with three kinds of bed material diameter (d50) consisted of 11 mm, 20 mm and 75 mm can be used as comparison. there were spaces between the stones. those stones and its spaces, particularly for the largest stone, had similarity with the gap between pavers on the cbp that used in this study. therefore, the configuration of paving blocks surface, that was the combination of the flat surface and the gaps, can produce a roughness factor that can retard the runoff velocity [2]. the virtual bed level, the flow through the rip rap, and the friction factor of the channel wall were also considered [4]. the study concluded that there was an increase in the friction factor with the increase in the slope for the same water depth and the area of boulders cover. the study also indicated that the increase in water depth could lead the decrease in influence of boulders in friction factor. the increase in surface slope can lead the increase of friction factor. the runoff velocity will decrease with an increase in friction factor. therefore, the increase in surface slope will lead the decrease in runoff velocity. there have been some researches on the relationship between surface roughness and the runoff velocity. surface roughness is one of major factor that influencing runoff velocity. “effective” roughness coefficient was actually generated from the effects of raindrop detachment, channelization of flow, obstacles (such as litter, crop ridges, rocks, and roughness from tillage), frictional drag over the surface, and erosion and sediment transport [5]. darboux has investigated the role of surface roughness in generating surface runoff [6]. experiment was conducted in a laboratory scale of a 2.4 m x 2.4 m soil box. the results indicated that a major effect on runoff generation could be resulted from a small modification of micro-topographic structure. all experiments indicated that there was a linear relationship between topographic correlation length and depression storage capacity. according to a study conducted by eitel [7], a surface topography mapped at the sub-cm level was able to generate surface roughness. the scale of the surface roughness erosion relationship and the regression model parameters were major factors in determining the strength of the relationship between surface roughness and erosion. effects of surface roughness on overland flow erosion process and advance hydrologic and erosion model parameters development were investigated using terrestrial laser scanning (tls). the decrease in the strength of the erosion-surface roughness relationship was an effect of removing the slope factor. an experiment conducted at a flume in the condition of high rainfall intensity and low soil rock fragment cover resulted that flow discharge was delayed slightly by the rock fragments [8]. the presence of the rock fragments led to the increase of infiltration rate. greater coverage of rock fragment and lower rainfall intensity increased the time-to-runoff. thus, the results indicated that with low rainfall intensity with significant rock fragment coverage, the surface soil saturation and the steady-state flow achievement take longer than for the case of no rock fragment coverage. the rock fragments were detentions for the overland flow and increasing the average of flow path length, causing to an increase in the time-to-runoff. although at present national land cover dataset (nlcd) land cover data may be the best practice for parameterizing surface runoff, however, it is inadequate. in terms of roughness parameter modelling, it would be better to use the physical structure or configuration of the terrain and the obstacles lying on it as the basic [9]. a study investigated four empirical models of roughness condition [10]. the models consisted of darcy-weisbach, lawrence, manning with constant roughness coefficient, and manning with water depth dependent roughness coefficient. the fourth’s model presented the best result comparing with the measured data on a sandy soil plot 10-m by 4-m with rainfall simulation. thus, roughness coefficient was flow-dependent. a hilly terrain considerably affected the roughness measures on a natural bare soil surface [11]. however, infiltration rate did not significantly influence the flow velocity. there was a limited effect civil and environmental science journal vol. 02, no. 01, pp. 024-034, 2019 26 of depression storage. this result was in line with the study conducted by mügler [10]. this research also concluded that overland flow resistance depended on water depth. the flow resistance decreased with an increase in water depth. the objectives of this study were to investigate the hydraulic performance of cbp indicated by surface roughness condition on cbp surface, the effect of high rainfall intensity and surface slope on roughness condition, and the best performance of cbp on generating the roughness number. the roughness condition was observed under high rainfall intensity, saturated sub-base layer, and various slope surfaces with considering the micro-topography formed by the gap and the pattern of paving blocks arrangement. 2. material and methods 2.1. study site experiments were conducted in a 179 m2 bare land located on a residential area, namely taman sulfat housing, malang city, east java province, indonesia. an experimental apparatus by 2m x 6 m was built on the area. the apparatus consisted of a paving block test plot and a 5-sprinkler rainfall simulator (figure. 1). height of the apparatus at the centre of length was 1.5 m, to accommodate surface slope variability up to 20%. the apparatus was constructed from cnp 15 profile steel in the side and 10 mm steel plat in the bottom. the test plot and the apparatus had same size. supply water to rainfall simulator was provided by a pipe-reservoir-pump system. the source of water was taken from freshwater supply agency (pdam). the pump could produce a pressure up to 1.8 kgf/cm2 and flow discharge of 10-18 l/min to produce rainfall intensity up to 80 mm/hr. figure 1. experimental apparatus with cbp test plot and 5-sprinkler rainfall simulator. 2.2. field data measurements and analysis measurements and analysis of observational data was preceded by some activities: 1) installation of the test plot and the rainfall simulator on the experimental apparatus; 2) preparation of flow measurement devices; 3) determination of the study design that included the variability of the civil and environmental science journal vol. 02, no. 01, pp. 024-034, 2019 27 treatment; 4) selection of travel time method that used for roughness coefficient analysis on cbp surfaces. 2.2.1. test plot and rainfall simulator installation. the test plot consisted of four kinds of cbp layers that observed one by one. the layers comprised rectangular cbp 90o-herringbone pattern (pav1), rectangular cbp basket-weave pattern (pav2), tri-hexagonal cbp (pav3), and hexagonal hollow cbp sand filled (pav4). to obtain a water saturation condition in the experimental process, the cbp layer was laid on an impermeable layer. this condition was required in generating an overland flow on the cbp surface. to drain the water that penetrated into the cbps, there was a hole of 5 cm diameter at the bottom of the plot. the rainfall simulator was designed to provide uniform rainfall with a simple technology. the technology was easy to construct, using local materials and manually operated (figure 2). the sprinklers used were butterfly type with specification pressure: 2.0-3.0 bar, flux:40120 l/h, range:4-8 m, and save water (figure 3). it was widely used for irrigation sprinkler and garden watering system. the frames of pipelines and sprinklers were designed such that they can adjust to the changes in slope of the test plot. it also can be moved depend on the space need for rainfall observation (figure 4). figure 2. rainfall simulator with 5 sprinklers and 1 mdistance sprinkler frame. figure 3. sprinkler with butterfly type. figure 4. adjustable sprinkler frame. civil and environmental science journal vol. 02, no. 01, pp. 024-034, 2019 28 2.2.2. flow measurement devices preparation. in this research, we measured travel time and discharge data. the travel time data were measured using dye-buoyant-oil tracing method. this method was a synthesised method of the dye tracing and float method. initially, a problem was appeared when only using the dye method. the raindrop detachment caused the dye was dispersed. at the lower end of the plot, the colour was not visible. the dye was then replaced by glitter powder that was coloured and shiny. however, the glitter powder cannot flow smoothly due to a constraint caused by the joint filler and the configuration of cbp. to solve the problem, oil was applied to the test plot so that the glitter powder can float on oil and reach the lower end. the discharge data was determined by measuring the volume of outflow from gutter every two minutes. the volume in litter were then divided by two minutes. 2.2.3. study design. the study design was experimental research and correlation analysis. firstly, we measured the flow velocity on the smooth pavement by applying a set of slope and rainfall intensity. afterwards, we observed travel time and discharge on four cbp layers with the same set of experimental design. the experimental design was as follows: 1) the slope gradient (s) consisted of 5%, 10% and 15%; 2) the rainfall intensity (i) consisted of 50 mmh-1, 55 mmh-1 and 60 mmh-1; and 3) four kinds of cbps as mentioned above. according to indonesian agency of meteorology climatology and geophysics (bmkg), international civil aviation organization (icao) and world meteorological organization (wmo), the rainfall intensities used in these experiments were categorized as high rainfall intensities. the surface roughness conditions were determined based on the difference of travel time between smooth layer and cbp layer. then, we calculated roughness coefficient based on travel time formula and roughness coefficient for overland flow developed by [12] and [13]. 2.2.4. izzard’s method, morgali-linsley’s method and sedyowati’s method for calculating travel time. according to a research conducted by [14], izzard’s travel time method was the best established method for estimating the travel time on cbp surfaces besides the method developed by [14], namely sedyowati travel time method. whereas the morgali-linsley’s equation was developed using kinematic wave analysis and manning’s roughness coefficient that widely used in practice. those methods have similar formula. they consist of four design parameters, that is l (length of overland flow or flow path), s (surface slope), i (rainfall intensity), and c (retardance coefficient for izzard) or n (manning roughness coefficient). the formulas are as follows: 1) izzard’s method: 𝑡𝑐 = 41.025(0.0007𝑖 + 𝑐)𝐿 0.33𝑆−0.333𝑖−0.667 2) morgali-linsley’s method: 𝑡𝑐 = 0.94𝐿 0.6𝑛0.6𝑆 −0.3𝑖−0.4 3) sedyowati’s travel time method: 𝑇𝑡 = 1.2. 10 4𝐹𝑟𝑑0.69𝑆−0.59(𝐼 𝐿⁄ )−2.99 ; where frd = flow retardance factor as a function of cbp properties, surface slope and raindrop size. 2.3. data analysis observation data analysis consisted of statistical analysis and surface roughness condition analysis. statistical analysis was conducted to know the effects of high rainfall intensity, surface slope and cbp types on surface roughness condition. the analysis consisted of correlation, determination and analysis of variance. afterwards, the roughness coefficient in each cbp surface was determined using izzard and morgali-linsley method. the roughness coefficient was modified to be fit for travel time observed data on cbp surfaces and sedyowati travel time model. the accuration of roughness coefficient selected was analysed using nash-sutcliffe efficiency (nse), mean absolute error (mae) and root mean square error (rmse). 3. result and discussion 3.1. roughness observation data on cbp surfaces civil and environmental science journal vol. 02, no. 01, pp. 024-034, 2019 29 table 1 shows the observation data of travel time taken from the three cbp surfaces, that is rectangular cbp 90o-herringbone pattern (pav1) with openings ratio (or = 0.068); rectangular cbp basket-weave pattern (pav2) with or = 0.065; tri-hexagonal cbp (pav3) with or = 0.073; and hexagonal hollow cbp sand filled (pav4) with or = 0.255. the data were observed in various rainfall intensities and surface slopes as mentioned above. table 1. observation data of travel time and the calculation of the decline of travel time on cbp surface compared with on smooth surface in various surface slope and rainfall intensity. s ia tb smooth tb pav1 tb pav2 tb pav3 tb pav4 tdec c pav1 tdec c pav2 tdec c pav3 tdec c pav4 0.05 50 2.05 2.68 2.65 3.02 4.28 0.63 0.60 0.97 4.28 0.05 55 1.77 2.28 2.50 2.83 3.40 0.51 0.73 1.06 3.40 0.05 60 1.25 1.50 2.00 2.17 3.83 0.25 0.75 0.92 3.83 0.10 50 1.75 2.67 2.40 2.67 2.78 0.92 0.65 0.92 2.78 0.10 55 1.43 2.17 2.20 2.50 1.40 0.74 0.77 1.07 1.40 0.10 60 1.03 1.87 1.95 2.13 1.39 0.84 0.92 1.10 1.39 0.15 50 1.38 1.92 2.10 2.63 0.95 0.54 0.72 1.25 0.95 0.15 55 0.70 1.87 1.90 2.37 1.22 1.17 1.20 1.67 1.22 0.15 60 0.57 1.73 1.80 2.05 1.13 1.16 1.23 1.48 1.13 a in mmh-1 b travel time observational data on smooth and cbp surfaces, in minute c travel time decline, as results of subtraction between t pav and t smooth, in minute data in table 1 were then processed to generate roughness number (rn). firstly, we calculated travel time decline between travel time on smooth surface and cbp surface. rn was then calculated as a comparison between travel time decline on a cbp surface and travel time of the cbp. in figure 5, serial number 1-3 have 5% slope; serial number 4-6 have 10% slope; serial number 7-9 have 15% slope. serial number 1, 4, 7 have 50 mmh-1 rainfall intensities; serial number 2, 5, 8 have 55 mmh-1 rainfall intensity; serial number 3, 6, 9 have 60 mmh-1 rainfall intensity. figure 5. plotting of roughness number (rn) data in the all cbp surfaces in various surface slope and rainfall intensity 0,00 0,10 0,20 0,30 0,40 0,50 0,60 0,70 0,80 1 2 3 4 5 6 7 8 9 r o u g h n e ss n u m b e r ( r n ) serial number of data pav1 (or=0.068) pav2 (or=0.065) pav3 (or=0.073) pav4 (or=0.255) civil and environmental science journal vol. 02, no. 01, pp. 024-034, 2019 30 figure 5 describes that the increase in rainfall intensity led to the increase in roughness number. according to [5] and [15], the greater rainfall intensity will lead to a greater raindrop splash. it also can be seen that the roughness number increased with an increase in surface slope. all cbp indicated the similar trend. this result supported a study conducted by pagliara [4]. contrastingly, pav1 particularly at 5% surface slope had different trend. it can be explained that in saturation and low slope condition, there was no more water penetration in pav1 (rectangular herringbone cbp), even under high rainfall intensity. the pavers gap in pav1 did not form a flow path that could maximized the water penetration [1]. pav4 indicated the greater mean roughness number with different trend particularly at 5% slope. however, at 10% and 15% slopes, despite having the largest openings ratio (or), pav4 shows the same roughness value as pav1 and pav2, and even lower than pav3. pav1 had smallest mean roughness number. at 5% slope, pav1 and pav2 showed significant differences in roughness number. however, at 10% and 15% slopes there was no significant difference in roughness number. the type and shape of paving blocks showed a significant effect on roughness. pav3 with more cavities on its surface provides a higher roughness value compared with rectangular shapes. this is in accordance with darboux's result [6]. while the difference in arrangement of rectangular paving block only gave significant effect at the mild slope. in this study, the cbp arrangement consisted of herringbone and basket-weave, and the basket-weave pattern was better in generating the roughness condition than herringbone. 3.2. correlation between roughness condition and the design parameters correlation analysis was performed using ms excel. correlation coefficient (r) resulted from the excel calculation was then squared to obtain determination coefficient (r2). those coefficients were used to identify the effects of the all design parameters on roughness number. the design parameters consisted of surface slope and rainfall intensity. according to figure 5, the trend of pav4 significantly differed with the others, therefore, the correlation analysis neglected the pav4 data. table 2 presents the correlation and determination coefficient between surface slope (s), rainfall intensity (i) and roughness number (rn). the correlation between roughness number and surface slope (r = 71%) was greater than roughness number and rainfall intensity (r = 47%). surface slope affected roughness number up to 51%, whereas rainfall intensity up to 22%. those results described that surface slope was the major factor that can retard the flow velocity, particularly on steep slope. the increase in surface slope will significantly increase the roughness number. this was in accordance with figure 5 above and research results found by pagliara [4]. table 2. correlation and determination coefficients between surface slope, rainfall intensity and roughness number parameter r r2 rn s i rn 1.00 1.00 s 0.71 1.00 0.51 i 0.47 0.00 1.00 0.22 figure 6 shows that for all observed data with rain intensity 50 mmh-1, 55 mmh-1, and 60 mmh-1 the relationship between roughness number and surface slope followed polynomial function, 𝑅𝑁 = 16.507. 𝑆 2 − 0.5253. 𝑆 + 0.2782 with determination coefficient 0.5236. figure 7 describes the scatter civil and environmental science journal vol. 02, no. 01, pp. 024-034, 2019 31 diagram for each cbp surfaces. it can be seen that in pav1 surface slope had the largest influence to the roughness number (r2 = 0.67), then followed by pav3 (r2 = 0.66) and pav2 (r2 = 0.51). pav2 had the smallest effect of surface slope due to the flow path formed by the paving block arrangement causing the water penetration was more affected by the rainfall intensity than the surface slope. these results supported the results of collins [1] and sedyowati [15]. while on pav1 and pav3 the arrangement pattern did not cause the occurrence of a straight flow path that led to water penetration. roughness factor was more influenced by cbp surface configuration and surface slope. figure 6. relationship between surface slope and roughness number in all various cbp and rainfall intensity. figure 7 also indicates that in each cbp surface the greatest correlation between roughness number and surface slope followed a polynomial function. pav3 indicated the greatest roughness number. pav2 and pav3 showed similar trend. this was due to the surface configuration of pav3 more varied in the presence of more cavities, and the greater opening ratio than pav1 and pav2. it significantly affected on surface roughness factors, and supported the conclusions of darboux [6] and medeiros [9]. figure 7. relationship between surface slope and roughness number on pav1, pav2 and pav3 in various rainfall intensity. y = 16,507x2 0,5253x + 0,2782 r² = 0,5236 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,00 0,05 0,10 0,15 0,20 r o u g h n e ss n u m b e r ( r n ) surface slope rn all pav poly. (rn all pav) r² = 0,67 r² = 0,51 r² = 0,66 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,00 0,05 0,10 0,15 0,20 r o u g h n e ss n u m b e r ( r n ) surface slope rn pav1 rn pav2 rn pav3 power (rn pav1) poly. (rn pav2) poly. (rn pav3) civil and environmental science journal vol. 02, no. 01, pp. 024-034, 2019 32 figure 8 presents the relationship between roughness number and rainfall intensity in various surface slope and the three types of cbp surfaces. it can be seen that rainfall intensity moderately influence roughness number (r2 = 0.23) and the relationship was also expressed by a polynomial function, 𝑅𝑁 = −0.0014. 𝐼2 + 0.1701. 𝐼 − 4.7361. figure 8. relationship between rainfall intensity and roughness number in all various cbp and surface slope. in contrast to figure 6, in figure 9 pav2 shows greatest determination coefficient (r2 = 0.46), and the lowest was pav1. the pattern of rectangular herringbone (pav1) did not allow more water penetration, therefore, rainfall intensity did not significantly contribute on the roughness condition. the roughness condition was more affected by surface slope. whereas in pav2 there were more water penetration caused by the flow path formation as mentioned by collins [1] and the raindrop splash effects as stated by engman [5] and jomaa [8]. more water penetration affected on the water depth. the decrease in water depth led to the increase in roughness condition. this result agreed to boundary layer theory developed by l. prandtl (1904) in [16], and research result by mugler [10] and smith [11]. figure 9. relationship between rainfall intensity and roughness number on pav1, pav2 and pav3 in various surface slope. y = -0,0014x2 + 0,1701x 4,7361 r² = 0,2288 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 45 50 55 60 65 r o u g h n e ss n u m b e r ( r n ) rainfall intensity (mmh-1) rn all pav poly. (rn all pav) r² = 0,13 r² = 0,46 r² = 0,31 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 45 50 55 60 65 r o u g h n e ss n u m b e r ( r n ) rainfall intensity (mmh-1) rn pav1 rn pav2 rn pav3 poly. (rn pav1) power (rn pav2) power (rn pav3) civil and environmental science journal vol. 02, no. 01, pp. 024-034, 2019 33 3.3. roughness coefficient analysis on cbp surfaces comparison between the observational data and simulation data calculated by izzard’s method resulted izzard roughness coefficient (c) for cbp overland flow, as follows: pav1 had c = 0.0125; pav2 had c = 0.013; and pav3 had c = 0.015. the nse, mae and rmse respectively were 65%, 21%, 30%. whereas comparison between simulation data generated by izzard’s method (with that izzard coefficient mentioned above) and sedyowati’s model resulted nse, mae and rmse respectively were 75%, 20%, 23%. it indicated that the observational data had wider range than the simulation data. comparison between the observational data and simulation data calculated by kinematic wave method developed by morgali-linsley resulted manning roughness coefficient (n) for cbp overland flow, as follows: pav1 had n = 0.09; pav2 had n = 0.1; and pav3 had n = 0.012. the nse, mae and rmse respectively were 66%, 21%, 30%, almost the same as the izzard method. however, when kinematic wave method (with that manning coefficient mentioned above) compared with sedyowati’s model, the accuration value was lower than the izzard method. the nse, mae and rmse respectively were 64%, 23%, 27%. these results supported the research results of sedyowati [14]. 4. conclusions the widespread usages of cbp particularly used as road need more attention in order to optimize the cbp functions. this study concluded that hydraulic performance of surface runoff in the cbp layer was more influenced by the surface roughness condition. the roughness condition was very sensitive to the change in surface configuration of the cbp, even only a little change. the rainfall intensities performed a little influence on the roughness condition (22%), however surface slope had significant impact (51%). the relationship between rainfall intensity, surface slope and roughness number followed polynomial functions. the equalization results of cbp surface roughness to izzard coefficient (c) and manning coefficient (n) are as follows: pav1 (rectangular cbp with herringbone pattern) had c = 0.0125 and n = 0.99; pav2 (rectangular cbp with basket-weave pattern) had c = 0.013 and n = 0.1; and pav3 (tri-hexagonal cbp) had c = 0.015 and n = 0.012. a further study is required to determine the quality of cbp that can be applied on steep slopes, as well as the strength of cbp to withstand the raindrop detachment resulted from the high rainfall intensity. acknowledgements we would like to thank to the people who have contributed in conducting this research, especially the students of civil engineering department, university of merdeka malang. this research was financially supported by the ministry of research, technology and higher education, republic of indonesia, through research grant namely penelitian produk terapan (ppt) 2017. references [1] k. a. collins, w. f. hunt, and j. m. hathaway, “hydrologic comparison of four types of permeable pavement and standard asphalt in eastern north carolina,” j. hydrol. eng., vol. 13, no. 12, pp. 1146–1157, 2008. [2] l. sedyowati, s. suhardjono, e. suhartanto, and m. sholichin, “runoff velocity behaviour on smooth pavement and paving blocks surfaces measured by a tilted plot,” j. water land dev., vol. 33, no. 1, pp. 149–156, 2017. [3] r. e. horton, “the role of infiltration in the hydrologic cycle,” eos trans. am. geophys. union, vol. 14, no. 1, pp. 446–460, 1933. [4] s. pagliara, r. das, and i. carnacina, “flow resistance in large-scale roughness condition,” can. j. civ. eng., vol. 35, no. 11, pp. 1285–1293, 2008. civil and environmental science journal vol. 02, no. 01, pp. 024-034, 2019 34 [5] e. t. engman, “roughness coefficients for routing surface runoff,” j. irrig. drain. eng., vol. 112, no. 1, pp. 39–53, 1986. [6] f. darboux, p. davy, c. gascuel-odoux, and c. huang, “evolution of soil surface roughness and flowpath connectivity in overland flow experiments,” catena, vol. 46, no. 2, pp. 125– 139, 2002. [7] j. u. eitel, c. j. williams, l. a. vierling, o. z. al-hamdan, and f. b. pierson, “suitability of terrestrial laser scanning for studying surface roughness effects on concentrated flow erosion processes in rangelands,” catena, vol. 87, no. 3, pp. 398–407, 2011. [8] s. jomaa et al., “rain splash soil erosion estimation in the presence of rock fragments,” catena, vol. 92, pp. 38–48, 2012. [9] s. c. medeiros, s. c. hagen, and j. f. weishampel, “comparison of floodplain surface roughness parameters derived from land cover data and field measurements,” j. hydrol., vol. 452, pp. 139–149, 2012. [10] c. mügler et al., “comparison of roughness models to simulate overland flow and tracer transport experiments under simulated rainfall at plot scale,” j. hydrol., vol. 402, no. 1, pp. 25–40, 2011. [11] m. w. smith, n. j. cox, and l. j. bracken, “terrestrial laser scanning soil surfaces: a field methodology to examine soil surface roughness and overland flow hydraulics,” hydrol. process., vol. 25, no. 6, pp. 842–860, 2011. [12] c. f. izzard and w. i. hicks, “hydraulics of runoff from developed surfaces,” in highway research board proceedings, 1947, vol. 26. [13] j. r. morgali and r. k. linsley, “computer analysis of overland flow,” j. hydraul. div., vol. 91, no. 3, pp. 81–100, 1965. [14] l. sedyowati, model waktu aliran berdasarkan model faktor retardasi aliran pada permukaan paving blok. digital library university of brawijaya, 2017. [15] l. sedyowati and e. i. susanti, “effects of concrete block pavement on flow retardation factor,” j. appl. eng. sci., vol. 7, no. 1, pp. 28–36, 2017. open access proceedings journal of physics: conference series civil and environmental science journal vol. ii, no. 01, pp. 067-075, 2019 67 the analysis of rainwater harvesting carrying capacity on water domestic supply for dwelling areas in indonesia gatot eko susilo1, muhammad jafri1 1civil engineering department, universitas lampung, bandar lampung, 35145, indonesia gatot89@yahoo.ca received 01-02-2019; revised 22-02-2019; accepted 18-03-2019 abstract. this research aims to promote the method to design rainwater harvesting facilities in indonesian dwelling areas. the estimation of rainwater harvesting (rwh) carrying capacity is undertaken using a simulation involving rainfall, inflow, and outflow data. the research was undertaken in natar sub-district, southern lampung, indonesia. daily rainfall data from branti airport from 2013 to 2017 are used for the simulation. research shows that houses in the study area can supply approximately 35% of their domestic water needs by applying rwh. this means that the support capacity of rainwater harvesting in the study area revolves around that value. the research also shows intensity of rainfall will greatly affect the carrying capacity of rwh. in addition to rainfall, the economic ability of a family plays an important role in planning the dimensions of a rwh facility in a house. finally, maintenance of rwh facilities on a regular basis is important to ensure the operational effectiveness of rwh. keywords: rwh, carrying capacity, facility, house. 1. introduction the increasing of world population from year to year triggers the increasing number of needs that must be fulfilled. this condition encourages more and more natural resources needed both in quantity and quality. among the various types of natural resources, water is one of the greatest natural resources for human benefit. in addition, for drinking, water is also needed by humans for various purposes of life such as bathing, washing, sanitation, gardening and others. the increasing population causes an increase in water demand. the increasing number of people from year to year around the world has led to an increase in water demand globally. although most of the surface of the earth is covered by water, not all types of water can be used directly for various human needs. clean and fresh water is basically the kind of water that humans really need. increased access and the needs of clean water can cause serious problems. reduced water reserves in the soil due to over-exploitation, and massive logging contribute to the future water scarcity. water scarcity is one of the main problems faced by many communities and the world in this century. the use of water has more than doubled the rate of population growth in the last century. water scarcity is already felt and affecting every region of the world. more than half of the population live in areas that have an indication of water scarcity both physically and economically. physical scarcity indicates the lack of water or water resources in an area. water scarcity occurs economically mailto:gatot89@yahoo.ca civil and environmental science journal vol. ii, no. 01, pp. 067-075, 2019 68 when an area or country lacks the necessary infrastructure to take water from its source. basically, on earth there is enough fresh water for seven billion people. but the problem of uneven distribution, waste in usage, pollution, and unsustainable management make water scarcity increasingly chronic in the world [1]. a 2014 study has surveyed water issues in about 500 major cities in the world. the survey finds that one of the world's four cities has water-related problems. another source says, based on un projections, by 2030 the world's freshwater demand will be 40 percent higher than availability. this condition is caused by several things, including climate change, human activities, and population growth. there are 12 major cities of the world experiencing a clean water crisis based on this study. some of them are in the asian continent of bangalore (india), beijing (china), jakarta (indonesia), and tokyo (japan). several other cities are on the continent of europe namely moscow (russia), istanbul (turkey), and london (uk) including also in the city that has problems with clean water. sao paulo (brazil), mexico city (mexico), and miami (usa) are cities in the american continent with water problems. cairo (egypt) and cape town (south africa) is a major city on the african continent that has recorded problems with water. among the cities above, cape town is the most severely affected city of water crisis. recent studies predict cape town's water reserves will be exhausted in early march 2018. the water crisis in cape town is partly due to very low rainfall in the last three years, as well as long drought. on the other hand, the population with water consumption continues to increase [2]. according to the un, the world needs to make radical changes in managing water resources to meet future water needs. the search for new water source alternatives and water-saving aesthetic movements should be made to maintain the existence of water resources from scarcity and deficits. one effort to overcome the problem of water scarcity is to conserve water. water conservation is done by storing water during wet or rainy seasons and using the water for various purposes in the dry season. water conservation philosophy is commonly used in water management in large reservoirs. basically, the principle of water conservation can be done in many aspects. one of them is by utilizing rain water for various purposes. utilization of rainwater at this time is better known as rainwater harvesting (rwh). rwh in some countries is applied to maintain the preservation of groundwater by directing the rainwater into the absorption wells to be impregnated into the ground as a recharge of groundwater. in some arid countries, the existence of rwh has existed since ancient times. in those countries people deliberately collected and stored rainwater for immediate use for various purposes of life such as drinking and sanitation. history records ancient peoples in the indus valley in india and pakistan had been using rwh technology for thousands of years. in many of the ancient cities remaining, many large stone barrels are found to collect rainwater that will be used to meet domestic and agricultural water needs. some of these stone barrels still exist and are still used today. another method used to collect rainwater is by collecting rainwater on the roof of the house and draining it into a reservoir. this method has been growing for hundreds of years in india and imitated by many world communities, especially the countries in asia. harvesting rain through the roof is known as rooftop rain water harvesting technique (rrwh). various societies around the world have applied rwh. developed countries such as the united states, canada, australia, japan and some countries on the europe continent have used rainwater in modern ways. in other parts of the world, people use technology to pick up the rainwater. in developing countries in africa and asia, people use simple containers and systems in rainwater harvesting so as to reduce the quantity and quality of collected rainwater. indonesia is a country with a tropical climate. there are only two seasons in indonesia which are dry season and rainy season. indonesia is geographically located at 6° ls 10° n and 95° east 141° east and lies between the indian and the pacific ocean. because of its location in a warm area of the equator then evaporation in the area occurs in large numbers. it is not surprising, therefore, that the rains continue to fall during the dry season. indonesia is an archipelagic country with a greater number of oceans than land. therefore, rain falls with high intensity. the average annual indonesian rainfall is about 2000 to 3000 mm. nevertheless, the rainfall in indonesia is not the same in every place. western civil and environmental science journal vol. ii, no. 01, pp. 067-075, 2019 69 indonesia gets more rain compared to eastern indonesia. this condition occurs because the geography and topography of the regions in indonesia are different from each other. many areas in indonesia are rich in water resources. domestic water needs are not difficult to overcome. on the opposite side, some regions in indonesia have difficulties in getting clean water for the community. in coastal cities, people do not find fresh water sources. as a consequence, the people fulfil their domestic water needs by buying water from merchants coming from other places. some swampy areas also share the same fate. people in the area are forced to buy water from other areas to meet domestic needs. some of these areas have started to collect and utilize rainwater for domestic purposes by implementing rainwater harvesting. however, the rainwater harvesting facilities they make are not technical and very simple. based on this, this research intends to promote the method for planning rwh facilities technically but simply. the proposed method is a method to estimate rwh's carrying capacity using a simulation involving rainfall data and water requirements as an inflow and outflow, respectively. the simulation philosophy is the water balance philosophy in rwh reservoir based on inflow and outflow behaviour. the focus of this research is the application of rwh in the dwelling areas. 2. material and methods 2.1. rainwater harvesting facility today, rain water harvesting is widely applied to the purpose of using rainwater as an alternative domestic water supply. in general, rain harvesting methods are carried out with rooftop (rrwh). the rrwh facility is technically not a complicated system. in general, the rrwh sketch is illustrated in figure 1. the mechanism in the rrwh system begins when the roof catches and collects rainwater. the caught rainwater is then collected through the gutters. the water-collecting gutters are equipped with strainers to remove relatively large debris such as leaves and gravel. the filtered water is then channeled into the reservoir by inlet pipe. the water contained in the reservoir is used for domestic water purposes. to ensure the quality of the rainwater to be used, the downstream portion of the reservoir is fitted with a filter comprising a nylon filter and activated carbon. the nylon filter serves as a small sediment and dust filter while activated carbon is used to remove odor from stored rainwater. a small water pump is used to drain water from the reservoir into the house. the pipeline from the reservoir to the house is called an outlet pipe. all components in the rrwh system require routine maintenance to ensure the smooth operation of the rrwh concerned. figure 1. rooftop rainwater harvesting (rrwh) facility 2.2. carrying capacity of rwh in general, urban communities in indonesia meet their domestic water needs from shallow wells, drilled wells, or buying from local water companies or from individual merchants. when someone civil and environmental science journal vol. ii, no. 01, pp. 067-075, 2019 70 implements rwh at home or at work then some of the domestic water needs can be partially replaced by rain water. the ratio of the number of days in a year to which the domestic water supply is supplied by rain water with the total number of days in a year is expressed in a percentage. this percentage illustrates the power of rwh in supporting domestic water supply within a household or office. this percentage is referred to as the carrying capacity of rwh. for example, an rwh facility with a carrying capacity of 41% will be capable of supplying domestic water requirements of a home or office for 150 days from 365 days in the year. carrying capacity of rwh varies from one location to another. this is because of the carrying capacity of rwh depends on the amount of inflow, outflow, and rwh facility dimension itself. to calculate the carrying capacity of a rwh facility, a simulation that involves inflow is daily rainfall with more than 10 years of data, roof area data, and reservoir dimension data. while to calculate the outflow data required the number of occupants of buildings and the amount of domestic water needs per capita. the simulation to get the value of carrying capacity of rwh is based on the water balance philosophy in the reservoir [3][4]. the equation in the simulation is given as follows [5][6][7]: 𝑆𝑡 = 𝑆𝑡−1 + 𝐼𝑡 − 𝑂𝑡 for 0 ≤ 𝑆𝑡 ≤ 𝑆𝑚𝑎𝑥 (1) where st is the reservoir volume on day t (m 3), st-1 is reservoir volume on day t -1 (m 3), it is inflow on day t (m3), ot is outflow on day t (m3), and smax is maximum storage capacity (m 3). the inflow and outflow for day t is calculated using formula 2 and 3, respectively: 𝐼𝑡 = 𝑐 × 𝑅𝑡 × 𝐴 × 1000 (2) 𝑂𝑡 = 𝑛 × 𝑑 (3) in the inflow formula, c is the runoff coefficient for roofs, the range value is ranged between 0.8 and 1.0 [8], rt is the volume of rainfall on day t (mm), and a is the area of roof (m 2). on the other formula, outflow for day t (ot) is formulated as a function of number of building occupants (n) and water demand per person per day (d). 2.3. case study the case study of the research is undertaken in natar sub-district, southern lampung, indonesia. natar is an area of 213.77 km2 and a population of 186,372. it is an emerging area from rural to urban. natar is a flat plain that is largely dominated by plantations and settlements. as a developing region, the availability of water is a necessity that must be considered for the survival of urban and community life. during this time the natar people rely on domestic water supply from shallow wells and boreholes. there is no public water company in the area. in the next few years, natar will begin to experience a clean water crisis in the dry season. therefore, introducing rainwater harvesting to meet domestic water needs is an important thing to do. this research aims to calculate the carrying capacity of rwh for home and office buildings in the natar region. for research purposes, the data used for the simulation are: • daily rainfall data taken from branti airport which is administratively located within the natar region. the data length is 5 years from 2013 to 2017. • roof area data • data on the number of building occupants • data of domestic per capita water demand (based on ministry of public works of the republic of indonesia per capita domestic water requirement for natar city is 90 l/day) civil and environmental science journal vol. ii, no. 01, pp. 067-075, 2019 71 figure 2. location of the study 2.4. the simulation simulation is undertaken in order to calculate carrying capacity of rwh. the example of simulation procedures is illustrated in the table as follows: table 1. an example of simulation procedures date r (mm) a (m2) c inf. (m3) n d (m3) outf. (m3) s (m3) (1) (2) (3) (4) (5) (6) (7) (8) (9) 01-jan-13 36.5 30 0.9 0.99 4.00 0.09 0.36 0.63 02-jan-13 68.0 30 0.9 1.84 4.00 0.09 0.36 2.10 03-jan-13 0.0 30 0.9 0.00 4.00 0.09 0.36 1.74 04-jan-13 12.2 30 0.9 0.33 4.00 0.09 0.36 1.71 the procedures above can be described as follows: • column 1 is the date on day t simulation • column 2 is the daily rainfall on day t (in mm) • column 3 is the area of the roof (in m2) • column 4 is the flow coefficient on the roof (set at 0.9) • column 5 is the volume of inflow on day t (in m3) calculated by the formula (2) • column 6 is the number of building occupants • column 7 is daily per capita water requirement (in m3) • column 8 is the outflow volume (in m3) on day t calculated by the formula (3) • column 9 is the volume of water in the reservoir (in m3) that is calculated by the formula (1) here is an example of calculation: to get the volume of water in the reservoir on jan 4, 2013 then: • s (jan 4, 2013) = inflow (jan 4, 2013) outflow (jan 4, 2013) + s (jan 3, 2013). • if s (jan 4, 2013) < 0 then s (jan 4, 2013) = 0 • if s (jan 4, 2013) > smax then s (jan 4, 2013) = smax, or in other words the s value (january 4, 2013) must be between 0 and smax. then the calculation can be done for another date. the carrying capacity of rwh is the number of days, whose the s > 0, divided by the number of days in the year which is 365 or 366. civil and environmental science journal vol. ii, no. 01, pp. 067-075, 2019 72 3. result and discussion 3.1. results of the research figure 3 illustrates daily rainfall data from branti airport from 2013 to 2017. the data shows rain accumulation between april and october. conversely, between may to september the rain did not fall too much. these data indicate that the area under study follows the usual rain patterns in indonesia. in most parts of indonesia, the rainy season occurs between october and april, and the dry season occurs between may and september. the intensity of rainfall in 2013, 2014, 2015, 2016, and 2017 is 2465.2 mm, 1682.5 mm, 1628.1 mm, 2317.6 mm, and 1825.1 mm, respectively. the year 2014, 2015 and 2017 are included into dry year with rainfall intensity of less than 2000 mm. on the other side, year of 2013 and 2016 are included into wet years with rainfall intensity of more than 2000 mm. figure 3. daily rainfall of branti airport for the simulation using the daily rainfall data above, a simulation to find rwh carrying capacity of a residential house is implemented. results of simulation are shown on figure 4. in indonesia, the type of house is usually based on the size of the building. for example, type 21 house means a house with an area of 21 m2. building area is considered equal to the roof area of the house. common types of houses in indonesia are: type 21, type 36, type 45, type 60, and type 70. house type 21 and type 36 are usually chosen by low-income families. while upper middle income families prefer to choose the type 45, type 60, and type 70. type 45 is the most favourite type of house in indonesia. house type 70 is a type of house that usually chosen by high economic class or a wealthy family. on the other hand, houses in indonesia are usually occupied by 4 to 6 residents consisting of father, mother, and 2 or 3 children. assuming that each house in the study area is generally a 45 type house occupied by 5 people, then based on the graph in figure 4 the carrying capacity of rwh in each house is 33 to 41% for smax between 2 to 8 m3. the simulation results above show the carrying capacity of rwh to provide domestic water supply per capita of 90 litres per day. generally, in indonesia people only use rain water for sanitation activities. sanitation activities require only about 80% of the total domestic water need [10]. therefore, if rwh water is only used for sanitation purposes then the carrying capacity of rwh will increase as shown in figure 5. 0,0 20,0 40,0 60,0 80,0 100,0 120,0 140,0 160,0 180,0 0 1 -j a n -1 3 0 1 -a p r1 3 0 1 -j u l1 3 0 1 -o c t1 3 0 1 -j a n -1 4 0 1 -a p r1 4 0 1 -j u l1 4 0 1 -o c t1 4 0 1 -j a n -1 5 0 1 -a p r1 5 0 1 -j u l1 5 0 1 -o c t1 5 0 1 -j a n -1 6 0 1 -a p r1 6 0 1 -j u l1 6 0 1 -o c t1 6 0 1 -j a n -1 7 r a in fa l (m m ) civil and environmental science journal vol. ii, no. 01, pp. 067-075, 2019 73 figure 4. carrying capacity of rwh for various values of a, n, and smax. figure 5. carrying capacity of rwh for house type 45, occupied by 5 people, with various values of maximum capacity of reservoir (smax) based on figure 4 fluctuations in the volume of water in the reservoir for each smax is presented in appendix 1. the fluctuation of water volume in the reservoir as shown in appendix 1 shows a pattern that is not very different from one another. the patterns formed follow the pattern of rainfall in the civil and environmental science journal vol. ii, no. 01, pp. 067-075, 2019 74 area concerned. this shows that rainfall is a parameter that has a very strong effect on the value of rwh carrying capacity. rainfall is also an independent parameter that can determine the maximum value of a rwh carrying capacity. in areas with very high rainfall intensities, the maximum capacity of reservoir (smax) and the roof area are parameters that also determine the maximum value of a rwh carrying capacity. in contrast, in areas where rainfall intensity is small, rainfall is the dominant parameter and other parameters do not significantly affect the maximum value of a rwh carrying capacity. the carrying capacity of rwh each year varies based on the number of rainy days and their intensity. the carrying capacity of rwh each year varies based on the number of rainy days and rainfall intensity. based on the simulation results, the dry years produce a smaller rwh carrying capacity than the wet years. table 2 illustrates the example of rwh carrying capacity for each year with the same a = 45 m2 and n = 5 people with various smax. the contents of the table clearly indicate that the carrying capacity of rwh in wet years (2013 and 2016) is greater than one in the dry years (2014, 2015, and 2017). the average carrying capacity of rwh in wet years ranges from 45 to 46% while in dry years it ranges from 30 to 35%. table 2. rwh carrying capacity for each year for a = 45 m2, n = 5 people, with various smax. year maximum capacity of reservoir (smax) in m3 average 2 4 6 8 2013 39.2% 45.5% 47.1% 48.5% 45.1% 2014 27.1% 32.9% 35.9% 37.0% 33.2% 2015 29.9% 31.0% 31.0% 31.0% 30.7% 2016 38.1% 44.9% 49.9% 51.2% 46.0% 2017 32.3% 35.9% 35.9% 35.9% 35.0% 2013 39.2% 45.5% 47.1% 48.5% 45.1% one important thing to do in order to ensure the effectiveness of rwh implementation is regular maintenance of rwh facilities. cleaning the roof of the house from dirt such as leaves, animal waste, and gravel, should be implemented to ensure the quality of rain water that fell to the roof. this activity can be done once or twice before the rainy season. clearing gutters from leaves or other debris may have to be more frequent to do especially in areas with many trees. sometimes the leaves fall and are carried by the wind into the gutter. the existence of these leaves on the gutters will clog the gut hole and inhibits the water entering into the inlet pipe. cleaning the gutters can be done once in a week or two weeks in the rainy season, depending on the amount of dirt that disrupts the effectiveness of the gutter. in the dry season the clearance of the gutter is done once in two weeks or a month depending on the amount of rain in the dry season. cleaning the reservoir can be done once in two months to remove the fine sediment accumulated at the bottom of the reservoir. the filter on the outlet pipe can be replaced within 3 to 6 months depending on the amount of filtered filth. filters can be purchased on the market at an affordable price. 4. conclusions analysis to investigate the carrying capacity of rainwater harvesting for clean water supply at the household level has been completed. the research produced several conclusions as follows: 1. the results show that in general the houses in the study area can supply approximately 35% of their domestic water needs by applying rwh. houses with larger size and larger rwh facilities will be able to supply their domestic water with larger quantities. civil and environmental science journal vol. ii, no. 01, pp. 067-075, 2019 75 2. the above discussions show that the implementation of rwh is an effective way to address future water shortage problems in indonesia. the simulations in this study indicate that the carrying capacity of rwh in a house can be improved by modifying the dimensions of the rwh facility. the parameters in the rwh design can be changed as needed. the irreversible parameter is the intensity of rainfall. 3. the economic ability of a family plays an important role in planning the dimensions of a rwh facility. rwh facilities with larger dimensions tend to produce a larger rwh carrying capacity. thus the availability of water will become more assured. 4. the intensity of rainfall will greatly affect the carrying capacity of rwh. rainfall intensity is a parameter that can be used as a reference in designing the dimensions of an rwh facility. in addition to rainfall, investment cost and space availability are the things to consider in planning the rwh dimension. 5. maintenance is an important part of rwh implementation. maintenance of rwh facilities on a regular basis will ensure the smooth operation of rwh. acknowledgements the authors wish to express their deep gratitude to the civil engineering department, university of lampung for their support in this research. the authors also wish to express their gratitude to the students involved in completing this research. references [1] united nation department of economic and social affair (undesa). 2014. water scarcity. united nation department of economic and social affair (undesa) article. website: http://www.un.org/waterforlifedecade/scarcity.shtml. [accesssed jan 25, 2019] [2] british broadcasting coorporation (bbc). 2018. water scarcity threatens 11 cities in the world, jakarta one of them. website: https://internasional.kompas.com/read/2018/02/12/16071851/ kelangkaan-air-ancam-11-city-in-the-world-jakarta-one only? page = all. [accesssed jan 27, 2019]. [3] khastagir, a. and jayasuriya, n. 2010. optimal sizing of rain water tanks for domestic water conservation. journal of hydrology, 381(3–4), pp. 181–188. [4] kahinda, j.m., taigbenu, a.e. and boroto, r.j. 2010. domestic rainwater harvesting as an adaptation measure to climate change in south africa. physics and chemistry of the earth, vol. 32(15-18), pp. 1050–1057. [5] susilo, g.e., yamamoto, k. and imai, t. 2011. the identification of rainwater harvesting potency in supporting freshwater availability under the effect of el nino. proceeding iwa – aspire international conference, october 2011, tokyo – japan. [6] susilo, g.e. 2015. experience in rainwater harvesting application at household scale in bandar lampung, indonesia. proceeding of the 1st young scientist international conference of water resources development and environmental protection, malang, 5-7 june 2015 [7] susilo, g.e., efendi, r., desmawati, e. and nalaralagi, a. 2017. promoting rainwater harvesting as an alternative of freshwater source for public sanitation. journal of asian institute of low carbon design (2017) [8] fewkes, a. 1999. the use of rainwater for wc flushing: the field testing of a collection system. building and environment, 34(6), 765–772. [9] fair, g.m., geyer, j.c. and okun, d.a. 1971. elements of water supply and wastewater disposal. second edition, john wiley & sons, inc. and toppan company, ltd., new york. [10] poedjiastoeti, h. and syahputra, b. 2006. determination of the maximum peak hour and daily maximums on the domestic water use pattern in kalasan, sleman, yogyakarta. proceeding of lecturer research, research institute of sultan agung university, yogyakarta, indonesia. http://www.un.org/waterforlifedecade/scarcity.shtml https://internasional/ open access proceedings journal of physics: conference series civil and environmental science journal vol. ii, no. 02, pp. 105-116, 2019 105 determination of pollution load capacity using qual2kw program on the musi river palembang handayani lestari1, riyanto haribowo2, emma yuliani2, 1environment and water resources division, nippon koei co., ltd, jakarta selatan, 12160, indonesia 2water resources engineering department, universitas brawijaya, malang, 65145, indonesia tariprojects@gmail.com received 23-07-2019; revised 12-08-2019; accepted 27-09-2019 abstract. the object of this research is a river named musi, located in palembang city, south of sumatera, which is one of the longest and the biggest river in indonesia. the condition of water quality in this river must be concerned because the high demand is not balanced with a good water quality. so, the aim of this study is to determine the value of the pollution load capacity, which is useful for consideration to government on water quality improvement policy. qual2kw is used as an application to calculate the pollution capacity which entered to each river segment. there are 3 scenarios in this study, simulation 1 is calibrated model, simulation 2 is maximum of pollutant load condition, and simulation 3 is minimum of pollutant load condition. the value of pollutant load capacity is obtained from the difference between simulation 2 and simulation 3. the results show that the pollution load capacity on musi river (particularly segment pulokerto – pt. baja baru) in 2016 sequentially 12948 kgdo/day, 25205 kgbod5/day, 3207 kg/ nh3-n day, 642 kg po4/day. keywords: water quality, pollution load, river, qual2kw 1. introduction musi river is one of the main river in south sumatra and widely used to meet the needs of the people of palembang. along the river with a length of 750 km and 300 meters wide stands a number of industries such as pt. hevea mk ii, pt. badja baru and many more [10]. over time, the number of residents in the city of palembang has increased, of about 1,5 million people [2], means that the need of clean water is around 1,9 million/l/person/day. the fact is, 70% water in musi river is contaminated by domestic waste, and 30% else contaminated by industrial waste [10]. the changes of land use around the musi river border that affect the condition of the water quality of the river itself. this situation raises concerns about the decline in water quality, considering the use and utilization of this river is so high [6, 8, 12]. therefore, the calculation of pollution load capacity is needed for the consideration to manage water quality improvement on the next policy of government [5, 11]. the first step to determine the value of pollution load capacity is collecting the water quality data, hydraulics data, and effluent which goes to the river [7]. nest is entering the data to worksheet of qual2kw. the result of this step is a model in graphical form. then the model has to be calibrated by trial and error the coefficient value civil and environmental science journal vol. ii, no. 02, pp. 105-116, 2019 106 [3]. based on the above problem, the aim of this study is to determine the value of the pollution load capacity. 2. material and methods the method in determining the pollution load capacity in this study is a computational method using qual2kw program. secondary data collected include maps, river water quality data, river hydraulic conditions, water quality point source, population of palembang city and meteorological conditions [4]. the water quality data, maps, river hydraulic condition, water quality source are obtained from sanitation and environmental offices. while the population data of palembang city is obtained from central agency of statistics. the next step is determining the segments. after the segment is reached, the data that has been obtained is then entered into the qual2kw program for model formation [1]. 2.1. segmentation in this study the musi river that will be examined is the start of the pulokerto to pt. new badja is about 7.1 km from the total length of kalimas of approximately 750 km. there will be 3 segments in this research. the division of this segment is based on input from the place for sampling, curves, changes in river dimensions and input from pollutant sources. 2.2. modelling after the data is entered and qual2kw is executed, the calibration is required to be able to process the model simulation. model calibration is done by altering the water quality coefficients at works sheet rates or reach rates. the model is said to have been verified if it has approached the data. this can be known from the trends formed by the model matching the trend formed by the data on the graph. 2.3. simulation calibrated models can be used to perform various simulation scenarios of river conditions. there are three simulation scenarios in this research. scenario 1 is a simulation of the result of forming the model according to the existing condition. scenario 2 is an existing data condition where the industrial waste consumption is assumed to have been processed so as to comply with the water quality standard of waste and also no domestic waste entering the river body. scenario 3 is a simulation where the state of the river is filled with pollutant load, where industrial waste and domestic waste enter the river body. 2.4. calculation of load pollution and load capacity pollution load capacity of river is obtained from scenario 2 and scenario 3. from each scenario is taken the data of the debit and pollutant concentration of simulation result from sources summary worksheet. then determine the value of pollutant load by multiplying the debit and pollutant concentration. the total river pollution load from scenario 2 and 3 then will be calculated to obtain the value of load capacity [9]. the calculation of pollution load is done by multiplying the large concertation into the river (mg/l) with the amount of river flow discharge (m/sec). the calculation of pollution load can be calculated by the following formula: pollution load (kg/day) = flow(m/s) x concentration (mg/l) x 86.4 3. result and discussion 3.1. segmentation this research will analyse musi river with length about 7.1 km from upstream (pulokerto) to downstream (pt. badja baru). in this case, the river is divided into 3 segments starting from upstream (kilometres 7.01) downstream (kilometres 0.0). this river segmentation is done for modelling purposes. the division of this segment is based on inputs from the tributaries, the location for sampling, turns, changes in river dimensions and input from pollutants. this is the basis of the segment determination to get 3 segments that can be seen in figure 1. elevation measurement using google earth help. segment division of research area in detail can be seen in table 1 below. civil and environmental science journal vol. ii, no. 02, pp. 105-116, 2019 107 table 1. segmentation of musi river palembang reach kilometer (from downstream) elevation upstream (m) downstream (m) (upstream) point 1 – point 2 7.1 – 5.05 4.88 3.96 point 2 – point 3 5.05 – 2.05 3.96 2.75 point 3 – point 4 2.05 – 0 2.75 2.15 3.1.1. reach 1, point 1 – point 2 (2.05 km) point segment 1 – point 2 is the first segment in the model formation for musi palembang. point 1 (upstream) is an agro-cultural area. while point 2 is an area that is not so far from the outlet of an industry called pt. hevea mk ii. the distance in this 1-2 segment is 2.05 km. this first segment is divided based on the input of the tributary to the musi river and also the input of waste from the industry. this area is dominated by agricultural fields, and plantation. it proved by the concentration of phosphate (po4) in point 1 is 0.90 mg/l, which is the highest number compared with the po4 in the other reaches. the average value of po4 in this area is around 0.75 mg/l, where the quality standard class ii permits the maximum value of po4 in some river is only 0.20 mg/l. moreover, the nh3-n value is also increased. it shows that the harmful toxicant begins to arised, about 0.41 mg/l to 0.56 mg/l. map of point 1 – point 2 can be seen in figure 1 figure.1. reach 1 (from pulokerto to pt. hevea mk ii) figure.2. reach 2 (from pt. hevea mk ii to musi ii bridge) 3.1.2. reach 2, point 2 – point 3 (3.00 km) segment point 2 – point 3 is the second segment in modelling for musi palembang. as mentioned earlier, point 2 is an area affected by the output of industrial waste (pt. hevea mk ii). while point 3 is musi ii bridge, where sampling is easy to do. the distance on this 2-3 segment is 3.00 km. this second segment is determined based on industrial waste input at point 2 and the easy access of water quality sampling at point 3. the value of do is begin to decreased, about 6.0 mg/l to 5.7 mg/l. in this reach. on the contrary, the bod5 value is begin to increased, about 4.1 mg/l to 4.4 mg/l. it can be conclude that the oxygen content is getting worse. it may cause by the affection from industrial waste water output, pt. hevea mk ii. the map of point 1 – point 2 can be seen in figure 2 below. 3.1.3. reach 3, point 3 – point 4 (2.05 km) segment point 3 – point 4 is the third segment in forming a model for musi palembang. point 3 as described previously, is musi ii bridge where access to sampling is easy to do. while point 4 is a region that is not so far from the outlet of an industry named pt. badja baru. the distance in this 3-4 segment civil and environmental science journal vol. ii, no. 02, pp. 105-116, 2019 108 is 2.05 km. this third segment is divided based on the easy access of water quality sampling at point 3 and also the industrial waste input at point 4. getting down to downstream, the oxygen content is also getting worse than before. the value of bod5 in point 3 is 4.23 mg/l, and in point 4 is 4.70 mg/l. it may be caused by domestic waste output and the affection of industrial waste output from the previous reach. map of point 1 – point 2 can be seen in figure 3 below. figure.3. reach 3 (jembatan musi ii to pt. badja baru) 3.2. model formation of qual2kw version 5.1 the stage of model formation is done after the segmenting step. the model formation of the musi river palembang will execute the hydraulics data of the musi river, and the water quality data of the musi river. the data that input to qual2kw version 5.1 worksheet included the general data on the river, such as river name, sampling time and so on, water quality data on headwater, segment data, point sources and diffuse sources (nonpoint sources) data hydraulic rivers (speed, depth and debut of the river), water quality data of water bodies (ph, bod, nh3-n, po4, and do), then supporting data such as cloud cover data, wind speed, and dew temperature. in modelling, non-source pollutant sources are industrial wastewater, where the drainage channels go directly to the musi river. the river quality parameters measured and modelled must be in accordance with the parameters in the qual2kw program, can be seen in the following table: table 2. water quality parameters in qual2kw program no parameter parameter name in qual2kw 1 ph ph 2 temperature (oc) temperature (oc) 3 do (mg/l) dissolved oxygen (mg/l) 4 bod5 (mg/l) cbod fast (mg/l) 5 cod (mg/l) generic constituent (mg/l) 6 tss (mg/l) iss (mg/l) 7 nh3-n(mg/l) nh4 (µg/l) 8 po4 (mg/l) inorganic p (µg/l) 9 no3 (mg/l) no3 (µg/l) 10 total coliform pathogen 3.2.1. calibration of hydraulic model before performing a scenario simulation, the already built model needs to be calibrated. model calibration is carried out by the data model approaching the input data that has been entered into the civil and environmental science journal vol. ii, no. 02, pp. 105-116, 2019 109 program due to time differences and variations of data. the calibration model is divided into 2 calibrations, that are calibration hydraulic data and calibration of water quality data. hydraulic data calibration is done by entering data of musi river (pulokerto – pt. badja baru) into qual2kw worksheet, headwater, reach, point sources (hydraulic data), diffuse sources (hydraulic data, hydraulics data, and temperature data) then input next click “run vba” to run and can be done trial and error for the model formed of hydraulic parameters in accordance with the inputted data. in conducting trial and error for the hydraulic, the changed data varies. models of speed and depth of musi palembang river are calibrated by changing the value on the worksheet reach. where on the worksheet is done trial and error on the column manning formula. the river flow model is influenced by both incoming and outgoing debit data into the musi river included in the worksheet point sources and diffuse sources. in conducting river flow model calibration, trial and error is performed on the diffuse source worksheet. in the worksheet reach there are coordinate data, distance, elevation, and hydraulic model. in the column hydraulic model there is a weir column, column rating curves and manning formula. the weir column is filled when there is a waterfall in a river, but in musi there is no plunge, so the weir column does not need to be filled. the rating curves and manning formulas are columns for determining calculations at the speed and depth of the stream. both models do not have to be filled both, but selected one of the models. the selected model is manning formula, this is because the value in manning formula is easier to use for river modeling in inputting data. in the manning column there is a data slope of the river, the coefficient of manning, and the width of the river. the musi river hydraulic data is inputted to the worksheet hydraulics data containing the debit data, depth, and speed, can be seen in table 3 and 4 below: table 3. worksheet reach hydraulic model (weir overrides rating curves; rating curves override manning formula) rating curves manning formula velocity depth channel manning bot width side side coefficient exponent coefficient exponent slope n m slope slope 1.6800 0.000 6.0000 0.000 0.000446 0.0700 419.00 0.00 0.00 1.4200 0.000 6.1500 0.000 0.000446 0.0700 464.00 0.00 0.00 2.0700 0.000 6.2000 0.000 0.000407 0.0180 330.00 0.00 0.00 1.8600 0.000 6.4700 0.000 0.000298 0.0160 279.00 0.00 0.00 table 4. worksheet hydraulics data distance q-data h-data u-data (km) m3/s m m/s 7.100 4337.490 6.000 1.680 5.050 3984.150 6.150 1.420 2.050 4952.710 6.280 2.070 0.000 2156.060 6.470 1.860 3.2.2. calibration of water quality model after the hydraulic data calibration model is in accordance with the desired data, then the next calibration of water quality data streams in each segment. in water quality calibration, data that has been inputted into wq data worksheet, point sources, diffuse sources, and supporting data such as air temperature, dew point temperature, wind speed, cloud cover, shade, and diesel. in calibrating the water quality data of the river, the data to be changed in value is the data on the worksheet reach rates. where on the worksheet is done trial and error on the coefficient of each parameter. range coefficient value of each parameter can be seen in table 5. the coefficient range is a corresponding number for rivers in a 4 seasons country. therefore, calibration is needed to adjust the civil and environmental science journal vol. ii, no. 02, pp. 105-116, 2019 110 appropriate coefficients for the musi river palembang. in doing this calibration there is a possibility that the coefficient value is outside the range in the table below, because the condition of each river will be different. table 5. coefficient value of calibration coefficient name unit value range reaeration day-1 0,02 – 3,4 iss settling velocity m/day 0 – 2 cbod oxidation rate day-1 0,02 – 4,2 nh4 nitrification rate day -1 0 – 10 no3 denitrification rate day -1 0 – 2 no3 sed. denitri transfer coeff. day -1 0 – 1 po4 settling velocity m/day 0 – 2 the fitness value is the control value generated when the qual2kw program finishes running. good fitness value is at susceptible 0 to 1. if more than that, there may be errors in the input data so as to make the fitness value more than 1. and in this research, the calibration obtained fitness value of 0.65. it means that the process of input data has already correct because the fitness value is still below to 1. the results of hydraulic calibration can be seen in the following figure below: figure 5. comparison of stream flow models and data figure 6. comparison of velocity models and data figure 7. comparison of depth models and data from figure 5, 6 and 7 above, the data trends in the graph above are indicated by dots, and the model trend is indicated by the line. it can be seen that the trend of debit model, trend of depth model, and trend of velocity of qual2kw running results is similar to the trend of existing data. 0,00 1000,00 2000,00 3000,00 4000,00 5000,00 6000,00 0246 fl o w ( m ^ 3 /s ) distance upstream (km) sungai musi (10/5/2016) q, m3/s 0,00 0,50 1,00 1,50 2,00 2,50 3,00 3,50 4,00 0246 v e lo c it y ( m /s ) distance upstream (km) sungai musi (10/5/2016) u, mps 0,00 1,00 2,00 3,00 4,00 5,00 6,00 7,00 8,00 9,00 01234567 d e p th ( m ) distance upstream (km) sungai musi (10/5/2016) h, m musi river musi river musi river civil and environmental science journal vol. ii, no. 02, pp. 105-116, 2019 111 3.3. water quality simulation 3.3.1. simulation 1 in simulation 1 it aims to calibrate water quality data to be used for other simulations. the results of this simulation obtained some parameters such as do, bod, nh3-n, and phosphate, with a variety of circumstances, some exceed the quality standard, while not. in doing this simulation 1 is done trial and error, for calibration of water quality data at worksheet reach rates. figure 8. comparison of dissolved oxygen (do) models and data figure 9. comparison of biological oxygen demand (bod5) models and data figure 10. comparison of ammonia nitrogen (nh3-n) models and data figure 11. comparison of phosphate (po4) models and data based on the results of simulation 1, it can be seen that the trend of do model running qual2kw is similar to the existing data trend do. the value of do increasingly downstream tends to decrease. but, the value of bod5 increasingly to the downstream tend to increase. this condition is in contrast to the previous do value. and it can be seen that nh3-n model trend and trend of phosphate of qual2kw running result is similar to existing data trend. 3.3.2. simulation 2 simulation 2 is a condition where trial and error at point source up to downstream water quality value in accordance with the limit of class ii water quality standard. the quality standard in use is government regulation no. 82. 2001 [10]. the profile of river water quality can be seen in figure 12 to figure 15. this quality profile is intentionally made to meet the quality standard. the assumption made is the amount of pollution load. the results of this simulation can be used to calculate the pollution load capacity, i.e. the amount of load that may be discharged into the river without causing polluted river water (not exceeding the quality standard). civil and environmental science journal vol. ii, no. 02, pp. 105-116, 2019 112 figure 12. water quality profile of musi river parameters do simulation 2 figure 13. water quality profile of musi river parameters bod5 simulation 2 figure 14. water quality profile of musi river parameter nh3-n simulation 2 figure 15. water quality profile of musi river parameter po4 simulation 2 the results of simulation 2 is a high value of do. this means that there is still a lot of oxygen content in the waters of the river musi point pulokerto up to pt. new badja. the value of do tends to fall from point 2 to point 4, where from point 2 there begins waste discharges from 2 major industries of crumb rubber. where the bod5 value is still above the quality standard. bod5 value is also higher towards downstream, this condition is in contrast to the previous do condition which actually decreased. in simulation 2, the waste discharge load is fully loaded, so the value of bod5 value is quite significant compared to simulation 1. then the value of nh3-n is also below from the quality standard value. nh3-n or commonly called ammonia nitrogen is a parameter that can be an indicator of ammonia toxicity that may harm aquatic life. it means the output of fisheries produced in vulnerable pulokerto pt. badja baru is still safe from aquatic disease because it is still below the standard value. and the reason why the po4 value is above from the standard quality may because there’s still an influence from the fertilizer of agricultural area. the highest phosphate value still exists in the first point, namely the point of pulokerto where the area is indeed dominated by plantations and agriculture. 3.3.3. simulation 3 the simulation 3 is done by eliminating pollutant load (point source), and data in headwater according to class ii quality standard. similarly, non-point source quality is considered good, equal to the quality standard of waste water. under conditions without input this pollution load, can know the amount of the minimum river pollution load burden with the maximum contamination load according to the quality standard. the results of simulation 3 can be seen in figure 16 to figure 19. the simulation results show that the removal of pollution sources along the river, the water quality of the meet the quality standards in all segments. civil and environmental science journal vol. ii, no. 02, pp. 105-116, 2019 113 figure 16. water quality profile of musi river parameters do simulation 3 figure 17. water quality profile of musi river parameters bod5 simulation 3 figure 18. water quality profile of musi river parameter nh3-n simulation 3 figure 19. water quality profile of musi river parameter po4 simulation 3 based on the result of simulation 3, that the value of do is above the standard. the value of do tends not to increase significantly or decrease significantly. in the simulation 3 is in the condition of the load discharged of waste considered no entry into the river body. then the value of do so tend to be constant. whereas, in bod5, nh3-n, and po4 graphic, the value is below from the standard. the condition of bod5 is different when compared with the condition of bod5 in simulation 2 which in overall value is above the standard. this is due to the effect of discharge of waste discharges entering the river body, so the bod5 condition in simulation 3 is better than the condition in simulation 2. in nh3-n graphic, the value is also below from the standard. indeed, when compared with the simulation 2, still equally below the quality standard because it is in the existing conditions even the value of ammonia nitrogen is not too high. however, by weight of the numbers, the nitrogen ammonia value in simulation 3 remains lower than the simulation 2. of course this has its effect from discharging the waste discharge load. the smaller the value of ammonia nitrogen the less likely the fish or biota in the river is poisoned. and for po4, there is a significant decrease of phosphate starting from the 2nd point, because the waste discharges in the river body are increasingly to downstream is industrial and domestic waste. 3.3.4. simulation 4 in simulation 4, will try to influence the discharge of water quality on point pulokerto to pt. badja baru. the maximum and minimum debit data to be used is the maximum discharge data available throughout the study site (pulokerto-pt badja baru). maximum and minimum debit data in the input on the headwater worksheet alternately to determine the effect that occurred. civil and environmental science journal vol. ii, no. 02, pp. 105-116, 2019 114 figure 20. water quality profile of musi river parameters do simulation 4 figure 21. water quality profile of musi river parameters bod5 simulation 4 figure 22. water quality profile of musi river parameter nh3-n simulation 4 figure 23. water quality profile of musi river parameter po4 simulation 4 3.4. calculation of pollution load capacity from the data of the simulation of water quality, the data is used to calculate the capacity of pollution load on the musi river from the pulokerto segment to pt. new badja. the calculation of the pollution load capacity will use the data generated on the source summary worksheet which is the result of the calculation of debit pollution load and the water quality of each segment. the calculation of the pollution load capacity using simulation 2 and 3, based on the results of the two simulations will be obtained the calculation of load pollution capacity by the difference of simulation result 2 (full pollution load) and simulation 3 (load without pollution). the source summary table for simulation 2 can be seen in table 6. whereas, for the source summary for simulation 3, the overall result is 0, because in simulation 3 assumed that there’s no pollutants enter to the river. then, the calculation of pollution load is obtained from multiplication of inflow and concentrations value on each parameter. these calculations of pollution load on each parameter can be seen in table 7 to 11. table 6. result source summary simulation 2 inflow temp cond iss oxygen cbods cbodf no nh4 no3 po inorg p cms c us/cm 25c mgd/l mgo2/l mgo2/l mgo2/l ugn/l ugn/l ugn/l ugp/l ugp/l 28.47 15.00 600.00 0.00 2.00 1.00 4.00 500.00 500.00 2000.00 100.00 100.00 36.08 15.05 599.56 0.03 2.03 1.00 3.99 498.13 498.13 1992.52 9.63 9.63 9.85 15.00 600.00 0.00 2.00 1.00 4.00 500.00 500.00 2000.00 100.00 100.00 table 7. calculation of pollution load, parameters do reach km flow (m/s) do (mg/l) pollution load – do (kg/day) 1 7.1-5.05 28.47 2.00 4920.00 2 5.05-2.05 36.08 2.03 6327.69 3 2.05-0 9.85 2.00 1702.08 civil and environmental science journal vol. ii, no. 02, pp. 105-116, 2019 115 table 8. calculation of pollution load, parameters bod5 reach km flow (cm/s) bod5 (mg/l) pollution load – bod5 (kg/day) 1 7.1-5.05 28.47 4.00 9840.00 2 5.05-2.05 36.08 3.99 12421.71 3 2.05-0 9.85 4.00 3404.17 table 9. calculation of pollution load, parameter nh3-n reach km flow (m/s) nh3-n (mg/l) pollution load – nh3-n (kg/day) 1 7.1-5.05 28.47 0.50 1230.00 2 5.05-2.05 36.08 0.49 1552.71 3 2.05-0 9.85 0.50 425.52 table 10. calculation of pollution load, parameter po4 reach km flow (m/s) po4 (mg/l) pollution load – po4 (kg/day) 1 7.1-5.05 28.47 0.100 246.000 2 5.05-2.05 36.08 0.099 310.542 3 2.05-0 9.85 0.100 85.104 table 11. pollution load capacity in musi river reach km do (kg/day) bod5 (kg/day) nh3-n (kg/day) po4 (kg/day) 1 7.1-5.05 4920.00 9840.00 1230.00 246.00 2 5.05-2.05 6327.69 12421.71 1552.71 310.54 3 2.05-0 1702.08 3404.17 425.52 85.10 from the table above, can be seen that the largest capacity in the musi river is in the segment (reach) 2 on each parameter. the potential source of pollution load in this segment comes from industrial and domestic waste (household) waste. the amount of pollution load capacity that has been obtained in this study results at any time may change but the changes are not so significant. the difference can be caused by the increasing amount of incoming waste, the number of segments, and the seasonal differences. figure 24. pollution load capacity, musi river pulokerto-pt.badja baru) 4. conclusions the parameter of water quality which simulated are do, bod5, nh3-n, and po4. determination of river pollution load capacity can be done with several methods, one of which is computation method using qual2kw program. this computer program works by analysing the simulation results of the river 1,5 2001,5 4001,5 6001,5 8001,5 10001,5 12001,5 14001,5 1 2 3 load capacity do load capacity bod5 load capacity nh4 load capacity po4 p o ll u ti o n l o a d c a [a c it y (k g /d a y ) reac civil and environmental science journal vol. ii, no. 02, pp. 105-116, 2019 116 water quality model. determination of pollution load capacity of musi river in pulokerto pt. new badja concluded that the capacity of pollution load of the river is still quite large with the capacity value as follows: 12,948 kgdo/day, 25,205 kgbod5/day, 3,207 kg/nh3-n day, 642 kgpo4/day.based on the result of application running, we can analyse and know the indicator numbers of each parameter to calculate the popullation load capacity. and for the future, this application can be used to see the quality of water river or the spread of pollution loads that exist. therefore, by knowing the existing pollution capacity we can know which segments of the river that need improvement for the future. references [1] brown, l.c., barnwell, t.o., 1987. the enhanced stream water quality models qual2e and qual2e-uncas (epa/600/3-87-007). u.s. environmental protection agency, athens, ga, pp 189. [2] central agency of statistics. 2016. palembang in numbers. palembang. (in bahasa indoensia) [3] chapra, s.c., pelletier, gj (2003) qual2k: a modeling framework for simulating river and stream water quality (beta version): documentation and users manual. civil and environmental engineering dept., tufts university [4] hoesein. a. 1984. water quality and irrigation system; faculty of engineering. universitas brawijaya. malang. (in bahasa indonesia) [5] metcalf & eddy. 2003. wastewater engineering :treatment disposal reuse. mcgraw-hill,inc. new york. [6] mitsch & gosselink. 1994. wet land, in water quality prevention, identification and management of diffuse pollution. van nostrand reinhold,.new york [7] ray k. linsey, franzini , joshep b. 1991. water resources engineering ; erlangga. jakarta. (in bahasa indonesia) [8] riyanto h, minami y, masahiko s, tsuyoshi i, koichi y, takaya h, ariyo k 2017 behavior of toxicity in river basins dominated by residential areas contemporary engineering sciences 10 (7), 305-315. [9] rusnugroho, a. 2012. qual2kw as a program for calculating the pllution load capacity in madiun city. (in bahasa indonesia) [10] sanitation and enviromental offices. 2016. water quality parameter. palembang. (in bahasa indonesia) [11] sugiharto. 1987. fundamentals of wastewater management; ui press. jakarta. (in bahasa indonesia). [12] yamashita h, haribowo r, sekine m, oda n, kanno a, shimono y 2012 toxicity test using medaka (oryzias latipes) early fry and concentrated sample water as an index of aquatic habitat condition environmental science and pollution research 19 (7), 2581-2594. open access proceedings journal of physics: conference series civil and environmental science journal vol. 05, no. 02, pp. 171-182, 2022 171 comparison of spt and vs-based liquefaction assessment on young volcanic sediment: a case study in bantul district of yogyakarta, indonesia. anisa nur amalina 1,4, teuku faisal fathani 2,4, wahyu wilopo 3,4 1 department of civil engineering, faculty of civil engineering and planning, islamic university of indonesia, indonesia 2 department of civil and environmental engineering, faculty of engineering, universitas gadjah mada, yogyakarta, indonesia 3 department of geological engineering, faculty of engineering, universitas gadjah mada, yogyakarta, indonesia 4 center for disaster mitigation and technological innovation (gama-inatek) universitas gadjah mada, yogyakarta, indonesia corresponding author's e-mail: amalina.anisa@gmail.com received 01-07-2022; accepted 27-09-2022 abstract. on may 26, 2006, an earthquake of moment magnitude (mw) 6.3 occurred in yogyakarta. the damages found in bantul were predicted to be caused by liquefaction. moreover, liquefaction symptoms were found, such as a sand boil and lateral spreading. it inferred that the damage was controlled by the amplification factors from young redeposited volcanic sediments and altered volcaniclastics from the active mount merapi. this study compared subsurface conditions based on two field investigation methods (spt and shear wave velocity) and determined the liquefaction potential by considering groundwater and the region's seismicity. to obtain the most fitted equation, several equations to represent the n-spt and vs data were also analyzed. as a result, several equations used in this study were inadequate to correlate n-spt and vs properly. a comparison of safety factor values indicated that the liquefaction potential in the studied area on the vs-based method is lower than the result from the spt-based method. keywords: shear wave velocity, downhole test, n-spt value, liquefaction potential. 1. introduction a strike-slip earthquake happened on may 26, 2006, in yogyakarta. approximately 5,700 people were killed, and over 156,000 houses and other structures were destroyed. the magnitude was 6.3, and its duration was about 60 seconds, with the hypocenter at the east of the opak river [1, 2]. northeast of the parangtritis, the bantul and klaten are the most affected area [3]. meanwhile, heavy losses were founded near the opak fault was due to the amplification factors from soft sediments redeposited from the active mount merapi [4, 1]. mailto:amalina.anisa@gmail.com civil and environmental science journal vol. 05, no. 02, pp. 171-182, 2022 172 besides damaging hundreds of houses, the earthquake destroyed university and school buildings, offices, infrastructures, and the runway at adi sutjipto international airport. additionally, liquefaction symptoms were detected, such as sand boils and lateral spreading. the area with the highest potential for liquefaction is patalan, bantul, part of the bantul basin, or the opak river fault basin [5]. evaluating soil liquefaction is crucial to minimize future damage, especially in earthquake-prone regions. the method mainly used is the simplified procedure [6], originally developed from the standard penetration test (spt) and correlated with a cyclic stress ratio parameter representing the cyclic soil loading. meanwhile, the most common approach is in-situ vs measurements [7]. vs is a field measurement with less than 10−4% strain [[8], [9]]. the vs-based liquefaction analysis has obtained considerable relevance compared to spt-based analysis. furthermore, vs and liquefaction resistance are sensitive to relative density, effective stress, and cementation in the same direction [10]. this study aims to compare subsurface conditions based on two field investigation methods (spt and shear wave velocity) and determine the liquefaction potential by considering groundwater and the region's seismicity. furthermore, a comprehensive analysis of liquefaction potential on young volcanic sediment was conducted by comparing the n-spt and vs values. 2. methodology the initial stage of this study involves seismic and geotechnical data compilation from the previous research, field test, and desk study. next, the collected data were analyzed to determine the site classification, soil stratigraphy, and soil parameters. groundwater and the region's seismicity were considered to calculate the potential of liquefaction. the liquefaction analyses were conducted using the spt method [14] and vs measurement [6, 16, 17]. furthermore, a comprehensive analysis of n-spt relationships with vs on young volcanic sediment was explained further. 2.1. geological conditions the study was conducted in the bantul region of yogyakarta, indonesia. bantul is considered earthquake-prone due to its proximity to the eurasian plate's subduction and the australian plate). furthermore, based on rahardjo et al. [11], the bantul region consists of quaternary young merapi volcano deposits (qmi) that have a high potential to liquefy (figure 1) deposits in the quaternary period are divided into holocene and pleistocene, while deposits older than the pleistocene are included in the tertiary period. the tertiary period comprised the kulon progo mountains and the southern mountains. meanwhile, most of the quaternary deposits compose yogyakarta and bantul. the lithology of the young merapi volcano deposits can be classified based on grains size distribution, namely 1) sand sediment, the most dominant sediment, consists of sand, silt sand, and gravel sand, 2) silt deposits, and 3) clay sediment consists of sandy clay and clay [12]. the microtremor survey was conducted in several severely damaged locations by the 2006 earthquake [13]. the result shows that the depth of bedrock in bantul area is approximately 30–60 meters. meanwhile, the deepest bedrock, around 60–100 meters, lay in the east bantul. in jetis, imogiri, and pundong, a breccia layer reaches 50 meters in thickness. 2.2. site classification besides soil stratigraphy, site classification was also conducted. the classification was based on the average value of n-spt and vs until a depth of 30 m. the site classification can be seen in table 1. site classification is commonly used to define the peak ground acceleration (pga) value by determining the seismic zones. meanwhile, this study applied the pga value referred to fathani et al. [17], where the research location was also conducted in bantul. they calculated the pga value using an attenuation relationship considering two scenarios of epicenter coordinate and hypocenter depth based on the indonesia meteorological, climatological, and geophysical agency (bmkg) and the united states geological survey (usgs). the results are summarized in table 2. civil and environmental science journal vol. 05, no. 02, pp. 171-182, 2022 173 figure 1. the location and geological condition of the study area (modified from [11]). table 1. comparison of pga based on two scenarios [17]. site class sv (m/s) 30n se (soft soil) <175 <15 sd (medium soil) 175 to 350 15 to 50 sc (hard/very dense soil and soft rock) 350 to 750 >50 sb (rock) 750 to 1500 n/a sa (hard rock) >1500 n/a sf (special soil) required specific geotechnical investigation and site response analysis on every site table 2. comparison of pga based on two scenarios [17]. sample location pga (g) bmkg usgs bh-01 bpkp-1 0.24 0.25 bh-02 bpkp-2 0.24 0.25 bh-03 segoroyoso 0.25 0.30 bh-04 karangsemut 0.26 0.30 bh-05 wijirejo 0.28 0.24 bh-06 bambanglipuro 0.32 0.26 bh-07 pranti 0.30 0.30 bh-08 tempuran kali opak-oyo 0.30 0.30 bh-09 watu 0.32 0.27 2.3. n-spt and vs empirical correlation for young sediment volcanic the data applied in this study are collected from an extensive geotechnical borehole, downhole and laboratory tests. the data consist of 29 boreholes and nine shear wave velocity data. the data depths vary from 20 m to 50 m (figure 2). nine borehole and downhole data were used to calculate the liquefaction potential by comparing those data. meanwhile, the other available data were used to generate soil stratigraphy. civil and environmental science journal vol. 05, no. 02, pp. 171-182, 2022 174 figure 2. the location and geological condition of the study area (modified from [11]). several equations in table 3 correlate the n-spt value with shear wave velocity (vs) in various types of soils. the selected equation was then used to define vs value in young sediment volcanic. table 3. comparison of pga based on two scenarios [17]. author equation seed and idriss [6]: ( ) 0.5 s 61.4v n= (1) hasancebi and ulusay [19]: ( ) 0.39 s 90v n= (2) imai and yoshimura [20]: ( ) 0.33 s 76v n= (3) kanai [21]: ( ) 0.6 s 19v n= (4) akin et al. [22]: ( ) 0.101 0.216 s 121.75 ( )v n z − = (5) alluvial sands [23]: ( ) 0.292 s 87.8v n= (6) alluvial soils (korea) [23]: ( ) 0.319 s 82v n= (7) 2.4. liquefaction safety factor (fs) parameters that need to be reviewed regarding liquefaction are the earthquake loading and soil strength against earthquake loading. the safety factor is calculated by comparing the cyclic stress ratio (csr) and the cyclic resistance ratio (crr). liquefaction might happen if the crr is less than crr. the safety factor of the liquefaction is 1.2 [24]. referring to pawirodikromo et al. [25], the de-aggregation results found that the dominant magnitude and the distance were influenced mainly by the shallow crustal instead of the megathrust earthquak e source. the md= 6.5 and the rd= 14.5 km. the opak river fault is located approximately 10 km from yogyakarta, while the megathrust earthquakes, with a larger magnitude, are located more than 300 km from yogyakarta. thus, the moment magnitude of 6.5 is used to calculate msf (eq. (8)). msf 6.9 exp 0.058 4 wm      − = − (8) civil and environmental science journal vol. 05, no. 02, pp. 171-182, 2022 175 2.4.1. spt-based liquefaction safety factor (fsl) the safety factor is calculated by the cyclic stress ratio (csr) and the cyclic resistance ratio (crr 7.5), as shown in eq. (9). the csr value is adjusted to a specific earthquake magnitude (mw=6.5) by a magnitude scaling factor (msf). 7.5 l crr fs msf csr = (9) 2.4.2. vs-based liquefaction safety factors (fsvs) fsvs is calculated using equation given by [6], [15], and [16]. the equation is generally considering both spt and vs data. s s s crr srr fs csr ssr v v v = = (10) 2.5. cyclic stress ratio (csr) the csr due to earthquake force is usually explained as 0.65 multiplied by the peak value of cyclic shear stress at a particular depth (z). several parameters, such as surface acceleration and total and effective stresses at different depths, are considered in determining the csr. 2.5.1. spt-based liquefaction triggering analysis (csr) the liquefaction triggering analysis proposed by idriss and boulanger [14] is based on trial and error (n1)60cs. the soil is unlikely to liquefy if the clean granular soils or (n1)60cs value is larger than 30 blows/ft. seed and idriss [6] calculated the induced stress ratio csr as shown in eqs. (11) to (14). σav is the 65% of the peak induced cyclic shear stress triggered by an earthquake, pga or amax is the peak ground acceleration at the site, g is the acceleration of gravity, rd is a depth factor, σv is the initial total vertical stress, and σ’v0 is the initial vertical effective stress in the ground. max ' ' csr 0.65 vav d v v a r g       = =       (11) ( ) 1.012 1.126sin 5.133 11.73 zz               = − − + (12) ( ) w 0.106 0.118sin 5.1242 11.28 zz m               = + + (13) ( )wd exp ( ) ( )r z z m = + (14) 2.5.2. vs-based liquefaction triggering analysis (ssr) the csr parameter is changed into a shear stress ratio (ssr) in the vs-based method. however, they have similar physical meanings. the shear stress ratio depends on the soil medium, unit weight, acceleration, and earthquake period [16]. eqs. (15) to (17) show several parameters. first, t is a predominant period of the earthquake wave. for example, the dominant vibration period suggested for m6.5 is 0.280s [15]. max s ' s ssr v d v a r g       =       (15) ( )s 10.25 n v i s ii t v  = =  (16) ( )s s sa ds i n10.25 ( ) n v i i t v v    =  = − − (17) civil and environmental science journal vol. 05, no. 02, pp. 171-182, 2022 176 the amax refers to the maximum horizontal ground acceleration (m/s 2), g is the gravitational acceleration (m/s2), σvs is the dynamic vertical stress (kn/m 2), σ′vs is the effective dynamic vertical stress at the same depths calculated by the same parameters (kn/m2), and rd is the stress reduction coefficient mentioned in eqs. (12) to (14). 2.6. cyclic resistance ratio (crr) soil resistance or crr is soil's capacity at a particular depth and state to resist liquefaction triggering liquefaction resistance is generally characterized by penetration resistance modified to account for various additional variables that can affect liquefaction resistance. 2.6.1. spt-based liquefaction resistance analysis (crr) the csr parameter is changed into a shear stress ratio (ssr) in the vs-based method. however, they have similar physical meanings. the shear stress ratio depends on the soil medium, unit weight, acceleration, and earthquake period [16]. the liquefaction safety factor can be calculated with widely used methods such as n-spt data and corrected with five correction factors as given by [14]. the value of clean sand, (n1)60cs, is then obtained by adjusting the fc (fines content) to the corrected blow count. the empirical procedures to obtain the corrected spt values based on idriss and boulanger [14] are shown in eqs. (18) to (21). meanwhile, the spt-based crr relationships are presented in eqs. (22) to (25). ( ) 601 60 n e b r sn n c c c c c= (18) ( )0.784 0.0768 1 60 n ' c 1.7 n a v p  − =        (19) ( ) 2 1 60 9.7 15.7exp 1.63 fc 0.01 fc 0.01 n                = + − + + (20) ( ) ( ) ( )1 1 160 60 60csn n n= +  (21) ( ) ( ) ( ) ( ) 2 3 4 1 60 1 60 1 601 60 ' 1 crr exp 2.8 14.1 126 23.6 25.4 cs cs cscs atm n n nn                      =                = + − + −       (22) ' ' 1 crr crr atm k   = = (23) ' 1 ln min 1.0 vo a c k p    − =              (24) 1 60 1 18.9 2.55 ( ) cs c n  = − (25) 2.6.2. vs-based liquefaction triggering analysis (ssr) the shear wave velocity was formulated from more than 50 sites measurement as shear resistance ratio (srr) and determined by corrected vs and maximum vs (vs, max) value, as shown in eq. (26) [26]. for values of corrected shear waves in the range of 190 to 220 m/s, the curve turns upward sharply where minor changes in vs1 correspond to significant changes in crr. the correlation between crr and vs of uncemented holocene-age soils shows in figure 3 [7]. civil and environmental science journal vol. 05, no. 02, pp. 171-182, 2022 177 s c s s s max c max 2 1 1 srr msf 100 v a b v v v       = + −     −      (26) figure 3. correlation between crr/csr and vs [7]. uyanık and taktak [15] determined that vs-max ranges from 220 to 250 m/s based on the fines content. meanwhile, the a and b values are 0.022 and 2.8. several researchers [27] suggested the corrected vs formula as shown in eqs. (27) to (28). the reference stress or atmospheric pressure (pa) is 100 kn/m 2. max max max 250 m/s, fc 5% 250 (fc 5) m/s, 5% fc 35% 220 m/s, fc 35% s s s v v v =  = − −   =  (27) 0.25 s s 'c a v p v v  =       (28) 3. result and discussion 3.1. soil classification soil classification was conducted by calculating the average value of n-spt and vs. data less than 30 m were approached by the nearest borehole n-spt values. table 4 shows a summary of site classification according to [18]. the results show that all soils are considered medium soils. in contrast, several locations (bh-03, bh-04, bh-08, and bh-09) are considered soft soil from the vs-based calculation. consequently, this difference will affect the results of the fs calculation. in addition, it might occur due to the uncertainties in downhole field performance. table 4. site classification based on spt and vs. sample location depth (m) soil classification spt vs bh-01 bpkp-1 30 sd sd bh-02 bpkp-2 20 sd sd bh-03 segoroyoso 46 sd se bh-04 karang-semut 20 sd se bh-05 wijirejo 46 sd sd bh-06 bambang-lipuro 50 sd sd bh-07 pranti 40 sd sd bh-08 kali opak-oyo 30 sd se civil and environmental science journal vol. 05, no. 02, pp. 171-182, 2022 178 bh-09 watu 34 sd se notes: sd = medium soil; se = soft soil 3.2. borehole stratigraphy a total of 23 data were analyzed to interpret the soil stratigraphy. the bedrock depth was estimated from the previous research by perdhana and nurcahya [13]. the soil layers are divided into fine sand, medium to coarse sand, silt to clay, breccia, medium to fine sandstone, and bedrock. the a-a' crosssection is made as long sections from north to south while the b-b' is cross-sections from west to east (figure 2). the borehole data show that fine sand, classified as the lithology of the young merapi volcano deposits, dominates the upper layer up to 20 m depth. beneath the 20 m, the soil layer is composed of fine to medium sandstone layers. figure 4 and figure 5 present an interpretation of the soil layer. this interpretation is coherent with the research of buana and agung [12], where fine sand dominates the area around the east of bantul. in addition, in the watu area, imogiri and karangsemut consist of a breccia layer. figure 4. soil stratigraphy of cross-section a-a′. figure 5. soil stratigraphy of cross-section b-b′. 3.3. n-spt and vs correlation table 5 shows that the given equations cannot adequately represent the n-spt and vs correlation. generally, the equation by akin et al. [22] gives the most insignificant error compared to the other equations. in addition, the error value of bh-04 tends to be small by applying the equation intended for alluvial sediments. table 5. summary of relative error for each equation. location relative error, er (%) eq. 1 eq. 2 eq. 3 eq. 4 eq. 5 eq. 6 eq. 7 bh-01 120 75 58 58 23 62 65 bh-02 166 108 88 56 21 92 96 bh-03 148 88 71 58 30 73 78 bh-04 78 36 37 47 47 34 34 bh-05 232 149 108 161 34 107 115 bh-06 277 182 156 66 67 159 166 civil and environmental science journal vol. 05, no. 02, pp. 171-182, 2022 179 location relative error, er (%) eq. 1 eq. 2 eq. 3 eq. 4 eq. 5 eq. 6 eq. 7 bh-07 209 188 136 217 50 145 147 bh-08 134 96 62 111 35 65 68 bh-09 175 115 79 127 27 79 85 the previously published research mainly used statistical relation to represent vs and n60 without considering confining stress. as a result, the graphs (figure 6) show significant errors in the equations that neglect confining stress (z). meanwhile, the other equations tend to be overestimated compared to the field test. hence, the effects of confining stress should be considered to minimize bias and reduce uncertainty. figure 6. n-spt and vs correlation based on given equations. 3.4. liquefaction analyses the liquefaction analysis was carried out based on two methods (n-spt and vs-based) by considering the largest acceleration value taken from fathani et al. [17]. figure 7 presents the analysis result from those methods. vs-based results tend to be much lower than the spt-based method. the site classification has identified this condition, where some boreholes are classified as soft soil instead of medium soil. the formula given by idris et al. [14] is susceptible to (n30)cs and fc values, where a value greater than 30 might result in an fs value greater than 2. in contrast, the vs-based results cannot identify these conditions. therefore, it aligns with ghazi et al. [27], where the vs values decrease mainly caused by the void ratio, while the grain size distribution and relative density do not affect them. civil and environmental science journal vol. 05, no. 02, pp. 171-182, 2022 180 figure 7. fs comparison based on two methods. 4. conclusions the present study intended to compare the liquefaction potential from spt and vs tests. those methods provide slightly different results. indonesian code of sni 8460:2017 [18] was used to determine the soil classification. several locations showed different results, such as on bh-03, bh-04, bh-08, and bh-09. based on spt data, the soil is classified as medium sand, while in vs -based, it is classified as soft soil. several equations in this study are inadequate to deliver a good correlation between n-spt and vs. the error value varies between 30 200%. however, the equation by akin et al. [22] gave the smallest error number. therefore, additional borehole and downhole tests must be carried out in the study area to determine the most compatible equation for the young volcanic sediment. the comparison of the safety factor values indicated that the liquefaction potential in the studied area on the vs-based method is lower than the result from the spt-based method. such differences may occur due to the errors and uncertainties in both borehole and downhole field performance. references [1] usgs preliminary earthquake report, the website of united statesgeological survey, earthquake hazards program, (available athttp://earthquake.usgs.gov/eqcenter/eqinthenews /2006/usneb6/), 2006. [2] a.s. enashai, s.j. kim, g.j. yun, and d. sidarta, the yogyakarta earthquake of may 27 2006. mid-american earthq. center, un. of illinois at urbana champaign, 2006. [3] h.z. abidin, h. andreas, t. kato, t. ito, i. meilano, f. kimata, d.h. natawidjaya, and h. harjono, "crustal deformation studies in java (indonesia) using gps," j. earthq. tsunami, vol. 3, pp. 77–88, 2009. civil and environmental science journal vol. 05, no. 02, pp. 171-182, 2022 181 [4] t.r. walter, r. wang, m. zimmer, h. grosser, b. luhr, and a. ratdomopurbo, volcanic activity influenced by tectonic earthquakes-static and dynamic stress triggering at mount merapi. geophysical research letters, 34. 2007. [5] e. soebowo, a. tohari, and d. sarah, "liquefaction potential due to earthquake based on cpt and n-spt data in patalan region bantul, yogyakarta," j. geol. and min. resc, vol. 19, no. 2, pp. 85-97, 2009. [6] h.b. seed and i.m. idriss, "simplified procedure for evaluating 255 soil liquefaction potential." j. soil mech. found. div., vol. 97, pp. 1249–1273, 1971. [7] r. d. andrus and k. h. stokoe, "liquefaction resistance of soils from shear-wave velocity," j. geo. geoenv. eng., vol. 126, no. november, pp. 1015–1025. 2000. [8] r. d. andrus, k. h. stokoe, and c.h juang, "guide for shear-wave based liquefaction potential evaluation," earth. spec., vol. 20, pp. 285–308, 2004. [9] el-sekelly, t. abdoun, r. dobry, "centrifuge modeling of the effect of preshaking on the liquefaction resistance of silty sand deposits," j. geo. geoenv. eng., vol. 142(6):04016012, 2016. [10] k. tokimatsu and a. uchida, "correlation between liquefaction resistance and shear wave velocity," soils found., vol. 30 (2), pp. 33–42, 1990 [11] w. rahardjo, sukandarrumidi, and h.m.d. rosidi, geological map of yogyakarta sheet jawa. (bandung: geological research and development centre), 1995. [12] t.w. buana and m.w. agung, "liquefaction characteristic based on ground response linier equivalent analysis and cyclic stress concept on young merapi volcanic deposit in bantul," j. jap. soc.eng. geo., pp. 1–5, 2015. [13] p. radhitya and b. nurcahya, "seismic microzonation based on microseismic data and damage distribution of 2006 yogyakarta earthquake," e3s web of conferences. 76. 03008, 2019. [14] i. m. idriss and r. w. boulanger, soil liquefaction during earthquakes. earthquake engineering research institute. ca, 2008. [15] o. uyanik and a.g. taktak, a new method for liquefaction analysis from shear wave velocity and active vibration period. sdu, science and technology. ins. magazine 13 (1), 74– 81, 2009. [16] o. uyanik, b. ekinci, and n.a. uyanik. "liquefaction analysis from seismic velocities and determination of lagoon limits kumluca/antalya example," j. app. geo., vol. 95, pp. 90–103, 2013 [17] t.f. fathani, a.d. adi, s. pramumijoyo, and d. karnawati. “the determination of peak ground acceleration at bantul regency, yogyakarta province, indonesia,” the yogyakarta earthquake may 27, 2006, pp. 1–15, 2008. [18] ministry of public works republic of indonesia, national standard of seismic design for building structure (sni 8460:2017), (jakarta: indonesian national standard). 2017. [19] n. hasancebi and r. ulusay, "empirical correlations between shear wave velocity and penetration resistance for ground shaking assessments," bulletin of engineering geology and the environment, vol. 66, pp. 203–213, 2006. [20] t. imai and m. yoshimura, "the relation of mechanical properties of soils to pand s-waves velocities for soil in japan," urana research institute, oyo corporation, tokyo, 1976. [21] k. kanai, "semi-empirical formula for the seismic characteristics of the ground motion," bulletin of the earthquake research institute, vol. 35, no. 2, 1957, pp. 309-325. [22] m.k. akin, s. kramer, and t. topal, "empirical correlations of shear wave velocity (vs) and penetration resistance (spt-n) for different soils in an earthquake-prone area (erbbaturkey)," j. eng geology, vol. 119, pp. 1-17, 2011. [23] w. a. prakoso, a. rahayu, i.a. sadisun, a.s. muntohar, m. muzli, dan a. rudyanto, "comparing shear-wave velocity determined by masw with borehole measurement at merapi sediment in yogyakarta," int. j. technol., vol. 6, pp. 993–1000, 2017 civil and environmental science journal vol. 05, no. 02, pp. 171-182, 2022 182 [24] h. sonmez, "modification of the liquefaction potential index and liquefaction susceptibility mapping for a liquefaction-prone area (inegol, turkey)". j. env. geo., vol. 44(7), pp. 862– 871, 2003. [25] w. pawirodikromo, l. makrup, m. teguh, dan b. suryo, "development of synthetic ground motion at a specific site in yogyakarta town, indonesia utilizing the psha method," e3s web of conferences, vol. 156, 2020. [26] r.d. andrus, k.h. stokoe, "liquefaction resistance based on shear wave velocity in evaluation of liquefaction resistance of soils, in: t.l. youd and i.m. idriss (eds.)," nceer proc., salt lake, ut, pp. 89-128, 1997. [27] o. uyanık, "an alternative to the repetitive strain ratio of liquefied or non-liquified soils," deu. fen ve müh. dergisi, vol. 8 (2), pp. 79–91, 2006. [28] a. ghazi, h. h. moghadas, h. sadeghi, m. ghafoori, and g.r. lashkaripour, "spatial variability of shear wave velocity using geostatistical analysis in mashhad city, ne iran," open j. geol., 4, 354-363, 2014. civil and environmental science journal vol. ii, no. 02, pp. 084-094, 2019 84 performance of the dispin models with automatic parameter calibration on the transformation of rainfall to runoff data sulianto1, m bisri2, l m limantara2, d sisinggih2 1civil engineering department, university of muhammadiyah malang, 65144 malang, indonesia 2water resources engineering department, universitas brawijaya, 65145 malang, indonesia sulianto1967@email.com received 16-07-2019; revised 31-07-2019; accepted 20-08-2019 abstract. this article presents a new model of the disprin model combination with two different level optimization methods. the new model of disprin model combination and differential evolution (de) algorithm is called disprin25-de models and its incorporation with monte carlo simulation method called disprin25-mc models. the case study is lesti watershed (319.14 km2) in east java. the model test uses a 10-year daily data set, from january 1, 2007 to december 31, 2016. data series year 2007 ~ 2013 as a set of training data for calibration and data year 2014 ~ 2016 as testing data set for model validation. running program disprin25-de models with input parameter value c_min = 0, c_max = 1, h_min = 0, h_max = 600 mm obtained best fitness 0.044 m3/sec, nse = 0.762 and pme = -0.059. the disprin25-mc models analysis generates a minimum rmse of 0.056 m3/sec, nse = 0.779, pme = -0.70. from the rmse and nse indicators it appears that both models can show an equivalent level of performance, but in terms of the pme indicator and iteration time is apparent the disprin25-mc model has worse performance than the two disprin25-de models. keywords: automatic, calibration, disprin model, rainfall-runoff 1. introduction a combination of metaheuristic methods with a conceptual hydrological model can produce a reliable and practical new model applied to divert the rainfall data series into runoff data. in the application the new model can perform automatic calibration by utilizing the rainfall data [p(t)], evapotranspiration [ep(t)] and runoff [q(t)] with limited series length [10]. several new models resulted from a combination of conceptual models of hydrology and metaheuristic methods have been successfully developed by previous researchers, among others; the combination of ga with hbv modified model [15], ctsm algorithm with hbv model and nam model [13], combination of ga with hbv modelling model [8], shuffle complex evolution algorithm (sce) with affdef model [4], combination dynamically dimensioned search (dds) algorithm and sce algorithm with swat 2000 model [21]. xin'anjiang models with sce algorithms [1], ga and ga hybrid [20]. mailto:sulianto1967@email.com mailto:sulianto1967@email.com civil and environmental science journal vol. ii, no. 02, pp. 084-094, 2019 85 metaheuristic methods for the automatic calibration of the tank model parameters have been widely proposed by world researchers, including a combination of particle swam optimization (pso) algorithms with tank models [16], tank models combined with marquard algorithm [17], ga [13]. the combination of the tank models with the pso algorithm for flood discharge analysis with the hourly period in urban areas in taiwan has also performed very well [7]. multi tank model 6 tanks system combined with dds algorithm can show better results than the output of the finite element method (fem) model [9]. the tank model 8 tank system combined with dds algorithm and ga can perform well in predicting groundwater fluctuations in japanese yamagata. in this case the two developed models can show nearly the same error rate, but the dds algorithm based optimization method is more effective in terms of speed reaching convergent conditions [6, 11]. this article presents two new models result the combination of the disprin model (dee investigation simulation program for regulating network) as described by d.g. jamieson & j.c. wilkinson (1972) in shaw, 1985, page 367 with parameter optimization method based on de algorithm and monte carlo simulation method. the new model of the combination of disprin 25 model parameters with algorithm de called disprin25-de model and its merger with monte carlo simulation method named disprin25-mc model [18]. the application program system is compiled using m-file matlab programming language with the reason of practicality in matrix operation and easiness in data management in graphical form. the results of this study are expected to be an alternative solution to solve the problem of limited river flow data which is often a classical constraint in water resource development activities in developing countries. 2. material and methods 1.1 hydrological model the disprin model is included in the lumped model’s category which technically can be solved by using the analogy of the sugawara tank model simulation. in "the uk's water resources board's model disprin", this model was developed at the dee river research program in the united states [12]. the scheme developed as the basis of simulation is shown figure 1. figure 1. simulation scheme of disprin models. civil and environmental science journal vol. ii, no. 02, pp. 084-094, 2019 86 in the application of the disprin model a watershed should be divided into 3 zones according to their position and physical characteristics, i.e. up-land zone, hill-slope zone and bottom-slope zone. the up-land zone is located in an upstream basin that is physically sloped by a steep slope, zone hillslope located in a central basin with a relatively moderate surface slope and a bottom-slope zone located downstream of a watershed that tends to have a relatively flat surface slope. each zone of the watershed is presented by two vertically arrayed tanks. the first tank or upper tank represents the combined surface and intermediate reservoir that contribute to the flow on the surface flow and the intermediate flow. the second tank or bottom tank is the reservoir sub-base that contributes to the flow of the sub-base flow. the tanks in each zone are interconnected with the principle of gravity flow. the horizontal outflow flow from the up-land zone tank group will flow in the hill-slope zone tank group, then the hill-slope zone tank group will drain the water in the bottom slope zone. in the vertical upstream flow, the upper tank will fill the bottom tank when there is sufficient water reservoir in the upper tank. however, if evapotranspiration is so dominant that it cannot be fulfilled by tank water reserves, the water reserves in the lower tanks will be taken at the value of the deficit. this process applies also to two tank groups in the hill-slope basin zone and bottom-slope zone. the flow through a tank can be solved through the continuity equation. if tank b1 is reviewed, then the equation applies: sb1(t) = sb1(t-1) + qa1(t) qb1(t) qb2(t) + py(t) – ey(t) (1) with, sb1(t) = water level tank b1 period t [mm]. sb1(t-1) = water level tank b1 period t-1 [mm]. qa1(t) = horizontal flow tank a1 period t [mm/day] py(t) = precipitation on hill-slope zone period t [mm/day] ey(t) = evapotranspiration on hill-slope zone period t [mm/day] qb1(t) = horizontal flow tank b1period t [mm/day] = cb1*[(sb1(t-1) + sb1(t)]/2) hb1] (2) qb2(t) = vertical flow tank b1 period t [mm/day] = cb2*[sb1(t-1) + sb1(t)]/2] (3) cb1 = horizontal flow coefficient tank b1 cb2 = vertical flow coefficient tank b1 the tank d1 accommodates the channel flow factor in the attenuation effect component. the water reservoir in this tank is not affected by the evapotranspiration process. the filling of water in the tank d1 is only influenced by the percolation flow of the three watershed zones. at the beginning of the dry season the base flow in the river is caused by the intermediate flow and sub-base flow components. however, at the end of the dry season when the water reserves in the intermediate zone have been exhausted to meet evapotranspiration needs, the river flow is only supported by the tank d1. high water catches on tank d1 stated: sd1(t) = sd1(t-1 +qa4(t)+qb4(t)+qc4(t) (4) in the disprin model stream flow is the result of translation effect of superposition of surface flow, sub base flow and base flow. the translation effect factor is presented by tank d2. the water height in tank d2 is calculated by the equation: sd2(t) = sd2(t-1)+qc1t(t)+ qc3t(t)+qd1(t) (5) with, sd2(t) = water lavel tank d2 period t, sd2(t-1) = water level tank d2 period (t-1), qc1t(t) = (ab/a_das) * qc1(t), and qc3t(t) = (ab/a_das) * qc3(t). civil and environmental science journal vol. ii, no. 02, pp. 084-094, 2019 87 q (t) is the river runoff period t at the control point of the watershed in units according to the calculated analysis period. in data analysis with daily period input variables, then river runoff value in m3/second unit can be converted by equation: q(t) = a_das * q(t)/(86.4) (6) 2.2 calibration model 2.2.1 fitness function the parameter calibration model is an analogy of solving the optimization problem to produce the optimal value of disprin model parameters. the objective function of the optimization process is the minimization of deviation curve of debit training data and the model simulation debit curve. in the metaheuristic method the objective function is expressed as a fitness function. in this article the fitness value is expressed as rmse which is calculated by the equation [7, 21]: 𝐹 = 𝑅𝑀𝑆𝐸 = √ 1 𝑁 ∑ [𝑄𝑡𝑟𝑎𝑖𝑛,𝑡 − 𝑄𝑠𝑖𝑚,𝑡 ] 2𝑁 𝑡=1 (7) with, f = fitness, qsim,t = discharge simulated period t, qtraining, t = discharge training period t, n = number of data points. 2.2.2 parameter optimization based on differential evolution algorithm (de) de includes stochastic search methods and population based search. de has similarities with other evolutionary algorithms (ea), but differs in terms of distance and direction information from the current population used to guide the search process for better solutions. in the field of hydrological modelling the de algorithm has been successfully applied for parameter optimization of swat model 16 parameters [21]. the de algorithm contains 4 components, namely; 1) initialization, 2) mutation, 3) recombination or crossover and 4) selection [2]. the process of calibrating the parameters in the disprin25-de model systematically can be explained as follows: 1) input training data set : evapotranspiration [ep(t)], rainfall [p(t)], observation debit [qtraining(t)] and area of up-land watershed zone [au], hill-slope [ah], bottom-slope [ab]. 2) setting parameter de : dimension (d), number of individual (n), upper limit (ub) and lower limit (lb) parameter value, and maximum generation number (maximum iteration). the value of d is corresponding to the number of optimized disprin model parameters. d = 25 for disprin25de models. 3) initialization: the generation of the initial value of the 0th generation vector, the variables to j and vector ican be represented by the following notation. 𝑥𝑗,𝑖,0 = 𝑙𝑏𝑗 + 𝑟𝑎𝑛𝑑𝑗 (, 1)(𝑢𝑏𝑗 − 𝑙𝑏𝑗 ) (8) the random number is generated by the rand function, where the resulting number lies between (0,1). index j denotes the variable to j. in case of minimization of function with 25 variables, then j will be worth 1,2,3, .... 25. 4) mutation, this process will produce population with size of n vector experiment. mutation is done by adding two vector differences to the third vector by the following notation : 𝑣𝑖,𝑔 = 𝑥𝑟0,𝑔 + 𝐹(𝑥𝑟1,𝑔 − 𝑥𝑟2,𝑔) (9) it appears that two randomly selected vector differences need to be scaled before being added to the third vector, xr0, g. factor scale fє (0,1+) has real positive value to control population growth rate. the base vector index r0 is determined by a random way that different from the index for the target vector, i. besides being different from each other and different from the index for the vector base and the target vector, the vector index of the increments r1 and r2 can be chosen once per mutant. 5) crossover, at this stage de crosses every vector (xi, g) with mutant vector (vi, g), to form the vector of ui, g with the formula. civil and environmental science journal vol. ii, no. 02, pp. 084-094, 2019 88 𝑢𝑖,𝑔 = 𝑢𝑗,𝑖,𝑔 = { 𝑣𝑗,𝑖,𝑔 → 𝑖𝑓 (𝑟𝑎𝑛𝑑(0,1) ≤ 𝐶𝑟𝑜𝑟𝑗 = 𝑗𝑟𝑎𝑛𝑑 𝑥𝑗,𝑖,𝑔 → 𝑖𝑓 (𝑟𝑎𝑛𝑑(0,1) > 𝐶𝑟𝑜𝑟𝑗 ≠ 𝑗𝑟𝑎𝑛𝑑 (10) 6) selection, if trial vector ui,g has a goal function value smaller than the target destination function xi,g, then ui,g will replace the position xi,g in the population in the next generation. if the opposite happens then the target vector will remain in its position in the population. the process of analysis of items 4), 5), 6) is done repeatedly from generation 0 to the maximum generation specified (iter_max). once the maximum generation is reached, then the optimal parameter values and the model simulation debit from the calibration stage are generatedand the model simulation debit from the calibration stage.. 2.2.3 parameter optimization base on monte carlo simulation method in the field of hydrological modelling monte carlo simulations have been successfully used to perform the uncertainty and sensitivity analysis of fortran-hspf model parameters [14]. the monte carlo method can also be used to estimate the value of tank model parameters [3] and successfully identify the value and structure of the hbv model with great satisfaction [19]. the process parameter optimization of disprin25 model is done through the following stages [14]: 1) formulate a system of optimization model equations that will be simulated, 2) input training data sets, namely: au, ah, ab, p (i), ep (i) and qobs(i), 3) input parameters monte carlo method, ie: number of samples (n), and sample space limit (lb and ub) of each variable analyzed, i.e. 25 parameters model disprin. 4) generates random numbers of uniform distributions or other probabilistic distributions of value [0,1], 5) calculate the appropriate random variable for each model parameter under study based on the number and space of the desired sample, 6) evaluate model performance by using random input parameter value result from step 5) according to the equation developed in step 1), 7) steps 4) and 5) repeated as much as the number of samples given, and 8) analyzing and discussing the output of the models presented in graphical form and statistical parameters. 2.3 model validation model validation is done by reapplying the disprin25 model with input set of data testing and the optimal parameter value of the result of the calibration process. the simulated discharge from the model output will be compared with the discharge testing data, and the deviation test uses the rmse, nash-shutclife efficiency (nse) and persistence model efficiency (pme) indicators. nse and pme are calculated by the formula [5]. 𝑁𝑆𝐸 = 1 − ∑ (𝑞𝑡 𝑠𝑖𝑚−𝑞𝑡 𝑜𝑏𝑠) 2 𝑁 𝑡=1 ∑ (𝑞𝑡 𝑜𝑏𝑠−𝑞𝑡 𝑚𝑒𝑎𝑛) 2𝑁 𝑡=1 (11) 𝑃𝑀𝐸 = 1 − ∑ (𝑞𝑡 𝑠𝑖𝑚−𝑞𝑡 𝑜𝑏𝑠) 2 𝑁 𝑡=1 ∑ (𝑞𝑡 𝑜𝑏𝑠−𝑞𝑡−1 𝑜𝑏𝑠) 2𝑁 𝑡=1 (12) 2.4 case study the position of lesti watershed in unity of brantas watershed is shown in figure 2. lesti watershed has an area of 319.14 km2, divided into up-land, hill-slope and bottom slope respectively of 67.02 km2, 114.89 km2 and 137.23 km2.the data series of hydroclimatology in this study is data of recording date from january 1, 2011 to december 31, 2013. evapotranspiration data obtained from the analysis using penmann method with data input wind speed, air temperature, air humidity and the duration of solar irradiance monthly. climatic parameters data obtained from the recording results from karangkates station. there are 4 rain gauge stations covered in lesti watershed, namely; st. dampit, st. turen, st. wajak and st. tirtoyudo. rainfall data recorded in daily period. average civil and environmental science journal vol. ii, no. 02, pp. 084-094, 2019 89 regional precipitation is calculated by the polygon thiesen method. weighting factor of polygon thiesen in the four rain stations was 0.380, 0.09, 0.19 and 0.34, respectively. river flow data from the listing of st. awlr tawangrejeni is available in the hourly period. the transformation of the discharge data into a daily mean period is calculated by means of an algebraic average. furthermore, the data series is divided into two groups. the first group as a set of data training for the calibration process and the second group as set of data testing for the model validation process. set of 7-year training data, the record period of january 1, 2007 until december 31, 2013 and set of data testing from the record results of the period january 1, 2014 to december 31, 2016. hydroclimological data in daily periods graphically shown figure 3. comparison of statistical parameters set of data training and data testing sets are shown in table 1. average, minimum, maximum, and varied sets of data testing tend to be larger than the set of data testing. figure 2. case studi, lesti watershed table 1: comparison of statistical parameters of training and testing data sets statistic of parameters discharge data (m3/sec) rainfall data (mm/day) training testing training testing mean 17.44 18.59 6.17 6.76 minimum 5.91 5.99 0.00 0.00 maximum 35.03 37.58 77.76 83.87 deviation standard 6.02 6.87 9.62 10.82 civil and environmental science journal vol. ii, no. 02, pp. 084-094, 2019 90 figure 3: daily training and testing data set 3. result and discussion the disprin models implementation reference is still very limited so the feasibility limit of the parameters value becomes difficult to define. referring to the application of the sugawara’s tank model of various references, the minimum (lb_c) and maximum (ub_c) parameters of the tank outlet coefficient are "0" and "1" respectively. the initial high water catch and the position of the tank outlet are positive numbers whose value varies depending on the watershed hydrological characteristics being analyzed. in this article the minimum value of the initial parameter of the container and the position of the tank outlet (lb_h) is set to "0", and the maximum value (ub_h) is approached by trial and error. the results of the analysis by utilizing the application disprin25-de model generated the relevant ub_h value is 600 mm. further analysis using input value lb_c = 0, ub_c = 1, lb_h = 0, ub_h = 600 mm. the results of the disprin25-de models analysis with the parameters inputn = 350 and iter_max = 250 and the results of the disprin25-mcmodels analysis with the input sample number of 200,000 are shown in table 2, table 3 and figure 4 to figure 6. table 2: comparison of model performance indicator values performance indicator notation calibration stage validation stage de mc de mc root mean square error rmse 0.044 0.056 0.086 0.100 nash-sutcliffe efficiency nse 0.762 0.779 0.727 0.769 persistence model efficiency pme -0.059 -0.700 -0.128 -0.505 time of iteration t_iteration 126.67 172.59 the best fitness value or minimum rmse at the calibration stage of the disprin25-de models is obtained 0.044 m3/sec and the analysis of the disprin25-mc models with the sample input quantity of 200,000 is obtained 0.056 m3/sec. the progress of achieving the minimum rmse values of the two models is shown in figures 4 and 5. based on the rmse and nse indicators both models can perform as well, but on the pme indicator the both model gives a negative value which means it does not civil and environmental science journal vol. ii, no. 02, pp. 084-094, 2019 91 perform well, the disprin25-de model has much better performance than the disprin25-mc model. model performance in the validation stage is generally decreased although not significant. this is understandable because the data training sets and data testing sets have different statistical parameters. in terms of the iteration the disprin25-mc model shows 30% longer than the disprin25-de model. from the various considerations, it can be concluded that the process optimization parameter disprin25 model based de algorithm is more effective than the analysis by applying monte carlo simulation method. figure 4: progress the best fitness value of de algorithm figure 5: rmse value of monte carlo simulation results sorted from large to small table 3: disprin25 models optimum parameters parameter description constraint optimum parameters lbj ubj de mc ha1 height of surface outlet up-land zone 0.00 600.00 0.07 69.95 ha2 height of sub surface outlet up-land zone 0.00 600.00 600 433.8 ca2 infiltration coefficient up-land zone 0.00 1.00 0.348 0.502 ca3 sub surface coefficient up-land zone 0.00 1.00 0.499 0.0075 ca4 percolation coefficient up-land zone 0.00 1.00 0.18 0.926 sa1_0 initial storage of tank sa1 0.00 600.00 155.15 599.79 sa2_0 initial storage of tank sa2 0.00 600.00 0 434.53 hb1 height of surface outlet hill-slope zone 0.00 600.00 0 592.27 hb2 height of sub surface outlet hill-slope zone 0.00 600.00 500.31 281.28 cb2 infiltration coefficient hill-slope zone 0.00 1.00 0.672 0.954 cb3 sub surface coefficient hill-slope zone 0.00 1.00 0.906 0.898 cb4 percolation coefficient hill-slope zone 0.00 1.00 0.293 0.768 sb1_0 initial storage of tank sb1 0.00 600.00 67.72 213.99 sb2_0 initial storage of tank sb2 0.00 600.00 600 160.06 hc1 height of surface outlet bottom-slope zone 0.00 600.00 0 434.89 hc2 height of sub surface outlet bottom-slope zone 0.00 600.00 596.49 269.24 cc2 infiltration coefficient bottom-slope zone 0.00 1.00 0.846 0.684 cc3 sub surface coefficient bottom-slope zone 0.00 1.00 0.26 0.547 cc4 percolation coefficient bottom-slope zone 0.00 1.00 0.506 0.829 sc1_0 initial storage of tank sc1 0.00 600.00 164.48 221.5 sc2_0 initial storage of tank sc2 0.00 600.00 600 79.31 cd1 runoff coefficient 0.00 1.00 0 0.007 cd2 runoff coefficient 0.00 1.00 0.007 0.386 sc1_0 initial storage of tank (attenuation effect) 0.00 600.00 282.57 369.87 sc2_0 initial storage of tank (translation effect) 0.00 600.00 591.1 2.97 civil and environmental science journal vol. ii, no. 02, pp. 084-094, 2019 92 figure 6: comparison of the discharge observed data series and the model output the comparison of the flow curve data and the curve from the model outcomes at the calibration stage and validation stage is shown figure 6. results from the disprin25-mc model outcomes appear to be different at high flow conditions, where the results obtained tend to be under estimated. the resulting flow curves of the both models at the calibration stage can generally follow the seasonal trend of the training data flow curve. in low flow, normal flow and high flow conditions tend to place themselves in a moderate position. fluctuations in the sharp flows that occur due to the high rainfall intensity in the daily period cannot be responded well. this condition is the cause of the low value of the resulting pme indicator. taking to the simulation scheme and the total equation of the model disprin25 flow as shown in figure 1, the existence of the translation effect factor (channel flow) is likely to be the factor causing this condition. the existence of the translation effect factor presented by a tank with a bottom outlet actually becomes an obstacle to model efforts in anticipating the fluctuation of sharp flows. rapid flow changes due to the high rainfall intensity occurring in the accumulation of up-land zone tanks, hill-slope and bottom-slope are muted in translation effect tanks and are delivered slowly. in the minimum rmse condition the optimal value of the disprin25 model parameter is shown in table 3 in column [5, 6]. the optimal value of disprin25 model parameters from the output of the two models gives different results because the resulting performance level is also significantly different. 4. conclusions based on the rmse, nse, pme and iteration indicators the de algorithm is proven to work more effectively than monte carlo simulation methods in solving the parameterization problem of the disprin25 model. testing model disprin25-de on lesti watershed (319.14 km2) with daily data set can show good performance both calibration stage and validation stage. generally generated flow curves can follow the seasonal trend of the observation flow curve. in low flow conditions, the normal flow as well as the high flow curve from the outline of the model tend to place themselves in a moderate position. fluctuations in the sharp flows that occur due to the high rainfall intensity of the daily period cannot be responded well. this condition is the cause of the low value of the resulting pme indicator. the translation effect factor presented by a tank with a basic outlet actually hampers the efforts of the disprin25 model in anticipating the occurrence of sharp fluctuations. rapid flow changes due to the high rainfall intensity occurring in the accumulation of up-land zone tanks, hillslope and bottom-slope are muted in translation effect tanks and are delivered slowly. the optimal 0 500 1000 1500 2000 2500 3000 3500 4000 5 10 15 20 25 30 35 40 periode d is c h a rg e (m 3 /s e c ) comparation q disprin-de, q disprin-mc & q-obs q-obs disprin-de disprin-mc 5 10 15 20 25 30 35 40 5 10 15 20 25 30 35 40 q-disprin de [m3/sec] q -o b s [ m 3 /s e c ] plot q-disprin de vs q-obs 5 10 15 20 25 30 35 40 5 10 15 20 25 30 35 40 q-disprin mc [m3/sec] q -o b s [ m 3 /s e c ] plot q-disprin mc vs q-obs civil and environmental science journal vol. ii, no. 02, pp. 084-094, 2019 93 value of disprin25 model parameters from the output of the two models gives different results because the resulting performance level is also different. references [1] bao h. j, wang l, li z. j, zao l. n, guo-ping zhang, 2008, hydrological daily rainfallrunoff simulation with btopmc model and comparison with xin’anjiang model, water science and engineering, 2010, 3(2): 121-131, doi: 10.3882/j.issn.1674-2370.2010.02.001, http://www.waterjournal.cn, e-mail: wse2008@vip.163.com [2] budi santosa & paul willy, 2011, metoda metaheuristik konsep dan implementasi, cetakan pertama, guna widya, surabaya, indonesia. [3] chen c, shrestha d.l., perez g.c., solomatine d., 2006, comparison of methods for uncertainty analysis of hydrologic models, 7th international conference on hydroinformatics hic 2006, nice, france. [4] darikandeh dorsa, akbarpour abolfazl, bilondi mohsen pourreza & hashemi seyyed reza, 2014, automatic calibration for estimation of the parameters of rainfall runoff model, scijour, journal of river engineering, volume 2, issue 8 2014, http://www.scijour.com/jre. [5] gupta, sorooshian & yapo, 1999, “status of automatic calibration for hydrologic models: comparation with multi level expert calibration”, journal of hydrologic engineering, vol. 4, no. 2, april, 1999. asce, issn:1084-0699/99/0002-0135–0143, http://www.ascelibrary.org. [6] huang x. l. & xiong j., 2010, parameter optimization of multi-tank model with modified dynamically dimensioned search algorithm, proceedings of the third international symposium on computer science and computational technology (iscsct ’10), jiaozuo, p. r. china, 14-15, august 2010, pp. 283-288, isbn 978-952-5726-10-7, © 2010 academy publisher, ap-proc-cs-10cn007. [7] hsu & yeh, 2015, study on flood para-tank model parameters with particle swarm optimization, journal of information hiding and multimedia signal processing, ubiquitous international volume 6, number 5, september 2015, @ 2015 issn 2073-4212 [8] jonsdottir harpa, madsen henrik & palsson olafur petur, 2005, parameter estimation in stochastic rainfall-runoff models, elsevier, journal of hydrology 326 (2006) 379–393. [9] kenji t.，yuzo o.，xiong j. & koyama t, 2008, tank model and its application to predicting groundwater table in slope, chinese journal of rock mechanics and engineering, vol.27 no.12 dec，2008, clc number：p 642.22 document code：a article id：1000–6915(2008)12–2501–08. [10] kim oong h., paik kyung r., kim hung s. & lee, 2005 dong r., a conceptual rainfall – runoff model considering seasonal variation, article in hydrological processes · december 2005impact factor: 2.68 · doi: 10.1002/hyp.5984advances in hydro-science and –engineering, volume vi, http://www.researchgate.net/publication/ 227599393 [11] kuok king kuok, sobri harun and po-chan chiu, 2011, comparison of particle swarm optimization and shuffle complex evolution for auto-calibration of hourly tank model’s parameters, int. j. advance. soft comput. appl., vol. 3, no. 3, november 2011, issn 20748523; copyright © icsrs publication, 2011, www.i-csrs.org [12] m. shaw, elizabeth, 1985, hydrology in practice, van nostrand reinhold (uk) co. ltd. [13] ngoc t. a., hiramatsu k. & haramada m., 2012, optimizing parameters for two conceptual hydrological models using a genetic algorithm: a case study in the dau tieng river watershed, vietnam, jarq 47 (1), 85 – 96 (2013) http://www.jircas.affrc.go.jp. [14] ramires j.d, camacho r, mcanally w, martin j, 2012, parameter uncertainty methods in evaluating a lumped hydrological model, obrasy proyectos 12, 42-56. http://www.waterjournal.cn/ http://www.waterjournal.cn/ http://www.scijour.com/jre http://www.scijour.com/jre http://www.researchgate.net/publication/%20227599393 http://www.researchgate.net/publication/%20227599393 http://www.jircas.affrc.go.jp/ http://www.jircas.affrc.go.jp/ civil and environmental science journal vol. ii, no. 02, pp. 084-094, 2019 94 [15] saibert jan, 2000, multi-criteria calibration of conceptual runoff model using a genetic algorithm, hydrology and earth system sciences, 4(2), 215-224 (2000) egs. [16] santos, 2011, application of a particle swarm optimization to the tank model, risk in water resources management (proceedings of symposium h03 held during iugg2011 in melbourne, australia, july 2011) (iahs publ. 347, 2011). [17] setiawan b., fukuda t. & nakano y., 2003, developing procedures for optimization of tank model’s parameters, agricultural engineering international: the cigr journal of scientific research and development. [18] tolson b. a. & shoemaker c. a., 2007, dynamically dimensioned search (dds) algorithm for computationally efficient watershed model calibration, ater resources research, vol. 43, w01413, doi:10.1029/2005wr004723, 2007, copyright 2007 by the american geophysical union. 0043-1397/07/2005wr004723$09.00 [19] uhlenbrook s, seibert j, leibundgut c, rodhe a, 1999, prediction uncertainty of conceptual rainfallrunoff models caused by problems in identifying model parameters and structure, hydrological sciences-joumal-des sciences hydrologiques, 44(5) october. [20] wang w. c., cheng c. t., chau k. w & xu d. m., 2012, calibration of xinanjiang model parameters using hybrid genetic algorithm based fuzzy optimal model, © iwa publishing 2012, journal of hydroinformatic, 14.3 – 2012, 785 w.-c. wang et al. | calibration of xinanjiang model parameters using hga based fom. [21] zhang, srinivasan, zhao & liew (2008), evaluation of global optimization algorithms for parameter calibration of a computationally intensive hydrologic model, hydrological processes, published online in wiley interscience, www.interscience.wiley.com. open access proceedings journal of physics: conference series civil and environmental science journal vol. iii, no. 01, pp. 010-017, 2020 10 application of sediment runoff model to the wlingi reservoir watershed, indonesia1 kurdianto idi rahman1, dian sisinggih2, runi asmaranto2 1 jasa tirta i public corporation, malang, 65145, indonesia 2 water resources engineering department, universitas brawijaya, malang, 65145, indonesia kurdi.rahman@gmail.com received 31-12-2019; accepted 19-02-2020 abstract. sedimentation is the main problem in wlingi reservoirs. they are suffering from severe watershed erosion and a heavy load of volcanic ash ejected from the eruption of mount kelud. wlingi reservoir is significantly affected by recurrent volcanic activities of mount kelud. after the 2014 eruption, the capacity of wlingi reservoirs decreased by 82.5% or only 3.70 million m3 from the initial capacity of 24 million m3. to analyze the impact of volcanic eruption disaster on reservoir sedimentation an integrated numerical model of sediment is required. the fujiyama model is an integrated sediment runoff model using a basin model composed of unit channels and unit slopes. the model seems suitable for a mountainous basin. the simulation results from the model explain that the mechanism of transporting sediment into the wlingi reservoir can be explained based on the type of sediment transport. the movement of sediment originating from kelud mountain in kali lekso is strongly influenced by rainfall duration compared to the intensity of the rainfall. also, the simulation model results explained that the mechanism of sediment transportation is dominated by suspended load or bed load which when large discharges will move with the mechanism of suspended load sediment transport. keywords: fujiyama model, sedimentation, wlingi watershed. 1. introduction reservoir sustainability at this time are increasingly threatened because of the high rate of sedimentation occurs. sedimentation is one of the main problems in the reservoir in the brantas river basin. the wlingi reservoir, which is part of a reservoir system in the brantas basin, has rapidly lost its storage capacity. the decrease in reservoir storage affects water allocation for energy generation, irrigation and raw water fulfillment during the dry season and flood control capability in the rainy season [1]. in addition, the wlingi reservoir is greatly affected by the eruption activity of mount kelud, which is one of the most active volcanoes on the island of java, indonesia [2]. the eruption of mount kelud in 1990 produced sediment volumes which greatly influenced sedimentation in the wlingi and lodoyo reservoirs [3]. the latest data for 2016 shows that the total reservoir capacity of the wlingi reservoir has decreased by 82.5% or only 4.45 million m3 from the initial capacity 24 million m3 [1]. at now, not 1 cite this as: rahman, k., sisinggih, d., & asmaranto, r. (2020). application of sediment runoff model to the wlingi reservoir watershed, indonesia. civil and environmental science journal, 3(1), pp.10-17. doi: https://doi.org/10.21776/ub.civense.2020.00301.2 civil and environmental science journal vol. iii, no. 01, pp. 010-017, 2020 11 many numerical models are used to estimating erosion and sedimentation of reservoirs due to volcanic eruptions were applied in indonesia. this paper will discuss the sedimentation analysis of the wlingi reservoir using the sediment runoff model to predict erosion and sedimentation due to volcanic material. it can be used as a reference in planning and management decision on related sedimentation action activities in the wlingi reservoir. 2. calculations method and conditions 2.1. target area the target area is wlingi reservoir watershed (fig 1). the area of watershed is around 697 km2 and elevation of this watershed is distributed from 145 m to 2850 m. the mean annual precipitation was 2.227 mm. in this area there are 4 rain gauge stations which are operated by jasa tirta i public corporation (pjt i), the location of those station are shown in fig 1. figure 1. research area in the wlingi reservoir watershed 2.2. method in this simulation, we applied yamanoi and fujita’s model [4], the sediment runoff model as known as fujiyama model. the model can calculate the water and sediment discharge and sediment deposition in the unit channel network. it mainly requires the rainfall conditions, topographical conditions, and grain size distribution of the river bed and produced sediment material. the model was developed by integrating sub-process models of sediment production, sediment supply, and sediment transport using basin model composed of unit channels and unit slopes (fig. 2). the model was constructed based on unit channel and unit slope basin model by egashira & matsuki model [5] as shown in fig. 3 [6]. a unit channel is defined as a section in the river between two adjacent confluence points. the two slopes that connect with both sides of a unit channel were defined as unit slopes. a unit channel was assumed to be straight and uniform. civil and environmental science journal vol. iii, no. 01, pp. 010-017, 2020 12 figure 2. conceptual of fujiyama model. the unit channels and unit slopes data were extracted from dem employing grass-gis. the length of each unit channel was extracted automatically using gis, and the inclination of the unit channel was calculated by dividing the difference in the elevation between the upstream end and the downstream end by the length of the channel. the area of each unit slope was then calculated using gis by measuring the projected area of each slope, and the angle was calculated as the average angle on the actual slope [6]. the sediment transport model of egashira & matsuki was employed and linked to the sediment supply model. this model simulates the change in bed elevation in the unit channel and in the grainsize distribution of bed material. rainfall runoff also was simultaneously simulated using the kinematic wave method and darcy’s law. the supplied sediment was expressed as riverbed evolution at the nearest unit channel. each model is connected and integrated using grass-gis. the timing and volume of sediment production are computed by the sediment production model from the topographical data and meteorogical data. using data on sediment production, the sediment supply model and transport model are employed simultaneously. as a result of this application, the water discharge, sediment discharge, and riverbed elevation can be obtained [4]. 2.3. conditions the unit slopes and unit channels were extracted using the 30m mesh dem data from srtm and refined to 10m mesh. the grain size distribution data was obtained by laboratory analisis from lekso, jari and semut river bed material (fig. 4). rainfall data using the average daily rainfall data from 4 stations in the target area in 2016 (fig. 5). figure 4. grain size distribution data. 0% 20% 40% 60% 80% 100% 0,00 0,01 0,10 1,00 10,00 100,00 p e rc e n t f in n e r particle diameter (mm) figure 3. unit channel and unit slopes, (a) channel units with two inflow points and one outflow (b) each channel unit has two slope units and (c) each slope unit can be divided into several slope sub-units based on the value of the slope aspect and other parameters. civil and environmental science journal vol. iii, no. 01, pp. 010-017, 2020 13 figure 5. rainfall data in 2016. 3. result and discussion 3.1. water and sediment discharge the calculated results for water discharge were higher than the observed results as shown in fig. 6. this possibility is because the rainfall simulation process which in the model uses uniform rainfall. so by using the uniform rainfall, the calculation assumption will get a higher value than the observation data. the consequence is the cumulative value of sediments deposited in the wlingi reservoir in 2016 reached a value of 598,824 m3 (shown in fig. 7), higher than the sediment value from the analysis of historical reservoir data of 500,000 m3/year. figure 6. rainfall-runoff discharge in wlingi reservoir watershed calculation by the model 3.2. sediment transport the mechanism of sediment transportation is dominated by suspended load sediments, or sediment bed loads that when large discharges will move with the suspended load sediment transport mechanism. for bed load movements with a basic flow mechanism, it cannot be described in the model. however, agradation and degradation in the process of riverbed change occurred during 2016. from the results of the running model to simulate sediment flow in the wlingi watershed, shows that the movement of sediments occurs in moderate and high intensity rain conditions. from the results of the running model for 1 year, it is known that the movement of each type of sediment transport modes both originating sediment from the slopes of mount kelud and those from the southern region of the wlingi reservoir. sediment transport in the rainy season occurs in all major tributaries that enter through the wlingi reservoir. civil and environmental science journal vol. iii, no. 01, pp. 010-017, 2020 14 figure 7. water and sediment discharge calculation by the model the movement of the bed load material is strongly influenced by the duration of the existing rainfall compared to the intensity of the rainfall that occurred. short duration rainfall (<6 hours) occurred at the upstream of kali lekso was unable to generate enough runoff to move river material to downstream area. its usually occurs in april-may when will enter the dry season. as a consequence of sediment flow, river bed changes only occur at the bottom of the upper lekso river, where although the runoff discharge is low, the relatively steep river slope will be able to erode the river bed. when the slope of the river is not steep enough, the degradation process does not occur and the material will pile up, causing channel agradation. conversely, when fairly long duration rainfall (>6 hours) occurs, usually in november-december, runoff discharges that occur on the land will be quite significant when it becomes a flood discharge in kali lekso and kali bambang can cause significant downward movement of bed material. the process of changing the river bed occurs when a long enough duration rainfall able to bring bed material moving at a longer range and enter the reservoir. the agradation and degradation process shown in fig. 7. unlike the movement of bed load material, for suspended load material, the sediment discharge increasing will be greatly influenced by the amount of runoff or flood discharge that occurs compared to rainfall duration. from the rainfall-runoff and sediment transport process in the model, obtained that the amount of suspended load sediment entering the wlingi reservoir has a linear relationship with the upstream rainfall events both in intensity and amount of rainfall. sediment transport for suspended load occurs for short duration rainfall both upstream of lekso river and lemon river. its will bring suspended sediment material that originates from the upstream trough the reservoirs. likewise, when it long duration rainfall, the resulting runoff discharge becomes higher so that the dominance of sediment transport is no longer by suspended load sediment but by bed load material transport. increased water discharge in the channel makes the flow velocity increase far beyond the initial threshold of the suspended moving grain level, so that the movement of the suspended load transport material granules becomes the wash load along the channel. fig. 8 illustrates the process of transporting sediment for suspended load material that occurs in the wlingi watershed. civil and environmental science journal vol. iii, no. 01, pp. 010-017, 2020 15 figure 7. river bed change (agradation and degradation) figure 8. suspended load sediment transport comparable to the movement of bed load and suspended load material transport, for wash load almost does not occur when a small runoff discharges due to short duration rainfall. as explained in the previous discussion when the discharge increases due to a long duration rainfall, an increase in wash load transport occurs in all tributaries in the wlingi reservoir. fig. 9 illustrates the process of transporting sediment for wash load material that occurs in the wlingi watershed. civil and environmental science journal vol. iii, no. 01, pp. 010-017, 2020 16 figure 9. wash load sediment transport based on the results of the movement of sediment material from the model, it can be described that the material entering the wlingi reservoir is as follows. volcanic eruption material is dominated by the northern region which flows through the lekso river. whereas material from land erosion originates from the slopes of mount butak through the bambang river and legi river. from the southern area the catchment area of material erosion resulting from land flows through lemon river. 4. conclusions a result of the calculation of this model, sediment runoff model can be used to simulate annual sediment discharge. the result of runoff discharge from the model was slightly greater than the observation discharge. so, the total cumulative sediment calcuated by model is greater than the historical reservoir sediment data. the mechanism of sediment transportation is dominated by suspended load sediments, or sediment bed loads that when large discharges will move with the suspended load sediment transport mechanism. for bed load movements with a basic flow mechanism, it cannot be described in the model. however, agradation and degradation in the process of riverbed change occurred during 2016. in general, it can be stated that the results of applying the model are quite good. of course, there are still shortcomings that become a gap to be improved in future research. acknowledgments the authors thank to disaster prevention research institute kyoto university (dpri-ku) japan, departement of water resource brawijaya university (wre-ub) and jasa tirta i public corporation (pjt-i) for research support and mutual collaboration work for this study. references [1] pjt i. 2016. kajian kapasitas tampungan waduk sengguruh-sutami-lahor dan wlingi-lodoyo. malang : penelitian oleh biro penelitian dan pengembangan. [2] hidayat, f., juwono, p. t., suharyanto, a., pujiraharjo, a., legono, d., sisinggih, d., neill, d., fujita, m. & sumi, t. 2017. assesment of sedimentation in wlingi and lodoyo reservoirs: a secondary disaster following the 2014 eruption of mt. kelud, indonesia. journal of disaster research, vol. 12 no. 3. [3] soekistijono, hidayat, f. & harnanto, a. 2005. coordinated sediment flushing in wlingi civil and environmental science journal vol. iii, no. 01, pp. 010-017, 2020 17 lodoyo reservoirs and the study of its benefits and effect to water quality and ecosystem in downstream reaches. international seminar on echohydrology. denpasar. [4] kazuki yamanoi and masaharu fujita, development of a combined model of sediment production, supply and transport, and its application to a mountainous basin, journal of jsce, vol. 3, 224-229, 2015. https://doi.org/10.2208/journalofjsce.3.1_224 [5] egashira, s. & matsuki, t. 2000. a method of predicting sediment runoff caused by erosion of stream channel bed. annual journal of hydraulics engineering. japan society of civil engineers 44. [6] masaharu fujita, kazuki yamanoi and hiroaki izumiyama, a combined model of sediment production, supply and transport, sediment dinamycs: from the summit to the sea, procedings of symposium, new orleans, lousiana, usa, 11-14 december 2014) (iahs publ. 367, 2014). doi:10.5194/piahs-367-357-2015 https://doi.org/10.2208/journalofjsce.3.1_224 open access proceedings journal of physics: conference series civil and environmental science journal vol. iii, no. 01, pp. 031-036, 2020 31 cultivation of chlorella sp. and algae mix for nh3-n and po4-p domestic wastewater removal1 i wayan koko suryawan1, evi siti sofiyah1 1department of environmental engineering, faculty of infrastructure planning, universitas pertamina, jakarta, 12220, indonesia i.suryawan@universitaspertamina.ac.id received 08-01-2020; accepted 18-02-2020 abstract. domestic wastewater provides the largest contribution to pollution both in terms of quantity and quality. therefore, before being discharged into the environment, wastewater needs to be managed first. this study used the cultivation of microalgae chlorella sp. and algae mix to manage domestic wastewater. the reactor used in the study was a 3l volume of water. the cultivation process was assisted by uv-a and uv-b with the air flow rate as much as 1.2 l/min. pollutant parameters being focused on were nh3-n and po4-p nutrient parameters. allowance for nh3-n by chlorella sp. and algae mix were 54.9% and 49%, respectively. allowance for po4-p by chlorella sp. and algae mix were 70.2% and 57.1% while biomass of chlorella sp. and algae mix increased 85.5% and 98.9%. specific growth rate of chlorella sp. and algae mix were 0.025 h-1 and 0.027 h-1. as a control on biomass growth, turbidity value in the study also increased. keywords: algae mix, chlorella sp., nh3-n removal, po4-p removal 1. introduction a research conducted in jakarta by the japan international cooperation agency (jica) team reported that the total amount of wastewater in jakarta was 1,316,113 m3/day, while the amount of domestic waste was 1,038,205 m3/day that reached 79% of total wastewater [1]. in addition, there is an increasing concentration of population and industry in urban areas that directly disposing wastewater from activities into rivers or waterways without prior processing [2]. discharged wastewater with high organic material content will take large amounts of dissolved oxygen for the decomposition process [3] in addition to organic materials, nutrients such as ammonia-nitrogen (nh3-n) and phosphate (po4-p) are important nutrients for growth and metabolism of phytoplankton in waterway. high concentration of these two substances can cause eutrophication in the river, causing death of marine biota. industrial and domestic wastewater are main sources of nh3-n and po4-p. excessive presence 1 cite this as: suryawan, i., & sofiyah, e. (2020). cultivation of chlorella sp. and algae mix for nh3-n and po4-p domestic wastewater removal. civil and environmental science journal, 3(1), pp.31-36. doi: https://doi.org/10.21776/ub.civense.2020.00301.4 civil and environmental science journal vol. iii, no. 01, pp. 031-036, 2020 32 of phosphate accompanied by the presence of nitrogen can stimulate the explosion of algae growth in waters (algae bloom). wastewater management usually uses microorganisms to degrade material contained in it. one of microorganism that has the opportunity in wastewater management is microalgae. the multiplication of microalgae biomass coupled with wastewater management is considered as one of the most promising ways to produce bioenergy and bio-based by-products that are economically and environmentally friendly [4]-[5]. microalgae that is easily obtained is chlorella sp., a single-celled microalga that lives in the marine environment, grows and flourish hovering on freshwater, seawater, and brackish by utilizing sunlight as an energy source and carbon dioxide as a source of carbon. chlorella sp. is one of the green algae groups that almost 90% of them live in freshwater and 10% live in sea water compared to other green algae. microalgae has a bioactive composition that can be used as a source of antioxidants, antibacterial, anti-inflammatory and anticancer [6]. the purpose of this study is to determine the effectiveness of cultivation of chlorella sp. in processing nutrients in the form of nh3-n and po4-n in domestic wastewater. a mixture of algae taken naturally to compare nh3-n and po4-n removal. the growth rate of the microalgae was also measured in the form of mix liquor suspended solid (mlss), thus the specific growth rate of chlorella sp. and algal mixture can be seen. 2. material and methods this study consisted of two stages, namely the acclimatization and running stages. seeding was done within one week to adjust the microalgae in room conditions. chlorella sp. microalgae culture was obtained from algae farm, while the algal mixture is taken from cisadane river in jakarta selatan. cisadane river consist of uncontrollable growth of algae [7]. cisadane river is used because it has an abundance of 19 types of phytoplankton and 10 types of zooplankton [8]. domestic wastewater used in the experiment obtained from mixed influent domestic wastewater treatment plant. acclimatization was carried out to adjust microalgae in domestic wastewater. acclimatization was done by adding 0,3-gram sugar and wastewater with a ratio of 50:50 (300 mg/l sugar: 300 mg/l cod). the running stage was carried out with 100% domestic wastewater. the volume of water in the reactor used was 5l. the volume of chlorella sp. and algae mix was 20% of total volume reactor. air was flowed into the reactor using an aerator with an air flow rate of 15 liters/minute. uv lamp used was a combination of uv a and uv b lamps. pollutant parameter measurements were carried out at 0 4 8 and 24 hours. measurement of nh3-n and po4-n nutrient parameters were done by phenate method (sni 06-6989.30-2005) and ascorbate method (sni 06-6989.31-2005), respectively. 3. result and discussion 3.1 nh3-n removal the measurement results of nh3-n values in figure 1a, showed that there was a decrease in nh3n value during the cultivation of chlorella sp. and algae mix. the nh3-n content in wastewater was successfully reduced by 54.9% and 49%. the decrease of nh3-n is caused by ammonia in the waste reacting to form ammonium [9], ammonium formation reaction occurs as equation 1. the removal of ammonia-nitrogen can increase because the form of ammonium. nh3+h2o→nh4oh→nh4+oh (1) the higher removal was obtained from the cultivation of chlorella sp. reaching 98.7-99.8% with piggery wastewaters media [10] and 80.62% with domestic wastewater media [9]. the same results were produced in swine wastewater treatment with chlorella vulgaris producing 40-90% nh3-n removal [11]. this study less of nh3-n removal because the cod/nh3n ratio very high with 678 mg/l/7,81 mg/l. cod/nh3-n ratio or c/n very important to growth of microorganism [12]. civil and environmental science journal vol. iii, no. 01, pp. 031-036, 2020 33 integration of algae in wastewater treatment system can applied to improve the efficiency of the nh3n removal in wastewater [13]-14]. 3.2 po4-p removal orthophosphate (po4-p) showed that there was a decrease reaching 70.2% in chlorella sp. and 57.1% in algae mix (figure 1b). this result contrasted with po4-p removal with chlorella vulgaris of previous studies, which reduced only 4.30% of po4-p [11]. the results of other studies mentioned the efficiency value of chlorella sp. reached 90% with mixed domestic-industrial wastewater media [15]. figure 1a. nh3-n removal figure 1b. po4-p removal figure 1. nutrient concentrations of nh3-n and po4-p in the cultivation of microalgae for domestic wastewater treatment 3.3 microalgae growth mixed liquor suspended solids (mlss) were measured periodically to determine the specific growth rate of chlorella sp. and algae mix. microalgae biomass were 85.5% and 98.9% with growth rate of 0.025 h–1 and 0.027 h–1 for chlorella sp. and algae mix, respectively. these results are greater than the results of research using chlorella protothecoides and chlorella variabilis with values of 0.0022 h-1 and 0.003 h-1 on a field scale [16]. research on a laboratory scale with chlorella vulgaris produced a specific growth rate of 0.042 h−1 [17]. other results of a larger study with chlorella sp. civil and environmental science journal vol. iii, no. 01, pp. 031-036, 2020 34 were produced 0.064 h−1 [18]. this result related with n:p ratio of 15:1, on this study n:p ratio not controlled. the nh3-n/po4-p ratio on this research only 8,75:1, the nutrient ratio very important to microorganism growth [19]. figure 2. the specific growth rate equation to control the mlss values, turbidity values were measured. the value of turbidity continues to increase as seen in figure 3. this shows that the algae grow well. figure 3. changes in turbidity values of microalgae cultivation 4. conclusion domestic wastewater treatment using microalgae is effective in removing nh3-n and po4-p nutrients. microalgae biomass growth also occurs well in the domestic wastewater media. the nutrient was successfully reduced by chlorella sp. and algae mix was 54.9% and 49% for nh3-n and 70.2% and 57.1% for po4-p. chlorella sp. and algae mix growth rate are 0.025 h –1 and 0.027 h–1. references [1] natsir, m. f., selomo, m., & la ane, r. 2019. efektifitas drum of wastewater treatment (dowt) dalam mereduksi kadar phospat dan nitirit limbah cair domestik. jurnal nasional ilmu civil and environmental science journal vol. iii, no. 01, pp. 031-036, 2020 35 kesehatan, 2(2): 68-75. [2] chan, n. w. 2012. managing urban rivers and water quality in malaysia for sustainable water resources. international journal of water resources development, 28(2): 343-354. doi: 10.1080/07900627.2012.668643. [3] suswati, a. c. s. p., wibisono, g., masrevaniah, a., arfiati, d. 2012. analisis luasan constructed wetland menggunakan tanaman iris dalam mangolah air limbah domestik (greywater). the indonesian green technology journal, 1(3): 1-7. [4] saadudin, e., fitri, s. r., & wargadalam, v. j. 2016. karakteristik asam lemak mikroalga untuk produksi biodiesel. ketenagalistrikan dan energi terbarukan, 10(2): 131-140. [5] sulastri, s., henny, c., nomosatryo, s. 2019, march. phytoplankton diversity and trophic status of lake maninjau, west sumatra, indonesia. in prosiding seminar nasional masyarakat biodiversitas indonesia,vol. 5, no. 2, pp. 242-250). 5(2): 242-250. [6] fithriani, d., amini, s., melanie, s., & susilowati, r. 2015. uji fitokimia, kandungan total fenol dan aktivitas antioksidan mikroalga spirulina sp., chlorella sp., dan nannochloropsis sp. jurnal pascapanen dan bioteknologi kelautan dan perikanan, 10(2), 101-109. [7] goldman, c. r., horne, a. j. 1983. limnology. new york: mcgraw-hill book company. [8] gumelar, a. r., alamsyah, a. t., gupta, i. b. h., syahdanul, d., & tampi, d. m. (2017). sustainable watersheds: assessing the source and load of cisadane river pollution. international journal of environmental science and development, 8(7), 484. [9] rosarina, d., & rosanti, d. (2018, october). struktur komunitas plankton di sungai cisadane kota tangerang. in prosiding seminar nasional sains dan teknologi (vol. 1, no. 1). [10] kwon, g., nam, j. h., kim, d. m., song, c., jahng, d. 2019. growth and nutrient removal of chlorella vulgaris in ammonia-reduced raw and anaerobically-digested piggery wastewaters. environmental engineering research, 25(2). doi: https://doi.org/10.4491/eer.2018.442. [11] gómez-guzmán, a., jiménez-magaña, s., guerra-rentería, a. s., gómez-hermosillo, c., parra-rodríguez, f. j., velázquez, s., gonzález-reynoso, o. 2017. evaluation of nutrients removal (no3-n, nh3-n and po4-p) with chlorella vulgaris, pseudomonas putida, bacillus cereus and a consortium of these microorganisms in the treatment of wastewater effluents. water science and technology 76(1): 49-56. doi: 10.2166/wst.2017.175. [12] suryawan, i. w. k., prajati, g., afifah, a. s., apritama, m. r., & adicita, y. (2019). continuous piggery wastewater treatment with anaerobic baffled reactor (abr) by bioactivator effective microorganisms (em4). indonesian journal of urban and environmental technology, 3(1), 1-12. doi: 10.25105/urbanenvirotech.v3i1.5095. [13] suryawan, i. w. k., afifah, a. s., & prajati, g. (2019, june). pretreatment of endek wastewater with ozone/hydrogen peroxide to improve biodegradability. in aip conference proceedings (vol. 2114, no. 1, p. 050011). aip publishing llc. [14] suryawan, i. w. k., helmy, q., & notodarmojo, s. (2020, february). laboratory scale ozonebased post-treatment from textile wastewater treatment plant effluent for water reuse. in journal of physics: conference series (vol. 1456, no. 1, p. 012002). iop publishing. doi:10.1088/1742-6596/1456/1/012002 [15] hammouda, o., abdel-raouf, n., shaaban, m., kamal, m., & plant, b. s. w. t. (2015). treatment of mixed domestic-industrial wastewater using microalgae chlorella sp. journal of american science, 11(12), 303-315. [16] uyar, b., kutluk, t., & kapucu, n. 2018. growth and lipid production of two microalgae strains in pilot scale (35 l) panel photobioreactors. journal of advanced physics 7(4): 527529. doi: 10.1166/jap.2018.1463. doi: 10.1007/s10295-008-0452-4 [17] subramanian, g., yadav, g., sen, r. 2016. rationally leveraging mixotrophic growth of microalgae in different photobioreactor configurations for reducing the carbon footprint of an algal biorefinery: a techno-economic perspective. rsc advances: 6(77): 72897-72904. doi: 10.1039/c6ra14611b. civil and environmental science journal vol. iii, no. 01, pp. 031-036, 2020 36 [18] bui, x. t., nguyen, t. t., nguyen, d. d., & dao, t. s. 2018. effects of nutrient ratios and carbon dioxide bio-sequestration on biomass growth of chlorella sp. in bubble column photobioreactor. journal of environmental management, vol 219: 1-8. doi: 10.1016/j.jenvman.2018.04.109. [19] suryawan, i. w. k., siregar, m. j., prajati, g., afifah, a. s. 2019. integrated ozone and anoxic-aerobic activated sludge reactor for endek (balinese textile) wastewater treatment. journal of ecological engineering, 20(7): 169-175. doi: 10.12911/22998993/109858. open access proceedings journal of physics: conference series civil and environmental science journal vol. 5, no. 1, pp. 026-044, 2022 ol. xx, no. xx, pp. xxx-xxx, 20xx 26 analysis of changes in land use patterns for erosion and sediment prediction syamsul arifin,1,2,*, ery suhartanto2, ussy andawayanti2 1 hydrology departement, pt. globetek glory konsultan, manado, 95125, indonesia 2 water resources engineering department, universitas brawijaya, malang, 65145, indonesia *techoest.1980@gmail.com received 12-01-2022; accepted 05-03-20221ceived xx-xx-xxx; revised xxc abstract. the amprong watershed has an area of ± 252.94 km². the increasing population causes the demand for land to increase. gis analyzes changes with the factors of change that occur. the purpose of the study was to determine the pattern of land-use change in the amprong watershed on erosion and sedimentation. idrisi selva for use change analysis and swat for erosion and sediment. from the results of land cover modeling, it can be seen that the trend of forest land cover change from 2008, 2013, and 2018 continued to decline with an average of 11.69% of land cover in 2008. in contrast to settlements, it always increased by an average of 9.29%. meanwhile, land cover changes in 2018 and 2028 decreased by 21.40%, plantations decreased by 4.33%, open land decreased by 42.11%, settlements increased by 46.47%, rice fields increased by 0.60%, and shrubs increased by 4.63%. the kappa index of agreement validation shows a k standard value of 0.85 which means that the modeling is scientifically accepted. the results of hydrological modeling in 2018 were 1,021,237.49 tons/ha/year, erosion was 752,973.95 tons/ha/year and in 2028 it was 1,886,689.64 tons/ha/year, erosion was 1,069,631.09 tons/year. keywords: amprong watershed, arcswat 2012, erosion, idrisi selva, sedimentation 1. introduction the amprong river is one of the tributaries of the brantas river, with an area of ± 252.94 km². the amprong watershed is located in malang regency and malang city [1]. the population growth rate in malang regency and malang city which continues to increase for the average population growth rate of malang regency based on data from the central statistics agency of malang regency is 0.86% per year, while for the population growth rate of malang city based on the central statistics agency malang city is 0.70% per year [2]. kedung kandang weir or residents call it rolak kedung kandang, whose existence is vital for irrigation in the kedung kandang irrigation area, is the main structure in the kedung kandang irrigation area which has an area of 5160 ha that covers the area of malang city and malang regency. kedung 1 cite this as: arifin, s., ery, s., & andawayanti, u. (2022). analysis of changes in land use patterns for erosion and sediment prediction. civil and environmental science journal (civense), 5(1), 26-44. doi: https://doi.org/10.21776/ub.civense.2022.00501.4 civil and environmental science journal vol. 5, no. 1, pp. 026-044, 2022 ol. xx, no. xx, pp. xxx-xxx, 20xx 27 kandang dam coordinates 7°59'22.25" south latitude and 112°39'11.28" east longitude or downstream of the amprong watershed. weir is the main structure that functions to raise the water level to flow into the intake of the irrigation network of kedung kandang. the kedung kandang intake is at ± 600 m upstream of the weir. the water comes from the amprong river and the kalisari suppletion channel [3]. due to high erosion resulting in sedimentation upstream of the kedung kandang weir. in the dry season, the water discharge in the amprong river has decreased, impacting the level of adequacy of irrigation water needs in the kedung kandang irrigation area and the smooth production of sugar at the krebet sugar factory. these conditions can be overcome by the existence of the kalisari suppletion channel due to the high sediment upstream of the kedung kandang weir, causing the water discharge from the kalisari suppletion channel to be wasted through the weir spillway [4], [5]. changes in land cover can be analyzed by using remote sensing and geographic information systems, namely satellite images. analysis of change and modelling for land cover prediction in a watershed can be done with the assist of idrisi selva software [6], [7]. while the easiest analysis to describe complex watershed conditions is to model it. the watershed hydrological model describes the interactions between variables in the watershed context. the development of the watershed hydrological model is in line with the development of geographic information system (gis) and remote sensing technology [8]. the watershed hydrological model cover that is often used is spatial modelling based on land cover data, forecasting and predicting the condition of a change for flood, drought, erosion, sedimentation, and other conditions [2]. the soil and water assessment tool (swat) is a hydrological model developed to predict the effects of land management on the result of water, sediments, pesticide loads, and agricultural chemicals [9]–[11]. the problems that occur are caused by changes in land cover that are not well planned. therefore, there is a need for research on the impact of land-use changes on the level of erosion that causes sedimentation downstream of the amprong watershed. in the end, to obtain the right handling solution to maintain the availability of irrigation water needs in the kedung kandang irrigation area and obtain a basis for determining the watershed management in the future [5]. therefore, the purpose of the study was to assess the pattern of land-use change in the amprong watershed on erosion and sedimentation 2. data and method 2.1 data the data needed for this analysis, namely earth map scale 1: 25,000, dem map, soil type data, rain station coordinate data, daily rainfall data from the nearest rain station in the amprong watershed for 10 years (2008-2017), discharge measurement data, temperature data, solar radiation data, relative humidity data, wind speed/velocity data, landsat 7 etm imagery dated june 20th, 2008, landsat 8 oli/tirs imagery dated august 13th, 2013 and july 26th, 2018. 2.2 method 2.2.1. rain data statistical test consistency test the data consistency test was carried out to find out whether there were data deviations in the available rain data so that it could be seen whether the data was suitable to be used in the subsequent hydrological analysis or not. the double mass curve method was used [12]. homogeneity test a series of hydrological data presented chronologically as a function of the same time is called a periodic series. field data published generally are discharge data, rainfall data, and others. the data is arranged in the form of a periodic series, so it must be tested before being used for further analysis. the data testing intended are: (1) no trend test; (2) stationary test; (3) persistency test. the three stages of testing are often referred to as data filtering (data screening) [13]. civil and environmental science journal vol. 5, no. 1, pp. 026-044, 2022 ol. xx, no. xx, pp. xxx-xxx, 20xx 28 2.2.2 regional average rainfall the rainfall data for the rain station post will be used in the form of regional average rainfall data calculated using the thiessen polygon method [6], [14]. 2.2.3 land use change analysis the basic map that needs to be prepared is the earth map. the landsat 7 etm satellite imagery layout in 2008 and landsat 8 oli/tirs in 2013 and 2018 for the kali amprong watershed projected to the 49s utm (universal transverse mercator) zone. the map of the earth is used to obtain spatial administrative analysis data sourced from the geospatial information agency/badan informasi geospatial (big), digital elevation model (dem) data, which is obtained from demnas data downloaded from https://tanahair.indonesia.go.id. basic image management includes geometric and radiometric corrections and gap filling for the 2008 image because there was a gap fill due to the sensor slc off on the landsat 7 etm device in 2008. gap filling process using envi 5 software. remote sensing data is in the form of digital data. the use of the data requires special hardware and software for processing. analysis and interpretation can be conducted in two ways: a. digital processing and analysis b. visual analysis and interpretation. both of these methods have advantages and disadvantages. at least both methods are used together to complement each other. digital processing functions to read data, display data, modify and process, extract data automatically, store, design map formats, and print. digital data processing is carried out using software specifically made for this purpose. meanwhile, visual analysis and interpretation are used if digital data processing cannot be carried out and does not function properly. land use classification of landsat images is interpreted to produce land cover maps for 2008, 2013, and 2018. after obtaining the land cover map, an accuracy test was conducted in the land cover classification results. each land cover and land use class are sampled for accuracy testing. the land cover classification results in an accuracy test using the confusion matrix table. the kappa coefficient is also calculated because it is not overestimated in determining the accuracy value. the accuracy test uses very highresolution images in the form of google earth and bing maps. the method used for land change prediction analysis is markov chain with projections to 2028 idrisi selva 17.2 software. in this stage, projections are carried out by assuming that changes that will occur in the future have patterns and possibilities similar to the patterns of changes that occur over a period used by using software that can assist in managing satellite imagery for land use change analysis. validation will be carried out from the land use modeling results, namely, comparing the land use data from the modeling with the data from the interpretation of the validation test images measured by the kappa index of agreement (kappa value). 2.2.4. erosion and sediment analysis erosion and sediment analysis were estimated using the modified universal soil loss equation (musle). musle uses runoff quantities to simulate erosion and sedimentation. based on the hydrological analysis, the predictions of runoff volume and runoff peak rates are obtained then used to analyze the energy of erosive runoff. substitution of these parameters provides the following advantages: the accuracy of the model's prediction is increased, the delivery ratio is no longer needed, and a single rainfall forecast that produces sediment can be calculated. digital map is prepared and first converted to format according to arcswat 2012 requirements (change shapefile to raster). suppose the data is in the correct format. in that case, we can start running arcswat by performing the following steps: automatic watershed delineation, hru analysis, write input tables, edit swat input, swat simulation. calibration using swat-cup software with sufi-2 program. the output of the 2012 arcswat model is then calibrated and validated. calibration and validation have the aim that the simulation results resemble the real situation in the field. calibration and validation are done by comparing the simulation civil and environmental science journal vol. 5, no. 1, pp. 026-044, 2022 ol. xx, no. xx, pp. xxx-xxx, 20xx 29 results with the monthly discharge from the observation results. assessment of calibration and validation used helpful software, namely swat-cup with the sufi-2 program. the calibration and validation assessment parameters are p-factor, r-factor, ns, and r2. 3. results and discussion 3.1. hydrological analysis consistency test consistency test was carried out with two methods, the double mass curve method for rainfall data at the rain station post. figure 1. double mass curve of jabung rain station figure 2. double mass curve of pocokusumo rain station figure 3. double mass curve of kedung kandang rain station figure 5. double mass curve of tumpang rain station figure 6. double mass curve of tutur rain station figure 7. double mass curve of gunung sawur rain station civil and environmental science journal vol. 5, no. 1, pp. 026-044, 2022 ol. xx, no. xx, pp. xxx-xxx, 20xx 30 the results of this test indicate that the selected data can be used for further hydrological testing and analysis. based on figures 1 to 7 of the double mass curve at each rain station above, it is known that there is a strong relationship between the x and y variables, with the coefficient of determination between 0.9 < r2 < 1. and it can be concluded that there were no deviations in the data from each station, so there was no correction on the rain data and the data was considered consistent. homogeneity test this study tested the annual rainfall data for rain stations for the absence of trends by the spearman method using a 2-sided t-test. the recapitulation of test results is presented as follows. table 1. recapitulation of no trend test results no. post name α tc value (t test table) coefficient distribution number information 1 jabung 5% 1.86 0.76 t<tc, no tren 2 poncokusumo 5% 1.86 -1.19 t<tc, no tren 3 kedung kandang 5% 1.86 0.42 t<tc, no tren 4 tajinan 5% 1.86 0.42 t<tc, no tren 5 tumpang 5% 1.86 -0.56 t<tc, no tren 6 tutur 5% 1.86 0.36 t<tc, no tren 7 gunung sawur 5% 1.86 0.92 t<tc, no tren based on table 1, it can be seen that the overall data does not show a trend by showing tcalculate<ttable at 5% confidence level. thus, these data can be analyzed further. table 2. recapitulation of variance stability test results (f test) no. post name  fc value (f test table) coefficient distribution number information 1 jabung 5% 5.192 0.19 f < fc , stable 2 poncokusumo 5% 5.192 0.40 f < fc , stable 3 kedung kandang 5% 5.192 0.20 f < fc , stable 4 tajinan 5% 5.192 1.37 f < fc , stable 5 tumpang 5% 5.192 0.78 f < fc , stable 6 tutur 5% 5.192 1.89 f < fc , stable 7 gunung sawur 5% 5.192 0.88 f < fc , stable table 3. recapitulation of average stability test results (t test) annual period no. post name  tc value (t test table) coefficient distribution number information 1 jabung 5% 1.943 0.95 t < tc , stable 2 poncokusumo 5% 1.943 0.40 t < tc , stable 3 kedung kandang 5% 1.943 0.10 t < tc , stable 4 tajinan 5% 1.943 3.37 t < tc , stable 5 tumpang 5% 1.943 0.78 t < tc , stable 6 tutur 5% 1.943 4.89 t < tc , stable 7 gunung sawur 5% 1.943 0.88 t < tc , stable civil and environmental science journal vol. 5, no. 1, pp. 026-044, 2022 ol. xx, no. xx, pp. xxx-xxx, 20xx 31 from table 2 and table 3 above, it can be seen that the value of f calculates < the value of f table and value of t calculate < value of t table, so it can be concluded that the rainfall data for the seven rain stations used has a stable variance and average. the persistence test is an independent test for each value in the periodic series. first, the spearman method must calculate the number of serial correlation coefficients. the calculation of the persistence test with the t-test is carried out. the recapitulation of test results is presented as follows. table 4. recapitulation of persistence test results no. post name  tc value (t test table) coefficient distribution number information 1 jabung 5% 1.860 2.00 t < tc , random 2 poncokusumo 5% 1.860 8.00 t < tc , random 3 kedung kandang 5% 1.860 1.00 t < tc , random 4 tajinan 5% 1.860 5.00 t < tc , random 5 tumpang 5% 1.860 2.00 t < tc , random 6 tutur 5% 1.860 3.00 t < tc , random 7 gunung sawur 5% 1.860 0.00 t < tc , random based on table 4, it can be seen that almost all of the data are random by showing tcalculate < ttable at 5% confidence level. thus, these data can be analyzed further. 3.2 regional average rainfall analysis figure 8. map of the influence area of the amprong sub-watershed rain station post using the thiessen polygon method civil and environmental science journal vol. 5, no. 1, pp. 026-044, 2022 ol. xx, no. xx, pp. xxx-xxx, 20xx 32 table 5. amprong sub-watershed thiessen coefficient 3.3. land use change analysis from the results of the classification of landsat 7 etm+ imagery in 2008, landsat 8 oli tirs imagery in 2013, and landsat 8 oli tirs imagery in 2018 in the amprong watershed with an area of 252.94 km2 in the period 2008 to 2018 (table 5), as well as the results of observations conducted in the field for land use in the amprong watershed, land use in the amprong watershed is divided into six classes, namely garden forest, open land, settlements, rice fields, and a mixture of shrubs (figure 8). the results of the interpretation of land use then conducted the accuracy test from the classification results obtained by comparing the interpretation of field use with high-resolution image data for each year of the determined land cover. from the six classes of land use interpretation results, 60 random points were checked with the number based on the percentage of each land cover each year to prove the accuracy of the interpretation of the map made. this accuracy test aims to determine the percentage of data confidence from landsat image interpretation based on the confusion matrix table. the confusion matrix table can be presented as follows: table 6. confusion matrix of sample point for each land-use class in 2008 l a n d sa t im a g e i n te r p e ta ti o n 2 0 0 8 code google image 2008 grand total frst agrl past urbn rice rngb forest mixed (frst) 15 3 18 agricultural land generic (agrl) 12 1 13 open field/pasture (past) 4 4 urban (urbn) 1 4 5 rice (rice) 3 1 11 15 range brush (rngb) 5 5 grand total 15 19 4 5 11 6 60 table 7. confusion matrix of sample point for each land use class in 2013 l a n d sa t im a g e i n te r p e ta ti o n 2 0 1 3 code google image 2013 grand total frst agrl past urbn rice rngb forest mixed (frst) 14 1 15 agricultural land generic (agrl) 11 1 1 2 15 open field/pasture (past) 2 1 3 urban (urbn) 1 5 6 rice (rice) 1 14 2 17 range brush (rngb) 4 4 grand total 14 15 2 6 15 8 60 name are a (km 2 ) pe rs e ntase sta. jabung 70.570 27.9% sta. poncokusumo 23.018 9.1% sta. kedung kandang 23.270 9.2% sta. tajinan 5.818 2.3% sta. tumpang 80.435 31.8% sta. tutur 48.564 19.2% sta. gunung suwur 1.265 0.5% total 252.94 100% civil and environmental science journal vol. 5, no. 1, pp. 026-044, 2022 ol. xx, no. xx, pp. xxx-xxx, 20xx 33 table 8. confusion matrix of sample point for each land use class in 2018 l a n d sa t im a g e i n te r p e ta ti o n 2 0 1 8 code google image 2018 grand total frst agrl past urbn rice rngb forest mixed (frst) 14 14 agricultural land generic (agrl) 11 1 1 2 15 open field/pasture (past) 1 1 urban (urbn) 8 8 rice (rice) 2 11 13 range brush (rngb) 1 8 9 grand total 14 14 1 9 11 11 60 image classification accuracy test results (supervised classification) from the amprong watershed confusion matrix table using envi 5.1 software were evaluated for accuracy with overall accuracy results for land cover interpretation in 2008 amounted to 85.00% in 2013 equal to 81.67%, and in 2018 amounted to 86.67%, while by the kappa accuracy for 2008 amounted to 80.86%, in 2013 equivalent to 76.73%, and in 2018 amounted to 83.33%, so it can be concluded that the interpretation of land cover with basic data of landsat imagery is overall acceptable and can be used for the analysis of land cover projections in 2028 (table 6-7). land use patterns experiencing dynamic changes from the analysis of land cover change dynamics in the amprong watershed from 2008, 2013, and 2018. the trend of forest land cover change from 2008, 2013, and 2018 continues to decline with an average of 11.69% of the total land cover in 2008. this is inversely proportional to settlement cover, which is always increasing, as the average increase is 9.29% (table 9 – 10). table 9. land cover change matrix for 2008 – 2013 land cover year 2013 grand total forest mixed agricultural land generic pasture urban rice range brush forest mixed 2008 6239.61 453.20 92.52 7.14 214.26 570.03 7576.76 agricultural land generic 1.35 4041.55 16.18 355.11 1058.25 31.91 5504.35 open field/pasture 114.22 283.39 1055.97 13.28 287.35 28.36 1782.57 urban 2110.37 2110.37 rice 1205.59 9.55 4842.55 6057.69 range brush 44.15 468.90 0.18 13.11 789.51 946.70 2262.56 grand total 6399.33 6452.63 1174.39 2499.02 7191.93 1577.00 25294.30 table 10. land cover change matrix for 2013 – 2018 land cover year 2018 grand total forest mixed agricultural land generic pasture urban rice range brush forest mixed 2013 5311.77 571.09 142.75 1.42 372.30 6399.33 agricultural land generic 436.88 3904.07 34.77 112.04 570.81 1394.06 6452.63 open field/pasture 47.12 384.42 734.89 6.54 1.13 0.28 1174.39 urban 2499.02 2499.02 rice 1576.47 369.04 339.10 4826.49 80.83 7191.93 range brush 68.22 413.43 7.95 75.77 219.55 792.08 1577.00 grand total 5897.58 6515.21 512.75 3360.05 5424.18 3584.54 25294.30 civil and environmental science journal vol. 5, no. 1, pp. 026-044, 2022 ol. xx, no. xx, pp. xxx-xxx, 20xx 34 3.4. analysis of land cover change projections land cover projections were carried out using the markov chain cellular automata method. land use in 2028 is obtained by comparing changes between 2008 and 2018. model simulation was run with ca markov. projection analysis with 2008 and 2013 land use to predict the 2018 land use. this projection aims to map the 2018 predictions so that they can be validated with the actual 2018 land use maps that have been made previously. the validation results will bring up the kappa value obtained through the tools validate on the idrisi selva. the validation value described in the kappa value has a maximum level of agreement between the number of rows and columns of 1,00. kappa value > 0,81 indicates very good agreement/suitability, kappa value = 0,61–0.80 good agreement/suitability, kappa value 0.41-0.60 indicates sufficient agreement/suitability, kappa value 0,21 -0.40 indicates a weak agreement/suitability, and a kappa value <0,20 indicates a very weak agreement/suitability (landis and kock, 1977). the validation results between the actual 2018 land use and land use prediction of k standard value show the suitability/agreement of distribution and area of 85.85%. this condition indicates that our projections are acceptable (figure 9). figure 9. the results of the 2018 prediction land cover validation with the actual land cover from the image interpretation result land use in 2008 and 2018 was used to project land use in 2028. changes in forest land cover decreased by 21.40%, gardens decreased by 4.33%, open land decreased by 42.11%, settlements increased by 46.47%, rice fields increased by 0.60%. shrubs increased by 4.63% (table 11) (figure 10). table 11. land cover change matrix for 2018 – 2028 tutupan lahan year 2028 grand total forest mixed agricultural land generic pasture urban rice range brush forest mixed 2018 4833.78 75.91 27.40 0.71 0.32 959.45 5897.58 agricultural land generic 1.72 5055.92 161.42 381.60 386.49 528.06 6515.21 open field/pasture 8.02 69.54 424.53 2.09 1.98 6.59 512.75 urban 3360.05 3360.05 rice 221.03 120.21 350.08 4720.62 12.24 5424.18 range brush 121.40 334.95 19.11 246.24 2862.84 3584.54 grand total 4964.92 5757.36 733.55 4113.63 5355.66 4369.18 25294.30 civil and environmental science journal vol. 5, no. 1, pp. 026-044, 2022 ol. xx, no. xx, pp. xxx-xxx, 20xx 35 3.4. erosion and sediment analysis hru analysis process is carried out automatically by the swat program to produce the hru (hydrologic response unit). watershed delineation in the hru analysis process is based on map overlays, namely dem maps, soil maps, and land cover maps. the main river network is formed based on the watershed delineation process results. the watershed boundary with a total 252.94 km2 consists of 37 sub basins/subwatersheds. formation of hrus using threshold by percentage, where each threshold percentage is 0% with 37 sub-watersheds formed. the hrus generated from the analysis differ between land cover data in 2018, as many as 1254 hru, and data with land cover in 2028 as many as 1073 hru (figure 11). figure 11. amprong watershed subbasin figure 10. land cover 2018 (a), 2013 (b), 2018 (c), 2028 (d) (a) (b) (c) (d) civil and environmental science journal vol. 5, no. 1, pp. 026-044, 2022 ol. xx, no. xx, pp. xxx-xxx, 20xx 36 the results of hydrological modelling with land cover in 2018 in the amprong watershed show that the average erosion of the amprong watershed is 81.44 tons/ha/year with an average erosion value of 60.04 tons/ha/year (figure 10). based on the subbasin scale, the highest sedimentation occurred in subbasin number 11 amounted to157.67 tons/ha/year with an erosion value of 105.85 tons/ha/year, while the lowest sedimentation occurred in subbasin number 4 amounted to 31.12 tons/ha/year with the lowest erosion value of 24.95 tons/ha/year. meanwhile, based on the hru (hydrology response unit) scale, the highest sedimentation occurred at hru number 000110019 amounted to 1134.59 tons/ha/year, the largest erosion value equal to 777.22 tons/ha/year at hru number 000290010, while the lowest sedimentation was at hru number 00170006 amounted to 0.46 tons/ha/ year with the lowest erosion value equal to 0.40 tons/ha/year at the same hru number. surface runoff from modelling result with land cover in 2018 an average of 772.78 mm/year. the total sediment in amprong amounted to 1.021.237,49 tons/ha/year, and the erosion was equal to 752.973,95 tons/ha/year (figure 12). figure 12. comparison of simulation and observation discharge fluctuations in 2018 discharge data calibration and validation calibration and validation play a significant role in this study. with this process, the simulation results of the watershed model are expected to be close to the actual conditions. in the swat simulation process, there are many parameters used, these parameters will help in the calibration process. in this study, 8 parameters were used, among others: cn2 (scs curve number), alpha_bf (alpha factor for surface runoff), gw_delay (deceleration of groundwater flow), gwqmn (water threshold depth in shallow aquifers), gw_revap (groundwater revap coefficient) , at_ttime (lateral flow travel time), esco (soil evaporation replacement factor), usle_p (land management factor). monthly discharge data from observation discharge data taken from the amprong dam in 2010 2013 are also used as calibration input. the results of the data calibration process using sufi2.swat-cup can be seen in the calibration outputs. the 95ppu.sf2 file contains the calibration process results in graphical form, as shown in figure 13. the area of the green graph (95ppu) shows the discharge from the sufi2.swat-cup simulation result. the red line shows the best simulation results (best estimation), and the blue line indicates the observation result data at the amprong dam. the model calibration results obtained the coefficient of determination (r2) amounted to 0.84, and the value of sutcliffe model efficiency (ns) was equal to 0.54. the number of input parameters is eight parameters. later, this new parameter will be used as input in the validation process (figure 13). civil and environmental science journal vol. 5, no. 1, pp. 026-044, 2022 ol. xx, no. xx, pp. xxx-xxx, 20xx 37 figure 13. graph of calibration results for amprong watershed river discharge data (flowout 28) validation was carried out using monthly discharge data for the 2014 – 2017 amprong watershed. the validation process shows unsatisfactory results, the value of the determination coefficient (r2) was 0.86, and the nash-sutcliffe efficiency model (nse) simulation result was also unsatisfactory at -0.18. the results of this new parameter are used for the hydrological modeling process with land cover in 2028 (figure 14). the hydrological system is sometimes affected by extraordinary (extreme) events, such as heavy rains, floods, and droughts. these conditions can happen because of the extraordinary extreme river discharge as seen far above the average discharge of the previous year. figure 14. graph of the validation results of the amprong watershed river discharge data (flowout 28) for hydrological modeling with land cover in 2028, the average erosion of the amprong watershed amounted to 175.83 tons/ha/year with an average erosion value equal to 99.68 tons/ha/year. based on the subbasin scale, the highest sedimentation occurred in subbasin number 26 amounted to 317.85 tons/ha/year with an erosion value of 185.46 tons/ha/year, while the lowest sedimentation occurred in subbasin number 6 amounted to 80.68 tons/ha/year with the lowest erosion value of 53.55 tons/ha/year in subbasin number 10. meanwhile, based on the hru (hydrology response unit) scale, the highest sedimentation occurred at hru number 000260008 at 2537.09 tons/ha/year, the highest erosion value was 1180.1694 tons/ha/year at the same hru while the lowest sedimentation was at hru number 000310008 at 1.96 tons/ha/ year with the lowest erosion value of 1.66 tons/ha/year at hru number 000170004. surface runoff from modeling results with land cover in 2028 an average of 907.28 mm/year, and for the total sediment in the amprong watershed amounted to 1.886.689,64 tons/ha/year and the erosion equal to 1.069.631,09 tons/ha/year (figure 15). civil and environmental science journal vol. 5, no. 1, pp. 026-044, 2022 ol. xx, no. xx, pp. xxx-xxx, 20xx 38 3.5. critical land analysis in this study, the determination of critical land is carried out using the scoring method for land criticality determinant parameter. this scoring method refers to the regulation of the director general of watershed management and social forestry number: p. 4/v-set/2013 on the technical guidelines for the compilation of spatial data on critical lands. the parameters used are land slope conditions, vegetation cover (land coverage), erosion, and management. these parameters will be weighted and assessed for each. after that, an overlapping process is carried out to get the total weight value. 1) land coverage map making this study's land cover maps were made digitally by analyzing landsat 8 image data with image processing software. they used the ndvi (normalized difference vegetation index) process to determine the land coverage. ndvi calculates the greenness of leaves by using the ratio of the near infrared band (nir) and the red band (red). the ndvi formula is: )( )( rednir rednir ndvi + − = the data used in this ndvi process is landsat 8 imagery with band 4 (red) and band 5 (nir). later, a map of land coverage is obtained, classified into five classes. the calculation of density class interval is based on the following formula: k xrxt kl − = where kl is interval class, xt is the highest value, xr is the lowest value, and k is the desired number of classes. from the analysis results, it can be seen that the land coverage in the amprong watershed is in very good condition 20.00%, good 24.85%, moderate 31.48%, bad 19.42%, and very bad 4.25%. 2) land slope land slope data was analyzed based on dem data downloaded from the big website in the form of raster data. the land slope data in this study was obtained from the running results of arcswat on the hru file that had been carried out. with the division of slope classes into 5 classes, namely 0%-8% (flat), 8%-15% (sloping), 15%-25% (slightly steep), 25%-40% (steep), and >40% (very figure 15. errosion distribution map 2018 (a), 2013 (b), 2018 (c), 2028 (d) (a) (b) (c) (d) civil and environmental science journal vol. 5, no. 1, pp. 026-044, 2022 ol. xx, no. xx, pp. xxx-xxx, 20xx 39 steep). from the analysis results, it can be seen that the slope of the land in the amprong watershed is 27.61% flat, 20.21% sloping, 2.97% slightly step, 15.30% steep, and 23.81% very steep. 3) erosion hazard level the erosion hazard level/tingkat bahaya erosi (tbe) is calculated by comparing the level of erosion in a land unit (land unit) and the effective soil depth (solum) in that land unit. the erosion hazard level class is divided into five classes based on permenhut no. p32/menhut-ii/2009. from the results of the analysis, it can be seen that the hazard level of land erosion in the amprong watershed with class i (<15 tons/ha/year) equal to 14.87%, class ii (15-60 tons/ha/year) amounted to 36.90%, class iii (60180 tons/ha/year) 30.79%, class iv (180-480 tons/ha/year) 13.27%, and class iii (>480 tons/ha/year) 4.17%. 4) land management in relation to the preparation of critical land spatial data, these criteria need to be spatialized using or based on certain mapping units. the mapping unit used, referring to the mapping unit for productivity criteria, is the land system mapping unit. management criteria in determining critical land are divided into three classes. the map shows that land management in the amprong watershed has a good class of 44.84%, a medium class of 23.67%, and a bad class of 31.48%. from the results of the overlay parameters that determine the land criticality, it can be seen that in the amprong watershed. from the total watershed area of 25294.74 ha, most of them are categorized as critical land, namely amounted to 11.86%, slightly critical land amounted to 48.17%, potentially critical land equal to 38.25% non-critical land equal to 1.72% (figure 16 17). figure 16. land coverage map (a), erosion hazard level map (b), map of land slope (c), land management map (d) (a) (b) (c) (d) civil and environmental science journal vol. 5, no. 1, pp. 026-044, 2022 ol. xx, no. xx, pp. xxx-xxx, 20xx 40 figure 17. map of land criticality for protected areas in the amprong watershed 3.6. directions for watershed land conservation vegetative land conservation as for the types of vegetative land conservation are as follows: 1. alley cropping 2. reforestation 3. agroforestry 4. relay cropping 5. planting the cover crops as green manure 6. living fence 7. mixed garden 8. strip cropping strip cropping is the planting of two or more types of plants in alternating strips between the main crop and the ground cover crop. this system is applied to land with slopes of 15-40%. the effectiveness of vegetative conservation with strip cropping conservation methods in the amprong watershed can be seen to be able to reduce sediment in the watershed by 8.61% from 1.069.631,01 tons/ha/year (403.634,29 m3/year) to 977.506,68 tons/ha/year (368.870,44 m3/year) 9. riparian buffer strip (filter strip) riparian buffer/filter strip functions to preserve the function of the river by holding back or capturing eroded soil (mud) as well as nutrients and chemicals including pesticides that are carried away from the land on the left and right of the river so that they do not enter the river. the effectiveness of vegetative conservation with the filter strip conservation method in the amprong watershed is not able to reduce sediment in the watershed but can reduce the sedimentation rate by 29% from 1,886,689.64 tons/ha/year to 1,334,937.30 tons/ha/year. 10. mulch 11. environmental greening civil and environmental science journal vol. 5, no. 1, pp. 026-044, 2022 ol. xx, no. xx, pp. xxx-xxx, 20xx 41 mechanical land conservation this method is an effort to conserve soil by using soil management techniques and civil structure construction which are expected to reduce the rate of water erosion. the general methods used in this method among others: 1. contour tillage the soil tillage parallel to the contour lines and form small ridges that slow down the flow of water and increase water infiltration. the effectiveness of mechanical conservation with the contour tillage conservation method in the amprong watershed. from the results of the swat model, it is known that it is able to reduce sediment in the watershed by 48.91% from 1.069.631,01 tons/ha/year (403.634,29 m3/year) to 546.499,59 tons/ha/year (206.226,26 m3/year) 2. terracing it is the creation of terraces on sloping land to reduce the angle of the land so that erosion can be minimized. the effectiveness of mechanical conservation with the terracing conservation method in the amprong watershed. from the results of the swat model, it can be seen that it can reduce sediment in the watershed by 31.57% from 1.069.631,01 tons/ha/year (403.634,29 m3/year) to 731.976,44 tons/ha/year (276.217,52m3/year) 3. guludan/bedengan 4. checkdam it is an activity to stem the flow of water through a ditch so that the eroded material can be retained and deposited. mechanical conservation is recommended in locations with severe/heavy and very severe/heavy erosion hazard levels (tbe). the effectiveness of mechanical conservation in the amprong watershed can be determined by reducing sediment that comes out of the outlet of the amprong watershed. the swat model results with potential sediment that can be accommodated from the twenty-eight planned check dams. sediment outflow at the outlet of the amprong watershed from the hydrological model (swat) was 1,069,630.87 tons/year or 403.634.29m3/year. by building twenty-eight check dams at these locations, it is able to reduce sediment by 397,757.39 tons/year or 162.406,97m3/year (40.24%) of the total sediment in the amprong watershed (table 12 – 13)(figure 18). table 12 location of the check dam placement no. check dam no. subdas coordinate no. check dam no. subdas coordinate x y x y 1 1 693160.28 9121312.30 15 16 695893.33 9118972.83 2 1 694246.35 9124583.93 16 21 697369.06 9118364.83 3 2 693302.98 9121176.02 17 21 699956.41 9118184.89 4 2 694178.03 9122413.08 18 21 701712.65 9118412.73 5 2 695012.98 9122132.23 19 22 695644.59 9117922.45 6 5 695747.53 9120459.05 20 22 697241.36 9117150.14 7 5 698367.93 9121213.79 21 22 696852.14 9116779.90 8 5 697358.41 9120621.74 22 29 703429.77 9116517.85 9 13 699315.37 9119160.82 23 29 707598.42 9117852.63 10 13 700925.99 9120432.42 24 35 697421.73 9112261.15 11 13 701332.92 9120377.82 25 35 699804.52 9113514.25 12 13 700953.20 9119969.61 26 36 694767.18 9113704.72 13 16 694995.10 9118869.50 27 36 696747.72 9112080.78 14 16 696709.74 9119485.46 28 36 695333.23 9112840.23 civil and environmental science journal vol. 5, no. 1, pp. 026-044, 2022 ol. xx, no. xx, pp. xxx-xxx, 20xx 42 figure 18. map of the location of check dam placement in the amprong watershed 4. conclusion based on the results of data analysis, modeling, and discussions that have been carried out, the following conclusions can be drawn: the land cover classification results in 2008 to 2018 show a dynamic changing trend. the trend of changes in forest land cover from 2008, 2013, and 2018 continued to decline with an average of 11.69% of the total land cover in 2008. this result is different from the 2008 land cover, which has consistently increased, while the average increase is 9, 29%. from land cover change modeling for 2028, forest land cover changes decreased by 21.40%, gardens decreased by 4.33%, open land decreased by 42.11%, increased by 46.47%, rice fields increased by 0.60%, and shrubs increased 4.63%. the results of hydrological modeling with land cover in 2018 in the amprong watershed, the value of surface runoff, total sediment, and erosion increased in 2028 in the amprong watershed, the amount of surface runoff from the modeling results with land cover in 2028 an average of 907.28 mm/year, and for the total sediment in amprong watershed increased by 85.75% to 1,886,689.64 tons/ha/year and erosion increased by 42.05% to 1,069,631.09 tons/ha/year. non-critical land is equal to 15.66%. critical potential land is 49.35%, slightly critical land is 29.33%. critical land by 5.66%, and very critical by 0.01%. as a conservation recommendation in handling the amprong watershed by applying vegetative and mechanical conservation. the results of the analysis and simulation of hydrological models using vegetative and mechanical methods are quite effective in reducing the impact caused by cover changes, namely the increase in sediment in the amprong watershed. civil and environmental science journal vol. 5, no. 1, pp. 026-044, 2022 ol. xx, no. xx, pp. xxx-xxx, 20xx 43 table 13 the effectiveness of the application of vegetative and mechanical conservation information average total sedimen t total erosion effectiveness sediment (ton/ha/year) erosion (ton/ha/year) rain (mm/year) runnoff (mm/year) (ton/ha/year) (ton/ha/year) m3/year condition in 2018 81.44 60.05 2246.94 772.78 1,021,237.49 752,973.95 284,141.11 condition in 2028 175.83 99.69 2262.66 907.29 1,886,689.64 1,069,631.01 403,634.29 conditions in 2028 with strip cropping conservation 130.85 91.10 2262.66 775.82 1,404,042.95 977,506.68 368,870.45 8.61% conditions in 2028 with terracing conservation 112.12 68.22 2262.66 738.04 1,203,026.41 731,976.44 276,217.53 31.57% conditions in 2028 with filter strip conservation 124.41 99.69 2262.66 907.29 1,334,937.30 1,069,631.01 403,634.29 0.00% conditions in 2028 with countouring conservation 50.93 68.62 2262.66 572.55 736,337.07 546,499.60 206,226.26 48.91% construction of check dam at 28 points 397,757.39 162,406.97 40.24% references [1] s. utami, soemarno, surjono, and m. bisri, “disaster risk and adaptation of settlement along the river brantas in the context of sustainable development, malang, indonesia,” procedia environ. sci., vol. 20, pp. 602–611, 2014, doi: 10.1016/j.proenv.2014.03.073. [2] a. c. cindy harifa, m. sholichin, and t. b. prayogo, “analisa pengaruh perubahan penutupan lahan terhadap debit sungai sub das metro dengan menggunakan program arcswat,” j. tenik pengair., vol. 008, no. 01, pp. 1–14, may 2017, doi: 10.21776/ub.jtp.2017.008.01.01. [3] f. u. hasanah, r. wirosoedarmo, and b. suharto, “pemetaan risiko bencana tanah longsor di sub daerah aliran sungai amprong,” j. sumberd. alam dan lingkung., vol. 4, no. 3, pp. 10–17, dec. 2017, doi: 10.21776/ub.jsal.2017.004.03.2. [4] a. riyadi, a. rachmansyah, and b. yanuwiadi, “water carrying capacity approach in spatial planning: case study at malang area,” j. pembang. dan alam lestari, vol. 9, no. 1, pp. 45– 50, feb. 2018, doi: 10.21776/ub.jpal.2018.009.01.08. [5] l. m. limantara, d. h. harisuseno, and v. a. k. dewi, “modelling of rainfall intensity in a watershed: a case study in amprong watershed, kedungkandang, malang, east java of indonesia,” j. water l. dev., vol. 38, no. 1, pp. 75–84, sep. 2018, doi: 10.2478/jwld-20180044. [6] a. k. batar and t. watanabe, “landslide susceptibility mapping and assessment using geospatial platforms and weights of evidence (woe) method in the indian himalayan region: recent developments, gaps, and future directions,” isprs int. j. geo-information, vol. 10, no. 3, p. 114, feb. 2021, doi: 10.3390/ijgi10030114. [7] v. mishra, p. rai, and k. mohan, “prediction of land use changes based on land change modeler (lcm) using remote sensing: a case study of muzaffarpur (bihar), india,” j. geogr. inst. jovan cvijic, sasa, vol. 64, no. 1, pp. 111–127, 2014, doi: 10.2298/ijgi1401111m. [8] h. haas, l. kalin, and p. srivastava, “improved forest dynamics leads to better hydrological predictions in watershed modeling,” sci. total environ., vol. 821, p. 153180, may 2022, doi: 10.1016/j.scitotenv.2022.153180. [9] y. liu, g. cui, and h. li, “optimization and application of snow melting modules in swat model for the alpine regions of northern china,” water, vol. 12, no. 3, p. 636, feb. 2020, doi: 10.3390/w12030636. civil and environmental science journal vol. 5, no. 1, pp. 026-044, 2022 ol. xx, no. xx, pp. xxx-xxx, 20xx 44 [10] r. haribowo, u. andawayanti, and r. d. lufira, “effectivity test of an eco-friendly sediment trap model as a strategy to control erosion on agricultural land,” j. water l. dev., vol. 42, no. 1, pp. 76–82, 2019, doi: 10.2478/jwld-2019-0047. [11] h. yamashita et al., “toxicity test using medaka (oryzias latipes) early fry and concentrated sample water as an index of aquatic habitat condition,” environ. sci. pollut. res., vol. 19, no. 7, pp. 2581–2594, aug. 2012, doi: 10.1007/s11356-012-0906-0. [12] m. aslam and m. albassam, “presenting post hoc multiple comparison tests under neutrosophic statistics,” j. king saud univ. sci., vol. 32, no. 6, pp. 2728–2732, sep. 2020, doi: 10.1016/j.jksus.2020.06.008. [13] j. lilienthal, r. fried, and a. schumann, “homogeneity testing for skewed and cross-correlated data in regional flood frequency analysis,” j. hydrol., vol. 556, pp. 557–571, jan. 2018, doi: 10.1016/j.jhydrol.2017.10.056. [14] c.-h. liaw and y.-c. chiang, “dimensionless analysis for designing domestic rainwater harvesting systems at the regional level in northern taiwan,” water, vol. 6, no. 12, pp. 3913–3933, dec. 2014, doi: 10.3390/w6123913. open access proceedings journal of physics: conference series civil and environmental science journal vol. 05, no. 02, pp. 235-249, 2022 235 farmers' social capital in supporting sustainable agriculture: the case of pujon kidul tourism village, indonesia achmad t. nugraha1*, rahmawati2, aidha auliah2, gunawan prayitno2 1department of agribusiness, universitas islam negeri syarif hidayatullah, jakarta, indonesia 2department of regional and urban planning, faculty of engineering, universitas brawijaya, malang, indonesia achmad.tjachja@uinjkt.ac.id received 13-09-2022; accepted 26-10-2022 abstract. pujon kidul village is a village with the potential for the main agricultural sector, which is determined and developed into a pujon kidul tourism village. tourism villages that are developed need to support themselves to maintain sustainability. tourist villages that do not pay attention to the sustainability aspect will threaten the social and economic conditions of the community, especially the farming community, which makes up the majority of rural communities. therefore, supporting sustainable agriculture that can balance sustainable tourism is necessary. in achieving sustainable agriculture, social capital is an important capital that must be prepared. why is that because social capital is the main force to empower communities in development? therefore, this study aims to examine the characteristics and conditions, and factors forming the social capital of the farming community of pujon kidul tourism village. the data collection method used a questionnaire aimed at 221 respondents. then the results of the questionnaire were described and analyzed by cfa analysis. the research finding is that the characteristics of farmers in pujon kidul tourism village have low economic welfare. however, the social capital of the farming community is in good condition, which can be used in determining the right approach to the farming community of pujon kidul tourism village based on the factors that form the community's social capital in supporting sustainable agriculture. keywords: social capital, rural tourism, sustainable agriculture, community 1. introduction pujon kidul village is a village with potential for the main agricultural sector, and this village has succeeded in developing its potential and attractiveness of the village into a tourist attraction so that it brings tourists and has been designated as a pujon kidul tourism village [1]. the success of this tourist village has received various awards and benefited the village's inhabitants. these benefits are in the form of new livelihoods in the tourism sector to open new jobs, reduce unemployment and increase the welfare of rural communities [2], [3]. in its development, the village focuses not only on tourist objects by turning the village into a tourist village. each activity can make the tourist village more selfsufficient, provided that the activities of tourist villages do not conflict with the significant pursuits of the community, such as agriculture [4]–[6]. a tourism village that is increasingly developing and sustainable will have an impact and change on the village, such as changes in land use, changes in civil and environmental science journal vol. 05, no. 02, pp. 235-249, 2022 236 livelihoods, changes in lifestyle, changes in the socio-economic conditions of the community, and so on [7]–[11]. the community's perception of the socio-economic impact of the development is crucial. the community's perception will influence its decision to support or not support the existing development in the community area. in short, people's perceptions are influenced by how people view development based on the condition of their social capital. social capital will affect how local communities respond to growth and development in the village [12]. the development aims to improve the community's welfare and build material facilities and humans as objects of development [13]. the development of social capital is one of the most important capitals, where social capital consists of trust, norms, and networks [14]. social capital is significant for each individual; the benefits of attachment to each other in the form of trust will provide convenience for individuals in living life. moreover, rural communities generally have strong beliefs and an immediate sense of kinship [15]. various benefits of social capital for rural communities are social capital as a means of providing mutual assistance to fellow farmers [16], sharing benefits fairly [17], reducing the poor [18], and managing village natural resources [19]. good and high social capital conditions are the main things that must be prepared to create conditions for people who are ready to take steps for progress and protect common interests. good social capital conditions will facilitate cooperation in carrying out collaboration between actors. social capital will also affect the attitudes and behaviour of individuals in society when faced with change or a problem [20]–[22]. sustainable agriculture is vital in supporting and compensating for transforming a village into a tourism village [23], [24]. sustainable agriculture is an action taken to maintain environmental, social, and economic sustainability in an integrated manner. it is not only related to the environment and technological advances but also to the socio-economic side of society [25]. sustainable agriculture is a form of business carried out by farmers and actors involved in managing agriculture by maintaining and maintaining what is there for today and in the future. it is crucial to support sustainable agriculture because agriculture is the primary driving sector in rural economic development and growth. sustainable agriculture will encourage the socio-economic conditions of sustainable rural communities as well. [26]. in rural communities, social capital helps promote the diffusion of irrigation technologies and the spread of green agricultural technologies [27] [28]. social capital builds relationships with other people and sustains them over time, enabling people to work together to achieve things they could not or would have had difficulty achieving on their own. social capital is productive, making it possible to complete some goals that cannot be achieved without it [29], [30]. social capital in the form of values, culture, and cognition is social capital that includes forms of empathy, a sense of obligation, trust, reciprocity, cultural identity, and mutually beneficial relationships. all concepts contained in social capital can be applied to agricultural activities [31]. sustainable agriculture can provide food and other resources for the world's growing population, which is essential for human survival and every human activity. however, several problems threaten the ability of agriculture to meet human needs now and in the future. it includes climate change; severe loss of biodiversity; land degradation due to soil erosion, compaction, salinity, and pollution; depletion and pollution of water resources; increase in production costs, reduction in the number of livestock, and associated reductions in poverty and rural population [32]. sustainable agricultural development is a process to optimize the benefits of natural and human resources to remain available in the future and adapt to changes [33], [34]. sustainable agricultural development is achieved using long-term social capital. first, carry out agricultural development to increase farmers' income and welfare. second, developing agricultural institutions in the local area, in the technical field, in the form of appropriate technology, environmental conservation, and based on local community knowledge. third, resources must synergize, including social capital, to improve the welfare of farmers and increase production and selling prices. finally, some institutions support and contain procedures for a series of interests [35]–[37]. it is important to understand all aspects of sustainable agriculture, as farmers, extension workers, policymakers, and other stakeholders need to understand the term's meaning to put it into practice [36] [38]. sustainable agriculture requires not only the preservation, protection, and enhancement of natural resources but also the enhancement of human and social capital [39], [40]. sustainable agriculture aims to improve the quality of life. a proactive, civil and environmental science journal vol. 05, no. 02, pp. 235-249, 2022 237 professional, and participatory approach to sustainable agriculture is needed based on high community social capital [41], [42]. 2. material and methods 2.1. research location the location of this research is pujon kidul village, pujon district, malang regency. this village is one of the villages designated as a tourist village in indonesia. it has succeeded in developing its potential and attractive objects to attract tourists to visit and enjoy the beauty of tourist villages (see figure 1). the economy of the pujon kidul tourism village community is predominantly the agricultural sector, with the establishment of this village as a tourist village creates opportunities to improve the economy through the tourism sector. the agricultural sub-sector in pujon kidul tourism village includes horticultural crops with many carrots, cabbage, food crops with many rice plants, and animal husbandry with cattle farming. figure 1. view of pujon kidul tourism village. 2.2. research instrument data collection was carried out by the primary survey method through questionnaires and the secondary survey method through observation. the population in this study was 1,250 kk (head of family) in pujon kidul village. determination of the number of samples based on the isaac and michael table with a degree of error of 10% so that the total number of samples is 221/kk. a sampling technique using proportionate stratified random sampling was used to obtain an even number of samples in each hamlet. the sample was divided into three hamlets in pujon kidul village, including krajan hamlet, with a selection of 153 families. maron hamlet with a sample of 50 families, and tulungrejo hamlet with a sample of 18 families. data collection by observation was carried out by making direct visits to the research location, namely pujon kidul tourism village, to take documentation of the physical condition of pujon kidul tourism village. data collection with a questionnaire aimed at 221 households seeks to obtain data related to the characteristics of respondents who work as farmers and the characteristics of farmers' social capital. the questionnaire design contains questions related to the characteristics of the respondents, namely gender, age, education level, and income level. then questions related to the characteristics of social capital are related to trust, norms, and networks, with a total of 14 question items. respondents can choose answers to questions based on a 5-point likert scale, which consists of answer choices strongly disagree (sd=1), disagree (d=2), neutral (n=3), agree (a=4), strongly agree (sd =5). civil and environmental science journal vol. 05, no. 02, pp. 235-249, 2022 238 2.3. analytical methods the analytical techniques used in this study are descriptive statistics analysis and confirmatory factor analysis (cfa) with amos software. first, descriptive statistics analysis is used to describe the characteristics of the respondents of the farming community, which consists of the characteristics of gender, age, education level, and income level. also, it describes the characteristics of the condition of farmers' social capital, which consists of farmers' trust characteristics, the state of the norms that are adhered to, and the condition of the farmer network. then the use of cfa analysis to determine the factors or indicators forming the social capital of the pujon kidul tourism village community. social capital consists of 3 sub-variables: trust, norms, and networks. these three sub-variables are variables used in measuring social capital. the measurement is carried out on these three variables using secondorder cfa with the maximum likelihood estimation analysis technique based on the number of samples. in the cfa analysis, a factor is declared significant. it can become a variable forming factor if it meets the requirements of an important test with a cr value (≥1.967) and a p value (≤0.05). it is also declared valid if it meets the validity test requirements with a loading factor value (≥0.50). if a factor does not meet these requirements, then the factor must be discarded. after all the factors are declared valid, the next step is to test the goodness of fit. in the goodness of fit test, a model is feasible if it meets at least 4 to 5 goodness of fit criteria. 3. result and discussion 3.1. characteristics of respondents the characteristics of farmer respondents in this study were divided into gender, age, education level, and income level. the characteristics of farmer respondents based on gender are divided into 2; namely, the male sex amounted to 153 people with a percentage of 69%, and the female sex amounted to 68 people with a percentage of 31%; this shows that most men work as farmers (figure 2a). agriculture is an identical part of the village, an area dominated by vast rice fields. furthermore, the village community generally does not differentiate gender in working as farmers. it is considered normal because most workers in the village are farmers. characteristics of farmer respondents based on age are divided into 2, namely productive age with a range of 15-64 years total of 190 people with a percentage of 86%, and unproductive age amounting to 31 people with a percentage of 14%; this shows that most farmers are of productive age (figure 2b). the productive age that is owned can be a potential because, with individuals who have a productive age, the individual is considered capable of working and producing something and can be involved in development. the characteristics of farmer respondents based on education level are divided into 4: primary school education level is 160 people with a percentage of 73%, junior high school education level is 51 people with a percentage of 23%. the high school education level is seven people, with a percentage of 3%, and the diploma education level is three people, with a percentage of 1%; this shows that many farmers have a low level of education (figure 2c). education in the village is generally considered not an obligation, so it is not surprising that the village community does not have a high education or even does not take education. the level of education affects the type of work and the level of income they have. the higher the level of education, the greater the opportunity to get a job with a high income. additionally, the level of education affects the mindset and acceptance of individuals towards existing changes and making innovations or creative ideas. civil and environmental science journal vol. 05, no. 02, pp. 235-249, 2022 239 figure 2. (a) gender, (b) age, (c) education, (d) income. characteristics of farmer respondents based on income level are divided into 5, namely income level <rp. 500.000, totalling 41 people with an 18% income level of rp. 500.000 – rp. 1.500.000, totalling 109 people with a 49% income level of rp. 1.500.001 – rp. 3.068.275, totalling 46 people with a 21% income level of rp. 3.068.275, totalling 19 people with a percentage of 9% and income levels >rp. 3.068.275, totalling six people with a percentage of 3%; this shows that many farmers have low-income levels and are below the regional minimum wage (rmw) of malang regency rp. 3.068.275 (figure 2d). income level affects the welfare and quality of life of individuals. the higher the income level, the more welfare will increase, and the quality of life will also improve. the income level of rural communities that mostly work in the agricultural sector is generally low, and this is due to the low level of education of rural communities, which impacts the limited ability and knowledge to innovate in agriculture. 3.2. characteristics of social capital characteristics of social capital of respondents who work as farmers are described in 3 social capital variables: trust, norms, and networks. the characteristics of social capital were obtained through a questionnaire aimed at 221 respondents, totalling 14 question items. each question consists of 5 answer choices, including strongly disagree (sd=1), disagree (d=2), neutral (n=3), agree (a=4), and strongly agree (sd=5). 3.2.1. trust. the social capital trust characteristics of farmer respondents consist of 7 indicators or factors, and each indicator consists of one question (figure 3). • question t1: do you trust your neighbours? 58% of respondents trust their neighbours. trust in neighbours is due to neighbours who help with energy, advice, money, and facilities when experiencing difficulties. civil and environmental science journal vol. 05, no. 02, pp. 235-249, 2022 240 • question t2: do you trust the newcomers to the village? 40% of respondents believe in new arrivals in the village. trust in newcomers is caused by always returning borrowed goods or money without being reminded and billed. • question q3: do you trust the village government? 42% of respondents trust the village government. trust in the village government is because the village government always provides complete, clear, and correct information without covering it up. • question q4: do you trust traditional village leaders? 51% of respondents believe in traditional village leaders. trust in traditional village leaders is because traditional leaders have traits that protect residents, are consistent, and have more profound knowledge and experience in customary science. • question q5: do you trust the village religious leaders? 37% of respondents believe in village religious leaders. trust in village religious leaders is because religious leaders have characteristics that protect residents, are consistent, and have deeper knowledge and experience in religious knowledge. • question t6: do you trust tourism institutions? 48% of respondents believe in tourism institutions. trust in tourism institutions is because the institutions provide complete and honest information in tourism management. • question t7: do you think community communication improves during covid-19? 39% of respondents feel that community communication during covid-19 has improved. community communication is getting better because communication can be done anytime and anywhere. figure 3. distribution of answers about the characteristics of social capital trust. 3.2.2. norms. characteristics of obedience to social capital norms of farmer respondents consist of 2 indicators or factors, and each indicator consists of one question (figure 4). • question n1: do you always obey the village's customary rules or norms? 49% of respondents always obey village customary rules or norms. obedience to village customary rules or norms is because the community knows and understands these customary rules or norms, which are part of living in the village. • question n2: do you often participate in traditional activities or events? t1 t2 t3 t4 t5 t6 t7 0 20 40 60 80 100 120 140 strongly disagree disagree neutral agree strongly agree civil and environmental science journal vol. 05, no. 02, pp. 235-249, 2022 241 42% of respondents participated in traditional activities or events 5-6 times. participation in traditional village activities is because the community feels that these activities are a tradition that must be carried out and strengthen harmony and cohesiveness between communities. figure 4. distribution of answers about the characteristics of social capital norms. 3.2.3. networks. the social capital trust characteristics of farmer respondents (figure 5) consist of 7 indicators or factors, and each indicator consists of one question. • question j1: are you willing to work with the village community? 43% of respondents are willing to cooperate with the village community. willingness to cooperate with the village community because cooperation is a form of mutual value, a habit of living in the village. the village community is accustomed to working together to achieve mutual success without expecting a personal gain. • question j2: do you often participate in religious activities in the village? 40% of respondents participated in religious activities in the village 5-6 times. participation in village religious activities is because the community feels that these activities are a tradition that must be carried out and as a form of strengthening faith, harmony, and cohesiveness between communities. • question j3: do you often participate in social activities in the village? 42% of respondents participated in social activities in the village 5-6 times. participation in village social activities is because the community feels that these activities are a tradition that must be carried out and strengthen harmony and cohesiveness between communities. • question j4: do you often give opinions during village meetings or meetings? 38% of respondents often share their opinions during village meetings or meetings. the community's willingness is to provide opinions as a form of contribution to the village. • question j5: are you willing to join a village group? 39% of respondents are willing to join the village group. the willingness of the community to join village groups is since joining provides many benefits. n1 n2 0 20 40 60 80 100 120 strongly disagree disagree neutral agree strongly agree civil and environmental science journal vol. 05, no. 02, pp. 235-249, 2022 242 figure 5. distribution of answers about the characteristics of social capital networks. 3.3. measurement model 3.3.1. results of significance test and validity test. cfa analysis in this study was conducted on the social capital variable, which is the latent variable. then the second latent variable is the sub-variable of social capital, which consists of trust, norms, and networks. therefore, cfa analysis in this study was carried out in more than 1 stage to obtain a valid model of social capital factors and can describe the factors forming the social capital of the farming community of pujon kidul tourism village. in cfa stage 1, all indicators or factors in each variable are tested and evaluated based on the requirements of the significant test and validity test. the factor requirement is said to be significant if it has a cr value (≥1.967) and a p value (≤0.05). then the conditional factor is said to be valid if it has a loading factor value (≥0.50). factors that do not meet the requirements of the significant test and validity test then the factor must be discarded. for example, in cfa stage 1, 4 factors must be removed because they do not meet the requirements of the significance test and validity test. these factors include trust in tourism institutions (t6), communication with fellow village communities (t7), participation in religious activities (nw2), and participation in village social activities (nw3) (table 1 and figure 6). table 1. results of the cfa significance test and cfa validity test. variable sub variable c.r. (≥1.96) p (≤0.05) loading factor (≥0.50) note trust t1 7.225 *** 0.748 valid t2 6.304 *** 0.580 valid t3 6.075 *** 0.549 valid t4 6.369 *** 0.589 valid t5 fixed 0.573 valid t6 1.078 0.281 0.082 invalid t7 1.133 0.257 0.087 invalid norms n1 5.116 *** 0.852 valid n2 fixed 0.966 valid nw1 nw2 nw3 nw4 nw5 0 20 40 60 80 100 strongly disagree disagree neutral agree strongly agree civil and environmental science journal vol. 05, no. 02, pp. 235-249, 2022 243 variable sub variable c.r. (≥1.96) p (≤0.05) loading factor (≥0.50) note networks nw1 8.771 *** 0.847 valid nw2 4.957 *** 0.384 invalid nw3 4.302 *** 0.328 invalid nw4 8.788 *** 0.858 valid nw5 fixed 0.590 valid figure 6. cfa model stage 1. in cfa stage 2, after knowing the factors that were declared invalid because they did not meet the requirements for the significance test and validity test, the next step in cfa stage 2, the invalid factors were discarded. after the invalid factors are removed, all the factors are declared valid because they have met the significant and accurate test. so, in this phase 2 cfa, ten factors form the social capital of the farming community of pujon kidul tourism village. these factors include trust in fellow village communities (t1), trust in new village people (t2), trust in village officials or village government (t3), trust in traditional village leaders (t4), and trust in village religious leaders (t5). the norms factor consists of obedience to village customary rules (n1) and attendance in village traditional activities or events (n2). the network items consist of willingness to build cooperation to achieve mutual success (nw1), activeness in giving opinions during village meetings or meetings (nw4), and participation in a village group (nw5) (table 2 and figure 7). table 2. results of the cfa significance test and cfa validity test in the second stage. variable sub variable c.r. (≥1.96) p (≤0.05) loading factor (≥0.50) note trust t1 7.229 *** 0.752 valid t2 6.295 *** 0.579 valid t3 6.068 *** 0.548 valid t4 6.399 *** 0.593 valid civil and environmental science journal vol. 05, no. 02, pp. 235-249, 2022 244 variable sub variable c.r. (≥1.96) p (≤0.05) loading factor (≥0.50) note t5 fixed 0.573 valid norms n1 4.795 *** 0.842 valid n2 fixed 0.977 valid networks nw1 8.483 *** 0.837 valid nw4 8.450 *** 0.880 valid nw5 fixed 0.576 valid figure 7. cfa model stage 2. 3.3.2. goodness of fit. based on cfa stage 2, 10 factors are declared significant and valid. these factors mean that they can describe the factors that form the social capital of the farming community of pujon kidul tourism village. then the next step is to do the goodness of fit test. a model will be declared feasible in the goodness of fit test; if it meets the minimum requirements of the 4-5 goodness of fit index. the goodness of fit test results on the cfa stage 1 meets the five requirements of the goodness of fit index. while the results of the goodness of fit test on the cfa stage 2 meet the six requirements. so, it can be concluded that the phase 2 cfa model is the most appropriate for describing the factors forming the social capital of the farming community of pujon kidul tourism village (see table 3). table 3. the goodness of fit test cfa stage 1 and cfa stage 2. cfa stage 1 cfa stage 2 the goodness of fit index cut of value results note the goodness of fit index cut of value results note chi-square <a.df (a=0.005) 188.795 (<df=74=109.074) poor fit chi-square <a.df (a=0.005) 58.540 (<df=74=56.328) poor fit civil and environmental science journal vol. 05, no. 02, pp. 235-249, 2022 245 the goodness of fit index cut of value results note the goodness of fit index cut of value results note probability ≥ 0.05 0.000 poor fit probability ≥ 0.05 0.003 poor fit cmin/df ≤ 2.00 2551 good fit cmin/df ≤ 2.00 1.829 good fit gfi ≥ 0.90 0.890 good fit gfi ≥ 0.90 0.949 good fit agfi ≥ 0.90 0.844 good fit agfi ≥ 0.90 0.913 good fit tli ≥ 0.90 0.845 good fit tli ≥ 0.90 0.952 good fit cfi ≥ 0.90 0.874 good fit cfi ≥ 0.90 0.966 good fit rmsea ≤ 0.08 0.084 poor fit rmsea ≤ 0.08 0.061 good fit the characteristics of the respondents are associated with the characteristics of social capital for trust. from the characteristics of these respondents, it can be concluded that the farming community of pujon kidul tourism village, the majority of which are productive men, has an elementary school education level. therefore, they have an income below the umk and tend to trust fellow village communities, religious leaders and customs, and village institutions and government. generally, rural communities have low levels of education, making it easy to trust others. people have insufficient knowledge, so they trust others who have known for a long time or have a higher education level than themselves. likewise, the characteristics of the respondents are associated with the characteristics of social capital for trust. therefore, with the characteristics of these respondents, it can be concluded that the farming community of pujon kidul tourism village, the majority of which are men of productive age, have an elementary school education level, and have an income below the umk, tend to obey the rules. therefore, village customs and attending traditional village activities have become a habit of living in the village. then the characteristics of the respondents are associated with the characteristics of social capital for the network. therefore, with the characteristics of these respondents, it can be concluded that the farming community of pujon kidul tourism village, the majority of which are men of productive age. they have an elementary school education level and an income below the umk. they tend to cooperate with the village community and are willing to contribute by giving opinions during village meetings or meetings and joining the group. based on the results of the factors that form trust in the social capital of farming communities, pujon kidul tourism village consists of the following: • valid factors for trust in fellow village communities (t1) with a loading factor value of 0.748. this factor is valid because most people, or 58%, trust their fellow citizens. • the valid factor for trust in new village people (t2) with a loading factor value of 0.580. this factor is valid because most people, 40%, have confidence in newcomers. • valid factor for trust in village officials or village government (t3) with a loading factor value of 0.549. this factor is valid because most of the community, or 42%, have confidence in the village government. • valid factor for trust in traditional village leaders (t4) with a loading factor value of 0.589. this factor is valid because most people, or 51%, have confidence in traditional leaders. • the valid factor for trust in village religious leaders (t5) with a loading factor value of 0.573. this factor is valid because most people (37%) believe in religious leaders. • the factor that forms trust in pujon kidul tourism village's farming community is trust in fellow village communities (t1), with a loading factor value of 0.748. this trust in the community is marked by the presence of neighbours who help with energy, advice, money, and facilities when experiencing difficulties. based on the results of the norm-forming factors in the social capital of the farming community, pujon kidul tourism village consists of: civil and environmental science journal vol. 05, no. 02, pp. 235-249, 2022 246 • the valid factor for obedience to village customary rules (n1) with a loading factor value of 0.852. this factor is valid because most of the community, 49%, obeys the customary rules. • valid factor for attendance in village traditional activities or events (n2) with a loading factor value of 0.966. this factor is valid because most of the community 42% attends traditional events or activities • the factor that most forms the norm in the farming community of pujon kidul tourism village, namely attendance in village traditional activities or events (n2) with a loading factor value of 0.966. the presence of the community in these traditional activities is marked by participating in traditional village activities 5-6 times because the community feels that these activities are a tradition that must be carried out and as a form of strengthening harmony and cohesiveness between communities. based on the results of network-forming factors in the social capital farming community, pujon kidul tourism village consists of: • valid factors for willingness to build cooperation to achieve mutual success (nw1) with a loading factor value of 0.847. this factor is valid because most of the community, 43%, are willing to cooperate with the village community. • the valid factor for activeness in giving opinions during village meetings or meetings (nw4) with a loading factor value of 0.858. this factor is valid because most of the community, 38%, are willing to give their opinions during village meetings or meetings. • valid factor for participation in a village group (nw5) with a loading factor value of 0.590. this factor is valid because most of the community, 39%, are members of the village group. • the factor that most forms trust in pujon kidul tourism village's farming community is activeness in giving opinions during village meetings or meetings (nw4) with a loading factor value of 0.858. the community's willingness to provide opinions is marked by the community's willingness to give opinions as a form of contribution to the village. 4. conclusions the conclusion from this study results is that most of the people of pujon kidul tourism village work as farmers, and in this study, the sample is aimed at respondents who work as farmers. it can be concluded that the respondents' male gender of 69%. most respondents have a productive age of 15-64 years, 86%. in general, rural communities are people who have a low level of education. in this study, it is proven that respondents who work as farmers have a low level of education, namely elementary school, by 73%. additionally, with the condition of the respondents who work as farmers, the majority also have a low-income level of rp. 500.000 – rp. 1.500.000 by 49%, this income is included in the low income, below the regional minimum wage (rmw) of malang regency rp. 3.068.275. based on the characteristics of the respondents, it can be concluded that the farming community of pujon kidul tourism village has low economic welfare. then the conclusion for the condition of the respondents' social capital is that the social capital of the respondents who work as farmers is in good condition, which ten factors form the social capital of the people of pujon kidul village. the good condition of social capital is evidenced by the trust between farmers and the trust in village leaders and government. the existence of trust makes farmers willing to work together to achieve mutual success and eager to contribute to the village by providing opinions and joining village groups. trust is the basis for building networks between communities, accompanied by individual awareness in obeying the rules or norms in the village and the following groups. references [1] g. prayitno, d. dinanti, a. efendi, a. hayat, and p. p. dewi, “social capital of pujon kidul communities in supporting the development of the covid-19 resilience village,” int. j. sustain. dev. plan., vol. 17, no. 1, pp. 251–257, 2022, doi: https://doi.org/10.18280/ijsdp.170125. [2] m. rahmawati, g. s. wardhani, a. purnomo, and p. glenn, “community participation to develop rural tourism in cafe sawah pujon kidul village,” vol. 404, no. icossei 2019, pp. civil and environmental science journal vol. 05, no. 02, pp. 235-249, 2022 247 314–318, 2020, doi: 10.2991/assehr.k.200214.057. [3] k. songthan, n. lertsirisakulchai, p. muangmontre, a. d. febriyanti, and a. a. romadhon, “the development of tourism based on local economic in pujon kidul village,” j. partisipatoris, vol. 2, no. 2, 2020, doi: 10.22219/jp.v2i2.11951. [4] a. e. e. sobaih, i. elshaer, a. m. hasanein, and a. s. abdelaziz, “responses to covid-19: the role of performance in the relationship between small hospitality enterprises’ resilience and sustainable tourism development,” int. j. hosp. manag., vol. 94, 2021, doi: 10.1016/j.ijhm.2020.102824. [5] s. f. fong and m. c. lo, “community involvement and sustainable rural tourism development: perspectives from the local communities,” eur. j. tour. res., vol. 11, 2015, doi: 10.54055/ejtr.v11i.198. [6] g. prayitno, a. hayat, a. effendi, h. tarno, and s. h. fauziah, “structural model of social capital and quality of life of farmers in supporting sustainable agriculture ( evidence : sedayulawas village, lamongan regency ‐ indonesia ),” 2022. [7] g. basile, m. tani, m. sciarelli, and m. a. ferri, “community participation as a driver of sustainable tourism. the case of an italian village: marettimo island,” sinergie, vol. 39, no. 1, 2021, doi: 10.7433/s114.2021.06. [8] t. j. setokoe and t. ramukumba, “challenges of community participation in community-based tourism in rural areas,” wit trans. ecol. environ., vol. 248, 2020, doi: 10.2495/st200021. [9] d. hwang and w. p. stewart, “social capital and collective action in rural tourism,” j. travel res., 2017, doi: 10.1177/0047287515625128. [10] d. hwang, w. p. stewart, and d. wan ko, “community behavior and sustainable rural tourism development,” j. travel res., vol. 51, no. 3, 2012, doi: 10.1177/0047287511410350. [11] m. y. wu, x. wu, q. c. li, and y. tong, “community citizenship behavior in rural tourism destinations: scale development and validation,” tour. manag., vol. 89, 2022, doi: 10.1016/j.tourman.2021.104457. [12] d. b. park, r. nunkoo, and y. s. yoon, “rural residents’ attitudes to tourism and the moderating effects of social capital,” tour. geogr., vol. 17, no. 1, 2015, doi: 10.1080/14616688.2014.959993. [13] m. dai, d. x. f. fan, r. wang, y. ou, and x. ma, “residents’ social capital in rural tourism development: guanxi in housing demolition,” j. destin. mark. manag., vol. 22, 2021, doi: 10.1016/j.jdmm.2021.100663. [14] r. d. putnam, “the prosperous community,” am. prospect, 1993, doi: 10.1055/s-00351569251. [15] k. he, j. zhang, j. feng, t. hu, and l. zhang, “the impact of social capital on farmers’ willingness to reuse agricultural waste for sustainable development,” sustain. dev., vol. 24, no. 2, 2016, doi: 10.1002/sd.1611. [16] e. kiptot and s. franzel, “voluntarism as an investment in human, social and financial capital: evidence from a farmer-to-farmer extension program in kenya,” agric. human values, vol. 31, no. 2, 2014, doi: 10.1007/s10460-013-9463-5. [17] j. pretty et al., “assessment of the growth in social groups for sustainable agriculture and land management,” glob. sustain., vol. 3, 2020, doi: 10.1017/sus.2020.19. [18] r. abdul-hakim, n. a. abdul-razak, and r. ismail, “does social capital reduce poverty? a case study of rural households in terengganu, malaysia,” eur. j. soc. sci., vol. 14, no. 4, 2010. [19] g. cetinkaya, a. kambu, and k. nakamura, “sustainable development and natural resource management: an example from köprülü kanyon national park, turkey,” sustain. dev., vol. 22, no. 1, 2014, doi: 10.1002/sd.528. [20] p. cheevapattananuwong, c. baldwin, a. lathouras, and n. ike, “social capital in community organizing for land protection and food security,” land, vol. 9, no. 3, 2020, doi: 10.3390/land9030069. [21] s. nosratabadi et al., “social capital contributions to food security: a comprehensive civil and environmental science journal vol. 05, no. 02, pp. 235-249, 2022 248 literature review,” foods, vol. 9, no. 11. 2020. doi: 10.3390/foods9111650. [22] h. h. chang and s. s. chuang, “social capital and individual motivations on knowledge sharing: participant involvement as a moderator,” inf. manag., vol. 48, no. 1, 2011, doi: 10.1016/j.im.2010.11.001. [23] j. a. ivars-baidal, j. f. vera-rebollo, j. perles-ribes, f. femenia-serra, and m. a. celdránbernabeu, “sustainable tourism indicators: what’s new within the smart city/destination approach?” j. sustain. tour., 2021, doi: 10.1080/09669582.2021.1876075. [24] g. prayitno, d. dinanti, i. h. hidayana, and a. t. nugraha, “place attachment and agricultural land conversion for sustainable agriculture in indonesia,” heliyon, vol. 7, no. 7, p. e07546, 2021, doi: https://doi.org/10.1016/j.heliyon.2021.e07546. [25] s. velten, n. w. jager, and j. newig, “success of collaboration for sustainable agriculture: a case study meta-analysis,” environ. dev. sustain., vol. 23, no. 10, 2021, doi: 10.1007/s10668021-01261-y. [26] k. a. segerkvist, h. hansson, u. sonesson, and s. gunnarsson, “research on environmental, economic, and social sustainability in dairy farming: a systematic mapping of current literature,” sustainability (switzerland), vol. 12, no. 12. 2020. doi: 10.3390/su12145502. [27] x. deng, m. zeng, d. xu, and y. qi, “does social capital help to reduce farmland abandonment? evidence from big survey data in rural china,” land, vol. 9, no. 10, 2020, doi: 10.3390/land9100360. [28] m. abid, g. ngaruiya, j. scheffran, and f. zulfiqar, “the role of social networks in agricultural adaptation to climate change: implications for sustainable agriculture in pakistan,” climate, vol. 5, no. 4, 2017, doi: 10.3390/cli5040085. [29] b. wu and l. liu, “social capital for rural revitalization in china: a critical evaluation on the government’s new countryside programme in chengdu,” land use policy, vol. 91, 2020, doi: 10.1016/j.landusepol.2019.104268. [30] a. t. nugraha, g. prayitno, a. w. hasyim, and f. roziqin, “social capital, collective action, and the development of agritourism for sustainable agriculture in rural indonesia,” evergreen, vol. 8, no. 1, pp. 1–12, 2021, doi: 10.5109/4372255. [31] c. d. osei and j. zhuang, “rural poverty alleviation strategies and social capital link: the mediation role of women entrepreneurship and social innovation,” sage open, vol. 10, no. 2, 2020, doi: 10.1177/2158244020925504. [32] m. a. hossain, m. n. amin, j. sultana, and m. n. a. siddique, “climate change impact on agriculture and related sustainable land management practices in bangladesh – a review,” int. j. environ. clim. chang., 2020, doi: 10.9734/ijecc/2020/v10i230181. [33] j. poveda, “insect frass in the development of sustainable agriculture. a review,” agronomy for sustainable development, vol. 41, no. 1. 2021. doi: 10.1007/s13593-020-00656-x. [34] d. el chami, a. daccache, and m. el moujabber, “how can sustainable agriculture increase climate resilience? a systematic review,” sustainability (switzerland), vol. 12, no. 8. 2020. doi: 10.3390/su12083119. [35] m. rivera, k. knickel, j. maría díaz-puente, and a. afonso, “the role of social capital in agricultural and rural development: lessons learnt from case studies in seven countries,” sociol. ruralis, vol. 59, no. 1, pp. 66–91, jan. 2019, doi: 10.1111/soru.12218. [36] j. mair and m. duffy, “the role of festivals in strengthening social capital in rural communities,” event manag., 2018, doi: 10.3727/152599518x15346132863229. [37] j. erbaugh, r. bierbaum, g. castilleja, g. a. b. da fonseca, and s. c. b. hansen, “toward sustainable agriculture in the tropics,” world dev., vol. 121, 2019, doi: 10.1016/j.worlddev.2019.05.002. [38] s. velten, j. leventon, n. jager, and j. newig, “what is sustainable agriculture? a systematic review,” sustain., vol. 7, no. 6, pp. 7833–7865, 2015, doi: 10.3390/su7067833. [39] a. trigo, a. marta-costa, and r. fragoso, “principles of sustainable agriculture: defining standardized reference points,” sustain., vol. 13, no. 8, 2021, doi: 10.3390/su13084086. civil and environmental science journal vol. 05, no. 02, pp. 235-249, 2022 249 [40] s. candia and f. pirlone, “tourism environmental impacts assessment to guide public authorities towards sustainable choices for the post-covid era,” sustain., vol. 14, no. 1, 2022, doi: 10.3390/su14010018. [41] a. artal-tur, a. j. briones-peñalver, j. a. bernal-conesa, and o. martínez-salgado, “rural community tourism and sustainable advantages in nicaragua,” int. j. contemp. hosp. manag., vol. 31, no. 6, 2019, doi: 10.1108/ijchm-05-2018-0429. [42] y. he, x. gao, r. wu, y. wang, and b. r. choi, “how does sustainable rural tourism cause rural community development?” sustain., vol. 13, no. 24, 2021, doi: 10.3390/su132413516. open access proceedings journal of physics: conference series civil and environmental science journal vol. i, no. 01, pp. 019-026, 2018 19 water management system based on zero run off policy in multi unit area (case study of menara asuransi astra in cilandak, south jakarta, indonesia) lailatul mukarromah1,2, ussy andawayanti3, tri budi prayogo3 1 master degree of water resources engineering, brawijaya university malang, indonesia 2 investment and one stop services board, jakarta, indonesia 3 water resources engineering program, brawijaya university malang, indonesia lala_vlo@yahoo.com received 07-02-2018; revised 07-03-2018; accepted 20-03-2018 abstract. water system management is an effort of planning, management, control, and supervision of runoff water that is structured and integrated in an area according with the policies. in governor regulation of jakarta capital city administration no. 43 of 2013 on the peil of building floor licence, it is explained that the implementation of the zero delta q principle is to keep the runoff remain in the area up to 100%/ zero runoff. this research is expected to develop a concept of a regional water system implementation which compares the hydrological analysis method with related regulatory methods, to obtain a technical policy that can be applied in order to meet the regional regulations based on the zero delta q concept for all to be developed areas in jakarta (south jakarta area as a pilot project). the conclusion is the calculation by hydrological analysis in accordance with the indonesian national standard regulation (sni) no. 03 2453 2002 on the procedure of planning technique of rainwater recharge wells for grounds becomes the chosen method, because it has a more detailed result and zero runoff concept can be met, so the runoff at the study site did not increase the load of grogol river. keywords: water system management, zero delta q, zero runoff, recharge wells. 1. introduction increased development, accumulation of activities, and increasing population in the jakarta resulted in increasing space cover and the decreasing of open space as a retention area. increased development such as settlements, office buildings, hotels, shops, business centers, hospitals, schools, roads, and other facilities are reduce open space rapidly. the built space proportion in south jakarta is ±77.65%, while the built space of central jakarta, west jakarta and east jakarta are respectively ±72.55%, 66.09%, 66, 77%. the amount of built space causes the rain that fell to the surface directly becomes rainfall runoff. in the 10-year repatriation period, the runoff contribution from south jakarta is ±30.59%, east jakarta ±30.22%, west jakarta ±18.49%, and central jakarta ±8.64% (technical data of department of water resources of jakarta capital city administration, 2015). civil and environmental science journal vol. i, no. 01, pp. 019-026, 2018 20 water system management is a planning effort, management, control, and supervision of runoff water that is structured and integrated in the regional area in accordance with the policies. according to governor regulation of jakarta capital city administration no. 43 of 2013 on the peil of building floor licence, the delta q zero principle is implemented by holding the runoff remains in the area up to 100% or drain the water out of the area to zero percent or zero runoff. according to governor regulation of jakarta capital city administration no. 20 of 2013 about recharge wells, the effort to utilize rainwater, reduce water runoff and conserve groundwater is by creating recharge wells and shelters that serve as a space to accommodate, store, and absorb rainwater that can increase the groundwater content. the increasing amount of building construction either above or below the ground has reduce the rainwater infiltration into the soil and the aquifer volume that can lead to floods and droughts. at the study site, rainfall runoff still occurs due to poorly functioning conservation building , where the runoff flow is directly directed to grogol river due to the contours of the study sites that directly lead to grogol river. therefore, a system support and drainage technology of the buildings, plots, and areas are necessary in order to generate a better zero runoff concept that can discharge runoff out of the area (grogol river) as low as possible or even zero runoff. the objective of the research is to generate a regional water system application concept that compares the hydrological analysis method with the relevant regulatory method, to obtain a technical policy that can be applied to meet the regulations based on the concept of zero delta q or zero runoff for all regions which will be developed in jakarta capital city administration, especially south jakarta. the expected benefits of the research results are to create a water management system concept that can be used as technical guidance for the owner of the activity or community in building a premise based on zero runoff policy in jakarta capital city administration, especially south jakarta. 2. material and methods 2.1. case study area building name : office, shelter, and facilities building number : 4 (four) building units building location : jl. tb. simatupang kavling 15, kelurahan lebak bulus kecamatan cilandak, jakarta selatan building use : office, trade, and service total area : 23.530 m2 development area : 10.9619 m2 roof covered area : 6.203,86 m2 pavement area : 4.415,14 m2 existing area : 12.911 m2 roof covered area : 5.532,97 m2 pavement area : 4.415,14 m2 open space area : 2.911 m2 the highest river water level from the road is +32,072 m (pp) (data measuring from the existing peil). groundwater level is 3.06 m (borlog result). 2.2. calculation of conservation building based on hydrological calculations and indonesian national standard regulation (sni) no. 03-2453-2002 in this research, three kinds of calculation alternatives are conducted in determining the amount of runoff that occurred at the study location and system management to meet the zero runoff. a. alternative i : the design discharge calculation with a return period 5th year in which all discharged at the study site is accommodated by the recharge well and the remainder is directed to civil and environmental science journal vol. i, no. 01, pp. 019-026, 2018 21 a recharge pond, assuming that land cover/soil surface is considered equal with urban business area. b. alternative ii : the design discharge calculation with a return period 5th year considering the type of land cover/ soil surface in the c calculation. the discharged entering the recharge well is only derived from the gutter/ building roof, while the runoff discharge in other land cover goes into the recharge pond through the internal drain. c. alternative iii : the design discharge calculation with a return period 5th year considering the types of every land covers/ soil surface in the c calculation. the discharged from the gutter/ building roof enters the injection well, while the runoff of other land cover goes into the retention pond through the internal drain. d. from the three alternatives (a), (b), (c) then a comparison is conducted with the calculation analysis according to the governor regulation of jakarta capital city administration about the zero runoff policies.. 3. result and discussion a. hydrological analysis calculation and indonesian national standard regulation (sni) no. 032453-2002 resulted in 3 (three) alternatives of water system management with conservation building plan: alternative i : recharge well : diameter 3 m and depth 3 m recharge well capacity 466,71 m3. number of planned recharge wells: 22 units recharge period : 4,23 days per well retention pond (rp): retention pond dimension rp i : 9m x 14m x 2m rp ii : 8m x 14m x 2m retention pond capacity 455,5 m3. retention period: 4,23 hari total recharge capacity : 922,21 m3. total open space area for conservation building : 317,40 m2. cost estimate for zero runoff concept : idr. 689.503.000,-. implementation on the field : not implementable. alternatif ii : recharge well : diameter 3 m and depth 3 m recharge well capacity 459,49 m3. number of planned recharge wells : 22 units retention pond (rp) : rp i : 8m x 12m x 2m rp ii : 8m x 13m x 2m retention pond capacity 394,63 m3. total recharge capacity : 854,12 m3. total open space area for conservation building : 294,71 m2. cost estimate for zero runoff concept : idr. 674.631.000,-. implementation on the field : implementable. alternatif iii : deep recharge well/injection well: injection well dimension (diameter 0,08 m x depth 13m) number of well : 4 unit with total capacity 541,23 m3. civil and environmental science journal vol. i, no. 01, pp. 019-026, 2018 22 retention pond (rp) : rp i : 12m x 12m x 3m rp ii : 11m x 21,2m x 2m retention pond capacity 394,63 m3. total recharge capacity : 935,85 m3. total open space area for conservation building : 139,54 m2. cost estimate for zero runoff concept : idr. 646.021.000,-. implementation on the field : implementable. b. calculation based on governor regulation of jakarta capital city administration in conservation building resulted below: total recharge volume : 978 m3. 22 units of recharge well (diameter 3m x depth 3m) with total capacity 487,9 m3. 1 unit of detention pond (8m x 8m x 2m) with total capacity 132,06 m3. retention pond (15m x 15,7m x 1,5m) with total capacity 375,65 m3. total open space area for conservation building : 489,23 m2 cost estimate for zero runoff concept : idr. 666.434.000,-. implementation on the field : implementable. c. calculation results comparison based on governor regulation and hydrological result analysis and indonesian national standard regulation (sni) no. 03-2453-2002. the three alternative calculation results with hydrological method and the indonesian national standard regulation (sni) no. 03-2453-2002 then compared with the calculation written in governor regulation. the result of governor regulation calculation is: type of calculation, structure, and soil permeability coefficients value are not discussed. the calculation is only based on the roof covered area, while the runoff of other land cover areas such as paving surface, road, garden is not calculated retention pond obligation is only for land with area of ≥ 5,000 m2. allocation of conservation building (retention ponds, recharge wells, water reservoirs) is not based on elevation/ land contour of the premises. overflow from the recharge well is still directed into the drainage channel. no calculation of the time soil takes to absorb water stored in the conservation building. the total of recharge volume is 1,078 m3. the value and certainty of zero runoff compliance is not measurable and not specified. the calculation is not based on the rework, but when compared with the return period on the hydrological analysis, it is in accordance with the return period 5th year. need more budget and open space area for conservation building. while the results of hydrological calculation and indonesian national standard regulation (sni) no. 03-2453-2002 is: type of calculation, structure, and soil permeability coefficients value are discussed. the runoff calculation is based on all covered area, including roof, paving surface, road, garden by calculating the different surface cover coefficient (c) factors. calculation and establishment of conservation building needs is based on total runoff of land area, not just a specific land area. allocation of buildings conservation (retention ponds, recharge wells, detention ponds) is based on elevation/ land contour of the premises. zero runoff compliance is completely calculated, so no runoff exits the premises, and zero run off can be achieved. the time soil takes to absorb the water contained in the conservation building is calculated, so the recharge well age can be monitored if the water is saturated. the total of recharge volume is 854,12 m3. civil and environmental science journal vol. i, no. 01, pp. 019-026, 2018 23 calculations are taken for return period 5th year, assuming the greatest risk level and the flood discharge possibility are based on the current precipitation. lower budget and less open space area for conservation building. figure 1. internal drainage network scheme of the existing area study the current situation at the study site is the rainwater runoff is directed to internal drainage and directly directed to grogol river. some recharge wells are located in basement and others are around existing buildings, but they can not be opened and can not be checked for maintenance. explanation : retention pond; injection well; manhole figure 2. zero runoff concept layout plan (based on the choosen method) r1 a : 1.011,39 m2 b : 0,3 m h : 0,2 m q : 0,02 m3/dt r2 a : 7.123,30 m2 b : 0,4 m h : 0,3 m q : 0,06 m3/dt r3, a : 1.843,1 m2 b : 0,4 m h : 0,3 m q : 0,06 m3/dt r5, a : 1.249,3 m2 b : 0,3 m h : 0,2 m q : 0,02 m3/dt r4, a : 10.119,51 m2 b : 0,5 m h : 0,4 m q : 0,13 m3/dt r6, a : 2.904,6 m2 b : 0,4 m h : 0,3 m q : 0,06 m3/dt r7, a : 9.103,50 m2 b : 0,5 m h : 0,4 m q : 0,13 m3/dt rk, a :19.223 m2 b : 0,8 m h : 0,7 m q : 0,53 m3/dt grogol river r8, a : 4.306,99 m2 b : 0,4 m h : 0,3 m q : 0,06 m3/dt r1 a : 1.011,39 m2 b : 0,3 m h : 0,2 m q : 0,02 m3/dt r2 a : 7.123,30 m2 b : 0,4 m h : 0,3 m q : 0,06 m3/dt r3, a : 1.843,1 m2 b : 0,4 m h : 0,3 m q : 0,06 m3/dt civil and environmental science journal vol. i, no. 01, pp. 019-026, 2018 24 box control internal drain retension pond soil surface cast cement cast cement aquifer roof filter box injection well fibers coral sand figure 3. zero runoff concept (based on the choosen method) table 1. comparison of governor regulation of jakarta capital city administration method with hydrological analysis (alternative iii) and indonesian national standard regulation (sni) no. 032453-2002. no. comparison descriptionn governor regulation hydrological analysis (alternative iii) and indonesian national standard regulation (sni) no. 03-2453-2002 1. recharge volume based on calculation 978 m3. 935,85 m3. 2. total recharge wells and dimension dimension : diameter 3m x depth 3m. number : 22 units deep recharge wells : diameter 0,08m x depth 13m. number : 4 units 3. retention ponds (rp) dimension : 15m x 15,69m x 1,5m. volume : 375,65 m3. obliged only for land with area of 5.000 m2. the depth and volume of the retention pond is not determined (only the area achieved). dimension : retention pond i : 12m x 12m x3m retention pond ii : 11m x 21,2m x2m volume : 394,63 m3. for all land area based on runoff that occurred at the site area. 4. conservation building overflow discharged to the main drainage/ drainage channel. no discharge/ zero runoff 5. structure and type of soil and soil permeability value not calculated calculated. the effectiveness of conservation building can be determined and obtained. 6. return period not mentioned. return period 5th year 7. type of land cover/land surface not calculated the coefficient value (c) is calculated based on the type of land cover/ soil surface for the runoff discharge calculation 8. calculation of time required by the land to absorb runoff water in conservation building. not calculated calculated based on soil type related to soil permeability coefficient value. related to the effectiveness of conservation building . 9. network and internal drainage channel dimensions. not calculated calculated to obtain drainage channel dimensions based on the volume of runoff discharge, according to the contours of the premises, and related to the planned water management system. 10. advantages. bigger recharge volume the calculation is based on the type of soil and the condition of the premises. the selection of species and quantities, civil and environmental science journal vol. i, no. 01, pp. 019-026, 2018 25 as well as age for conservation building (recharge wells, retention ponds) are very effective. decision of water management system adjusted to the condition of premises. the zero runoff concept can be achieved. lower budget for injection well. fewer land requirements for conservation area. 11. disadvantages. the runoff discharge that can be recharge is only based on roof covered area, whereas the other covered area and the type and condition of the land are not calculated. the selection of the type and number of conservation building (recharge wells, retention ponds, detention ponds) can not be effective because they are not adapted to the type and condition of the site. zero runoff has not been achieved, because there is still possible overflow from the conservation building out of the premises. more budget for recharge well. need more open space area for conservation building. requires a water management review that comes with rainfall data and soil investigation data. no. comparison descriptionn governor regulation hydrological analysis (alternative iii) and indonesian national standard regulation (sni) no. 03-2453-2002 12. conservation building options not adjusted to the type of soil and the condition of the premises, so that its effectiveness can not be achieved. adjusted to the type of soil and the condition of the premises, so that its effectiveness can be achieved. 13. implementation on the field implementable implementable 4. conclusions the conclusions obtained from the results of the discussion are as follows: each method has its own advantages and disadvantages, but in the research it is found that the result of calculation by hydrological method and indonesian national standard regulation (sni) no. 03-2453-2002 has more advantages than its disadvantages compared with governor regulation of jakarta capital city administration of method, where the calculation and result are more detailed and the zero runoff concept can be achieved, so as not to increase the load of grogol river. references arnelliya fitri, azura ulfa. 2015. the implementation of zero run off and agroforesty concept based on river discharge in belik sub watershed, yogyakarta. journal of regional and city planning institute teknologi bandung, volume 26 no. 3. (yogyakarta : gadjah mada university indonesia). badan standardisasi nasional. 2001. peraturan standar nasional indonesia (sni) 03 2453 2002 tentang tata cara perencanaan teknik sumur resapan air hujan untuk lahan pekarangan. jakarta : badan standardisasi nasional. christopher j. wals.,tim d. fletcher. matthew j. burns., 2012. urban stormwater runoff : a new class of environment flow problem. (united states of america. https://doi.org/10.1371/journal.pone.0045814). dinas tata air provinsi dki jakarta. 2015. data teknis kajian air tanah. jakarta. https://doi.org/10.1371/journal.pone.0045814 civil and environmental science journal vol. i, no. 01, pp. 019-026, 2018 26 evangelos a. baltas. 2009. climate change and associated implications for the water policy framework in the basin of venetikos. international journal of water resources development volume 25. p 491 -506. gubernur provinsi daerah khusus ibukota jakarta. 2013. peraturan gubernur provinsi daerah khusus ibukota jakarta nomor 20 tahun 2013 tentang sumur resapan. jakarta : provinsi daerah khusus ibukota jakarta. gubernur provinsi daerah khusus ibukota jakarta. 2013. peraturan gubernur provinsi daerah khusus ibukota jakarta nomor 43 tahun 2013 tentang pelayanan rekomendasi peil lantai bangunan. jakarta : provinsi daerah khusus ibukota jakarta. i. m. faisal civil engineering, s. parveen, m.r. kabir. 2006. sustainable development through groundwater management : a case study on the barind tract. international journal of water resources development, volume 21. p 425 -435. jacinta a. opara. 2016. (urp) environmental health challenges and sustainable development in nigeria: implications for policy and management. international journal of contemporary research and review, volume 7 no. 7. lizarraga mendiola l, vazquez rodriguez. g, blanco pinon . a, et. al. 2015. estimating the rainwater potential per household in an urban area: case study in central mexico. water journal, volume 7 no. 9. p 4622 – 4637. osborne. j, lambert. f, groenendijk. m. et al. 2015. reconciling precipitation with runoff: observed hydrological change in the midlatitudes. journal of hydrometeorology, volume 16 no. 6. p 2403 – 2420. s.r. barick, b.k. ratha. 2017. hydrological studies and water quality analysis around the limestone mining in the hial area of bolangir district ,odisha for the optimal use and sustainable management of available water resources. international journal of contemporary research and review, volume 8 no. 7. tewodros negash kahsay, onno kuik, roy brouwer, pieter van der zaag. 2018. the transboundary impacts of trade liberalization and climate change on the nile basin economies and water resource availability. water resources management journal, issue 3/ 2018. zhang. d, gersberg. r, wilhelm. c, et. al. 2009. decentralized water management: rainwater harvesting and greywater reuse in an urban area of beijing, china. urban water journal, volume 6 no. 5. p 375385. open access proceedings journal of physics: conference series civil and environmental science journal vol. iii, no. 01, pp. 001-009, 2020 1 using water balance to analyse water availability for irrigation with upraising surface temperature (a case study pasar baru barrage in cisadane watershed)1 dwi ariyani1, frederick josep putuhena2, dharma wira3 1 civil engineering department, faculty of engineering, pancasila university, jakarta selatan 126400, indonesia 2 civil engineering department, faculty of engineering, pembangunan jaya university, kota tanggerang selatan 15413, indonesia 3bachelor school of civil engineering and faculty of engineering, pancasila university, indonesia dwi.ariyani@univpancasila.ac.id received 06-11-2019; accepted 17-02-2020 abstract. this research determines water balance at pasar baru barrage. and conducted to see the effect of rising temperatures on water requirements. water requirement is calculated from irrigation, domestic and raw water, it is calculated by planning cropping pattern in one year. evapotranspiration was calculated using penmann modification, water availability calculated using fj mock, maximum water availability value is 11.75 m3/second. so that the water balance is obtained by surplus deficit water balance method. air temperature in the cisadane irrigation area is increasing from 1985 to 2018. the average temperature increases by 0.74°c, minimum air temperature increases by 0.8°c and the maximum increases by 0.2°c, the average evapotranspiration value decreases by 0.15 mm/day, while the average water availability decreases from 1985 to 2018 at 1.8 m3/second. amount of water needed for irrigation was 5.57 liters/second/ha. it can see that the water balance has a surplus every year, the water balance deficit only occurred in july 2015 of 0.3 m3/sec. the largest water balance occurred in march 2014 amounting to 656.97 m3/sec. the results of this study can be used as a reference in planning and developing integrated water resources buildings especially in the cisadane watershed and the ciliwung-cisadane river basin in general. keywords: water balance, ciliwung-cisadane watershed, water requirement, irrigation, water availability 1. introduction the increase in the earth's surface temperature is the real thing that must be ready to be faced by humanity on earth, now scientists continue to find out the effects of changes in surface temperature, based on the 100-year trend (1906-2005) there is an increase in the average surface temperature of the earth 0.740c +0.180c [1] according to an ongoing temperature analysis conducted by scientists at nasa’s goddard institute for space studies (giss), since 1880 the average global temperature on earth has increased by about 0.8°celsius [2], updated reports every month about changes in the earth's surface temperature can be seen on the ghcn website, ghcn analyses more than 7000 meteorology 1 cite this as: ariyani, d., putuhena, f., & wira, d. (2020). using water balance to analyse water availability for irrigation with upraising surface temperature (a case study pasar baru barrage in cisadane watershed). civil and environmental science journal, 3(1), pp.1-9. doi: https://doi.org/10.21776/ub.civense.2020.00301.1 civil and environmental science journal vol. iii, no. 01, pp. 001-009, 2020 2 stations in the world, to find out changes in surface temperature in more detail. there are 4.7 million station months of temperature data in ghcn, starting in 1701 and continuing to the present [3] according to ghcn highest temperature change it is happen in north and south earth hemisphere, while in the area tropical temperature change is not until 10c. except afrika continent, even though it’s located in the equator the temperature change it’s extremely reach until 2.5°c [4], in the north pole area temperature exchange until to 3.8°c [5, 6] research on the donau river, which is the longest river in europe, states that climate change affects all elements of the water balance: precipitation, evapotranspiration and runoff. decreasing annual precipitation by 55 mm and increasing annual evaporation by 47 mm leads to a decrease in annual availability by 102 mm in the upper danube river basin, the highest impact found in the northern edge of the alps, where water availability decreases by up to 400 mm [7] hydrological cycle is strongly influenced by the earth's surface temperature and radiation balance, high surface temperatures cause the hydrological cycle intensity, resulting in higher rates of evaporation and increasing liquid precipitation, this causes a shift from run off distribution, soil moisture, ground water, and evaporation. india predicts that without climate change demand for irrigation water will increase by around 3.5-5% in 2025, 73% of water use in india is for irrigation, in gujarat it is predicted to fall -6 to -8%, while in north-western india rainfall rises around 10% from normal, without doing good water management, it is likely that india will have a water deficit [8]. furthermore, the effect of change evaporation due to change in surface temperature is influenced by geographical location, and irrigation designation. this study aims to determine the effect of change in surface temperature over the past 30 years on water requirement by taking cases in karawang, west java, in this area the land is quite large, so further research is needed condition of the water balance. 2. material and methods 2.1. data used data used for the research is temperature, rainfall data, relative humidity, wind speed, solar, and etc. climatology data was obtained from climatology station from 1985 to 2018. the research located in koang jaya village, karawaci, tanggerang (figure 1). figure 1. area location pasar baru barrage the cisadane irrigation area (di) covers the tanggerang regency and a small part of the tanggerang city area. the water source in cisadane comes from the cisadane river trough the pasar civil and environmental science journal vol. iii, no. 01, pp. 001-009, 2020 3 baru barrage located in the tanggerang sub-district, tanggerang city. the area of di cisadane in 2004 was 22.269 ha and then reduced to 22.053 ha in 2007, and in 1988 an area of 38.634 ha. there has been a change of function in an area of 16.581 ha which is used for settlements, industry and soekarnohatta airport. figure 2. monthly rainfall graph in budiharto station from the monthly rainfall graph every year in pasar baru barage it is known that the maximum monthly rainfall occurred in february 2007 amounting to 227.5 mm (figure 2). therefore, it can be seen that rainfall is fluctuating. temperature data from the climatology station budiharto in tangerang, in the form of data of maximum, minimum and average temperature for 33 years, from 1985 to 2018. the maximum air temperature occurred in october 2002 at 37.8°c 2.2. methods for this research used the temperature and rainfall data from bmkg, temperature data is used to analyzed evapotranspiration with penman modification method. the rainfall data is for calculate water availability with mock method. using mann kendall to know temperature rise [8]. temperature is related to water availability and water demand. to calculate water requirement for irrigation, must be known in advance the value of evapotranspiration and effective rainfall. evapotranspiration is calculated based on climatological data from budiharto station using modified penman method, while reliable rainfall is calculated based on rainfall data using the basic year method, the effective rainfall value for rice plant is 70% from the reliable rainfall. calculation of irrigation water requirement in rice fields is calculated according to the formula: nfr = etc + p + wlr –re (1) where; nfr is netto field water requirement (mm/day), etc is plant evaporation (mm/day), p is percolation (mm/day) and wlr is replacement of water layer for flooding (mm/day), while re is effective rainfall. the wlr value for replacing the water layer is taken as 1,1 mm/day, the percolation value based on the type of soil is taken 3 mm. water balance calculate based on surplus deficit water balance, is mean the water available reduced by water requirement. in this study the water balance based on the mainstay discharge in the river calculated from rainfall data, compare to discharge from measurement in pasar baru barrage. the available discharge data at pasar baru barrage is obtained for five years, in year 2013 to 2017 from the cidurian-cisadane water resources management (bpsda) civil and environmental science journal vol. iii, no. 01, pp. 001-009, 2020 4 3. result and discussion 3. 1. analysis result of air temperature each to analyze air temperature and rainfall data using the mann-kendall trend test [8] [9] [10] [11]. assumed that h0 is no trend and ha there is trend. if p-value greater than alpha is mean h0 is rejected, and conversely. from the results of the trend line analysis at the average air temperature, it can be seen that the pvalue is smaller than the significant alpha level so that h0 is rejected and ha is accepted. if ha is accepted, it means that there is a trend of rising temperatures on average in the period 1985 to 2018. during the 33 years the average temperature increase occurred at 0.74°c. the graph of the average temperature rise trend can be seen in figure 3. figure 3. average air temperature graph from 1985 – 2018 at the minimum air temperature of the mann-kendall trend test it is known that p-value is smaller than the significant alpha level, it means that the alternative hypothesis ha is accept. the minimum increase in air temperature for 33 years is from 1985 to 2018 of 0,8°c. the minimum trend of rising air temperature graph can be seen in figure 4. figure 4. minimum air temperature graph from– 2018 23 24 25 26 27 28 29 30 31 0 24 48 72 96 120 144 168 192 216 240 264 288 312 336 360 384 408 432 a v a ra g e r a in fa ll ( 0 c ) month 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 0 24 48 72 96 120 144 168 192 216 240 264 288 312 336 360 384 408 432 m in im u m r a in fa ll ( 0 c ) month civil and environmental science journal vol. iii, no. 01, pp. 001-009, 2020 5 the results of the analysis of the maximum air temperature trendline using the mann-kendall trend test. as the computed p-value is lower than significance alpha level, one should reject the null hypothesis h0, and accept the alternative hypothesis ha. the risk to reject the null hypothesis h0 while it is true is lower than 1,17%. from figure 5, it can be seen that the maximum air temperature has increased by 0,2°c for the last 33 years, from 1985 to 2018. figure 5. maximum air temperature graph from 1985 2018 3. 2. evapotranspiration calculation result the evapotranspiration value is calculated based on data on air temperature, relative humidity, solar, wind speed from climatology station, for 33 years, from 1985 to 2018. by using the modified penmann method it is known that the evapotranspiration value for the last 33 years can be seen in figure 6. the graph below. figure 6. evapotranspiration chart from 1985 – 2018 from the mann-kendall trend test result. as the computed p-value is greater than significance level alpha, one cannot reject the null hypothesis h0. the risk to reject the null hypothesis h0 while it is true 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 0 24 48 72 96 120 144 168 192 216 240 264 288 312 336 360 384 408 432 m a x im u m r a in fa ll ( 0 c ) month 2,5 3 3,5 4 4,5 5 5,5 198519871989199119931995199719992001200320052007200920112013201520172019 a v a ra g e e v a p o tr a n sp ir a ti o n (m m /d a y ) years civil and environmental science journal vol. iii, no. 01, pp. 001-009, 2020 6 is 84.18 %. furthermore, there is no trend in evapotranspiration analysis. the evapotranspiration value has decreased for 33 years, which is equal to 0.15 mm/day. 3. 3. irrigation water requirement calculation result irrigation water needs are calculated based on the planned cropping pattern. in this study the pattern of planting that is used palawija-padi-padi, within one year of planting two crops of rice and one. calculation resulting from the value of irrigation water needs of 1985 to 2018 units per month with a liter/second/ha, multiplied by the total area irrigated by the weir irrigation new market, a score needs water in paddy fields (m3/s). graph value of irrigation water requirement can be seen in figure 7 below. figure 7. irrigation water requirement graph 1985 – 2018 from the graph in figure 7 above it can be seen that the amount of its water demand decreased from 1985 to 2018, this was due to the degradation of agricultural land to settlements, industry and soekarnohatta airport. from 1988 to 2007, degradation of agricultural land of 16.581 ha which causes a decrease in irrigation water demand by 44 m3/s from 1985 to 2018. 3. 4. water availability calculation result calculation of water availability is calculated based on the rainfall data for 33 years at the station budiharto, using the fj mock method to get a debit mainstay of every month. mainstay discharge calculation results can be seen in figure 8 below. figure 8. mainstay discharge from 1985 – 2018 0 5 10 15 20 25 30 35 0 24 48 72 96 120 144 168 192 216 240 264 288 312 336 360 384 408 432 m a in st a y d is ch a rg e ( m 3 /s e co n d ) month civil and environmental science journal vol. iii, no. 01, pp. 001-009, 2020 7 from the graph above it can be seen that there was a decrease in water availability of 1.8 m3 / sec from 1985 to 2018. 3. 5. water balance calculation result the results of the water balance calculation based debit available in cisadane can be seen in figure 9 below. figure 9. water balance from water avaibility cisadane river and water irrigation in1985 – 2018 from the graph of the water balance in the figure 8 above it can be seen that the availability of river water cisadane cannot meet the water needs of irrigation, water irrigation (red line) is greater than availability (blue line) so that the water balance (green line) in deficit each year. the water balance deficit occurred in april 1987 amounted to 162,32 m3 / sec. from the calculation of the water balance in the pasar baru barrage based on data flow available at the weir for 5 years is 2013 to 2017 is known that the availability of water is sufficient irrigation water cisadane from 2013 to 2017 there was a surplus of water balance, the bigest water balance excess occur in march 2014 amounted to 656.97 m3 / second. and the deficit in july 2015 was 0.30 m3 / second. so with the pasar baru barrage there is sufficient water in the cisadane irrigation area. the water balance chart from 2013 to 2017 in pasar baru barrage can be seen in figure 10 and 11 below. figure 10. water balance from water availability bendung pasar baru and water irrigation in 2013 – 2017 civil and environmental science journal vol. iii, no. 01, pp. 001-009, 2020 8 figure 11. water balance from water avaibility pasar baru barrage and water demand tahun 2013 – 2018 per month 4. conclusions the research was conducted to determine the climatological changes, both air temperature and rainfall that occurred in the cisadane watershed. it can be seen that rainfall has fluctuated in the last 33 years, the average temperature has increased by 0.74°c, the maximum has increased by 0.2°c and the minimum has increased by 0.8°c for the last 33 years. although the temperature of the last 33 years has increased, the value of evapotraspiration has decreased by 0.15 mm/day. the value of water requirement for irrigation has decreased this is due to the conversion of irrigation land into settlements, industry and others. although the value of irrigation water requirement is decreasing from year to year but the availability of water in the cisadane river cannot sufficient water requirement, there is always deficit every year, so pasar baru barrage are needed to sufficient water requirement. based on data availability of pasar baru barrage discharge for 5 years from 2013 to 2017, the water balance deficit occurred in july 2015 of 0.3 m3/sec, and the largest surplus occurred in march 2014 of 656.97 m3/ sec. acknowledgements thanks to various parties who have contributed and supported the implementation of this research process, especially to the lppm faculty of engineering, pancasila university for the funds that have been given for this research references [1] ipcc., 2007 intergovernmental panel on climate change, ipcc fourth assessment report : climate change [2] nasa., 2018. world global temperature, article site: https://earthobservatory.nasa.gov/worldofchange/decadaltemp, access on oct 2018. [3] peterson, thomas c., vose, russel s (1997) an overview of the global historical climatology network temperature database, bulletin of the american meteorological society, vol. 78, no. 12. [4] christy, j. r., w. b. norris, and r. t. mcnider.,2009. surface temperature variations in east africa and possible causes, j. clim., 22, 3342–3356, doi:10.1175/2008jcli2726.1. 0,00 100,00 200,00 300,00 400,00 500,00 600,00 700,00 w a te r b a la n ce month 2013 2014 2015 2016 2017 https://earthobservatory.nasa.gov/worldofchange/decadaltemp civil and environmental science journal vol. iii, no. 01, pp. 001-009, 2020 9 [5] noaa., 2018. national centers for environmental information, state of the climate: global climate report for january 2018, published online february 2018, retrieved on october 29, 2018 from https://www.ncdc.noaa.gov/sotc/global/201801. [6] karl, t. r., c. n. williams, p. j. young, and w. m. wendland (1986), model to estimate the time of observation bias associated with monthly mean maximum, minimum and mean temperatures for the united states, j. clim. appl. meteorol., 25, 145–160, doi:10.1175/15200450(1986)025<0145:amtett>2.0.co;2. [7] zabel f (2016) impact of climate change on water availability. in: mauser w., prasch m. (eds) regional assessment of global change impacts. springer, cham pathak, surendra,. et all, climate change and water availability in indian agriculture: impacts and adaptation, indian journal of agricultural sciences, 84(6):671-679 [8] karmeshu, n (2012). trend detection in annual temperature & precipitation using the mann kendall test–a case study to assess climate change on select states in the northeastern united states (tesis). university of pennsylvania, pennsylvania, usa. diperoleh dari http://repository.upenn.edu/cgi/view content. cgi?article=1045&context=mes_capstones [9] ahmad, ijaz, deshan tang, tianfang wang, mei wang, and bakhtawar wagan (2015). “precipitation trends over time using mann-kendall and spearman ’ s rho tests in swat river basin , pakistan.” [10] blain, gabriel constantino., 2013. “acta scientiarum the mann-kendall test : the need to consider the interaction between serial correlation and trend.” (iid):393–402. [11] journal, international (2014). “trend analysis of hydro-meteorological variables using the mann-kendall trend test : aplication to the niger river. 100-110. [12] mondal, arun, sananda kundu, and anirban mukhopadhyay (2012). “rainfall trend analysis by mann-kendall test : a case study of north-eastern part of cuttack district , orissa rainfall trend analysis by mann-kendall test https://www.ncdc.noaa.gov/sotc/global/201801 open access proceedings journal of physics: conference series civil and environmental science journal vol. ii, no. 01, pp. 044-062, 2019 44 study of economic impact of terminals type a and weigh stations management handover in east java province to the central government m. ruslin anwar1, m. hamzah h1, ayu r. d. a1 1 civil engineering department, engineering faculty, universitas brawijaya, malang, 65145, indonesia ruslin@ub.ac.id received 10-01-2019; revised 06-02-2019; accepted 11-03-2019 abstract. purpose of this study is to know the operational performance of terminals type a and weigh stations in east java province, analyse the economic contribution to the regional government, assessing the operational impact terminals type a and weigh, and examine the strategy of minimizing the operational impact if terminals are taken over by the central government. analysis used in this study are growth analysis, efficiency analysis, importanceperformance analysis (ipa) method, and strength weakness opportunity threat method. the operational economic performance of terminals type a (arjosari terminal), obtained retribution of 2,346,495,500 idr and bayuangga terminal obtained retribution of 1,796,877,000 idr. the operational economic performance of weigh stations is 35,668,880,000 idr. the operational economic contribution of terminals type a and weigh stations is very small/less. the operational impact of terminals type a that taken over by the central government for the next 15 years is still considered good. strategy to minimize the operational impact of terminals type a with: 1. strategy s-o (strength-opportunity), 2. strategy s-t (strength-threat), 3. strategy w-o (weak-opportunity), 4. strategy w-t (weak-threat). for weigh stations we cannot do ipa and swot analysis because all samples of weigh bridges are no longer operating when this study is conducted. keywords: terminals type a, weigh stations, ipa, swot. 1. introduction the transportation system in indonesia, approximately around 70 to 80 percent, is on the land and it supposed to be the best, it should not be inferior to airports and train stations. if the province government is deemed not be able to provide information technology, the central government ought to foster and guide them. the ministry of transportation (kemenhub) will begin to take over the management of 120 weigh stations and terminals type a throughout indonesia. previously, since the enactment of regional autonomy, the management of weigh stations and terminals type a was managed by regional transportation agency. the handover of terminals and weigh stations is only in the bookkeeping process, so that the incoming retributions can be directly used for the maintenance and development of those two facilities. in addition, the ministry of transportation will transfer the employee status of mailto:ruslin@ub.ac.id civil and environmental science journal vol. ii, no. 01, pp. 044-062, 2019 45 regional transportation agency who manage terminals type a and weigh stations, for them to be proposed as official government employees at the ministry of transportation. law number 23 of 2014 states terminals type a and weigh stations will be taken into operation by the central government. therefore, discussions must be held to discuss the matter. these discussions included experts from the ministry of transportation (kemenhub) and the ministry of home affairs (kemendagri) who were followed by all heads of transportation departments in east java with bpkad (regional financial and asset management agency) in both east java province and districts/cities in east java. it is expected that law number 23 of 2014 provides opportunities and benefits to the regional government. supervision and guidance are carried out by the central government, but the operation remains in the regional of either province or district/city in east java province. many problems, pros and cons arising from this policy. the objectives of this study are: 1. knowing the economic performance of terminals type a and weigh stations in the study area of east java province. 2. analysing the economic contributions to the regional government if terminals type a and weigh stations are taken over by the central government. 3. assessing operational impacts if terminals type a and weigh stations in east java province are taken over by the central government. 4. assessing strategies for minimizing the operational impact if terminals type a and weigh stations in east java province are taken over by the central government. 2. material and methods methods used for data collection in this study is primary and secondary methods. secondary data collection method is collecting data from related institutions, data from the destination of passengers and goods movement. primary data needed in this study is by taking data directly in the field, using questionnaires. interviews are conducted with the government at the study site. 2.1. the operational economic performance analysis 1. overload analysis in weigh stations overload of goods can be detected through weighing freight loads in the weigh station that is passed. overload analysis in weigh stations includes: • analysis of the freight transport amount in weigh stations. • analysis of cargo freight loads. • analysis of the freight overload percentage. the violation occurrence of goods load can be known if the freight transport vehicle carries a load that is not in accordance with the specified jbi (total permitted weight). under current conditions, the freight loads excess tolerance is set at 25%. 2. analysis of freight loads transportation cost based on two aspects and procedures commonly used in freight load transportation cost, there are: • holding a classification of goods in several groups for the purpose in determining the rating, and • conducting preparations regarding the rate scale and how they are used in a tariff list. the first aspect is about or related to what or what goods that will be transported, meanwhile the second aspect is related to where or where between places the goods are transported and the calculation is based on the first aspect. according to morlok [5] and warpani [9], in the classification of goods that are transported, it is necessary to pay attention to various factors, including type of transported goods, volume or weight, price or value and so forth. therefore, goods that are identical or almost the same in characteristic and type, they will be classified into one group, then they are going to be set by a certain tariff for the group. civil and environmental science journal vol. ii, no. 01, pp. 044-062, 2019 46 2.2. the economic contribution analysis 1. analysis of pad source contribution for the purpose to find out the contribution of each apbd source to the total apbd, the contribution of each pad source to the total pad, the contribution of each regional tax type to the total regional tax. adawiyah [1] describe the contribution of each regional retribution type to the total regional retribution, and bumd respective contribution to the total portion of bumd profits, the following formulation is used: 𝑃𝑛 = 𝑄𝑋 𝑥 100 𝑄𝑌 with, pn = contribution of pad component revenue to the apbd (rupiah) qy = amount of apbd revenue (rupiah) qx = amount of pad revenue component (rupiah) n = a certain year (period) 2.3. the operational impact analysis 1. analysis of ipa (importance-performance analysis) jonathan [7] describe that ipa has the main function to display information related to service factors that according to consumers greatly influence their satisfaction and loyalty, and service factors that according to consumers need to be improved because current conditions are not satisfactory. bakhtiar [2] and saputra [4] used ipa method for the terminals performance analysis. ipa combines the measurement of importance level and satisfaction level factors into two-dimensional graph that facilitates explanation of data and practical proposal acquirements. in this study, there are two variables used, x to indicate the satisfaction performance level and y to indicate the importance level indicators. using the formula: 𝑇𝑘𝑖 = 𝑋𝑖 𝑌𝑖 𝑥 100% with, tki = respondent suitability level. xi = performance assessment score. yi = importance assessment score. 2. analysis of swot (strength weakness opportunity threat) the swot analysis is needed in this study used to help finding out potential areas at the study site. rangkuti [3] present an internal and external factors are carried out in this swot analysis. internal analysis is intended to identify strengths and weaknesses, while external analysis is intended to know opportunities and threats. method used to construct strategic factors of terminal effectiveness is using the swot matrix. this matrix can be clearly illustrated how external opportunities and threats can be adjusted to the internal strengths and weaknesses they have. the purpose of swot analysis is providing an overall image of analysis results of strength, weakness, opportunity and threat that used as a basis for objectivity and strategies making in terminal development. the analysis of swot consists of four factors, there are: 1. strength it is a strength condition contained in terminals. the strength analysed is a factor found in the terminal itself. civil and environmental science journal vol. ii, no. 01, pp. 044-062, 2019 47 2. weakness it is a weakness condition contained in terminals. the weakness analyzed is a factor found in the terminal itself. 3. opportunity it is an opportunity condition to develop in the future that occurs. conditions that occur are opportunities from outside the terminal. for example, accessibility, government policies, environmental conditions. 4. threat it is a threatening condition from the outside. the threats can interfere with the concept of terminals planning and development. 3. result and discussion 3.1. the operational economic performance of terminals type a and weigh stations 3.1.1 the operational economic performance of terminals type a 1. arjosari terminal there are several criteria used to find out the economic performance of arjosari terminal, as follows: 1) terminal service based on the calculation result, the annual income from terminal service is 1,241,632,500 idr. 2) passengers boarding and unboarding parking service based on the calculation result, the income from passengers boarding and unboarding parking service every year is 373,629,000 idr. 3) waiting for departure parking service based on the calculation result, the income from parking service while waiting for departure every year is 268,274,000 idr. 4) parking service other than public transportation based on the calculation result, the income from the motorized vehicles parking service every month is 462,960,000 idr. 2. bayuangga terminal there are several criteria used to find out the economic performance of bayuangga terminal, as follows: 1) terminal service based on the calculation result, annual income from terminal service is 1,019,859,000 idr. 2) passengers boarding and unboarding parking service based on the calculation result, the income from passengers boarding and unboarding parking service every year is 464,454,000 idr. 3) waiting for departure parking service based on the calculation result, the income from parking service while waiting for departure every year is 290,604,000 idr. 4) parking service other than public transportation based on the calculation result, the income from the motorized vehicles parking service every month is 21,960,000 idr. 3.1.2 the operational economic performance of weigh stations 1. rejoso weigh station there are two criteria to determine the economic performance of the weigh station, there are: 1) costs of unloading and/or storing of over loads. in the activities of unloading, storing or stacking goods and re-loading the loads using warehouse and land owned by the province regional government are subject to retribution in the use of regional asset with provision of: civil and environmental science journal vol. ii, no. 01, pp. 044-062, 2019 48 a) the use of warehouses and land for storing goods that are unloaded for less than 1(one) day is calculated as 1 (one) day. b) the use of warehouses and land for storing goods shall be carried out no later than 15 (fifteen) days from the date of storage. c) if the period expires and the goods stored are not taken, they belong to the province regional government. 2) fines value for violations of loading, carrying capacity and dimensions. based on the analysis result, the amount of fines value of rejoso weigh station in east java is explained in table 1 below. table 1. fines value for violations in rejoso weigh station 2016 no weigh station vehicle groups number of violations amount of fines total 1 rejoso group i 129,073 20,000 2,581,460,000 group ii 12,021 40,000 480,840,000 group iii 23,627 50,000 1,181,350,000 group iv 16,622 60,000 997,320,000 total 4,808,214,000 2. sedarum weigh station there are two criteria to determine the economic performance of the weigh station, there are: 1) costs of unloading and/or storing of over loads. in the activities of unloading, storing or stacking goods and re-loading the loads using warehouse and land owned by the province regional government are subject to retribution in the use of regional asset with provision of: a) the use of warehouses and land for storing goods that are unloaded for less than 1(one) day is calculated as 1 (one) day. b) the use of warehouses and land for storing goods shall be carried out no later than 15 (fifteen) days from the date of storage. c) if the period expires and the goods stored are not taken, they belong to the province regional government. 2) fines value for violations of loading, carrying capacity and dimensions. based on the analysis results, the amount of fines value of sedarum weigh station in east java is explained in table 2 below. tabel 2. fines value for violations in sedarum weigh station 2016 no weigh station vehicle groups number of violations amount of fines total 1 sedarum group i 101,225 20,000 2,024,500,000 group ii 22,809 40,000 912,360,000 group iii 64,899 50,000 3,244,950,000 group iv 23,174 60,000 1,390,440,000 total 7,572,250,000 3. widang weigh station there are two criteria to determine the economic performance of the weigh station, there are: 1) costs of unloading and/or storing of over loads. in the activities of unloading, storing or stacking goods and re-loading the loads using warehouse and land owned by the province regional government are subject to retribution in the use of regional asset with provision of: a) the use of warehouses and land for storing goods that are unloaded for less than 1(one) day is calculated as 1 (one) day. civil and environmental science journal vol. ii, no. 01, pp. 044-062, 2019 49 b) the use of warehouses and land for storing goods shall be carried out no later than 15 (fifteen) days from the date of storage. c) if the period expires and the goods stored are not taken, they belong to the province regional government. 2) fines value for violations of loading, carrying capacity and dimensions. based on the analysis results, the amount of fines value of widang weigh station in east java is explained in table 3 below. tabel 3. fines value for violations in widang weigh station 2016 no weigh station vehicle groups number of violations amount of fines total 1 widang group i 3,431 20,000 68,620,000 group ii 918 40,000 36,720,000 group iii 3,064 50,000 153,200,000 group iv 3,639 60,000 218,340,000 total 476,880,000 4. weigh stations in east java there are two criteria to determine the economic performance of weigh stations, there are: 1) costs of unloading and/or storing of over loads. in the activities of unloading, storing or stacking goods and re-loading the loads using warehouse and land owned by the province regional government are subject to retribution in the use of regional asset with provision of: a) the use of warehouses and land for storing goods that are unloaded for less than 1(one) day is calculated as 1 (one) day. b) the use of warehouses and land for storing goods shall be carried out no later than 15 (fifteen) days from the date of storage. c) if the period expires and the goods stored are not taken, they belong to the province regional government. 2) fines value for violations of loading, carrying capacity and dimensions. based on the analysis results, the amount of fines value of weigh stations in east java is explained in table 4 below. tabel 4. fines value for violations in weigh stations 2016 no weigh station vehicle groups number of violations amount of fines total 1 east java group i 692,323 20,000 13,846,460,000 group ii 86,331 40,000 3,453,240,000 group iii 218,376 50,000 10,918,800,000 group iv 124,173 60,000 7,450,380,000 total 35,668,880,000 3.2. the operational economic contribution of terminals type a and weigh stations criteria used to measure the operational performance of terminals type a and weigh stations (palealu, a.s. and others, 2016) are: • growth of retribution revenue • efficiency of retribution revenue 3.2.1 terminals type a 1. arjosari terminal 1) growth analysis: measuring how much revenue is realized compared to the previous year. civil and environmental science journal vol. ii, no. 01, pp. 044-062, 2019 50 𝐺 = (2,346,495,500 − 2,182,088,000) 2,182,088,000 𝑥 100 % = 7.53% therefore, the growth analysis for arjosari terminal is equal to 7.53%. 2) efficiency analysis: comparing costs used to achieve certain goals with results that have been obtained. 𝐸 = 1,795,200,000 2,346,495,500 𝑥 100 % = 76.5% therefore, the efficiency analysis for arjosari terminal is equal to 76.5%. 3) economic contribution comparing the revenues realization with gdrp from transportation sector. 𝐾 = 2,346,495,500 1,122,300,000,000 𝑥 100 % = 0.2% therefore, the economic contribution of arjosari terminal to the gdrp in malang city is 0.2 %. 2. bayuangga terminal 1) growth analysis: measuring how much revenue is realized compared to the previous year. 𝐺 = (1,796,877,000 − 1,809,870,000) 1,809,870,000 𝑥 100 % = −0.71% therefore, the growth analysis for bayuangga terminal is equal to -0.71%. 2) efficiency analysis: comparing costs used to achieve certain goals with results that have been obtained. 𝐸 = 2,199,948,000 1,796,877,000 𝑥 100 % = 122.43% therefore, the efficiency analysis for bayuangga terminal is equal to 122.43 %. 3) economic contribution comparing the revenues realization with gdrp from transportation sector. 𝐾 = 1,796,877,000 1,169,753,160,000 𝑥 100 % = 0.15% therefore, the economic contribution of bayuangga terminal to the gdrp in probolinggo city is 0.15 %. 3.2.2 weigh stations 1. rejoso weigh station 1) growth analysis: measuring how much revenue is realized compared to the previous year. 𝐺 = (4,808,214,000 − 7,006,840,000) 7,006,840,000 𝑥 100 % = −31.38% therefore, the growth analysis for rejoso weigh station is equal to – 31.38%. 2) economic contribution comparing the revenues realization with gdrp from transportation sector. 𝐾 = 4,808,214,000 543,236,300,000 𝑥 100 % = 0.89% therefore, the economic contribution of rejoso weigh station to the gdrp in pasuruan district is 0.89 %. civil and environmental science journal vol. ii, no. 01, pp. 044-062, 2019 51 2. sedarum weigh station 1) growth analysis: measuring how much revenue is realized compared to the previous year. 𝐺 = (1,390,440,000 − 6,828,580,000) 6,828,580,000 𝑥 100 % = −79.64% therefore, the growth analysis for sedarum weigh station is equal to -79.64%. 2) economic contribution comparing the revenues realization with gdrp from transportation sector. 𝐾 = 1,390,440,000 543,236,300,000 𝑥 100 % = 0.26% therefore, the economic contribution of sedarum weigh station to the gdrp in pasuruan district is 0.26 %. 3. widang weigh station 1) growth analysis: measuring how much revenue is realized compared to the previous year. 𝐺 = (476,880,000 − 6,847,870,000) 6,847,870,000 𝑥 100 % = −93.04% therefore, the growth analysis for widang weigh station is equal to – 93.04%. 2) economic contribution comparing the revenues realization with gdrp from transportation sector. 𝐾 = 476,880,000 350,633,060,000 𝑥 100 % = 0.14% therefore, the economic contribution of widang weigh station to the gdrp in tuban city is 0.14 %. 4. weigh stations in east java 1) growth analysis: measuring how much revenue is realized compared to the previous year. 𝐺 = (35,668,880,000 − 58,895,210,000) 58,895,210,000 𝑥 100 % = −39.44% therefore, the growth analysis for weigh stations is equal to – 39.44%. 2) economic contribution comparing the revenues realization with gdrp from transportation sector. 𝐾 = 35,668,880,000 41,107,640,000,000 𝑥 100 % = 0.08% therefore, the economic contribution of weigh stations in east java to the gdrp in east java is 0.08 %. 3.3. the operational impact of terminals type a and weigh stations management handover to the central government 3.3.1. analysis of terminal type a and weigh station facilities the main and supporting facilities of terminal type a based on decree of the minister of transportation number 132 of 2015 concerning the implementation of passenger road transport terminals are shown in table 5 below: civil and environmental science journal vol. ii, no. 01, pp. 044-062, 2019 52 table 5. conditions of terminal main facilities with type a standards no main facilities requirement terminal type a standards facilities condition in arjosari terminal facilities condition in bayuangga terminal 1 vehicles lane of departure √ √ 2 vehicles lane of arrival √ √ 3 passengers waiting room √ √ 4 vehicles parking lot √ √ 5 environmental management facilities √ √ 6 road equipment √ √ 7 technology use facilities √ √ 8 media information √ √ 9 drivers handling √ 10 customer service from bus companies √ √ 11 safety surveillance facilities √ √ 12 passengers lane of arrival √ √ 13 departure waiting room √ √ 14 ticket counters √ 15 shared ticket counters √ 16 online ticket counters √ 17 information centre √ √ 18 browser board in the terminal √ √ 19 bulletin board √ √ 20 baggage service √ 21 storage room √ √ 22 emergency meeting points √ 23 disaster evacuation routes √ table 6. conditions of terminal supporting facilities with type a standards no supporting facilities requirement terminal type a standards facilities condition in arjosari terminal facilities condition in bayuangga terminal 1 disabled and pregnant women facilities √ √ 2 security facilities √ √ 3 security service facilities √ √ 4 vehicles crew rest facilities √ 5 ramp check facilities √ √ 6 vehicles deposition facilities √ √ 7 workshop facilities for bus operations √ 8 health facilities √ √ 9 worship/praying facilities √ √ 10 passengers transit area √ √ 11 fire extinguishers √ √ 12 public facilities √ √ 3.3.2. analysis of terminal type a queue 1. arjosari terminal frequency of arrivals is the number of vehicles entering the terminal unit of a certain time. it is expressed by the value of arrival rate (λ). frequency of arrivals in arjosari terminal is shown in table 7 below: civil and environmental science journal vol. ii, no. 01, pp. 044-062, 2019 53 table 7. frequency of bus arrivals no month vehicles λ 1 january 10,442 19 2 february 10,940 22 3 march 10,465 19 4 april 10,555 20 5 may 10,350 19 6 june 10,902 20 7 july 12,015 22 8 august 11,162 20 9 september 11,143 21 10 october 11,237 20 11 november 11,790 22 12 december 13,136 24 total 134,137 248 average 21 frequency of service is the number of vehicles that depart from the terminal after getting service per unit of time. frequency of service in arjosari terminal is shown in table 8 below: table 8. frequency of bus departures no month vehicles μ 1 january 9,408 19 2 february 9,900 22 3 march 9,593 19 4 april 10,107 20 5 may 9,796 19 6 june 10,228 20 7 july 10,723 22 8 august 10,557 20 9 september 10,438 21 10 october 10,511 20 11 november 11,217 22 12 december 12,065 24 total 124,543 229 average 19 grdp (gross regional domestic product) is used to predict the condition of passenger’s amount in the next 15 years. the prediction of passengers amounts to arrive in the next 15 years is shown in table 9 below. table 9. prediction of the passengers increasing amount in the next 15 years year passengers year passengers departure arrival departure arrival 2017 2,622,328 2,864,558 2025 4,055,070 4,429,646 2018 2,769,178 3,024,974 2026 4,282,154 4,677,706 2019 2,924,252 3,194,372 2027 4,521,954 4,939,658 2020 3,088,010 3,373,257 2028 4,775,184 5,216,279 2021 3,260,939 3,562,159 2029 5,042,594 5,508,390 2022 3,443,551 3,761,640 2030 5,324,979 5,816,860 2023 3,636,390 3,972,292 2031 5,623,178 6,142,604 2024 3,840,028 4,194,741 2032 5,938,076 6,486,590 civil and environmental science journal vol. ii, no. 01, pp. 044-062, 2019 54 based on analysis of the queue on routes that exist in arjosari terminal for the next 15 years, the analysis results for the value of traffic intensity (ρ) can be seen in table 10. table 10. prediction of terminal performance in the next 15 years year frequency of arrival (λ) frequency of departure (μ) traffic intensity (ρ) year frequency of arrival (λ) frequency of departure (μ) traffic intensity (ρ) 2017 22 20 1.1 2025 32 27 1.2 2018 23 20 1.1 2026 34 28 1.2 2019 24 21 1.1 2027 35 29 1.2 2020 25 22 1.1 2028 37 30 1.2 2021 27 23 1.2 2029 39 31 1.2 2022 28 24 1.2 2030 41 32 1.3 2023 29 25 1.2 2031 43 33 1.3 2024 31 26 1.2 2032 45 35 1.3 based on analysis that has been done, the terminal performance for the next 15 years has a value of traffic intensity (ρ) = 1.3. and based on the value of traffic intensity (ρ) that has been analyzed, the terminal performance is good because the value of traffic intensity (ρ) is more than 1. 2. bayuangga terminal frequency of arrivals is the number of vehicles entering the terminal unit of a certain time. it is expressed by the value of arrival rate (λ) (table 11). table 11. frequency of bus arrivals no year vehicles λ 1 2016 145302 22 frequency of service (µ) is the number of vehicles that depart from the terminal after getting service per unit of time (table 12). table 12. frequency of bus departures no year vehicles μ 1 2016 154818 24 grdp (gross regional domestic product) is used to predict the condition of passenger’s amount in the next 15 years. the prediction of passengers amounts to arrive in the next 15 years is shown in table 13 below. table 13. prediction of the passengers increasing amount in the next 15 years year passengers year passengers departure arrival departure arrival 2017 2,159,653 1,629,137 2025 3,411,108 2,573,174 2018 2,286,641 1,724,931 2026 3,611,682 2,724,477 2019 2,421,096 1,826,357 2027 3,824,048 2,884,676 2020 2,563,456 1,933,746 2028 4,048,903 3,054,295 2021 2,714,187 2,047,451 2029 4,286,978 3,233,888 2022 2,873,781 2,167,841 2030 4,539,052 3,424,040 2023 3,042,760 2,295,310 2031 4,805,949 3,625,374 2024 3,221,674 2,430,274 2032 5,088,538 3,838,546 civil and environmental science journal vol. ii, no. 01, pp. 044-062, 2019 55 based on analysis of the queue on routes that exist in bayuangga terminal for the next 15 years, the analysis results for the value of traffic intensity (ρ) can be seen in table 14. table 14. prediction of terminal performance in the next 15 years year frequency of arrival (λ) frequency of departure (μ) traffic intensity (ρ) 2017 23 25 0.9 2018 24 26 0.9 2019 25 27 0.9 2020 27 28 0.9 2021 28 29 0.9 2022 29 30 1.0 2023 31 31 1.0 2024 32 32 1.0 2025 34 34 1.0 2026 35 35 1.0 2027 37 36 1.0 2028 39 38 1.0 2029 41 39 1.0 2030 43 41 1.0 2031 45 42 1.0 2032 47 44 1.1 based on analysis that has been done, the terminal performance for the next 15 years has a value of traffic intensity (ρ) = 1.1. and based on the value of traffic intensity (ρ) that has been analysed, the terminal performance is good because the value of traffic intensity (ρ) is more than 1. 3.4. minimization strategies of the operational impact on terminals type a and weigh stations management handover to the central government importance-performance analysis (ipa) and swot (strength-weakness-opportunity-threat) methods are used to develop strategies to minimize the operational impact of terminals type a and weigh stations after being taken over by the central government. the amount of terminal type a users (respondents) used in this analysis is approximately 47 people consisting of 15 passengers and 20 transport drivers and 12 stakeholders. whereas for service quality attributes that will be sought satisfaction level is in the amount of 29 attributes spread over 4 subcategories, they are facilities, accessibility, services and security. meanwhile, respondents for weigh station user after being taken over by the central government were not obtained, considering that all weigh station samples were no longer operating when the study was conducted. the next discussion is focused on minimizing the operational impact of terminals type a. 1. arjosari terminal analysis of satisfaction and importance levels of users is used to measure the suitability level of users satisfaction and importance from the comparison result between performance score and importance score. this suitability level will determine the priority order for increasing factors that affect user satisfaction. this priority is included in the cartesian diagram. the importance value (4.11) is bigger than satisfaction value (3.70), therefore 𝑋 𝑌 = 3.70 4.11 = 0.90 𝑜𝑟 𝑋 𝑌 < 1. it can be concluded that user satisfaction level in arjosari terminal service is still not satisfactory or arjosari terminal service is considered not optimal. the suitability level variables to describe the comparison between conditions that are currently felt and conditions that desired by arjosari terminal users, is shown in table 15 below: civil and environmental science journal vol. ii, no. 01, pp. 044-062, 2019 56 table 15. suitability level for each variable in arjosari terminal no code indicators average 1 y1 facilities 0.90 y1.1 vehicles lane of departure 0.89 y1.2 vehicles lane of arrival 0.90 y1.3 passengers waiting room, 0.90 y1.4 vehicles parking lot 0.90 y1.5 environmental management facilities 0.94 y1.6 road equipment 0.92 y1.7 technology use facilities 0.93 y1.8 media information 0.94 y1.9 drivers handling 0.94 y1.10 customer service from bus companies 0.94 y1.11 safety surveillance facilities 0.89 y1.12 passengers lane of arrival 0.92 y1.13 departure waiting room 0.87 y1.14 ticket counters 0.92 y1.15 information centre 0.93 y1.16 browser board in terminal 0.91 y1.17 bulletin board 0.93 y1.18 baggage service 0.91 y1.19 storage room 0.91 y1.20 emergency meeting points 0.83 y1.21 disaster evacuation routes 0.84 y1.22 toilets 0.76 y1.23 retails and cafeteria 0.82 y1.24 praying facilities (musholla) 0.86 2 y2 accessibility 0.89 y2.1 located on a road network with activities centre 0.88 y2.2 strategic location 0.89 y2.3 easily accessed by passengers and public transportation 0.89 3 y3 service 0.90 y3.1 customer service 0.90 4 y4 security 0.92 y4.1 passengers and goods safety 0.92 based on table 15, it shows there is no variable that has a satisfaction level equal to or more than 1, which means the satisfaction level of service in arjosari terminal is still not optimal. however, it can be seen from the table that security suitability variable has the highest score of 0.92. it means respondents are quite satisfied with security service of terminal type a since the score is close to the value of 1. the calculated data is then entered into cartesian diagram (shown in figure 2) to determine the priority of each variable to improve arjosari terminal service. civil and environmental science journal vol. ii, no. 01, pp. 044-062, 2019 57 figure 2. variables of arjosari terminal service in cartesian diagram the swot matrix (strength-weakness-opportunity-threat) is used to formulate minimization strategies for the operational impact of the terminal, based on internal and external strategy factors. these factors are obtained from the results of previous ipa analysis based on the result of interviews/field observations obtained, as follows: a) strength ipa analysis results in quadrant b with high levels of performance/satisfaction and importance, are the strength on internal factors, they are: ▪ located on a road network with activities centre ▪ strategic location ▪ easily accessed by passengers and public transportation ▪ passengers and goods safety b) weakness indicators in quadrant a as a result of ipa analysis with high importance level, but low in performance/satisfaction level. it becomes a weakness on internal factors, they are: ▪ praying facilities (musholla) ▪ customer service c) opportunity opportunity factors as external factors are based on interviews/field observations result, among others: ▪ high interest in service that has the potential to increase the amount of public transportation; ▪ government policies to provide business opportunities in the field of providing public transport service. d) threat threat factors as negative external factors are based on interviews/field observations result, as follows: ▪ increasing number of online transportation systems; ▪ increasing access to private vehicles ownership used as public transportation. 2. bayuangga terminal analysis of satisfaction and importance levels of users is used to measure the suitability level of users satisfaction and importance from the comparison result between performance score and importance score. this suitability level will determine the priority order for increasing factors that affect user satisfaction. this priority is included in the cartesian diagram. the importance value (3.67) is bigger than satisfaction value (4.34), therefore, 𝑋 𝑌 = 4.34 3.67 = 0.85 𝑜𝑟 𝑋 𝑌 < 1. it can be concluded that user 1 3&2 4 5 6 7 8 9 10 11 12 13 14 1516 17 18 19 20 21 22 23 24 25 26 27 28 29 r 2.0 2.5 3.0 3.5 4.0 4.5 5.0 2.0 2.5 3.0 3.5 4.0 4.5 5.0 t in g k a t k e p e n ti n g a n ( y ) tingkat kepuasan (x) importance performance analysis prioritas utama (a) prioritas rendah (d) pertahankan prestasi (b) berlebihan (c) civil and environmental science journal vol. ii, no. 01, pp. 044-062, 2019 58 satisfaction level in bayuangga terminal service is still not satisfactory or bayuangga terminal service is considered not optimal. the suitability level variables to describe the comparison between conditions that are currently felt and conditions that desired by terminal type a users, is shown in table 16 below: table 16. suitability level for each variable in bayuangga terminal no. code indicators average 1 y1 facilities 0.92 y1.1 vehicles lane of departure 0.92 y1.2 vehicles lane of arrival 0.92 y1.3 passengers waiting room, 0.92 y1.4 vehicles parking lot 0.96 y1.5 environmental management facilities 1.00 y1.6 road equipment 1.00 y1.7 technology use facilities 1.00 y1.8 media information 1.00 y1.9 drivers handling 1.00 y1.10 customer service from bus companies 0.95 y1.11 safety surveillance facilities 0.95 y1.12 passengers lane of arrival 1.05 y1.13 departure waiting room 1.00 y1.14 ticket counters 1.00 y1.15 information centre 0.96 y1.16 browser board in terminal 0.92 y1.17 bulletin board 0.91 y1.18 baggage service 0.87 y1.19 storage room 0.96 y1.20 emergency meeting points 0.70 y1.21 disaster evacuation routes 0.73 y1.22 toilets 0.79 y1.23 retails and cafeteria 0.73 y1.24 praying facilities (musholla) 0.72 2 y2 accessibility 0.87 y2.1 located on a road network with activities centre 0.81 y2.2 strategic location 0.92 y2.3 easily accessed by passengers and public transportation 0.88 3 y3 service 0.86 y3.1 customer service 0.86 4 y4 security 0.76 y4.1 passengers and goods safety 0.76 based on table 16, it shows there is no variable that has a satisfaction level equal to or more than 1, which means the satisfaction level of service in bayuangga terminal is still not optimal. however, it can be seen from the table that facilities variable has the highest score of 0.92. it means respondents are quite satisfied with facilities service in bayuangga terminal, since the score is close to the value of 1. the calculated data used to determine the priority of each variable to improve bayuangga terminal service, then entered into cartesian diagram shown in figure 3 below. civil and environmental science journal vol. ii, no. 01, pp. 044-062, 2019 59 figure 3. variables of bayuangga terminal service in cartesian diagram the swot matrix (strength-weakness-opportunity-threat) is used to formulate minimization strategies for the operational impact of the terminal, based on internal and external strategy factors. these factors are obtained from the result of previous ipa analysis that based on interviews/field observations result obtained, as follows: a) strength ipa analysis results in quadrant b with high levels of performance/satisfaction and importance are the strength in internal factors, they are: ▪ toilets ▪ customer service ▪ passengers and goods safety ▪ weakness indicators in quadrant a as a result of ipa analysis with high importance level, but low in performance/satisfaction level. it becomes a weakness on internal factors, they are: ▪ praying facilities (musholla) b) opportunity opportunity factors as external factors are based on interviews/field observations result, among others: ▪ high interest in service that has the potential to increase the amount of public transportation; ▪ government policies to provide business opportunities in the field of providing public transport service. c) threat threat factors as negative external factors are based on interviews/field observations result, as follows: ▪ increasing number of online transportation systems; ▪ increasing access to private vehicles ownership used as public transportation. 4. conclusions based on the analysis results in previous chapter in this study, it can be concluded that: 1. the operational economic performance of terminals type a and weigh stations a) the operational economic performance of terminals type a: ▪ arjosari terminal that serves a total of 258,680 vehicles and 5,195,915 passengers for 2016, obtained retribution of 2,346,495,500 idr. ▪ bayuangga terminal that serves a total of 300,120 vehicles and 3,578,382 passengers for 2016, obtained retribution of 1,796,877,000 idr b) the operational economic performance of weigh stations in east java shows vehicle violations in total of 1,121,203 vehicles for 2016 and obtained retribution of 35,668,880,000 idr. detail explanation on 3 weigh stations in this study, as follows: 13&2 4 5 67 8 9 1011 12 1314 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 r 2,0 2,5 3,0 3,5 4,0 4,5 5,0 2,0 2,5 3,0 3,5 4,0 4,5 5,0 t in g k a t k e p e n ti n g a n ( y ) tingkat kepuasan (x) importance performance analysis prioritas utama (a) prioritas rendah (d) pertahankan prestasi (b) berlebihan (c) civil and environmental science journal vol. ii, no. 01, pp. 044-062, 2019 60 ▪ rejoso weigh station, violations amount is 181,343 vehicles and obtained retribution of 4,808,214,000 idr. ▪ sedarum weigh station, violations amount is 212,107 vehicles and obtained retribution of 7,572,250,000 idr. ▪ widang weigh station, violations amount is 11,052 vehicles and obtained retribution of 476,880,000 idr. 2. the operational economic contribution of terminals type a and weigh stations a) the operational economic contribution of terminals type a: ▪ arjosari terminal is classified as a very/less small with a retribution-revenue growth of 7.53% is 0.2%, ▪ bayuangga terminal is classified as very/less small with a retribution-revenue growth of 1.22% is 0.15%. b) the operational economic contribution of weigh stations in east java with the retributionrevenue growth of -39.437% is 0.08%. detail explanation on 3 weigh stations in this study, as follows: ▪ rejoso weigh station with a revenue growth of -31.38% is 0.89%. ▪ sedarum weigh station with a revenue growth of -79.64% is 0.26%. ▪ widang weigh station with a revenue growth of -93.04% is 0.14%. 3. the operational impact of terminals type a management handover to the central government. ▪ arjosari terminal is still considered good of being taken over by the central government for the next 15 years, there are changes in arrival frequency by 45 buses/hour, service frequency by 35 buses/hour and traffic intensity of 1.3. ▪ bayuangga terminal is still considered good for the next 15 years, there are changes in arrival frequency by 47 buses/hour, service frequency by 44 buses/hour and traffic intensity of 1.1. 4. strategies to minimize the operational impact of terminals type a and weigh stations a) arjosari terminal 1) the satisfaction level of service in arjosari terminal is still not optimal with the comparison value on the satisfaction level to the importance level 𝑋 𝑌 = 3.70 4.11 = 0.90. 2) the availability level of main and supporting facilities in arjosari terminal is relatively sufficient. 3) the sustainability level of security variable for arjosari terminal users has the highest score of 0.92. this means the respondents are quite satisfied with service in arjosari terminal, while the accessibility variable has the lowest score of 0.89. this means it should have improvements in terminal accessibility. 4) ipa analysis results obtained by these indicators must be given the highest priority for the performance improvement, they are: 1. being on a road network with activities centre; 2. strategic location; 3. easily accessed by passengers and public transportations; and 4. passengers and goods safety. b) bayuangga terminal: 1) the satisfaction level of service in bayuangga terminal is still not optimal with the comparison value on the satisfaction level to the importance level 𝑋 𝑌 = 4.34 3.67 = 0.85. 2) the availability level of main and supporting facilities in bayungga terminal is sufficient. 3) the sustainability level of facilities variable for bayuangga terminal users has the highest score of 0.92. this means the respondents are quite satisfied with facilities in bayuangga terminal, while the security variable has the lowest score of 0.76. this means it should have improvements in terminal security 4) ipa analysis result obtained by these indicators that must be given the highest priority to be improved is praying facilities (musholla). meanwhile, indicators with conditions have civil and environmental science journal vol. ii, no. 01, pp. 044-062, 2019 61 met expectations and need to be maintained are: 1. toilets; 2. customer service; and 3. passengers and goods safety. c) strategies to minimize the operational impact of terminals type a and weight stations management handover to the central government using s-o strategy (strength-opportunity), which includes: 1) improved road maintenance. 2) providing special lanes for public transportation. 3) providing bus stop facilities at each sufficient distance (500 meters). 4) controlling the area around terminals and weigh stations location for development purposes. 5) development of integrated terminals (interchange) for the convenience and security of passengers and goods. d) strategies to minimize the operational impact of terminals type a and weight stations management handover to the central government using s-t strategy (strength-threat), which includes: 1) providing a special base for online transportation. 2) limiting the acceleration of private vehicles ownership by implementing high tax on vehicle ownership and high parking fees. 3) providing mass public transportation. e) strategies to minimize the operational impact of terminals type a and weight stations management handover to central government using w-o strategy (weakness-opportunity), which includes: 1) completing and maintaining an adequate place for praying/worship (musholla). 2) human resources recruitment that meet standards of terminals and weigh stations operation. 3) utilizing outsourcing human resources to meet the needs of terminal and weigh station employees. 4) utilizing cleaning service employees to maintain praying facilities. 5) preparing sop for terminals and weigh stations operation. f) strategies to minimize the operational impact of terminals type a and weight stations management handover to the central government using w-t strategy (weakness-threat), which includes: 1) completing regional regulations concerning conventional public transportation system and online public transportation system. 2) customer service application using digital/online information system. g) ipa analysis and swot cannot be carried out on weigh stations since the respondents were not obtained after weigh stations management was taken over by the central government, considering that all weigh station samples were no longer operating when the study was conducted recommendations swot analysis results based on internal and external factors obtain 4 (four) strategies to minimize the operational impact of terminals type a that taken over by the central government, among others: 1. s-o strategy (strength-opportunity) for increasing road maintenance is prioritized on available accessed roads. providing special road lanes for public transportation needs to be carried out on sufficient road sections. providing bus stop facilities at each sufficient distance (500 meters) needs to be accompanied by the making of regional regulations for the implementation. controlling the area around terminals location needs to be included in district/city spatial planning. development of integrated terminals (interchange) needs to be synchronized with airport and station planning. 2. s-t strategy (strength-threat) is used to avoid threat factors with strength factors, which is providing a special base for online transportation needs to be included in district/city spatial civil and environmental science journal vol. ii, no. 01, pp. 044-062, 2019 62 planning. limiting the acceleration of private vehicles ownership needs to implement vehicle tax regulation. providing mass public transportation needs to be synchronized with the transportation system planning. 3. based on the improvement results obtained by the existence of internal factors strength that can provide directions for improvement, then w-o strategy (weakness-opportunity) is recommended. completing and maintaining praying facilities (musholla) needs to pay attention to minimum standards of space requirement and number of users. recruitment of human resources and cleaning service employees need to pay attention to local government needs and capabilities. utilizing outsourcing human resources needs to pay attention to availability of existing human resources. 4. then, for w-t strategy (weakness-threat), which is complementing regional regulations on conventional public transportation and online public transportation systems, it is necessary to pay attention to the vehicles amount proportion. customer service application using digital/online information system needs to be made in a website form. acknowledgements collate acknowledgements in a separate section at the end of the article before the references and do not, therefore, include them on the title page, as a footnote to the title or otherwise. list here those individuals who provided help during the research (e.g., providing language help, writing assistance or proof reading the article, etc.). references [1] adawiyah, w, i. c. kusuma. (2015). analisis kontribusi dan efektivitas sumber-sumber pendapatan asli daerah dan dana perimbangan terhadap anggaran pendapatan dan belanja daerah (apbd) pemerintah daerah kota sukabumi.jurnal akunida (1) : 17-25 [2] bakhtiar, anang. 2014. kajian efektifitas operasional terminal madyopura malang. tesis: fakultas teknik. universitas brawijaya malang [3] freddy rangkuti. 2005. analisis swot. teknik membedah kasus bisnis, gramedia jakarta. [4] m. taufiq yuda saputra. 2012. analisa tingkat kepuasan pengguna jasa terhadap kinerja pelayanan terminal makassar metro kota makassar, tesis : fakultas teknik. institut teknologi 10 nopember surabaya. [5] morlok, e.k. 1998. pengantar teknik dan perencanaan transportasi. erlangga jakarta. [6] pearce, j.a.,ii and robinson, r.b., jr. 2003. strategic management: strategy formulation, implementation and control, 8th edition, chicago, il : r.d. irwin,inc. [7] sarwono, jonathan. 2006. metodologi penelitian kuantitatif dan kualitatif. graha ilmu yogyakarta. [8] supranto, j. 2006. pengukuran tingkat kepuasan pelanggan. pt. rineka cipta, jakarta. [9] warpani suwajoko. 1990. merencanakan sistem pengangkutan. penerbit itb. bandung open access proceedings journal of physics: conference series civil and environmental science journal vol. 05, no. 02, pp. 144-158, 2022 144 factors affecting commuters' intentions in using park and ride (p&r) facilities based on theory of planned behavior sara irawati1, imma widyawati agustin1, ismu rini dwi ari1 1 urban and regional department, universitas brawijaya, malang, 65145, indonesia saraairwt@gmail.com received 21-06-2022; accepted 27-09-2022 abstract. park and ride (p&r) is a form of transportation demand management closely related to commuting activities. several developed countries, such as the uk, canada, china, and hong kong, have already implemented p&r with a high level of effectiveness and success in overcoming the congestion problems in the city center, low use of public transportation, and air pollution. however, in developing countries, the various positive impacts of p&r still have not been able to encourage commuters' intentions to use these facilities. as a result, the level of p&r use at sidoarjo station is still relatively low (44.3%). behavioral is one of several keys to the success of p&r that depends on intention and ability. the intention is the result of knowledge, social, and infrastructure that can support the use of public transport and p&r. this study aims to identify factors that can influence commuters' intentions to use p&r at sidoarjo station based on the theory of planned behavior using sem analysis. the results showed that p&r and public transportation conditions as perceived behavioral control were the most influential factors on commuter intentions. therefore, the conditions of public transportation (including availability and location) and the quality of p&r facilities are essential considerations for commuters using p&r. keywords: park and ride, transportation demand management, commuters, theory of planned behavior, structural equation model 1. introduction transportation is one of the keys to the development of a region [1]. along with the increasing population and the level of the community's economy, the number of private vehicle users from year to year continues to increase. the comparison between the number of transportation needs inversely proportional to the availability of proper and adequate transportation facilities causes various transportation problems, such as traffic congestion and air pollution [2]. besides limited infrastructure, transportation problems are also caused by the lack of sustainable transportation innovation, especially in developing countries [3]. based on fajar & djunaedi [4], big cities in indonesia still use the old or conventional transportation planning paradigm, namely widening roads without being accompanied by sustainable transportation innovations, especially to meet the needs of people's movements. there are several problems with urban transportation, including a limited public transportation network and lousy quality of public transportation services, so the use of private vehicles is the only access for people in sub-urban areas to go to the city center [5]. this condition causes a low use of public transportation for commuters in indonesia. 78% of urban people prefer private vehicles to public transportation [6]. mailto:saraairwt@gmail.com civil and environmental science journal vol. 05, no. 02, pp. 144-158, 2022 145 surabaya is the capital and economic center in east java province, one of the destinations for workers outside the surabaya city area. based on bps, the number of commuters in surabaya in 2018 reached 169,560 people. the area of origin that contributes the most significant percentage of commuters is the sidoarjo regency, with 40% or as many as 109,351 people of the total commuters in surabaya. along with the increasing number of commuters, surabaya has several alternative modes of transportation to move commuters from sidoarjo to surabaya, one of which is a commuter train with a large carrying capacity and short travel time [7]. however, based on the 2019 kai passenger data, the level of use of commuter trains in sidoarjo regency is still relatively low, which is only 3,176 people using commuter trains out of 109,351 inhabitants of the total number of sidoarjo people who are active in surabaya. therefore, it impacts the congestion level on the sidoarjo surabaya connecting road, which ranges from 0.90 to 1.58 [8]. the government has made various efforts to increase the use of public transportation for commuters. there is a plan based on rpjmd surabaya 2021 – 2026 to strengthen connectivity and accessibility to support the development of the gerbangkertasusila metropolitan area. one of the plans is in the form of public transportation development for the gerbangkertasusila metropolitan area, which consists of the surabaya regional railway line and the surabaya lrt. the construction of the surabaya regional railway line will connect surabaya to sidoarjo and become an alternative mode of transportation that can accommodate the needs of commuters. departing from this issue, the east java provincial government began to develop a plan to provide supporting facilities for public transportation, such as park and ride. park and ride (p&r) is a form of tdm in the improved transport option category in the form of parking facilities integrated with the public transportation network [9]. p&r facilities can reduce traffic congestion, increase the use of public transportation, and reduce parking areas in the city center [9]– [11]. p&r is synonymous with commuter activities because these facilities can be a liaison between the sub-urban area and the city center and function as a transfer node that can distribute travel d emand [4]. p&r has many positive impacts on facilitating the demand for public transport and helping to reduce the number of trips within an area [12]. sidoarjo station has the potential for developing p&r facilities because sidoarjo station is the largest origin station in the sidoarjo regency, with an average number of 1,200 passengers per day [7]. the various positive impacts of p&r still have not been able to encourage commuters to switch to using public transportation and use these facilities. based on the findings of research conducted by irawati [13], in existing conditions, the probability of commuters from sidoarjo surabaya who wants to move using commuter trains through the use of p&r is relatively low, at 44.3%. the low probability is caused by several factors, including the low quality and quantity of public transportation, the high cost, and the absence of a supportive transportation policy. on the other hand, the low use of p&r can also be influenced by people's behavior which is shaped by intention and ability. this condition is related to public acceptability, one of the important aspects of the success of sustainable transportation planning [3] behavioral is one of several keys to the success of p&r that depends on intention and ability. the intention is the result of knowledge, social, and infrastructure that can support the use of public transport and p&r. the commuter must have a positive attitude towards p&r and support by public transport conditions, parking facilities, and transportation policies to encourage the intention of commuters to use p&r [14]. this condition is expected to increase the probability of commuters using public transportation via p&r to 82.91% [13]. in line with this, parkhurst [15], in his findings, explains that implementing sustainable transportation strategies must be accompanied by changes in people's mindsets and habits, especially in developing countries. therefore, it is essential to discuss a person's motivation and behavior related to using p&r. however, the current state of the covid-19 pandemic impacts public transportation. javid et al. [16] and zhang et al. [17] explained that there was an increase in passenger anxiety because they considered public transportation to have a high risk of being exposed to the covid-19 virus. therefore, apart from implementing the social restriction policy, there was a 43% decrease in the number of public civil and environmental science journal vol. 05, no. 02, pp. 144-158, 2022 146 transportation users in east java. this condition is one of the transportation challenges that need to be faced by urban areas, especially areas with a high level of mobility because these conditions will also affect the use of public transportation and p&r facilities in the future. many developed countries already used p&r, such as the uk, canada, china, and hong kong. the existence of these facilities is considered successful in reducing congestion in the city center and increasing the use of public transportation. in addition, the implementation of p&r also has a good level of public acceptability as an early stage in efforts to increase the use of public transportation in line with the plan to develop an integrated public transportation network [2], [18], [19]. many studies have discussed p&r planning in developed countries, but research on p&r planning in developing countries is still limited. most research also only focuses on parking characteristics and public transportation conditions separately. however, only a few studies were found discussing the relationship between these two aspects and people's behavior towards the intention to use p&r facilities [9], especially during the covid-19 pandemic. in his previous research, ibrahim [9] tried to examine people's intentions using p&r based on the theory of planned behavior using several variables, including attitudes, subjective norms, perceived behavioral control, and beliefs. however, this research has not accommodated the condition of public transportation as a research variable. the condition of public transportation is the main consideration of the community in carrying out travel activities and determining the mode of transportation. guarantees regarding the availability of public transportation and good service quality are factors that encourage people to use public transportation and p&r [1], [10]. in addition, the quality of the p&r facilities offered is also an important consideration. the availability of public transportation and p&r conditions can be a perceived behavioral control because these facilities' existence can affect a person's attitude and behavior [20]. perceived behavioral control is an individual's beliefs about factors that can facilitate or hinder behavioral performance [21]. several studies that have been conducted have only been able to determine the effect of all dependent variables on commuter intentions, so they cannot examine the possible interactions between dependent variables that can affect people's intentions to use p&r [3], [4], [22]. therefore, this research is essential to find out and examine more deeply the community's behavior towards the use of p&r facilities in commuters based on the theory of planned behavior (tpb) using sem analysis. the respondent's determination is that commuters have a high level of mobility between regions and are the main targets of p&r planning. the theory of planned behavior (tpb) is one of the most widely used models to study the choice of travel modes [20]. the three main factors in the tpb, namely attitude, subjective norm, and perceived behavioral control, produce an intention to behave, take action, or anything that can guide a person's behavior. in this context, to arouse the motivation or intention of commuters to use p&r, the commuter must have a positive attitude towards public transportation and p&r, supported by the surrounding environment, and can use p&r (supported by public transport conditions, parking facilities, and transportation policies). sem analysis is expected to overcome the shortcomings of previous research to determine the dependent variable that can affect the commuter's intention to use p&r and determine the relationship between the dependent variables. this research is important to be carried out as study material for p&r planning, which is one form of sustainable transportation to overcome the problem of the low use of public transportation and traffic congestion at regional borders due to commuter activities in the future. 2. material and methods 2.1. data collection the location of this research is in sidoarjo regency, especially in the sidoarjo station area. data collection in this study was obtained from online distributing questionnaires to commuters in sidoarjo surabaya as the population in the study. the data were collected over two weeks in march 2022 and received responses from 150 commuters. the sample size of commuters from sidoarjo – surabaya was appropriate or more than the minimum sample size recommendation based on hair et al. [23], which civil and environmental science journal vol. 05, no. 02, pp. 144-158, 2022 147 uses the maximum number of arrows in one construct as a reference in determining the minimum sample requirement. the maximum number of arrows in one construct is the highest number of indicators in one variable. in this study, the highest number of indicators was eight, namely the perceived behavioral control variable. this study uses a significant level of 5% with a minimum r2 of 0.1, so the minimum sample size required is 144 samples. 2.2. research instruments and measurements the research method used is quantitative research. there are five research variables obtained through the study of literature. the five variables consist of several indicators and are measured using a likert scale, ranging from 1 = "strongly disagree" to 5 = "strongly agree." in addition, questions related to the characteristic of commuters (gender, age, education, and occupation) and those related to the use of the mode of transportation were also included. the pls-sem model in this study consists of five constructs of variables and twenty-two items or indicators that identify the factors that influence commuters' intention to use p&r based on the theory of planned behavior. variables and indicators were obtained from literature studies and modified according to the research objectives to identify factors influencing commuters' intentions to use p&r during the covid-19 pandemic. intention to use p&r influenced by attitude consist of three items [6], [9], [24], [25], subjective norm consist of three items [6], [24], [26], perceived behavioral control, including p&r and public transportation conditions that consist of eight items [1], [5], [17], [27]–[30], policy, including vehicle use restrictions, parking restrictions in city center, and the use of public transportation during the covid-19 pandemic that consist of six items [15], [21], [31], [32], and intention to use p&r [6], [9], [24]. table 1. research variables variable indicator parameter source attitude a1. using p&r is a good idea 1= very disagree 2= disagree 3= neutral 4= agree 5= strongly agree [6], [9], [24], [25] a2. using p&r provides many advantages a3. using p&r support public transportation use behavior subjective norm sn1. people closest to me use p&r 1= do not know 2= no 3= yes [6], [24], [26] sn2. people who are my role models use p&r sn3. people important to me recommend using p&r perceived behavioral control pbc1. p&r’s location is strategic and easy to access 1= very disagree 2= disagree 3= neutral 4= agree 5= strongly agree [1], [5], [17], [27]–[30] pbc2. plenty of available parking capacity pbc3. p&r has good service quality pbc4. the security and safety in p&r pbc5. the availability of parking spaces information pbc6. availability of public transportation pbc7. cleanliness of public transportation during the covid-19 pandemic pbc8. the public transportation conditions around p&r during the covid-19 pandemic made it easier for me to use p&r civil and environmental science journal vol. 05, no. 02, pp. 144-158, 2022 148 policy p1. the implementation of the vehicle use restriction policy hindered my trip 1= very disagree 2= disagree 3= neutral 4= agree 5= strongly agree [15], [21], [31]–[33] p2. the implementation of the vehicle use restriction policy encourages me to use p&r p3. the implementation of a parking restriction policy in the city center makes it difficult for me p4. the implementation of a parking restriction policy in the city center encourages me to use p&r p5. the policy of public transportation during the covid-19 pandemic has been implemented properly p6. the implementation of public transportation policy during the covid-19 pandemic encourages me to use p&r intention to use p&r i1. i want to use p&r 1= do not know 2= no 3= yes [6], [24], [26] i2. i will use p&r 2.3. analysis the data obtained from data collection will be analyzed using structural equation model (sem). a structural equation model (sem) is a combination of multivariate statistical techniques (factor analysis and regression) which aims to examine the relationship between variables in a model, both between indicators and constructs or relationships between constructs [6]. based on hair et al. [23], there are two types of structural equation modeling, namely covariance-based (cb-sem) and variancebased (pls-sem). this study uses pls-sem to identify the factors influencing the commuter's intention to use p&r and the interrelationships between the variables. the pls-sem model is the result of a combination between theory and logical reasoning. there are two-step approaches in pls-sem, namely the measurement and structural models. first, the evaluation of the measurement model using a reflective approach is carried out by evaluating the value of outer loading, construct reliability and validity (cr and ave), and discriminant validity. meanwhile, the measurement model using a formative approach is carried out by evaluating the collinearity level of the vif value and measuring the significance level of the outer weight and outer loading values. structural model evaluation is generally more accessible, as seen from the t-statistical value and p-value, which show the significance level between one latent variable and other variables. the measurement and structural models were evaluated according to hair et al. [34]. 3. result and discussion 3.1. characteristics of sidoarjo surabaya commuters sidoarjo regency is one of the cities in the gerbangkertasusila metropolitan area, with the city of surabaya as the center of its activities. one of the impacts of this condition is the high number of commuters in the sidoarjo regency, along with the increasing number of jobs available in surabaya. a commuter has a pattern of moving from one point to another without having the intention of settling down. the move is often motivated by education and work. in this study, the commuters are workers who live in sidoarjo and work in surabaya using private vehicles (cars and motorcycles). data collection civil and environmental science journal vol. 05, no. 02, pp. 144-158, 2022 149 regarding the characteristics of commuters in sidoarjo – surabaya was conducted through questionnaires distributed online to 150 commuters in sidoarjo surabaya. table 2. characteristic of respondents variable characteristic gender 73% male; 27% female age 4% less than 20 years old; 37% 20 – 30 years old; 31% 30 – 40 years old; 20% 40 – 50 years old; and 8% more than 50 years old education 7% junior high school; 31% senior high school; 19% diploma i/ii/iii; 34% undergraduate; 9% graduate, and 2% postgraduate occupation 7% students; 15% government employees; 34% private sector employees; 12% teachers or lecturers; 10% trader, 14% entrepreneur; and 5% others use of transportation modes 72% motorcycle users; 28% car users the questionnaire results show that commuters from sidoarjo – surabaya are dominated by motorcycle users by 72% and males by 73%. the average sidoarjo – surabaya commuter is 20 to 30 years old. this condition shows that most of the commuters from sidoarjo – surabaya are of working productive age. meanwhile, from the type of work and education level, most of the commuters from sidoarjo – surabaya have the latest undergraduate education level and work as private employees. in addition, in the characteristics of transportation modes, identification of the number of vehicle ownership for sidoarjo – surabaya commuters is also carried out, both two-wheeled vehicles (motorcycles) and four-wheeled vehicles (cars). table 3. number of vehicle ownership in sidoarjo surabaya commuters types of transportation modes number of vehicles (unit) total 0 1 – 2 3 – 4 more than 4 units car 48 93 9 0 150 motorcycle 20 100 28 2 150 the average sidoarjo – surabaya commuter has two types of vehicles, namely cars and motorcycles, with a total of 1 – 2 vehicle ownership units per vehicle type. as many as 67% of the commuters from sidoarjo – surabaya have 1-2 units of motorbikes, and 62% have 1-2 units of cars. this condition shows that the average vehicle ownership of commuters in sidoarjo – surabaya is still relatively high compared to commuters in several other developed countries, such as singapore, japan, and germany. 3.2. measurement model the measurement model is a model that contains the relationship between the latent variable and its indicators. there are two ways to measure a latent variable: reflective and formative [23]. the first stage in evaluating the measurement model using a reflective approach is the value of the outer loading on each indicator. based on hair et al. (2019), the outer loading on each indicator must at least have a value above 0.708. the results showed that of the 14 existing indicators, 13 indicators were following the pls-sem standard because they had an outer loading above 0.708 (table 2). therefore, it shows that these indicators can explain the latent variable by more than 50%, which can be said to be reliable. in addition, from the measurement results, there is one indicator with an outer loading value below civil and environmental science journal vol. 05, no. 02, pp. 144-158, 2022 150 0.708, namely the sn3 indicator (0.592). therefore, it is necessary to eliminate the sn3 indicator to obtain a better model. the results of the research findings explain that the subjective norm variable shows that of the three indicators, the sn3 indicator does not affect the commuter's intention to use p&r. meanwhile, sn1 and sn2 influence commuters to use p&r at sidoarjo station. this condition is in line with brohi et al. [24], which state that the role of someone considered necessary, close, or professional influences a person's intention to take specific actions. in this study, the intentions of the sidoarjo surabaya commuters cannot be formed simply through one-way direction but need to be accompanied by evidence through actions taken by people in the surrounding environment, which indirectly creates a "pressure" that can lead to an urge to take action. based to ingvardson & nielsen [37], the behavior of people in the surrounding environment can form a social norm that can indirectly encourage the formation of certain attitudes or actions. in this context, the use of p&r. the results give an alternative solution to increase the use of p&r among commuters, namely through socialization and promotion, as well as activities that can shape people's behavior, such as the pro-public transportation movement and the environmentfriendly movement. furthermore, the second stage in evaluating the measurement model is to test the reliability and validity of the model through the value of consistency reliability (cr) and ave. based on hair et al. [34], the standard cr value is more than 0.7, and the ave value is above 0.5. table 2 shows that the four latent variables have cr values above 0.7 and ave above 0.5, namely attitude (cr: 0.844; ave: 0.664), subjective norm (cr: 0.775; ave: 0.540), policy (cr :0.929; ave:0.688), and intention (cr:0.947; ave:0.899), so it can be said that the model is reliable and valid. the last stage is the measurement of discriminant validity through the htmt value. in this study, when referring to the plssem standard based on hair et al. [34], the value of htmt in a pls-sem model is less than 0.90 because the theory about p&r is still quite limited. the result shows that four latent variables have met the standard htmt value of less than 0.90. it explains that all latent variables in the pls-sem model of this study are valid. table 4. measurement model evaluation with reflective approach variable and indicator outer loading cr ave attitude 0,844 0,664 a1. using p&r is a good idea 0,854 a2. using p&r provides many advantages 0,803 a3. using p&r support public transportation use behavior 0,747 subjective norm 0,775 0,540 sn1. people closest to me use p&r 0,840 sn2. people who are my role models use p&r 0,751 sn3. people important to me recommend using p&r 0,592 policy 0,929 0,688 p1. the implementation of the vehicle use restriction policy hindered my trip 0,874 p2. the implementation of the vehicle use restriction policy encourages me to use p&r 0,890 p3. the implementation of a parking restriction policy in the city center makes it difficult for me 0,833 civil and environmental science journal vol. 05, no. 02, pp. 144-158, 2022 151 variable and indicator outer loading cr ave p4. the implementation of a parking restriction policy in the city center encourages me to use p&r 0,795 p5. the policy of public transportation during the covid-19 pandemic has been implemented properly 0,830 p6. the implementation of public transportation policy during the covid-19 pandemic encourages me to use p&r 0,745 intention 0,947 0,899 i1. i want to use p&r 0,953 i2. i will use p&r 0,944 the first step in evaluating the measurement model using a formative approach is to see the level of collinearity of the model's vif value. based on hair et al. [34], the standard vif value is below 3. therefore, indicators with a vif value of more than three must be reduced or eliminated to obtain better model accuracy. for example, table 3 shows that 7 of the eight indicators have a vif value of less than 3, while the other 1 has a vif value above 3, namely pbc1 (vif: 4,939), which indicates multicollinearity. therefore, based on the collinearity level test, it is necessary to eliminate the pbc1 indicator. next, in the second stage, measuring the level of significance seen through the p-value on the outer weight. measurements in the second stage are carried out after the bootstrapping process. a p-value of less than 0.05 indicates that the indicator significantly influences the latent variable. indicators with a p-value of more than 0.05 will be eliminated [23]. however, this indicator can still be maintained if it has an outer loading value of more than 0.50. based on this explanation, out of the eight indicators, 6 of them are significant, while the other two indicators, namely pbc1 and pbc7, have values above 0.05. when referring to the pls-sem standard based on hair et al. [23], the pbc1 indicator needs to be eliminated because it is insignificant and has an outer loading value of less than 0.50. table 5. measurement model evaluation with formative approach variable and indicator outer loading outer weight vif p-value perceived behavioral control pbc1. p&r’s location is strategic and easy to access 0,012 0,236 4,939 0,446 pbc2. plenty of available parking capacity 0,850 0,569 1,746 0,010 pbc3. p&r has good service quality 0,872 0,463 2,762 0,033 pbc4. the security and safety in p&r 0,743 0,161 2,788 0,044 pbc5. the availability of parking spaces information 0,530 0,173 2,369 0,037 pbc6. availability of public transportation 0,470 0,140 2,939 0,035 pbc7. cleanliness of public transportation during the covid-19 pandemic 0,598 0,320 1,720 0,104 pbc8. the public transportation conditions around p&r during the covid-19 pandemic made it easier for me to use p&r 0,416 0,162 2,616 0,047 civil and environmental science journal vol. 05, no. 02, pp. 144-158, 2022 152 the literature studies explain that the location of p&r is one of the factors that can affect the level of use of p&r. but, in some cases, especially for commuters, the availability of public transportation and adequate parking capacity has a more significant influence than the location in influencing commuters' intentions to use p&r. [27], [31], [38]. therefore, the pbc1 indicator (strategic and easily accessible p&r location) can be eliminated by evaluating the measurement model and the literature study. meanwhile, from the results of the measurement model evaluation, the pbc7 indicator is still maintained because even though it is not significant, the indicator has an outer loading value of more than 0.50, which is 0.598. this condition is also reinforced by the covid-19 pandemic, which causes changes in people's behavior in mode selection activities, where cleanliness is one of the essential aspects that people consider when using public transportation during the pandemic [16], [17], [39]. in the initial pls-sem model, there are five variables and 22 indicators. based on the measurement model results, using both reflective and formative approaches, several indicators need to be eliminated because they are not following pls-sem standards. the indicators that need to be reduced are sn3, pbc7, and pb8. so out of 22 indicators, only 19 will be used in the final model. furthermore, measurement model evaluations were carried out in the final model to determine the suitability of the pls-sem model. table 6. final measurement model evaluation with reflective approach variable and indicator outer loading cr ave attitude 0,844 0,664 a1. using p&r is a good idea 0,855 a2. using p&r provides many advantages 0,808 a3. using p&r support public transportation use behavior 0,741 subjective norm 0,824 0,701 sn1. people closest to me use p&r 0,850 sn2. people who are my role models use p&r 0,825 policy 0,929 0,688 p1. the implementation of the vehicle use restriction policy hindered my trip 0,872 p2. the implementation of the vehicle use restriction policy encourages me to use p&r 0,889 p3. the implementation of a parking restriction policy in the city center makes it difficult for me 0,826 p4. the implementation of a parking restriction policy in the city center encourages me to use p&r 0,796 p5. the policy of public transportation during the covid-19 pandemic has been implemented properly 0,835 p6. the implementation of public transportation policy during the covid-19 pandemic encourages me to use p&r 0,749 intention 0,947 0,899 i1. i want to use p&r 0,952 i2. i will use p&r 0,944 civil and environmental science journal vol. 05, no. 02, pp. 144-158, 2022 153 table 7. final measurement model evaluation with formative approach variable and indicator outer loading outer weight vif p-value perceived behavioral control pbc2. plenty of available parking capacity 0,858 0,575 1,744 0,858 pbc3. p&r has good service quality 0,881 0,461 2,693 0,881 pbc4. the security and safety in p&r 0,745 0,189 2,748 0,745 pbc5. the availability of parking spaces information 0,527 0,189 2,778 0,527 pbc6. availability of public transportation 0,481 0,154 2,830 0,481 pbc7. cleanliness of public transportation during the covid-19 pandemic 0,596 0,329 1,715 0,596 pbc8. the public transportation conditions around p&r during the covid-19 pandemic made it easier for me to use p&r 0,412 0,168 2,615 0,412 3.3. structural model the structural model is a model that contains latent variables to show the relationship between one variable and other latent variables. determining the order or path relationship between latent variables is based on the literature study results. structural model evaluation is generally more accessible, seen from the t-statistical value and p-value, which show the significance level between one latent variable and other variables. based on hair et al. [34], the first stage in evaluating the structural model is looking at the t-statistical value. the pls-sem model can be accepted if the t-statistic value is greater than the t-table value. the number of variables in this study was 5, so if using a significance value of 0.05, the ttable was 2.01505. table 4 shows that all variables have a t-statistic value greater than the t-table, except for the relationship between the policy variable and attitude, which has a t-statistic value of 1.509 (smaller than the t-table). next, the evaluation looks at the p-value. the relationship between one variable and another can be significant if it has a p-value less than 0.05. the results of the structural model measurement show that six of the seven hypotheses are accepted and are significant because they have a p-value of less than 0.05. meanwhile, the hypothesis that the policy variable affects attitude has a p-value of more than 0.05, which means it is not significant, so the research hypothesis is rejected. table 8. structural model evaluation variable b t-value p-value description attitude → intention 0,303 3,193 0,001 significant subjective norm → intention 0,489 5,725 0,000 significant perceived behavioral control → intention 0,498 5,327 0,020 significant policy → intention 0,266 2,508 0,012 significant policy → attitude 0,205 1,509 0,131 not significant policy → subjective norm 0,292 2,493 0,013 significant subjective norm → attitude 0,722 13,025 0,000 significant a person's attitudes and behavior are also related to the policies that apply in an area, both written and unwritten (norms) [21]. the existence of a policy will suppress and limit a person's actions so that it can affect his attitudes and behavior. however, this is not in line with this study's findings, which civil and environmental science journal vol. 05, no. 02, pp. 144-158, 2022 154 show that the policy does not affect a person's attitude and behavior. this condition can occur due to the low level of public trust in the government and the effectiveness and efficiency of the policies drawn up. the level of public trust and acceptance is the key to successfully planning government programs. policies that are applied equitably and fairly, accompanied by the socialization of policies to the public, can accelerate changes in attitudes and behavior. in some conditions, the role of the government as regional leaders as well as important figures who are role models for the community in disseminating policies and contributing to the implementation of policies will encourage people to take specific actions [6], [32]. the study's results indicate that the policy affects the subjective norm and can indirectly affect the attitudes and behavior of commuters. therefore, one way to increase the use of p&r is to increase trust and public acceptance of the government and its programs. a high level of public trust can affect the condition of the community in an area and accelerate changes in attitudes and behavior. in this context are attitudes and behaviors that can encourage the use of p&r. 3.4. intention commuters to use p&r in sidoarjo station research findings indicate that the intention of commuters from sidoarjo – surabaya to use p&r at sidoarjo station is influenced by several factors, including attitude, subjective norm, perceived behavioral control, and policy. if sorted based on the value of the coefficient on each variable, the perceived behavioral control variable related to the p&r condition has the most significant influence on the commuter's intention (0.498). then continued with the variables were the subjective norm (0.489), attitude (0.303), and policy (0.266). these four variables significantly affect the intention of commuters from sidoarjo surabaya to use p&r. figure 1 shows the final result of the pls-sem analysis. the significance level of the relationship between variables is shown with the symbol (***), which means the hypothesis is accepted and has a p-value less than 0.05 (significant). meanwhile, the size of their influence can see through the thickness of connecting line between latent variables: the thicker line, the more significant impact or influence. the commuter's decision to use p&r can be influenced by one's perception of the facility, such as the knowledge and experience commuters possess to form a perception that can influence their actions. in the context of using p&r, brohi et al. [24] explain that a person's optimistic view of the existence of a facility can encourage someone to use the facility. this statement is in line with the findings of this study which showed that attitude significantly affected commuter intentions. the better a person's view of the benefits and existence of p&r, the greater the commuter's intention to use the facility. several indicators affect the attitude variable, namely: 1. p&r is a good innovation/idea (0.486; 0.000) 2. p&r provides many advantages (0.382; 0.000) 3. p&r supports the public transport use behavior (0.372; 0.000) the tendency of a person to perceive p&r as innovation and a good idea in a transportation plan, the better their attitude towards the use of p&r. in addition, in line with the research of yan [40], commuters will consider the most significant advantages when choosing the mode of transportation to be used. so the more benefits one gets from using p&r, the better one's perception and attitude towards the facility. the higher commuter's awareness of public transportation use behavior encourages the positive commuter's attitude towards p&r. a person's intention to use public transportation and p&r is also influenced by social conditions and the role of the closest people who are considered to have an important position. it tells that when someone is aware, their attitudes and behavior can be imitated by those closest to them [9]. the results showed that the subjective norm variable significantly influenced the commuter's intention to use p&r. several indicators affect the subjective norm variable, including: 1. the closest people use p&r (0.617; 0.000) 2. people who are role models use p&r (0.576; 0.000) the more people closest to and are role models use p&r, the better it affects the surrounding environment and encourages commuters' intentions to use p&r. the research findings indicate that the subjective norm variable influences attitude. civil and environmental science journal vol. 05, no. 02, pp. 144-158, 2022 155 figure 1. final pls-sem model of the intention to use p&r the social conditions of commuters indirectly can influence their perception and encourage commuters to use p&r. on the other side, the commuter's intention to use p&r is influenced by the conditions and facilities that can encourage the formation of an attitude and behavior. in this case, the p&r itself. the perceived behavioral control variable significantly influences the commuter's intention, showing that the better the p&r condition, the greater the commuter's intention to use the facility. several indicators influence the perceived behavioral control variable, including: 1. plenty of available parking capacity (0.575; 0.010) 2. p&r has good service quality (0.461; 0.033) 3. security and safety offered by p&r facilities (0.189; 0.044) 4. information regarding the availability of parking spaces is clear (0.189; 0.037) 5. availability of public transportation around p&r (0.154; 0.035) the research findings explain that the success of p&r implementation is determined by several factors, including the availability of parking spaces and complementary facilities. the better the quality of p&r services, including regarding security, safety, and ease of obtaining information, the greater the public trust and satisfaction with the implementation of p&r. in addition, the availability of public transportation modes also encourages the formation of using p&r. these findings align with the research of handaeyani & ariyani [27] and ibrahim et al. [9]. they say that the availability of public transportation modes is one aspect that affects the level of use of p&r. in the context of commuter travel, the availability of public transportation modes that are easily accessible with a good travel frequency becomes the primary consideration for commuters when using p&r. based on several studies on sustainable transportation planning, transportation policy is one aspect that can support the implementation of p&r at sidoarjo station. the findings show that the policy variable significantly influences the commuter's intention to use p&r. the higher the strictness of a policy, the higher the intention of commuters. in addition, the policy also influences the subjective norm variable. applying policies in an area indirectly affects social conditions or the surrounding environment, which can also affect commuters' intentions to use p&r. several indicators affect policy variables, including: civil and environmental science journal vol. 05, no. 02, pp. 144-158, 2022 156 1. the implementation of the vehicle use restriction policy hinders commuter travel (0.214; 0.001) 2. the implementation of the vehicle use restriction policy encourages commuters to use p&r (0.233; 0.001) 3. the implementation of a parking restriction policy in the city center makes it difficult for commuters (0.207; 0.004) 4. the implementation of a parking restriction policy in the city center encourages commuters to use p&r (0.165; 0.047) 5. the policy on the use of public transportation during the covid-19 pandemic has been appropriately implemented (0.213; 0.001) 6. implementation of policies on the use of public transportation following health protocols encourages commuters to use p&r (0.167; 0.046) furthermore, a person's attitudes and behavior, in general, are also related to the policies that apply in an area. the existence of a policy will suppress and limit a person's actions so that it can affect his attitudes and behavior. in addition, policies that are applied equitably and fairly, accompanied by the socialization of policies to the public, can accelerate changes in attitudes and behavior. if it is related to the covid-19 pandemic that has occurred since the beginning of 2019, it certainly has influenced people's behavior and perception of public transportation. the research findings show that exemplary implementation of policies can increase the public trust and encourage the intention of sidoarjo surabaya commuters to use p&r. research results also show that public transportation conditions around p&r during the covid-19 pandemic make it easier for commuters to use p&r (0.168; 0.046). 4. conclusions in achieving the success of p&r planning and other forms of sustainable transportation, infrastructure planning must be accompanied by a change in mindset and behavior, especially in developing countries. behavioral is one of several keys to the success of p&r that depends on intention and ability. therefore, this study aims to identify the influence of knowledge, social conditions, parking facilities, public transportation conditions, and policies on commuters' intentions in using p&r. the results indicate that the four variables significantly affect the intention of the commuter. the perceived behavioral control variable obtained the most significant influence value. this result can be interpreted that the conditions of public transportation and the quality of the p&r facilities are among the strongest driving factors for people to use p&r. the more benefits obtained, the greater the commuter's intention to use p&r. on the other hand, this solution also needs to be accompanied by the government's commitment to socializing and publishing, as well as strengthening the implementation of policies to enforce vehicle-free areas in the city center, restrictions on parking in the city center, and implementation of health protocols. references [1] x. zhao, y. li, and h. xia, “behavior decision model for park-and-ride facilities utilization,” adv. mech. eng., vol. 9, no. 7, pp. 1–9, 2017, doi: 10.1177/1687814017708907. [2] k. huang, z. liu, t. zhu, i. kim, and k. an, “analysis of the acceptance of park-and-ride by users: a cumulative logistic regression approach,” j. transp. land use, vol. 12, no. 1, pp. 637– 647, 2019, doi: 10.5198/jtlu.2019.1390. [3] m. k. s. perera, v. waidyasekara, and s. dissanayake, “commuters perception towards the bus base park and ride implementation in colombo city limit,” cinec acad. j., vol. 5, no. 1, pp. 36–45, 2021. [4] i. fajar and a. djunaedi, “factors that influencing informal park and ride facility choice in indonesia: case study of kendal regency,” j. ilm. univ. batanghari jambi, vol. 20, no. 1, p. 54, 2020, doi: 10.33087/jiubj.v20i1.789. [5] f. r. widayanti and a. r. pattisinai, “investigate park and ride performance assessment for the better sustainable urban transportation in surabaya,” iop conf. ser. mater. sci. eng., vol. 1098, no. 2, p. 022019, 2021, doi: 10.1088/1757-899x/1098/2/022019. civil and environmental science journal vol. 05, no. 02, pp. 144-158, 2022 157 [6] p. dirgahayani and h. sutanto, “the effect of transport demand management policy on the intention to use public transport: a case in bandung, indonesia,” case stud. transp. policy, vol. 8, no. 3, pp. 1062–1072, 2020, doi: 10.1016/j.cstp.2020.03.004. [7] a. r. nurkhariza and s. nurlaela, “faktor-faktor yang memengaruhi permintaan commuter line berdasarkan karakteristik fasilitas park and ride di stasiun sidoarjo,” j. transp. sist. mater. dan infrastruktur, vol. 1, no. 2, p. 106, 2019, doi: 10.12962/j26226847.v1i2.5035. [8] dllaj, “masterplan transportasi kota surabaya,” 2017. [9] a. n. h. ibrahim, m. n. borhan, and r. a. o. k. rahmat, “understanding users’ intention to use park-and-ride facilities in malaysia: the role of trust as a novel construct in the theory of planned behaviour,” sustain., vol. 12, no. 6, 2020, doi: 10.3390/su12062484. [10] a. asapa, “park and ride sebagai bagian dari pelayanan kereta api perkotaan bandung,” j. perenc. wil. dan kota, vol. 25, no. 2, pp. 157–173, 2014, doi: 10.5614/jpwk.2015.25.2.5. [11] e. macioszek and a. kurek, “the use of a park and ride system a case study based on the city of cracow (poland),” energies, vol. 13, no. 13, 2020, doi: 10.3390/en13133473. [12] m. suryandari, a. wicaksono, and i. w. agustin, “the implementation of park and ride at bekasi station,” tataloka, vol. 17, pp. 172–185, 2015, [online]. available: https://doi.org/10.14710/tataloka.17.3.172-185. [13] s. irawati, i. w. agustin, i. rini, and d. ari, “potensi park and ride dalam mendukung penggunaan kereta api komuter di stasiun sidoarjo,” plan. urban reg. environ. vol., vol. 10, no. 3, pp. 159–168, 2021. [14] h. gan and x. ye, “will commute drivers switch to park-and-ride under the influence of multimodal traveler information? a stated preference investigation,” transp. res. part f traffic psychol. behav., vol. 56, pp. 354–361, 2018, doi: 10.1016/j.trf.2018.05.015. [15] w. clayton, e. ben-elia, g. parkhurst, and m. ricci, “where to park? a behavioural comparison of bus park and ride and city centre car park usage in bath, uk,” j. transp. geogr., vol. 36, pp. 124–133, 2014, doi: 10.1016/j.jtrangeo.2014.03.011. [16] m. ashraf javid, m. abdullah, n. ali, and c. dias, “structural equation modeling of public transport use with covid-19 precautions: an extension of the norm activation model,” transp. res. interdiscip. perspect., vol. 12, no. october, p. 100474, 2021, doi: 10.1016/j.trip.2021.100474. [17] x. zhang, d. liu, y. wang, and h. du, “behavioral intentions of urban rail transit passengers during the covid-19 pandemic in tianjin , china : a model integrating the theory of planned behavior and customer satisfaction theory,” vol. 2021, 2021. [18] e. macioszek and a. kurek, “the analysis of the factors determining the choice of park and ride facility using a multinomial logit model,” energies, vol. 14, no. 1, 2021, doi: 10.3390/en14010203. [19] t. zijlstra, t. vanoutrive, and a. verhetsel, “a meta-analysis of the effectiveness of park-andride facilities,” eur. j. transp. infrastruct. res., vol. 15, no. 4, pp. 597–612, 2015, doi: 10.18757/ejtir.2015.15.4.3099. [20] j. k. liang, t. eccarius, and c. c. lu, “investigating factors that affect the intention to use shared parking: a case study of taipei city,” transp. res. part a policy pract., vol. 130, no. september, pp. 799–812, 2019, doi: 10.1016/j.tra.2019.10.006. [21] k. zhang, h. guo, g. yao, c. li, y. zhang, and w. wang, “modeling acceptance of electric vehicle sharing based on theory of planned behavior,” sustain., vol. 10, no. 12, pp. 1–14, 2018, doi: 10.3390/su10124686. [22] h. a.-r. lubis, b. hasibuan, and m. farda, “users’ perception of private park and ride facilities in cawang area, jakarta, indonesia,” j. tek. sipil, vol. 26, no. 3, p. 205, 2019, doi: 10.5614/jts.2019.26.3.3. [23] j. hair, g. t. hult, c. ringle, and m. sarstedt, a primer on partial least squares structural equation modeling (pls-sem) joseph f. hair, jr., g. tomas m. hult, christian ringle, marko sarstedt. 2017. civil and environmental science journal vol. 05, no. 02, pp. 144-158, 2022 158 [24] s. brohi, s. kalwar, i. a. memon, and a. ghaffar, “using the theory of planned behavior to identify the behavioral intention to use public transportation service: the case study of karachi circular railway,” int. j. emerg. technol, vol. 12, no. 6, 2021. [25] s. haustein and m. hunecke, “reduced use of environmentally friendly modes of transportation caused by perceived mobility necessities: an extension of the theory of planned behavior,” j. appl. soc. psychol., vol. 37, no. 8, pp. 1856–1883, 2007, doi: 10.1111/j.15591816.2007.00241.x. [26] h. d. hussain, “predicting the commuter’s willingness to use lrt, utilising the theory of planned behaviour and structural equation,” j. appl. eng. sci., vol. 18, no. 3, pp. 403–412, 2020, doi: 10.5937/jaes18-27013. [27] k. d. m. e. handayeni and b. s. p. ariyani, “commuters’ travel behaviour and willingness to use park and ride in tangerang city,” iop conf. ser. earth environ. sci., vol. 202, no. 1, 2018, doi: 10.1088/1755-1315/202/1/012019. [28] s. e. palupiningtyas, “kriteria fasilitas park and ride sebagai pendukung angkutan umum massal berbasis jalan,” war. penelit. perhub., vol. 27, no. 2, p. 69, 2019, doi: 10.25104/warlit.v27i2.768. [29] b. sharma, strategic approach in analysing the demand for park-and-ride facilities, no. civil. 2019. [30] x. n. sun, y. y. mai, and x. g. wang, “the structural equation model for public evaluation of the transfer efficiency of rail transit p&r facilities,” appl. mech. mater., vol. 368–370, no. 1, pp. 2027–2033, 2013, doi: 10.4028/www.scientific.net/amm.368-370.2027. [31] c. chen, j. (cecilia) xia, b. smith, d. olaru, j. taplin, and r. han, “influence of parking on train station choice under uncertainty for park-and-ride users,” procedia manuf., vol. 3, no. ahfe, pp. 5126–5133, 2015, doi: 10.1016/j.promfg.2015.07.537. [32] r. sayyadi and a. awasthi, “an integrated approach based on system dynamics and anp for evaluating sustainable transportation policies,” int. j. syst. sci. oper. logist., vol. 7, no. 2, pp. 182–191, 2020, doi: 10.1080/23302674.2018.1554168. [33] b. he, w. he, and m. he, “the attitude and preference of traveler to the park & ride facilities: a case study in nanjing, china,” procedia soc. behav. sci., vol. 43, no. 01186, pp. 294–301, 2012, doi: 10.1016/j.sbspro.2012.04.102. [34] j. f. hair, j. j. risher, m. sarstedt, and c. m. ringle, “when to use and how to report the results of pls-sem,” eur. bus. rev., vol. 31, no. 1, pp. 2–24, 2019, doi: 10.1108/ebr-11-2018-0203. [35] s. setyodhono, “faktor yang mempengaruhi pekerja komuter di jabodetabek menggunakan moda transportasi utama,” war. penelit. perhub., vol. 29, no. 1, p. 21, 2017, doi: 10.25104/warlit.v29i1.326. [36] a. d. irjayanti, d. w. sari, and i. rosida, “perilaku pemilihan moda transportasi pekerja komuter: studi kasus jabodetabek,” j. ekon. dan pembang. indones., vol. 21, no. 2, pp. 125– 147, 2021, doi: 10.21002/jepi.v21i2.1340. [37] j. b. ingvardson and o. a. nielsen, “the relationship between norms, satisfaction and public transport use: a comparison across six european cities using structural equation modelling,” transp. res. part a policy pract., vol. 126, no. may, pp. 37–57, 2019, doi: 10.1016/j.tra.2019.05.016. [38] x. shen, f. chen, b. su, q. chen, and j. yao, “optimization of park-and-ride system: a case study of shunyi in beijing,” adv. mech. eng., vol. 9, no. 8, pp. 1–8, 2017, doi: 10.1177/1687814017714987. [39] a. tirachini, “covid-19 and public transportation: current assessment, prospects, and research needs,” j. public transp., vol. 22, no. 1, pp. 1–21, 2020. [40] x. yan, j. levine, and r. marans, “the effectiveness of parking policies to reduce parking demand pressure and car use,” transp. policy, vol. 73, pp. 41–50, 2019, doi: 10.1016/j.tranpol.2018.10.009. open access proceedings journal of physics: conference series civil and environmental science journal vol. iii, no. 01, pp. 051-059, 2020 51 slope stability analysis in ulubelu lampung using computational analysis program1 jafri m1, iswan1, rizki m1, and susilo g.e1 1civil engineering department, universitas lampung, 35145, indonesia jafri@unila.ac.id received 02-03-2020; accepted 27-03-2020 abstract. ulubelu sub-district is the center of geothermal activity in lampung province. the ulubelu geothermal project supply 25% of electricity to lampung province. in the future the government plans to build a geothermal pipeline network with the aim of maximizing the potential found in ulubelu. one of the objects that must be examined in the construction of the pipeline is the stability of the slope that will be passed by geothermal pipes. therefore, this study aims to analyze the stability of landslides in the ulubelu geothermal pipeline. soil samples for this study were taken from 5 locations: bh-01, bh-02, bh-03, bh-04, and bh-05. this soil sample is then examined to determine its soil mechanics characteristics in the laboratory. the safety factor of each sample is analyzed using 3 slope analysis methods: the fellenius method, the bishop method, and the janbu method, and calculated in geostudio (slope/w). the results showed that all samples showed safety factor values that were not much different that were spread between the numbers 1.7 to 4.3. this shows that all sample locations are safe from landslides. this also shows that the characteristics of the soil and the slope of the study area are almost the same. keywords: slope, safety factor, fellenius, bishop, janbu, geostudio(slope/w) 1. introduction tanggamus is one of the areas in lampung that has a large geothermal potential. the lampung provincial government claims the province has a geothermal potential of 2,867 mw or 10% of indonesia's total geothermal potential. with this potential, the province is ranked third after west java and north sumatra as the province with the largest geothermal potential in the country. overall, the government said indonesia's geothermal energy potential was 29,000 mw. the international geothermal association (iga) states that indonesia has the third largest installed capacity after the us and the philippines, with a capacity of 1,340 mw as of 2015. meanwhile, the us and the philippines have an installed capacity of 3,450 mw and 1,870 mw, respectively. ulubelu sub-district is the center of geothermal activity in tanggamus. it is located in the hills with a distance of about 3-4 hours by road from bandar lampung, the capital of lampung province. to reach the location, we must pass ravines, cliffs and forests. there is the ulubelu geothermal power plant (pltp) owned by pt 1 cites this as: jafri, m., iswan, rizki, m., & susilo, g.e. (2000). slope stability analysis in ulubelu lampung using computational analysis program. civil and environmental science journal, 3(1), pp.51-59. doi: https://doi.org/10.21776/ub.civense.2020.00301.6 civil and environmental science journal vol. iii, no. 01, pp. 051-059, 2020 52 pertamina geothermal energy (pge) which has four electricity generating units. pge is a subsidiary of pt pertamina (persero) which focuses on geothermal development. geothermal development in the ulubelu region has actually been carried out since 1991. however, the monetary crisis that occurred 20 years ago made the project halted. pge only started to develop again in 2008. ulubelu pltp is not the only power plant that uses renewable energy. the development and opening of new wells continue at ulu belu to meet the supply of fuel to power plants. the contribution of 25% of electricity supply to lampung province is the main advantage of the utilization of ulubelu geothermal energy [1]. figure 1. map of tanggamus district and the location of ulu belu in the future the government plans to build a geothermal pipeline network with the aim of maximizing the potential found in ulubelu. to build a geothermal pipe that can last a long time, it is necessary to calculate the soil safety factor so that the foundation of the geothermal pipe is resistant to the load that will be placed on it. therefore, this study intends to analyze the safety factor of the slope stability at places that will be crossed by geothermal pipelines. 2. material and methods 2.1. soil sampling soil samples were taken from five different points in ulubelu. furthermore, the locations of the sampling points are named bh-01, bh-02, bh-03, bh-04, and bh-05. bh is an extension of bore hole. the soil samples were then analyzed to find out the profile of the soil mechanics at the soil mechanics laboratory, faculty of engineering, university of lampung. soil mechanical parameters tested in the laboratory include: • water content (%) • density (gr/cm3) • specific gravity (gs) • passed sieve no. 200 (%) • atterberg limit tests ➢ liquid limits (ll) (%) ➢ plastic limits (pl) (%) lampung province tanggamus ulu belu 20 km n lampung gulf civil and environmental science journal vol. iii, no. 01, pp. 051-059, 2020 53 ➢ plasticity index (pi) (%) • consolidation tests ➢ cv (cm2/s) ➢ cc • triaxial tests ➢ cohesion (c) (kg / cm2) ➢ internal shifting angle (φ) (o) ➢ free compressive strength test (kg/cm2) 2.2. the analysis of slope stability an open ground surface that stands at a certain angle to the horizontal direction is called a slope without reinforcement. slopes can occur scientifically or man-made. if the ground is not horizontal, a component of gravity will tend to move the ground down. if the gravity component is large enough, a slope failure will occur, that is, when the mass of the landslides down. the launching force affects the resistance of shear strength along the surface of the collapse. civil engineers are often asked to make calculations to check the safety of natural slopes, excavated slopes, and embankment slopes. this check includes determining the shear strength that builds along the surface of the collapse and differentiating it from the shear strength of the soil. this process is called slope stability analysis. in determining the stability or instability of a slope, the term safety factor (f) is introduced. the value is a comparison between the forces that resist the movement and the forces that move the ground. interpretations of the value of safety factor are [2]: • f > 1.0: the slope is stable • f = 1.0: the slope is balanced, and ready for landslides • f < 1.0: slope is not stable in this research, the analysis of slope stability is conducted based on the philosophy of fellenius method, bowles method, and janbu method. all the works of stability analysis is undertaken using built-in computer programming called geostudio slope/w 2012. 2.3. fellenius method [3] this method is also called ordinary method of slice. the assumptions used in this method are: • field of landslides in a circle • the landslide field is divided into several upright slices • the width of each slice does not have to be the same • more suitable for soil that has values of c and  figure 2. forces acting on landslides for fellenius slope analysis method civil and environmental science journal vol. iii, no. 01, pp. 051-059, 2020 54 this simple method of slices assumes only the overall moment equation of equilibrium written with respect to the center of the slip surface. the shear and normal forces between blocks xi and ei are neglected. then sf is calculated directly from the following expression: (1) where: ui = pore pressure within block i ci,φi = effective values of soil parameters wi = block weight ni = normal force on the segment of the slip surface αi = inclination of the segment of the slip surface li = length of the segment of the slip surface 2.4. bishop method [4] the bishop method is a very popular method in slope stability analysis due to its simple and fast calculation. this method also provides a fairly thorough calculation of the safety factor. the bishop method calculates the force components (horizontal and vertical) by considering the moment balance of each piece. this method assumes zero xi forces between blocks. the method is based on satisfying the moment equation of equilibrium and the vertical force equation of equilibrium. the fs is found calculate a consecutive iteration as follows: (2) where: ui = pore pressure within block i ci,φi = effective values of soil parameters wi = block weight ni = normal force on the segment of the slip surface αi = inclination of the segment of the slip surface li = length of the segment of the slip surface figure 3. forces acting on landslides for bishop slope analysis method 𝐹𝑆 = 1 ∑ 𝑊𝑖 sin𝛼𝑖𝑖 ∑(𝑐𝑖𝑙𝑖 + (𝑁𝑖 − 𝑢𝑖𝑙𝑖)tan𝜑𝑖) 𝑖 𝐹𝑆 = 1 ∑ 𝑊𝑖 𝑠𝑖𝑛 𝛼𝑖𝑖 ∑ 𝑐𝑖𝑏𝑖 + (𝑊𝑖−𝑢𝑖𝑏𝑖)𝑡𝑎𝑛 𝜑𝑖 𝑐𝑜𝑠 𝛼𝑖 + [𝑡𝑎𝑛 𝜑𝑖 𝑠𝑖𝑛 𝛼𝑖]/𝐹𝑆 𝑖 civil and environmental science journal vol. iii, no. 01, pp. 051-059, 2020 55 2.5. janbu method [5] janbu is a soil slice method developed based on boundary balance. it takes a balance of power and satisfying moments that work on a particular block plane. sliced soil is made by dividing the soil on the slip surface as a plane. the forces acting on each slice can be seen in the following figure: figure 4. forces acting on landslides for janbu slope analysis method each slice block is assumed to contribute due to the following forces: wi = block weight, including material surcharge having the character of weight including the influence of the coefficient of vertical earthquake kv khwi = horizontal inertia force representing the effect of earthquake, kh is the factor of horizontal acceleration during earthquake ni = normal force on the slip surface ti = shear force on the slip surface ei ,ei+1 = forces exerted by neighboring blocks, they are inclined from horizontal plane by angle δi resp. δi+1 and lie at the height zi resp. zi+1 above slip surface fxi,fyi = other horizontal and vertical forces acting on block m1i = moment from forces fxi, fyi rotating about point m, which is the center of the ith segment of slip surface ui = pore pressure resultant on the ith segment of slip surface the janbu method takes several assumptions to calculate the balance of force and moment limits on individual blocks: • the divider between the blocks is always vertical • the wi block weight action line passes through the center of the slip surface segment which is represented by point m • the normal force ni works in the middle of the slip surface segment, at point m • the position of zi force ei acting between blocks is assumed, at the end point of the slip surface is z = 0 the determination of safety factor value is determined by employing the following iteration process: • the initial value of angles are set to zero δi = 0 and positions zi to approximately one third of interface height • the safety factor for a given value of δi follows from equation (5), while assuming the value of en+1 = 0 at the end of the slip surface (3) 𝐴 = [(𝑊𝑖 − 𝐹𝑦𝑖)cos𝛼1 − (𝐾ℎ𝑊𝑖 − 𝐹𝑥)sin𝛼𝑖 − 𝑈𝑖 + 𝐸𝑖 sin(𝛼𝑖 − 𝛿𝑖)] tan𝜑𝑖 𝐹𝑆 sin(𝛼𝑖 − 𝛿𝑖+1) tan𝜑𝑖 𝐹𝑆 + cos(𝛼𝑖 − 𝛿𝑖+1) civil and environmental science journal vol. iii, no. 01, pp. 051-059, 2020 56 (4) 𝐸𝑖+1 = 𝐴 + 𝐵 (5) • the value of δi is provided by equation (5) using the values of ei determined in the previous step. • the steps are then repeated until the value of fs does not change. unstable solutions have to be avoided for successful iteration process. such instabilities occur at points where the equation is division by zero, for example: 𝐹𝑆 = tan𝛼1 tan(𝛿𝑖+1 − 𝛼𝑖) (6) another check to avoid numerical instability is the verification of parameter mα: 𝑚𝛼 = cos𝛼1 sin𝛼1 tan𝜑𝑖 𝐹𝑆 > 0,2 (7) 2.6. geostudio geostudio is integrated software products for geotechnical modeling & analysis. this software has been developed in canada since 1977. geostudio has the ability to overcome planning problems related to strengthening soil structure such as deformation analysis and soil stability. in the analysis, the properties of structural components can be included in the stress deformation analysis so that the forces and moments in the structure can be calculated together with the interaction between the structure and the soil. stability analysis can also be carried out with all or part of structural load components that are assumed to be applied to the shear mass. structural components can be used or ignored to simulate actual field conditions. figure 4. graphical user interface (gui) of geostudio (slope/w) software 𝐵 = 𝑐𝑖 𝐹𝑆 𝑏𝑖 cos𝛼1 − (𝑊𝑖 − 𝐹𝑦𝑖) sin𝛼1 − (𝐾ℎ𝑊𝑖 − 𝐹𝑥)cos𝛼𝑖 −𝑈𝑖 + 𝐸𝑖 cos(𝛼𝑖 − 𝛿𝑖)] sin(𝛼𝑖 − 𝛿𝑖+1) tan𝜑𝑖 𝐹𝑆 + cos(𝛼𝑖 − 𝛿𝑖+1) civil and environmental science journal vol. iii, no. 01, pp. 051-059, 2020 57 slope/w is a component that is part of geostudio. the conventional limit equilibrium method is the basis for calculating slope stability analysis in the geostudio (slope/w) program. the limit equilibrium method is formulated in the form of moments and calculates the value of the safety factor from the moment equation balance. in this analysis, the safety factor is defined as the ratio of the shear resistance available to the one that needed for balance condition. the analysis of slope stability in this research uses fellenius, bishop, and janbu in the geostudio (slope/w) software. 3. results and discussions soil samples taken from the field are then brought to the laboratory to investigate the characteristics of soil mechanics through several tests. the results of the test are presented in the following table: table 1. the characteristics of soil mechanics of the samples bore hole depth water content (%) density (gr/cm3) specific gravity (gs) passed sieve no. 200 (%) liquid limits (ll) (%) plastic limits (pl) (%) bh-01 -5 m 43,53 1,465 2,471 68,65 65,17 46,39 -10 m 63,46 1,435 2,569 62,95 65,81 53,21 bh-02 -5 m 53,24 1,478 2,515 31,64 64,86 45,94 bh-03 -5 m 56,7 1,428 2,565 19,21 96,71 61,38 bh-04 -5 m 60,91 1,415 2,586 28,4 62,71 38,07 -15 m 45,55 1,547 2,529 35,8 56,02 32,16 bh-05 -5 m 74,62 1,469 2,585 61,02 106,79 68,83 -10 m 42,33 1,421 2,522 46,02 81,72 56,35 -15 m 32,62 1,527 2,5 70,05 59,88 35,26 table 2. the characteristics of soil mechanics of the samples (cont.) bore hole depth plasticity index (pi) (%) cv (cm2/s) cc cohesion (c) (kg/cm2) internal shifting angle (φ) (o) free comp. strength test (kg/cm2) bh-01 -5 m 18,78 0,07 0,204 0,13 11,8 0,4 -10 m 12,6 0,057 0,234 0,103 13,4 0,38 bh-02 -5 m 18,93 0,148 0,238 0,185 15,9 0,07 bh-03 -5 m 35,33 0,072 0,239 0,099 15,4 0,39 bh-04 -5 m 24,64 0,068 0,258 0,033 14,4 0,13 -15 m 23,86 0,108 0,2 0,092 13,5 0,25 bh-05 -5 m 37,96 0,083 0,301 0,05 20,7 0,36 -10 m 25,37 0,094 0,234 0,121 20,5 0,47 -15 m 24,62 0,089 0,213 0,184 19,4 0,53 then, using geostudio software, all samples from each location were analyzed with the final goal of finding the value of the slope safety factor of each location based on calculations from the fellenius method, the bishop method, and the janbu method. the results are: civil and environmental science journal vol. iii, no. 01, pp. 051-059, 2020 58 table 3. safety factor value for each bore hole based on calculations using the fellenius method, the bishop method, and the janbu method bore hole load variation safety factor value fellenius method bishop method janbu method bh-01 0 ton 2.017 2.185 2.020 5 tons 2.064 2.190 1.965 10 tons 2.020 2.189 1.964 15 tons 2.021 2.190 1.965 20 tons 2.020 2.190 1.965 bh-02 0 ton 3.987 4.357 4.168 5 tons 3.524 3.458 3.443 10 tons 2.599 3.335 1.857 15 tons 2.310 2.326 1.711 20 tons 2.245 2.015 2.056 bh-03 0 ton 3.711 3.873 3.702 5 tons 3.711 3.581 3.412 10 tons 3.418 3.579 3.411 15 tons 3.418 3.579 3.411 20 tons 3.259 3.419 3.251 bh-04 0 ton 2.028 2.093 2.386 5 tons 2.028 2.093 2.386 10 tons 2.000 2.035 2.007 15 tons 1.986 2.035 2.040 20 tons 1.947 1.862 1.749 bh-05 0 ton 2.126 2.232 2.034 5 tons 2.256 2.318 2.096 10 tons 1.948 2.042 1.936 15 tons 1.804 2.006 1.811 20 tons 1.822 1.882 1.748 the table shows that the safety factors for slope stability at the study locations are always > 1, which means that all the land at the location that is reviewed is safe from landslides. physically, it is known that the type of soil in the study area is soil that has layers that have moderate to good quality. in addition, the slopes reviewed are not too steep so the soil tends to be stable from landslides. the highest safety number value is achieved when the load = 0. load variations are added to the soil model analyzed by adding a load with a multiple of 5 tons. the calculation results also show that there is a decrease in the value of the safety factor along with the increase in burden. however, the decrease is not significant when compared to the value before being given a burden. this shows that the physical properties of the soil are quite uniform from the surface to a certain depth. the difference in computation among the fellenius method, the bishop method, and the janbu method does not produce too different safety factor values. this shows that all three models have the same accuracy in estimating landslide hazards. such statements are supported by several previous studies. research comparing the results of the calculation of the three methods with the results of the calculation of finite difference numerical method (fdm) shows a very close relationship between these results [6]. however, until now there has been no expert who states that one method is better than another method. one expert stated that each model has its own specificity in its use. for example, the bishop method is only good when used to analyze circular slip surfaces. on the other hand, janbu's method is best when used to analyze shallow and elongated slip surfaces and the fellenius method is good when used to analyze any type of slip surface. some others said that the however, most experts argue that the greatness of a method in analyzing slope slides depends on the type of slope and soil under investigation. civil and environmental science journal vol. iii, no. 01, pp. 051-059, 2020 59 4. conclussions slope stability analysis in ulubelu lampung for geothermal pipeline network development has been analyzed. three method of slope stability analysis: fellenius method, bishop method, and janbu method have been used to calculate safety factor of each sampling location. the calculation is undertaken using geostudio (slope/w) program. the characteristics of soil mechanics at the five studied locations indicate similarity. therefore, the values of the safety factors that are produced are also not much different from each other. the results also showed that the value of the safety factor produced was 1.8 to 4.3 which showed that all the land in all locations studied had sufficient security against landslides. however, from the three methods used to calculate the safety factor in this study, it can be concluded that the accuracy of each model is not much different. according to experts the superiority of a method in analyzing slope slides depends on the type of slope and the soil under investigation. acknowledgements the authors wish to convey their deep gratitude and appreciation to the civil engineering department, university of lampung for their support in this research. the authors also wish to thank to dr. gatot susilo who has assisted them in writing this paper. references [1] margrit, annisa, 2001. pembangkit listrik panas bumi: berkah ulubelu bagi masyarakat (in bahasa indonesia). website: https://banten.bisnis.com/read/20170620/451/664240/ pembangkit-listrik-panas-bumi-berkah-ulubelu-bagi-masyarakat [acessed feb 28, 2020]. [2] pangemanan m. g. v., turangan a.e and sompie o.b.a., 2014. analisis kestabilan lereng dengan metode fellenius (studi kasus: kawasan citraland). jurnal sipil statik, vol.2(1), pp. 37 – 46. [3] petterson k. e., 1955. the early history of circular sliding surfaces. geotechnique, vol(5), pp. 275-296. [4] bishop, a.w., 1955. the use of the slip circle in the stability analysis of slopes. geotechnique, vol. 5(1), pp. 7-17. [5] janbu, n. 1973. slope stability computations. embankment dam engineering casagrande volume, r.c. hirschfeld and s.j. poulos, eds., john wiley and sons, new york, pp 47-86. [6] mansour, z. s. and kalantari, b. 2011. traditional methods vs. finite difference method for computing safety factors of slope stability. electronic journal of geotechnical engineering, no. 16, pp. 1119 – 1130. open access proceedings journal of physics: conference series civil and environmental science journal vol. i, no. 01, pp. 012-018, 2018 12 application of artificial neural network for defining the water quality in the river riyanto haribowo1, very dermawan1, nevandria satrya yudha1 1water resources engineering department, universitas brawijaya, malang, 65145, indonesia riyanto_haribowo@ub.ac.id received 05-11-2017; revised 08-01-2018; accepted 26-02-2018 abstract. predicting point and nonpoint source runoff of dissolved and suspended materials into their receiving streams is important to protecting water quality. therefore, it is important to monitoring the condition of river water quality. the purpose of this study is to predict water quality in small streams using an artificial neural network (ann). the study focuses on small stream in tributary of brantas river. the variables of interest are dissolved oxygen (do), biochemical oxygen demand (bod), chemical oxygen demand (cod), ph and temperature (t). to validate the performance of the trained ann, it was applied to an unseen data set from a station in the region. the result show that the prediction of do is 6.03 mg/litre, ph is 6,47 mg/litre and temperature is 25.18°. with the relatively error was 15.63%, 12.64% and 14.12% respectively. it was finally concluded that ann models are capable of simulating the water quality parameters. keywords: artificial neural network, river, water quality, modelling 1. introduction rivers have received increasing amounts of attention due to their vicinity to large centres of population [6, 8]. therefore, it is necessary to have reliable information on characteristic of water quality for effective pollution control and water resource management, especially in arid regions [5, 4]. in an effort to handle this problem, it is necessary to conduct accurate and efficient water quality monitoring activities as a reference to make efforts to manage the quality of river water [1, 7]. therefore, the quality of river water can improve along with the increasing knowledge of human work more facilitated by the computer [3]. an artificial neural network (ann) is a computational method inspired by the studies of the brain and nervous system in biological organisms [9]. ann models have been used increasingly in various aspects of science and engineering because of its ability to model both linear and nonlinear systems without the need to make any assumptions as are implicit in most traditional statistical approaches [2]. the main aim of the present work is to construct an artificial neural network (ann) model of the surabaya river water quality. the do, bod, cod, ph and temperature of the river water were taken as the dependent variables here and set of other parameters constituted the independent variables. in this study, ann models have been identified for computing the do, bod, cod, ph and temperature of the river water. civil and environmental science journal vol. i, no. 01, pp. 012-018, 2018 13 2. material and methods the data set used in this study was generated through continuous monitoring of the water quality of surabaya river which is the tributary of brantas river, the biggest river in east java. this research was conducted on three water quality monitoring stations located in surabaya river, namely canggu tambangan station, perning bridge and jrebeng bridge. data of water quality parameter used is monthly data for 10 years (2006 -2015), and parameters used are do, bod, cod, ph and temperature. to calculate the discharge using monthly rainfall data for 10 years (2006-2015) from 3 nearest stations (kemlaten, krian, bakalan). field data for do, ph and temperature were analyzed with the help of water quality checker (horiba u-50) device. prediction analysis of water quality parameters by modeling the artificial neural networks using neurosolution 7.0 for excel. the ann network used for the present study is shown in figure 1. in the modeling analysis used three scenarios that will be explained in the next section. figure 1. structure of a multi-layer feed forward artificial neural network model the mathematical model of mass balance method can be used to determine the average concentration of downstream flow from point source and non-point sources pollutants (figure 2). figure 2. river flow scheme for mass balance analysis information: 1. river flow before mixing with pollutant sources 2. flow source stream a 3. flow source stream b 4. river flow after mixing with pollutant sources. output output layer hidden layer input layer intput civil and environmental science journal vol. i, no. 01, pp. 012-018, 2018 14 3. result and discussion 3.1. analysis of water quality using artificial neural networks (ann) in this study, the ann method will be applied to predict water quality parameters (do, bod, cod, ph and temperature) at jrebeng bridge point. at the prediction stage with ann method in this study will be made 3 (three) configuration. so it will be seen which configuration model has the best accuracy. the differences between the three scenarios lies in the input and desire variables. 3.1.1. discussion of configuration results 1 configuration i is conducted to predict parameters that can be measured directly in the field such as do, ph and temperature. this is carry out to determine the current condition of water quality at the downstream point with no need to measure the downstream, only with measurement data in upstream and centre of the river. after that, also tried to predict bod and cod only with input parameter of do, ph and temperature. from the results of ann analysis in configuration 1 shows good results for do, ph and temperature parameters. but at the output of bod and cod shows the re is still high namely above 10% (table 1). the lowest result in configuration 1 for do, ph and temperature set in the configuration with the output of each parameter, then set in the composition of the same dataset and epoch namely the dataset 60:20:20 and epoch 5000 with re do = 4.50%, ph = 0.99% and temperature =1.03%. table 1. relative error for configuration i with output for each parameter parameter epoch relative error (%) dataset composition 50%:30%:20% dataset composition 60%:20%:20% dataset composition 60%:30%:10% do 1,000 10.55 8.73 9.21 5,000 4.94 4.50 7.91 10,000 10.00 6.13 9.78 bod 1,000 30.10 32.95 41.72 5,000 33.42 30.90 30.92 10,000 30.30 40.34 36.18 cod 1,000 33.31 34.07 52.16 5,000 40.10 36.01 42.64 10,000 34.66 28.53 35.18 ph 1,000 1.15 1.17 1.29 5,000 1.15 0.99 1.35 10,000 1.44 1.12 1.20 t 1,000 1.32 1.43 1.38 5,000 1.49 1.03 1.26 10,000 1.50 1.30 1.48 3.1.2. discussion of configuration results ii configuration ii is conducted to predict water quality in the downstream with water quality parameters, in which the measurement can be done in the laboratory, with the requirement having the data of river water quality that will be measured on the upstream and downstream of the river. for instance, we will measure bod and cod, the requirements we must have bod and cod data on upstream and downstream and direct measurable supporting data such as do, ph, and temperature at 3 river sections ie upstream, middle and downstream. as well as required rainfall data from some nearby rain stations. civil and environmental science journal vol. i, no. 01, pp. 012-018, 2018 15 table 2. relative error for configuration ii with bod and cod output parameter epoch relative error (%) dataset composition 50%:30%:20% dataset composition 60%:20%:20% dataset composition 60%:30%:10% bod 1,000 20.44 17.58 20.48 5,000 18.49 15.59 16.15 10,000 17.43 24.66 22.38 cod 1,000 23.62 16.91 18.54 5,000 31.45 27.29 21.10 10,000 24.95 18.51 19.25 from the results of ann analysis in configuration ii shows the re is still above 10% (table 2). the lowest results in configuration 2 for bod and cod are in different epoch but still in the same data set composition ie 60:20:20. for bod located on epoch 5,000 with a re of 15.59% whereas cod located on epoch 1,000 with re 16.91% 3.1.3. discussion of configuration results iii configuration iii is performed to predict bod or cod parameters that cannot be measured directly in the field. analyzes were performed using input data that can be measured directly in the field such as do, ph and temperature. this was conducted to determine the current condition of bod and cod condition without need to bring water sample to the laboratory but only with input parameter do, ph and temperature, so it could save time and cost. here is an example of the best re configuration iii as shown in table 3. table 3. relative error configuration iii with bod and cod output parameter epoch relative error (%) dataset composition 50%:30%:20% dataset composition 60%:20%:20% dataset composition 60%:30%:10% bod 1,000 29.89 20.67 31.55 5,000 32.25 33.20 50.87 10,000 40.56 41.65 33.46 cod 1,000 30.58 32.68 26.85 5,000 38.06 28.62 28.25 10,000 27.57 31.55 36.43 from the analysis results seen in the 3rd configuration apparently, the smallest re is in the same epoch that is 1,000, but the results obtained is still better in the 2nd configuration, this is because in the 3rd configuration re is still above 20%. so, it can be concluded that the form of network architecture in the 2nd configuration can be used in bod and cod forecasting. after conducted 90 times process of ann analysis using neurosolution for excel then the analysis result of the model with the smallest re can be seen in table 4. civil and environmental science journal vol. i, no. 01, pp. 012-018, 2018 16 tabel 4. selection of the smallest relative error parameter smallest re epoch configuration dataset composition train : cros val : test re (%) do 5,000 1 60 % : 20% : 20% 4.50 bod 5,000 2 60 % : 20% : 20% 15.59 cod 1,000 2 60 % : 20% : 20% 16.91 ph 5,000 1 60 % : 20% : 20% 0.99 temperature 5,000 1 60 % : 20% : 20% 1.03 3.2. comparison between model results and actual data result of model and actual data analysis for do, ph and temperature parameter at smallest re located in the epoch and configuration as well as the same data set composition, namely epoch 5,000 configurations 1 and data set composition 60:20:20. comparison between model of analysis result and actual data for do, ph and temperature parameter can be seen in figure 3-8. the analysis shows that the model is already approaching the actual data, so it can be concluded that the model can be used to predict water quality condition. figure 3. comparison between do actual and model figure 4. distribution of do actual and model figure 5. comparison of ph actual and model figure 6. graph distribution of ph actual and model model actual civil and environmental science journal vol. i, no. 01, pp. 012-018, 2018 17 figure 7. comparison between temperature actual and model figure 8. graph of data distribution the output temperature of ann and actual temperature 3.3. water quality prediction for water quality prediction, the next conducted is to add the data of direct measurement results in the field which then put as input data and desired data using one of the running results of the parameter with the best output that has the smallest re %. from the analysis result, it is known that the prediction of do, ph and temperature conditions is 6.03 mg/litre, 6.47 and 25.18°c. meanwhile, the differences of the result between model and field data for do, ph and temperature respectively were 1.12, 0.73 and 4.14, with an average re of 14.14% (table 5). tabel 5. comparison of model and measurement data in the field point parameter value difference kr % model field jembatan jrebeng do (mg/litre) 6.03 7.15 1.12 15.63 ph 6.47 5.74 0.73 12.64 temperature (°c) 25.18 29.32 4.14 14.12 4. conclusions the smallest re value of do amounted 4.50%, ph 0.98% and temperature 1.0267% located in configuration 1 with target of each parameter using epoch 5,000 and dataset composition of training 60%, cross validation 20% and testing 20%. for the smallest re of bod 15.58% and cod 16.90% with configuration model 2, epoch 5,000, and dataset composition of training 60% cross validation 20% testing 20%. predicted result value for do parameter is 6.03 mg/litre and the field measurement value are 7.15 mg/litre has a difference of 1.12 mg/litre with a re of 15.63%. the predicted value of ann for ph amounted 6.46 and the field measurement value 5.74 has a difference of 0.73 with a re of 12.64%. the predicted value of ann for temperature amounted 25.18°c and the field measurement value 29.32°c has a difference of 4.14°c with a re of 14.12%. the analysis results show that with an average re rate of less than 15%, the ann model can be used to predict water quality conditions, which will make it easier to predict water quality conditions for better river management. suggestions for future research to use more data from multiple stations to obtain more accurate results and represent the overall river condition. references [1] boucher, m.a., perreault, l., anctil, f., 2009. tools for the assessment of hydrological ensemble forecasts obtained by neural networks. j. hydroinform. 11 (3e4), 297e307. [2] chang, y.-t., lin, j., shieh, j.-s., abbod, m.f., 2012. optimization the initial weights of artificial neural networks via genetic algorithm applied to hip bone fracture prediction. adv. fuzzy syst t e m p e ra tu re temperature actual actual model civil and environmental science journal vol. i, no. 01, pp. 012-018, 2018 18 9. [3] khalil, b., ouarda, t.b.m.j., st-hilaire, a., 2011. estimation of water quality characteristics at ungauged sites using artificial neural networks and canonical correlation analysis. j. hydrol. 405, 277e287. [4] kisi o., ay m., 2014. comparison of mann–kendall and innovative trend method for water quality parameters of the kizilirmak river, turkey j. hydrol., 513 (2014), pp. 362-375. [5] motaghian h.r., mohammadi j., 2011. spatial estimation of saturated hydraulic conductivity from terrain attributes using regression, kriging, and artificial neural networks pedosphere, 21 (2) (2011), pp. 170-177. [6] nilsson c., reidy c.a., dynesius m., revenga c., 2005. fragmentation and flow regulation of the world's large river systems. science, 308 (2005), pp. 405-408. [7] riyanto h, minami y, masahiko s, tsuyoshi i, koichi y, takaya h, ariyo k,. 2017. behavior of toxicity in river basins dominated by residential areas. contemporary engineering sciences, 10 (7)(2-13), pp. 305-315. [8] wang x.l., lu y.l., han j.y., he g.z., wang t.y., 2007. identification of anthropogenic influences on water quality of rivers in taihu watershed. j. environ. sci. (china), 19 (2007), pp. 475-481. [9] yegnanarayana, b. (1999). artificial neural networks. prentice-hall of india pvt. ltd., new delhi. open access proceedings journal of physics: conference series civil and environmental science journal vol. iii, no. 02, pp. 095-101, 2020 95 public perception of transportation systems in the halal logistics ita suhermin ingsih*, anita rahmawati civil engineering department, universitas islam malang, malang, 65144, indonesia ita.suhermin@gmail.com1 received 26-06-2020; accepted 10-08-2020 abstract. the need for halal products has now become a trend. not only struggling in food, but has grown in cosmetic, medicines and islamic financial services industry. a research from the pew research centre, states that until 2050, the world's muslim population is expected to grow by 75 percent. this can be interpreted that the level of need for halal products is also increasing. along with increasing public awareness of halal products, it is also necessary to treat halal in the logistics process. this research examines public perceptions regarding halal logistics, especially halal product transportation, and its variables are perceived by the community to be applied in halal logistics. the results of the study showed that more than 90% of respondents considered important variables needed in the implementation of halal logistics: mainly in sorting goods according to types as well as halal and non-halal, separating halal and non-halal products, setting the position of goods in cargo, using vehicles specifically for halal products, maintenance of cargo cleanliness, training of halal logistic officers, and health care for halal logistic officers. in addition, the use of halal logistic stickers can also provide halal logistic warranty from producers to consumers. keywords: perception, transportation, halal logistics 1. introduction one reason for the rise of the halal economy is that the global customer group of nearly two billion muslims are younger and, in some places at least, richer than ever [1]. a research from the pew research center, states that until 2050, the muslim population in the world is expected to grow by 75 percent. this figure is double the population growth in the world which is estimated at 35 percent [2]. demand from approximately 1.6 billion muslims throughout the world has become a crucial door-opener for halal industry [3]. indonesia is the highest halal market potential in the world due to indonesia's total population of 257.9 million and around 85% are muslim, which is around 12.5 percent of the population worldwide. however, not many industries in the country have looked at business opportunities with this halal standardization. in a muslim country such as indonesia, halal products have the potential power to foster customer loyalty [4]. the problem in indonesia with the halal market potential is currently still hitting the discourse. indonesia is still limited to awareness of not daring to act, whereas in non-muslim 1 cite this as: ingsih, i., & rahmawati, a. (2020). public perception of transportation systems in the halal logistics. civil and environmental science journal (civense), 3(2), 95-101. doi: https://doi.org/10.21776/ub.civense.2020.00302.4 civil and environmental science journal vol. iii, no. 02, pp. 095-101, 2020 96 countries many have implemented this halal supply chain. conditions like this if not addressed wisely will certainly make the indonesian people as spectators in their own country, especially in the competition of the asean economic community (aec). halal logistics is the process of controlling the material flow and information flow throughout the supply chain by following the halal standard [5]. the concept of halalan toyyiban has been introduced, where the concept starts from the farm until consumption. this means all the raw materials, material handling, storage, warehousing, and transportation should use the halal concept across the supply chain [6]. halal is extending towards logistics. this paper proposes a halal assurance system for transportation, warehousing and terminals as a proof of a halal logistics system [7]. the consumer opinion is necessary to measure, to develop a logistical standard and to conclude where the critical control points (ccps) of the halal food chain really are [8]. referring to malaysia's halal standard supply chain (halal supply chain), there are 3 (three) criteria for halal logistics standardization, namely: 1. goods transportation services; 2. warehousing activities; 3. sales [9]. based on the above matters, the author needs to know how the perception of a small population of consumers in indonesia, who are predominantly muslim, is about the halal logistics system in transportation variable and how high is the public's attention on the halal logistics system, especially in transportation of goods. 2. material and methods 2.1. location and time of study the study was conducted in october 2019 located in malang city, indonesia by taking a sample of the general public around the university of islam malang and surrounding involving students, employees, lecturers and the general public. 2.2. data collection the methods used in collecting data were interview and questionnaire. the selected respondents are workers with a minimum high school education level and conducted on 89 respondents. with getting data directly by questionnaire and interviews in spare time, will be obtained data which can be taken up by the respondent in answering existing questions. 2.3. data processing the data analysis used qualitative descriptive method. the analysis based on the results of closed questionnaire recapitulation, in which the respondent is directed to choose an answer that is in accordance with the respondent's perception. while the interview survey is open, so that respondents are expected to give their opinions freely in the form of narration. 3. result and discussion respondents who were the focus of this study were classified based on several types of characteristics, namely gender, education level, and respondent's occupation. sampling amounted to 89 respondents, which have various characteristics. for more details about the characteristics of the respondents will be presented in several diagrams below. 3.1. test validity and reliability of the questionnaire based on the results of the distribution of questionnaires to 89 respondents about the public perception of transportation for halal products, the following data were obtained. from the results of a closed questionnaire conducted on the general public, this questionnaire directed respondents to assess the level of importance of each variable, namely the first variable up to the nine variable symbolized by (x1 to x9). the importance level is in the form of very not important (value 1), less important (value 2), neutral (value 3), important (value 4), and very important (value 5). the above assessment is in addition to measuring the level of validity and the level of reliability of the questions contained in the questionnaire, also to determine public perceptions of what treatments need to be applied to the civil and environmental science journal vol. iii, no. 02, pp. 095-101, 2020 97 implementation of halal logistics transportation activities. testing the validity and reliability of the questionnaire aims to find out whether the contents or data of the question items are valid (valid) and reliable (reliable). if the data from the question items are valid and reliable, then the data can be used to measure the content of existing instruments. in table 1. the results of the validity test, obtained the value of the validity of variables x1 to variable x9 are above the value of r table (0.142), which varies between values 0.6 to 0.8. so it can be said that the variables contained in this questionnaire are valid. next is the reliability test using the cronbach alpha formula with reference to the standard alpha value [10]. cronbach alpha value obtained for public perception of halal logistics transportation is 0.85111, can be said to be very reliable because it is worth more than 0.8 and less than 1. 3.2. respondents characteristics this study was dominated by 62 male respondents (70%) and 27 female respondents (30%). based on the level of education that is senior high school graduates, bachelor, magister, and doctoral (figure 1). also was dominated by senior high school graduate respondents totaling 61 people (69%), then bachelor graduate respondents totaled 4 people (4%), magister graduates totaling 22 people (25%) and doctoral graduates totaling 2 people (2%) (figure 2). 3.3. discussion in this research, a perception of transportation services for halal products, the community gives a response about what they get and expect. analysis of this variable can be used as an illustration of the data instrument. the first step taken to analyse the data is by arranging them according to the number of statements for each variable. 1. the term supply chain or halal logistics supply chain (figure 3). 2. consumption of halal products (for example: food, cosmetics, medicines, clothes, etc.) (figure 4). 3. sorting items according to type (x1) (figure 5). 4. separation of halal and non-halal products in cargo (x2) (figure 6). 5. sorting of halal and non-halal products that have been damaged (x3) (figure 7). 6. positioning the placement of halal and non-halal goods in cargo vehicles (x4) (figure 8). 7. use of special vehicles in the delivery of halal products (x5) (figure 9). 8. cleanliness and avoid contamination between products in cargo vehicles (x6) (figure 10). 9. regularly training goods delivery personnel on halal logistics (x7) (figure 11). 10. special training for officers on how to treat halal products (x8) (figure 12). 11. health care for workers sending goods, especially officers shipping halal products (x9) (figure 13). while the results of the open questionnaire survey of several respondents have different perceptions related to halal logistics transportation in indonesia. some of these responses are: 1). some respondents, even the majority consider that the separation of halal products from non-halal products placed in separate containers is very important. this mean to avoiding (cross) contamination, avoiding mistakes, and ensuring that operations are consistent with the expectations of the muslim consumer [8][11]. the separation of halal and non-halal products in a different container or container is considered as a form of religious prudence and also a form of religious tolerance that needs to be maintained as well as possible. not only muslim consumers, but also non-muslim consumers. in general, various socioeconomic/demographic factors such as education level, older generation, those who are more religious and the urban dweller seem to more likely to be aware of the advantages of halal principles [12]. 2). the separation of halal and non-halal products is part of a different container or container is considered as a form of caution in religion and is also a form of religious collection that needs to be maintained properly. civil and environmental science journal vol. iii, no. 02, pp. 095-101, 2020 98 figure 1. characteristics of respondents by gender figure 2. characteristics of respondents based on the latest education level figure 3. the term supply chain or halal logistics supply chain figure 4. consumption of halal products figure 5. sorting items according to type figure 6. separation of halal and non-halal products in cargo figure 7. sorting of halal and non-halal products that have been damaged figure 8. positioning the placement of halal and non-halal goods in cargo vehicles civil and environmental science journal vol. iii, no. 02, pp. 095-101, 2020 99 figure 9. use of special vehicles in the delivery of halal products figure 10. cleanliness and avoid contamination between products in cargo vehicles figure 11. regularly training goods delivery personnel on halal logistics figure 12. special training for officers on how to treat halal products table 1. validity test results variabel r table validity x1 0.142 0.601959 ok x2 0.142 0.831832 ok x3 0.142 0.730957 ok x4 0.142 0.748228 ok x5 0.142 0.838175 ok x6 0.142 0.753449 ok x7 0.142 0.805823 ok x8 0.142 0.842556 ok x9 0.142 0.869852 ok 3). the importance of sorting products that have passed the end of their useful life (expired) and also products that are damaged or unsuitable for sale or consumption by consumers, which in turn will impact on the health of consumers. 4). shipping logistics both halal and non-halal products by train, to save on shipping costs and reduce the volume of vehicles on the highway. 5). at this time, the role of relevant stakeholders is only the type of goods listed in the manifest of goods entering or leaving the port. the owner of the goods, especially refer container, needs to sort out between halal and non-halal, given the consumption patterns in our country with a variety of religions and cultures. sometimes the goods owner can only mix between halal and non-halal to reduce shipping costs. so, expect education about halal logistics from upstream to downstream. 6). respondents hope that there will be cargo companies that implement the separation of halal and non-halal products. if there is no cargo company that is willing to share this halal product idea. it is better if there is a muslim entrepreneur initiative to pioneer cargo civil and environmental science journal vol. iii, no. 02, pp. 095-101, 2020 100 services that are willing to serve the separation of halal products. 7). there needs to be extensive socialization to the public so that the whole community is concerned about the halal logistics system, so that there will be direct supervision from the public if there are deviations in the implementation of logistics for halal products. 8). the current pattern of shipping goods is in accordance with the sop and the security is quite good, because every item to be sent is pre-packed/neatly wrapped from the factory or the owner of the goods so that the shipping officer at the port only repackages if there is damage. the shipping of goods has always been safe because the goods sent are solid goods/not raw goods so it does not cause risk of contamination. 9). there must be a clear and straightforward standard/sop in managing this matter, and the commitment of all stakeholders to implement it. if this logistics process can be run more efficiently, it is not impossible for indonesia to become a market leader in the business. in malaysia, the concept of halalan toyyiban has been introduced, where the concept starts from the farm until consumption. this means all the raw materials, material handling, storage, warehousing, and transportation should use the halal concept across the supply chain. there are even already a number of halal logistics service providers (lsp). there was only one lsp company that introduced this new concept in their operation, there is about nine companies certified with halal logistics certificate [6]. controlling 'halal' in logistics activities is monitoring halal performances in transportations activities that should comply with the shariah principle [13]. determining few risks in the transportation process of halal logistics are needed. there are few risk categories that lead to contamination risk of halal food products during the transportation, storage, and distribution process in halal food supply chain. delay risk, natural hazard, and operational risk are the category of risks that would affect the halal food products safety and quality and halal status during the transportation process. similarly, technology adoption risk and halal integrity risk are also important risk factors towards the process of risk categorization in halal food transportation and distribution process [14]. using technology also can be provided in transportation of halal logistics, for example ict (information communication technology). three important element that is considered an important step when deciding to adopt ict for halal transportation which are: a). assessing the halal transportation's requirement b). validating the need for technology specifically for halal transportation controls and c). assessing organizational capabilities or readiness activate halal transportation critical controls through ict assistance. technology related factors (ict compatibility with halal requirement) and halal assurance related factors are the most crucial factors among the halal lsps applying ict for halal control in transportation-s operation [15]. this is because transportation cannot be separated from information technology [16]. there is a need to develop proper guidelines, standards and codes, to train the halal logisticians. robust ict and its appropriate implementation seems as the backbone of the hsc (halal supply chain) [17]. ict technology can also be applied to agricultural products and fresh fish [18]. 4. conclusions more than 90% of respondents consider that variables 1 through 9 are important and very important in the implementation of the transportation system for halal products. the importance of using separate vehicles for the transportation of halal products and non-halal products. in the using same vehicle, it is necessary to place halal products in separate containers with non-halal products. in using same container, it is necessary to set the position or position separately and in such a way between halal and non-halal products. special training is needed for officers who will handle halal products in this halal logistics. such as vehicle cleaning that must be in accordance with the mahzab shafi'i (law), as well as other requirements because halal products are still maintained halal and obedience. halal logistics costs can be reduced by the use of vehicles and routes separate from general logical transportation. and also, the use of halal stickers can be used as a guarantee of halal (halal logistics warranty) for consumers. research on halal transportation is not only limited to perception, but can be developed to logistical service providers. another thing that can also be developed is knowing non-muslim perceptions of halal logistical services. civil and environmental science journal vol. iii, no. 02, pp. 095-101, 2020 101 references [1] m. asrofi, “halal logistics business potential in indonesia,” frost & sullivan market insight, 2011. [2] databoks, “https://databoks.katadata.co.id/datapublish/2017/01/31/penduduk-muslim-tumbuhtercepat-di-dunia,” 2017. https://databoks.katadata.co.id/datapublish/2017/01/31/pendudukmuslim-tumbuh-tercepat-di-dunia. [3] n. s. n. m. yunus, w. e. w. rashid, n. m. ariffin, and n. m. rashid, “muslim’s purchase intention towards non-muslim’s halal packaged food manufacturer,” procedia soc. behav. sci., 2014, doi: 10.1016/j.sbspro.2014.04.018. [4] i. masudin, f. w. fernanda, and widayat, “halal logistics performance and customer loyalty: from the literature review to a conceptual framework,” int. j. technol., 2018, doi: 10.14716/ijtech.v9i5.1919. [5] m. shahril ahmad razimi, a. rahim romle, and a. mohd rashid, “the halal concept on logistic islamic practices in malaysia,” eur. j. appl. sci., 2017, doi: 10.5829/idosi.ejas.2017.11.15. [6] n. f. roslan, f. a. rahman, f. ahmad, and n. i. ngadiman, “halal logistics certificate in malaysia: challenges and practices,” int. j. supply chain manag., 2016. [7] m. tieman and m. c. ghazali, “halal control activities and assurance activities in halal food logistics,” procedia soc. behav. sci., 2014, doi: 10.1016/j.sbspro.2014.01.1107. [8] r. bruil, “halal logistics and the impact of consumer perceptions,” master thesis r.r. bruil, 2010. [9] malaysian standard 2004-1:2010, halalan-toyyiban assurance pipeline part 1: management system requirements for transportation of goods and/or cargo chain services. malaysia, 2004. [10] t. p. budi, paradigma baru manajemen sumber daya manusia. yogyakarta: tugu publisher, 2005. [11] h. a. tarmizi, n. h. kamarulzaman, i. a. latiff, and a. a. rahman, “factors behind thirdparty logistics providers readiness towards halal logistics,” int. j. supply chain manag., 2014. [12] v. n. mathew, a. m. r. binti a. abdullah, and s. n. binti m. ismail, “acceptance on halal food among non-muslim consumers,” procedia soc. behav. sci., 2014, doi: 10.1016/j.sbspro.2014.01.1127. [13] n. w. r. shah, a. muhammad, s. mohamad, and h. s. jaafar, “halal transportation providers for supply chain management in halal industry: a review,” j. hosp. networks, 2016. [14] t. z. yaacob, f. a. rahman, and h. s. jaafar, “risk categories in halal food transportation: a preliminary findings,” int. j. supply chain manag., 2018. [15] m. i. i. tan, r. n. razali, m. i. desa, and z. j. m. husny, “information communication technology adoption process for malaysia halal transportation,” in lecture notes in engineering and computer science, 2014. [16] qurtubi and e. kusrini, “research in halal logistics and halal supply chain: issue and area development,” in matec web of conferences, 2018, doi: 10.1051/matecconf/201815401096. [17] a. haleem and m. i. khan, “towards successful adoption of halal logistics and its implications for the stakeholders,” br. food j., 2017, doi: 10.1108/bfj-12-2016-0637. [18] t. g. amran, “design of cold chain third-party logistics (3pl) for halal food in indonesia,” proceeding 8 th int. semin. ind. eng. manag., 1978. open access proceedings journal of physics: conference series civil and environmental science journal vol. i, no. 01, pp. 001-011, 2018 1 application of polynomial rocking bearings as seismic isolation system on irregular bridges krisna febrian anugerahputra1, lee tzu ying2, ari wibowo1 1 civil engineering department, engineering faculty, universitas brawijaya, malang, 65145, indonesia 2 civil engineering department, engineering faculty, national central university, taoyuan city, 32001, taiwan krisfebrian9132@gmail.com received 18-11-2017; revised 18-01-2018; accepted 14-02-2018 abstract. friction pendulum system (fps) is one of the conventional sliding isolators which widely used and effectively proved to reduce seismic hazard in far-fault earthquakes. however, it may not be effective when the structures are induced by near-fault earthquakes because the earthquake’s period is usually close to the isolation period. in this study, a polynomial rocking bearing (prb) which has variable isolation stiffness is used to improve the performance of seismic isolation systems applied on irregular bridges under near-fault earthquakes. the prb is composed by an articular joint and concave rocking surface. the rocking surface is defined by a sixth-order polynomial function. based on previous studies, the prb has been verified to effectively suppress the large isolator displacement subjected to near-fault earthquakes on building and regular bridges. however, it has not been used yet in the irregular bridges. this study aims to analyze the behaviour of polynomial rocking bearing installed on an irregular bridge. as compared with friction pendulum systems (fps), the performance of prbs is much better to effectively suppress the displacement of the bridge deck in both near and far-fault earthquakes. keywords: irregular bridges, near-fault earthquakes, polynomial rocking bearing, variable isolation stiffness. 1. introduction bridges are one of the most vital components in the transportation system. design of bridges are based on its function, ground condition, material construction, and the available funds. no matter what kinds of bridges will be constructed, they must be able to carry any loads especially seismic loading to provide safety and comfort for users. in the past extreme earthquakes, a number of bridges suffered serious damage. once bridges failure or collapse, it will impede recovery and rehabilitation. to protect bridges from seismic damage, bridges should be designed based on the bridge seismic design codes. a modern technique of mitigating seismic damage is called structural control. structural control can be classified into three, passive, active, and semi-active control. more than 20 years, most of the previous researchers use passive control, especially base isolation systems or seismic isolation systems [1, 2, 3, 4, 6, 9]. civil and environmental science journal vol. i, no. 01, pp. 001-011, 2018 2 seismic isolation systems are usually placed between structure and foundation on buildings. the main concept of this technology is to increase the fundamental period of structures and/or dissipate the seismic energy transmitted directly onto the structure systems [10]. seismic isolators can be divided into two groups, namely, sliding bearings and elastomeric bearings [5, 7, 11]. friction pendulum system (fps) is commonly-used sliding bearings. previous research has shown that the fps has good isolation effect when structures are subjected to far-fault earthquakes. however, it may result in an excessive isolator displacement under near-fault earthquakes. to overcome this problem, some researchers suggested the isolation systems with variable mechanical properties, which may be adaptive to a wider range of earthquakes. polynomial rocking bearings (prbs) proposed by lu et al. [8] has variable mechanical properties. in the previous study, polynomial rocking bearing has applied on the building by lu er at [8] and also applied to the regular bridge (bridge with the same heights of the column). based on both previous researches, polynomial rocking bearing (prbs) is able to effectively suppress the large isolator displacement induced by strong near-fault earthquake. bridges structure may be irregular in column heights due to complex terrain, route alignment, ramps, interchanges, and so on. in this study, prbs are installed between the deck and the column of the irregular bridge. this research is aimed to analyze the behaviour of polynomial rocking bearing installed on an irregular bridge subjected to the seismic loading. the optimum parameters of prbs are found out using pso-sa hybrid searching algorithm. lastly, the seismic performances of the irregular bridge with prbs and fps are compared to verify the superiority of prbs. 2. material and methods 2.1. configuration of prbs polynomial rocking bearing (prb) is an axially symmetric rocking surface with variable curvature. it has an articular (ball and socket) joint on the upper part and a concave rocking surface with a base plate on the lower part [8]. the articular joint is mounted on the footing of the superstructure, while the base plate is mounted on the foundation [8]. when the earthquake occurred, the rocking surface of the bearing will rock back and forth on the base plate, thus provide an isolation layer to reduce the ground motion transmitted into the super-structure. prb is one of the seismic isolation systems. it can mitigate the seismic load transmitted onto the structure, so the structural systems and their facilities inside will be safe. based on figure 1, prb has three design parameters: height of bearing (h), the radius of the spherical head (r), and the geometrical function of rocking surface y = g(x). in this study, the sixth-order polynomial function is chosen to make the bearing with variable stiffness. g(x)=c1x 6+c2x 4+c3x 6 (1). figure 1. polynomial rocking bearings installed under bridge’s deck. upper plate socket base base plate spherical head rocking surface deck column y-g(x) civil and environmental science journal vol. i, no. 01, pp. 001-011, 2018 3 2.2. horizontal restoring force of prb besides the configuration, the mechanical properties of an isolator are also important things. before discussing mechanical properties, for simplicity, some assumptions will be made. first, rocking surface and base plate of bearing should have a point contact anytime. second, the friction coefficient between them should be large enough to prevent slippage. third, the inertial moment due to the rocking motion is negligible as compared to the forces applied to the bearing. at last, the radius of curvature should be larger than height to retain stability. based on figure 2, there are two coordinate systems on this isolator, x-y and x-y. the x-y is a fixed coordinate system which x-axis attached to the ground. the x-y is moving coordinate system of prb attached to bearing and will rock along the bearing. therefore, when the bearing is on its origin position, both of the coordinate systems coincides each other. however, when the systems are rocking, there will be a rotation angle between x-y and x-y that denoted by θa. since it assumed that the rocking surface of prb has a point contact with ground, so the x-axis is tangent to the contact point a. tan 𝜃𝑎 = sin 𝜃𝑎 cos 𝜃𝑎 = 𝐺 ′(𝑋𝑎) , − 𝜋 2 ≤ 𝜃𝑎 ≤ 𝜋 2 (2) θa denotes rotation angle, while xa denotes moving coordinate for contact point. other parameters are four forces that work on the isolator. w is the structural weight, u is the horizontal resultant forces, n is the normal forces at contact point a, and f is the friction forces at contact point a. w and u are actually the forces that occur between superstructure and the bearing. moreover, the force u as horizontal resultant forces transmitted onto isolated structure is an important parameter. the force u is defined by taking the moment equilibrium at contact point a and written as follows: ∑ 𝐹𝑥 = 0 → 𝑈 = 𝐹 (3) ∑ 𝐹𝑦 = 0 → 𝑊 = 𝑁 (4) ∑ 𝑀𝐴 = 0 → 𝑈 = 𝑢𝑟 = 𝑊(𝑥𝑎−𝑥𝑏) 𝑦𝑏 (5) w denotes structural weight, u denotes horizontal resultant forces, n and f represents normal forces and friction forces at contact point a, respectively, ur denotes bearing restoring force, xa denotes x coordinate of the contact point a in the x-y coordinates, while xb and yb are x and y coordinates of the point b, respectively. figure 2. free body diagram of polynomial rocking bearings since it assumed that friction coefficient between the rocking surface and base plate should be large enough to prevent slippage, so xa should be equal to the arc length (sa) between a and centre axis of moving coordinate system. fixed coord moving coord civil and environmental science journal vol. i, no. 01, pp. 001-011, 2018 4 𝑥𝑎 = 𝑆𝑎 = ∫ √1 + 𝐺 ′(𝑋𝑎) 2𝑑𝑋 𝑋𝑎 0 (6) using the coordinate transformation relation between x-y and x-y systems, the value of xb and yb can be determined as: 𝑥𝑏 = (ℎ − 𝐺(𝑋𝑎 )) sin 𝜃𝑎 − 𝑋𝑎 cos 𝜃𝑎 + 𝑥𝑎 (7) 𝑦𝑏 = (ℎ − 𝐺(𝑋𝑎 )) cos 𝜃𝑎 + 𝑋𝑎 sin 𝜃𝑎 (8) refer to equation 2, with eliminating variable θa, the value of xb and yb can be determined in another form. 𝑥𝑏 = 𝑆𝑎 + −𝑋𝑎+(ℎ−𝐺(𝑋𝑎))𝐺 ′(𝑋𝑎) √1+𝐺′(𝑋𝑎) 2 (9) 𝑦𝑏 = 𝑋𝑎𝐺 ′(𝑋𝑎)+(ℎ−𝐺(𝑋𝑎)) √1+𝐺′(𝑋𝑎) 2 (10) from the equations above, variables xa, xb, and yb are depend on variable xa which represents the x coordinate of the contact point a. refer to equation 5, equation 6, equation 9, and equation 10, the existence of restoring force ur can be shown as: 𝑢𝑟 = 𝑢𝑟 (𝑋𝑎 ) = 𝑊[−(ℎ−𝐺(𝑋𝑎))𝐺 ′(𝑋𝑎)+𝑋𝑎] (ℎ−𝐺(𝑋𝑎))+𝑋𝑎𝐺 ′(𝑋𝑎) (11) thus, to express the restoring force u_r of polynomial rocking bearing, it should be defined first about the geometric function of polynomial rocking bearing. 2.3. horizontal friction force of prb since the spherical head of polynomial rocking bearing has the friction effect, it will provide the energy dissipation of the bearing. so, when the friction is considered, the behavior of spherical head will change like the figure 3. this figure represents the resultant friction force and resultant normal force with the symbol f and n, respectively. for the resultant normal force, because it measured from the vertical axis, so there will be an angle ϕ. note that the force n and f are perpendiculars each other. for the convenience, the force system in the figure 3a is slightly replaced by the equivalent calculation of force system in the figure 3b, in which w and u are the equivalents vertical and horizontal force components. the force w and u are interactive forces between the structure and bearing, so it should be affected by the structural weight and dynamic response. furthermore, in the figure 3b, the equivalent couple moment produce by friction force f to point b can be expressed as: 𝑀𝑓 = 𝑟𝐹 (12) mf denotes moment produce by f. figure 3. equivalent force systems at spherical head of prbs civil and environmental science journal vol. i, no. 01, pp. 001-011, 2018 5 from the figure 3, it is assumed that the bearing has a positive displacement and its rocking outward (the articular joint moving away from the neutral position). if the bearing has the opposite direction, so the directions of f and mf should be reversed. figure 4. model of target bridges generally, the directions of f and mf should be determined by the rocking direction of the bearing, once it moving outward or inward. horizontal force u is consisting of restoring force and friction force. 𝑈 = 𝑢𝑟 + 𝑢𝑓 (13) 𝑢𝑟 = 𝑊𝑒 𝑦𝑏 = 𝑊(𝑥𝑎−𝑥𝑏) 𝑦𝑏 (14) 𝑢𝑓 = 𝑀𝑓 𝑦𝑏 = 𝑟𝐹 𝑦𝑏 (15) 2.4. analysis model and method 2.4.1. design of target bridge the bridge is designed based on the japan highway bridge design codes. as shown in the figure 4, the bridges consist of the three-span deck with two abutments and two different heights of columns. the detail parameters are shown in the table 1. this study is based on single span bridge deck with a different height of the column. the following assumption is considered to simplify the analysis. first, the soil condition along the bridge is uniform. second, the vertical ground motion characteristics of the structure are not considered. third, the friction coefficient of the bearing is constant. lastly, the maximum static friction coefficient is equal to its dynamic friction coefficient. 2.4.2. equation of motion derivation from the free body diagram as shown in the figure 5, the bridge’s system will divide into two parts, upper part and lower part. the upper part is a bridge’s deck, and the lower part is bridge’s column. 𝑚𝑑 �̈�𝑑 = −(𝑈1 + 𝑈2) − 𝑚𝑑 �̈�g (16) 𝑚𝑐1�̈�𝑐1 + 𝑐𝑐1�̇�𝑐1 + 𝑘𝑐1𝑥𝑐1 = 𝑈1 − 𝑚𝑐1�̈�g (17) 𝑚𝑐2�̈�𝑐2 + 𝑐𝑐2�̇�𝑐2 + 𝑘𝑐2𝑥𝑐2 = 𝑈2 − 𝑚𝑐2�̈�g (18) generally, the equation of motion can be obtained as: mẍ(𝑡) + cẋ(𝑡) + kx(𝑡) = ml1�̈�g(𝑡) + l2u(𝑡) (19) m, c, and k denote the mass, damping, and stiffness matrices. l1 and l2 are the seismic force distribution vector and the total horizontal force distribution matrix, respectively. �̈�g(𝑡) is the ground excitation, x(t) is structure civil and environmental science journal vol. i, no. 01, pp. 001-011, 2018 6 displacement vector, while u(t) is total horizontal force vector that contains restoring force (ur) and friction force (uf). table 1. parameter of irregular bridges the equation 19 is rewritten as the state space equation of motion as follows: ż(𝑡) = az(𝑡) + e�̈�g(𝑡) + bu(𝑡) (20) equation 20 is a continuous-time system. it will be converted into a discrete-time system using external linear interpolation as follows: z[𝑘 + 1] = adz[𝑘] + e0�̈�g[𝑘] + e1�̈�g[𝑘 + 1] + b0u[k] + b1u[𝑘 + 1] (21) z[k] represents the system state (contains the system velocity and displacement) and can be shown as: z[𝑘 + 1] = [ ẋ[𝑘 + 1] x[𝑘 + 1] ] (22) in equation 21, ad denotes the discrete-time system matrix which contains the mass, damping, and stiffness of structure. b and e are the discrete-time matrices for the horizontal force of prb and ground excitation, respectively. k is the kth step and (k+1) is the (kth+1) step, δt is the time step. figure 5. free body diagram of irregular bridges 2.4.3. horizontal friction force of prb the component ur that represents the restoring force can be determined by the bearing geometric parameters as shown in the previous chapter. because the physical properties of the prbs are complex, then the behavior of prbs must be obtained by two coordinate systems, namely fixed coordinate system mass of bridge's deck 2038.8 ton short column mass of column 37.1 ton stiffness of column 124400 kn/m long column mass of column 74.2 ton stiffness of column 15740 kn/m civil and environmental science journal vol. i, no. 01, pp. 001-011, 2018 7 (x-y) and moving coordinate system (x-y). as describe in second chapter, the value of xa, xb(xa), yb(xa), xa(xa) are obtained by coordinate transformation systems. in this study, the bisection method is selected as the numerical solver to find xa and others parameters. unlike the restoring force (ur), the friction force (uf) cannot be easily expressed as an explicit function of the system response, because the friction forces have two possible states, namely sticking state and rocking state. furthermore, because the bridge model has different height for each column, it may cause the friction force has one another possible state, namely partial rocking state. thus, in this case, the friction force totally has three possible states: sticking state (all bearing is sticking), rocking state (all bearing is rocking), and partial rocking state (partial bearing is sticking while partial bearing is rocking). when the moment of the bearing (mf) is less than the maximum moment (mf,max), it is called the sticking state. on the other hand, when the moment (mf) is equal or more than the maximum moment (mf,max), it will be in rocking state. for the detail, analysis process will be shown in the figure 10. moment of the bearing and the maximum moment can be shown as: �̅�𝑓 [𝑘 + 1] = �̅�𝑓 [𝑘 + 1]𝑦𝑏 [𝑘 + 1] (23) 𝑀𝑓,𝑚𝑎𝑥 = 𝑊𝜇𝑟𝛽(𝑋𝑎 ) (24) 𝛽(𝑋𝑎 ) is a modification factor to the friction coefficient. a. sticking state |�̅�𝑓 [𝑘 + 1]| < 𝑀𝑓,𝑚𝑎𝑥 (25) b. rocking state |�̅�𝑓 [𝑘 + 1]| ≥ 𝑀𝑓,𝑚𝑎𝑥 (26) c. partial rocking state this state means at the same time, both of bearings may have different state, one is sticking state and the other is rocking state. because the restoring force (ur) can be defined easily by the bearing geometric parameters, so for this condition just need to concern for the friction force (uf). when one of the bearings is in the sticking state, so equation 25 can be considered. and for another bearing is in the rocking state, so using equation 26. 3. result and discussion 3.1. ground motion input to investigate the isolation performance of prb system on the irregular bridges, two types of horizontal ground motions with different characteristics, recorded from real earthquakes, were considered as the excitations in the simulation. totally two ground motions are choosing to simulate the behavior of irregular bridge. for the near-fault earthquake, the 1994 northridge earthquake is used. to represent the far-fault earthquake, the 1940 el centro earthquake is used. 3.2. numerical results and discussions in this study, pso-sa hybrid searching algorithm based on particle swarm optimization and simulated annealing is adopted to explore the optimal parameters of the prb isolation system. prbs have three key design parameters: the geometric function y=g(x), the bearing height (h), and the radius of the spherical head (r). thus, by properly choosing the value of these parameters, the mechanical properties of the prbs may get the desired specifications. overall for the deck displacement, prb has better isolation effect than fps. based on the numerical results, some figures about the structure’s responses are not satisfactory, such as the hysteretic loop of the bearing. for example, is the hysteretic loop of prb in northridge earthquake. theoretically, in the short column case, the displacement of prb in short column should be larger than longer column, because short column’s stiffness is larger than longer column, so the stiffness of the bearing should be smaller than in longer bearing. however, the results show that displacement of prb in short column is smaller than prb in long column. it means that the stiffness of prb in short column is larger than prb civil and environmental science journal vol. i, no. 01, pp. 001-011, 2018 8 in long column. this phenomenon is also occurred in the long column case. it may happened because in this research using two different analysis for the seismic isolation system and the bridge structure. non-linear analysis is performed in the seismic isolation system while linear analysis is in the bridge structure. nevertheless, generally, the performance of prb isolation system is better than fps because it can effectively suppress the deck displacement in near and far-fault earthquakes. figure 6. time history of prb and fps under northridge earthquake civil and environmental science journal vol. i, no. 01, pp. 001-011, 2018 9 figure 7. time history of prb and fps under el centro earthquake figure 8. hysteretic loop of prb and fps under northridge earthquake civil and environmental science journal vol. i, no. 01, pp. 001-011, 2018 10 figure 9. hysteretic loop of prb and fps under el centro earthquake figure 10. analysis process civil and environmental science journal vol. i, no. 01, pp. 001-011, 2018 11 4. conclusions the pso-sa hybrid searching method is used to find out the optimal design parameters of the prb and fps. observed from the analytical results, the pso-sa can obtain effective isolation effect of the prb and fps bearing parameters. however, some structural responses are not satisfactory because in this research two different analysis for the seismic isolation system and for the bridge structure are used. non-linear analysis is used in the seismic isolation system and linear analysis is in the bridge structure. but, compared with the fps, generally prb can effectively suppress the deck displacement under both near and far-fault earthquakes. for the future research, it is suggested to consider the non-linear behavior of bridges, namely, non-linear analysis to achieve more realistic results for the structure response. references [1] asher, j. w., hoskere, s. n., ewing, r. d., van volkinburg, d. r., mayes, r. l., and button, m. (1995). seismic performance of the base isolated usc university hospital in the 1994 northridge earthquake. asme-publications-pvp, 319, 147-154. [2] bozorgnia, y., mahin, s. a., and brady, a. g. (1998). vertical response of twelve structures recorded during the northridge earthquake. earthquake spectra, 14(3), 411-432. [3] çelebi, m. (1996). successful performance of a base isolated hospital building during the 17 january 1994 northridge earthquake. the structural design of tall and special buildings, 5(2), 95-109. [4] fujita, t. (1998). seismic isolation of civil buildings in japan. progress in structural engineering and materials, 1(3), 295-300. [5] kelly, j. m. (1986). aseismic base isolation: review and bibliography. soil dynamics and earthquake engineering, 5(4), 202-216. [6] kelly, j. m. (1998). seismic isolation of civil buildings in the usa. progress in structural engineering and materials, 1(3), 279-285. [7] koh, c. g., and kelly, j. m. (1988). a simple mechanical model for elastomeric bearings used in base isolation. international journal of mechanical sciences, 30(12), 933-943. [8] lu, l. y., and hsu, c. c. (2013). experimental study of variable-frequency rocking bearings for near-fault seismic isolation. engineering structures, 46, 116-129. [9] martelli, a., and forni, m. (1998).seismic isolation of civil buildings in europe. progress in structural engineering and materials, 1(3), 286-294. [10] matsagar, v. a., and jangid, r. s. (2006).seismic response of simply supported base-isolated bridge with different isolators. international journal of applied science and engineering, 4(1), 53-69. [11] naeim, f., and kelly, j. m. (1999). design of seismic isolated structures: from theory to practice. john wiley & sons. civil and environmental science journal vol. iii, no. 02, pp. 102-109, 2020 102 management and arrangement model of loloan river area for conservation and development as a tourist attraction area i gusti agung putu eryani1*, cok agung yujana1, i wayan wesna astara2 1 faculty of engineering and planning, warmadewa university, denpasar, 80239, indonesia 2 faculty of law, warmadewa university, denpasar, 80239, indonesia eryaniagung@gmail.com1 received 26-08-2020; accepted 07-09-2020 abstract. among the massive areas in the city of denpasar that have changed land functions, there are still some areas that are still preserved with their natural landscapes. one of them is the loloan river area. this area is currently planned to be developed as an area of natural tourist attraction in urban areas. this research aims to make a management and arrangement model of the loloan river area optimize the development of renon village around the loloan river area as a tourist attraction area without lay aside the sustainability of the surrounding environment. the research method used in this study uses descriptive qualitative research methods to create a management and arrangement model that is appropriate to the research location. the result of management and arrangement model of the loloan river area that can be done in several ways, including empowering the society in efforts to clean up sediment in the loloan river basin so that the river's capacity can be optimal, educating the society about the importance of conserving irrigation channels for sustainable water potential and arrangements in the loloan river area which can be done by planting around the loloan river area. keywords: water potential, management, conservation. 1. introduction the river as a water resource has benefits and an important role in human life. nowadays, rivers flowing in densely populated residential areas show a tendency to worsen from year to year. increasing economic development activities, land-use change, and increasing population growth have resulted in high pressure from river areas to the environment [1]. bali province, which is a tourism destination, requires a lot of supporting facilities to complement tourism supporting facilities and infrastructure, such as hotels, restaurants, villas, and increased housing development. currently, the land around the river area in bali province has changed its function, especially agricultural lands in urban areas that have been converted into buildings that support tourism 1 cite this as: eryani, i.g.a.p., yujana, c.a., & astara, i.w.w.a. (2020). management and arrangement model of loloan river area for conservation and development as a tourist attraction area. civil and environmental science journal (civense), 3(2), 102-109. doi: https://doi.org/10.21776/ub.civense.2020.00302.5 civil and environmental science journal vol. iii, no. 02, pp. 102-109, 2020 103 activities. as the capital city of bali province, denpasar city is one of the cities in bali that is experiencing a rapid land conversion [2]. according to land use, most of the land area in denpasar city is used for non-agricultural lands such as roads, settlements, offices, and others. the area of irrigated rice fields decreased from year to year from 2013 to 2017. from 2016 2017, irrigated rice fields decreased by 35 hectares. the conversion of agricultural land, both paddy fields, and non-rice fields is used for non-agricultural lands such as yards, settlements, roads, and others [3]. land use changed to have an impact on the amount of erosion in the upstream to downstream areas of the river and the discharge of residential waste into the river that resulting in river pollution. this can lead to silting of water bodies, drought in the dry season, and flooding in the rainy season [4]. among the massive areas in the city of denpasar that have changed land functions, there are still some areas that are still preserved with their natural landscapes. one of them is the loloan river area around the traditional village of renon. this area is currently planned to be developed as an area of natural tourist attraction in urban areas. however, the current condition is not yet supportive to become a tourist area due to the inadequate management and arrangement of the loloan river area. if it is not managed and arranged properly, its development as a tourist attraction area can cause problems such as land conversion, pollution and so on. therefore, a management and arrangement model of loloan river area is needed to optimize the development of renon village around the loloan river area as a tourist attraction area without lay aside the sustainability of the surrounding environment. 2. material and methods 2.1. research location this research took place in the loloan river area (figure 1), around the renon village. this location was taken because this area is under development as a tourist attraction area for renon village. figure 1. research location 2.2. research tools and materials the research tools used in this study were a camera, interview sheets, and a laptop. besides, it is supported by the google earth pro, drones, and microsoft office. google earth pro is used to obtain imagery at the study site for 2015-2019, then drones are used to take existing aerial images. after that, the data obtained were processed using microsoft office. the types of data used in this study are primary data and secondary data. primary data is in the form of data collection obtained through observation , interviews, and focus group discussions (fgd). secondary data is data obtained from the literature study method from books, journals, magazines, and the internet regarding the research location. the collected data will be used for research and useful for making management and arrangement model of the loloan river area in denpasar city. civil and environmental science journal vol. iii, no. 02, pp. 102-109, 2020 104 2.3. data analysis technique the research method used descriptive qualitative research methods to create a management and structuring model that is appropriate to the research location. this study begins by analyzing the potential that can be developed as a tourist attraction and problems in the research location through direct observation and interviews, after knowing the potential and problems that occur, a management and arrangement model of the loloan river area is made as an effort to conserve and develop the loloan river area as an area of tourist attraction. with the management and arrangement model of the loloan river area, it is hoped that it can optimize the development of renon village around the loloan river area as a tourist attraction area. 3. result and discussion 3.1. loloan river area loloan river is one of the watersheds that flow in the denpasar city with a river length of 3.75 km and irrigates 103 hectares of rice fields [3]. characteristics of the loloan river have a very flat riverbed slope (0.0032 in the upstream, 0.0032 in the midstream and 0.0025 in the downstream), a narrow river width (average 4.4 m in the upstream, 4.5 m in the midstream part and 9 m downstream) [5]. this situation causes a slow sediment rate that allows flooding if the sediment in the water body is not managed properly [6] [7] [8]. coupled with changes in the function of land in the area around the river so that the management and arrangement of the river are needed to conserve the sustainability of the water potential of the area. figure 2. land conversion in loloan river area based on aerial images from google earth for 2015-2019 (figure 2), from 2015 to 2016 there was a land-use change in the area around the study site into built-up land, while from 2017 to 2018 there was no significant change, and in 2019 there was a reduction in green land around research sites. if this area is not managed and arranged properly, this will have an impact on the potential for increased flow coefficient which can increase the potential for flooding during the rainy season and the potential for drought in the dry season. civil and environmental science journal vol. iii, no. 02, pp. 102-109, 2020 105 3.2. tourism potential of the loloan river area according to the big indonesian dictionary (kbbi), the potential is the ability, strength, and power that can be developed. tourism potential is everything that is found in a tourist destination and is an attraction for people to come to visit these places [9]. based on law no. 10 of 2009, the notion of tourist attraction is anything that has uniqueness, beauty, and value in the form of a diversity of natural, cultural, and man-made wealth that is the target or purpose of tourist visits [10]. according to the tourism law, tourist attraction is one of the efforts in tourism. tourism business which includes: • tourist area • transportation services and travel services • food and beverage services • providing accommodation for entertainment and recreation activities • organizing meetings, intensity trips, conferences and exhibitions • tourism information services, tourism consulting and guide • water and spa tours broadly speaking, the tourist attraction is classified into three classifications [11]. • natural tourist attraction sourced from existing natural conditions such as beach tourism, marine, mountainous nature, remote wild areas, parks, and conservation areas. • cultural appeal having objects that come from the socio-cultural conditions of the community or legacy such as conditions of community customs, social conditions of the community, and traditional events. • man-made attraction attractiveness that develops something that is human-made or is included as a special attraction, such as folk amusement parks, music festivals, annual festivals, or competition locations (boats, motor cross, etc.). loloan river is one of the locations that has tourism potential in the form of nature tourism. around the river area, there is a stretch of rice fields that are still natural, the flow of water from the loloan river and the existence of the renon traditional village office area whose area has been paved so that it can be used as a jogging track area or other relaxing recreation. the location is also easy to reach and has adequate road facilities so that it is not difficult for tourists who want to have a recreation there. the existence of the loloan river also adds to the attraction of this place to be used as a tourist area. in general, city people are rarely able to see natural conditions due to dense settlements, but this location can be used to be able to carry out natural recreation to relieve the fatigue of urban society as shown in the figure 3. figure 3. potential tourism attractions of the loloan river area 3.3. loloan river area problems the loloan river is located in the village of renon which borders the sanur area which has the potential to become a tourist attraction area. however, the current condition is not yet favorable to be used as a tourist area due to the inadequate management of water potential and the arrangement of the loloan river area. several problems still occur in the loloan river area, including: civil and environmental science journal vol. iii, no. 02, pp. 102-109, 2020 106 • the existing condition of the irrigation technical channel is still experiencing several problems, such as: in some locations, there are technical channels that are damaged and cause loss of potential water in the channel, there are weeds that grow in water bodies so that the river reservoir does not function as planned as shown in the figure 4. figure 4. damage in river revetment and river silting • lack of society awareness of the importance of conserving the loloan river which can cause various problems as shown in the figure 5. figure 5. pollution in rivers due to lack of society awareness • the arrangement and conservation around the loloan river area are still not optimal as shown in the figure 6. figure 6. environmental conditions around the loloan river civil and environmental science journal vol. iii, no. 02, pp. 102-109, 2020 107 3.4. management and arrangement model of loloan river area according to kotler [12], swot analysis (strength, weakness, opportunity, threat) is an overall evaluation of strengths, weaknesses, opportunities, and threats. the benefit of a swot analysis is to increase the knowledge and understanding of the organization so that it can analyze what are the strengths, weaknesses, opportunities, and threats in the organization to get the right strategy by using existing strengths and opportunities to overcome all threats and reduce existing weaknesses so that the organization can survive and be able to thrive. according to riadi [13], swot analysis has a function to obtain information from situation analysis and separate it into internal issues (strengths and weaknesses) and external issues (opportunities and threats). from the existing problems and potentials, a swot model for the management and arrangement of the loloan river area is made as follows. table 1. swot model for the management and arrangement of the loloan river area strength (s) weakness (w) opportunity (o) threat (t) • has a potential tourist attraction • there is still a problem of pollution due to garbage in the loloan river • can be developed as a tourist attraction • river pollution which if not managed can damage the environment of the loloan river • easy to reach, close to the city center • lack of arrangement of the area around the loloan river and damaged river embankments • the strategic location with the trajectory of the tour makes it easy to promote the area as a tourist attraction • there is a possibility of flooding due to silting thus reducing the potential for existing tourist attractions • the environment is still natural and there have not been many changes in land use • there is still a lack of awareness and education of the surrounding society about the conservation of the area around the loloan river • its location in the urban area is perfect for city people who are tired of routines and want simple tours that are easy to reach • starting from changes in land use, namely changes in paddy fields into settlements • the role of traditional villages and communities that are active in its development • there is still a lack of promotion by traditional village administrators regarding the potential for tourist attractions around the loloan river area • it is easy to promote because it already has a unique characteristic, namely the baris cina dance, so that it can be developed with various tourist facilities, such as museums or cultural exhibitions. • there is an internal conflict from the indigenous village community if it has been developed as a tourist attraction area related to the impact of tourism facilities that support the development of the area based on table 1, several management strategies and arrangements of the loloan river area can be formulated as follows. civil and environmental science journal vol. iii, no. 02, pp. 102-109, 2020 108 • empowerment of the surrounding society and related stakeholders in the form of cooperation in efforts to clean the sedimentation in the loloan river area so that the river's capacity can be optimal. this strategy can be carried out by holding cooperation to clean the water body of the loloan river by involving the participation of the society and related stakeholders to clean the loloan river, whose existing conditions are still overgrown with weeds and plants and installing garbage catcher nets to prevent silting due to waste in water bodies. • educate about the importance of conserving irrigation channels so that the water potential of the loloan river can be used optimally. with this education, it is hoped that the surrounding society will understand the importance of conserving the loloan river area to reduce the negative impacts that can occur due to changes in land use and the habits of the surrounding society which can cause pollution and damage to the loloan river area. • planning for arrangement and conservation of the loloan river area. this can be done by planting appropriate crops according to climatic conditions and the needs of the surrounding society, as well as repairing river embankments to reduce water loss in water bodies that cause drought and sedimentation of water bodies. • promoting the tourist attraction of the loloan river area to increase the interest of the surrounding society to visit the area, so that it can be developed as a tourist attraction area that might improve the economic level of the surrounding area. • make strict rules regarding the behavior of the surrounding society for not to pollute the loloan river, and make a river care community to increase society awareness of the importance of conserving the loloan river area. based on this model, it can be seen that the loloan river area has the potential to be developed as a tourist attraction area, its location in the city center makes this location easy to reach, and the natural scenery of rice fields and rivers around the location. this area also can be used as a simple recreation area for the surrounding society who want to eliminate boredom due to work and the stress of life in the city. but before this location is further developed as a tourist attraction area, there is a need for management in the loloan river area, especially regarding the problem of waste pollution and damage to river embankments. after the management is carried out, support is needed from the side of the arrangement of the area, so that this area becomes sustainable, planting plants around the loloan river is very necessary, and it is not impossible to add lighting if it is open for the night. 4. conclusions based on the explanation above, it can be concluded that several things are as follows. 1. the loloan river is one of the rivers that flow in denpasar city. the loloan river located in renon village has a tourist attraction as a natural tourism attraction. the view of the rice fields that are still maintained, the flow of water from the loloan river, and the paved location provide facilities for the surrounding society to do jogging and nature recreation in urban areas. however, the current condition is not yet favorable to be used as a tourist area due to the inadequate management and the arrangement of the loloan river area. 2. to optimize the development of the loloan river area as an area of tourist attraction, it can be done by empowering the surrounding society in the form of cooperation in efforts to clean up weeds in the loloan river basin so that the river's capacity can be optimal, socializing the importance of conserving irrigation channels for potential loloan river water can be used optimally as well as planning the arrangement and conservation of the loloan river watershed. this can be done by planting appropriate crops according to climatic conditions and the needs of the surrounding society, as well as repairing river embankments to reduce water loss in water bodies that cause drought and sedimentation of water bodies. civil and environmental science journal vol. iii, no. 02, pp. 102-109, 2020 109 acknowledgments acknowledgments submitted to the warmadewa university and community of the traditional village of renon who have supported the completion of this paper. references [1] d. widodo, b. lupiyanto, r., dan wijaya, “pengelolaan kawasan sungai code berbasis masyarakat,” j. sains dan teknol. lingkung., vol. 2, no. 1, 2010. [2] g. p. d. s. pratiwi and i. p. a. citra, “dinamika dan kesesuaian arahan fungsi kawasan di kota denpasar,” j. pendidik. geogr. undiksha, vol. 7, no. 1, 2019, doi: 10.23887/jjpg.v7i1.20674. [3] pemerintah kota denpasar, “rencana kerja pemerintah daerah semesta berencana 2020,” denpasar, 2020. [online]. available: https://bappeda.denpasarkota.go.id/new/public/ckfinder/userfiles/files/rkpd 2020.pdf. [4] i. g. a. p. eryani, “potensi air dan metode pengelolaan sumber daya air di daerah aliran sungai sowan perancak kabupaten jembrana,” paduraksa, vol. 3, no. 1, pp. 32–41, 2014. [5] cv. permata denpasar, “review masterplan drainase kota denpasar,” denpasar, 2016. [online]. available: http://sippa.ciptakarya.pu.go.id/sippa_online/ws_file/dokumen_usulan/drainase/drainase _51-71-2016.pdf. [6] s. a. nelson, “river systems & causes of flooding,” tulane university, 2016. https://www.tulane.edu/~sanelson/natural_disasters/riversystems.htm. [7] d. indriastuti, “analysis of runoff due to the change in land use at the watershed of upstream ciliwung,” j. civ. eng. forum, vol. 2, no. 1, p. 131, 2016, doi: 10.22146/jcef.26576. [8] delwp, guidelines for development in flood affected areas, no. february. 2019. [9] o. a. yoeti, pengantar ilmu pariwisata. bandung: angkasa, 1996. [10] kementerian pariwisata republik indonesia, undang-undang republik indonesia nomor 10 tahun 2009. indonesia, 2009. [11] h. marpaung and h. bahar, pengantar pariwisata. bandung: alfabeta, 2002. [12] p. kotler, marketing management. jakarta: prenhallindo, 2000. [13] m. riadi, “strength weakness opportunities threats (swot),” kajianpustaka.com, 2013. http://www.kajianpustaka.com (accessed aug. 04, 2019). open access proceedings journal of physics: conference series civil and environmental science journal vol. iii, no. 02, pp. 119-125, 2020 119 the investigation of avalanche patterns on railroad tracks with steep slopes lusmeilia afriani* and iswan civil engineering department, universitas lampung, bandar lampung, 35145, indonesia lusmeilia.afriani@yahoo.com1 received 12-08-2020; accepted 28-09-2020 abstract. this study aims to investigate the pattern of landslides on the cliffs forming the railway with steep slopes. this research was conducted at rejosari natar station, south lampung regency, lampung province. the point of observation is at sta 30 + 250. the data in this study were divided into primary and secondary data. primary data is the data that is directly obtained in the field by taking soil samples which are then processed in the laboratory. the secondary data is the soil characteristics data of the railroad structure starting from the rail load, rail bearings, ballast layers, sub-ballast layers, and sub-grade. these will be used as input in conducting railroad analysis using plaxis modelling. plaxis modeling requires these variables and parameters to be analyzed based on the amount of vertical settlement, total stress, and safety factor values that occur due to rail loads. reserach found that the value of the soil safety factor was <1.25. this means that the soil condition is in a critical condition for collapse and the ground will experience landslides which can endanger the safety of the passing trains. for this reason, improvements are needed in the soil that will experience landslides. keywords: avalance, pattern, railroad, track 1. introduction train is a vehicle or means of transportation that can transport goods and people in large quantities. a train consists of a locomotive as the driving force and carriages as a place to transport people or goods. the carriages are stretched lengthwise and pulled by the locomotive to move. trains run on specific roads which are called rails. throughout the world, trains are used as a means of transporting goods or human transportation. mass human transportation by rail means dealing with the transportation of large numbers of people from one city to another. for freight transport, trains can be a long series involving more than 50 cars. the longest train in the world is the kansas city southern de mexico with a length of 5166 m. this train is operated between united states and mexico [1]. the longest train in the world for passenger is in australia (the ghan) with a length of about 1696 m with a maximum series of 44 cars [2]. other countries with the largest number of carriages and the longest trains are canada, the united states, the united kingdom and china. in indonesia, the transportation 1 cite this as: afriani, l. & iswan. (2020). the investigation of avalanche patterns on railroad tracks with steep slopes. civil and environmental science journal (civense), 3(2), 119-125. doi: https://doi.org/10.21776/ub.civense.2020.00302.7 civil and environmental science journal vol. iii, no. 02, pp. 119-125, 2020 120 of goods and people using trains is organized by pt. kereta api indonesia, a government-owned company appointed to manage rail transport services in indonesia [3]. the length of railroads in indonesia is 6,790 km. of that number, only two thirds are active and still in use. railroads in indonesia are spread across java as much as 71% and in sumatra as much as 29%. by 2030, the government targets to increase the length of the railroad so that its length is twice the length of the current rail. the plan for this long train network will be spread across the islands of java, bali, sumatra, kalimantan, sulawesi and papua [4]. increasing the length of railways to twofold by 2030 inevitably requires expertise to better organize and maintain this infrastructure to ensure the smooth operation of railways. due to its operation, railroads that are used as roads for trains will experience quality degradation in some of their components [5][6] including in railroad structures such as fractures in rail weld joints, damage to rail fasteners, wear on rails and cracks in concrete bearings. the dominant incidence of train accidents in indonesia is the collapse of the carriages caused by the spread of cracks in rail fractures, cracks in concrete pads, loose fastening of rails, failure of railroad structures, land subsidence, and human error. one of the most dominant causes of accidents is cracks in concrete bearings. the cracks in the concrete bearings are caused by the concrete bearings that are not able to withstand the loads given by the railroad cars, causing cracks on various sides of the concrete bearings. cracked concrete bearings can also occur due to land subsidence due to decreased soil bearing capacity due to non-standard soil compaction. in addition, the railroad structure on sloping ground contours can trigger landslides and cause fractures to concrete bearings, rails and damage to the railroad structure. this study aims to investigate the pattern of landslides on the cliffs forming the railway with steep slopes. this research was conducted at rejosari natar station, south lampung regency, lampung province. the point of observation is at sta 30 + 250. the laboratory work is carried out at the laboratory of soil mechanics, university of lampung. the visualization of the collapse of the cliffs forming the railroad will be carried out with the help of the plaxis method. 2. research methodology 2.1. study location this research was conducted at rejosari natar station at the observation point of sta 30 + 250. rejosari station is a train station located in natar district, south lampung regency. the distance is approximately 19 km from tanjung karang central station, lampung. rejosari station is a class ii train station located at an altitude of +104 meters above sea level. administratively, this station is under regional division iv tanjungkarang. figure 1. study location civil and environmental science journal vol. iii, no. 02, pp. 119-125, 2020 121 this station has four railway lines with line 3 being a straight line plus eight special lines in the workshop area. at this station, there is a coal train maintenance workshop that sends coal from the bukit asam coal mine, south sumatra province, to the tarahan power plant in lampung province. this coal carrier train is the longest train in indonesia, which is approximately 600 m long with a maximum series of 50 carriages. this train is capable of making 50 trips from bukit asam to tarahan every day and supplies several hydropower plants in java island apart from plta tarahan in lampung province. 2.2. data and research procedures the data in this study were divided into primary and secondary data. primary data is data that is directly obtained in the field by taking soil samples which are then processed in the laboratory. meanwhile, secondary data is data obtained from the results of previous research which can be accounted for its accuracy. primary data obtained from this study is the data on the characteristics of landfills [7] which are the results of tests at the laboratory of soil mechanics, university of lampung. these data are: • water content (%) • specific gravity (%) • sieve analysis (%) • atterberg limit (%) • max. dry density (%) • cbr soaked and unsoaked (%) the secondary data is the soil characteristics data of the railroad structure starting from the rail load, rail bearings, ballast layers, sub-ballast layers, and sub-grade layer [8]. the characteristics of the railroad include the modulus of soil elasticity (e), subgrade modulus (ks), poisson ratio, soil permeability, soil cohesion and soil shear angle. these characteristics will be used as input in conducting railroad analysis using plaxis. 3. result and discussion plaxis modeling requires variables and parameters to be analyzed based on the amount of vertical settlement, total stress, and safety factor values that occur due to rail loads. the following are the figure 2. cross section in the location of study civil and environmental science journal vol. iii, no. 02, pp. 119-125, 2020 122 characteristics of the primary data and the parameters that will be used in the plaxis program input in the form of cross sections and tables. table 1. original soil characteristics data from the field (primary data) no. description unit value 1. water content (%) 12.3 2. specific gravity (%) 2.562 3. sieve analysis (%) 36.82 4. atterberg limit (%) ll = 37.92, pl = 25.33, ip = 12.59 5. max. dry density (gr/cm3) 1.531 6. opt. moisture content (%) 23.70 7. cbr soaked and unsoaked (%) soaked = 13.60 unoaked = 7.33 figure 3. force distribution in the cross section studied figure 4. figure network of deformed elements in the unsaturated condition of the railroad structure which is located at sta 30 + 250 civil and environmental science journal vol. iii, no. 02, pp. 119-125, 2020 123 table 2. input data for plaxis analysis (secondary data) zone parameter symbol value unit centralized load 96.4322 kn concrete rail bearing elastic axial stiffness ea 6,963,854.9 kn/m flexural ridigity ei 141.4812 kn.m2/m weight w 0.2246 kn/m/m poisson ratio v 0.2 ballast fill weight above the phreatic level 𝛾𝑢𝑛𝑠𝑎𝑡 20 kn/m 3 fill weight below the phreatic level 𝛾𝑠𝑎𝑡 22 kn/m 3 permeability in the hor. direction kx 0.0011574 m/day permeability in the vertical direction ky 0.0011574 m/day modulus young e 24,500 kn/m2 poisson ratio v 0.4 sliding angel ∅ (phi) 40 o angel of dilation 𝜑 (psi) 10 o sub-ballast fill weight above the phreatic level 𝛾𝑢𝑛𝑠𝑎𝑡 18 kn/m 3 fill weight below the phreatic level 𝛾𝑠𝑎𝑡 20 kn/m 3 permeability in the hor. direction kx 0.000011574 m/day permeability in the vertical direction ky 0.000011574 m/day modulus young e 12,250 kn/m2 poisson ratio v 0.15 sliding angel ∅ (phi) 35 o angel of dilation 𝜑 (psi) 5 o landfill fill weight above the phreatic level 𝛾𝑢𝑛𝑠𝑎𝑡 18 kn/m 3 fill weight below the phreatic level 𝛾𝑠𝑎𝑡 20 kn/m 3 permeability in the hor. direction kx 1.1574e-09 m/day permeability in the vertical direction ky 1.1574e-09 m/day modulus young e 14,241.2 kn/m2 poisson ratio v 0.3 sliding angel ∅ (phi) 25 o angel of dilation 𝜑 (psi) 0 o original soil fill weight above the phreatic level 𝛾𝑢𝑛𝑠𝑎𝑡 18 kn/m 3 fill weight below the phreatic level 𝛾𝑠𝑎𝑡 20 kn/m 3 permeability in the horizontal direction kx 1.1574e-09 m/day permeability in the vertical direction ky 1.1574e-09 m/day modulus young e 13,430.7 kn/m2 poisson ratio v 0.3 sliding angel ∅ (phi) 25 o angel of dilation 𝜑 (psi) 0 o civil and environmental science journal vol. iii, no. 02, pp. 119-125, 2020 124 figure 4 is a display of the results of the deformed element network in the unsaturated condition of the railroad structure which is located at sta 30 + 250. the red grid color is the element distribution that occurs after a stretching analysis of the element density due to the effect of sloping soil displacement on the embankment soil. there was a change in the shape of the sloping soil position on the right side of the embankment in the conditions after analysis, on the sloping part of the embankment there was a temporary settlement. in the cross section of sta 30 + 250 there is a deformation of 1.25 m. the greater the deformation value, the greater the likelihood of landslides due to soil deformation occurring on sloping land, both vertically and horizontally. the amount of deformation is influenced by the magnitude of the slope angle of the embankment soil and the height of the soil slope itself. the illustration of total soil displacement shows the effect of two directions of soil displacement, both horizontally and vertically. there are two directions of arrows that move vertically and horizontally. soil displacement that occurs is indicated by the largest arrow and the direction as shown. the total soil extreme displacement value at sta 30 + 125 is 1.25.103. the total soil displacement is obtained at 1.25 m. figure 5. total soil displacement due to landslides figure 6. effective stress illustration civil and environmental science journal vol. iii, no. 02, pp. 119-125, 2020 125 the illustration of the effective stress shows the amount of effective earth stress that occurs at the cross section of sta 30 + 250. effective stress affects shear strength and changes in volume or soil subsidence that occurs on sloping soil. the deeper the soil, the greater the effective soil stress that occurs. this is indicated by the red density element. the denser the elements, the greater the effective soil stress that occurs. in this condition, the maximum effective stress value is -156.97 kn / m2. the negative sign at the maximum value indicates the pressure on the soil particles. the greater the value of the effective soil stress that occurs, the better the condition of the soil particles in providing bearing capacity for sloping soil landslides on the landfill. from the calculation results, the unsaturated sloping soil conditions studied had a safe factor (fk) value of 1.19, or were in a critical condition (fk <1.25) for collapsed. therefore, retaining walls for supporting soil must be installed on steep soils so that the safety factor value reaches a value of more than 1.25 and the construction is safe against landslides. 4. conclussion in overall, in the analysis for sta 30 + 250, it was found that the value of the soil safety factor was <1.25. this means that the soil condition is in a critical condition for collapse. this situation states that the ground will experience landslides which can endanger the safety of the passing trains. for this reason, improvements are needed in the soil that will experience landslides such as the installation of retaining walls, flat sheet piles, steel sheet piles and soil geometric changes on steep slopes. 5. acknowledgements the authors would like to thank deeply to the civil engineering department of lampung university and to the students and technicians for their support in the lab and field tests for completing of this paper. references [1] wikipedia, 2020, longest train. website: https://en.wikipedia.org/wiki/longest_trains [acessed sep 27, 2020]. [2] henly, s.g. 2020. 3 days on board the ghan train. website: https://www.australia.com/en/trips-and-itineraries/adelaide-and-surrounds/3-days-on-boardthe-ghan-train.html [acessed sep 27, 2020]. [3] pt. kereta api indonesia (kai), sejarah perkeretaapian. website: https://kai.id/corporate/about_kai/ [acessed sep 27, 2020]. [4] pt. sarana multi infrastruktur (smi), 2014. smi’s insight -triwulan i 2014. website: https://www.ptsmi.co.id/ wp-content/uploads/2015/10/ smis_insight_triwulan_i_2014_ kereta _api.pdf [acessed sep 9, 2020]. [5] elkhoury, n., hitihamillage, l., moridpour, s. and robert. d. 2018. degradation prediction of rail tracks: a review of the existing literature. the open transportation journal, vol. 12: 88-104 [6] soleimanmeigouni, i., ahmadi, a.and kumar. u., 2016. track geometry degradation and maintenance modelling: a review. proceedings of the institution of mechanical engineers, part f: journal of rail and rapid transit. [7] afriani, l. soil shear strength, jakarta: graha ilmu publisher; 2014. [8] hendriyana, 2013. seputar kereta api. website: https://hendriyana90.wordpress.com/konstruksi-rel-kereta-api/ [acessed sep 27, 2020]. https://en.wikipedia.org/wiki/longest_trains https://www.australia.com/en/trips-and-itineraries/adelaide-and-surrounds/3-days-on-board-the-ghan-train.html https://www.australia.com/en/trips-and-itineraries/adelaide-and-surrounds/3-days-on-board-the-ghan-train.html https://kai.id/corporate/about_kai/ https://hendriyana90.wordpress.com/konstruksi-rel-kereta-api/ open access proceedings journal of physics: conference series civil and environmental science journal vol. iii, no. 02, pp. 110-118, 2020 110 design of hazardous waste station in xyz port, jakarta city andhika yoga wibisono, disfiatri kusumaningtyas, salman farid lahmadi, alfiyah najwa, hafiz arie rachmantoro, ariyanti sarwono, i wayan koko suryawan* department of environmental engineering, faculty of infrastructure planning, universitas pertamina, jakarta, 12220, indonesia i.suryawan@universitaspertamina.ac.id1 received 29-08-2020; accepted 24-09-2020 abstract. the design of hazardous waste station is intended to adjust the security in the xyz port area based on the fire and leakage possibility of hazardous waste generation. the research method used primary and secondary data to determine the availability of land area, and solid waste generation including its characteristics, respectively. the design of hazardous waste station was initiated with field observations to measure the land availability, and followed by secondary data collection to identify the volume, characteristics, and dimensions of hazardous waste collection. the composition of hazardous wastes, based on the solid waste characteristics, was flammable (20%), flammable and toxic (56%), toxic (23%), and corrosive (1%). the result suggested that the recommended dimension of the hazardous waste station was 11m x 8 m. the container dimensions for leakage prevention were 2 m x 2 m x 0.6 m with a freeboard of 0.3 m. the fire extinguisher was within a range of 12 m. keywords: hazardous waste station, design, port area 1. introduction port is the main gateway for a country to carry out economic activities. port is not only meant for passenger services but is also meant for a traffic lane of goods’ export-import. indonesia ranks sixth after hong kong, singapore, the republic of korea, malaysia, and the united emirates arab in terms of container port’s traffic levels [1]. the increasing market demand will also increase operational activities in the xyz port area of jakarta. heavy equipment in the terminal is routinely used, which results in regular maintenance. maintenance activities of heavy equipment produce hazardous and toxic waste in the form of oil, cables, and other hazardous goods that piled together. liquid materials such as used oil are very likely to leak and be scattered, creating the risk of fire. according to the international labour organization (i.l.o), the fire requirements can occur and enlarge due to several fuels or flammable substances, the existence of a lighters source, and the amount of oxygen in the air to support combustion [2]. from the three fire conditions, flammable material is always in the hazardous waste station, while oxygen is always in free air, only a lighter which has not 1 cite this as: wibisono, a.y., kusumaningtyas, d., lahmadi, s.f., najwa, a., rachmantoro, h.a., sarwono, a & suryawan, i.w.k. (2020). design of hazardous waste station in xyz port, jakarta city. civil and environmental science journal (civense), 3(2), 110-118. doi: https://doi.org/10.21776/ub.civense.2020.00302.6 civil and environmental science journal vol. iii, no. 02, pp. 110-118, 2020 111 met the occurrence of a fire, but the existence of a lighter source in the hazardous waste station area is very possible, among others: short circuit possibility from an electrical device, many vehicles passed by allowing road users to dispose cigarette butts [3]. if hazardous waste is not managed properly, it will impact on all living things and natural environments on this earth [4]. details are regulated by the law starting from the source of waste, storage, transportation, and destruction. hazardous waste management is important, if intentionally mixing hazardous waste without knowing their individual characteristics, unforeseen events will potentially occur, such as sudden burning and exploding. there are several aspects of burning such as fire extinguishers, direct sunlight, and hazardous waste mixing that is not based on its characteristics but it is recommended for one concept to only be filled with 1 type of hazardous waste. based on the government regulation no.101 of 2014 [5], the area of waste station must accommodate hazardous waste generated routinely (/day, /week, /month, etc.). each hazardous waste package must be symbolized and labeled, to identify if there is hazardous waste in the area otherwise it will endanger workers when they misuse the hazardous waste. for container design, the volume of the container is designed by multiplying the volume of each hazardous liquid waste by 110%. based on sni 03-6572-2001 regulations for ventilation design of storage/warehouse (category seven [6], it requires ventilation with an area of at least 10% of the floor area and ventilation height of no more than 3.6meters from the floor. the arrangement of fire extinguishers, based on nfpa 13 of 2013 [7], the placement of fire extinguishers must be arranged with the height of the top (head) of the fire extinguisher about 1.2 meters from the floor surface. the location of fire extinguishers is also regulated based on nfpa 10 of 2013 [7]. the location of fire extinguishers is as far as 23 meters from a potentially flammable sources and metal source of fire extinguishers is needed if the characteristics of the hazardous waste produced are flammable, thus, when a minor fire occurs, it can be immediately overcome because the provision of fire extinguishers is readily accessible and the placement of fire extinguishers is located properly [8]. in making symbols and labels, it must be installed on the package (drums) of hazardous waste as a sign of hazardous waste and it must label their respective characteristics. the symbol size used is 15 x15 cm, whereas the label size used is 25 x 40 cm according to kep05 / bapedal/09/1995 [9]. providing a waste transfer station, in accordance with the regulations of the minister of environment and forestry no. p.12 2020 [10] concerning the storage of hazardous and toxic waste materials, can prevent the risk of environmental impacts, especially from fires. in addition, the company will achieve a good rating from an auditor. the purpose of this work is to design a hazardous waste station to be safe from the risk of fire by taking the composition of the waste. 2. material and methods 2.1. field observation field observations were conducted to examine the capacity of the land. measurements were carried out in areas that are safe from disturbance and have no potential of causing environmental impacts. 2.2. generation and composition hazardous waste generation data was obtained from the logbook inventory at xyz port for three months. the composition of hazardous waste was differentiated based on its characteristics, which are flammable and corrosive. the generation and composition data were obtained from secondary data. 2.3. design solid waste volume is calculated based on solid waste generation and multiplied by a safety factor of 30%. the frame of the waste bin often experiences fluctuating loads from hazardous waste loads therefore, dynamic loads was anticipated [11]. the equation used is in accordance with equation 1. volume of waste = waste generation x 30% (1) civil and environmental science journal vol. iii, no. 02, pp. 110-118, 2020 112 from field observation, the estimation volume of waste spills can be calculated based on equation 2. the placement between fire extinguishers is adjusted to permenaker no. 04/ men/1980 [12]. the range of fire extinguishers is designed 15 meters from the placement. volume wastewater = volume solid waste x ∑ drum (2) 3. result and discussion 3.1. hazardous waste generation and composition based on the secondary data on the volume of hazardous waste generated, the data obtained from the generation of waste each month are subsequently accumulated for 3 months. inventory data was used to measure the generation and composition of hazardous waste usually use [13, 14] the generation and composition of hazardous waste for 3 months in port area are presented in table 1. based on the packaging volume, textile waste, used oil and grease are put in a 200 l drum; the filter is put in a 120 cm x 120 cm wooden box; and the wire and used battery are directly laid on the pallet because the wire is already in the form of rolls and the used battery already has its container. used cloth/textiles have flammable characteristics, because this waste contaminated with oil, grease or gasoline. this is similar to fajriyah and wardhani which state that fuel contamination of the textiles cause the textile to become flammable [15]. oil cleaning activities on machines can cause high use of textiles, especially ship engines at ports. toxic waste can be treated with an incinerator and must pay attention to disposal of the ash generation by stabilization [16]. table 1. generation and characteristics of hazardous waste in port area no type of waste characteristics amount per month amount of 3 month density (kg/m3) volume (m3) 1 used cloth/textile flammable 280 kg 840 kg 180.66 4.65 2 used oil toxic and highly flammable 800 kg 2400 kg 800 3 3 grease toxic and flammable 2 kg 6 kg 953 0.0063 4 oil filter toxic 200 pcs 600 pcs 5 wire toxic 2 rolls 6 rolls 6 used battery corrosive 7 pcs 21 pcs the composition of hazardous waste (w/w) can be seen in figure 1. this composition is used in determining storage and storage place at the waste station. the volume of storage used is 0.18 m3 with a capacity of 209 litters. the maximum volume and capacity of hazardous waste packaging can be utilized to determine the number of packages to be used. storage used is divided into two types namely drums and wooden boxes. other research also mentions used oil or flammable waste packaged in drums [17, 18]. this waste, nearby fire/sources of fire, sparks, and easily list friction in a long time either during transportation, storage, or disposal, thus the container must be kept safe from it. civil and environmental science journal vol. iii, no. 02, pp. 110-118, 2020 113 figure 1. the composition of hazardous waste in the study area. based on field observations, the land area that can be used as a waste station is 11 m x 8 m. waste management must consider the characteristics of waste, in which different waste characteristics must be spaced at least 60 cm and combustible waste must be given a wall with a thickness of 15 cm, made of concrete and 23 cm, made of bricks. the previous design mentioned that hazardous waste generation of 12 kg/week requires a land area of 4 m x 3 m [19]. toxic and corrosive waste is stored in containers with provisions. for storage in the form of tanks and/or containers, the requirements are: the packaging material must be able to store hazardous waste; and the packaging must have a strong cover to avoid spillage during storage, transfer and/or transportation; the packaging must also be in good condition, rustles, intact, and no leakage. some requirements must be fulfilled [20] such as; the container of materials must be in accordance with the character of hazardous waste; all containers must be stored in a closed area protected from rain and ventilated; and the ground floor of the building must be waterproof to avoid absorbing spills or spills leak. the number of drums and wooden boxes needed can be seen in table 2. dimension of drums and wooden boxes can see in figure 2. table 2. the number of drums and wooden boxes needed in hazardous waste transfer station no type of waste number of drums volume of drums number of containers dimension of wooden boxes 1 used cloth/textile 43 200 l 2 used oil 3 grease 4 filter 2 120 cm x 120 cm 5 wire 3 6 used battery 1 20% 56% 23% 1% combustible combustible and toxic toxic corrosive civil and environmental science journal vol. iii, no. 02, pp. 110-118, 2020 114 figure 2. dimension of drums and wooden boxes based on guidelines for issuance of recommendations for the transportation of hazardous and toxic waste [21] the symbols and labels used must be in line with the characteristics of the waste produced and refer to permenlh no. 14 of 2013 concerning hazardous waste symbols and labels [22]. symbols are placed on both filled and empty packaging to facilitate the placement and the use of the container. the symbol on the container is 15 cm x 15 cm (figure 3) and is in accordance with the waste characteristics. the following are the symbols used on hazardous waste station. figure 3. symbols of hazardous waste for hazardous waste station [22] the hazardous label contains complete information on the classification and types of hazardous waste along with a brief description in order to facilitate the handling of waste and to avoid accidents to workers. the hazardous label must be proportional and readable. the size used on hazardous label is 35 cm x 25 cm. all drums are stored in racks based on hazardous waste characteristics. used cloth / textile, grease, and oil are stored in one shelf because they use drums and are specifically for combustible materials. meanwhile, wooden boxes that provide other waste such as filters, wires, and used batteries are placed in one rack. shelf placement is adjusted according to the regulation as in figure 4. civil and environmental science journal vol. iii, no. 02, pp. 110-118, 2020 115 figure 4. rack placement on hazardous waste station (a) for drum and (b) for wooden boxes [21] 3.2. the design of hazardous waste station leakage prevention the container is used to collect spills in the hazardous waste station. it is an important facility because waste spills are prohibited from being directly disposed of in the drainage system. this calculation is based on the waste volume, and the waste spill volume. the waste volume per drum is by assumption of 30% of the waste generation shown in equation 1. if the number of drums in the industry is 43, the total volume of waste spills can be calculated (equation 2). volume waste = 0.18 x 30% = 0.054 m 3 volume waste spills = 0.054 m 3 x 43 = 2.322 m3 from the above calculation, total spill volume is 2,322 m3, obtained from the dimensions of the storage area with a value of 2 m x 2 m x 0.6 m and a 0.3 m freeboard. the data are considered sufficient for the manufacture of hazardous waste container for storage. the volume of storage containers, for individual hazardous liquid waste, is designed by multiplying the volume of hazardous liquid waste by 110%, in accordance with head of bapedal no. 01 of 1995 [23]. leaked collection tank is also added with soil with permeability of 10-5 cm/second in accordance with applicable regulations [21]. based on the decree of the head of bapedal no. 01 of 1995 [23], concerning procedures and technical requirements for the hazardous and toxic waste storage and collection, the floor at hazardous waste station must have a maximum slope of 1% to drain leaks so that leaks can flow directly into the trench and be collected in the reservoir. the plan picture for a wastewater collection is depicted in figure 5. to prevent the release of hazardous waste into the environment, tanks and / or containers are equipped with secondary storage [10]. secondary storage can take the form of one or more of the following conditions [10]: 1. is made or coated with a material which is compatible with the hazardous waste being stored and has sufficient thickness and strength to prevent damage due to pressure effects; 2. is placed on a foundation or base that can support resistance tank and/or container against pressure from above and below and is able to prevent damage caused by filling, pressure or uplift; 3. equipped with a leak detection system designed and operated for 24 (twenty four) hours so that it is capable of detecting damage to the tank structure and/or primary and secondary containers, or the release of hazardous waste from the secondary storage system; and 4. secondary storage, designed to accommodate and lift liquids from leaks, spills or precipitation. civil and environmental science journal vol. iii, no. 02, pp. 110-118, 2020 116 figure 5. top view of hazardous waste station in xyz port area 3.3. the design of hazardous waste station fire prevention the characteristics of hazardous waste to be stored is of great importance especially in building materials selection. this is to prevent accidents such as fires caused by combustible waste. the materials selection, which can be used as storage walls, can utilize red brick walls with a minimum thickness of 23 cm. likewise, roof construction may employ asbestos materials to resist corrosion and fire [24]. based on permenaker no. 04/ men/ 1980 [12], the installation of fire extinguishers must meet the requirements. single or multiple fire extinguisher(s) must be placed in a position that is easily seen, readily reached, and taken, as well as accompanied by a sign of installation. the marking must agree with permenaker no. 04/ men/ 1980 [12]. each extinguisher must be placed with a maximum distance of 15 meters between them unless otherwise stipulated by a safety employee or work safety experts. each fire extinguisher must be mounted to a wall by reinforcement or with other reinforcement construction or placed in an unlocked cabinet or box. the fire extinguishers installation must follow the above conditions; thus, the dry powder type of fire extinguishers can be placed lower so that the distance between the fire extinguishers base is not less than 15 cm from the floor surface. the fire extinguisher model may adopt chemical powder multi-purpose 9 kg. the fire extinguisher was chosen because it has a wide spray range and is less heavy. the effective of 95% is obtained from product specifications, in this design plan it is known that the longest range of one fire extinguisher is 7.5 m where 95% effectiveness means that at a distance above 7.125 m fire extinguishing is less effective. civil and environmental science journal vol. iii, no. 02, pp. 110-118, 2020 117 4. conclusion with the largest flammable and toxic composition of 56%, hazardous waste in the xyz port area requires land of 11 m x 8 m. based on the needs of the container, the size of the container is 2 m x 2 m x 0.6 m. while the effective rate of fire extinguishers is 95%. references [1] d. w. te velde and united nations conferenceon tradeand development., "foreign direct investment and development: an historical perspective," london: overseas development institute odi, 2006. [2] i.l.o., manajemen risiko kebakaran, jakarta: international labor office, 2018. [3] p. a. nugroho, s. prasetya, a. rozaq and a. iswanto, "rancang bangun alat pendeteksi kebakaran pada tempat penyimpanan sementara limbah b3," seminar nasional teknik mesin,, vol. 9, no. 1, 2019. [4] s. yudi, "rawannya pelanggaran dalam pengelolaan limbah bahan berbahaya dan beracun," lingkar widyaiswara, vol. 1, pp. 41-46, 2014. [5] indonesia government, government regulation no. 101 of 2014 regarding hazardous waste management, jakarta, 2014. [6] bsn, "sni 03-6572-2001 concerning procedures for designing ventilation and air conditioning systems in buildings," 2001. [7] nfpa13, standard for the installation of sprinkler systems, usa: quincy massachusetts, 2013. [8] megawati and t. w. panjaitan, "perancangan proses penyimpanan limbah bahan berbahaya dan beracun di pt. eta indonesia. titra." jurnal titra, vol. 3, no. 2, pp. 129-134, 2015. [9] bapedal, head of bapedal decree no. 5. kep-05 / bapedal / 09/1995 concerning procedures for labeling and symbols of waste, 1995. [10] ministry of environment and forestry, minister of environment and forestry no. p.12 2020 concerning the storage of hazardous and toxic waste, jakarta: kementrian lingkungan hidup dan kehutaan, 2020. [11] l. a. wibawa, "desain dan analisis kekuatan rangka tempat sampah di balai lapan garut menggunakan metode elemen hingga.," turbulen jurnal teknik mesin, vol. 1, no. 2, pp. 64-68, 2018. [12] minister of manpower and transmigration, minister of manpower and transmigration regulation no. per 04 / men / 1980 regarding the requirements for installation and maintenance of light fire extinguishers, 1980. [13] s. d. prameswari, m. a. nurhadi, i. rizaldi, m. octaviani, i. w. k. suryawan and b. ridhosari, "design of hazardous waste station in xyz radioactive industry.," envirotek: jurnal ilmiah teknik lingkungan, vol. 12, no. 1, pp. 80-86, 2020. [14] i. suryawan, evaluasi pengelolaan limbah padat b3 di fasilitas incinerator untuk puskesmas kota surabaya, surabaya: institut teknologi sepuluh nopember, 2014. [15] s. a. fajriyah and e. wardhani, "evaluasi pengelolaan limbah bahan berbahaya dan beracun (b3) di pt. x.," jurnal serambi engineering, vol. 5, no. 1, pp. 711-719, 2020. [16] i. w. k. suryawan, g. prajati and a. s. afifah, "bottom and fly ash treatment of medical waste incinerator from community health centres with solidification/stabilization," aip conference proceedings, vol. 2114, no. 1, p. 050023, 2019. [17] a. e. afiuddin and a. k. dwi, "studi perbaikan tempat penyimpanan sementara (tps) limbah b3 sesuai dengan limbah yang dihasilkan dan peraturan terbaru di pt. x.," iptek journal of proceedings series, vol. 2, pp. 78-84, 2018. [18] r. w. pratiwi, a. setiawan and a. e. afiuddin, "perancangan tempat penyimpanan sementara (tps) limbah b3 (studi kasus: bengkel maintenance pt. varia usaha)," seminar k3, vol. 1, no. 1, pp. 199-204, 2017. civil and environmental science journal vol. iii, no. 02, pp. 110-118, 2020 118 [19] t. n. pramestyawati, "pengelolaan limbah bahan berbahaya dan beracun (b3) laboratorium klinik di sumber limbah," prosiding seminar teknologi perencanaan, perancangan, lingkungan dan infrastruktur, vol. 1, no. 1, pp. 471-476, 2019. [20] n. anggarini, s. megi and prihatiningsih., "pengelolaan dan karakterisasi limbah b3 di pair berdasarkan potensi bahaya," beta gamma, vol. 5, no. 1, pp. 41-49, 2014. [21] ministry of enviroment, " guidelines for issuance of recommendations for the transportation of hazardous and toxic waste," 2015. [online]. available: http://pelayananterpadu.menlhk.go.id/images/dokumen/nonperizinan/pedomanpenerbitan-rekomendasi-pengangkutan-limbah-bahanberbahaya-dan-beracun-final.pdf. [accessed 20 09 2020]. [22] ministry of environment, permenlh no. 14 of 2013 concerning hazardous waste symbols and labels, jakarta: ministry of environment, 2013. [23] bapedal, decree of the head of bapedal no kep-01 / bapedal / 09/1995 concerning procedures and technical requirements for storage and collection of hazardous and toxic waste,jakarta, 1995. [24] i. w. murti and a. h. ibrahim, "identifikasi bahaya dan perancangan tempat penyimpanan sementara (tps) limbah b3 proses sandblasting di pt swadaya graha," energy, vol. 8, no. 1, pp. 1-7, 2018. civil and environmental science journal vol. 4, no. 1, pp. 076-083, 2021 76 the influence of damage to the geomembrane layer on the seepage pattern and discharge at the homogeneous embankment dam achsinwijayanto1*, pitojo tri juwono2, evi nur cahya2 1pt indra karya (persero) division of engineering i, malang, 65115, indonesia 2 water resources engineering department, universitas brawijaya, malang, 65145, indonesia achsinw@gmail.com1 received 01-01-2021; accepted 08-02-2021 abstract. placing the geomembrane layer on the upstream slope can control the seepage in homogeneous dams. poor geomembrane design, construction and maintenance caused damage to the geomembrane that caused a leak through the dam body. this study discusses the effect of damage on the geomembrane layer at the homogeneous embankment dam on the seepage pattern and discharge. the study location is in the sianjo anjo dam, aceh singkil district, a homogeneous dam with a geomembrane layer located in the dam body's upstream part. the damage of the geomembrane layer is assumed caused by the various defect of locations and size. the results show that the seepage pattern (phreatic line) tends to be weak in the geomembrane layer without damage. meanwhile, if the geomembrane layer is damaged, the larger the defects' width, the higher the phreatic line. however, the seepage pattern that occurs shows insignificant or almost the same. the seepage discharge increases with increasing defect width and decreasing defect location. keywords: damage, geomembrane, phreatic line, seepage 1. introduction dams are constructed across rivers and valleys to retain water for protection from floods, water storage, diversion of water to canals in high lands, producing energy, and many more. dams can be homogeneous (constructed using one type of soil) or zoned (consists of more than one type of soil with different hydraulic conductivities) [6, 15]. a homogeneous dam is an embankment dam in with the material forming the dam's body consisting of 80% of materials with almost the same grade. generally, the material used is semiimpermeable up to impermeable [1]. the control of seepage in homogeneous dams is carried out by placing an impermeable water layer in a geomembrane upstream part of the dam body to retain water [2]. various control methods can be used to reduce the seepage through the dam, such as foundation cutoffs, transition zones, adequate 1 cite this as: wijayanto, a., juwono, p.t., & cahya, e.n. (2021). the influence of damage to the geomembrane layer on the seepage pattern and discharge at the homogeneous embankment dam. civil and environmental science journal (civense), 4(1), 76-83. doi: https://doi.org/10.21776/ub.civense.2021.00401.7 civil and environmental science journal vol. 4, no. 1, pp. 076-083, 2021 77 core contact area, drainage material and blankets, upstream impervious blankets, impervious zones, and relief wells [14]. however, if the design, construction and maintenance are not good enough for the geomembrane, it can cause damage which results in leakage through the foundation and dam body. this study discusses the effect of damage to the geomembrane layer in the homogeneous embankment dam on the seepage pattern and discharge. the analysis is carried out assuming that the geomembrane layer is damaged. numerical modelling is becoming more widely used instead of experimental modelling to study seepage. seep/w, which geo-slope international ltd. develops, is a powerful finite element software for modeling groundwater flow in porous media. seep/w can model simple saturated steady-state problems or sophisticated saturated/unsaturated transient analyses with atmospheric coupling at the ground surface. therefore, the seepage analysis in this study used seep/w software based on the finite element numerical method [15, 16, 17, 20]. the location of the damage is determined at the top, middle and bottom. damage occurred in the form of defects with the width of the defects studied in this study were 10 cm, 25 cm and 50 cm [6]. reservoir water level calculated in the seepage analysis is the normal water level (elevation + 14.80m) [12]. 2. material and methods 2.1. location of study the study's location is at the sianjo anjo dam in the district of aceh singkil, a homogeneous dam with a geomembrane layer in the upstream part [3, 4, 5]. the sianjo anjo dam, located at coordinates 02° 25.5’ 69” s and 97° 58.51’73” e in kain golong village, aceh singkil district, aceh province (figure 1). figure 1. location of study 2.2. sianjo anjo dam the sianjo anjo dam was completed in 2010. the benefits of the sianjo-anjo reservoir construction are as follows: delivery of clean water for households, irrigation, and supporting tourism development. the sianjo anjo dam type is a homogeneous embankment dam with embankment material in the form of silty sand. the dam body's length is 192.65 m, on the upstream slope a layer of geomembrane is installed as an impermeable layer. figure 2 shows a cross section of the sianjo anjo civil and environmental science journal vol. 4, no. 1, pp. 076-083, 2021 78 dam reviewed in this study at sta 0 + 280 and the location of the damage assumed to occur in the geomembrane layer [3, 4, 5]. figure 2. cross section of sianjo anjo dam 0+280 2.3. data collection the data were obtained from balai wilayah sungai (bws) sumatera i, the dam owner and manager. the data required for the analysis are: [3] [4] [5] [7] [8] 1. coefficient of permeability table 1 shows material properties data of foundation and dam embankment used for seepage analysis, namely the coefficient of permeability (k). permeability is generally influenced by the material size and proportion [21]. table 1. coefficient of permeability (k) zone material k (cm/sec) zone 1 soil 1.04 x 10-3 zone 2 filter 1.00 x 10-3 zone 3 toe drain 1.00 x 10-2 zone 4 riprap 1.00 x 10-1 zone 5 backfill material 1.00 x 10-4 zone 6 foundation 1.53 x 10-4 table 2. data of open stand pipe piezometer on 26th october 2019 (nwl, el. +14.80m) piezometer coordinate x (m) coordinate y (m) pore water pressure (kpa) op3.1 79.875 11.050 0.000 op3.2 79.875 6.516 46.482 op3.3 79.875 1.252 91.200 op4.1 93.375 6.993 21.672 op4.2 93.375 1.404 87.571 remark : zone = soil zone = filter zone = toe drain zone = rip rap zone = backfill materials zone = foundation op3, op4 = open standpipe piezometer instrumentation 1 2 3 4 5 6 civil and environmental science journal vol. 4, no. 1, pp. 076-083, 2021 79 the geomembrane’s coefficient of permeability and the gcl data based on the benchmark are 1.00 x 10-15 cm/s and 1.00 x 10-11 cm/s, respectively [9]. 2. data of op3 and op4 open stand pipe piezometer instrumentation readings data of op3 and op4 open stand pipe piezometer instrumentation readings (table 2) result from field observations on 26th october 2019 at the normal water level (nwl, el. +14.80m). this data is used for calibration with analysis results. 3. the dam body seepage discharge’s data measured on the v-notch instrument on 26th october, 2019 was 0.909 l/s. 2.4. stages of study seepage analysis to determine the flow pattern (phreatic line) and the seepage discharge that comes out through the foundation and the dam body due to defecting of the geomembrane is performed in the following steps: 1. collecting data, namely data on the geometry of the foundation and dam body, data on embankment material and foundation, data on readings of standpipe piezometer and v-notch. 2. performed seepage analysis on the foundation and the body of the dam at the level of the reservoir water level in normal conditions (elevation + 14.80 m) analysis of seepage conditions without damage/existing conditions the data will be calibrate by comparing the results of the seepage analysis of existing conditions and the results of the seepage analysis using field instrumentation data (piezometer and v-notch readings) [10] [11] [13]. seepage analysis with the condition that there is damage to the geomembrane layer for each location and the width of the defect. 3. the results of the seepage analysis show the seepage pattern (phreatic line) and the seepage discharge [14][18][19]. 3. result and discussion the results of the seepage analysis of the existing conditions, as shown in figure 3 show that if the geomembrane layer is not damaged, the phreatic level in the body of the dam tends to be lower. the seepage rate through the dam is 4.8971 x 10-6 m3/s/m. with a dam body length of 192.65 m, it was found that the seepage discharge was obtained of 0.943 l/s. furthermore, the seepage discharge is close to the discharge measured on the v-notch instrument of 0.909 l/s. figure 3.analysis result of seepage in existing condition the amount of pore water pressure from the riser piezometer analysis and readings at each piezometer tip location is shown in table 3. civil and environmental science journal vol. 4, no. 1, pp. 076-083, 2021 80 table3. pore water pressure from the riser piezometer analysis and readings piezometer coordinate x coordinate y analysis result reading result (m) (m) (kpa) (kpa) op3.1 79.875 11.050 0.000 0.000 op3.2 79.875 6.516 42.063 46.482 op3.3 79.875 1.252 93.358 91.200 op4.1 93.375 6.993 30.105 21.672 op4.2 93.375 1.404 84.935 87.571 the validation test of the piezometer data from the observations and analysis results yielded an rmse value of 4.552, nse of 0.984 with a "good" category and a correlation coefficient (r) of 0.992 indicating a " very strong" category. so, it can be concluded that the value of the pore pressure of the analysis results is close to the observed results. so that the calibration result data can be used for further seepage analysis. the data from the calibration results are used for further analysis, as shown in table 4. table 4. permeability coefficient (k) data calibration result zone material k (cm/sec) zone 1 soil 1.04 x 10-3 zone 2 filter 1.00 x 10-3 zone 3 toe drain 1.00 x 10-2 zone 4 riprap 1.00 x 10-1 zone 5 backfill materials 1.00 x 10-4 zone 6 foundation 2.10 x 10-3 the damage in the geomembrane on the dam body can conclude that as the defect width increases and the defect location decreases, the seepage discharge will increase. if there is no damage to the geomembrane and the resulting seepage discharge is constant. the phreatic level is affected by the width of the defect. the wider the defect, the higher the phreatic level. however, the flow pattern at each defect width at the same location showed insignificant differences (figure 4). a) phreatic line on damage location on the upper part of geomembrane layer civil and environmental science journal vol. 4, no. 1, pp. 076-083, 2021 81 b) phreatic line on damage location on the middle part of geomembrane layer c) phreatic line on damage location on the lower part of geomembrane layer figure 4.flow pattern (phreatic lines) on the dam body with various damage locations and defect width in the geomembrane layer. figure 5. the influence of the size and location of the defect to the seepage discharge the analysis results show that the amount of seepage discharge for defect widths of 10, 25 and 50 cm is 2.71 x 10-5, 2.76 x 10-5 and 2.79 x10-5 m3/s/m respectively. the bigger the defect, the greater the seepage discharge through the dam's foundation and body. the amount of seepage discharge for a 10 cm defect width is 5.23 l/s or 1.94% of the mean annual inflow. the seepage discharge for the 25 cm defect width was 5.33 l/s or 1.98% of the mean annual inflow. furthermore, the seepage discharge for a defect width of 50 cm is 5.38 l/s or 2.00% of the annual mean inflow. the amount of seepage discharge that occurs is less than the permit seepage discharge in terms of quantity. the allowable civil and environmental science journal vol. 4, no. 1, pp. 076-083, 2021 82 seepage discharge is 2.00% of the average annual inflow discharge (annual inflow = 0.27 m3/s), or is 5.39 l/s. 4. conclusions the seepage analysis results under existing conditions (without damage) show that the dam body's phreatic level tends to be lower. the low phreatic level is because there is an intact geomembrane layer in the dam's upper reaches. the seepage analysis in the supposedly damaged geomembrane layer shows that the greater the defect's width, the higher the phreatic line. however, the flow patterns that occur show an insignificant difference or nearly the same. during this time, the seepage discharge that occurs shows that with an increase in the defect's width and a decrease in the location of the defect, the seepage discharge will increase. the results show that damage to the geomembrane layer will result in leakage through the dam body. therefore, a good design, construction and proper maintenance of the dam body's geomembrane layer is necessary so that leakage through the dam body can be avoided so that the dam body's safety can be awake. references [1] s. sosrodarsono, k. takeda, "bendungan type urugan". pradnya paramita. jakarta. 2002. [2] balai bendungan. "evaluasi rembesan". materi bimbingan teknis pemeriksaanbesar bendungan. balai bendungan direktorat jenderal sumber daya air. jakarta. 2015 [3] anonymous. "laporan akhir evaluasi penyempurnaan konstruksi waduk sianjo anjo".pt wiratman &associates jo pt citra adiyasa estima. jakarta. 2017. [4] anonymous."laporan evaluasi penanganan bendungan sianjo anjo". pt indra karya (persero) divisi engineering i jo pt tuah agung anugerah & pt aztindo rekaperdana. banda aceh. 2020. [5] anonymous. "laporan ringkas persiapan pengisian pertama pembangunan waduksianjo anjo". pt wiratman &associates. jakarta. 2007. [6] w. cen, h. wang, d. li, "seepage properties of geomembrane faced sandy-gravel dams with different dam heights due to defect-induced leakage". advances in engineering research (aer), volume 143, 6th international conference on energy and environmental protection (iceep), pp. 1361-1365, 2017 [7] anonymous. "final laporan akhir pekerjaan sid embung sianjo anjo dan embungrimo di kabupaten aceh singkil". pt resco nusantara consultan. jakarta.2001. [8] anonymous. "laporan geologi dan mekanika tanah embung sianjo anjo dan embungrimo di kabupaten aceh singkil". pt resco nusantara consultan. jakarta. 2001. [9] s. demirdogen, "numerical analysis of leakage through defective geomembrane liners in embankment dams". thesis, scholar commons university of south florida, 2018. [10] motovilov, y.g., gottschalk, l., engeland, k. & rodhe, a. "validation of a distributed hydrological modelling against spatial observations". elseiver agricultural and forest meteorology. 98 : 257 – 277. 1999. [11] sugiyono. "statistika untuk penelitian". bandung: cv. alfabeta. 2007 [12] r.h. ardiansyah, sobriyah, a.h. wahyudi, “pengaruh fluktuasi muka air waduk terhadap debit rembesan menggunakan model seep/w (studi kasus di bendungan benel, kabupaten jembrana, bali)”, e-jurnal mariks teknik sipil, pp. 471-476, 2014. [13] a.l. huda, s. prabandiyani r.w., suharyanto, “evaluasi tekanan air pori dan rembesan pada bendungan panohan”, reka buana : jurnal ilmiah teknik sipil dan teknik kimia, 4 (2), pp 102-111, 2019. [14] h.k. shayan, e. a. tokaldany, “ effects of blanket, drains, and cutoff wall on reducing uplift pressure, seepage, and exit gradient under hydraulic structures”, international journal of civil engineering, vol. 13, no. 4a, transaction a: civil engineering, pp. 486-500, 2015. [15] juwono, p., asmaranto, r., & murdhianti, a. (2020). stability of existing banyukuwung dam in recent hydrology and geotechnical conditions. civil and environmental science journal civil and environmental science journal vol. 4, no. 1, pp. 076-083, 2021 83 (civense), 3(2), 60-71. doi: https://doi.org/10.21776/ub.civense.2020.00302.1. [16] i.n. aribudiman, m.d.w. ardana, i g. n oka suputra, “penggunaan program geo-studio seep/w untuk menentukan rembesan air lindi pada tanah lempung”, jurnal ilmiah teknik sipil – a scientific journal of civil engineering, vol. 22, no.2, pp 108-113, 2018. [17] y. astuti, a. masrevaniah, s. marsudi, “analisa rembesan bendungan bajulmati terhadap bahaya piping untuk perencanaan perbaikan pondasi”, jurnal teknik pengairan, vol. 3, no. 1, pp. 51–60, 2012. [18] i.g.n. putu dharmayasa, “ analisis rembesan di bawah tubuh bendungan urugan”, jurnal paduraksa, vol.7, no. 1, pp.53-62, 2018. [19] sudirman,” eksperimental pola aliran dan rembesan di bawah pondasi bendungan urugan tanah”, jurnal ilmiah techno entrepreneur acta, vol. 5 no.1, pp. 67-75, 2020. [20] a. imron, d. sarah, s. hardiyati, k. w. sadono, “analisa geoteknik bendungan gongseng terhadap keamanan rembesan, stabilitas lereng dan beban gempa”, jurnal karya teknik sipil, vol. 6, no.1, pp. 185 – 192, 2017. [21] en cahya, e arifi, r haribowo. 2020. recycled porous concrete effectiveness for filtration material on wastewater treatment. international journal 18 (70), 209-214. doi: https://doi.org/10.21660/2020.70.9266. . open access proceedings journal of physics: conference series civil and environmental science journal vol. i, no. 01, pp. 027-033, 2018 27 data generation in order to replace lost flow data using bootstrap method and regression analysis gatot eko susilo1 1civil engineering dept., universitas lampung, bandar lampung, 35145, indonesia gatot89@yahoo.ca received 28-02-2018; revised 23-03-2018; accepted 06-04-2018 abstract. this paper aims to find method to generate data in order to replace lost flow data in the series of discharge data in sungai seputih river, lampung province. bootstrap simulation is used to estimate the discharge data and complete the existing discharge data. regression analysis is also used to find the pattern of data distribution. results of the research show that both methods are able to generate new series of flow data that the distribution is similar to available field data. results also show that the use of statistical methods is one way to tackle the problem of data limitations due to missing or unrecorded data. the weakness of data generation using a combination of bootstrap methods and regression analysis is the disappearance of extreme values in the data series. existing extreme values have been modified to ideal values that satisfy certain distributions. however, careful analysis is required in using statistical method, so that the results of analysis do not deviate from the field conditions. keywords: data generation, flow data, bootstrap method, regression analysis. 1. introduction hydrology is the study of the earth's water sundry which includes the process of its occurrence, its movement, its distribution, and its relation to the environment and the living creatures. understanding of the science of hydrology is very useful in understanding the concept of water balance on a global scale on the surface of the earth. hydrological events such as rain and flow are recorded in the information referred to as hydrological data. almost all water resources development activities require hydrological information for basic planning and design. if the hydrological information used is not suitable and does not meet the requirements, it may result in incorrect and inaccurate planning and design. interpretation of the hydrological phenomenon will be carried out properly if supported by sufficient data availability. sufficient data collection tools and consistent data collection activities are essential for generating good hydrological data. the most important hydrological data is the flow data of a river. basically, all water resource planning requires flow data in the calculation. but since the flow recorder stations in rivers in indonesia are not always available then the amount of discharge can be calculated by varying the rain to discharge. rainfall data is more available in watersheds in indonesia. the rainfall recorder station is easier to find than the flow recorder station. this is because rain stations are not only installed by the department of public work but are also installed by department of agriculture and department of transportation with various objectives. civil and environmental science journal vol. i, no. 01, pp. 027-033, 2018 28 various methods have been created by people to diversify rain into debit. but the accuracy of each method is still being debated. the calibration and verification process of a hydrological model is an absolute process to determine the validity of a model or method. the problem is data for calibration and verification is rarely available in indonesia. automation of flow recorders and rain gauges in indonesia has not been equally distributed in indonesia. consequently, most of the debit or rainfall data in indonesia are not valid enough data to be used in water resource planning. as an effort to validate the data, the planners perform validation analysis with various statistical methods. the problem of scarcity of hydrological data has been overwhelmingly faced by water resource planners. some of them attempt to generate data to add or supplement lost data. one of the known data generation methods is monte carlo simulation. monte carlo simulation is a simulation to determine a random number of sample data with a particular distribution. the goal of monte carlo simulation is to find a value close to the real value, or the value that will occur based on the distribution of the sampling data [1]. the monte carlo simulation involves the use of random numbers to model the system, where time does not play a substantive. monte carlo simulation is undertaken by artificial data generation using pseudo random numbers generator. basically, a monte carlo simulation is performed based on a particular sampling distribution. the key is to identify the distribution of existing sample data. randomly, simulations of numbers are performed so that a combination of nearfit distribution is most fit. monte carlo simulations have been used to generate rainfall data in stochastic hydrological modelling studies in czech republic [2]. this simulation has also been used as a method to quantify drainage discharge components in a stochastic drainage discharge model in south africa [3]. in addition to the monte carlo simulation method, people often use the bootstrap method. the bootstrap method is a method used to estimate the parameters of a population suspected of the statistical value obtained from the population sample. this method is often used because it does not base on certain distribution assumptions. bootstrap is a method that can work without the need for distribution assumptions because the original sample is used as a population [4]. bootstrap was first introduced by efron in 1979. bootstrap is a method based on data simulation for statistical inference purposes [5]. the bootstrap method is performed by random sampling with a re-sampling with replacement. some sources state that the bootstrap sample size (d) used is less than or greater than the sample data (n). however, the most optimum and effective way to guess parameters is the size of the bootstrap instance equal to the size of the sample data. the bootstrap method is a method based on resampling the sample data with the condition of return on the data in completing the statistics of the size of a sample in the hope that the sample represents the actual population data. usually re-sampling size is taken thousands of times to represent the population data. this method is great for relatively small sample data sizes [6]. bootstrap method has been used for quantifying uncertainty on sediment loads in germany [7]. previously, the method was also used in estimating the uncertainties related to the sample size in research of estimation of future discharge of the rhine river [8]. the newest one, in china bootstrap method was used to analyze the influence of rainfall spatial uncertainty on hydrological simulations [9]. this paper aims to generate data in order to replace lost flow data in the series of discharge data in sungai seputih river, lampung province. the corresponding flow data will be used to calculate the availability of water in the way seputih river for irrigation purposes in the seputih irrigation area. due to the lack of data, the bootstrap simulation will be used to estimate the discharge data and complete the existing discharge data. regression analysis is also used to find the pattern of data distribution. 2. material and methods in this research, the bootstrap method will be used to supplement lost discharge data in order to calculate the dependable flow to be used in calculating the allocation of irrigation water in the pengubuan river. the river is located in the central lampung regions, indonesia. the river is currently supplied water for irrigation areas which is way pengubuan irrigation area. the irrigation civil and environmental science journal vol. i, no. 01, pp. 027-033, 2018 29 area captured 5,000 ha and 3,500 ha as potential and functional paddy field, respectively. the calculation of irrigation water allocation is an activity to calculate the balance between water availability and water requirement in the irrigation area. in order to calculate irrigation water availability, a dependable flow is calculated with 80% reliability. for the calculation, the daily average discharge data in monthly period for 10 years have to be available. in fact, the daily average discharge data at way pengubuan dam is only available for year 2011 until 2017. the available data is also not a complete data because there are some missing or undocumented data. the available discharge data view can be seen in table 1. table 1. existing flow data (in m3/s) of way pengubuan river at way pengubuan dam. year/month 2011 2012 2013 2014 2015 2016 2017 jan 4.85 4.03 5.23 3.34 3.21 4.58 feb 5.04 5.06 4.36 5.11 4.35 3.77 mar 3.86 5.05 3.16 4.27 5.69 5.40 apr 4.39 4.99 4.41 3.67 5.87 4.76 may 3.17 5.41 4.96 3.92 5.37 jun jul 1.82 3.00 2.45 0.83 2.11 aug sep oct nov dec 3.60 3.46 3.78 4.15 1.13 4.69 source: bbws mesuji sekampung (2018) to calculate the dependable flow required data flow with a data length of at least 10 years. to complete the missing data then the bootstrap method is taken to generate the data. the data generation procedure with bootstrap method is implemented as follows: • calculating the maximum and minimum values of monthly data for every year of data. this procedure will result in the maximum and minimum value of january, february, march, april, may, july, and december data for year 2011 to 2017. • generating data using bootstrap method and complete flow data for the period of january, february, march, april, may, july, and december data for year 2011, 2017, 2018, 2019, and 2020. • generating data using bootstrap method and complete flow data for the period of june for year 2011 to 2020. value of june is random value between may and july values. • to complete flow data of september, october, and november for year 2011 to 2020 then regression analysis is undertaken. regression equation is formed for all data year and after that the shape of regression curves are modified to find ideal equation for the data of each year. final equation of the regression then is used to generate new serial data. once the new serial of data is found, dependable flow with 80% reliability is calculated using weibull probability equation [10]. the probability of each daily average monthly data is calculated using following formula: 𝑃 = 𝑚 𝑛+1 (1) where, p is the probability of data that explain the reliability percentage of data, m is the number of data after sorted from maximum to minimum value, and n is number of data. civil and environmental science journal vol. i, no. 01, pp. 027-033, 2018 30 3. result and discussion result of procedure 1 is given in table 2. the result shows the maximum and minimum value of january, february, march, april, may, july, and december data for year 2011 to 2017. table 2. maximum and minimum flow data (in m3/s) of way pengubuan river month jan feb mar apr may jun jul aug sep oct nov dec max 5.23 5.11 5.69 5.87 5.41 3.00 4.69 min 3.21 3.77 3.16 3.67 3.17 0.83 1.13 source: calculation bootstrap method is used to generate data and complete flow data for the period of january, february, march, april, may, july, and december data for year 2011, 2017, 2018, 2019, and 2020. the value of particular month is actually random data between maximum and minimum value of corresponding month. another generating data process using bootstrap method is undertaken and complete flow data for the period of june for year 2011 to 2020. value of june is random value between may and july values. the results are given as follows: table 3. result of data generation using bootstrap method year/month 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 jan 4.16 4.85 4.03 5.23 3.34 3.21 4.58 4.70 3.65 4.00 feb 4.75 5.04 5.06 4.36 5.11 4.35 3.77 5.29 4.26 3.66 mar 5.42 3.86 5.05 3.16 4.27 5.69 5.40 5.17 4.33 3.61 apr 5.34 4.39 4.99 4.41 3.67 5.87 4.76 4.51 3.99 3.82 may 4.31 3.17 5.41 4.96 3.92 5.37 5.05 3.50 3.39 4.10 jun 3.50 2.97 3.95 4.66 1.08 4.34 3.27 2.34 2.66 4.26 jul 5.00 3.64 6.00 4.89 1.66 4.22 2.50 1.20 1.94 4.18 aug 0.89 2.81 0.27 1.37 3.90 sep 0.00 1.08 3.69 oct 0.00 1.22 3.80 nov 2.76 0.62 1.92 4.17 dec 3.60 3.46 3.78 4.15 1.13 4.69 3.60 2.40 3.32 4.13 source: calculation regression analysis is undertaken to form ideal shape of data distribution. the example of regression curve formed by regression analysis is given for year 2011 in figure 1. the curve of actual data is modified into new curve formed by regression analysis. using the equation of the new regression analysis, a serial of new data is generated. this serial data is finally used as serial data for dependable flow calculation. figure 1. curve of actual data (black line and black dot) and regression curve formed by regression analysis (dashed line) for year 2011 data y = 0,03x3 0,567x2 + 2,559x + 1,985 r² = 1 0,0 1,0 2,0 3,0 4,0 5,0 6,0 1 2 3 4 5 6 7 8 9 10 11 12 f lo w ( m 3 /s ) month civil and environmental science journal vol. i, no. 01, pp. 027-033, 2018 31 using same procedures regression curve formed by regression for each year is given as follows: table 4. regression equations formed by modified data year regression equation formed 2011 y = 0.03x3 0.567x2 + 2.559x + 1.985 2012 y = 0.015x3 0.239x2 + 0.579x + 4.483 2013 y = 0.025x3 0.484x2 + 2.317x + 2.097 2014 y = 0.011x3 0.181x2 + 0.4x + 4.784 2015 y = 0.035x3 0.646x2 + 2.666x + 1.494 2016 y = 0.046x3 0.893x2 + 4.465x 0.786 2017 y = 0.025x3 0.464x2 + 2.053x + 2.42 2018 y = 0.031x3 0.545x2 + 2.009x + 3.206 2019 y = 0.023x3 0.409x2 + 1.676x + 2.36 2020 y = 0.022x3 0.411x2 + 1.66x + 2.343 source: calculation using equations above the final generated data is given in table 5. dependable flow is undertaken by sorting daily average monthly flow data. weibull probability equation is used to calculate the value of reliability for each month. the results of reliability calculation weibull probability equation are given in table 5 below. table 5. serial flow data based on regression curve m jan feb mar apr may jun jul aug sep oct nov dec p 1 5.01 5.29 5.81 5.73 4.96 4.26 4.18 3.90 3.69 3.80 4.17 4.13 0.09 2 4.84 5.08 5.37 5.22 4.71 3.98 3.18 2.46 1.97 1.87 2.30 3.69 0.18 3 4.70 5.00 5.37 5.07 4.36 3.79 2.63 2.03 1.74 1.68 2.13 3.44 0.27 4 4.03 4.95 5.17 4.81 4.21 3.43 2.49 1.95 1.54 1.55 1.92 3.41 0.36 5 4.01 4.94 5.08 4.51 3.69 3.41 2.49 1.53 1.27 1.37 1.92 3.32 0.45 6 3.81 4.87 4.65 4.19 3.63 3.04 2.41 1.50 1.08 1.22 1.90 2.94 0.55 7 3.96 4.81 4.62 4.06 3.50 2.66 1.97 1.37 0.96 0.88 1.50 2.89 0.64 8 3.65 4.52 4.47 3.99 3.39 2.59 1.94 1.33 0.60 0.56 1.46 2.53 0.73 9 3.55 4.26 4.33 3.94 3.28 2.34 1.20 0.27 0.00 0.00 0.62 2.40 0.82 10 2.83 3.66 3.61 3.85 3.05 1.79 0.51 0.00 0.00 0.00 0.00 0.94 0.91 source: calculation using interpolation technique dependable flow with 80% reliability for each month are presented in figure 2. the resulting dependable flow above illustrates the pattern of rainy and dry seasons occurring in the study area. therefore, it can be concluded that the data can be statistically used as a material calculation of water allocation in the area concerned. for irrigation purposes, usually the dependable flow value is calculated based on a period of 15 days. to calculate the dependable flow with a period of 15 days, it can be done by taking two random numbers whose average is the value in the corresponding month. for example, to calculate the value of dependable flow in the period january i and january ii, we have to take two random numbers where the average of the two random numbers is the january dependable flow value. the weakness of data generation with a combination of bootstrap methods and regression analysis is the diminished extreme value of a distribution. existing extreme values have been modified to ideal values that satisfy certain distributions. the influence of climate anomalies such as el nino must be closely watched because the minimum extreme values sometimes appear this year. minimal extreme values will affect the dependable flow calculation. sometimes a minus number appears in the civil and environmental science journal vol. i, no. 01, pp. 027-033, 2018 32 generated data. if the minus value appears in serial data then the value must be replaced with the value of zero because logically there is no minus flow value. figure 2. dependable flow with 80% reliability of pengubuan river basically, the best way to calculate dependable flow is to collect as much historical data as possible. but to get a lot of data flow and complete is not easy in indonesia. therefore, statistical analysis is the best way to do it. statistical analysis is probably the best way to process a small amount of data. but statistical analysis should be accompanied by empirical analysis to test the accuracy of the preceding analysis. 4. conclusions data generation in order to replace lost flow data in the series of discharge data in sungai seputih river, lampung province has been analyzed. the results show that the combination of bootstrap method and regression analysis is able to generate new data whose distribution is similar to available field data. however, complete data is a key requirement in a water resource plan. statistical methods can be taken to solve the problem of data availability. however, careful analysis is required in using statistical methods so that the results of analysis do not deviate from the field conditions. acknowledgements the author would like to express his deep gratitude to mrs. eka desmawati and mr. ankavisi nalaralagi from bbws mesuji sekampung for their support of this research especially in providing hydrological data. references [1] huang, h. 2018. monte carlo simulation using excell (in bahasa indonesia), globalstats academic publication. http://www.globalstatistik.com/simulasi-monte-carlo-dengan-excel/. march 19th (19:05). [2] březková, l., starý, s., and doležal, p. the real-time stochastic flow forecast. soil & water res., 5(2): 49–57. [3] flores, g. 2015. a stochastic model for sewer base flows using monte carlo simulation. master thesis, stellenbosch university, south africa. [4] sungkono, j. 2015. bootstrap re-sampling observation on estimation parameter regression using software r (in bahasa indonesia). magistra no. 92 year xxvii. [5] efron, b. and tibshirani, r. j. 1993, an introduction to the bootstrap, chapman and hall, new york. [6] monalisa, a. 2016. use of bootstrap resampling method for simulation data time series model using arima, undergraduate thesis (in bahasa indonesia), university of jember. 3,58 4,39 4,41 3,98 3,32 2,46 1,38 0,57 0,19 0,14 0,83 2,46 0,00 0,50 1,00 1,50 2,00 2,50 3,00 3,50 4,00 4,50 5,00 jan feb mar apr may jun jul aug sep oct nov dec d is c h a r g e ( m 3 /s ) month civil and environmental science journal vol. i, no. 01, pp. 027-033, 2018 33 [7] slaets, j. i. f., piepho, h., schmitter, p., hilger, t. and cadisch, g. 2017. quantifying uncertainty on sediment loads using bootstrap confidence intervals. hydrol. earth syst. sci., 21: 571–588. [8] lenderink, g., buishand, a. and deursen, w. 2007. estimates of future discharge of the river rhine using two scenario methodologies: direct versus delta approach. hydrol. earth syst. sci., 11(3): 1145–1159. [9] zhang, a., shi, h., li, t. and fu, x. 2018. analysis of the influence of rainfall spatial uncertainty on hydrological simulations using the bootstrap method. atmosphere 9(71): 2–24. [10] weibull, w. 1951. a statistical distribution function of wide applicability, j. appl. mech.-trans. asme, 18(3): 293–297. civil and environmental science journal vol. 4, no. 1, pp. 022-029, 2021 22 eco-bricks method to reduce plastic waste in tanjung mekar village, karawang regency dwi ariyani1*, niken warastuti1, resti nur arini1 1civil engineering department, faculty of engineering, pancasila university, south jakarta, 126400, indonesia dwi.ariyani@univpancasila.ac.id1 received 22-11-2020; accepted 28-12-2020 abstract. plastic waste is a source of environmental pollution in indonesia. the increase in the use of plastic materials has resulted in an increase in the production of plastic waste from year to year. destruction of plastic waste by burning will only worsen health because of the dioxin substances produced. the most appropriate method to handle waste is to use the eco-bricks method. the aim of the study was to see the strength of eco-bricks material compared to other materials usually use in the market like red bricks and concrete bricks. the test is carried out using a compressive strength testing machine on several specimens. from the results of tests in the concrete laboratory university of pancasila using eco-bricks material, with three specimens are plastic bottles filled with pure plastic, sand, and a mixture of plastic and sand, compared to red bricks and concrete bricks in the market. the strength test results show that the eco-bricks material containing sand shows the greatest compressive strength value is 41.2 mpa, compared to the red bricks which is 27 mpa and concrete bricks is 38 mpa. from the result eco-bricks has a higher compressive strength value than other materials. keywords: compressive strength, eco-bricks, plastic waste, strength 1. introduction according to a survey by nova chemicals, indonesia is the second largest contributor to sea waste after china, which is 1.29 million metric tons/year. at present there are still many people in indonesia who throw garbage in any place, and can caused flooding in the river. the river is polluted with a lot of waste, one of which is the citarum river. citarum river is a river that is very important for residents of west java. the condition of the citarum river which is very alarming is polluted by waste and garbage. in the world's leading survey site, the citarum river occupies the 4th position for the dirtiest river problem. the rubbish that pollutes the citarum river is more inorganic or unbiodegradable, for example plastic, bottles or beverage cups, plastic food wrapping, and so on. as we know plastic waste is very difficult to decompose, it takes more than 100 years to decompose the plastic decomposed or decompose completely [1]. garbage is a common problem, currently all countries in the world are facing the same problem, regarding waste management, especially plastic waste, because plastic takes 1 cite this as: ariyani, d., warastuti, n., & arini, r.n. (2021). eco-bricks method to reduce plastic waste in tanjung mekar village, karawang regency. civil and environmental science journal (civense), 4(1), 22-29. doi: https://doi.org/10.21776/ub.civense.2021.00401.3 civil and environmental science journal vol. 4, no. 1, pp. 022-029, 2021 23 decades to decompose properly, currently plastic production in the world currently reaches 300 million tons per year [2], it is estimated that there are 150 million tons of plastic in the ocean and another 250 million tons will increase the burden of marine waste towards the trend of increasing urbanization [3]. currently, indonesia ranks second in producing plastic waste after china, which is estimated to reach 3.22 million tons per year, even four large rivers in indonesia are named as the top 20 dirtiest rivers in the world, namely brantas, solo, progo and serayu. the plastic waste reduction program is currently being promoted throughout the world, the government of indonesia is targeting that by 2025 it can reduce plastic waste and other waste in the next sea by 70%, and targets the reuse of plastic waste by 30% [4], there are many methods to achieve the target. these include reusing existing plastic waste (reuse), eco bricks is a method of reusing plastic waste as an alternative to environmentally friendly building materials, currently people are still doubtful about the use of eco bricks, especially with regard to technical properties. it is necessary to make a comprehensive research to determine the technical properties of the eco bricks. testing of ecobricks materials using sand and plastic waste to produce bricks, was carried out by heating at 2000c. then compared the results between bricks mixed with sand and plastic with traditional local bricks, it was observed that plastic sand bricks have low water absorption, low porosity and high compressive strength [5]. dhote, 2016, conducted research on investigating the use of pet bottles as sustainable materials in construction. tested the compressive strength of bottles filled with sand with a ratio between fly ash and different sand in each bottle, the results show that with a fly ash and sand ratio of 2: 1 the compressive strength results are 22,000 kg, more greater than the ratio of 1: 2, 1: 3, 1: 1, the smallest value in the material that contains sand is 7,260 kg [6]. the following research focuses on one of the eco-bricks technical properties, namely the compressive strength of the eco-bricks, when compared to the eco-bricks that have been made before, as well as with bricks, bricks and concrete bricks on the market. 2. material and methods research on eco-bricks is currently growing rapidly, there are several materials for making environmentally friendly bricks, from the simplest stages to the use of complex mixtures, the method of making eco-bricks can be divided into the following table (table 1) table 1. distribution of eco-bricks making methods method type characteristic warming up compression cement binding another mixture addition of water 1 pure solid plastic no yes no no no 2 solid plastic filler no yes no yes no 3 cold binding plastic no yes yes yes yes 4 plastic hot binding without water yes yes no yes no 5 plastic hot binding with water yes yes no yes yes 6 cement plastic binding yes yes yes yes yes research on types of plastic fillers and cold plastic bindings, more developed in north africa, egypt, china and india by utilizing 20-40% of the plastic composition of the whole, while hot plastic binding is widely used in central and south africa, such as nigeria, the heating method is carried out civil and environmental science journal vol. 4, no. 1, pp. 022-029, 2021 24 without the addition of cement, but the binding process of the material using plastic that is heated to form tar. the use of plastic bottles as eco-bricks is proven to be comfortably not much different from bricks from cement, even eco-bricks plastic bottles can reduce temperatures around 0.5-1°c in the home compared to the use of concrete bricks [7]. thirugnanasambantha et al, examined the strength of plastic sand bricks method 6, which is a mixture of ash, cement, sand and water, then mixed with plastic that has melted with a ratio of plastic and sand 1: 3, 1: 4 and 1: 5, the results of compressive strength in sequence is 4.49 (n/mm2); 5 (n/mm2) and 5.6 (n/mm2) [8]. raj (2018), conducted a test of a mixture of plastic and quarry from 30% to 42%, ash 60% 40% and the remaining binding material in the form of cement (10 15%), plastic material was crusher first, then mixed with ash and cement without using heating, in this case cement is used as a binding material, the results show a compressive strength of 1.85 n/mm2 to 5.22 n/mm2, the biggest yield is obtained with a plastic mixture of 37% [9]. priya (2014), mixing ash, limestone, cement and plastic waste that has been crushed, adding 20% plastic and molding eco-bricks without heating, the result is the addition of plastic mixture can increase the compressive strength of eco-bricks, but did not mention the exact value [10]. kamble (2017), examines eco-bricks method 2, which is without heating and without binding, only adding plastic and sand into plastic bottles and then compacted with a plastic mixture of 12% and the rest is sand, and the second eco-bricks is added by tar, the result is eco-bricks has strength greater than just a mixture of cement and sand, the compressive stress value reaches 2.7 n/mm 2, while the addition of tar is able to increase the compressive stress to 3 n/mm2 [11]. taaffe (2014) conducted an eco-bricks study using method 1, which included inserting plastic waste into mineral water bottles, from 10 specimens with various types of densities, compressive strenght varied from 2.59 n/mm2 to 2.8 n/mm2 , this variation is in line with the level of compaction of the plastic in the bottle, the denser the plastic in the bottle, the higher the value of compressive stress [12]. the method used in this study was a literature review with observations and test materials in the pancasila university concrete laboratory. the field survey was conducted prior to the implementation of the socialization (figure 1). figure 1. survey of citarum watershed conditions preparation the material for making eco-bricks, before testing. the materials for making eco-bricks are came from waste in the citarum watershed, the waste that pollutes the citarum river is mostly inorganic or non-biodegradable, for example plastic, bottles or glass for drinks, plastic food wrappers, and so on. as we all know, plastic waste is very difficult to decompose, it will take more than 100 years for plastic to decompose completely. plastic waste is a source of environmental pollution in indonesia. the benefits of using plastic products must be balanced with the calculation of the resulting negative impacts [13]. the properties of this plastic material make it difficult to replace it with other materials for various applications, especially in everyday life, from food packaging, household appliances, children's toys, electronics to automotive components. the increase in the use of plastic materials has resulted in an increase in the production of plastic waste from year to year [6]. the civil and environmental science journal vol. 4, no. 1, pp. 022-029, 2021 25 problem that occurs in the lower part of the citarum river, especially in the karawang district, there are no landfills at several points, so that people throw their garbage carelessly, including into rivers. the ecovillage community consists of 15 rws with approximately 20 members, which are active communities in collecting organic and inorganic waste in the community (figure 2). however, the problem is the lack of knowledge from ecovillage members in recycling waste. one solution in this problem is by utilizing plastic waste that cannot be recycled as sustainable construction materials [14][15]. in making eco-bricks, before testing the materials are prepared to make eco-bricks with various predetermined variations. the steps to make an eco-bricks can be seen in figure 3. figure 2. waste sorting process in the community to start research on the first eco-bricks by conducting a literature review on the comparison of the results of the eco-bricks test object, it can be seen in table 1, after that making the test object, with consists of a plastic bottle with full plastic contents, a plastic bottle filled with sand, and a plastic bottle filled with plastic 20% and sand 80%, which is tested on the compressive strength of each specimen and the results are compared with the compressive strength of materials on the market such as bricks and concrete. after the specimen is ready to test comparison of 3 test specimens, each test object consisting plastic bottles with plastic filler (a), plastic bottle with sand + plastic filler (b), and plastic bottles with sand filler (c), (see table 2). table 2. eco-bricks specimen specimen quantity a plastic bottles (plastic contents) 1 b plastic bottles (plastic + sand) 1 c plastic bottles (sand filled) 1 eco-bricks research will conduct a compressive strength comparison of bricks (1) and concrete bricks (2), from each bricks and concrete bricks making consist of one test specimens (table 3), then each weight is measured (table 4). table 3. eco-bricks comparative specimen specimen quantity 1. bricks 1 2. concrete bricks 1 the steps for making an eco-brick (figure 4), first collect and separate plastic waste, prepare all kinds of plastic to make eco-bricks, second choose the same orchid and bottle size, you should use the most bottles in your environment. having an eco-brick in the same bottle makes it easy and embellishes the result, third use a wooden stick to tamp down metal, glass, which will damage the bottle. avoid civil and environmental science journal vol. 4, no. 1, pp. 022-029, 2021 26 paper and food scraps that will break down, and the last it is very important to ensure the quality of the eco-bricks made. weigh eco-bricks that have been made, eco-bricks are good if they weigh at least 35% of the volume of the bottle. in a 1500 ml bottle, the minimum weight is 500 grams, in a 600 ml bottle, the minimum weight is 200 grams. in table 4 is the weight of the eco-bricks made (figure 5). figure 4. making eco-bricks figure 5. measuring specimen weight table 4. specimen weight specimen specimen weight (gram) a plastic bottles (plastic contents) 290,1 b plastic bottles (plastic + sand) 855 c plastic bottles (sand filled) 1.047 3. result and discussion the results of the compressive strength test on the eco-bricks that have been made, when testing the position of the test object must be in a sleep state because for eco-bricks application in the field, the position used in the sleeping position is not the standing position [14]. figure 5. position when performing the compressive strength test [13] civil and environmental science journal vol. 4, no. 1, pp. 022-029, 2021 27 the eco-bricks that have been made is compressive strength test for each eco-brick variation, from the compressive strength test results will be displayed in the form of a bar chart, where the calculation to find the compressive strength is; compressive strength = p a (1) where: p = maximum load that will be given until a failure occurs (n) a = area (cm2) from the results of the eco-bricks test the compressive strength results obtained (figure 6), for specimen in table 2 figure 6. eco-bricks compressive strength the results of this research are used by university of pancasila team to socialize how to make ecobricks and how strong the pressure on the eco-bricks material. eco-bricks method is used to solve the problem of plastic waste along the citarum river. this socialization was held in tanjung mekar village, west karawang district, karawang regency. the participants come from eco-village communities to reduce plastic waste that cannot be recycled. from the results of tests that have been carried out on the compressive strength test, using the unit testing machine for the compressive strength test, it was see the strength of the eco-bricks when receiving a compressive load and to compare the compressive strength test against non-structural materials such as red bricks and concrete bricks and then the compressive strength test results from the eco-bricks were obtained. the highest compressive strength is 41.2 mpa from plastic bottle sand filled material, compared to the results of the compressive strength of red bricks is 27 mpa and concrete bricks is 38 mpa, the test can be respectively seen in figure 7, for its specimen in table (2) and (3). figure 7. eco-bricks compressive strength comparison civil and environmental science journal vol. 4, no. 1, pp. 022-029, 2021 28 from the results of testing shows eco-bricks has a higher compressive strength when compared with red bricks and concrete bricks. after a strong test of the test specimen, a successful failure of each test object was seen, shown in figure 8,9 and 10. figure 8. concrete bricks after the test were destroyed figure 9. red bricks after testing were destroyed figure 10. eco-bricks after testing are not being destroyed from figure 8,9 and 10 shows that eco-bricks are stronger in accepting the burden when compared to other materials. if eco-bricks are applied to non-structural, eco-bricks is able to withstand greater load, in this case earthquake, because when an earthquake occurs structural/non-structural damage that is destroyed can injure humans. 4. conclusions eco-bricks are the most effective solution to overcome the reduction of plastic waste that can damage the environment. from the compressive strength test results, eco-bricks which contains sand + plastic shows a higher result that is 41.2 mpa when compared with red bricks that is 27 mpa and the concrete bricks building is 38 mpa. eco-bricks are able to receive a greater burden than the bricks and concrete bricks. eco-bricks can be used as non-structural material. civil and environmental science journal vol. 4, no. 1, pp. 022-029, 2021 29 acknowledgements thanks to who have contributed and supported the implementation of this research process, especially to the lppm faculty of engineering, pancasila university for the funds that have been given for this research references [1] r. haribowo et al., “behavior of toxicity in river basins dominated by residential areas,” contemp. eng. sci., vol. 10, no. 7, pp. 305–315, 2017, doi: 10.12988/ces.2017.7116. [2] gaelle gourmelon, “global plastic production rises, recycling lags,” 2015. [3] world economi forum, “the new plastics economy rethinking the future of plastics,” 2016. [4] shuker, i.g., and s. . cadman, “marine debris,” in rapid assesment, no. april, 2018, p. 46. [5] l. b. singh, “manufacturing bricks from sand and waste plastics,” int. j. eng. technol. manag. appl. sci. www.ijetmas.com, vol. 5, no. 3, pp. 426–428, 2017. [6] s. u. dhote, “investigating the use of pet bottles as a sustainable material in construction,” int. j. res. advent technol., no. 2, pp. 13–16, 2016. [7] m. mokhtar et al., “application of plastic bottle as a wall structure for green house,” arpn j. eng. appl. sci., vol. x, no. x, pp. 1–5, 2015. [8] n. thirugnanasambantham, p. t. kumar, r. sujithra, r. selvaraman, and p. bharathi, “manufacturing and testing of plastic sand bricks,” int. j. sci. eng. res. (ij0ser), vol. 5, no. 4, pp. 1–6, 2017. [9] s. m. raj, m. n. gopal, t. p. kumar, g. g. prasath, and s. r. m. e, “an experimental study on the strength & characteristics of eco-bricks from garbage dump,” int. j. latest technol. eng. manag. appl. sci., vol. vii, no. iv, pp. 124–128, 2018. [10] m. s. priya and f. ash, “modern technique in fly ash bricks,” int. j. math. sci. eng. (ijmse), march 2014, vol. 3, no. 1, pp. 44–49, 2014. [11] s. a. kamble and d. m. karad, “plastic bricks,” int. j. adv. res. sci. eng., vol. 06, no. 04, pp. 134–138, 2017. [12] j. taaffe, s. o. sullivan, m. ekhlasur, and v. pakrashi, “experimental characterisation of polyethylene terephthalate ( pet ) bottle eco-bricks,” j. mater. des., vol. 60, pp. 50–56, 2014, doi: 10.1016/j.matdes.2014.03.045. [13] h. chandra, sunjonto, and sarto, “plastic recyling in indonesia by converting plastic wastes ( pet , hdpe , ldpe , and pp ) into plastic pellets,” plast. recycl. indones. by convert. plast. waste (pet, hdpe, ldpe pp) into plast. pellets, vol. 1, no. 1, pp. 65–72, 2015. [14] f. c.antico, g. araya-letelier, j. wiener, and r. gabriel, “eco-bricks : a sustainable substitute for construction materials eco-bricks : a sustainable substitute for construction materials ecoladrillos : un reemplazo sustentable de materiales de construcción,” rev. la constr., no. january 2018, 2017, doi: 10.7764/rdlc.16.3.518. [15] m. v. shoubi, m. v. shoubi, and a. s. barough, “investigating the application of plastic bottle as a sustainable material in the building construction,” int. j. sci. eng. technol. res., vol. 2, no. 1, pp. 28–34, 2013. civil and environmental science journal vol. iii, no. 02, pp. 072-083, 2020 72 drainage management study of the city of merauke towards inundation by rainfall luffi kusumabrata1*, ussy andawayanti2, ery suhartanto2 1 the department of public works and spatial planning, mappi regency, kepi, 99871, indonesia 2 water resources department, faculty of engineering, universitas brawijaya, malang, 65145, indonesia luffi.kusumabrata@gmail.com1 received 22-06-2020; accepted 02-08-2020 abstract. one problem that is often faced by the city of merauke as an urban area is inundation, which disrupts socio-economic activities and damages infrastructure in areas affected by inundation. the aim of this case study is to find ways to deal with inundation that occurs due to rainfall with return periods of 2 years, 5 years, 10 years, and 25 years. the inundation volume for the 2-year return period is zero, for the 5-year return period is 12.58 m3/sec with a height of 23.35 cm, for the 10-year return period is 18.57 m3/sec with a height of 25.63 cm, and for the 25-year return period is 20.22 m3/sec with a height of 27.75 cm. with the microsoft excel application, hydrological analysis was performed; spatial analysis using geographic information systems (gis) resulted in a map of the characteristics of the case study area, and with the storm water management model (swmm), hydraulics analysis was performed on existing drainage channels along with simulated management. keywords: rainfall, inundation, swmm, management. 1. introduction the city of merauke, with its occurring development, is experiencing problems of inundation in several areas due to rainfall runoff that cannot be accommodated by the drainage channels. in this regard, it is necessary to have good management to overcome the existing inundation [12, 18]. the analysis of these problems can be performed using geographic information systems (gis) and storm water management model (swmm) in order to show the amount of inundation that must be managed and alternatives for the management [1, 3, 4, 17]. the rate of development of the city in the direction of the rate of population development, every year requires open space which is converted into offices and settlements [2, 5, 6, 9]. with changes in existing land use, affecting the amount of surface runoff that occurs in the area [14, 15]. a reduced 1 cite this as: kusumabrata, l., andawayanti, u., & suhartanto, e. (2020). drainage management study of the city of merauke towards inundation by rainfall. civil and environmental science journal (civense), 3(2), 7283. doi: https://doi.org/10.21776/ub.civense.2020.00302.2 civil and environmental science journal vol. iii, no. 02, pp. 072-083, 2020 73 catchment area will increase the height of standing water at the ground surface due to rain [12]. from statistical data it is known that there was an increase in population from 2010 to 2014 [18]. dimension of the existing drainage channel is critical, unable to drain the existing runoff water to the river body again. the city of merauke 50 years ago experienced an inundation as high as one meter, and it has been handled well. but now back inundation occurs everywhere during the rainy season with an average inundation height of 20 cm. the current global climate change is also contributing to the high inundation in merauke city. rainfall with low intensity and with a long duration of 4 hours during the rainy season always occurs in each year [18]. the purpose of this study is to what forms of treatment can be done at the city of merauke drainage so that there is no puddle when it rains. 2. materials and methods this study involved the city of merauke, covering most of the mandala hamlet and a small portion of samkai hamlet, with a study area of 390 ha. figure 1. location of the city of merauke, papua. figure 2. location of the study area. 2.1. depth of problem this study does not involve the entire area of the city of merauke, but is limited to the area from the port to surrounding the mopah airport, which has many government facilities in addition to residential areas and is located in the middle of the city. 1. the obtained inundation height was based on rainfall with return periods of 2, 5, 10, and 25 years against existing land use, drainage channels, and topography. 2. in this study, the reviewed existing channel conditions were of the drainage channels that are present. 3. rainfall data was taken from one station, being the class iii meteorology station of mopah merauke. 4. analysis of the flow profile in the drainage channels utilized the swmm application. 5. spatial analysis of land use at the study location utilized arcgis. 6. sedimentation in channels was not included. 7. water quality was not included. 8. socio-economic impacts due to inundation were not included. civil and environmental science journal vol. iii, no. 02, pp. 072-083, 2020 74 in this study only two problems will be reviewed: a) what is the capability of existing drainage in managing inundation due to rainfall with return periods of 2, 5, 10, and 25 years? b) what should be the treatment for drainage that is not able to bear the burden of inundation due to rainfall with return periods of 2, 5, 10, and 25 years? by finding out the relationship pattern of rainfall in affecting drainage, the department of public works of merauke regency will have a better technical and systematic plan for management of inundation caused by rainfall. 2.2. theoretical basis one important matter in hydrological analysis is interpreting the probability of a future event based on hydrological data obtained from past records [13]. for this purpose, the concept of probability is utilized within analysis of hydrological data [7, 8, 10]: 𝑃 = 1 𝑇 (1) where: p = probability (%) t = return period (years) to find out the flooding or inundation occurring in an area, the hourly pattern of rain distribution is needed. if the available data are daily rainfall data, rain distribution models can be used to obtain the depth of hourly rainfall from the planned rain [19]. the alternating block method (abm) is an oftenutilized model. the planned hyetograph that results from this method consists of rain that occurs in a series of n consecutive time intervals with duration δt during time td (td = n δt) [14, 15]. the depth of the rainfall is obtained by multiplying the intensity of the rain by the duration of time (figure 3). figure 3. hyetograph rain intensity. the rational method is one of the oldest methods and was originally utilized only to estimate peak discharge [11]. the following is the basic equation of the rational method [14]: civil and environmental science journal vol. iii, no. 02, pp. 072-083, 2020 75 qp = c i a (2) where: qp = flood peak discharge (mm3/sec) c = flow coefficient i = rain intensity (mm/sec) a = catchment area (mm2) the drainage coefficient of an area of a with various topographic, soil, and vegetation conditions can be calculated by the following formula: 𝐶 = ∑ 𝐶𝑖𝐴𝑖 𝑛 𝑖=1 ∑ 𝐴𝑖 𝑛 𝑖=1 (3) the infiltration discharge of a shallow infiltration well with the condition that water is absorbed at the bottom of the well is calculated by the following formula [10, 11]: 𝑄0 = 5,5. 𝑅. 𝐾. 𝐻 (4) where: r = well radius (m) k = soil permeability coefficient (m/sec) h = water level in the well (m) the balance of water entering the well and seeping into the soil can be written down as the following formula [12, 13, 14]: 𝐻 = 𝑄 𝐹.𝐾 (1 − 𝑒 − 𝐹.𝐾.𝑇 𝜋.𝑅2 ) (5) where: h = water level in the well (m) f = geometric factor (m) q = incoming water discharge (m3/sec) t = flow time (seconds) k = soil permeability coefficient (m / sec) r = well radius (m) 2.3. methodology this study was conducted with the following steps, the first thing to do is gather information about problems that occur both from the community and related agencies. to be able to find out the causes of the problems that occur during the rainy season, hydrological data, map data and existing hydraulic drainage data are collected. from the data that has been collected, hydrological analysis, map analysis and hydraulics analysis are carried out to find out how much capacity the existing canal has in discharging rainwater flow. using the help of the swmm application tool, from the data that has been known, the value of the discharge flowing through the canal is calculated according to rainfall during 2 years, 5 years, 10 years and 25 years. by comparing the discharge capacity in the channel with the peak discharge due to rainfall in the channel, it is known in which channels that overflow occur and cause inundation in the area. if the channel discharge capacity is greater than the peak discharge, it means that the channel is safe and if the reverse means it requires handling to be safe. for channels that are not safe to channel peak discharge due to rainfall, a treatment plan is carried out with the help of the swmm application as a simulation tool, so that peak flow through the channel is smaller than the channel's discharge capacity. from the whole description above, it can be concluded what form of treatment is appropriate for the drainage channel (figure 4). civil and environmental science journal vol. iii, no. 02, pp. 072-083, 2020 76 figure 4. research methodology. 3. results and discussion 3.1. existing conditions of the study area the study area of the research has a variety of land use areas, which are dominated by residential areas, then shops and offices. the study area has a relatively flat topography, with slope variations ranging from 0.2% 1%. the case study area possesses city drainage channels throughout, but cases of inundation are still found in several surrounding areas. table 1. dimensions of existing channels channel existing channel (meter) channel existing channel (meter) channel existing channel (meter) wa wb d wa wb d wa wb d sal1 10.8 4 2.9 sal12 12.8 6 2.9 sal23 9.8 3 2.9 sal2 10.8 4 2.9 sal13 9.8 3 2.9 sal24 1.5 1.5 1.0 sal3 10.8 4 2.9 sal14 2.5 2.5 2.5 sal25 1.5 1.5 1.0 sal4 10.8 4 2.9 sal15 2.5 2.5 2.5 sal26 1.5 1.5 1.0 sal5 10.8 4 2.9 sal16 9.8 3 2.9 sal27 9.8 3 2.9 sal6 12.8 6 2.9 sal17 9.8 3 2.9 sal28 9.8 3 2.9 sal7 12.8 6 2.9 sal18 9.8 3 2.9 sal29 12.8 5 3.4 sal8 12.8 6 2.9 sal19 9.8 3 2.9 sal30 9.8 3 2.9 sal9 12.8 6 2.9 sal20 9.8 3 2.9 sal31 9.8 3 2.9 sal10 12.8 6 2.9 sal21 9.8 3 2.9 sal11 12.8 6 2.9 sal22 9.8 3 2.9 civil and environmental science journal vol. iii, no. 02, pp. 072-083, 2020 77 figure 5. map of the drainage network. the existing drainage channels have varying sizes and shapes of sections (figure 5). some channel sections are trapezoidal and others are rectangular sections, sal1 to sal13 are trapezoidal, sal14 and sal15 are square, sal16 to sal23 are trapezoidal, sal24 to sal26 are square, and sal27 to sal31 are trapezoidal (table 1). by hydrological analysis with daily rainfall data for 20 years, the maximum rainfall with return periods of 2, 5, 10, and 25 years were found. the duration of the return period has a linear relationship with the maximum rainfall that occurs. from the maximum rainfall for each return period, with the alternating block method (abm), input data was obtained in the form of planned rainfall, which is distributed in the form of hourly rain depths in the hyetograph. the existing condition of the study area with rainfall of a 2-year return period (117.92 mm/day) was safe, with no inundation and zero inundation volume; with rainfall of a 5-year return period (165.19 mm/day), inundation occurred with a volume of 12.583 m3/sec; with rainfall of a 10-year return period (200.18 mm/day), inundation occurred with a volume of 18.571 m3/sec; and with rainfall of a 25-year return period (248.58 mm/day), inundation occurred with a volume of 20.215 m3/sec. the civil and environmental science journal vol. iii, no. 02, pp. 072-083, 2020 78 amount of runoff varied according to the return period, with the runoff becoming greater as the value of the rainfall return period becomes greater. figure 6. modeling of sub-catchment areas, junctions, and conduits in the study area. from the data collected, in the form of existing hydraulic conditions in the field in the case study area of the existing network system is modeled in the smww application (figure 6). through the swmm application, runoff was found in some channels due to rainfall of various return periods as the peak discharge exceeded the channel capacities. a) with rainfall of a 2-year return period (117.92 mm/day), all drainage channels were safe and none of them overflowed. b) with rainfall of a 5-year return period (165.19 mm/day), there was overflow at sal9 = 3.127 m3/sec, sal10 = 2.752 m3/sec, sal11 = 2.492 m3/sec, sal12 = 3.550 m3/sec, sal24 = 0.078 m3/sec, sal25 = 0.258 m3/sec, and sal26 = 0.326 m3/sec. c) with rainfall of a 10-year return period (200.18 mm/day), there was an overflow at sal5 = 0.233 m3/sec, sal7 = 3.427 m3/sec, sal9 = 3.708 m3/sec, sal10 = 2.931 m3/sec, sal11 = 2.504 m3/sec, sal12 = 4.523 m3/sec, sal24 = 0.146 m3/sec, sal25 = 0.466 m3/sec, and sal26 = 0.633 m3/sec. d) with rainfall of a 25-year return period (248.58 mm/day), there was overflow at sal5 = 0.233 m3/sec, sal7 = 3.608 m3/sec, sal9 = 4.232 m3/sec, sal10 = 3.074 m3/sec, sal11 = 2.518 m3/sec, sal12 = 5.172 m3/sec, sal24 = 0.155 m3/sec, sal25 = 0.507 m3/sec, and sal26 = 0.716 m3/sec. 3.2. management the problem of inundation occurs in the upstream area, and therefore, management is carried out only in the upstream area, by changing the cross section of the channels and placing wells in areas along the channels that are unable to accommodate runoff. a. reduction of inundation volume with infiltration wells [16], with retaining walls placed on channel walls. civil and environmental science journal vol. iii, no. 02, pp. 072-083, 2020 79 it appears that overflow of water flow in several channels due to peak discharge due to rainfall exceeds the channel discharge capacity in channels sal7, sal9, sal10, sal11, sal12, sal24, sal25 and sal26 (table 2). table 2. summary of channel capacities for discharge channel existing qmax rainfall return period 2 5 10 25 sal1 33.304 2.104 3.145 3.948 5.090 sal2 33.304 3.046 4.503 5.627 7.237 sal3 33.304 5.408 8.029 10.057 13.146 sal4 33.304 8.535 12.773 16.065 21.540 sal5 33.304 11.789 17.759 22.418 30.680 sal6 44.962 14.887 22.568 28.521 40.196 sal7 44.962 17.539 26.824 33.299 46.230 sal8 44.962 16.946 25.840 32.531 43.754 sal9 44.962 24.726 36.542 45.568 48.381 sal10 44.962 24.833 36.781 45.919 48.442 sal11 44.962 24.781 36.693 45.793 47.849 sal12 44.962 25.573 37.895 47.308 50.511 sal13 38.215 2.817 4.163 5.178 6.777 sal14 12.182 0.192 0.831 0.876 0.857 sal15 12.182 2.142 3.898 3.963 4.388 sal16 38.215 1.921 2.111 1.985 1.920 sal17 38.215 1.431 1.987 2.367 3.416 sal18 38.215 3.896 5.483 6.643 9.560 sal19 38.215 5.313 7.428 9.000 13.181 sal20 38.215 3.218 4.072 4.551 7.990 sal21 38.215 1.782 2.221 2.427 3.924 sal22 38.215 0.963 1.204 1.286 1.578 sal23 38.215 0.362 0.528 1.297 2.282 sal24 1.877 0.084 0.835 1.590 1.912 sal25 1.877 0.241 1.032 1.828 2.385 sal26 1.877 0.311 1.132 1.951 2.594 sal27 38.215 0.597 1.537 2.447 3.386 sal28 38.215 0.991 2.097 3.130 4.505 sal29 72.618 1.215 1.848 2.828 4.455 sal30 38.215 0.550 1.270 2.115 3.394 sal31 38.215 7.964 10.750 12.621 21.225 maximum discharge of the channel (qcapacity) = 44.692 m 3/sec; discharge due to rainfall (qrainfall) = 46.524 m3/sec; inundation volume due to rainfall (qinundation) qinundation = qrainfall − qcapacity = 46.524 − 44.692 = 1.562 m3/sec diameter (d) = 1 m; depth (h) = 2 m; soil permeability (k) = 9.21 x 10-7 cm/sec = 9.21 x 10-9 m/sec; flow time (t) = 1 hour = 3600 seconds; form factor (f) civil and environmental science journal vol. iii, no. 02, pp. 072-083, 2020 80 f = 5.5 x r = 5.5 x ( 1 2 ) = 2.75 meters volume that can be absorbed by one well (qabs) qabs = f. k. h (1 − e − f.k.t π.r2 ) = 2.75 x (9.21x10−9) x 2 (1 − e − 2.72 x (9.21 x 10−9) x 3600 π x 0.52 ) = 0.00044 m3/sec needed number of wells (n) n = qinundation qabs = 1.562 0.00044 = 3551 wells to overcome the overflow in the drainage channel, sal7 needed 3551 wells, sal9 required 2481 wells, sal10 required 3176 wells, sal11 2254 wells, sal12 8863 wells, sal24 required 87 wells, sal25 needed 1157 wells, and sal26 needed 1628 wells. it can be seen that the number of wells needed is relatively large, due to the large absorptive capacity of the land in the city of merauke, other handling methods are needed to resolve the problem above. b. reduction of inundation by turning channels into long storage [16], by closing water gates to prevent intervention from the tides of the maro river. water is held to the channel capacity limits in the upstream, and the excess is channeled downstream; if the channels in the downstream are full, using a pump with a rate of 5 m3/sec, the water is discharged into the maro river. the cover dam on the channels utilizes a spillway or weir: weir length (l) = 1 meter; weir height (h) = 0.20 meters; length of channel (lsal) = 2192.67 meters; channel cross-sectional area (asal): asal = ( wa + wb 2 ) × d = ( 10.8 + 4 2 ) × 2.9 = 21.46 m2 the volume of water that can be accommodated by the channels as long storage (vstor) vstor = lsal × asal = 2192.67 × 21.46 = 47054.70 m3 civil and environmental science journal vol. iii, no. 02, pp. 072-083, 2020 81 the storage volume of 47,054.70 m3 is greater than 36,792 m3, and thus the channels functioning as storage can safely accommodate the existing discharge. discharge flowing in the spillway or weir (qwe): qwe = c × l × h 3 2 = 3.33 × 1 × 0.2 3 2 = 0.298 m3/sec figure 7. map of management plan with channels as storage. the treatment plan is modeled into the swmm application and then executed to check the volume of the peak discharge in each channel. the results of executing modeling in the swmm application by placing the cover dam at several points according to the plan, along with the 5 m3/sec pump to aid in storage draining, are shown in the following table; peak discharge that exceeds the channel capacity was not indicated. the burden of downstream water flow seems large because it carries the burden from upstream, seeing the capacity of the channel that is in the upstream there is a large discharge difference. by installing civil and environmental science journal vol. iii, no. 02, pp. 072-083, 2020 82 cover dam at points 04, 06, 08, 23, 24, 29, the volume of water is held back for some time, not directly flowing from upstream to downstream. in cover dam construction, overflow is installed with an overflow to dispose of water volume that exceeds the channel storage capacity (figure 7). problems that occur on channels sal5, sal7, sal10, sal11, sal12, sal24, sal25 and sal26 can be solved properly using this method, for the dimensions of the channel with handling and at which control points that need to be installed cover dam (figure 7). 4. conclusion from the results of the analysis, it can be concluded for the study area that for rainfall, the existing drainage channel is able to accommodate the flow load of rainfall with a 2-year return period and there is no inundation, but for rainfall with 5-year, 10-year, and 25-year return periods, there is inundation. the inundation volume for a 5-year return period is 12.58 m3/sec with a height of 23.35 cm, for a 10-year return period is 18.57 m3/sec with a height of 25.63 cm, and for a 25-year return period is 20.22 m3/sec with a height of 27.75 cm. the inundation caused by rainfall can be managed by utilizing drainage channels as long storage. at the outlet point, when the rain falls, the gate is to be fully closed to make it easy to control the flow of water due to rainfall and prevent interference from the tides of the maro river. the water from the upstream should be retained as much as possible first to prevent exceeding the capacity of the channel, by installing a cover dam with a pump of 5 m3/sec capacity. when the water in the maro river recedes, drainage channels from upstream to downstream are then drained with the help of a pump. the construction of water structures in the city of merauke requires materials to be brought in from other regions since there are no available local materials, making it expensive. the existing problem cannot be resolved within one term of office (5 years) of the regional chief; it must be worked on continuously from the period of one chief to the next. the policy direction of the central government in making the city of merauke the capital of the province of south papua needs to be followed up with the development direction for the area to minimize the risk of failure of water structures. this means that anticipation of the cause of city flooding must refer to a large planned value, with usage of the 25-year return period among the four periods examined in this study for handling floods. references [1] s. boonya-aroonnet, “applications of the innovative modelling of urban surface flooding in the uk case studies,” 11th international conference on urban drainage, edinburgh, scotland, uk, 2008. [2] akajiaku c. chukwuocha, ngozi b. ac-c chukwuocha, nigeria, “geographic information systems based urban drainage efficiency factors,” department of surveying and geoinformatics, federal university of technology, owerri, owerri,sofia, bulgaria, 17-21 may 2015 [3] daniel jato-espino, susanne m. charlesworth, joseba r. bayon, frank warwick, “rainfall– runoff simulations to assess the potential of suds for mitigating flooding in highly urbanized catchments,” int. j. environ. res. public health, 13, 149, 2016. [4] m.coskun, n. musaoglu, “investigation of rainfallrunoff modelling of the van lake catchment by using remote sensing and gis integration,” itu, civil engineering faculty, 34469 maslak istanbul, turkey istanbul. [5] f. de smedt, l. yongbo and s. gebremeskel,” hydrologic modelling on a catchment scale using gis and remote sensed land use information,” department of hydrology and hydraulic engineering, free university brussels, belgium, southampton, boston: 295-304, 2000. [6] lothar fuchs, thomas beeneken, martin lindenberg,” use of geographic information systems for flooding analysis in urban drainage,” proceedings of the federated conference on computer science and information systems, pp. 627–631, 2012. civil and environmental science journal vol. iii, no. 02, pp. 072-083, 2020 83 [7] x. wanga, x. gub, z. wub, c. wangc,” simulation of flood inundation of guiyang city using remote sensing, gis and hydrologic model,” the international archives of the photogrammetry, remote sensing and spatial information sciences. vol. xxxvii. part b8. beijing 2008. [8] j. bhaskar, c.r. suribabu,” estimation of surface run-off for urban area using integrated remote sensing and gis approach,” jordan journal of civil engineering, volume 8, no. 1, 2014. [9] m. kh. askar,” rainfall-runoff model using the scs-cn method and geographic information systems a case study of gomal river watershed,” wit transactions on ecology and the environment, vol 178, 2014. [10] boonya-aroonnet s, maksimović č, prodanović d, djordjević s,” urban pluvial flooding: development of gis based pathway model for surface flooding and interface with surcharged sewer model,” novatech 2007. [11] chow, v.t., “open channel hydraulics”, by mcgraw-hill book company, inc., 1959. [12] kodoatie, robert j. dan roestam, “tata ruang air [water spatial planning]”, penerbit andi, 2010. [13] soewarno, “hidrologi aplikasi metode statistik untuk analisa data jilid 1 [hydrological applications of statistical methods for data analysis, part 1]”, penerbit nova, 1995. [14] soewarno, “hidrologi aplikasi metode statistik untuk analisa data jilid 2 [hydrological applications of statistical methods for data analysis, part 2]”, penerbit nova, 1995. [15] sumarto, c.d., “hidrologi teknik [hydrology engineering]”, penerbit usaha nasional, 1987. [16] suripin, “sistem drainase perkotaan yang berkelanjutan [sustainable urban drainage systems]”, penerbit andi, 2004. [17] solikin solikin, ery suhartanto, riyanto haribowo. 2017. analisis penanganan genangan pada wilayah kota banjarmasin. jurnal teknik pengairan 8 (1), 15-25. [18] the department of public works of merauke regency, 2016 [19] khaerudin, d., primantyo, a., & rahardika, r. (2019). determining infiltration rate from infiltration measurement with flooding method by turftech infiltrometer. civil and environmental science journal, 2(1), pp.35-43. doi:https://doi.org/10.21776/ub.civense.2019.00104 open access proceedings journal of physics: conference series civil and environmental science journal vol. i, no. 01, pp. 034-040, 2018 34 the application of modal split using revealed and stated preference techniques: a study in malang muhammad nurjati hidayat1 1 water resources engineering department, universitas brawijaya, malang, 65145, indonesia muhammadhidayat@ub.ac.id received 05-02-2018; revised 29-03-2018; accepted 08-04-2018 abstract. in this study we investigate modal split and travel behaviour in malang by conducting person trip survey in study area. the purpose is to understand respondents’ travel behaviour and their preferences in selecting mode of transport. this is carried out to understand what are respondents feel regarding their perception on mode of transportation that available to them. the data being used are revealed preference (rp) and stated preference (sp) data. the first data based on present situation of respondents (including respondents’ characteristics and daily travel information), while the second one is hypothetical scenario that has not available in present condition. these data then compared and analysed using multinomial logit model (mnl). keywords: travel behaviour, revealed preference, stated preference, multinomial logit model 1. introduction in modelling travel demand, actual behaviour of user usually estimated using revealed preference (rp) data by employing discrete choice analysis (e.g. ben-akiva and lerman [1]). however, rp data may have shortage in estimating individual choice due to the following reasons [2]: preferences for non-existing services are not provided in rp data the set of alternatives considered by an individual may be ambiguous there are some errors in estimating service attributes there are similarities in attributes or lack of variability, or both in order to lighten those drawbacks, a survey with hypothetical choice scenario and fully controlled alternatives need to be done. it called stated preference data that widely used by researchers for travel demand [3] and [4], and also in marketing research [5], as well. this paper investigates the idea of using rp and sp data simultaneously because they have complementary characteristics. unknown reliability of sp data is explicitly considered and its objective is to yield more reliable travel demand model on combining rp and sp data rather than analysing rp and sp data separately. the key features of this method are bias identification (the effect of new services that are not recognizable by individual in rp data), efficiency (all preferences on available data is jointly estimated), and bias correction [6]. in rp data, trade-offs among certain attribute cannot be estimated accurately. for example, the correlation between travel cost and travel time in rp data may resulting insignificant parameter civil and environmental science journal vol. i, no. 01, pp. 034-040, 2018 35 estimates for their coefficients. however, an sp survey designed based on little or low correlation between these attributes may presenting additional information on their trade-offs. the aim of this paper is to perform the effectiveness of the combined rp/sp estimation method by an application to predict the mode choice in malang (east java) if new mode of transport is introduced. 2. material and methods 2.1. study area this research located in malang city (urban area) and malang regency (rural area) which is unified in greater malang territory (batu city excluded in this research). malang is the second biggest city in east java having population of 820,243 residents, while malang regency having 2,459,982 residents. total area is 110.06 and 3,534.86 km2, respectively. government planning to introduce commuter train as a new public transportation in order to reduce the congestion level. another reason is there is no public transport that connects directly from northern to southern part of malang. by using the current transportation, it would take longer time rather than using private vehicle. on the ground of those reasons, the study of travel demand is needed. 2.2. modelling approach discrete choice model is a technique in which decision makers choose an alternative from choice set of available alternatives. it identifying pattern made by an individual facing available choice set. discrete choice model postulates that the probability of individual choosing an alternative is based on their socioeconomics and level of attractiveness to the alternative. to represent the attractiveness of the alternative the utility function is constructed. generally, utility derived from individual characteristics. utility is value indicator for an individual, which, generally, derived from the attributes of alternatives or sets of alternatives. the utility theory states that an individual will select an alternative in choice set that maximize his/her utility. the theory states that it contains function of attributes of alternative and individual characteristics[7]. in the newest study, the decision utility (mode choice) could be affected by characteristics the built environment (diversity, design and density) and travel modes (travel cost and time)[8]. the utility function, u, has a property that an alternative is chosen if its utility is greater than utility of other alternatives in individual’s choice set. this function can be expressed as: 𝑈𝑖𝑛 ≥ 𝑈𝑗𝑛, ∀𝑗 ∈ 𝐶𝑛, 𝑖 ≠ j (1) 𝑈𝑖𝑛 = 𝑉𝑖𝑛 + 𝜀𝑖𝑛 (2) which could be interpreted as the utility of alternative i for individual n is greater or equal to alternative j in individual’s choice set. utility function can be represented by two components: an observable or representative part vin which is a function of the measured attribute, and a random term ε which reflect unobservable part of individual and also error made by modeler. two individuals with same attribute, x, in observable part and having the same choice set probably select different choice, and some individual may not always choose the best alternative. 2.3. model specification rp and sp model types are considered. the rp model reflecting behaviour of individual explained in utility function, whereas sp model is the result of sp response. suppose mode choice model utility function for rp model with following equation: 𝑈𝑖𝑛 𝑅𝑃 = 𝑣𝑖𝑛 𝑅𝑃 + 𝜀𝑖 𝑅𝑃 = 𝛼′𝑤𝑖 𝑅𝑃 + 𝛽′𝑥𝑖 𝑅𝑃 + 𝜀𝑖 𝑅𝑃 (3) and the choice of decision maker given by: civil and environmental science journal vol. i, no. 01, pp. 034-040, 2018 36 𝑑𝑖𝑛 𝑅𝑃 = { 1, if 𝑈𝑖 = max𝑗=1, . . , i{𝑈𝑖 } 0, otherwise (4) where i = 1, . . , i is number of alternatives; wi and xi are vector of attributes of alternative; α and β are parameter to be estimated; and ɛi is error term. similar to utility function of rp model, the utility function of sp model is: 𝑈𝑖𝑛 𝑆𝑃 = 𝑣𝑖𝑛 𝑆𝑃 + 𝜀𝑖 𝑆𝑃 = 𝛽′𝑥𝑖 𝑆𝑃 + 𝛾 ′𝑧𝑖 𝑆𝑃 + 𝜀𝑖 𝑆𝑃 (5) and the choice of decision maker given by: 𝑑𝑖𝑛 𝑆𝑃 = { 1, if 𝑈𝑠 = max𝑗=1, . . , i{𝑈𝑖 } 0, otherwise (6) from the framework above we assume that sp response is the most preferable alternative chosen by respondent. thus we have equation as follow: 𝑈𝑐𝑛 ≥ 𝑈𝑎𝑛 (7) 𝑈𝑡𝑛 ≥ 𝑈𝑐𝑛 (8) the subscripts c, a, and t represent the current mode, alternative mode, and commuter train, respectively. the term 𝑥𝑖 𝑅𝑃 and 𝑥𝑖 𝑆𝑃 in both model implies the common variable in rp and sp model and term γ’z is specific to sp model that may contain sp biases. the level of random noise in rp and sp data is presented by the variance of the disturbance term ε. if the data source has different noise level, it can be shown as follow: var(𝜀𝑖𝑛 𝑅𝑃 ) = 𝜇2var(𝜀𝑖𝑛 𝑆𝑃 ), ∀𝑖, 𝑛 (9) with the framework described above, the choice probability of alternative using multinomial logit model can be expressed as follow: 𝑃𝑛(𝑖) = 𝑒xp(𝑣𝑖𝑛) ∑ 𝑒xp(𝑣𝑗𝑛) 𝐼𝑛 𝑗=1 (10) 2.4. combination of rp/sp models since our concern is actual behaviour of respondents, prediction only using rp model. hence, utility component being used is: 𝑣𝑖𝑛 = �̂� ′𝑥𝑖𝑛 + �̂� ′𝑤𝑖𝑛 (11) note that �̂� is calculated using both rp and sp data. in sp questions, hypothetical services are to be included for predicting demand, thus the term in sp model will be: 𝑣𝑖𝑛 = �̂� ′𝑥𝑖𝑛 + �̂� ′𝑤𝑖𝑛 + +�̂� ′𝑧�̅�𝑛 (12) where 𝑧�̅�𝑛 represents hypothetical attributes related to the policy changes and �̂� ′is an estimation on parameter of 𝑧�̅�𝑛. in equation above, rp and sp utility can be combined because new scale parameter (µ) is introduced with the purpose to adjust rp and sp scale parameters. 3. result and discussion 3.1. field survey in this research we conducting two times survey, namely: preliminary survey and primary survey. the first survey conducted to ensure the population is being sampled, evaluate the questionnaire, and civil and environmental science journal vol. i, no. 01, pp. 034-040, 2018 37 the result is being evaluated. this survey also helps to avoid the problem of collecting large of useless or incorrect data in primary survey because of ineffective constructing questionnaire and improper sampling preparation. this survey targeting car, microbus, motorbike, and train users with 80 respondents. 20 passengers interviewed each of those modes, thus we understand their trip behaviour. private vehicle (car and motorbike) users were interviewed in gas station, traffic light or when the user stops near the streets. microbus users interviewed on-board and the rests was sampling people on train stations. the second survey, primary survey, was conducted with small revision from preliminary survey. the sample being taken in this survey is 360 respondents for car, microbus, and motorbike. we eliminate train user because in preliminary survey there were only few respondents who use train as their mode for working purpose. 3.2. result the survey result is displayed in table 1. number of respondent who travelled from lawang or kepanjen to city center is dominated by male (61%) compared to female (39%). sequentially, the age of respondents are 25-45 years old (58%), 46-65 years old (22%), less than 25 years old (19%), and more than 65 years old (1%). the occupation of respondent is dominated by businessman (47%) and followed by entrepreneur (18%), civil servant (16%), student (10%), house wife and etcetera have same proportion, that are 4%, part timer has very small proportion (1%). number of commute in a week conducted by respondents are 7 times a week (58%), 5 times (20%), more than 7 times (15%), and 3 times (7%). by taking notice to respondent who majority have job as businessman, probably there is correlation between occupation and number of commute in a week, that is 7 times a week. respondents’ trip characteristics and level of service of transport facilities are shown as follow. the reason respondent not using public transportation dominated by long travel time (37%) followed by long waiting time (21%), uncomfortable (20%), having far access from home (11%), travel cost is expensive (11%), and etcetera (5%). table 1. the result of respondents’ characteristics item range % item range % sex male 61 vehicle ownership (%) motorbike 70 female 39 car 30 age < 25 19 income (usd) < 88 29 25 45 58 88 177 27 46 65 22 >177 44 65 > 1 people in group 1 67 occupation civil servant 16 3-feb 23 entrepreneur 18 >3 10 businessman 47 reason not using public transport long travel time 37 student 10 expensive 11 part timer 1 uncomfortable 20 house wife 4 far access 11 others 4 long waiting time 21 last education elementary school 7 frequency per week ≤3 7 junior high school 14 5 20 senior high school 45 7 58 university 27 >7 15 post graduate 5 others 3 civil and environmental science journal vol. i, no. 01, pp. 034-040, 2018 38 table 2. respondents current and alternative mode and their income from table 2 we can relate that respondents whom using car as their current mode prefers to use microbus and motorbike as their alternative mode are 19% and 80%, respectively. for microbus user, their alternative modes are car (2%) and motorbike (69%), while motorbike user prefers car (10%) and microbus (52%) as their alternative modes. diagonally, we can see that there are respondents answered the alternative mode exactly the same as current mode, i.e. car respondent using car as their alternative, microbus respondent using microbus as their alternative and motorbike user using motorbike as their alternative. they are categorized as captive respondent, that is respondent who has no any alternative mode if current mode cannot be used. similar to the current mode of respondent over the alternative mode, income of respondents affecting modal choice preferences. from survey result, 80% of car respondent have high-income. middle and high-income for motorbike respondent have almost identical numbers, that are 51 and 55 respondents, respectively. in contrary, microbus respondents have the opposite result of income. majority of microbus user is a low-income respondent, which is 64 respondents (55%). afterwards, we could say that car user who uses motorbike as their alternative mode of transport is high-income respondent. microbus user who categorized as captive respondent are middle-income. only few microbus users who uses car categorized as high-income respondent. motorbike respondent who uses microbus as their alternative mode mostly are middle-income respondent. high-income motorbike users mostly are captive respondent. 3.3. rp/sp model estimation three models were estimated: rp model, sp model and rp/sp model using multinomial logit (mnl) model, each of which was estimated by maximizing the log-likelihood function. in order to ease the explanation, artificial tree structure has been made. given the way the data was collected, the structure in figure 1 should represent these condition appropriately. figure 1. the artificial tree structure current mode alternative mode income car microbus motorbike total low income middle income high income total car 39 19 80 138 12 16 110 138 microbus 2 46 69 117 64 38 15 117 motorbike 10 52 83 145 39 51 55 145 total 51 117 232 400 115 105 180 400 civil and environmental science journal vol. i, no. 01, pp. 034-040, 2018 39 table 3. the result from estimation data rp model sp model rpsp model constantcar 2.155 (5.97) 1.201 (12.85) constantbus 1.089 (1.59) 0.953 (3.99) constanttrain 3.214 (7.75) 0.267 (10.59) cost 0.008 (2.04) -0.061 (-10.81) -0.005 (-11.27) time -2.927 (-2.68) -3.843 (-7.05) -0.302 (-6.93) age 0.025 (1.33) -0.013 (-2.72) 0.0168 (2.65) sex -1.381 (-3.46) 0.345 (3.22) -0.904 (-6.23) frequencytrain 0.123 (10.88) 0.0098 (9.59) income -0.144 (-1.71) 0.013 (0.96) -0.121 (-4.45) μ 11.682 (10.38) ρ2 0.744 0.164 0.408 n 400 2000 2000 from rp data, a binary choice data set was created by regarding the current mode and the alternative mode as the first and the second options of chosen mode. the data set consist of 400 respondents, after eliminating incomplete and data error. in this data set, data collected only available in two alternatives, namely the current mode and the alternative mode. the current mode is the mode that respondent used every day for commuter trip, while the alternative mode is his/her alternative mode if the current mode is cannot be used. the current and alternative mode considered as the best choice or have the highest utility for respondent from the choice set. the estimation of rp, sp and rp/sp model presented in table 3. not all models having correct signs due to some errors. cost variable has sign that should not be positive. logically, cost variable should have negative sign which means the higher the travel cost, the most likely respondent not using the current mode as their transport mode. the explanation of positive sign in cost variable could be as follow: 1. there is a correlation between distance and travel fare. the longer the distance of the travel, the higher travel fare should be paid by respondent 2. the current mode has higher cost than the alternative mode. the expensive current mode is the product of the number of respondent who have travel expenses using the current mode higher than the alternative mode divided by number of non-captive respondents and multiplied by hundred to obtain the results in percentage. captive respondent excluded in the calculation because there is no significant difference in travel cost. 3. there were mistakes in translating questionnaire form from english version into indonesian version before distribute it to surveyor. as for sp model, stated preference or stated intention of using the new commuter train were employed to create binary choice data. if the respondents have willingness or intention to switch mode using commuter train, he or she is considered to have chosen the commuter train over the current mode he/she currently used. otherwise, the respondent is considered to choosing the currently mode they used over the commuter train. thus, a binary choice can be created. in the data, each respondent facing five different level of services of new commuter train. with number of observation of 2000, respondent will accept and have intention to use new commuter train if the level of service match his/her condition. commuter train constant is introduced in the model so that it may capture the attributes of new commuter train that are not include in the model and response bias toward the new commuter train. the commuter train constant has a significant positive coefficient, probably reflect the overstated use of the commuter train. civil and environmental science journal vol. i, no. 01, pp. 034-040, 2018 40 the last model is combined rp/sp model. the framework is shown in equation (3) to (9). due to the difference in variance of rp and sp data, variable µ is employed. the value of scale parameter µ is expected to be less than one. if scale parameter µ has value less than one, it scales down the explanatory variables in the stated preference model because sp model has more random noise than rp model. however, if the µ value greater than one, the rp model has more random noise. the estimation results of rp/sp model are shown in the third column of table 3. it shows that train frequency has positive coefficient. the results also show that µ has estimated value greater than 1. this probably because of the errors obtained from rp data explained previously. the value more than 1 scales up the sp model. the estimation of rp/sp model is almost similar to rp model which indicate that the joint estimation successfully replicates the rp model, except in variable cost. 4. conclusions the combined estimation of discrete choice models from rp and sp data was presented. the strategy combining both types of data can benefit with explicit consideration of their merit and demerit. the case study is modal split model under hypothetical scenario, namely introducing commuter train as new alternative. in estimating rp and sp data simultaneously to estimate the mode choice model, alternative specific constant was estimated separately. in modelling using mnl model, the most significant model from rp model, sp model and combined rp/sp model is rp/sp model than other models alone. combining rp data with sp data increase the accuracy of parameter estimates in the model. in our result shows that rp model contain more random noise than sp model. to perform this model in real condition, more data need to be collected, such as number of passenger for each mode and od table, thus the probability for each mode can be calculated. from academic point of view, this research need more advanced model such as nested logit (nl), cross nested logit (cnl), generalized nested logit (gnl) to resulting higher quality in estimation and research due to the estimated modes are able to categorized in private vehicle and public transport. references [1] m. ben-akiva and s. r. lerman, discrete choice analysis: theory and application to travel demand. mit press, 1985. [2] t. morikawa, m. ben-akiva, and k. yamada, “forecasting intercity rail ridership using revealed preference and stated preference data,” transp. res. rec., vol. 1328, pp. 30–35, 1991. [3] j. j. louviere et al., “laboratory-simulation versus revealed-preference,” transp. res. rec. 794, pp. 42–51, 1981. [4] d. a. hensher, p. o. barnhard, and t. p. truong, “the role of stated preference methods in studies of travel choice,” j. transp. econ. policy, vol. 22, no. 1, pp. 45–58, 1988. [5] p. cattin and d. r. wittink, “commercial use of conjoint analysis: a survey,” source j. mark., vol. 46, no. 3, pp. 44–53, 1982. [6] m. ben-akiva et al., “combining revealed and stated preferences data,” mark. lett., vol. 5, no. 4, pp. 335–349, 1994. [7] t. a. domencich and d. mcfadden, urban travel demand: a behavioral analysis. amsterdam and oxford, 1975. [8] j. de vos, p. l. mokhtarian, t. schwanen, v. van acker, and f. witlox, “travel mode choice and travel satisfaction: bridging the gap between decision utility and experienced utility,” transportation (amst)., vol. 43, no. 5, pp. 771–796, 2016. open access proceedings journal of physics: conference series civil and environmental science journal vol. iii, no. 01, pp. 018-030, 2020 ol. xx, no. xx, pp. xxx-xxx, 20xx 18 hydrological analysis of trmm (tropical rainfall measuring mission) data in lesti sub watershed1 suryaningtyas lufi1, suhartanto ery2, rispiningtati2 1hydrology department, pt saka buana yasa selaras, banjarmasin, 70236, indonesia 2water resources engineering department, universitas brawijaya, malang, 65145, indonesia lufisuryaningtyas@gmail.com received 19-12-2019; accepted 02-03-2020 abstract. alternative solution for availability of inadequate rain data as input to hydrological data is with the assist of tropical rainfall measurement mission (trmm) satellite rainfall data which using remote sensing technology (satellite). the purpose of this study is to look for correlations and data corrections and validate trmm satellite data with rainfall data at the rain station and discharge observation data. lesti sub-watershed is used as a case study with consideration of the data availability that is considered sufficient. the validation results of corrected trmm rain data produce nash-sutcliffe efficiency (nse), root mean squared error (rmse), correlation coefficient (r), and relative error (kr). then, conducted an analysis of the flow discharge estimation using trmm rainfall data and validated with tawangrejeni automatic water level record (awlr) data. the results of flow discharge validation using the fj mock method produce an nse value of 0.507, rmse 19.383, correlation coefficient (r) 0.713, and relative error of 0.001. overall analysis shows trmm data can be used as an alternative of the rain data that is used to estimate flow discharge, but the result of flow discharge analysis is still better using rainfall data from the rain station post. keywords: rainfall, trmm, rain station post, validation, flow discharge, fj mock 1. introduction the rainfall data information is very important for various analyzes of water resources. rainfall data can be in the form of temporal (time series) or spatial [9]. as one of the important data in hydrological analysis, rainfall data obtained from measurements at the rain station post, so that the rainfall data obtained are expected to have sufficient accuracy. rainfall data in time series recording can provide trend information from the nature of rain in a place whether it has increased or vice versa. from this description can be said that rainfall data is climatological data that is quite important. accurate and timely observations and estimates of regional and global precipitation are crucial for various researches and applications [6]. 1 cite this as: suryaningtyas, l., ery, s., & rispiningtati, r. (2020). hydrological analysis of trmm (tropical rainfall measuring mission) data in lesti sub watershed. civil and environmental science journal, 3(1), pp.18-30. doi: https://doi.org/10.21776/ub.civense.2020.00301.3 civil and environmental science journal vol. iii, no. 01, pp. 018-030, 2020 ol. xx, no. xx, pp. xxx-xxx, 20xx 19 in fact to obtain the representative rainfall observation data namely both in terms of quality and quantity or length of its observation data that quite appropriate with the requirements is very difficult. the difficulty to get rainfall data, due to the limited number of measuring devices or gauge especially in remote areas, so that it will be difficult to conduct studies and analysis of water resources based on rainfall data in a place because not all places have rainfall monitoring stations manually or automatically [8]. according to syaifullah [9], the latest technological development, namely in the form of satellite technology (remote sensing) is able to make a breakthrough in terms of the acquisition of rainfall information (precipitation) because with remote sensing technology now has been able to conduct precipitation measurement from remote distance. areas that do not have sufficient rain recording stations are almost impossible to measure rainfall, but with this technology it is possible to obtain precipitation data that is not limited in space and time, so that it can simply be said that with satellite technology rainfall data can be obtained anytime and anywhere. tropical rainfall measuring mission (trmm) satellite has achieved some research progress since its launch in 1997 [1]. trmm satellite was launched in november 1997 and has been producing since 1998 [3]. one of the satellite technology that has been developed is the trmm meteorological satellite, which has two types of data namely trmm nasa (3b42rt) developed by national aeronautics and space administration and trmm jaxa (gsmap_nrt) developed by japan aerospace exploration agency (jaxa), which its results in the form of rainfall data (precipitation) that occurs in the atmosphere with a certain spatial resolution and within period of 3 hours, daily or monthly [9]. considering that, then it is necessary to conduct evaluation whether the rainfall data from the trmm satellite and from the existing rain station post network will produce maximum information so that can be obtained the magnitude of rainfall at all points with sufficient accuracy or even differ greatly. in the lesti sub watershed with an area of 381,21 km2 and has five closest rain stations with the uneven position of the rain station post. this study will examine how the correlation of the rainfall station post data towards the satellite rainfall data. this analysis is carried out in an effort to get the value of correlation and accuracy in the results of the analysis of flow discharge estimation using rainfall data at the observation station and satellite rainfall. 2. materials and methods 2.1 materials data needed for this analysis, namely data of rain station coordinate, dem, topographic map and river network map, daily rainfall data from the 5 closest rain stations in the lesti sub-watershed for 17 years (2002-2018), trmm rainfall data per 3 hours (trmm_3b42rt v7), tawangrejeni awlr discharge data for 12 years (2007-2018), and lesti sub watershed land use data. 2.2 method 2.2.1. hydrological analysis consistency test data consistency test is carried out to find out whether there is any deviation in the available rainfall data, so that it can be known whether the data is suitable to be used in further hydrological analysis or not. in this study 2 (two) methods were performed, namely (1) double mass curves; (2) rescaled adjusted partial sums (raps) [7]. homogeneity test a series of hydrological data that is presented chronologically as a function of the same time is called a periodic series. the field data that published in general are discharge data, rainfall data, and others. data is arranged in a series of periodic forms, so that before used for further analysis must be tested. civil and environmental science journal vol. iii, no. 01, pp. 018-030, 2020 ol. xx, no. xx, pp. xxx-xxx, 20xx 20 the data testing intended are: (1) test for no trend; (2) stationary test; (3) persistence test. the three stages of testing are often referred to as data filtering. 2.2.2 thiessen polygon method rain station post rainfall data that will be used in the form of regional average rainfall data which calculated using the thiessen polygon method. 2.2.3 trmm rainfall data validation test for validation test, using the method of nash-sutcliffe efficiency (nse), correlation coefficient (r), root mean squared error (rmse), and relative error (re). there are two validation analysis performed, namely validation of uncorrected trmm data and validation of corrected trmm data [5]. validation of uncorrected trmm data using rain station post rainfall data and uncorrected trmm. the periods used are monthly with a data length of 7 years (2011-2018), 4 years (2014-2018), 1 year (2018). as for the corrected trmm data validation conducted a number of processes first, namely calibration, verification, and validation. calibration and verification using the scatter plot method. for calibration used monthly periods with data length of 10 years (2002-2011), 13 years (2002-2014) and 16 years (2002-2017). while the verification and validation test uses a monthly period with a data length of 7 years (2011-2018), 4 years (2014-2018), 1 year (2018), excluding calibration years. 2.2.4. analysis of rain data into flow discharge with f.j. mock method analysis of rainfall data into flow discharge in this study uses the mock method which in principle takes into account water balance above the surface and water balance in the ground (groundwater) which is affected by rain, soil type and climate [2, 4]. as for the data used in the flow discharge analysis using the fj mock method, among others: 1. results of the regional average rainfall analysis in lesti sub watershed in 2007 2008 2. trmm rainfall data before being corrected and after being corrected in 2007-2018 3. tawangrejeni awlr discharge recording data for 2007-2018 4. data on climate recording at karangploso climatology station in 2007-2018, as for the measured data needed are : t = monthly average temperature (oc) rh = monthly average relative humidity (%) n/n = monthly sun brightness (%) u = monthly average wind speed (m/sec) 5. coordinate data of the observation point namely the point where awlr tawangrejeni is located. ll = latitude location of location being reviewed 6. the initial storage value is obtained by trial and error 7. the initial groundwater storage value is obtained by trial and error after obtaining the f.j mock discharge value with the rain station post data, trmm before and after corrected, the discharge data is analyzed its validation with awlr discharge data using the method of nash-sutcliffe efficiency (nse), correlation coefficient (r), root mean squared error (rmse), and relative error (re). as for the validation method formula used in this study, namely: 1. nash-sutcliffe efficiency (nse) this method shows how well the plot of the observation value (measurement) is compared to the prediction-simulation value, according to the 1: 1 line, with a range of values ∞ to 1. in other words, the closer to 1, then the better the nse value. civil and environmental science journal vol. iii, no. 01, pp. 018-030, 2020 ol. xx, no. xx, pp. xxx-xxx, 20xx 21 nse = 2 1 2 )( )( 1 ii n i ii xx yx − − −  = (1) with: xi = observation data (actual data) yi = estimation data (estimation result data) xi = average observation data n = the number of data table 1. criteria of nash-sutcliffe efficiency (nse) value nse value interpretation nse > 0.75 good 0.36 < nse < 0.75 qualified nse <0.36 not qualified 2. correlation coefficient the purpose of this analysis is to obtain a pattern and closeness relationship between two or more variables. r =       = == = = = = −− −− n i n i ii n i n i ii n i n i n i ii yynxxn yixyixn 1 1 22 1 1 22 1 1 1 )()( .......................................... (2) with: xi = observation data (actual data) yi = estimation data (estimation result data) n = the number of data table 2. criteria of correlation coefficient value r value interpretation 0 – 0.19 very low 0.20 – 0.39 low 0.40 – 0.59 moderate 0.60 – 0.79 strong 0.8 – 1 very strong 3. root mean squared error (rmse) rmse= n yx n i ii = − 1 2 )( (3) with: xi = observation data (actual data) yi = estimation data (estimation result data) n = the number of data civil and environmental science journal vol. iii, no. 01, pp. 018-030, 2020 ol. xx, no. xx, pp. xxx-xxx, 20xx 22 4. relative error test this test is used to determine the comparison between the magnitudes of one variable against other variables used as a benchmark for actual variables. kr = i n i ii y yx = − 1 )( 100% (4) with: xi = observation data (actual data) yi = estimation data (estimation result data) n = the number of data 3. results and discussion 3.1. hydrological analysis consistency test consistency test is carried out by two methods, the double mass curve method for station post rainfall data and the raps method for trmm data and discharge data figure 1 double mass curve of figure 2 double mass curve of figure 3 double mass curve of dampit rain station post poncokusumo rain station post tumpukrenteng rain station post figure 4 double mass curve figure 5 double mass curve of turen rain station post of wajak rain station post y = 0.9815x 0 5000 10000 15000 20000 25000 30000 35000 40000 0 10000 20000 30000 40000 c u m u la ti v e o f d a m p it r a in s ta ti o n p o st (m m ) cumulative of the surrounding rain station post(mm) y = 0.988x 0 5000 10000 15000 20000 25000 30000 35000 40000 0 10000 20000 30000 40000c u m u la ti v e o f p o n c o k u su m o r a in s ta ti o n p o st (m m ) cumulative of the surrounding rain station post(mm) 44.47o 44.65 o y = 0.928x 0 5000 10000 15000 20000 25000 30000 35000 40000 0 10000 20000 30000 40000 c u m u la ti v e o f t u m p u k re n te n g r a in s ta ti o n p o st (m m ) cumulative of the surrounding rain station post(mm) 42.86o y = 0.9978x 0 5000 10000 15000 20000 25000 30000 35000 40000 0 10000 20000 30000 40000 c u m u la ti v e o f t u re n r a in s ta ti o n p o st (m m ) cumulative of the surrounding rain station post(mm) 44.94o y = 1.1076x 0 5000 10000 15000 20000 25000 30000 35000 40000 45000 0 10000 20000 30000 40000c u m u la ti v e o f w a ja k r a in s ta ti o n p o st (m m ) cumulative of the surrounding rain station post(mm) 47.92o civil and environmental science journal vol. iii, no. 01, pp. 018-030, 2020 ol. xx, no. xx, pp. xxx-xxx, 20xx 23 table 3 recapitulation of the α value at each rain station post no rain station post α value 1 dampit 44.47° 2 poncokusumo 44.65° 3 tumpukrenteng 42.86° 4 turen 44.94° 5 wajak 47.92° table 4 recapitulation of consistency test results no post name double mass curve method raps method information angle q/n0,5 calculate q/n0,5 table r/n0,5 calculate r/n0,5 table 1 dampit 44.47° consistent 2 poncokusumo 44.65° consistent 3 tumpukrenteng 42.86° consistent 4 turen 44.94° consistent 5 wajak 47.92° consistent 6 awlr 0.54 1.16 0.63 1.31 consistent 7 trmm 0.41 1.20 0.54 1.39 consistent based on figure 1 to figure 5 and table 3 then can be said that rainfall data of rain station post that used after being tested using the double mass curve method is consistent because the resulting angle is in the value ranges of 42o< α < 48 o. whereas based on table 4, the trmm rainfall data consistency test and the discharge data using the raps method also meet the test requirements because the value of qcalculate< qcritical and the value of rcalculate< rcritical so that the results can be considered to be consistent. these test results indicate that the selected data can be used for further hydrological testing and analysis. homogeneity test in this study, annual rainfall data of the rainfall station was tested for absence of trends by the spearman method using 2-side t-test. the recapitulation of the test results presented as follows. table 5 recapitulation of test for no trend results no. name of rain station post tcalculate α tc information 1 dampit 0.774 5% 2.131 not indicate a trend 2 poncokusumo 0.754 5% 2.131 not indicate a trend 3 tumpukrenteng 0.876 5% 2.131 not indicate a trend 4 turen 0.266 5% 2.131 not indicate a trend 5 wajak 2.052 5% 2.131 not indicate a trend 6 awlr tawangrejeni 2.561 1% 3.169 not indicate a trend 7 trmm 0.324 5% 2.131 not indicate a trend based on table 5 can be seen that the entire data (except awlr discharge data) did not indicate a trend by showing tcalculate < ttable at a 5% confidence degree. thus, these data can be further analyzed. civil and environmental science journal vol. iii, no. 01, pp. 018-030, 2020 ol. xx, no. xx, pp. xxx-xxx, 20xx 24 table 6 recapitulation of variance stability test results (f test) no. name of rain station post fcalculate α fc information 1 dampit 0.759 5% 3.370 the value of the variance is stable 2 poncokusumo 1.168 5% 3.370 the value of the variance is stable 3 tumpukrenteng 5.658 1% 6.840 the value of the variance is stable 4 turen 1.449 5% 3.370 the value of the variance is stable 5 wajak 0.830 5% 3.370 the value of the variance is stable 6 awlr tawangrejeni 22.326 1% 10.97 the value of the variance is not stable 7 trmm 1.416 5% 3.370 the value of the variance is stable table 7 recapitulation of average stability test results (t test) annual period no. name of rain station post tcalculate α tc information 1 dampit 0.856 5% 2.131 the average value is stable 2 poncokusumo 1.190 5% 2.131 the average value is stable 3 tumpukrenteng 0.617 5% 2.131 the average value is stable 4 turen 0.727 5% 2.131 the average value is stable 5 wajak 1.183 5% 2.131 the average value is stable 6 awlr tawangrejeni 1.906 5% 2.228 the average value is stable 7 trmm -0.129 5% 2.131 the average value is stable from table 6 and table 7 above it can be seen that the value of f calculate < the value of f table and the value of t calculate < the value of t table, so it can be concluded that the rainfall data of the five rain station posts, the trmm rainfall data, and the discharge data used have a stable variance and average. the persistence test is an independent test for each value in the periodic series. first, the number of serial correlation coefficients must be calculated by the spearman method, then the calculation of the persistence test with the t-test is conducted. the recapitulation of the test results is presented as follows. table 8 recapitulation of persistence test results no. name of rain station post tcalculate α tc information 1 dampit -1.65 5% 2.145 data is random 2 turen -1.432 5% 2.145 data is random 3 tumpakrenteng -2.028 5% 2.145 data is random 4 wajak -3.840 5% 2.145 data is random 5 poncokusumo -0.828 5% 2.145 data is random 4 tawangrenjani awlr discharge -0.178 5% 2.262 data is random 5 trmm -0.793 5% 2.145 data is random based on table 8 it can be seen that almost all of the data are random by showing tcalculate< ttable at 5% confidence level/degree. thus, these data can be analyzed further. 3.2 correlation of rain data of rain station post and trmm based on table 9, the correlation analysis results of all rain station posts with trmm data (20022018 data), have a good correlation with trmm rain data, this can be seen from the correlation coefficient values that are at values> 0,6. civil and environmental science journal vol. iii, no. 01, pp. 018-030, 2020 ol. xx, no. xx, pp. xxx-xxx, 20xx 25 table 9 correlation results of monthly rain data of rain post with trmm no. post correlation 1 dampit 0.81 2 poncokusumo 0.81 3 tumpuk renteng 0.78 4 turen 0.86 5 wajak 0.85 table 10 thiessen coefficient of lesti sub watershed no. post area (km2) kr 1 dampit 200.601 0.659 2 poncokusumo 89.476 0.294 3 tumpuk renteng 1.299 0.004 4 turen 12.937 0.043 5 wajak 76.894 0.253 total 304.313 1 3.3 regional average rainfall analysis figure 6 map of the influence area of the lesti sub watershed rain station post by using the thiessen polygon method based on table 10 obtained that the results of the value of kr for each post of the rain station is a comparison of the area of influence of each post of the rain station on the area of the lesti sub watershed towards the total area of the lesti sub watershed. the calculation results of the kr value are then used to calculate the regional average rainfall. civil and environmental science journal vol. iii, no. 01, pp. 018-030, 2020 ol. xx, no. xx, pp. xxx-xxx, 20xx 26 figure 7 shows a comparison graph of regional average rainfall with trmm before being corrected. from the graph it can be seen that the trmm rainfall value tends to be smaller, but has a pattern and fluctuation that is almost the same as the regional average rainfall. further analysis after obtaining regional average rainfall is a validation analysis of rainfall data from the rain station post and trmm rainfall. figure 7 graph of comparison of average regional rainfall with trmm 3.4 calibration and validation analysis of rain data from rain station post and trmm trmm rain data calibration figure 8 through figure 13 shows the calibration scatterplot to get the best equation. from the regression equation that has been obtained to get the corrected trmm rain data then the used regression equation with the largest r2 value. obtained the results of the trmm rainfall regression equation in the lesti watershed with r² = 0.7158 with the polynomial equation. figure 8 linear regression equation figure 9 intercept linear regression equation figure 10 polynomial regression figure 11 rank regression equation equation y = 1,0837x + 53,792 r² = 0,7049 0 200 400 600 800 1000 0 200 400 600 800 r a in s ta ti o n p o st r a in fa ll ( m m ) monthly trmm rainfall(mm) data calibration of station post and trmm 16 years (2002-2017) linear function y = 1,2626x r² = 0,6743 0 200 400 600 800 1000 0 200 400 600 800r a in s ta ti o n p o st r a in fa ll ( m m ) monthly trmm rainfall(mm) data calibration of station post and trmm 16 years (2002-2017) intercept linear function y = -0,0007x2 + 1,4289x + 30,867 r² = 0,7158 0 200 400 600 800 1000 0 200 400 600 800r a in s ta ti o n p o st r a in fa ll (m m ) monthly trmm rainfall(mm) data calibration of station post and trmm 16 years (2002-2017) polynomial function y = 3,0693x0,8318 r² = 0,6561 0 200 400 600 800 1000 0 200 400 600 800 r a in s ta ti o n p o st r a in fa ll ( m m ) monthly trmm rainfall(mm) data calibration of station post and trmm 16 years (2002-2017) rank functiont civil and environmental science journal vol. iii, no. 01, pp. 018-030, 2020 ol. xx, no. xx, pp. xxx-xxx, 20xx 27 figure 12 logarithmic regression figure 13 intercept polynomial regression equation equation trmm rain data verification the next stage is verification of the data outside the data used for calibration. figure 14 verification of trmm rainfall in 2018 figure 14 shows a verification graph of rain data of rain station post with trmm outside the calibration year. the correlation value (r) produced for the 2018 regional rainfall is 95,98%, this shows that the corrected trmm rainfall data has a very strong correlation with station post rainfall data. trmm rain data validation validation is performed on data outside the data used for calibration. to be able to measure the magnitude of the difference in the results of the model calculation towards the observational data then conducted trmm rain data validation using the objective function of the nse (nash-sutcliffe efficiency), correlation coefficient (r), rmse (root mean square error), and relative error (re). table 11 recapitulation of calculation results for validation of station post rainfall data with trmm before corrected total year nse rmse kr r calibration validation value interpretation value interpretation 10 7 0.545 qualified 114.949 0.269 0.829 strong 13 4 0.476 qualified 122.960 0.282 0.807 moderate 16 1 0.631 qualified 108.479 0.416 0.959 very strong r = 0.9598 0 50 100 150 200 250 300 350 400 450 500 0 200 400 600r a in s ta ti o n p o st r a in fa ll ( m m ) monthly trmm rainfall(mm) data verification of station post and trmm 1 year (2018) y = 90,312ln(x) 157,15 r² = 0,547 -400 -200 0 200 400 600 800 1000 0 200 400 600 800 r a in s ta ti o n p o st r a in fa ll ( m m ) monthly trmm rainfall(mm) data calibration of station post and trmm 16 years (2002-2017) logarithmic function y = -0,0011x2 + 1,6534x r² = 0,7092 0 200 400 600 800 1000 0 200 400 600 800 r a in s ta ti o n p o st r a in fa ll ( m m ) monthly trmm rainfall(mm) data calibration of station post and trmm 16 years (2002-2017) intercept polynomial function civil and environmental science journal vol. iii, no. 01, pp. 018-030, 2020 ol. xx, no. xx, pp. xxx-xxx, 20xx 28 table 12 recapitulation of calculation results for validation of station post rainfall data with trmm after corrected total year nse rmse kr r calibration validation value interpretation value interpretation 10 7 0.657 qualified 99.726 0.045 0.835 strong 13 4 0.674 qualified 97.033 0.007 0.825 medium 16 1 0.890 good 59.163 0.116 0.960 very strong figure 15 graph of lesti watershed rainfall in 2007-2018 based on table 11 and table 12 by comparing the validation results of uncorrected data and corrected data, the corrected data validation results have better results. the results of the data validation show the results "qualified" at the nse method for all data, except for 1 year validation of the corrected data obtained the results of "good". the rmse value for uncorrected data validation is relatively high, but has decreased in the validation of corrected data. the value of relative error is classified as very small in all data. for the correlation coefficient of all data, the calculation results show a very strong relationship, but the best results are found in the validation of 1-year corrected data using 16-year data calibration. this shows that the more data used for calibration, then the better it is for validation. 3.5 water discharge analysis fj mock methode flow discharge simulation is carried out by trial and error of parameter values which are carried out repeatedly until it meets the model performance criteria. based on the calibration results obtained, the simulation discharge hydrograph approaches the observation discharge. the trial results of the parameter values can be seen in table 13. figure 16 graph of model discharge and observation discharge of lesti watershed in 2002-2018 0,0 100,0 200,0 300,0 400,0 500,0 600,0 700,0 800,0 900,0 1000,0 ja n a p r ju l o c t ja n a p r ju l o c t ja n a p r ju l o c t ja n a p r ju l o c t ja n a p r ju l o c t ja n a p r ju l o c t ja n a p r ju l o c t ja n a p r ju l o c t ja n a p r ju l o c t ja n a p r ju l o c t ja n a p r ju l o c t ja n a p r ju l o c t 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018r iv e r f lo w d is c h a rg e ( m ³/ se c ) month rainfall of lesti watershed in 2007 2018 0,0 20,0 40,0 60,0 80,0 100,0 120,0 140,0 160,0 180,0 ja n a p r ju l o c t ja n a p r ju l o c t ja n a p r ju l o c t ja n a p r ju l o c t ja n a p r ju l o c t ja n a p r ju l o c t ja n a p r ju l o c t ja n a p r ju l o c t ja n a p r ju l o c t ja n a p r ju l o c t ja n a p r ju l o c t ja n a p r ju l o c t 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 r iv e r f lo w d is c h a rg e ( m ³s e c ) month calculation discharge and observation discharge in 2007-2018 debit awlr debit ch wilayah debit trmm tidak terkoreksi debit trmm terkoreksi civil and environmental science journal vol. iii, no. 01, pp. 018-030, 2020 ol. xx, no. xx, pp. xxx-xxx, 20xx 29 table 13 simulation results for fj mock parameters no year parameter smc (mm) i k is (mm) vn (mm) 1 2007 250 0.53 0.09 50 50 2 2008 250 0.21 0.92 50 50 3 2009 250 0.08 0.10 50 50 4 2010 250 0.72 0.99 50 50 5 2011 250 0.61 0.97 50 50 6 2012 250 0.56 0.99 50 50 7 2013 250 0.97 0.97 50 50 8 2014 250 0.79 0.99 50 50 9 2015 250 0.91 0.99 50 50 10 2016 250 0.95 0.99 50 50 11 2017 250 0.89 0.99 50 50 12 2018 250 0.98 0.99 50 50 from figure 16 it can be seen that the trend of monthly awlr discharge and the fj mock method flow discharge have almost the same pattern. from the table, it appears that the awlr data for 20082009 is indeed that the value is very far from the average each year which occurs every season. validation of f.j. mock flow discharge to show the accuracy value of each flow discharge simulation from the different rain database with the fj mock method, conducted validation test of observation mock discharge data (awlr) using the objective function of nse, correlation coefficient, rmse and relative error. table 14 validation results on fj mock flow discharge no discharge of model results with database value nse r rmse kr 1 rain station post rainfall 0.507 0.713 19.383 0.001 2 trmm rainfall 0.374 0.614 21.839 0.016 3 corrected trmm rainfall 0.411 0.646 21.190 0.025 based on table 14 above, the nse value of the model discharge with three variations of rain data has a value> 0.36 which indicates that the discharge analysis of the model result can be said qualified. but the nse value of discharge data with trmm database has the smallest value, so that it is better to use corrected trmm data. while the value of the correlation coefficient (r) from the three sources of rain data has a value of 0,5 <r≤ 0,75 which indicates that the results of the model have a strong correlation. the rmse value of the model discharge with the rain data of rain station post is smaller than the discharge of trmm model result and corrected trmm, it shows that the discharge with the rain station post data has a smaller deviation than the awlr discharge. the relative error value (re) of the model discharge with trmm rain data has a smaller value than the other results, this shows that the model discharge with trmm rain data there is less error. the error here refers to errors in recording. 4. conclusions the results of correlation analysis of trmm satellite rainfall data and rainfall data from the rain station post have a good. the results of the station post rainfall data validation with trmm show that the results of the corrected data validation have better results than the trmm data before being corrected. the best result is found in the validation of 1-year corrected data using 16-year data civil and environmental science journal vol. iii, no. 01, pp. 018-030, 2020 ol. xx, no. xx, pp. xxx-xxx, 20xx 30 calibration. this shows that the more data used for calibration, then the better it is for validation. the results of the validation towards the analysis of flow discharge using the fj mock method, validation is obtained by flow discharge analysis using rainfall data of the rain station post, overall analysis shows trmm data can be used as an alternative of the rain data that is used to estimate flow discharge, but the result of flow discharge analysis is still better using rainfall data from the rain station post. references [1] cheng chen. 2011. adaptability evaluation of trmm satellite rainfall and its application in the dongjiang river basin. elsevier procedia environmental sciences 10 ( 2011 ) 396 – 402. [2] destiana wp, joko s, adam p. 2017. evaluasi data hujan satelit untuk prediksi data hujan pengamatan menggunakan cross correlation. seminar nasional sains dan teknologi [3] levina. 2016. comparison of trmm satellite rainfall and aphrodite for drought analysis in the pemali-comal river basin. elsevier procedia environmental sciences 33 ( 2016 ) 187 – 195. [4] maulidani, s. ihsan, n., sulistiawaty. 2015. analisis pola dan intensitas curah hujan berdasarkan data observasi dan satelit tropical rainfall measuring mission (trmm) 3b42 v7 di makasar. jurnal sains dan pendidikan fisika, vol. 11, no.1 [5] motovilov, y.g., gottschalk, l., engeland, k. dan rodhe, a. 1999. validation of a distributed hydrological model against spatial observations. elsevier agricultural and forest meteorology. 98 : 257-277. [6] na yang. 2017. evaluation of the trmm multisatellite precipitation analysis and its applicability in supporting reservoir operation and water resources management in hanjiang basin, china. elsevier journal of hydrology 549 (2017) 313–325. [7] sugiyono. 2017. matematika : aproksimasi kesalahan. modul. tidak diterbitkan. yogyakarta: universitas gadjah mada [8] syaifullah, d. 2013. kondisi curah hujan pada kejadian banjir jakarta dan analisis kondisi udara atas wilayah jakarta bulan januari-februari 2013. jurnal sains dan teknologi modifikasi cuaca (jstmc), 14(1), 19-26 [9] syaifullah, d. 2014. validasi data trmm terhadap data curah hujan aktual di tiga das di indonesia. jurnal meteorologi dan geofisika 15 (2) :109-118. civil and environmental science journal vol. 4, no. 2, pp. 192-201, 2021 192 analysis of carrying capacity of the porong river caused by sidoarjo mud disposal robert agung abdi saputro1*, suhardjono1, pitojo tri juwono1 1water resources engineering department, universitas brawijaya, malang, 65145, indonesia *r.agungwre01@gmail.com received 20-01-2021; accepted 23-08-20211 abstract. this study aims to examine the sediment distribution models and the stream sediment distribution due to mud disposal of porong river. it examines how the sediment distribution models and deposition, the distribution of stream sediment due to mud disposal along with its impacts on the river's capacity, and whether the mud disposal has a harmful impact on the water quality. the data used were based on topographic and bathymetric data of porong river, crosssections of the river, and terrain sediment distribution patterns. the study conducted field and secondary data analysis, hydrological analysis, oceanographic analysis of mura river and river hydraulic analysis. the study concludes that to maintain its capacity and prevent negative impacts, it is necessary to protect the cliffs and embankments along the segment of the river. to protect the community pond area, overburden and/or river dredging activities along with the segments from the branch to the estuary of the river are needed. furthermore, it is also necessary to add artificial inputs such as submersible kribs that are arranged on piles to deal with problems of river sediments in the mouth of porong river. keywords: porong river, sedimentation, sidoarjo mud 1. introduction the mudflow in porong, sidoarjo, which occurred on may 29, 2006, continues to this day. the state of mudflow still shows fluctuation in large, medium and small range, reaching 1 to 3 meters in height. it is estimated that the mudsflow will last about 20-30 years, while the possibility of closing the flow of success is very low. in accordance with perpres (presidential decree) 14/2007 jo. perpres 48/2008 jo. perpres 40/2009, the mud overflow is to be dumped into the sea via porong river. porong riverwas chosen because beside of being ready for use for the ongoing disaster, it is also in the long term that has the most economical operating and maintenance costs for the energy station [1]. the management of the disposal of the mudsflow from the mud storage basin to porong river is carried out optimally during the rainy season, while during the dry season it is carried out in a limited way. this role should be maintained and 1 cite this as: saputro, r.a.a., suhardjono, s. & juwono, p.t. (2021). analysis of carrying capacity of the porong river caused by sidoarjo mud disposal. civil and environmental science journal (civense), 4(2), 192201. doi: https://doi.org/10.21776/ub.civense.2021.00402.9 civil and environmental science journal vol. 4, no. 2, pp. 192-201, 2021 193 secured so that the additional mudflow does not reduce the capacity of the porong river and does not cause flooding upstream and / or indirectly in the influence are of porong river. the disposal of the mud in the porong river is not the target of the final elimination but only as a means of draining the mud into the sea. for the mud to flow into the sea and at the same time to maintain the porong river's performance in flood control in the brantas river, it is necessary to carry out activities to safeguard the porong river. with over 11 (eleven) years of experience in using porong river as a means of channeling mud into the sea, it is hoped that in the coming years things will not happen to harm or reduce the function of porong river as a diversion channel for the brantas watershed. in addition, a study found that a significant sediment deposition occurred at the river bed of porong river due to increase sediment discharge from the volcano during dry periods [2]. furthermore, in accordance with presidential decree no. 40 of 2009 of the republic of indonesia, in article 9 point d [3], porong river’s functions are added to deal with the overflow of mud of sidoarjo so that the mud can flow into the sea and at the same time maintain the performance of the porong river in flood control in the brantas river watershed (figure 1). with the addition of these functions, it is necessary to conduct a capacity analysis for porong river. thus, this study tries to examine the sediment distribution models, and the stream sediment distribution due to mud disposal. figure 1. profile of outlet stretch of the porong river mud 2. material and method 2.1 data this study used the analysis of porong river topographic data and bathimetry, river cross section and field sediment distribution models [3] [4]. meanwhile, to get the type of tides of porong river civil and environmental science journal vol. 4, no. 2, pp. 192-201, 2021 194 estuary, this study analyzed tidal observation data and bmkg (meterological, climatological, and geophysical agency) or other secondary data. in hydrological analysis, the data used are awlr flow data. the secondary data of this study include the oceanographic data of wind direction and speed, as well as characteristics and mud flows that have been in the laboratory. in addition, the discharge recording of the discharge of sludge discharged into the porong river is also carried out with a sludge content ratio: 20% solids, 80% water. 2.2 steps in the research process the analysis process of this study is grouped into four, including field and secondary data analysis, hydrological analysis, oceanographic analysis of porong river estuary, and hydrological analysis of porong river. a. field and secondary data analysis includes topographic data and bathymetry analysis of the porong river cross section and changes in the capacity volume of the porong river, and the terrain sediment distribution model. the other data are in the form of data of the sediment characteristics of the porong river, tidal observations and bmkg secondary data, as well as the water quality of porong river due to the sidoarjo mudflow and its impact on the environment; b. the hydrological analysis carried out is in the form of a flood opportunity analysis that crosses the porong river by verifying the awlr data; c. oceanographic analysis of porong river estuary includes analysis of wind direction and speed data to obtain wind rose and the analysis of porong river sedimentation and erosion models along the coastline; d. in the analysis of river hydraulics, the study conducted an analysis of the water level profile of the porong river flood before the outlet, the outlet at the mouth of the kali river, as well as the analysis of the distribution of river sedimentation due to mud disposal. 3. results and discussion 3.1 sediment distribution patterns a. assessment on the distribution of existing sediment transport in the field in this analysis, the topography and bathymetry of the porong river were carried out starting from the upstream of the sidoarjo mud outlet pipe to the mouth of the porong river. previously, a study shows that the period of movement patterns of water upstream from the offshore direction towards the plug (ups) and the movement would leave for offshore direction towards the downs [5]. bathymetry measurements were also carried out offshore jutting into the sea on the left and right of the kali porong estuary as well as the front area of lusi island (figure 2). additionally, lusi island is not only receiving mud sourced from sidoarjo mud, but also from three watershed systems (figure 3). the study of the distribution of sediment transport in the existing conditions is the result of the identification of the deposition area and the scour area. sources of data used are the results of the 2014 porong river bathimetry and topographic and bathymetry measurement data in this work. based on bathimetry and topographic data for the 2014 and 2019 measurement, the difference is calculated using the raster method. raster calculator calculation results for the volume of precipitation: the difference between 2019 and 2014 elevation times the cell size raster is as follows: sediment volume : 2.490.766,25 m3; scour volume : 3.228.751,50 m3. sediment distribution model in 2014 bathymetry lusi island was formed at the porong river estuary in 2014. the previous formation of lusi island was a soil bank area resulting from the dragging of porong river. some study shows that it’s the concentration of heavy metals contained in its mud were below environmental soil quality guidelines [6]. similar founding occurred at porong river estuary [7]. in 2014, the lusi island had not yet formed civil and environmental science journal vol. 4, no. 2, pp. 192-201, 2021 195 new mangroves and islands as in the current state of 2019. additionaly, in 2012, the mangroves growth in the mouth of porong river is found to create an increase of areas in the wetland of more than 10 ha [8]. this study aims to examine the models of sediment distribution and deposition. therefore, this study looks into the field conditions in 2014 modeled with the prediction result and the current condition in 2019. here is a picture of the sedimentation distribution model in 2014: figure 2. sediment distribution model at the porong river estuary and lusi island; sediment sourced from sidoarjo mud. figure 3. sediment distribution model at porong river estuary and lusi island; sediment sourced from sidoarjo mud and 3 watershed (das) systems. civil and environmental science journal vol. 4, no. 2, pp. 192-201, 2021 196 figure 4. sediment distribution model in 2019 bathymetry during dry season figure 5. sediment distribution model in 2019 bathymetry during wet season sediment distribution model in 2019 bathymetry the aim of the 2019 bathymetric data modeling analysis is to predict future distribution patterns so that the required estuary repair planning can be done [9]. from the bathymetric modeling in 2019, it can be concluded that there will be an accumulation of sediment deposits at the mouth of the porong river estuary between baru island and lusi island. the sediment distribution appears to be different in every season. in figure 4, it can be seen the sediment distribution during dry season. meanwhile, figure 5 shows a different pattern of the distribution during wet season and the wider model is spotted during flood season (figure 6). furthermore, a study found that during wet season, the thickness of the sediment in lusi island is ranged from 1.6 to 2.6 m [10]: civil and environmental science journal vol. 4, no. 2, pp. 192-201, 2021 197 figure 6. sediment distribution model in 2019 bathymetry during flood season a. inflow sediment of porong river a modeling has been tested to represent field conditions, so that the value of the sediment concentration in the time series approach that occurred during 2009 to 2018 can be used using avswat modeling data [1]. the sediment inflow in porong river is the cumulative amount of sediment in the two watershed outlets, namely kali sadar and kali kambing is presented in figure 7. figure 7 . sediment concentration time series result of avswat model 2000 3.2 assessment of river sediment distribution due to mud disposal a. assessment of sediment distribution of normal / existing operation pattern in the model test of the conditions of the normal discharge flow limit, the 3 sediment watershed systems (sadar river watershed, kambing river watershed, outflow weir lengkong and the disposal of sidoarjo mud as in the existing operating pattern are currently operating resulting in changes in the base in the river fork of porong river around 0.065 m annually [11]. civil and environmental science journal vol. 4, no. 2, pp. 192-201, 2021 198 at the mouth of the porong river, located near lusi island, the change in sediment deposits is 0.064 m each year. in the sidoarjo mud outlet location area up to 1 km downstream is 0.073 m to 0.07 m. if this modeling is compared/verified according to the results of field measurements in 2014 and 2019, the sedimentation rate at the porong rivers branch is 1.03 m/5 years or 0.21 m each year [3] [4] (figure 8). whereas the field verification for the kali porong estuary area near lusi island is 3.9 m/5 years or 0.78 per year, while the modeling results produce 0.064 m each year, so there is a difference of 0.716 m which is assumed to be due to the flow effect of the pattern, tides, and the coastal sediment. figure 8. profile of sediment in porong river resulting from watershed sediment and existing operation model of sidoarjo mud. b. assessment of sediment distribution for operation pattern increased 2x the operation pattern of sidoarjo mud disposal is increased to 2 x normal operations, resulting in an increase in sediment deposits in the estuary to changes in the base in the river fork for porong river 0.14 m annually. the impact of deposition in the watershed of lusi island is 0.132 m annually. the pattern of increased sediment deposition due to surgery is increased to 2 times (figure 9). figure 9. profile of sediment of porong river up to the estuary due to the impact of the watershed sediment and the existing operation pattern of sidoarjo mud and increased 2 times. c. assessment of sediment distribution for operation pattern increased 5x the addition of the discharge capacity of sidoarjo mud to porong river via the outlet pipe was increased by 5 times, which results a 0.1 m increase in sedimentation rate each year from the existing discharge. additional capacity can be seen in the area of the outlet nozzle, increasing by 0.38 m (figure 10) each year. civil and environmental science journal vol. 4, no. 2, pp. 192-201, 2021 199 figure 10. the sediment profile in porong river to the estuary caused by watershed sediment and the existing operation pattern of sidoarjo mud and increased 5 times. d. assessment of sediment distribution for operation pattern increased 10x as a result of the operation pattern increased to 10 x from the current operation, it takes the need for the operation pattern of porong river 4 km from the outlet for every 5 years monitoring until dredging, so in this study it is not recommended to apply this operating pattern. as the operation is increased to 10 x, there is also an increase of the sediment deposits as seen in figure 11. figure 11. the sediment profile in porong river to the estuary caused by watershed sediment and the existing operation pattern of sidoarjo mud and increased 10 times. 3.3 the analysis of environmental impact according to the result of water quality testing and field monitoring, it can be concluded as follows: 1. the water quality standards are classified in class 3, are always safe for the water supply of ponds and do not cause pollution that could endanger the fishing ecosystem [12]. additionally, in a study conducted by triaji et.al (2017), the water quality of porong river is classified as medium criteria through an analysis using nsf-wqi (national sanitation foundation – water quality index) [13]. furthermore, the parameters show the quality of the water is worth of 34 ,g/l for cod, 14.46 mg/l for nitrate, 30 mg/l for tts, and 0.43 mg/l for phosphrate [14]. in terms of the founding of tts, similar condition is found in brantas river [15] without being polluted based on the tds parameter [16-17]. 2. further downstream from porong river, the tidal effect is increasingly visible, where the brackish water category is visible at a distance of 750 m from the sidoarjo mud outlet. increase by 5x increase by 10x civil and environmental science journal vol. 4, no. 2, pp. 192-201, 2021 200 3. porong river waters after discharge may contain high mineral and metal content mixed with salinity levels already in brackish water category; 4. the lower the conditions of the do parameter, the higher the indication of the reduction process in water; 5. it is possible that the effect of the discharge from sidoarjo mud has a direct effect on the increase of the tds parameter in the waters of porong river. 4. conclusions based on the calculation using raster method, it shows that there has been a difference between the bathymetric and topographic data in 2014 and 2019 in terms of the sediment and the scour of the porong river. the difference of the sediment is 2.490.766,25 m3, while the scour of the river is 3.228.751,50 m3. this difference shows that the capacity the porong river has in 2014 is bigger than in 2019. the decreasing capacity of the river each year results in increasing in the elimination capacity of sidoarjo mud can be allowed to 5 times the current capacity. thus, in order to maintain the capacity of porong river, proper planning is required so as not to have negative impacts on the environment. references [1] e. suhartanto, panduan avswat 2000 dan aplikasinya di bidang teknik sumber daya air. 2008 [2] s. kure, b. winarta, y. takaeda, k. udo, “effects of mud flows from the lusi mud volcano on the porong river estuary, indonesia,” journal of coastal research. coastal education and research foundation, vol. 70 no. 70, pp. 568-573, apr, 2014 [3] peraturan presiden republik indonesai nomor 40, 2009, badan penanggulangan lumpur sidoarjo, jakarta. [4] d. priyantoro, teknik pengangkutan sedimen. 1987 [5] m. mustain, “the model of current pattern at the mouth of porong river sidoarjo,” international journal of civil engineering and technology (ijciet), vol. 9, no. 1, pp. 688701, jan, 2018 [6] b. d. krisnayanti, d. s. agustawijaya, “characteristics of lusi mud volcano and its impact on the porong river,” journal of degraded and mining lands management, vol. 1, no. 4, pp. 207-210, july, 2014 [7] l. k. harlyan, r. dwi, s. h. j. sari, f. iranawati, “concentration of heavy metal (pb and cu) in sediment and mangrove avicennia marina at porong river estuary, sidoarjo, east java,” research journal of life science, vol. 2, no. 2, pp. 124-132, aug. 2015 [8] f. sidik, t. hidayatullah, h. p. kadarisman, c. e. lovelock, “evaluation of mangrove development in a created mangrove wetland in porong, east java,” regional symposium on mangrove ecosyste management in southeast asia. eds. bedjo santoso and takahisa kusano. ministry of forestry – indonesia proc., march, 2013 [9] b. w. parkinson, global positioning system : theory and applications, volume ii. 1996 [10] a. k. engki , p. dj. viv, “tidal, wave, current, and sediment flow patterns in wet season in the estuary of porong river sidoarjo, indonesia,” isoceen 2017. matec web conference. vol. 177, pp. 1-13, july. 2018 [11] g. w. breusers, “river analysis system hec-ras.” hydraulic reference manual version 4.1. california., 2012 [12] peraturan pemerintah republik indonesia nomor 82, 2001. pengelolaan kualitas air dan pengendalian pencemaran air. jakarta. [13] m. triaji, r. yenny, m. mahmudi, “analysis of water quality status in porong river,” jurnal pembangunan dan alam lestari, vol. 8, no. 2, 2017 [14] i. suntoyo, z. hasan, s. muhammad, n. sukmasari, g. angraeni, h. tanaha, m. umeda. s. kure, “modelling of the cod, tts, phosphate and nitrate distribution due to the sidoarjo mud civil and environmental science journal vol. 4, no. 2, pp. 192-201, 2021 201 flow into porong river estuary,” procedia earth and planetary science, vol. 14, doi.10.1016/j.proeps.2015.07.095, jul, 2015 [15] g. verstraeten, ian p. prosser, p. fogarty, predicting the spatial patterns of hillslope sediment delivery to river channels in the murrumbidgee catchment, journal of hydrology. 2007 [16] kustamar, l. k. wulandari, “the pollution index ad carrying capacity of the upstream brantas river,” international journal of geomate, vol. 9, no. 73, pp. 26-32, march, 2020. [17] haribowo, r., dermawan, v., & yudha, n. (2018). application of artificial neural network for defining the water quality in the river. civil and environmental science journal (civense), 1(1), pp.12-18. doi:https://doi.org/10.21776/ub.civense.2018.00101.2. civil and environmental science journal vol. 4, no. 1, pp. 001-009, 2021 1 the vibration impact to slope deformation on soils potentially liquefactions yayan haryadhi, rakhmat yusuf*, herwan dermawan civil engineering study program, universitas pendidikan indonesia, bandung, 40154, indonesia rakhmatyusuf@upi.edu1 received 08-08-2020; accepted 02-10-2020 abstract. in an area that has potential for earthquake has possibility of losing soil stability and causing physical soil damage, one of them is liquefaction. this research was conducted to determine the magnitude of deformation on slopes with potentially liquefaction. the soil slope samples were tested using shaking table with various slope and frequency was set. research began with soil physical properties had unit weight of density 1.81 gr/cm3, moisture content 2.31%, specific gravity 2.72, sand properties with cu is 2.1, cc is 0.98 and  is 23.962. by giving certain earthquake acceleration in the soil slope sample that was tested by shaking table, it was liquefaction occurred. results of research, the greater slope and frequency given, so the lateral and axial deformation will increase. minimum lateral deformation occurs at frequency 6.6 hz with a slope 6 and maximum lateral deformation is 17 cm at frequency 9.5 hz with slope 24, while minimum axial deformation is 0.5 cm at frequency 8 hz with slope 6 and maximum axial deformation is 5 cm at frequency 9.5 hz with a slope 24, but 12-degree slope can consider as a safe slope for slope which holding vibration. keywords: deformation, frequency, liquefaction, slope 1. introduction liquefaction can cause underground pipes due to buoyant forces to come to the surface (lifeline damage) and heavy structures to sink into the soil. the great east japan earthquake caused liquefaction over a wide area from tohoku to kanto, where tokyo is located, and when the earthquake stopped underground water burst up over the ground with soil grains, a phenomenon called jetted sand. jetted sand caused serious damage to houses, underground pipes, roads, and river levees. liquefaction-caused damage was larger in kanto than in tohoku. we need to apply the lessons about liquefaction from the great east japan earthquake to prevent serious damage in future earthquakes [1]. liquefaction is a process of changing the condition of the saturated sand soil to liquid, caused by a cyclic load at the time of the earthquake so that the moisture pressure increased close to even throw effective stress of the soil. the risks that can be inflicted by the liquidation in the event of an earthquake is a loss of bearing capacity 1 cite this as: haryadi, y., yusuf, r., & dermawan, h. (2021). the vibration impact to slope deformation on soils potentially liquefactions. civil and environmental science journal (civense), 4(1), 01-09. doi: https://doi.org/10.21776/ub.civense.2021.00401.1 civil and environmental science journal vol. 4, no. 1, pp. 001-009, 2021 2 and settlement. in the event of soil liquefaction phenomenon, it can be deformation due to shock. lateral movements of the ground surface or slope of embankment can be damage to other infrastructure. previous studies mention that earthquake-induced landslides are among the most destructive slope movements, not only because of their size and magnitude, but also because of the synergistic action with the earthquake the consequences are higher, due to the earthquake shaking and the landslide effect. studies on landslides triggered by seismic activities are not as extensive as rainfall-induced landslides. in this study, a quantitative risk analysis approach was used to calculate the risk for people exposed to the threat of earthquake-induced landslide in emamzadeh ali, north of iran [2]. recent experiments show that clean sands do not behave similarly to silty sands. tests on loose, silty sand indicate a ‘‘reverse’’ behaviour with respect to confining pressure and this violates the basic assumption that loose, silty sands behave similarly to loose, clean sands. strong correlations between fines content, compressibility, and liquefaction potential are often found for these soils. a procedure for the analysis and evaluation of static liquefaction of slopes of fine sand and silt, such as submarine slopes, mine tailings, and spoil heaps, is presented [3]. the research became important to know, because many of the phenomena of structural failures on the granular soil that occurred during earthquakes, as had been occurred some areas in indonesia. this research was conducted to determine the magnitude of deformation on slopes with potentially liquefaction soils. 2. material and methods the soil samples in this study were taken at bandulu beach, cinangka banten provence at 2018 as seen on figure 1. the soils sample is disturbed sample (soils sample taken freely without protecting its original nature from the location that used to be a study place), and then tested in the laboratory include of soil physical properties which had unit weight of density, moisture content, specific gravity, coefficient of uniform, coefficient curvature obtained through a sieve analysis test and angle of repose obtained through triaxial test. the research methods used are experimental research, which goal is to know the consequences of a treatment given intentionally by researcher. in general, the methodology is used starting from determining the location of research; data collection through experiment in laboratory and literary studies; and data analysis. figure 1. map of micro zonation for liquidity vulnerability of merak – anyer source: eko soebowo, lipi, 2016 [4] 105°55’00’’ 106°00’00’’ 106°05’00’’ 106°10’00’’ low susceptibility zone medium susceptibility zone high susceptibility zone low (0-5) medium (5 15) high (> 5) liquefaction potential zone explanation 0 5 km n -5°55’0’’ -6°0’0’’ -6°5’0’’ civil and environmental science journal vol. 4, no. 1, pp. 001-009, 2021 3 based on the figure 1. it can be seen that on beach bandulu-cinangka is located in a moderate vulnerability zone which allows for liquefaction and also indicated by high value of liquefaction potential index (lpi), in the laboratory carried out soil physical testing and shaking table test with frequency to slope as variable. soil sample testing consists of physical properties which include specific gravity, water contents, bulk density, sieve analysis and angle of repose as the size of the parameters to be used in the analysis. on the table 1. below result of soil properties. table 1. soil properties soil properties symbol value unity bulk density  1.81 gr/cm 3 water content w 2.31 % dry density d 1.77 gr/cm 3 saturated density sat 1.98 gr/cm 3 specific gravity g 2.72 size particles: d10 0.09 mm d30 0.13 mm d60 0.19 mm coefficient of uniform cu 2.10 coefficient of curvature cc 0.98 angle of repose  23.96 degree 2.1. regulation of land acquisition for development of public interest the earthquake was a great shock that spread to the surface of the earth caused by disruption in the lithosphere. this disorder occurs because inside the layer of the earth's skin with a thickness of 100 km. the energy accumulation occurs due to the shifting of the skin of the earth itself [5]. 2.2. total normal pressure the normal pressure total is a multiplication of the weight of soils volume with the depth of the point being tested. by not taking into account the influence of water, the equations are as follows:[6].  = t z (1) where,  = normal pressure (gram/cm 2 ) t = bulk density of soils (gram/cm 3) z = depth (cm) 2.3. effective stress effective stress is the stress in the soil that is influenced by the forces of the water contained in the soil. applied to the soil that is saturated and associated with two stresses, namely the normal total stress () and water pressure pore (u). the equations are as follows:[6].  =  u  = sat z w hw (2) where,  = effective pressure (gram/cm 2 ) w = bulk density of water (gram/cm 3) sat = bulk density of saturate (gram/cm 3 ) z = depth (cm) hw = depth of the point being reviewed to the groundwater (cm) civil and environmental science journal vol. 4, no. 1, pp. 001-009, 2021 4 2.4. angle of repose karl terzaghi defines that the angle of repose as an inner sliding angle obtained from extreme conditions (loose/looser state). in addition, it can be defined as the maximum slope angle where the soils are almost unstable. according to the coulomb theory the angle of repose is brought to a close as the arctan of the maximum static friction coefficient [7]. 2.5. liquefaction according to marcuson [8] the liquefaction is defined as a granular material transformation from solid to liquid form as a result of rising pore water pressure and effective stress loss. rising water pressure of pores is caused by the tendency of granular material to become dense due to cyclic shear deformations. according to seed et. al states that the liquidation is the process of changing the condition of a water saturated sand to liquid due to the increasing water pressure of the pore which is the same value as the total pressure by the cause of dynamic load, so that the effective stress of the soil to zero [9]. 2.6. mechanism of liquefaction the soil is essentially a collection of many soil particles or soil grains that have interconnection details. the cohesion is generated from the weight of the particles that are above the other grains that hold each particle to remain in position and provide strength to the ground. as a result of the cyclic load such as the earthquake, the soil structure on the saturated and loose sand will be destroyed and the sand's constituent particles will move and tend to form a denser configuration. however, the water on the pores of the soil does not drain out and get trapped. as a result, the soils particles cannot move and close to form a denser configuration. thus, the increase in pore water pressure will reduce the cohesion between soil particles causing the soil to lose strength [10].the change of solid nature to the liquid properties that occur in saturated sand is caused by increased pore water pressure and effective stress reduction. effective stress equation [11]. σeff = σtot – u (3) where, σeff = actual stress working on the soil grain (kg/cm 2 ); σtot = stress due to the loading (kg/cm 2 ); and u = porewater pressure (kg/cm 2 ). 2.7. geotechnical modelling modeling is a necessity in geotechnical engineering. modeling is useful for conducting research in laboratories where we can model the original scale into scale model so that we do not need to make models according to natural existing conditions. in this modeling can use the same material as the location of the field. the scale (n) is the ratio or comparison between the values of each parameter that is in the model with the one in the field [12]. 𝑛 = 𝑣𝑎𝑙𝑢𝑒 𝑖𝑛 𝑡ℎ𝑒 𝑓𝑖𝑒𝑙𝑑 𝑣𝑎𝑙𝑢𝑒 𝑖𝑛 𝑡ℎ𝑒 𝑚𝑜𝑑𝑒𝑙 (4) table 2. scale rule for dynamic models parameter model/prototype length 1/n area 1/n2 volume 1/n3 stress 1 strain 1 mass 1/n3 note: n = scale factor [13]. civil and environmental science journal vol. 4, no. 1, pp. 001-009, 2021 5 2.8. deformation according to kuang deformation is a change in form, position and dimension of an object. based on that definition the deformation can be interpreted as a change of position or movement of a point on one object [11]. 2.9. shaking table shaking table research has provided valuable insight into the liquefaction, post-earthquake settlements and lateral soil pressure issues. for models used in shaking tables, the soil can be placed, compacted and instrumented relatively easily [15]. the concept of testing using a shaking table is to analyze the movement of one of the earthquake waves, shear waves [16]. 𝐴(𝑚𝑎𝑥) = (2 𝜋 𝑓) 2 𝑟 (4) 𝑓 = √ 𝐴𝑚𝑎𝑥 (2 𝜋)2 𝑟 (5) 3. result and discussion soil sample testing consists of physical properties which include specific gravity, water content, bulk density, sieve analysis and angle of repose as the size of the parameters to be used in the analysis. 3.1. test result with α = 24 and frequency 9.5 hz (0.7g) the shaking table test was done for 32 seconds. water pore pressure experienced a significant increase after the earthquake load was administered. in the 1st piezometer tool, there is no reading because it is enclosed by ground slope. in the 1st minute pore water pressure increased by 1.10 gr/cm2, then the water pressure of the pore in each of the tools in the 19th second had an increase of 3.00 gr/cm2. the 10th second to 32th seconds is the time span or range when soils liquefaction occurs. based on the analysis shown in figure 2. in the 10th seconds the water pores pressure on the 2nd and 3rd piezometer tools reach 2.00 gr/cm2 and the effective stress reaches 0 gr/cm2. effective stress that has reached 0 gr/cm2 (or minus) is an indication of the occurrence of the liquefaction. but at piezometer #1 is unreadable because it is obstructed by slopes, meaning the pore pressure is still small. in the figure 2. show the dash red line as indication of limit between safe zone and liquefaction zone, under red line is liquefaction zone. this shows that the occurrence of liquefaction is only a few seconds after the vibration, the experiment’s value show that is around 10 seconds. figure 2. water pressure pore and effective stress in time with acceleration 0.7 g -1.2 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 p o re p re ss u re a n d e ff e ct iv e s tr e ss ( gr /c m 2 time (s) relation between pore pressure and effective stress to time with acceleration 0.7g pore pressure (gr/cm2)1 pore pressure (gr/cm2)2 pore pressure (gr/cm2)3 effective stress s¢ (gr/cm2)1 effective stress s¢ (gr/cm2)2 effective stress s¢ (gr/cm2)3safe zone liquefaction zone civil and environmental science journal vol. 4, no. 1, pp. 001-009, 2021 6 (a) (b) figure 3. installation piezometer and shaking table (a) before and (b) after testing the figure 3. the model before and after testing with soil before it was given an earthquake load could withstand the above slope. then after given the earthquake load the slope occurs a settlement of 5 cm on the 1st piezometer area, 0.50 cm on the 2nd piezometer and 0.20 cm on the 3rd piezometer. in addition to the settlement, the ground slope on the model also occurs an avalanche of 17.00 cm due to the soil that is under the slope occurs liquefaction. 3.2. relation between soil slope (α) with effective stress (’) the figure 4. is a graph of the slope relationship to effective stress that is averaged and is taken most on every frequency and then plotted on the chart of the shaking table test result. figure 4. relation slope with effective stress figure 4. provides that information on each slope has different effective stress, due to the influence of pore water pressure and frequency on the model. the greater frequency given the greater water pressure of the pores occurring, resulting in a smaller effective stress. while the slope has no effect on the liquefaction, because the liquefaction that occurs under the slope. 3.3. relationship frequency and earthquake acceleration to deformation on the chart of the frequency relations and the acceleration of the earthquake to the deformation obtained from the shaking table with a tilt of 6, 12, 18 and 24 then given earthquake acceleration 0, 4g; 0.5g; 0.6g and 0.7g with a frequency of 6.60 hz; 7.40 hz; 8.00 hz and 9.50 hz. civil and environmental science journal vol. 4, no. 1, pp. 001-009, 2021 7 figure 5. frequency relations and earthquake acceleration against lateral deformation based on the figure 5. at each given frequency produces different lateral deformations. at a slope of 6 when frequency 6.6 hz does not occur lateral deformation, but when increased its frequency to 7.4 hz, 8.0 hz and 9.5 hz there is a lateral deformation of 3.0 cm, 11.5 cm and 12.0 cm. after that at a slope of 12 with a frequency of 6.6 hz of lateral deformation that occurs by 10.00 cm, frequency 7.4 hz, 8 hz and 9.5 hz lateral deformation that occurs at 10.5 cm, 11.0 cm and 12.0 cm. further testing is done with a slope of 8, the frequency given is 6.6 hz, 7.4 hz, 8 hz and 9.5 the lateral deformation is 10.0 cm, 10.0 cm, 12.0 cm, and 15.0 cm. then at a slope of 24 with the same frequency of lateral deformations that occur that is 9.0 cm, 10.0 cm, 15.0 cm and 17.0 cm. at a slope inclination 12 lateral deformation tends to be linier with changes frequency, meaning that the safe slope of lateral deformation on the slope is about 12 degrees. figure 6. frequency relations and earthquake acceleration of axial deformation at α = 24 from the figure 6. show that the frequency and acceleration of the earthquake to axial deformation, it can give an information on slope α = 24 with various frequency of 6.60 hz, 7.40 hz, 8.00 hz, and 9.50 hz the axial deformation of 1st occurs at 4.00 cm, 4.00 cm, 5.00 cm, and 5.00 cm respectively. r² = 0.9984 0 2 4 6 8 10 12 14 16 18 6.5 7.0 7.5 8.0 8.5 9.0 9.5 l a te ra l d e fo rm a ti o n ( c m ) frequency (hz) relation between frequency an earthquake acceleration to lateral deformation α = 6 α = 12 α = 18 α = 24 0.4 0.5 0.6 0.7 earthquake acceleration (g) 0 1 2 3 4 5 6 6.5 7.0 7.5 8.0 8.5 9.0 9.5 v e rt ic a l d e fo rm a ti o n ( c m ) frequency (hz) relation between frequency and acceleration earthquake to vertical deformation α = 24 (soil settlement 1) α = 24 (soil settlement 2) α = 24 (soil settlement 3) 0.4 0.5 0.6 0.7 earthquake acceleration (g) civil and environmental science journal vol. 4, no. 1, pp. 001-009, 2021 8 further in the axial deformation 2nd occurs by 1.00 cm, 1.00 cm, 0.80 cm, and 0.50 cm. then the axial deformation 3rd occurs by 1.10 cm, 1.20 cm, 0.70 cm, and 0.20 cm. this deformation occurs because the slope is under the soil that is undergoing liquefaction, resulting in axial deformation. table 3. resume of deformation to frequency frequency slope slope deformation axial deformation1 axial deformation2 axial deformation3 hz ° cm cm cm cm 6.6 6 0 2 0.6 0.5 7.4 3 2 0 0 8 11.5 0.5 0.4 1 9.5 12 1.2 0.4 1.2 6.6 12 10 2 1 1 7.4 10.5 2.2 0.5 1 8 11 2.4 0.2 0 9.5 12 2.5 0.3 1 6.6 18 10 1.7 0.2 1.1 7.4 10 1.8 0.1 1 8 12 2.6 0.4 0.7 9.5 15 4 0.5 0.5 6.6 24 9 4 1 1.1 7.4 10 4 1 1.2 8 15 5 0.8 0.7 9.5 17 5 0.5 0.2 4. conclusions modelling vibration frequency influences on deformation on potentially liquid slopes can be concluded as follows: a. with the characteristics of the sand cu < 6 and cc < 1 categorized as poor graded sand and also if the sand is at the most volatile limit then the condition of the soil can be potentially liquefaction. b. earthquake acceleration of 0.40g; 0.50g; 0.60g and 0.70g are shown to cause liquefaction when tested with shaking table. c. the larger of the slope and the given frequency the greater the lateral and axial deformation that occurs. the maximum lateral deformation is 17.00 cm at a frequency of 9.50 hz with a tilt of 24 while the axial deformation occurs at 5.00 cm at 9.50 hz frequency with a tilt of 24. but it is found that the ideal slope to withstand the vibration of the earthquake at 12-degree slope. as an implication in the field of engineering, the application in the planning of slopes on potentially liquefaction soils should attention to the slope maximum of 20 degrees. for warning at the time while of the earthquake, that liquefaction occur very quickly on granular soils or cohesionless soils that is about 10 seconds. acknowledgements we would like to thank all leaders of the civil engineering study program at the indonesia university of education, who have provided research opportunities in the laboratory, special thank you to the chairman of the soil mechanics laboratory, who has allowed the use of space and a number of laboratory equipment. references [1] faculty of societal safety sciences, the fukushima and tohoku disaster. 2018. civil and environmental science journal vol. 4, no. 1, pp. 001-009, 2021 9 [2] s. mostafa mousavi, babak omidvar, fereydon ghazban, and reza feyzi, “quantitative risk analysis for earthquake-induced landslides—emamzadeh ali, iran,” engineering geology 122(3-4):191-203. july. 2011. [3] poul v. lade and jerry a. yamamuro, “evaluation of static liquefaction potential of silty sand slopes,” can. geotech. j. 48: 247–264 (2011). 28 january 2011. [4] soebowo, eko. identification of liquefaction hazard in the coastal area of merak-anyer, banten based on cpt and spt data. research center for geotechnology, indonesian institute of science (lipi). j. segara vol.12 no.2 issn: 1907-0659. 2006. [5] mustafa, badrul. analisis gempa nias dan gempa sumatera barat dan kesamaannya yang tidak menimbulkan tsunami. jurnal teknik sipil, universitas andalas. jurnal ilmu fisika (jif), vol.2 no 1 issn: 1979-4657. 2010. [6] pontororing,c. analisis tegangan-regangan, tekanan air pori dan stabilitas model dam timbunan tanah.pascasarjana teknik sipil universitas sam ratulangi. jurnal ilmiah media engineering vol.4 no.4 issn: 2087-9334. 2014. [7] al-hasemi m.b hamzah dan al-amoudi s.b omar. a review on the angle of repose of granular materials. department of civil and environmental engineering, king fahd university of petroleum and minerals. 2018. [8] putra, g.h., dkk. analisa potensi likuifaksi berdasarkan data pengujian sondir (studi kasus gor haji agus salim dan lapai,padang). jurnal rekayasa sipil volume 5 no.1 issn : 1858 2133. 2009. [9] sarajar a.n, dkk. analisis potensi likuifaksi di pt.pln (persero) uip kit sulmapa pltu 2 sulawesi utara 2 x 25 mw power plan. fakultas teknik.jurusan teknik sipil.universitas sam ratulangi manado. jurnal sipil statik vol.1 no.11 issn: 2337-6732. 2013. [10] chetia, m & saikia, r. critical review on the parameters influencing liquefaction of soils. international journal of innovative research in science, engineering and technology, 3 (4), 110-116. 2014. [11] hardiyatmo, h. c. mekanika tanah i. penerbit gajah mada university press, yogyakarta. 2002. [12] kumala, e. y. pengkajian kinerja hidraulik bangunan pelimpah bendungan santan – di kalimantan timur. pusat litbang sumber daya air. 2007. [13] ilyas, t. pemanfaatan modelling untuk memecahkan masalah geoteknik. fakultas teknik universitas indonesia. 2006. [14] haqqi, kun. f.m. survei pendahuluan deformasi muka tanah dengan pengamatan gps di kabupaten demak (studi kasus: pesisir pantai kecamatan sayung). program studi teknik geodesi. fakultas teknik. universitas diponegoro. 2015. [15] towhata, i. et al. shaking table tests in earthquake geotechnical engineering. department of civil engineering. university of tokyo. current science, vol. 87 no. 10, november 2004. 2015. [16] mase, l. z. studi eksperimental potensi likuifaksi di kali opak imogiri menggunakan alat shaking table. 2013. civil and environmental science journal vol. iii, no. 02, pp. 084-094, 2020 84 model of land acquisition productivity performance for toll road projects in indonesia kartika nur rahma putri1*, puti farida marzuki2 1 department of civil and environmental engineering, universitas gadjah mada, yogyakarta, 55284, indonesia 2 faculty of civil and environmental engineering, institut teknologi bandung, bandung, 40132, indonesia kartikanurrahmaputri@ugm.ac.id1 received 17-07-2020; accepted 04-08-2020 abstract. land acquisition process in the indonesian toll road project has a high level of uncertainty. several previous studies mainly discuss the risks involved in toll road projects and their mitigation measures, but the effect of existing risks on land acquisition scheduling is rarely reviewed. this research aims to develop a model for land acquisition productivity performance for toll road projects. the performance of productivity was modelled based on a predefined duration mentioned in indonesian act. no. 2/2012, compared to the actual duration from 6 toll road projects using monte carlo simulation. the validity of model was tested using the section ii of cisumdawu toll road project. the simulation productivity result was 23.13 km/year, with a standard deviation of 6.704 km/year. meanwhile, the actual productivity was 20.50 km/year, which was still within the range of the simulation's standard deviation. hence, the models could reasonably describe the reality of the project. the most important activities that could affect land acquisition productivity performance were payment of compensation, the determination of compensation value, settlement of claims for the forms of compensation, and the identification and inventory of land ownership data. keywords: risk modelling, productivity performance, land acquisition, toll road, monte carlo 1. introduction indonesia is in a period of development. the toll road project is one of the infrastructure projects that the government claims to improve the transportation and logistics distribution sector. land acquisition, or eminent domain, creates the most obstacle in toll road development in indonesia [1]. the high level of uncertainty in land acquisition time and cost complicates the project owner’s attempt to determine any project risks. it makes the project financially unfeasible, hindering the government’s efforts to actualize the toll road project as a publicly funded one. in line with the statement above, [2] emphasize that land acquisition process has the highest risk during the project. after the construction, land and toll road are part of government’s assets. while 1 cite this as: putri, k., & marzuki, p. (2020). model of land acquisition productivity performance for toll road projects in indonesia. civil and environmental science journal (civense), 3(2), 84-94. doi: https://doi.org/10.21776/ub.civense.2020.00302.3 civil and environmental science journal vol. iii, no. 02, pp. 084-094, 2020 85 investors only have the rights to operate it during the concession period. the certainty of cost and duration of land acquisition is relatively low. hence the risk of cost overrun, and delayed time of operation becomes high. since the regulation states that land acquisition falls under the authority of the government, every risk following the delay in land acquisition becomes the responsibility of the government as well. the regulation of land acquisition in indonesia is issued in act. no. 2/2012 on land acquisition for land acquisition for development of public interest [3]. in construction projects, risks are inevitable. risks that are not seriously addressed in the initial planning will result in a cost overrun and delay in project completion. some previous studies mainly discuss the risks involved in toll road projects and their mitigation measures. some main obstacle factors resulted from [4] were the application process for establishment of development sites (surat permohonan penetapan lokasi pembangunan/sp2lp), the provision of residual land issues, and the delay in payment of compensation. meanwhile, based on [5] the three dominant risk source variables in toll road projects land acquisition were (a) the planning stage where investors do not immediately complete administrative requirements (6.2%); (b) the deliberation stage where complaints arise from the community (5.9%); (c) and the occurrence of land problems (5.6%). several researches have been focusing on risks on toll road projects. a study of risks analysis in trans sumatra toll road project [6] revealed that land acquisition was the main factor contributing to toll road projects delay. while from [7] five main risk factors identified in this project are: licensing risk, feasibility study, detailed engineering design, land acquisition and investment. the result of the research depicted that land acquisition was one of major factors that could affect toll road project implementation. unfortunately, the effect of existing risks on land acquisition productivity performance is rarely reviewed. thus, the aim of this study was to develop a model of land acquisition productivity performance to predict the duration for upcoming project. the source of this study includes seven schemes of land acquisition for toll road projects. the model can be used to determine the forecast value of land acquisition duration for the next projects. the results from this research were expected to provide a better understanding for both project owners and contractors to develop a better land acquisition schedule. 2. material and methods this research focused on the process of land acquisition based on act no. 2/2012 and conducted between september until december of 2016. since most of the toll road projects had already completed land acquisition planning and preparation (i.e., two of the four phases listed in the regulation), this research only observed main activity in phase iii, namely the implementation of land acquisition. subphases in each main activity is not observed due to lack of recording duration data in the field. the first two steps of land acquisition process were done by using old regulation namely presidential regulation no. 65/2006 on amendment of presidential regulation no. 36/2005 on land acquisition for development of public interest [8]. the earlier regulation does not mention about the maximum duration of each phase in land acquisition process, thus the implementation in the field becomes long and protracted. to generate a land acquisition productivity performance, the first step that needs to be done is to develop a probability density function (pdf) of the duration of the land acquisition project from existing projects in indonesia. the respondents included seven people from commitment-making official (pejabat pembuat komitmen) for land acquisition toll road project in indonesia. two data collected from toll road projects in sumatra, and five data from toll road projects in java. software fit distribution was used to generate the parameter of each pdf. the second step was to perform a monte carlo simulation using @risk software. this simulation was carried out to predict the performance of the duration of land acquisition in the next project. there is one project whose data will be compared with the results of the simulation to ensure that the results civil and environmental science journal vol. iii, no. 02, pp. 084-094, 2020 86 of the modelling can represent the actual conditions. the results of the both stages will be analysed to obtain conclusions from this study. 2.1. regulation of land acquisition for development of public interest it should be mention time and place of research in first part. all materials and methods that used such chemical for analysis, treatment and experimental design must be stated clearly and briefly. state the objectives of the work and provide an adequate background, avoiding a detailed literature survey or a summary of the results. a theory section should extend, not repeat, the background to the article already dealt with in the introduction and lays the foundation for further work. a calculation sections represents a practical development from a theoretical basis. to accelerate the process of land acquisition for public infrastructure development―including toll road projects, the government issues a regulation containing the maximum duration for each phase of land acquisition. the regulation is act. no. 2/2012 on land acquisition for development of public interest. the process contains the following four phases: phase i: land acquisition planning • feasibility study • the establishment of land acquisition planning document phase ii: land acquisition preparation • initial data collection (60 days) • public consultation (118 days) • the settlement of claims for compensation (107 days) phase iii: land acquisition implementation • the identification and inventory of land ownership data (79 days) • the determination of compensation value (90 days) • settlement of claims for the forms of compensation (102 days) • payment of compensation (35 days) phase iv: the delivery of land acquisition • the national land authority submits the land acquisition result to the ministry of public works (7 days) • land certification (30 days) each sub-phase has their own break-down explained in the regulation. although the maximum duration of land acquisition has been regulated, there are still many delays in the field. land acquisition is influenced by several factors, namely information dissemination process and community’s knowledge and legal awareness of a public project and the firm legal basis for its implementation [9]. 2.2. monte carlo simulation monte carlo simulation was chosen to develop a duration model because in the implementation of land acquisition process, there are some uncertainty resulted from its own procedures and parties involved. this distribution is more realistic to describe uncertainty in risk analysis. monte carlo simulation illustrates risk analysis by generating models of possible outcomes by replacing any factors that have inherent uncertainty with a range of values obtained from a probability density function (pdf). the probability density function is based on the data collection of the probability of occurrence for each factor. in this research, the pdf was built from the data of actual duration to finish each step-in land acquisition process from several of sample projects. the calculation to predict the upcoming duration of project is processed by selecting a random value from the probability density function. it calculates the results over and over-using different random value. the iteration can involve hundreds or even thousands of calculations. the simulation assigns a new probability density function to every possible outcome. civil and environmental science journal vol. iii, no. 02, pp. 084-094, 2020 87 2.3. data processing 2.3.1. generate probability density function (pdf) probability density function is needed as a basic value to perform the montecarlo simulation. to generate pdf, the primary data obtained from the questionnaire were as follows: • the time of the commencement of land acquisition • the percentage of completed land acquisition using the old regulation (i.e. presidential regulation no. 65/2006) • the percentage of completed land acquisition using the new regulation (i.e. act no. 2/2012) • the duration of each activity (as listed in the new regulation) that had been implemented in the field. • the obstacles experienced in implementing the new regulation. in this land acquisition, the scheduling was developed by modelling every phase as a series of activities. in other words, the relationship between the activities was finish to start (fs) as seen in figure 3. this method was based on the laws and regulations that provided a serial time limits for each activity. the actual duration or sequence may vary (as long as it complies with the regulation) based on the field. the source of uncertainty modelled in this study was the performance of the four activities in the implementation phase captured in figure 1. figure 1. the model of land acquisition duration for the main activities the data obtained from the interview were processed for data distribution using the fit distribution software. this step was applied to produce the performance distribution values of the four activities in the phase of land acquisition implementation for further analysis. a larger set of project data would create a better and more representative distribution. the length of land to be acquired is different for each project, yet the maximum time duration in the regulation is the same. hence, to make a model using different data from several projects, there should be a new variable that can show general comparison. in this study, productivity defined as ‘the speed of the team in conducting land acquisition, presented in km/year’. as mentioned above, some projects still use the old regulation to accomplish their land acquisition process. thus, in this research, there were a variable namely planned productivity which compared the remaining length of land that had not been acquired vs maximum duration allowed in act no. 2/2012. while actual productivity was defined as a comparison between the length of land that had been acquired using new regulation vs actual duration to acquired it. meanwhile, the land acquisition performance compares the completion time of actual land acquisition with the completion time planned. all data mentioned below were collected in september until december 2016. 𝑃𝑙𝑎𝑛𝑛𝑒𝑑 𝑃𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑣𝑖𝑡𝑦 (𝑃𝑃) = 𝑇ℎ𝑒 𝑟𝑒𝑚𝑎𝑖𝑛𝑖𝑛𝑔 𝑙𝑒𝑛𝑔ℎ𝑡 𝑜𝑓 𝑙𝑎𝑛𝑑 (𝑘𝑚) maximum duration allowed according to act no.2/2012(year) (1) 𝐴𝑐𝑡𝑢𝑎𝑙 𝑃𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑣𝑖𝑡𝑦 (𝐴𝑃) = 𝑇ℎ𝑒 𝑙𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑙𝑎𝑛𝑑 𝑎𝑐𝑞𝑢𝑖𝑟𝑒𝑑 𝑎𝑐𝑐𝑜𝑟𝑑𝑖𝑛𝑔 𝑡𝑜 𝐴𝑐𝑡 𝑁𝑜.2 / 2012 (𝑘𝑚) the actual duration in the field (year) (2) civil and environmental science journal vol. iii, no. 02, pp. 084-094, 2020 88 𝐿𝑎𝑛𝑑 𝐴𝑐𝑞𝑢𝑖𝑠𝑖𝑡𝑖𝑜𝑛 𝑃𝑒𝑟𝑓𝑜𝑟𝑚𝑎𝑛𝑐𝑒 = 𝐴𝑐𝑡𝑢𝑎𝑙 𝑃𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑣𝑖𝑡𝑦 𝑃𝑙𝑎𝑛𝑛𝑒𝑑 𝑃𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑣𝑖𝑡𝑦 × 100% (3) an example of calculation will be presented to illustrate the steps that had been done in this study. a summary of maximum duration allowed according to act no. 2/2012 can be seen in figure 1. for project 1, the data obtained from interview were as follow: phase: identification and inventory of land ownership data • planned duration (see figure 1): 79 days • take an assumption that number of working days in one year is 20 days per month x 12 month = 240 days • total length of toll road: 54,8 km • length acquired using old regulation: 7,7 km (14,05 % from total length) • remaining length to be acquired with new regulation: 54,8 km – 7,7 km = 47,11 km • planned productivity (see equation 1) pp = 47,11 𝑘𝑚 79 𝑑𝑎𝑦𝑠 240 𝑑𝑎𝑦𝑠 ×1 𝑦𝑒𝑎𝑟 = 𝟏𝟒𝟑, 𝟏 𝒌𝒎/𝒚𝒆𝒂𝒓 until the data were taken, the performance of land acquisition duration was as follows: • the length of land acquired using new regulation: 24,55 km • actual duration to complete the process: 134 days • actual productivity (see equation 2) ap = 24,55 𝑘𝑚 143 𝑑𝑎𝑦𝑠 240 𝑑𝑎𝑦𝑠 ×1 𝑦𝑒𝑎𝑟 = 𝟒𝟑, 𝟗𝟕 𝒌𝒎/𝒚𝒆𝒂𝒓 thus, the land acquisition performance was: • land acquisition performance (see equation 3) 43,97 km/year 143,1 km/year = 30,73 % these formulas were used to calculate the land acquisition performance of six projects at every implementation phase. the calculation results are mentioned in table 1. table 1. data of land acquisition performance to be plotted in probability density function (pdf) project name land acquisition performance (%) average identification and inventory of land ownership data determination of compensation value settlement of claims for the forms of compensation payment of compensation 1 project 1 30.73% 72.16% 26.58% 36.48% 41.49% 2 project 2 60.40% 67.57% 85.00% 49.44% 65.6% 3 project 3 85.58% 100.17% 82.88% 59.24% 81.97% 4 project 4 52.32% 72.00% 127.5% 106.06% 89.47% 5 project 5 28.30% 25.80% 26.18% 34.39% 28.67% 6 project 6 4.63% 8.19% 5.18% 14.23% 8.06% average 43.66% 57.65% 58.89% 49.97 % civil and environmental science journal vol. iii, no. 02, pp. 084-094, 2020 89 the obtained value from the calculation of the land acquisition performance was plotted. the data then being processed with best fit software to determine the type of distribution for each activities using software fit distribution. the probability density function (pdf) is summarized in table 2. table 2. the probability density function of every activity in the phase of land acquisition activity probability density function type of distribution parameter the identification and inventory of land ownership data left triangular (ramp down) 1st parameter (minimum) (a) : 0.0463 2nd parameter (most likely) (a) : 0.0463 3rd parameter (maximum) (b) : 1.0938 the determination of compensation value right triangular (ramp up) 1st parameter (minimum) (a) : 0.20044 2nd parameter (most likely) (b): 1.0017 3rd parameter (maximum) (b) : 1.0017 settlement of claims for the forms of compensation left triangular (ramp down) 1st parameter (minimum) (a) : 0.051289 2nd parameter (most likely) (a) : 0.051289 3rd parameter (maximum) (b) : 1.6072 payment of compensation left triangular (ramp down) 1st parameter (minimum) (a) : 0.14228 2nd parameter (most likely) (a) : 0.14228 3rd parameter (maksimum) (b) : 1.3294 2.3.2. monte carlo simulation the monte carlo simulation was performed after the distribution data of each activity was obtained using @risk software. in this study, the source of uncertainty is the productivity performance of each activity. the planned productivity is a fixed value according to the actual project data. this simulation aimed to determine the performance of the land acquisition duration for each activity. this information was obtained by taking a random value that was included in the data distribution acquired previously. a land acquisition project was selected as an input for the simulation. this project was the toll road connecting cileunyi, sumedang, and dawuan (cisumdawu) phase 2. the input data for simulation is planned productivity (pp). planned productivity was calculated using equation (3) based on the cisumdawu project data. the total productivity from the simulation was compared with the actual productivity of the cisumdawu toll road project for further analysis. if the value of the former approached the latter, then civil and environmental science journal vol. iii, no. 02, pp. 084-094, 2020 90 the simulation would be concluded as proper and representative of the value in the field. the input for the montecarlo simulation is listed in table 3. table 3. the input for the monte carlo simulation activities planned productivity (km/year) performance (%) (triangular) 1st paramet er 2nd paramet er 3rd paramet er the identification and inventory of land ownership data 8.96 0.395 0.046 0.046 1.094 the determination of compensation value 7.87 0.601 -0.200 1.002 1.002 settlement of claims for the forms of compensation 6.94 0.570 0.052 0.052 1.607 payment of compensation 20.23 0.538 0.142 0.142 1.329 when the simulation was run, the software would choose one random value based on the performance distribution (pdf) of each activity. the iteration was performed 10,000 times, and the result was a normally distributed risk output graph, as seen in figure 2. this figure illustrates the land acquisition productivity performance. figure 2. the results of the monte carlo simulation result parameter from simulation were listed below. • minimum : 9.874 (km/year) • maximum : 39.527 (km/year) • mean : 23.131 (km/year) • std. deviation : 6.704 (km/year) • median : 22.335 (km/year) the tornado diagram showed the extent to which an alternative value could shift due to a certain change in the quantity. the bars in the diagram represented the payoff range if a specific quantity (variable) was given a variation from one end to another in the relevant range by retaining all variables in their base values. the tornado diagram of the simulation is displayed in figure 3 below. civil and environmental science journal vol. iii, no. 02, pp. 084-094, 2020 91 figure 3. the tornado diagram of the monte carlo simulation results the most influential activities in this simulation are presented in the following sequence. 1. payment of compensation (in the form of money) 2. the determination of compensation value 3. settlement of claims for the forms of compensation 4. the identification and inventory of land ownership data this order shows that if the performances of the activities above are not good, it will likely influence the performance of the total project. thus, payment of compensation and the determination of compensation value are two most critical activities that need to give more attention. 2.3.3. validation and simulation result to validate or identify whether the performed simulation could represent the actual value, this research compared the productivity of the simulated land acquisition with the actual productivity. the simulation value obtained from multiplication between simulation mean (23.131 km/year) and percentage of each activity from total duration presented in table 2. while actual productivity obtained from interview data. the comparison can be seen in the table 4. table 4 comparison of actual and simulation productivity activities planned productivity (km/year) productivity weight simulation productivity (km/year) actual productivity (km/year) difference (km/year) total each activity (a) (c) = (a)/(b) (d) (e) = (c) / (d) (f) (g) = (f)– (e) the identification and inventory of land ownership data 8.96 20.37 % 23.131 4.71 4.9 -0.19 the determination of compensation value 7.87 17.88% 4.14 4.63 -0.49 settlement of claims for the forms of compensation 6.94 15.78% 3.65 2.81 0.84 payment of compensation 20.23 45.98% 10.63 8.16 2.47 total (b) 43.09 23.13 20.50 2.63 civil and environmental science journal vol. iii, no. 02, pp. 084-094, 2020 92 the simulation productivity was 23.13 km/year with a standard deviation of 6.704 km/year. meanwhile, the actual productivity was 20.50 km/year, which was still within the range of the standard deviation of the simulation productivity. this finding shows that the simulation results can represent the actual activities. observing the simulation results, the research was able to estimate the time required for completing the project with a predetermined probability and a certain confidence level (%). the simulated value was the performance value. a higher performance value provided an assumption that the project ran very fast (optimistic). yet in the land acquisition work, the confidence level value will be higher if the productivity plan is low. therefore, a little modification to the percentile value was necessary. the value of 90% became a confidence level of 10%, and 80% meant a confidence level of 20%, and so forth, the illustration can be seen in figure 4. therefore, the percentage in this simulation made more sense, as seen in table 5. figure 4 area of 90% confident level in land acquisition productivity performance table 5 standard distribution table for the simulation percentile zx forecast value productivity (km/year) 0% 1.95 36.20 10% 1.25 31.51 20% 0.84 28.76 30% 0.53 26.68 40% 0.25 24.81 50% 0 23.13 60% -0.25 21.46 70% -0.53 19.58 80% -0.84 17.50 90% -1.25 14.75 100% -1.95 10.06 for example, the calculation used to identify the project performance with a confidence level of 90% is as follows. probability: p (z < zx) = 90%; based on the normal standard distribution table, p (z < zx) = 90% has z = -1.25 𝑧𝑥 = 𝑥−𝑚𝑒𝑎𝑛 𝑆𝑡𝑎𝑛𝑑𝑎𝑟𝑑 𝐷𝑒𝑣𝑖𝑎𝑡𝑖𝑜𝑛 (4) −1,25 = 𝑥 − 23.131 6.704 𝑥 = 14.751𝑘𝑚/𝑦𝑒𝑎𝑟 the table shows that the confidence level affects the confidence in the performance of land acquisition duration. the value of 14.751 km/year can be used as a forecast value of land acquisition civil and environmental science journal vol. iii, no. 02, pp. 084-094, 2020 93 implementation process with confidence level of 90%. the value of productivity for each level of confidence can be seen in table 5. 3. result and discussion there were some facts reveals from the study above. according to table 1, the number of average duration implementation for each activity varied from 43.66 % up to 58,89%, the range of differences was not too high. it means that each activity's duration was mostly delayed for around 50% of the actual value determined by the regulation. nevertheless, if we look forward to each project's average productivity performance, the variation is extremely high. for example, from 8.06% to 89.47% for project 6 and project 4 respectively. it means that there were considerable differences in the government's ability to resolve the land acquisition problem. both projects were part of the national strategic project of indonesia. however, the performance of two example projects was dramatically different can be caused by the different priorities of each project. the national land agency's capacity was not enough since they also work for some other projects at the same time. because of this limitation, they probably choose the top priority project to be done first. based on interview and risk identification data, the main parties contributing to the risks are national land agency, district court or supreme court, and ministry of public works and housing to guarantee the existence and distribution of compensation money. public awareness of the importance of land acquisition for the public interest also needs to be improved to make it easier to cooperate in public consultation process. several problems that are mentioned quite often arise in land acquisition process are the different priority of project, the availability of compensation money, community participation, the limited resources of the national land agency, and time to complete the land acquisition claims in the district court and supreme court. the pdf of this research was able to run a simulation that can represent the actual value. by knowing the length of the road to be acquired and planned productivity, this simulation can help the government determine how many times needed to be allocated for the land acquisition process and become additional information on how to resolve the risk so that there is no delay in the predicted duration. if the duration seems too long, the government needs to pay more attention to the land acquisition project by giving an additional number of national land agency personnel, speeding up the settlement in the district and supreme court, and ensuring the disbursement of the fund. the focus of government plays a significant role in land acquisition projects. the decision making to speed up the process of land acquisition falls under the authority of the project-determining party, which is the head of the commitment-making official for land acquisition in toll road project. this study provides new additional information, namely the probability of project success with specific percentiles in a specified duration. nevertheless, project performance and completion remain dependent on the land acquisition implementation team in the field. 4. conclusions the number of average land acquisition productivity performance for each project shows an extremely big gap. this shows that some land acquisition activities could be completed very fast, and some are very slow for years. this depends on several problems that occur in the field such as the priority of project, the availability of compensation money, community participation, the limited resources of the national land agency, and time to complete the land acquisition claims in the district court and supreme court. the duration of land acquisition depending on some main parties i.e. are national land agency, district court or supreme court, and ministry of public works and housing. the actual productivity for validation was still within the range of standard deviation from simulation productivity. this finding shows that the simulation results can represent actual activities. the value of probabilistic density function (pdf) for each activity of land acquisition implementation can be used to forecast the duration of further projects. the most influential activities that could affect land acquisition productivity performance illustrated in tornado diagram was payment of compensation, the determination of compensation value, settlement of claims for the forms of compensation, and the civil and environmental science journal vol. iii, no. 02, pp. 084-094, 2020 94 identification and inventory of land ownership data respectively. thus, the first and second activities need to get more attention from the government. the data for this study obtained from 6 land acquisition for toll road projects during september until november of 2016. more additional data are needed to update the parameter of distribution (pdf) with current situation. the more data used, the better it will represent the actual condition. references [1] r. z. tamin, p. f. marzuki, and s. f. rostiyanti, “complex and uncertain land acquisition: one of major obstacles in toll road public private partnership (ppp) project in indonesia,” internet j. soc. soc. manag. syst., vol. 7, no. 1, pp. 1–8, 2011. [2] f. s. sunito, “an effort to break through the toll road investment barriers (in bahasa),” in the-8th indonesian national conference on road engineering, 2007. [3] the government of republic indonesia, indonesian act. number 2 of 2012 on land acquisition for development of public interest. indonesia, 2012. [4] s. sadono, “analysis of inhibitor factors in land acquisition of toll road projects,” master thesis report, civil engineering, universitas indonesia, 2007. [5] a. wibowo, a. tjan, and a. wibowo, “analisis resiko pengadaan tanah pada proyek pembangunan jalan tol,” master thesis report, civil engineering program, universitas parahyangan, 2011. [6] m. n. karunia, “analisis risiko keterlambatan waktu pada proyek (studi kasus: pembangunan jalan tol trans sumatera bakauheni-terbanggi besar (paket ii sidomulyo-kotabaru sta. 39+400 sta. 80+000) dan (paket iii kotabaru-metro sta. 80+000 – sta. 109+000)),” undergraduate thesis, civil engineering program, university of lampung, 2016. [7] a. sandhyavitri and n. saputra, “analisis risiko jalan tol tahap pra konstruksi (studi kasus jalan tol pekan baru-dumai),” j. tek. sipil, vol. 9, no. 1, pp. 1–19, 2019, doi: 10.28932/jts.v9i1.1366. [8] the government of republic indonesia, presidential regulation no. 65/2006 on amandement of presidential regulation no. 36/2005 on land acquisition for development of public interest. indonesia, 2006. [9] f. hermawan, f. kistiani, and t. d. santoso, “pengaruh pembebasan lahan terhadap risiko proyek konstruksi (studi kasus social engineering proyek jalan tol ruas semarang bawen),” teknik, vol. 32, no. 2, pp. 88–94, 2011. open access proceedings journal of physics: conference series civil and environmental science journal vol. 4, no. 1, pp. 093-105, 2021 93 bed-shear velocity measurement in curved open channel sumiadi1, b.a. kironoto2, djoko legono2, istiarto2 1 water resources engineering department, universitas brawijaya, malang, 65145, indonesia 2civil and environmental engineering department,universitas gadjah mada, yogyakarta, 55281, indonesia sumiadi_73@ub.ac.id1 received 12-01-2021; accepted 05-03-2021 abstract. generally, the condition of the rivers in indonesia are alluvial rivers which had meanders, where the change in the river bed topography often occur. one of the parameters associated with changes in the river bed topography is bed-shear velocity, or reynolds stress. the bed-shear velocity can be calculated by the reynolds stress distribution method and the clauser method which commonly used in straight channels. in fact, on natural channel there is a curve and even a meandering channel. with more complex flow conditions, the use of the clauser method in curved channels can be questioned, is it still accurate or not. in this paper, both methods will be discussed by comparing the measurement data in the laboratory using 180 curved channel with flat bed. the results of data analysis show that the use of these two methods in curved channels produces an average difference of around 19.81%, where the clauser method gives greater results and better tendencies. apart from the differences in the results given, it can be said that the clauser method as well as the reynolds stress distribution method can still be used to calculate the bed-shear velocity in the curved channel. keywords: bed-shear velocity, clauser method, curved open channel, reynolds shear stress 1. introduction generally, river conditions in indonesia are meandering and alluvial rivers where the bed material in the form of sand, gravel or clay is easily transported by the flow. flows in natural rivers and channels are often unsteady. field studies show that, during the passage of a flood, the bed-load movement is different from those in steady flow[8]. with these conditions, efforts to control the destructive power of the river become a difficult challenge. one aspect that needs attention is the change in the riverbed due to degradation and aggression. one of the parameters associated with the process of channel bed profile changing is the shear velocity parameter, u*, or shear stress on the bed, τo. shear velocity is determined using velocity profile data, particularly those measured in the inner layer. in loose gravel bed flows, a roughness layer develops just above the bed, thus affecting the lower end of the inner layer velocity profile [6][5]. under certain conditions, it may be difficult to obtain reliable velocity profile data, 1 cite this as: sumiadi, kironoto, b.a., legono, d., & istiarto. (2021). bed-shear velocity measurement in curved open channel. civil and environmental science journal (civense), 4(1), 84-92. doi: https://doi.org/10.21776/ub.civense.2021.00401.9 civil and environmental science journal vol. 4, no. 1, pp. 093-105, 2021 94 particularly in the field. in that case, shear velocity must be estimated from single point measurements [2]. in alluvial rivers that are relatively straight, the effect of flow on the bed shear stress or velocity will be different when compared to the effect of flow on a curve. when the flow enters the curve, there is an increase in secondary flow and triggers an increase in the bed-shear velocity or bed-shear stress. the increase in bed shear velocity results in scouring, especially on the outer bank and settling on the inner bank. 2. material and methods 2.1. methods to determine the bed shear velocity, u*, in uniform flow, there are several methods that can be used, namely [1]: 1. energy gradient method 2. clauser method 3. reynolds stress distribution method. from the three methods mentioned above, in this paper only the last two methods will be discussed, namely the clauser method, which uses tangential velocity measurement data and the second method using reynolds stress measurement data. while the first method is rather difficult to use, because it is not easy to determine the energy gradient on the curved channel. 2.1.1. clauser method at the clauser method, the bed-shear velocity is obtained based on the tangential velocity profile. with the assumption that the tangential velocity distribution in the inner region follows the logarithmic equation formulated as : 𝑣θ 𝑢∗ = 1 κ ln ( 𝑧 𝑘𝑠 ) + 𝐵𝑟 (1) if the left side and the right side is multiplied by the bed-shear velocity, u* then equation 1 becomes: 𝑣θ = 𝑢∗ κ ln ( 𝑧 𝑘𝑠 ) + 𝐵𝑟 ∙ 𝑢∗ (2) 𝑣θ is tangential velocity (m/s), 𝑢∗ is bed-shear velocity (m/s), z: distance from bed-surface (m), 𝑘s: bed roughness (m), : von karman's constant, br: constant of integration. based on equation 2, it is known that the tangential velocity vertical distribution 𝑣θ to ln ( 𝑧 𝑘𝑠 ) is linear, with a gradient of 𝑢∗ κ . 2.1.2. reynolds stress distribution method in turbulent flow, instantaneous velocity can be separated into two components, namely the average velocity towards time (time average velocity) and velocity fluctuations as illustrated in figure 1 below. figure 1. averaging velocity towards time. t u u(t) 𝑢ത civil and environmental science journal vol. 4, no. 1, pp. 093-105, 2021 95 so that it can be written in the form : 𝑢 = 𝑢ത + 𝑢′ (3) where: 𝑢 : longitudinal velocity (m/s) 𝑢ത : average velocity (m/s) 𝑢′ : velocity fluctuations, can be positive or negative (m/s) referring to equation 3, then for 3d flow in a curved channel, which consists of tangential, radial and vertical direction velocity components, it can be written as : 𝑣𝜃 = 𝑣𝜃തതത + 𝑣𝜃 ′ 𝑣𝑟 = 𝑣�̅� + 𝑣𝑟 ′ 𝑣𝑧 = 𝑣�̅� + 𝑣𝑧 ′ (4) with 𝑣𝜃 , 𝑣𝑟 , 𝑣𝑧 are the component of instantaneous velocity, 𝑣𝜃തതത, 𝑣�̅�, 𝑣�̅� average velocity component and 𝑣𝜃 ′ , 𝑣𝑟 ′, 𝑣𝑧 ′ are the velocity fluctuation component, respectively in the tangential direction, , radial direction, r, and vertical direction, z. from equation 4, then the value of velocity fluctuations 𝑣𝜃 ′ , 𝑣𝑟 ′, 𝑣𝑧 ′ can be stated as: 𝑣𝜃 ′ = 𝑣𝜃 − 𝑣𝜃തതത 𝑣𝑟 ′ = 𝑣𝑟 − 𝑣�̅� 𝑣𝑧 ′ = 𝑣𝑧 − 𝑣�̅� (5) using equation 5, the magnitude of instantaneous velocity fluctuations can be calculated. while the shear stress in turbulent flow the shear stress acting on the plane i of the direction j is formulated as: ji i j j i ij uu x u x u −           +   = (6) the first term on the right shows the stress caused by the viscosity of water, (𝜐), while the last term shows the effect of velocity fluctuations and is known as the reynolds stress. in turbulent flow, the stress caused by the influence of velocity fluctuations (turbulence) is far greater than the stress due to water viscosity. so that the shear stress due to viscosity of water can be ignored. then equation (6) becomes: jiij uu −= (7) for flow in the curved channel, using cylindrical coordinates (, r, z) then for the z field, there are 3 shear stresses, i.e.: τ𝑧𝑧 = −ρ𝑣𝑧 ′𝑣𝑧 ′തതതതതത (8) τ𝑧𝑟 = −ρ𝑣𝑧 ′𝑣𝑟 ′തതതതതത (9) τ𝑧𝜃 = −ρ𝑣𝑧 ′𝑣𝜃 ′തതതതതത (10) where τ𝑧𝑧 is a normal component of shear stress or often referred to as normal stress, while τ𝑧𝑟 and τ𝑧𝜃 respectively are components of shear stress in radial and tangential directions or often referred to as reynolds stresses. furthermore, what is discussed in this paper is reynolds stress in the tangential direction, τ𝑧𝜃 . referring to equation 10, the bed shear stress, o (tangential direction) can be obtained from measurement data of reynolds stress distribution in the tangential direction, τ𝑧𝜃 , for the value of z = 0, namely z|z=0τoby extrapolating (or regression) measurement data for tangential reynolds stress distribution, τ𝑧𝜃 , at z = 0, namely: civil and environmental science journal vol. 4, no. 1, pp. 093-105, 2021 96 τo = 𝜌𝑢∗ 2 = τ𝑧𝜃,𝑧=0 = −𝜌𝑣𝑧 ′𝑣𝜃 ′തതതതതത| 𝑧=0 (11) or: τo 𝜌 = 𝑢∗ 2 = −𝑣𝑧 ′ 𝑣𝜃 ′തതതതതത| 𝑧=0 (12) based on equation 12, then the bed-shear velocity can be derived. 2.2. material 2.2.1. experiments this research was conducted at the hydraulic laboratory, department of civil and environmental engineering, universitas gadjah mada using 180 curved channel with flat bed. three-dimensional velocity measurements include tangential velocity (𝑣θ), radial velocity (𝑣𝑟) and vertical velocity (𝑣𝑧). before entering the curved channel, flow through the approach channel (approach flow). in the upstream of the approach flow also fitted with head tank – to ensure steady/permanent flow conditions – and thompson type discharge meter. furthermore, the flow parameters in the approach flow in detailed are shown in table 1 below. table 1. flow parameter in approach flow. q b h 𝑹𝒉 𝒅𝟓𝟎 s u c re fr b/h (l/s) (cm) (cm) (cm) (cm) (o oo⁄ ) (cm) (𝑚 1/2 𝑠⁄ ) (103) 24.2 50 15.9 9.7 1.0 0.7 30.4 37 54 0.24 3.1 2.2.2. equipment and instrumentation a. channel the channel or flume used in this study is an acrylic walled channel. this channel successively from upstream to downstream consists of 3 parts namely: approach channel (approach flow) as long as 8 m, curved section 180 with axles radius, r = 1.25 m and downstream section (downstream) as long as 6 m. to ensure the flow condition is a steady flow, then the flow is supplied from the head tank in the upstream section which is equipped with an overflow and a triangular overflow type measuring instrument. the detailed research sketch is presented in figure 2. b. bed material the bed material used in this study is black sand, with a diameter of 0.8 1.2 mm and a mass density of 2.65gr/cm3. c. measuring instrument the measuring instrument used in this study includes flow velocity measuring devices, discharge measuring instrument, water level/table gauge, bed topographic measuring instruments and time measuring instruments. the flow velocity measuring instrument used is the adv type microadv 16 mhz with the ability to read instantaneous flow velocity up to 50 data per second. civil and environmental science journal vol. 4, no. 1, pp. 093-105, 2021 97 figure 2. sketch of curved open channel the measurement of 3d velocity distribution in this study was carried out on seven curved angle section, i.e. at an angle of 0, 30, 60, 90, 120, 150, and 180, plus one measurement at approach flow. at each section carried out five measurements of vertical distribution, namely at position r = 105, 115, 125, 135, and 145 cm. the vertical distance between measurement points is 0.3 cm for data near the bed (inner region, at z/h ≤ 0,2), and 1 cm for data in the outer region. because of the shape and size of the probe adv, there is a part of the flow that cannot be measured namely at a depth of about 5 cm below the water surface, and 5 cm width near the channel wall (see figure 3) figure 3. velocity measurement point in each cross section r 1 2 5 hu150 hu250 c0 c30 c 6 0 c 9 0c 1 2 0 c1 50 c180 hi100 2 ,0 0 8 ,0 0 6 ,0 0 cl cl inlet kolam penenang outlet kolam outlet not measured area measured area civil and environmental science journal vol. 4, no. 1, pp. 093-105, 2021 98 then the measurement data obtained is coded c and r. for example, the data series with code c30r105 means that measurement is made in cross section c = 30 and at the radius position, r = 105 cm. the following is shown the 3d flow velocity data collection method with adv: gambar 3. metode pengambilan data dengan adv figure 4. the data measurement method with adv flow measurement using micro adv is also equipped with sontek horison adv software so that measured data can be displayed in real time on a computer screen. 3. result and discussion 3.1. velocity distribution in figure 4 is given examples of the typical measurement results of velocity distributions with tangential, radial and vertical direction on the curved angle of 90. for determining the shear velocity using the clauser method, tangential directional velocity distribution data is used, especially in the inner region. figure 5. the velocity distribution in the direction of : (a) tangential, (b) radial and (c) vertical at the section of 90 splash-proof housing computer flume probe adv display data civil and environmental science journal vol. 4, no. 1, pp. 093-105, 2021 99 the tangential velocity distribution, for r115 data shows a shape that tends to close in the outer region (z/h >0,2), while on the inner region (z/h ≤0,2), the shape of the velocity distribution showing trends similar to the flow in a straight channel (figure 5). for radial direction velocity, up to the depth of z/h 0.3, radial velocity has a negative value, which means that the direction of the radial velocity toward the inside of the curve; while at z/h> 0.3 the velocity has a positive value, which indicates that the direction of the radial velocity towards the outside of the curve. whereas for the component of vertical direction velocity, the velocity value near the bed tends to be smaller compared to the velocity at a location far from the bed. 3.2. reynolds shear stress distribution the following is shown a typical example of the measurement results of the tangential directional reynolds shear stress distribution on several curved channel section. seen in figure 6, the shape of the reynolds stress vertical distribution −𝑣𝑧 ′𝑣𝜃 ′തതതതതത and reaches zero values at the water surface (extrapolation results). kironoto and graf (1995) shows that the shape of the reynolds stress distribution is linear for uniform flow, and nonlinear (concave or convex) for non-uniform flow, depending on whether the flow is accelerated or slowed. figure 6. reynolds stress distribution in curved inlet, c0 by using the regression method, the reynolds stress vertical distribution equation is obtained −𝑣𝑧 ′𝑣𝜃 ′തതതതതത in the curved inlet follows the following equation: τ𝑧𝜃 𝜌 = 0.3𝑢∗ 2 (1 − 𝑧 ℎ ) (13) as for areas that very close to the bed, theoretically the influence of flow viscosity is more dominant than velocity fluctuations. the flow velocity will also be close to zero on the bed surface (z/h = 0), as well as the value of velocity fluctuations. as a result the reynolds stress distribution decreases and approaches zero as shown by 3 data near the bed. thus it can be said that for areas that very close to the bed, shear stress is the total stress due to velocity fluctuations and flow viscosity. 0 0.2 0.4 0.6 0.8 1 0 0.5 1 1.5 2 c0 r115 −𝑣𝑧 ′𝑣𝜃 ′തതതതതത τ𝑧𝜃 𝜌 = 0.3𝑢∗ 2 (1 − 𝑧 ℎ ) civil and environmental science journal vol. 4, no. 1, pp. 093-105, 2021 100 furthermore, with the increase in curved angle, the vertical distribution of the reynolds stress changes to non-linear even begin at 120 curved angle in outer region (z/h 0.2), the reynolds voltage has negative value as shown in figure 5.28 below. the influence of the centrifugal force on the flow in the curved channel causes the flow to accelerate, especially on the outside of the bend and deceleration on the inner side of the bend so that the shape of the reynolds shear stress distribution is not linear. figure 7. reynolds shear stress distribution in curved channels for data: (a). c60r125, (b) c120r125 and (c) c180r115 0 0.2 0.4 0.6 0.8 1 -0.5 0 0.5 1 1.5 c60 r125 0 0.2 0.4 0.6 0.8 1 -0.5 0 0.5 1 1.5 c180 r115 -0.5 0 0.5 1 1.5 c120 r125 𝑧 ℎ −𝑣𝑧 ′𝑣𝜃 ′തതതതതത −𝑣𝑧 ′𝑣𝜃 ′തതതതതത −𝑣𝑧 ′𝑣𝜃 ′തതതതതത civil and environmental science journal vol. 4, no. 1, pp. 093-105, 2021 101 3.3. bed-shear velocity in figure 5 below is shown the example of u* calculation with the clauser method, for data c30r145. the plot of tangential velocity measurement data as the y axis and ln (z/ks) as the x axis, where ks is a bed roughness. with the linear regression method obtained a straight line with a gradient of u*/ and intersect the y-axis at coordinates (0; br. u*). with the same principle, can be calculated the value of the shear velocity, u*, for all data in the curved channel using the clauser method. the results of the shear velocity calculation using the clauser method in detailed presented in table 2. figure 8. example application of the clauser method for data c30r145 table 2. value of bed-shear velocity, 𝑢∗ and constant br with clauser method r145 r135 r125 r115 r105 u * 1.711 1.653 1.566 1.575 1.815 br 9.205 10.204 11.947 10.803 8.283 u * 1.911 1.854 1.935 1.903 1.922 br 7.078 8.279 7.896 7.640 8.960 u * 1.942 2.133 2.212 2.261 2.474 br 6.827 6.442 6.070 6.676 6.574 u * 2.394 2.456 2.372 2.436 2.419 br 5.284 6.043 6.554 6.079 5.748 u * 2.277 2.382 2.317 2.368 2.314 br 8.110 7.802 8.804 8.328 8.395 u * 2.098 2.264 2.365 2.241 2.268 br 9.603 8.027 8.325 8.216 8.763 u * 2.166 2.492 2.588 2.402 2.624 br 8.745 6.696 5.965 6.330 5.539 u * 2.207 2.258 2.197 2.222 2.287 br 9.919 8.793 8.045 6.181 6.096 radius kode parameter af c150 c180 c0 c30 c60 c90 c120 𝑢∗ 𝜅 𝐵𝑟 ∙ 𝑢∗ 𝑣 𝜃 (c m / s) code civil and environmental science journal vol. 4, no. 1, pp. 093-105, 2021 102 the following is an example of the data analysis of the reynolds stress distribution on c120r135 data to obtain the value of the radial and transversal bed shear velocity. furthermore, the total shear velocity value is the resultant of both. figure 9. example of the applications of the reynolds stress distribution method for c120r135 data in the same way, all of the reynolds stress distribution data for other section can be calculated and the results in detailed presented in table 3. in table 3, the number of tangential flow velocity data is also included –especially in inner region which still follows logarithmic equations and is given a notation: n. based on the analysis of the data in table 3, it is known that for the flow in the straight channel (sequence number 1 to 5), the clauser method and the reynolds stress distribution method produce relatively the same shear velocity where the average difference is 1.97%. similarly in the curved inlet area (c0), the average difference is still relatively small at 3.78%. whereas in the curved channel with the curve angle of 30 until 180 it can be seen that the two methods give different results where the clauser method tends to produce a shear velocity value greater than the reynolds stress distribution method with an average difference of 19.81%. based on the bed shear velocity values obtained, it can be said that the clauser method gives better results indicated by the value of the shear velocity in the curved section which is greater than the value of the bed shear velocity in the straight channel section. from table 3. it is also known that the shear velocity obtained by the clauser method and the reynolds stress distribution on the straight channel (approach flow) with hucl code shows a relatively equal value with the average difference of 2.067%. as well as in the curve inlet area, the average difference between the two methods is still acceptable namely 3.565%. further at curve angle of =30 until 180, clauser method produces a greater shear velocity value than the reynolds stress distribution method with an average difference of 2.693%. comparison of the results of the two methods is shown in figure 10. 0 5 10 15 20 -2 0 2 4 z (c m ) c120 r135 −𝑣𝑧 ′𝑣𝜃 ′തതതതതത 0 5 10 15 20 -4 -2 0 2 4 c120 r105 -4 -2 0 2 4 c120 r115 0 5 10 15 20 -4 -2 0 2 4 c120 r125 -4 -2 0 2 4 c120 r135 0 5 10 15 20 -4 -2 0 2 4 (cm2/s2) c120 r145 −𝑣𝑧 ′𝑣𝑟 ′തതതതതത 𝑢∗𝑟 = −0.648 cm/s 𝑢∗𝑡 = 1.797 cm/s civil and environmental science journal vol. 4, no. 1, pp. 093-105, 2021 103 table 3. bed-shear veocity according to distribution of reynolds stress method and clauser method perbedaan n (%) 1 hucl+20 1.710 0 1.710 8 1.711 0.021 2 hucl+10 1.658 0 1.658 8 1.653 0.299 3 hucl 1.523 0 1.523 8 1.566 2.828 4 hucl-10 1.565 0 1.565 9 1.575 0.600 5 hucl-20 1.703 0 1.703 10 1.815 6.589 6 c0r105 1.871 -0.548 1.949 8 1.922 1.400 7 c0r115 1.766 -0.566 1.855 8 1.903 2.596 8 c0r125 1.901 -0.693 2.023 8 1.935 4.351 9 c0r135 1.849 -0.787 2.010 9 1.854 7.740 10 c0r145 1.778 -0.608 1.879 9 1.911 1.736 11 c30r105 1.957 -0.620 2.053 8 2.474 20.498 12 c30r115 1.670 -0.470 1.735 8 2.261 30.304 13 c30r125 1.817 -0.580 1.907 8 2.212 15.974 14 c30r135 1.720 -0.570 1.812 8 2.133 17.671 15 c30r145 1.616 -0.550 1.707 8 1.942 13.810 16 c60r105 1.936 -0.806 2.098 8 2.419 15.335 17 c60r115 1.764 -0.728 1.908 8 2.436 27.679 18 c60r125 1.718 -0.663 1.841 8 2.372 28.807 19 c60r135 1.822 -0.742 1.967 9 2.456 24.821 20 c60r145 1.661 -0.583 1.761 8 2.394 35.969 21 c90r105 1.825 -0.866 2.020 9 2.314 14.554 22 c90r115 1.811 -0.806 1.982 9 2.368 19.441 23 c90r125 1.808 -0.800 1.977 9 2.317 17.156 24 c90r135 1.797 -0.648 1.910 10 2.382 24.691 25 c90r145 1.453 -0.548 1.552 9 2.277 46.675 26 c120r105 1.910 -0.742 2.049 9 2.268 10.682 27 c120r115 1.903 -0.872 2.093 8 2.241 7.071 28 c120r125 1.931 -0.922 2.140 8 2.365 10.518 29 c120r135 1.797 -0.632 1.905 9 2.264 18.809 30 c120r145 1.616 -0.781 1.794 10 2.098 16.938 31 c150r105 1.977 -0.787 2.128 9 2.624 23.277 32 c150r115 1.954 -0.849 2.131 9 2.402 12.720 33 c150r125 1.865 -0.889 2.066 9 2.588 25.251 34 c150r135 1.741 -0.671 1.865 9 2.492 33.597 35 c150r145 1.565 -0.640 1.691 9 2.166 28.052 36 c180r105 1.967 -0.632 2.066 8 2.287 10.661 37 c180r115 1.755 -0.707 1.892 8 2.222 17.460 38 c180r125 1.876 -0.775 2.030 9 2.197 8.227 39 c180r135 1.800 -0.548 1.881 9 2.258 20.001 40 c180r145 1.706 -0.500 1.778 6 2.207 24.137 metode clausermetode dist. tegangan reynolds no kode 9 5.2 6.5 7.8 𝑢∗𝐶𝑙 𝑢∗𝑅𝑒 𝑢∗𝑡 𝑢∗𝑟 different code dist. of reynolds stress method clauser method civil and environmental science journal vol. 4, no. 1, pp. 093-105, 2021 104 figure 10. comparison of the bed shear velocity values based on the reynolds stress distribution and the clauser method 4. conclusions flow parameters in the form of shear velocities can be calculated using the clauser method based on the velocity distribution data and the reynolds shear stress distribution method. the results of calculations with both methods on a straight channel (approach flow) produce a bed-shear velocity value which relatively equal to the average difference of 1.97%. whereas in the curved channel, the results of the calculation of the two methods give an average difference of 19.81% where the clauser method gives greater results compared to the reynolds stress distribution method. in general, the clauser method gives greater results compared to the reynolds stress distribution method. apart from the difference of up to 19.81%, it can be said that in the flow in the curved channel, the bed-shear velocity can still be calculated using the clauser method or based on the reynolds shear stress distribution method. acknowledgements head of hydraulic laboratory university of gadjah mada, for the support of the laboratory and the research tools (adv and 180⁰ curved flume). references [1] b.a. kironoto, b. yulistiyanto, istiarto, sumiadi, a. ariyanto, 2012. the effect of bed shear stress on bed topography changes, proceedings of annual scientific meeting hathi xxix, bandung. [2] bagherimiyab, f. and lemmin, u. 2013. shear velocity estimates in rough-bed open-channel flow. earth surf. process and landforms 38, 1714–1724 [3] graf, w.h., 1998. fluvial hydraulics, published by john wiley & son ltd, west sussex, uk. [4] jin, y-c., steffler, p.m. and hicks, f.e., 1990. roughness effects on flow and shear stress near outside bank of curved channel, journal of hydraulic engineering, 116(4), 563-577. [5] nikora vi, smart gm. 1997. turbulence characteristics of new zealand gravel-bed rivers. journal of hydraulic engineering asce 123: 764–773. [6] raupach mr. 1981. conditional statistics of reynolds shear stress in rough-wall and smoothwall turbulent boundary layers. journal of fluid mechanics 108: 363–382. [7] song, t. and graf, w.h., 1996. velocity and turbulence distribution in unsteady open-channel flow, journal of hydraulic engineering, 122(3), 141-154. 0 1 2 3 4 0 1 2 3 4 u * r e u*cl af c0 c30 c60 c90 c120 c150 c180 𝑢∗𝐶𝑙 (cm/s) 𝑢 ∗ 𝑅 𝑒 ( c m /s ) civil and environmental science journal vol. 4, no. 1, pp. 093-105, 2021 105 [8] song, t. and chiew, y.m., 2001. turbulent measurement in non-uniform open-channel flow using acoustic doppler velocimeter (adv), journal of engineering mechanics, 127(3), 219232. [9] sumiadi, istiarto, b.a. kironoto and d. legono, 2011. developing laboratory experiment o n flow in an erodible curved channel, disajikan pada the 4th asean civil engineering conference, yogyakarta. [10] sumiadi, b.a. kironoto, d. legono and istiarto, 2011. flow characteristics in eroded-bed curved channel, proceedings of civil enginerring post graduate conference (knpts), bandung. [11] sumiadi, b.a. kironoto, d. legono and istiarto, 2012. distribution of turbulence intensity in alluvial channel bend, proceedings of annual scientific meeting hathi xxix, bandung. civil and environmental science journal vol. 4, no. 1, pp. 084-092, 2021 84 mode choice modelling between bus and train under the new normal condition willy kriswardhana1, akhmad hasanuddin1, daud rosyid r.a. muntsari1 1 department of civil engineering, universitas jember, jember, 68121, indonesia willy.teknik@unej.ac.id1 received 10-01-2021; accepted 15-02-2021 abstract. the passenger movements were limited by the government policies that made new system decisions, namely large-scale social distancing policies. however, over time several regions in indonesia have begun to end large-scale social distancing called new normal. the new normal condition has undoubtedly changed the pattern of mode choice of the passenger. little attention has been paid to the travel mode choice under the new normal condition. therefore, this study aims to understand the travel mode choice model of train and bus, especially in the new normal era. the primary data was collected using the stated preference online-based survey. this study performed a binomial-logit-difference model. from the modelling result, 89% of the passenger will choose the bus if the train's travel fare is idr 160,000 higher. the probability value will be equal when the bus fare is idr 25,000 higher than the train’s travel cost. it indicates that people choose the bus mode because of the travel cost factor. directions for the future study are presented. keywords: bus, new normal, mode choice, train 1. introduction the trans-java toll road is a toll road network that connects various cities from west to east on java. the trans-java toll road also connects indonesia's two largest cities, jakarta and surabaya. the existence of the trans-java toll road has significantly reduced travel time between surabaya-jakarta and jakarta-surabaya. before the trans-java toll road presence, surabaya's travel time to jakarta was 20 hours; now with the trans-java toll road, it can be reached in 11-13 hours. the impact of reduced travel time will undoubtedly lead to more competitive competition between the bus and train modes. however, in the new normal condition, the behaviour of travel mode choice might be changing. the covid-19 pandemic in indonesia caused almost all movements or activities to be restricted to reduce transmission of the covid-19 virus. the passenger movements were limited by the government policies that made new system decisions, namely large-scale social distancing policies. however, over time several regions in indonesia have begun to end large-scale social distancing called new normal. 1 cite this as: kriswardhana, w., hasanuddin, a., & muntsari, d.r.r.a. (2021). mode choice modelling between bus and train under the new normal condition. civil and environmental science journal (civense), 4(1), 84-92. doi: https://doi.org/10.21776/ub.civense.2021.00401.8 civil and environmental science journal vol. 4, no. 1, pp. 084-092, 2021 85 the new normal condition has undoubtedly changed the pattern of mode choice of the passenger. in march 2020, when covid-19 pandemic started, the transportation sector has been influenced. in indonesia, the train passenger must have a letter confirming that the passenger is healthy. according to pt kereta api indonesia (pt kai), long-distance train customers in java island are required to show a negative antigen rapid test result as a condition for taking a train. the test is provided by pt kai, and it requires customers to pay more (the fee of the test is excluding from the ticket price). meanwhile, some bus operators do not require their customers to show the health test. some factors influence the behaviour of travel mode choice. travel cost is the essential attribute of mode choice, followed by travel time, punctuality, access time, and connection type [1]. the extra cost could lead to a movement of passengers’ travel modes. a study in barcelona stated that the cost variable influenced the mode choice behaviour. when the costs of travelling by car increase, the probability of rail-based transportation chosen by the customers will be higher than the car [2]. furthermore, in australia, customers' one-way cost is a significant factor in influencing the perceived satisfaction with train fares [3]. some factors like income and vehicle ownership also found to be significant in influencing the mode choice behaviour in srilanka [4]. the preference heterogeneity of mode choice in australia was partially explained by the intercity differences, user group status, income, and trip purposes [5] in indonesia, some studies have developed the travel mode choice model between bus and train. a study analysing the travel mode choice from yogyakarta to solo stated that the train mode is more desirable than buses. the average price difference is idr -162,000 (train is way cheaper than the bus) [6]. similarly, some studies also stated that train mode is more preferred because the fare is cheaper than bus [7][8]. however, in the new normal condition, the extra cost of taking a train could decrease the market share. passengers, who think that the travel fare is essential, will be influenced by the regulation. comparing to developed countries, the study of mode choice is less developed in developing countries [9]. moreover, little attention has been paid to the travel mode choice under the new normal condition. therefore, this study aims to understand the travel mode choice model of train and bus, especially in the new normal era. figure 1. surabaya-jakarta bus and train route civil and environmental science journal vol. 4, no. 1, pp. 084-092, 2021 86 2. material and methods 2.1. case study this paper studied a route of bus and train; it was surabaya-jakarta. surabaya-jakarta route represents the long-distance travel (781 km) (figure 1). the research was conducted at the initial departure point for bus and train passengers. the research location and data collection were carried out in four places, including purabaya bus station and surabaya pasar turi railway station. figure 2. number of passengers of train and bus in 2019 (source: upt terminal bungurasih and pt kai (persero)) figure 2 indicates that bus is the more preferable mode than train in the surabaya-jakarta route. people tend to travel by bus because of its flexibility and easier bus station access. 2.2. stated preference survey the primary data was collected using the stated preference online-based survey. the stated preference technique is a data collection technique refers to the approach to the opinion of respondents in dealing with various alternative choices. this technique uses an experimental design for creating alternative imaginary situations [10]. general characteristics such as gender, age, occupation, income, origin/destination, and purpose of travel were asked to the respondents. apart from the characteristics of the users of modes, an analysis is also carried out based on considerations of cost—data obtained by distributing questionnaires to prospective bus and train passengers. table 1. a stated preference survey of the study ticket fare of bus ticket fare of train gap of ticket fare preferencesa 1 2 3 4 5 idr 375.000 idr 535.000 ­ idr 160.000 this section was filled by the respondents idr 425.000 idr 535.000 ­ idr 110.000 idr 470.000 idr 535.000 ­ idr 60.000 idr 470.000 idr 485.000 ­ idr 10.000 idr 470.000 idr 435.000 idr 40.000 a option (1): definitely choose the bus; (2): maybe choose a bus; (3): balanced choice; (4): maybe choose a train; (5): definitely choose a train 8000 9000 10000 11000 12000 13000 14000 15000 16000 17000 0 2 4 6 8 10 12 n u m b e r o f p a ss e n g e rs month bus train civil and environmental science journal vol. 4, no. 1, pp. 084-092, 2021 87 the number of populations in this study, both buses and trains, was taken from the average number of passengers on the surabaya-jakarta route (table 1). then, the calculation of the sample was carried out using the slovin formula with the desired accuracy level of 95%, so that the error tolerance limit (e) = 5%. a total of 425 respondents filled the questionnaires. the survey was carried out from september to december 2020. besides the household characteristics, the mode choice characteristics were asked to the respondents. the questions regarding the mode choice characteristics are the difference in travel cost, the difference in travel time between train and bus, and access time. the cost of health test (idr 80,000) was added to the total travel fare of the train. 2.3. data analysis this study performed a binomial-logit-difference model using probability value calculations, model validation analysis, and sensitivity analysis. the binomial-logit-difference model is used to calculate the probability value of the mode choice of transportation between buses and trains. as a result of modelling the binomial-logit-difference stage, the proportion of opportunities for each mode of transportation to be selected by travelers are obtained. the utility function is to measure each choice given to the respondent. this function reflects the effect of the respondent's choice on all the attributes included in the stated preference. generally, utility functions are linear, as follows: 𝑈𝑗 = 𝑎 + 𝑏1𝑥1 + 𝑏2𝑥2 + ⋯ + 𝑏𝑛𝑋𝑛 (1) where uj = choice utility j; a, b1,…, bn = model parameters and; x1, x2,…, xn = attribute value the objective of the analysis is to determine the estimated values to which the values are referred to as the option weights or the utility component. from the model parameter values can be the relative effect of each attribute on the entire utility. after the utility component can be estimated, it can then be used for various purposes, such as determining the relative importance of the experiment's attributes and determining the utility function for model forecasting. furthermore, to find out the probability of each mode of transportation, the binomial logit equation is used by entering the utility value of the transportation mode obtained previously using the formula: 𝑃𝑏𝑢𝑠 = 𝑒𝑈𝑏𝑢𝑠 𝑒𝑈𝑏𝑢𝑠+𝑒𝑈𝑡𝑟𝑎𝑖𝑛 = 𝑒(𝑈𝑏𝑢𝑠 − 𝑈𝑡𝑟𝑎𝑖𝑛) 1+ 𝑒(𝑈𝑏𝑢𝑠 − 𝑈𝑡𝑟𝑎𝑖𝑛) (2) the sensitivity analysis of the model was intended to understand changes in the probability value of one mode of public transportation to illustrate this sensitivity changes in each group's attribute value. the sensitivity graph was made based on the gradual change in one of the variables; the variable is altered gradually in value by increasing and subtracting the portion with the assumption that the other variable's value is fixed. 3. result and discussion passengers on the surabaya-jakarta route can use buses or trains and other modes of transportation. passenger transportation services from surabaya to jakarta, if taken by bus, can be started at terminal purabaya (bungurasih). the difference in departures between buses departing from the next bus (headway) is 30 minutes. meanwhile, passenger transportation services from surabaya to jakarta can be reached using the train mode, with the starting point of departure at surabaya pasar turi railway station for the northern route. meanwhile, if you want to go through the southern route, you can use gubeng railway station as the starting point of departure. 3.1. general characteristics of respondents characteristics of passenger respondents are divided into three parts, namely socio-economic characteristics, travel characteristics, and mode choice characteristics using the stated preference model experiment (table 2). the socio-economic characteristics consist of gender, age, latest education, type of work, and income in one month. the characteristics of the choice of mode using the experimental civil and environmental science journal vol. 4, no. 1, pp. 084-092, 2021 88 model stated preference consists of three parts of the probability of the respondent. this probability selects each category modelled between buses and trains. the first part is viewed in terms of travel cost attributes. the travel cost attribute is divided into two categories, the travel cost attribute in normal conditions and the travel cost attribute in pandemic conditions. the second part is in terms of travel time attributes. the third part is viewed in terms of the access time attribute. table 2. demographic characteristics of respondents characteristics percentage bus train gender male 43 50 female 57 50 age <18 years old (y.o.) 10 5 18-30 y.o. 47 50 31-43 y.o. 28 31 44-56 y.o. 13 12 >56 y.o. 2 2 last education elementary school 0 0 junior high school 7 3 senior high school 35 29 vocational study 26 26 undergraduate 27 33 postgraduate 5 9 occupation housewife 6 0 private sector 40 18 student 34 32 civil servant 20 29 income idr <1,500,000 31 24 idr 1,500,000 – 3,000,000 22 13 idr 3,000,001 – 4,500,000 25 22 idr 4,500,001 – 6,000,000 14 25 idr >6,000,000 8 16 figure 3. simple regression graph attribute cost difference travel under the pandemic conditions y = -0,00001134x 0,2848 r² = 0,9851 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 0 1 2 3 4 5 6 l o g e = p t r /p b u cbu ctr regression plot δx1 civil and environmental science journal vol. 4, no. 1, pp. 084-092, 2021 89 3.2. travel mode choice modelling the utility equation is obtained from the data input for the independent variable x1; x2; and x3 and the dependent variable y, so we get a regression equation which is the mode selection utility equation. the independent variable data, previously ordinal data (point rating), is then transformed into intervalscale data. after the regression analysis results, the modal choice utility model is obtained. the linear regression results for bus and train passengers based on the difference in travel costs attribute in pandemic conditions (δx1) (figure 3). based on linear regression results using statistical arithmetic tools, the utility model and r2 are obtained as follows. 𝑈𝐵𝑈 − 𝑈𝑇𝑅 = −0,2848 − 0,00001134(∆𝑋1) therefore, the model is obtained with the binomial model as follows: 𝑃𝑇𝑅 = 𝑒 (𝑈𝐵𝑈−𝑈𝑇𝑅) 1 + 𝑒 (𝑈𝐵𝑈−𝑈𝑇𝑅) = 𝑒(−0,2848 − 0,00001134(∆𝑋1) 1 + 𝑒 (−0,2848 − 0,00001134(∆𝑋1) for example, the difference in travel costs during a pandemic condition (δx1) = (-) idr 160,000 (bus tickets are idr 160,000 cheaper than trains), the probability of bus and train passengers is obtained as follows: 𝑃𝑇𝑅 = 𝑒 (−0,2848 − 0,00001134(−160000)) 1 + 𝑒 (−0,2848 − 0,00001134(−160000)) = 0,109 = 10,9% 𝑃𝐵𝑈 = 1 − 𝑃𝑇𝑅 = 1 − 0,109 = 0,891 = 89,1% based on the calculation above, the model is continued with another cost difference value, then the probability of choosing the mode between bus and train is obtained. the results of the probability of choosing the mode between bus and train based on the attribute difference in travel costs in pandemic conditions are presented in the table below (table 3): table 3. probability of bus and train passengers based on the difference in travel cost attributes in the new normal condition ∆x1 (idr) exp (ubu-utr) ptr pbu -160.000 0.123 0.109 0.891 -110.000 0.216 0.178 0.822 -60.000 0.381 0.276 0.724 -10.000 0.672 0.402 0.598 25.115 1.000 0.500 0.500 40.000 1.184 0.542 0.458 the regression constant is a value that affects the choice characteristics and individual characteristics that are not considered on the utility function in the mode selection. if the constant regression value is getting smaller/closer to 0 (zero), then the constant value is getting better. in this modeling obtained constant values (-0.2848) and variable values (-0.00001134 (δx1)). the constant value is (-0.2848), so if the two modes have the same travel costs, the difference in utility is (-0.2848). where in this condition, the bus probability value is 57.1%, while the train probability value is 42.9%. the probability shows a similar value when the difference of ticket fare is idr 25,115 (figure 4). civil and environmental science journal vol. 4, no. 1, pp. 084-092, 2021 90 figure 4. probability of bus and train passengers based on the difference in travel cost attributes in pandemic conditions 3.3. sensitivity analysis based on the utility value function, the fare difference between the bus mode and the train mode during a pandemic is used as an experiment when the fare difference is increased or decreased. figure 5. sensitivity analysis based on the difference in travel costs in new normal conditions based on the sensitivity analysis graph of the difference in travel costs in the pandemic conditions, the calculation of the sensitivity to the variable fare gap in pandemic conditions shows that the sensitivity line slope is positive, indicating the greater probability of choosing the bus mode (figure 5). when the travel fare difference is 0 (zero), the probability of choosing the train mode is 43%, and the bus mode is -0.5 -0.25 0 0.25 0.5 0.75 1 -160,000 -110,000 -60,000 -10,000 40,000 p ro b a b il it y change in travel fare gap (idr) modeling the difference in travel costs for pandemic conditions train probability bus probability 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 -200,000 -150,000 -100,000 -50,000 0 50,000 100,000 p ro b a b il it y o f tr a in change in travel fare gap (idr) sensitivity analysis of travel cost difference (δx1) 0,43 25.000 100.000 civil and environmental science journal vol. 4, no. 1, pp. 084-092, 2021 91 57%. meanwhile, when the likelihood of choosing the two modes is equal, 50%, the difference in tariff is idr 25,000. the probability of choosing the train mode can be increased to 70% with a fare difference of idr 100,000, meaning that the train mode must be able to reduce its fare by idr 100,000 from the bus mode fare, or by increasing the bus mode fare to idr 100,000 more expensive than the train. according to the survey, respondents chose the train mode because of the health factor. pt kai requires every passenger to wear a mask and a face shield. this requirement makes people feel safer from the danger of spreading viruses. however, this factor also makes the travel fare way more expensive. passengers need to bring the negative antigen rapid test (which costs idr 100,000 to 300,000). meanwhile, people chose the bus because of the travel fare was cheaper than the train mode. 4. conclusions travel time from surabaya to jakarta experiences a considerable decrease because of the launching of the trans-java toll road. consequently, the bus mode is now competing with the train mode. meanwhile, in the new normal situation, every aspect of life has changed, including the transportation sector. some transportation modes require the passengers to show the result of health test (generally, the negative antigen rapid test), including the train mode. this requirement might be burdensome for a particular group of people because the test will cost them idr 100,000 to 300,000. however, some people still choose to travel by train because of the health factor. from the modelling result, 89% of the passenger will choose the bus if the train's travel fare is idr 160,000 higher. the probability value will be equal when the bus fare is idr 25,000 higher than the train’s travel cost. it indicates that people choose the bus mode because of the travel cost factor. meanwhile, in this new normal condition, the train operator should reduce the ticket fare by idr 100,000 if they want a 70% probability value. further research could develop the model of short to medium travel journey in the new normal condition. factors related to mode choice are varied; therefore, exploring the most influencing factor of choosing travel mode in the new normal condition could be a promising idea. acknowledgement we express our gratitude to the pt kai daop viii and the department of transportation of east java which allowed us to access the data and do the survey. references [1] a. hergesell and a. dickinger, “environmentally friendly holiday transport mode choices among students: the role of price, time and convenience,” j. sustain. tour., 2013. [2] j. asensio, “transport mode choice by commuters to barcelona’s cbd,” urban stud., 2002. [3] p. paramita, z. zheng, m. mazharul haque, s. washington, and p. hyland, “user satisfaction with train fares: a comparative analysis in five australian cities,” plos one, 2018. [4] r. a. m. madhuwanthi, a. marasinghe, r. p. c. j. rajapakse, a. d. dharmawansa, and s. nomura, “factors influencing to travel behavior on transport mode choice,” int. j. affect. eng., 2016. [5] z. zheng, s. washington, p. hyland, k. sloan, and y. liu, “preference heterogeneity in mode choice based on a nationwide survey with a focus on urban rail,” transp. res. part a policy pract., 2016. [6] m. h. syahputra, a. t. handayani, and v. d. a. anggorowati, “analisis pemilihan moda transportasi bus antar kota dan kereta api jalur jogjasolo,” equilib, vol. 1, no. 1, pp. 103–110, 2020. [7] w. wahab and a. pruima, “studi analisis pemilihan moda transportasi umum darat di kota padang antara kereta api dan bus damri bandara internasional minangkabau,” j. tek. sipil itp, 2019. [8] w. kriswardhana and h. widyastuti, “probabilitas perpindahan moda dari bus ke kereta api dalam rencana re-aktivasi jalur kereta api jember civil and environmental science journal vol. 4, no. 1, pp. 084-092, 2021 92 panarukan,” in seminar nasional teknik sipil xi, its surabaya, 2015. [9] p. lanzini and s. a. khan, “shedding light on the psychological and behavioral determinants of travel mode choice: a meta-analysis,” transp. res. part f traffic psychol. behav., 2017. [10] d. pearce and e. özedemiroglu, “economic valuation with stated preference techniques summary guide,” … prefer. tech. …, no. march 2002, p. 89, 2002. civil and environmental science journal vol. 4, no. 1, pp. 010-021, 2021 10 analysis of sedimentation for the optimization of lempake dam operations for flood control for the city of samarinda, province of east kalimantan sandi erryanto1,2*, ussy andawayanti2, ery suhartanto2 1river basin organization of kalimantan iii, directorate general of water resources, the minister for public works and housing, samarinda, east kalimantan province, 75123, indonesian 2water resources engineering department, faculty of engineering, universitas brawijaya, malang, 65145, indonesia axlsandyrose2000@yahoo.com1 received 10-11-2020; accepted 07-12-2020 abstract. the lempake dam currently functions as a dam that provides raw water for irrigation and clean water, besides its indirect functioning as the only flood control dam in the karangmumus sub-watershed. current conditions indicate that the lempake reservoir has experienced decreased capacity from year to year. at the normal water level, the reservoir capacity of lempake reservoir in 2013 was 0.76 million m3 and in 2018 was 0.39 million m3. therefore, efforts are needed to control reservoir sedimentation and reservoir operations to allow the lempake dam to continue to function as a flood control reservoir. this study was carried out by analyzing the volume of sedimentation in the reservoir using the arcgis program and analyzing the flood hydrograph at the site by flood routing at the pasar segiri river, optimizing reservoir operations, and mapping flood inundation using the ras mapping program (hecras). the results showed that the storage volume in 2020 is predicted to be 0.241 million m3 with an annual sediment rate of 0.074 million m3. from the flood routing analysis and optimization of reservoir operations, the cross-sectional capacity of the river in pasar segiri (safe limit elevation +3.30 m) is insufficient for a flood discharge of a return period of more than 2 years (more than 222.14 m3/sec) for scenario 1, and of more than 5 years (more than 320.48 m3/sec) for scenario 2. keywords: arcgis, flood control, reservoir operations, sedimentation 1. introduction the karangmumus river that runs through the city of samarinda flows from the north up to its confluence with the mahakam river; this river is a sub-drain of the mahakam river, in accordance to 1 cite this as: erryanto, s., andawayanti, u., & suhartanto, e. (2021). analysis of sedimentation for the optimization of lempake dam operations for flood control for the city of samarinda, province of east kalimantan. civil and environmental science journal (civense), 4(1), 10-21. doi: https://doi.org/10.21776/ub.civense.2021.00401.2 civil and environmental science journal vol. 4, no. 1, pp. 010-021, 2021 11 its function as the primary sub-drain of the karangmumus river, allowing outflow discharge to flow from the spillway of the lempake dam. the lempake dam at present functions to supply raw water for irrigation and clean water, and additionally, the lempake dam indirectly functions as the sole flood control dam in the karangmumus sub-watershed. the cross-section of the karangmumus river in the back of pasar segiri is one of the most critical river cross-section points in terms of dimensional sufficiency to allow the flood discharge of the karangmumus river to flow. the most detrimental hydraulic effect is the narrowing in the back part of pasar segiri, which causes the flow to be impeded and sediment to build up downstream of the bridge [6]. the water-filled area of lempake reservoir is at present covered by almost 90% by water plants, and extremely serious sedimentation is occurring in the reservoir [6]. in several locations of the reservoir water area, reclamation has been performed by residents, and particularly on the right side of the reservoir water area, reclamation has been performed for roads. often, the karangmumus river possesses a discharge amount that exceeds the capacity of the river flow, and this occurrence recurs almost every year, which causes flooding to occur in several parts of the city of samarinda [6]. in addition to the size of the discharge flow amount from the upstream that cannot be contained by the river flow, another issue is the narrowing of the river body due to settlements constructed at the river shallows, and riverbed silting due to sedimentation [6]. to conduct analysis of the containment volume of the reservoir and of the spatial distribution of sedimentation, the geographical information system (gis) software that may be utilized for this purpose is arcgis version 10.4 from the environmental system research institute (esri) [11]. primary data from bathymetry measurements can be processed with the interpolation method in arcgis. bathymetry data is developed in the arcgis software, and this allows the reservoir volume at each increase of the water surface elevation to be found through surface volume (3d analyst) as part of arcgis. the volume of the reservoir will become the containment capacity [2]. the aim of this study among others is to find out the amount of sedimentation in lempake reservoir and its spatial distribution, to find out the flood hydrograph at the dam spillway and the river part close to pasar segiri with floods of various return periods, and to find out the technical conditions of the river cross-section close to pasar segiri during times of floods. 2. material and methods the lempake dam is located in karangmumus river, lempake sub-district, north samarinda regency, city of samarinda, east kalimantan, at the coordinate position of 0°24’29.62” south latitude and 117°11’34.48” east longitude. the overall area of the karangmumus watershed is ± 321.6 km2, while the area of lempake dam sub-watershed is ± 194.5 km2 (figure 1). 2.1. stages of conducting the study 1. collection of data and survey results at the study location (daily rainfall data, awlr discharge data, and digital mapping (land usage and soil types)). 2. conducting a quality test for rainfall data with usage of the raps (rescaled adjusted partial sums) method [3]. quality testing for rainfall data was performed by testing data consistency, data homogeneity, and inliers and outliers in the data [10]. 3. conducting analysis of the regional maximum daily rainfall with usage of the method of thiessen polygons [9]. 4. conducting analyses of frequency, goodness of fit testing, and planned rainfall. frequency analysis was performed with usage of the gumbel type i and log pearson type iii methods, after which the planned rainfall was selected based on the goodness of fit testing [8]. 5. conducting analysis of effective rainfall. analysis of effective rainfall was performed by the hourly distribution of rainfall by the psa 007 method and the rate of infiltration by the horton method [5]. civil and environmental science journal vol. 4, no. 1, pp. 010-021, 2021 12 6. conducting analysis of the flood hydrograph. analysis of the flood hydrograph was performed by considering the amount of flood discharge for various flood return periods (q1.01yr, q2yr, q5yr, q10yr, q25yr, and q50yr) with the nakayasu method [4]. 7. conducting analysis of the distribution of reservoir sedimentation with the spatial method. the spatial method utilized in this study is the kriging spatial interpolation method in arcgis with analysis of bathymetry data from 2013 and 2018, which is then interpolated to the current conditions in 2020 based on the analysis of the sedimentation rate of the reservoir [2]. 8. conducting analysis of the reservoir volume. bathymetry data was developed in the arcgis software in order to find out the reservoir volume for each increase in the water surface elevation with usage of surface volume (3d analyst) as part of arcgis [2]. the reservoir volume became the containment capacity. 9. conducting analysis of simulated dam operations. dam operations were simulated to optimize the containment capacity of the dam in reducing floods. 10. conducting flood routing analysis for the dam and the river downstream of the dam. flood routing for the dam was conducted on the primary and emergency dam spillways. the outflow that resulted from the spillways became the input for flood routing analysis along the river from lempake dam to pasar segiri with the muskingum method. flood routing downstream of the dam was conducted at pasar segiri for observations, with the remaining basin as its watershed [9]. 11. conducting mapping of flood inundation. the mapping of flood inundation was performed through ras mapping with the hec-ras software. the resulting inundation was then overlaid on aerial photography for greater clarity in understanding the resulting flood inundation map. the input from inundation mapping with hec-ras utilized hydrograph data as the results of flood hydrograph analysis for lempake dam [1]. figure 1. study location civil and environmental science journal vol. 4, no. 1, pp. 010-021, 2021 13 3. results and discussion 3.1. consistency testing of rainfall data in this study, consistency testing of the data was performed with the rescaled adjusted partial sums (raps) method. consistency testing of data was performed for rainfall data from the rain stations of temindung, lempake, pampang, sei siring, and tanah merah. the results of consistency testing for the data showed that the rainfall data are consistent. 3.2. statistical testing of rainfall data the rainfall data that had been tested for consistency cannot be fully utilized before being first examined through statistical testing. the utilized statistical tests were stationary testing (f-test and ttest) and abnormality testing with the inlier-outlier method [8]. through the conducted statistical testing, it was shown that the resulting rainfall data from the four rain stations in the upstream part of karangmumus watershed that had been corrected through consistency testing could be analyzed further (table 1). 3.3. analysis of the area of the region of influence with the method of thiessen polygons the upstream part of karangmumus watershed has an area of 320 km2 and includes four rainfall stations within it. therefore, for this study, the method of thiessen polygons was chosen to find out the area of influence [7]. the area of influence of each rain station would then be utilized to analyze the average regional rainfall. there are two outlets in the karangmumus watershed, which are the outlet of lempake dam and the river outlet at pasar segiri (figures 2 and 3). for the outlet of lempake, four rain stations were utilized, being sei siring, tanah merah, pampang, and lempake stations. meanwhile, for the outlet of pasar segiri, five rain stations were utilized, consisting of the above with the temindung rain station. figure 2. thiessen polygons for the lempake dam outlet figure 3. thiessen polygons for the pasar segiri river outlet 3.4. analysis of planned rainfall analysis of planned rainfall was conducted with usage of two statistical methods, which are the log pearson type iii and gumbel type i methods. the results of the planned rainfall that would be utilized further are the results with the lowest data skewness. from the results of analyses of frequency and goodness of fit testing with several statistical methods to obtain the above planned rainfall, it was decided that the watershed with the lempake dam outlet civil and environmental science journal vol. 4, no. 1, pp. 010-021, 2021 14 utilized the results of planned rainfall from the gumbel type i method (skewness value -0.971). meanwhile, the watershed with the pasar segiri outlet utilized the results of planned rainfall from the log pearson type iii method (skewness value -1.804). tables 2 and 3 indicate the results of planned rainfall analysis for each outlet. table 1. summary of maximum rainfall no. year max rainfall (mm) lempake dam pasar segiri 1 2019 72.88 88.00 2 2018 56.74 65.72 3 2017 60.29 46.47 4 2016 54.88 46.75 5 2015 54.40 23.70 6 2014 55.40 50.17 7 2013 85.12 51.40 8 2012 68.46 45.09 9 2011 85.42 55.60 10 2010 78.72 40.42 11 2009 79.13 54.65 12 2008 80.22 60.22 13 2007 79.16 75.43 14 2006 75.85 91.14 15 2005 72.34 107.20 16 2004 74.18 79.71 17 2003 72.63 34.31 18 2002 71.74 29.97 19 2001 83.14 49.65 20 2000 84.56 85.43 table 2. planned rainfall with the gumbel type i method for the watershed with the lempake dam outlet no tr chance planned rainfall (year) (%) (mm/day) 1 1.01 99.00 16.04 2 2 50.00 55.76 3 5 20.00 79.53 4 10 10.00 95.26 5 25 4.00 115.15 6 50 2.00 129.90 7 100 1.00 144.54 8 200 0.50 159.13 9 500 0.20 178.38 10 1000 0.10 192.93 table 3. planned rainfall with the gumbel type i method for the watershed with the pasar segiri outlet no tr (year) chance (%) planned rainfall (mm/day) 1 1.0101 99.00 20.52 2 2 50.00 56.05 3 5 20.00 76.84 4 10 10.00 89.72 5 25 4.00 105.09 6 50 2.00 115.97 7 100 1.00 126.34 8 200 0.50 136.37 9 500 0.20 152.82 10 1000 0.10 158.74 civil and environmental science journal vol. 4, no. 1, pp. 010-021, 2021 15 3.5. hydrograph of the planned flood discharge analysis of the planned discharge in this study was conducted with usage of rain distribution by hours on the length of 6 hours. the utilized rain distribution by hours was by the psa-007 method. after conducting synthetic unit hydrograph analysis by the nakayasu method, values of planned flood discharge for various return periods were obtained, which are shown in table 4 that follows. the results of analysis of the planned flood discharge showed that the planned flood discharge for each outlet had varying values, but the flood discharge value for a return period of 1000 years had almost the same value for both outlets (being 709.49 m3/sec and 705.04 m3/sec). table 4. summary of planned discharge of a watershed with two outlets flood discharge (m3/sec) return period lempake dam outlet pasar segiri outlet q 1.01 yr. 227.40 63.21 q 2 yr. 329.26 211.52 q 5 yr. 394.92 309.35 q 10 yr. 438.54 371.58 q 25 yr. 493.67 445.86 q 50 yr. 534.56 498.40 q 100 yr. 575.15 548.52 q 200 yr. 615.59 596.98 q 500 yr. 669.03 676.47 q1000 yr. 709.49 705.04 table 5. reservoir containment of lempake dam in 2013 and 2018 no. elevation 2013 2018 area (ha) volume (million m3) area (ha) volume (million m3) 1 5.00 0.00 0.00 0.11 0.00 2 5.25 0.00 0.00 0.34 0.00 3 5.50 0.00 0.00 0.57 0.00 4 5.75 0.00 0.00 2.27 0.01 5 6.00 38.88 0.00 3.96 0.01 6 6.25 47.00 0.11 13.43 0.05 7 6.50 44.12 0.23 22.89 0.08 8 6.75 67.47 0.39 30.78 0.16 9 7.00 79.83 0.57 38.67 0.23 10 7.25 115.86 0.81 159.77 0.43 11 7.50 146.49 1.14 341.42 1.18 12 7.75 261.36 1.64 343.88 1.84 13 8.00 376.23 2.44 416.42 3.01 total containment volume at normal water surface (el.7.20) 0.76 0.39 3.6. analysis of reservoir containment the amount of reservoir containment as utilized in this study was taken from the results of the analysis of bathymetry data that had been performed in the years of 2013 and 2018, and had been processed in surface volume (3d analyst) in the arcgis software (table 5). the results of analysis of reservoir containment indicated that the volume of reservoir containment at the water surface elevation in normal conditions experienced a decrease from 2013 to 2018, from a containment volume of 0.76 million m3 in 2013 to 0.39 million m3 in 2018. figure 4. 3d raster visualization of the bottom of the containing reservoir of lempake dam in 2013 figure 5. 3d raster visualization of the bottom of the containing reservoir of lempake dam in 2018 civil and environmental science journal vol. 4, no. 1, pp. 010-021, 2021 16 based on the base elevation of the containment, from the bathymetry data, interpolation was performed with usage of the geo-statistics feature found in the arcgis software, for which the results were transformed into raster form (figures 4 and 5). the results of analysis and visualization of raster data illustrated the change in the base elevation of the bottom of the containing reservoir, which in turn indicated a change in reservoir containment volume within the period from 2013 to 2018. changes in the cross-section of the reservoir that occurred within the period of the data indicated that sedimentation had occurred. then, the raster data was utilized as a reference for estimating the distribution pattern of sedimentation in order to be able to obtain the containment volume in 2020, as in the following. table 6. reservoir containment of lempake dam in 2020 no. elevation area (ha) volume (million m3) 1 5.00 0.00 0.00 2 5.25 0.00 0.00 3 5.50 0.00 0.00 4 5.75 2.94 0.01 5 6.00 5.04 0.01 6 6.25 6.39 0.02 7 6.50 6.66 0.02 8 6.75 17.75 0.06 9 7.00 24.36 0.09 10 7.25 67.73 0.28 11 7.50 341.72 1.20 12 7.75 368.50 2.24 13 8.00 376.23 3.24 total containment volume at normal water surface (el.7.20) 0.24 figure 6. 3d raster visualization of the bottom of the containing reservoir of lempake dam in 2020 the containment capacity of lempake dam in 2013 and 2018 experienced changes in that in 2013 the containment capacity was 0.762 million m3 at normal water surface elevation and in 2018 decreased to 0.390 million m3 at normal water surface elevation. the reduction in containment volume, which civil and environmental science journal vol. 4, no. 1, pp. 010-021, 2021 17 amounts to 0.372 m3, is assumed to be due to sediments that have settled over a period of five years. therefore, the containment volume in 2020 can be predicted to be 0.241 million m3 with an annual rate of sedimentation of 0.074 million m3. 3.7. flood routing flood routing was performed with two primary scenarios that utilize the function of operations during the rainy season with the water level reduced to the lowest elevation. scenario 1 = flood routing with the condition of the dam water level being full, at full supply level (fsl) (el. +7.20) scenario 2 = flood routing with the condition of the dam water level being at the minimum operation level (el. +6.00) or 1.70 m below the elevation of the edge of the spillway. flood routing for both of the two scenarios involve flood routing at the lempake dam spillway, flood routing through the river downstream of the dam, and flood routing at pasar segiri. flood routing at pasar segiri was conducted with the input discharge as the hydrograph discharge of the flood outflow from lempake dam that has been routed for the upstream part of the river, to which is added the discharge from the flood hydrograph in the remaining basin for which the watershed outlet is at pasar segiri. table 7. summary of the water level height for each flood return period at pasar segiri (scenario 1) no return period flood discharge h water surface elev. safe elev. limit for pasar segiri remarks (years) (m3/sec) (m) (m) (m) 1 q 1.01 yr. 93.15 3.0048 + 2.8313 + 3.30 safe 2 q 2 yr. 222.14 3.2795 + 3.1060 + 3.30 safe 3 q 5 yr. 320.48 3.4889 + 3.3154 + 3.30 over capacity 4 q 10 yr. 383.06 3.7197 + 3.5462 + 3.30 over capacity 5 q 25 yr. 457.81 4.0072 + 3.8337 + 3.30 over capacity 6 q 50 yr. 510.72 4.2504 + 4.0769 + 3.30 over capacity from the results of calculations above, it can be concluded that the capacity of the river cross-section at pasar segiri is not sufficient for a flood discharge that occurs with a return period of greater than 2 years if the flood occurs while the surface water level in the containing reservoir is at the peak elevation or is full. table 8. summary of the water level height for each flood return period at pasar segiri (scenario 2) no return period flood discharge h water surface elev. safe elev. limit for pasar segiri remarks (years) (m3/sec) (m) (m) (m) 1 q 1.01 yr. 93.15 2.7439 + 2.5704 + 3.30 safe 2 q 2 yr. 211.54 3.2569 + 3.0834 + 3.30 safe 3 q 5 yr. 309.51 3.4656 + 3.2921 + 3.30 safe 4 q 10 yr. 371.76 3.6764 + 3.5029 + 3.30 over capacity 5 q 25 yr. 446.05 3.9610 + 3.7875 + 3.30 over capacity 6 q 50 yr. 498.61 4.1947 + 4.0212 + 3.30 over capacity from the results of calculations above (tables 7 and 8), it can be concluded that the capacity of the river cross-section at pasar segiri is not sufficient for a flood discharge that occurs with a return period civil and environmental science journal vol. 4, no. 1, pp. 010-021, 2021 18 of greater than 5 years if the flood occurs while the surface water level in the containing reservoir is at the peak elevation or is full. table 9. summary of the comparison of the flood reduction capability of lempake dam no. return period flood reduction (%) (years) scenario 1 scenario 2 1 q 1.01 yr. 67.0% 78.4% 2 q 2 yr. 65.8% 74.6% 3 q 5 yr. 64.7% 72.2% 4 q 10 yr. 64.0% 71.2% 5 q 25 yr. 63.3% 69.9% 6 q 50 yr. 62.8% 69.2% 3.8. mapping of flood inundation mapping of flood inundation was performed through ras mapping with the hec-ras software. the resulting inundation was then overlaid on aerial photography. the input from the inundation mapping for hec-ras utilized hydrograph data from the results of flood hydrograph analysis for lempake dam with return periods of 2 and 5 years. meanwhile, the geometry input utilized in this analysis perused digital elevation model (dem) data as the results of generating data on the river crosssection in the remaining basin up to pasar segiri. figure 7. mapping of flood inundation at pasar segiri with a return period of 2 years (scenario 1) figure 8. mapping of flood inundation at pasar segiri with a return period of 2 years (scenario 2) figure 9. mapping of flood inundation at pasar segiri with a return period of 5 years (scenario 1) figure 10. mapping of flood inundation at pasar segiri with a return period of 5 years (scenario 2) civil and environmental science journal vol. 4, no. 1, pp. 010-021, 2021 19 from the results of the flood inundation mapping in the area of pasar segiri, it can be concluded that the flood with a return period of 2 years does not exceed the river capacity, in accordance with previous calculations (figures 7 and 8). in the area of pasar segiri, flood inundation occurred with a return period of 5 years. from the results of flood inundation mapping above, it can be seen that the inundation in scenario 2 is less than the inundation in scenario 1 (figures 9 and 10). figure 11. mapping of flood inundation in the remaining basin with a return period of 2 years (scenario 1) figure 12. mapping of flood inundation in the remaining basin with a return period of 2 years (scenario 2) figure 13. mapping of flood inundation in the remaining basin with a return period of 5 years (scenario 1) figure 14. mapping of flood inundation in the remaining basin with a return period of 5 years (scenario 2) civil and environmental science journal vol. 4, no. 1, pp. 010-021, 2021 20 in the area of the river in the remaining basin, flood inundation occurred starting with a return period of 2 years for scenarios 1 and 2. however, the inundation that occurred was not present in the area of settlements or public facilities (figures 11 and 12). in the mapping of flood inundation for a return period of 5 years in the remaining basin, the inundation that occurred can be seen to be present in settlements and public facilities, in both scenario 1 and scenario 2 (figures 13 and 14). 4. conclusion from the bathymetry data that was developed in surface volume (3d analyst) in arcgis, the containment capacity of lempake reservoir in 2013 and 2018 experienced changes from 0.762 million m3 to 0.390 million m3 at the elevation of normal water surface level. the reduction in containment volume is the amount of 0.372 m3, which is assumed to be by sediments that have settled over a period of five years. thusly, the containment volume in 2020 can be predicted to be 0.241 million m3. the flood discharges at pasar segiri are q1.01yr = 93.15 m 3/sec; q2yr = 222.14 m 3/sec; q5yr = 320.484 m 3/sec; q10yr = 383.06 m 3/sec; q25yr = 457.81 m 3/sec; and q50yr = 510.72 m 3/sec. the capacity of the river crosssection at pasar segiri is not sufficient for a flood discharge that occurs with return periods of greater than 2 years for scenario 1 and return periods of greater than 5 years for scenario 2. the scenario with maintenance of the water surface condition at the minimum operation level (el. +6.00) or 1.70 m below the elevation of the edge of the spillway of lempake dam is the most optimal scenario for the function of flood control in the upstream area. based on the results of analysis that had been performed, some suggestions can be made in relation to the effort to control floods or outflows, one of which is by improving the condition of land usage and maintaining the condition of the upstream part of the river to retain vegetation. another effort is to conduct efforts of coordinating reservoir operations to anticipate the floods that occur during the rainy season. there needs to be a structure to control sediments and a dam to reduce the flood discharge that enters the karangmumus river. references [1] brunner, g.w. (2016) hec-ras river analysis system. 2d modeling user’s manual. usa: us army corps of engineers. [2] childs, colin. (2004). interpolating surfaces in arcgis spatial analyst. usa: esri education services. [3] i made kamiana. (2011). teknik perhitungan debit rencana bangunan air [techniques of calculating the planned discharge of water structures]. yogyakarta: graha ilmu. [4] limantara, lily montarcih. (2010). hidrologi praktis [practical hydrology]. bandung: lubuk agung. [5] ministry of public works and public housing, directorate-general of water units, working unit for dam authority. (2017). petunjuk teknis perhitungan debit banjir pada bendungan [technical guidance of the calculation of flood discharge for dams]. jakarta: kementerian pekerjaan umum dan perumahan rakyat. [6] pt. catur bina guna persada. (2018). laporan akhir inspeksi besar bendungan lempake kota samarinda [final report of the major inspection of lempake dam, city of samarinda] (contract no. hk.02.03/satker.op.sda.k.iii/op/sda.i/243.c/xii/2017 on the date of december 22, 2017). [7] soemarto, cd. (1987). hidrologi teknik [hydrological engineering]. surabaya: usaha nasional. [8] soewarno. (1995). hidrologi aplikasi metode statistik untuk analisis data [hydrology: applications of statistical methods for data analysis]. bandung: nova. [9] sosrodarsono, suyono and takeda kensaku. (2003). hidrologi untuk pengairan [hydrology for water resources. jakarta: pt. pradnya paramita. civil and environmental science journal vol. 4, no. 1, pp. 010-021, 2021 21 [10] suhartanto, e., haribowo, r. (2011). application of kagan-rodda method for rain station density in barito basin area of south kalimantan, indonesia. journal of applied technology in environmental sanitation 1 (4). [11] wardani, y., suhartanto, e., haribowo, r. (2019). analysis of the correlation between land use changes in sub watershed wuno toward lifetime of wuno reservoir, sigi district, central sulawesi province. civil and environmental science journal 2 (1), 1-14. doi: https://doi.org/10.21776/ub.civense.2019.00101. civil and environmental science journal vol. 4, no. 1, pp. 062-075, 2021 62 analysis of runoff curve number distribution into surface runoff of lesti watershed didit priambodo1*, ery suhartanto2, sumiadi2 1perum jasa tirta i, state owned corporation, malang, east java, 65145, indonesia 2water resources engineering department, universitas brawijaya, malang, 65145, indonesia didit_priambodo@jasatirta1.net1 received 09-01-2021; accepted 04-02-2021 abstract. lesti watershed is a sub basin of brantas river located in malang regency, which is the main source of inflow and sediment loads for the sengguruh dam. human activities change the type of land cover by deforestation for the expansion of agricultural and residential areas. it makes a rapid increasing of runoff and discharges that were potentially carrying sediment into lesti river. to measure surface runoff in a watershed can be held by modeling rather than directly in the field, it is cheaper and more effective with accurate results. this study is based on soil conservation service (scs) formula to illustrate surface runoff level by knowing curve number distribution. using models based on land use changes in 2010, 2012 and 2017, generated by av swat software, shows that increasing cn value each year affects the surface runoff, so there is a relationship between land use and runoff. the average cn value in 2010 is 63.644, 2012 is 63.942, 2017 is 65.49, while the average surface runoff in 2010 is 800.28, 2012 is 823.26, 2017 is 828.009. conservation treatment on the area with a high cn value can reduce the surface runoff. it shows that watershed performance is getting better. keywords: curve number, lesti watershed, runoff. 1. introduction water flows naturally from a high to a lower area or its known as well as from upstream to downstream. in a hydrological system the water flow is divided into 4 sub-systems namely surface water, subregional groundwater, regional groundwater, and stream sub system. rainfall is the most important component of the hydrological process. rainfall depth is being transferred into stream, either through surface runoff, inter flow and sub surface flow or groundwater flow [1]. erosion at upstream of watershed is a natural occurrence due to rainfall that reaches the ground surface where not full infiltrated into the soil [15]. in a good watershed, the erosion rate is small and can be held by an existing plant. and it is balanced with the rate of soil formation. but, since land use changes are not according to conservation principles, it is immediately increasing either the erosion rate and sedimentation in river and reservoir [2]. 1 cite this as: priambodo, d., suhartanto, e., & sumiadi. (2021). analysis of runoff curve number distribution into surface runoff of lesti watershed. civil and environmental science journal (civense), 4(1), 62-75. doi: https://doi.org/10.21776/ub.civense.2021.00401.6 civil and environmental science journal vol. 4, no. 1, pp. 062-075, 2021 63 in recent years, land use in lesti watershed has already changed. there was an increase in agricultural land and residential area, while the forest was decreasing. this change has an impact on runoff and river discharge whose value are getting higher and potentially occurs the erosion and sedimentation in sengguruh reservoir [3]. according to perum jasa tirta i data, the storage capacity of sengguruh reservoir in 2011 has been reduced to 76,8 % from its initial capacity [4]. several recent studies [3, 5, 6, 7, 8] have used hydrological models that reflect the relationship between rainfall and surface runoff by considering the condition of land cover which is one of the erosion factors. soil conservation service (scs) is one of hydrological model to calculate the prediction of surface runoff and curve number (cn), which is a function of watershed characteristics such as land use, soil type, land cover, moisture, and land management methods. this research conducted to analyze the relationship of surface runoff and discharge on lesti watershed by creating the map of cn distribution value, and making an alternative model of improvement land use by conservation approach on lesti watershed. 2. materials and methods 2.1. study location this research uses the upstream lesti river basin as the area of study location. lesti sub-catchment area is located in malang regency, east java, indonesia. geographically, it is situated between 8°02'50" – 8°12'10" ls and 112°42'58" – 112°56'21" bt. the lesti watershed area is 58,294 ha, divided into sub-catchment areas, upstream lesti with 38,248 ha and downstream lesti in 20,046 ha. figure 1. location of study 2.2. data and tools the study conducted some analysis using spatial data from arc view gis 10.3 process, such as sensing of land use, soil type, and cn distribution maps. this program has an extension to analyze the model of watershed management and its impact to hydrology response unit, erosion, and sedimentation that relate with soil type, land use, and land cover periodically. it is called av swat 2000. the data structure used to run this program consists of two spatial types, vector and grid-based data. several data are used in this study, i.e.: 1. topography map in scale 1:25,000 of lesti watershed 2. river network map in scale 1:25,000 3. land use map year 2010, 2012, and 2017. 4. soil type map of lesti watershed civil and environmental science journal vol. 4, no. 1, pp. 062-075, 2021 64 5. daily rainfall data in 20 years (2000 – 2019) 6. tawangrejeni awlr discharge data in 10 years (2010 -2019) figure 2. data structure model in av swat to analyse the relationship of land use changes to runoff cn, this research uses three models simulation for 3 years of lesti watershed land use, 2010, 2012, and 2017. 2.3. research procedure the research method used is analytical research with stages as below: 1. collect the data. 2. analyse the hydrological aspects 3. digitize the map 4. running the hydrological, land use and soil type data using av swat 2000 program, to result discharge model calculation. 5. calibrate the model discharge with observation discharge from tawangrejeni station awlr. 6. analyse cn value distribution map using output of calibrated model. 7. analyse surface runoff of watershed for each model simulation. 8. create alternatives of land use improvement simulation and analyse the cn and runoff value using the same process with the earlier model. 9. analyse the comparison of each results simulation. primary and secondary data collection 2.4. watershed a watershed has special characteristics related to land use, soil type, slope and its length and topography. land use and slope are two factors that can be change by human, while the other factors are natural and uncontrol. therefore, the land use change, slope, and land cover focus on watershed management [2]. vegetation types are important in hydrological systems, and human intervention in this factor is enormous. vegetation can affect soil physical and chemical characteristics to change soil surface condition and runoff value. when rainfall intensity exceeds the infiltration capacity, water will fill the cavities on ground surface first. then, the rest of water will flow over the ground or known as surface runoff. it will run into the trench or ditch, until it enters tributaries and collects as a river [1]. volume and rate of surface runoff are depending on meteorology character of watershed. scs are develop an index called runoff curve number that expresses the impact of soil condition, hydrology or water content simultaneously. 2.5. hydrology analysis the result of hydrological analysis is rainfall intensity in several period as input data for model development. civil and environmental science journal vol. 4, no. 1, pp. 062-075, 2021 65 2.6. soil conservation service (scs) the scs method is develop from rainfall observation for years and involve many agricultural areas in us. this method is based on relationship between infiltration for every soil type with every rainfall that reaches the ground. total rainfall in every rain (p) on the ground with maximum potential of soil retains water (s), will divide into 3 components; runoff water (q), infiltration (f) and initial abstraction (ia), with formulas [9] 𝑄 = (𝑃 − 𝐼𝑎) 2 (𝑃 − 𝐼𝑎 + 𝑆) with: q = volume of surface runoff (mm) ia = initial abstraction p = daily rainfall (mm) s = volume of total retention parameter (mm) to determine depth excess rainfall or surface runoff can be showed on formula above, where correlation ia with s is [9]: 𝐼𝑎 = 0.2 𝑆 to simplify calculation of antecedent moisture condition, land use, and soil conservation, us scs determine s value as below: 𝑆 = 25.4 ( 1000 𝐶𝑁 − 10) cn: runoff curve number (0 – 100) by plotting p and q in scs curve (graphic below), it finds the cn value. in scs, soil type is classified into 4 type based on the type and land use (hydrological soil group). usually, initial abstraction use approach 0.2 s. so, the formulas : 𝑄 = (𝑃 − 0.2 𝑆)2 (𝑃 + 0.8 𝑆) surface runoff will occurred when rain (p) is bigger than initial abstraction (ia). for different cn value look this picture. figure 3. cn-scs graphics civil and environmental science journal vol. 4, no. 1, pp. 062-075, 2021 66 cn value is obtained from area study which has moderate climate. but this value can be used, when there is no value determined in area study. table 1. cn value by scs classification land-use description a b c d cultivated land1: without conservation treatment 72 81 88 91 with conservation treatment 62 71 78 81 pasture or range land: poor condition 68 79 86 89 good condition 39 61 74 80 meadow: good condition 30 58 71 78 wood or forest land: thin stand, poor cover, no mulch 45 66 77 83 good cover2 25 55 70 77 open spaces, lawn, parks, golf courses, cemeteries, etc. good condition: grass cover on 75 percent or more of the area 39 61 74 80 fair condition: grass cover on so to 75 percent of the area 49 69 79 84 commercial and business areas (85 percent impervious) 89 92 94 95 industrial districts (72 percent impervious) 81 88 91 93 residential3: average lot size average percent impervious4 1/8 acre or less 65 77 85 90 92 1/4 acre 38 61 75 83 87 1/3 acre 30 57 72 81 86 1/2 acre 25 54 70 80 85 1 acre 20 51 68 79 84 paved parking lots, roofs, driverways, etc.5 98 98 98 98 street and roads: paved with curbs and storm sewers5 98 98 98 98 gravel 76 85 89 91 dirt 72 82 87 89 the antecedent moisture conditions (amc) have strong influence on assessing surface runoff volume. therefore, scs has compiled three level of amc based on the amount of rain in 5 days earlier [12] : 1. amc i. soil in watershed is dry, lowest potential runoff, however it is not to the point of withering, have been planted with good results. amc i analysis is used to analyse cn when dry season. 2. amc ii. soil is in average condition. 3. amc iii. heavy or light rain with low temperature, soil is in saturated condition, and highest potential runoff. amc iii is used to analyse cn when wet season. curve number value is equivalent on amc i and iii conditions can be counted by using this equation [10] : civil and environmental science journal vol. 4, no. 1, pp. 062-075, 2021 67 𝐶𝑁(𝐼) = 4.2 𝐶𝑁(𝐼𝐼) 10 − 0.058 𝐶𝑁(𝐼𝐼) and, 𝐶𝑁(𝐼𝐼𝐼) = 23 𝐶𝑁(𝐼𝐼) 10 − 0.13 𝐶𝑁(𝐼𝐼) scs has developed soil classification system based on soil characteristic and that are classified into four hydrologic soil group (hsg), i.e : table 2. hydrologic soil group classification hsg soil texture hsg definitions (usda-nrcs, 1986) the six types of soil textures in study area a sand, loamy sand, or sandy loam low runoff potential and high infiltration rates; this soils have high rate of water transmission (greater than 7.62 mm/hr) (1) loamy sand (ls) (2) sandy loam (sl) b silt loam or loam moderate infiltration rates; the soils have moderate rate of eater transmission (3.81 mm/hr) (3) loam (ll) c sandy clay loam low infiltration rates; the soils have a low rate of water transmission (1.273.81 mm/hr) d clay loam, silty clay loam, sandy clay, silty clay, or clay high runoff potential; these soils have very low rate of water transmission (01.27 mm/hr) (4) clay loam (cl) (5) heavy clay (hc) (6) light clay (lc) 2.7. land use direction to conduct a good land use, several criteria are determined for protecting forest and production forest according the watershed physical characteristic, such as land slope, soil type, sensitivity to erosion and response to daily rainfall. the criteria used in determining the area based on its function refer to indonesian government regulation : pp no. 37/2012 and minister of forestry regulation : p.60/menhut-ii/2014. 3. results and discussion 3.1. digitalize the catchment area initial process on av swat program is to determine the watershed boundaries. by using topographic map and river network map, it can generate the digitized stream network with dem format. next step is to define the river and outlet location. this process needs data input for designated watershed outlet at the tawangrejeni bridge and area threshold value of 500 ha. the result of this analysis are boundary of catchment area and river network of lesti watershed. 3.2. irrigation performance index calculation • analysis of homogenous rainfall based on the analysis using raps method, with q/√n calculation < q/√n table and r/√n calculation < r/√n table, the rainfall data from tangkil, poncokusumo, and dampit station is worth to use. • analysis of abnormality based on the analysis of inlier-outlier all rainfall data is within range from xh to xl. • analysis of consistency rainfall this analysis using double mass curve methode. the result of this analysis are r2 for each station. there are 0.989, 0.984, and 0.994. so, the rainfall data are consistent. civil and environmental science journal vol. 4, no. 1, pp. 062-075, 2021 68 figure 4. the boundary of lesti catchment area with tawangrejeni station as the outlet. 3.3. analysis of land slope by calculating watershed proses on av swat program, land slope distribution is recorded on a dbf watershed table. figure 5. display of .dbf watershed table in av swat program to shows the land slope 3.4. analysis of land use map distribution of land use in the sub-catchment area presented in table 3. table 3. distribution of land use in 2010, 2012, 2017 land use 2010 2012 2017 area (ha) (%) area (ha) (%) area (ha) (%) shrubs 566.01 1.48 503.26 1.32 470.16 1.23 forest 9,129.94 23.87 8,670.69 22.67 8,438.75 22.00 06 plantation 3,199.18 8.36 1,044.12 2.73 1,014.31 2.65 residence 1,642.94 4.30 2,578.52 6.74 6,242.09 16.32 moor 17,598.49 46.01 14,044.64 36.72 12,182.62 31.85 agriculture 6,069.12 15.87 11,376.17 29.74 9,873.70 25.82 fallow 42.01 0.11 30.23 0.08 26.00 0.07 total 38,247.63 100.00 38,247.63 100.00 0 38,247.63 100.0 00 civil and environmental science journal vol. 4, no. 1, pp. 062-075, 2021 69 the tables show that there are land use changes each years. forest, shrubs, and plantation are decreasing from 25.35 % in 2010 to 23.99 % in 2012 and 23.29 % in 2017. while the agriculture area are increasing from 15.87 % in 2010 to 29.74 % in 2012, and 25.84 % in 2017. residence are also increasing from 4.3 % in 2010 to 16.32 % in 2017. distribution of land use can be shown in spatial mode by mapping it. figure 6. map of land use distribution in 2010 figure 7. map of land use distribution in 2012 figure 8. map of land use distribution in 2017 table 4. cn ii value for each land use no. land use cn ii value a b c d 1 water 49 69 79 84 2 forest 36 60 73 79 3 plantation 43 65 76 82 4 residence 49 69 79 84 5 meadow 39 61 74 80 6 agriculture 58 69 77 80 7 shrubs 35 56 70 77 8 moor 43 65 76 82 3.5. rehabilitation of physical infrastructure in surak irrigation area hru distribution is used to determine the area of land use and soil type in the watershed model. 3.6. rehabilitation of physical infrastructure in surak irrigation area this simulation aims to process all data to obtain discharge and surface runoff value in the area studies. in this research, hydrological spatial modeling’s simulation process uses scenarios land use modeling in 2010, 2012 and 2017. there are 2 types of av swat 2000 simulation results files: subbasin output file (*.sbs) and main channel output file (*.rch) 3.7. rehabilitation of physical infrastructure in surak irrigation area to obtain applicable and acceptable model in accordance with field conditions, a calibration step is required for the swat model. the calibration process is needed to adjust the influencing parameters in the study area's watershed so that the modeling results are closer to the observation discharge, in this case awlr tawangrijeni. in this study, the calibrated parameters are limited to lat_time, cn, esco, sol_awc, and alpha_bf parameters. civil and environmental science journal vol. 4, no. 1, pp. 062-075, 2021 70 table.5 av swat 2000 parameters calibrated the calibration process result is shown in the comparison graph for each modeling simulation in figure. 10, 11 and 12. calibrated model is tested statistically to compare the data population, both model discharge and awlr data. in this study, statistic testing uses regression method, nash sutcliff efficient method, and mean square error method. the results of all tests prove that the model is suitable for use. figure 9. comparation graph of model discharge to awlr discharge in 2010. figure 10. comparation graph of model discharge to awlr discharge in 2012. 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 jan feb mar apr mei jun jul ags sep okt nov des d is ch a rg e m 3 /s e c month graphic of qmodel vs qobs 2010 model observation 0.00 10.00 20.00 30.00 40.00 50.00 60.00 jan feb mar apr mei jun jul ags sep okt nov des d is ch a rg e m 3 /s e c month graphic of qmod vs qobs 2012 model observation parameter lower limit upper limit calibrated value cn2 35 98 15 % lower sol_awc 0 1 0.05 esco 0 1 0.4 – 0.5 lat_time 0 270 170 – 180 days alpha_bf 0 1 0.55 – 0.75 civil and environmental science journal vol. 4, no. 1, pp. 062-075, 2021 71 figure 11. comparation graph of model discharge to awlr discharge in 2017. 3.8. rehabilitation of physical infrastructure in surak irrigation area one of the simulation outputs with calibrated parameter values is cn values for each sub basins and hru. there are 176 sub basins in the model simulations divided by land use, soil type, and land management into each hydrology response units. each hru has its own cn value obtained from running the av swat program. by calculating each total hru area's percentage factor, it can be obtained the average cn value for both sub-basin and watershed. the average cn value for each models are 63.44 in 2010, 63.94 in 2012, 65.49 in 2017. figure.12 comparation of cn value distribution map in 2010, 2012, and 2017 models. from that spatial models (figure 12) are known, there are changes of cn values distribution that simultaneously with surface runoff rate changes. the increasing of agriculture area from 2010 to 2012 is more than 5,000 ha. furthermore increasing of residence area from 2010 to 2017 are quite significant, 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 jan feb mar apr mei jun jul agt sep okt nov des d is ch a rg e m 3 /s e c month graphic of qmod vs qobs 2017 model observation civil and environmental science journal vol. 4, no. 1, pp. 062-075, 2021 72 is more than 4,500 ha. otherwise, the area of forest and plantations continued to decline to nearly 3,000 ha in 7 years. it affects higher cn value in the following year. 3.9. rehabilitation of physical infrastructure in surak irrigation area the results of model simulation using calibrated parameter values obtained the watershed rate of surface runoff distribution value. mapping of the surface runoff distributions in each models are shown in figure. 14, 15 and 16. figure 13. map of the 2010 lesti watershed surface runoff according to the figures above, there is an increasing of surface runoff values from 2010 to 2017. the average surface runoff in 2010 is 800.28 mm/year, 2012 is 823.26 mm/year, and 2017 is 828.009 mm/year. surface runoff rates and watershed outlet river discharge also be measured as an evaluation of the cn value. table 6. comparation of hydrological value in lesti watershed parameter units 2010 2012 2017 qmin m 3/s 11.59 0.12 0.64 qmax m 3/s 61.35 50.44 60.71 runoff rate mm/year 800.28 823.26 828.01 avrg cn value 63.44 63.94 65.49 3.10. rehabilitation of physical infrastructure in surak irrigation area conservation efforts aim to improve the watershed ability to store the rainfall to reduce the surface runoff. the land improvement proposed through rearrangement the watershed existing land use (2017). the treatment priority are on sub basin or hrus which have high cn values. this study proposes two alternative conservation scenarios. first alternative is changing the land use of moor area with plantation with dense plants. the type of vegetation is also important. sengon, jabon, and fruit tree like durian, lamtoro, kemiri, avocado, and jackfruit tree are highly recommended for use. other treatment is adding 0.5 ha infiltration pond in the residence area by putting some infiltration wells in each house, making a wetland designed as a town park, and building some pond. treatment of alternative i conservation scenario as seen on figure 14. civil and environmental science journal vol. 4, no. 1, pp. 062-075, 2021 73 figure 14. location of alternative i conservation scenario. second alternative is designed by keep the existing land use. conservation effort are carried out through land treatment by changing the straight row crops into contoured fields or terraces (figure 15). the hydrologic effect of contouring results from the surface storage provided by the furrows because the storage prolongs the time during which infiltration can take place. the magnitude of storage depends not only on the dimensions of the furrows but also on the land slope, crop, planting and cultivation manner. figure 15. location of alternative ii conservation scenario both conservation model simulations are run by changing the cn value of 2017’s model, especially on the areas selected for conservation. the changes of cn value are refer to the table of scs cn classification. 3.11. rehabilitation of physical infrastructure in surak irrigation area both of conservation models are obtain similar simulation results (table 7). civil and environmental science journal vol. 4, no. 1, pp. 062-075, 2021 74 table 7. comparison of watershed hydrology parameter parameter 2010 2012 2017 conservation alt i conservation alt ii qmin (m 3/sec) 11.59 0.12 0.64 0.85 1.64 qmax (m 3/sec) 61.35 50.44 60.71 39.55 39.88 runoff rate (mm/year) 800.28 823.26 828.01 796.89 797.87 averg cn value 63.44 63.94 65.49 64.27 62.75 both of conservation models are proven can reduce cn value, runoff rate, and outlet discharge in lesti watershed. it means that the conservation models are successful and can be used to improve the watershed performance. 4. conclusion to predict the cn value of lesti watershed, av swat software analysis is used based on scs formulas. there are three model scenarios with different years of land use, 2010, 2012, and 2017. each models are calibrated with watershed outlet discharge obtained from tawangrejeni awlr data. the results of calibration is tested by nash sutcliff efficient method, and mean square error method. from all tests are proof that the model is suitable for use. average cn values for each model are 63.44 in 2010, 63.94 in 2012, and 65.49 in 2017, with a 0.264/year growth rate. spatially, the increasing of cn values mostly occurred in the southern and western part of the watershed. it happened because of land use changes such as forest reduction, expansion of agricultural area, and rise of residence area. the increasing of cn value each years affects on increase of surface runoff rate. the average surface runoff in 2010 is 800.28 mm/year, 2012 is 823.26 mm/year, and 2017 is 828.009 mm/year. it proves that changes in land cover and land management affects the watershed ability to storage the rainfall. when rainfall intensity exceeds the infiltration capacity, water will fill the cavities on a ground surface first. iit can change runoff value conservation treatment is needed to improve watershed ability to store the rainfall, reducing the surface runoff. in this study, there are two alternative scenarios. alternative one is designed by change some land use of sub basin and adding ponds of infiltration on residence area. alternative two is designed by keep the land use, and change the land cover and land management with lower cn value. the conservation simulation results are cn value is 64.27 for an alternative i and 62.75 for an alternative ii. while the rate of surface runoff for alternative i is 796.89 mm/year and for alternative ii is 797.873 mm/year. it means that the conservation models are successful and can be used to improve the watershed performance. references [1] b. triatmodjo, hidrologi teknik terapan, yogyakarta: beta offset, 2010. [2] c. asdak, hidrologi dan pengelolahan daerah aliran sungai, yogyakarta: gajah mada university press, 2002. [3] l.f. ideawati, l.m. limantara, and u. andawayanti. “analisis perubahan bilangan kurva aliran permukaan (runoff curve number) terhadap debit banjir di das lesti,” journal of water resources engineering. vol. 6, no. 1, 2015. [4] perum jasa tirta (pjt) i, “kajian kapasitas tampungan waduk sengguruh-sutamilahor dan wlingi-lodoyo”. malang: research by berau of research and development pjt i, 2015. [5] nurdiyanto, l.m. limantara, and e. suhartanto. “analisis hujan dan tata guna lahan terhadap limpasan permukaan di sub das pekalen, kabupaten probolinggo,” journal of water resources engineering, vol. 7, no. 1, pp. 83-94, 2016. civil and environmental science journal vol. 4, no. 1, pp. 062-075, 2021 75 [6] m.n. fikriy, l.m. limantara, and e. suhartanto. “cn modeling for predicting discharge in lesti sub-watershed,” intl. journal of innovative tech. and exp. eng, vol. 8, issue 12, pp 48904896, oct 2019. [7] a. prakoso, s. marsudi, and sumiadi. “analisis laju erosi dan usaha konservasi lahan di das bogel kabupaten blitar berbasis sistem informasi geografis (sig),” in water resources engineering. brawijaya university website, [online document], 2016. available: http:// pengairan.ub.ac.id/. [accessed januari 3, 2021]. [8] s. tikno, t. hariyanto, n. anwar, a. karsidi, and e. aldrian. “aplikasi metode curve number untuk mempresentasikan hubungan curah hujan dan aliran permukaan di das ciliwung hulu – jawa barat,” jurnal tek. ling, vol. 13, no.1, pp. 25 – 36, jan 2012. [9] v.t. chow, hidrolika saluran terbuka, jakarta : erlangga, 1989. [10] s.l. neitsch, j.g. arnold, j.r. kiniry, r. srinivasan, and j.r. williams, soil and water assessment tool user’s manual version 2000, grassland, soil and water research lab. usda arigicultural research service, temple, tx: texas water resources institute, 2002. [11] e. suhartanto, panduan avswat 2000 dan aplikasinya di bidang teknik sumber daya air, malang: asrori, 2008. [12] e. suhartanto, panduan hec-hms dan aplikasinya di bidang teknik sumber daya air, malang: asrori, 2008. [13] lm. limantara, hidrologi praktis, bandung: lubuk agung, 2010. [14] soewarno, hidrologi aplikasi metode statistik untuk analisa data, bandung: nova, 1995. [15] haribowo r., andawayanti u., lufira r.d. 2019. effectivity test of an eco-friendly sediment trap model as a strategy to control erosion on agricultural land. journal of water and land development. no. 42 (vii–ix) p. 76–82. doi: 10.2478/ jwld-2019-0047. http://www.pengairan.ub.ac.id/ http://www.pengairan.ub.ac.id/ open access proceedings journal of physics: conference series civil and environmental science journal vol. iii, no. 01, pp. 037-050, 2020 37 performance of multi-soil-layering (msl) urban domestic wastewater treatment system1 haribowo r.1, prayogo t.b.1, shaleha n.n.1, hafni k.n.2 1water resources department, faculty of engineering, universitas brawijaya, 65145 malang, jawa timur, indonesia 2environmental engineering department, faculty of engineering, university of north sumatra, medan, 20222, north sumatra, indonesia riyanto_haribowo@ub.ac.id received 19-01-2020; accepted 26-03-2020 abstract. this research has the objective of examining the efficiency optimization of a multisoil-layering (msl) system in three stages through the selection of the most efficient material for permeable layers. the utilized charcoal variations were coconut shell charcoal, rice husk charcoal, and corncob charcoal. the utilized incoming discharge for q1 and q2 were 0.0063 l/second and 0.0126 l/second. in the first stage of processing, the pumice and zeolite in q1 had not been able to reduce the tss below the quality standard, while silica sand in both discharges were still in accordance with the quality standard. in the second stage of processing, q1 msl a-s had the best elimination capability, with the efficiencies of tds, tss, ph, and do respectively being 18.13%, 79.68%, 2.60%, and 126.67%, while for q2, they were 29.99%, 77.76%, 1.62%, and 95.80%. in the third stage, it was shown that msl b-m was the most optimal reactor compared to all reactors that had their water qualities measured. for q1 for msl b-m, the parameters of tds, tss, ph, and do were respectively 33.16%, 84.32%, 1.29%, and 126.67%, and for q2 they were 30.80%, 80.54%, 1.50%, and 112.30%. in the third stage of processing, msl a-m, msl b-m, and msl c-m that included the addition of soil mixtures and modifications of soil mixture blocks could increase the efficiency of each parameter and had a more stable quality of water outflow compared to standard msl; this is because the incoming water flow was slower, which caused water contact with the processing media to be more optimal. keywords: multi-soil-layering, wastewater treatment, domestic wastewater 1. introduction soil as a natural filtration medium has long been used in the process of water purification, and one of the utilized methods is multi-soil-layering (msl). various research and studies have been conducted to increase the capabilities because this system is cheap in its operations and maintenance, easy to construct and operate, and can utilize local materials. the problem that is discovered in major 1 cite this as: haribowo, r., prayogo, t.b., shaleha, n.n., & hafni, k.n. (2000). performance of multi-soillayering (msl) urban domestic wastewater treatment system. civil and environmental science journal, 3(1), pp.37-50. doi: https://doi.org/10.21776/ub.civense.2020.00301.5 civil and environmental science journal vol. iii, no. 01, pp. 037-050, 2020 38 cities in the rivers as the bodies of water that pass through them, such as the ciliwung, bengawan solo, and brantas rivers as well as others, is the entry of pollutants into the river water, which is dominated by both processed and unprocessed domestic wastewater [9, 10]. this research involves performing optimization of msl system reactors to compare msl effluents with the effluents of the integrated public sanitation (mck) system that is currently installed at tlogomas using two different discharges for the parameters of ph, total suspended solids (tss), total dissolved solids (tds), and dissolved oxygen (do) [11]. the values of these parameters are compared with that for water quality based on government of the republic of indonesia regulation no. 82/2001 on the management of water quality and control of water pollution and ministry of the environment and forestry regulation no. 68 of year 2016 on the domestic wastewater quality standard [4]. both discharges are based on the current estimation of produced domestic waste output as well as the projected output of waste in the future based on the increase in population [6]. optimization of the msl system is focused on the selection of the best permeable layer to be combined with several kinds of soil mixture blocks with different kinds of charcoal, as well as to see the increase in the efficiency of the msl system when modifications of the soil mixture block shapes are applied [1, 2]. the different kinds of permeable zeolite, zeolite-resembling material, perlite, rock, and charcoal layers gave different values of efficiency in the elimination of dissolved cod, bod5, and reactive phosphorus [3]. the efficiency of elimination also depended on the operational condition of whether or not aeration was given. in a research by megah [7], permeable layers of zeolite, gravel, and gravelzeolite mixture had not been able to meet the quality standards according to ministry of the environment and forestry regulation no. 68 of year 2016 on the domestic wastewater quality standard for the parameter of total suspended solids (tss). this was also the case after the permeable layer was combined with soil block mixtures composed of variations of andosol soil mixed with coconut shell charcoal, rice straw charcoal, and sawdust with a ratio of 2:1 [8]. this was in accordance with the research by megah [7], in which it was proved that the permeable layer affected the process of water purification, particularly in the elimination of dissolved solids. guan et al. [3] stated that the quantitative evaluation of water movement in msl is not sufficient for understanding and suggested the use of retention distribution time (rtd) as the method for the characterization of mixtures and flows in an msl reactor using pulse tracer tests. the results of the research indicated that the level of re-dispersion of msl is a moderate dispersion for hlr of 200, 400, 800, and 1,600 l/(m2.d) with the rtd showing a continuous stirrer tank reactor (cstr) flow pattern as well as a negative correlation with the dead zone. the dead zone ratios of the msl were 41.0%, 52.3%, 59.6%, and 38.8% for hlr of 200, 400, 800, and 1,600 l/(m2.d). this research was in line with the study performed by latrach [5, 6] in that the manipulation of influent flow patterns with modification of the soil mixture block layer shape can increase the efficiency of msl. this research is to optimize an msl system that may be applied in the processing of domestic wastewater of the integrated public sanitation at tlogomas hamlet, malang, which is expected to be able to be implemented in the current system and will have an effect on the optimization of land use and beneficial utilization of wastewater before being drained into the river. 2. material and methods the location of the research is tlogomas hamlet in lowokwaru sub-district, city of malang. tlogomas hamlet is one of the 12 hamlets in lowokwaru sub-district in the city of malang (satria, 2013). the research site is the wastewater treatment facility (ipal) in rt.04 rw.07 in tlogomas sub-district (figure 1 and figure 2). civil and environmental science journal vol. iii, no. 01, pp. 037-050, 2020 39 figure 1. integrated public sanitation wastewater treatment facility (ipal mck), jl. tirta rona figure 2. aeration pond i, sample collection site for the ipal mck calculation of effluent average discharge the calculated average wastewater discharge is the wastewater discharge that originates from household connections (sr) and public hydrants (hu). as the inflow discharge value for the msl reactor, the resulting wastewater outflow discharge was assumed to be 80% of the clean water discharge of household connections and public hydrants, or can be taken as a wastewater generation rate (fab) of 0.8. the wastewater discharge can be calculated using the following formula: qr = fab x [(80% x household water needs (sr)x number of residents) + (20% x hydrant water needs)] 86,400 second/day ........... ( 1 ) where: qr: average wastewater discharge (l/second) wastewater generation rate: 0.8 domestic water needs for household connections: 170 l/person/day water needs for public hydrants: 30 l/person/day number of residents served: 5 people calculation of wastewater discharge: qr = (0.8 x [ (80% x 170 x 5) + (20% x 30)])/(86400) qr = 0.0063 l/second or 378 ml/minute from the above calculations, the wastewater discharge which flows into the msl reactor was found to be 0.0063 l/second. for the q2 discharge, it was assumed to be twice as large as q1, and therefore the q2 discharge has a rate of 0.0126 l/second or 576 ml/minute. the control and installation of discharge for the reactor utilized the method of valve opening, wherein the size of the primary valve opening was controlled in order to result in a discharge that is in accordance with calculations. msl reactor planning in this research, the reactor dimensions were determined based on the inflow discharge as well as the filtration speed of the rapid filter as designated in sni 6774:2008 [7], which is 6 m/hour. the following is the systematic calculation of reactor dimensions using equation 2 below: as = q vo ................... ( 2 ) as = 0.0063 l/second 6 m/hour civil and environmental science journal vol. iii, no. 01, pp. 037-050, 2020 40 as = 0.0033 m2 = 33.33 cm2 with as or the calculation area amounted to 33.33 cm2 then obtained the dimension value, as = as(design) 33.33 = length x width = 8.2 x 4.1 33.33 = 33.62 (sufficient) the planned dimensions of the reactors were 8.2 x 4.1 cm, but because of calculations of retention time, the dimensions were increased to five times larger than the planned dimensions. the height of the reactors were determined based on the total thicknesses of the gravel layer (5 cm), sand layer (25 cm), soil mixture block layer (20 cm), and the distance between the surface of the sand layer with the inlet pipe (5 cm), and the resulting reactor height was 55 cm. thus, the dimensions of the msl reactor were 41 cm x 20.5 cm x 55 cm. domestic wastewater treatment using an msl system consisted of the following three stages of processing: 1. the first stage of processing has the objective to process the wastewater using a reactor filled with rocks composed of zeolite, silica sand, and pumice with 3-5 mm diameters. the most optimal rock filler is to be used in the second and third stages of processing as a filler layer between soil mixture blocks. the dimensions of the rock filler has a length x width x height of 41 cm x 20.5 cm x 40 cm (figure 3). 2. the second stage of processing involved the use of combinations soil mixture blocks with the previously selected rock filler layer. the composition of soil mixture blocks for each reactor is made up of andosol soil, sawdust, iron powder, and charcoal variations at a ratio of 7:1:1:1. the msl-standard reactors are composed of msl a-s that utilized coconut shell charcoal, msl b-s that utilized rice husk charcoal, and msl c-s that utilized corncob charcoal. the dimensions of the soil mixture blocks were 8 cm x 20.5 cm x 5 cm in length x width x height (figure 4). 3. the third stage of processing involved processing with modification of the shape of the soil mixture in the second stage of processing. if in the previous stage the soil mixture was shaped into rectangular blocks, in this stage the blocks were modified into the shape of a letter “u”. the modified soil mixture block in the third stage of processing has the objective to optimize the flow of wastewater in the reactor and reduce reactor areas where the flow does not go through (dead zone). the utilized dimensions are the same as with previous dimensions (8 cm x 20.5 cm x 5 cm) with the addition of blocks on the left and right with dimensions of 2 cm x 20.5 cm x 3 (figure 5). figure 3. reactor installation in the first stage processing figure 4. reactor installation in second stage processing figure 5. reactor installation in the third stage processing civil and environmental science journal vol. iii, no. 01, pp. 037-050, 2020 41 parameter measurement the parameters that were measured are ph, total dissolved solids (tds), dissolved oxygen (do), and total suspended solids (tss). the utilized discharge had a value of 0.0063 l/second for q1 and 0.0126 l/second for q2. measurements were performed every 15 minutes for 2.5 hours. the resulting average outflow water quality of the reactor was compared with the integrated public sanitation outlet water quality and quality standards based on existing regulations (table 1). table 1. quality standard for domestic wastewater calculation of removal and improvement efficiency what is meant by efficiency is the comparison of increase or decrease in the initial content of waste with the content of waste after processing with the stages of multi-soil-layering (msl). this allows to see whether processing using this method is efficient in decreasing waste content that exceeds environmental quality standards. efficiency of wastewater parameter reduction is calculated with the formula below: elimination (%) =│ initial concentration−final concentration initial concentration │ x 100 % calculation of enhancement efficiency is performed with the formula below: enhancement (%) = │ final concentration−initial concentration initial concentration │x 100 % determination of the best reactor with scoring method to determine the best reactor to be used in stages i, ii, and iii, a simple scoring method was utilized. weighting was performed through the evaluation of average measurement results for each parameter in both discharges to determine scores to be given based on specific criteria: a) for each parameter, if the average measurement for each discharge meets the quality standard of ministry of the environment and forestry regulation no. 68 of year 2016 on the domestic wastewater quality standard and government of the republic of indonesia regulation no. 82/2001 on the management of water quality and control of water pollution, a score of 1 is given, and a score of 0 otherwise. b) the best processing was given a weighted score of 3, the next-best was given a weighted score of 2, and the worst was given a weighted score of 1 for each parameter for both discharges. 3. result and discussion 3.1 measurement of the existing water quality of the integrated sanitation facility at tlogomas the utilized domestic wastewater came from the waste that entered the integrated sanitation facility at tlogomas. the sampling points consisted of two points, which were aeration pond i and the integrated sanitation facility outlet. sampling taken from aeration pond i was taken as the influent waste for the entire research. to compare the quality of outflow water or effluent from the msl system, measurements needed to be taken from the integrated sanitation facility outlet in order to be able to make a comparison. measurement of water quality used the water quality checker no parameter unit maximum content 1 tss mg/l 30 2 tds mg/l 1000 3 do mg/l 3 4 ph 6.0 – 9.0 civil and environmental science journal vol. iii, no. 01, pp. 037-050, 2020 42 horiba series u-50 tool for the parameters of ph, tds, and do, and the insite ig series 3150 tool for the parameter of tss. measurements were taken at 6:00 am, 12:00 pm, and 6:00 pm, considering that domestic waste is generally discharged in the morning and the afternoon (table 2). table 2. existing water quality of the integrated sanitation facility at tlogomas no. parameter unit hour quality standard 6:00 am 12:00 pm 06:00 pm aeration pond i integrated sanitation outlet aeration pond i integrated sanitation outlet aeration pond i integrated sanitation outlet 1 ph 7.04 7.21 6.95 7.47 6.94 7.32 6,00-9.00 2 do mg/l 0 2.08 0 1.29 0 0.95 3 3 tds mg/l 711 568 691 576 656 584 1000 4 tss mg/l 67 29 72 30 77 27 30 based on ministry of the environment and forestry regulation no. 68 of year 2016 on the domestic wastewater quality standard, the water quality at the sampling points still have not met the established quality standards, still in excess of 30 mg/l for the tss parameter and less than 3 mg/l for the do parameter. however, ph and tds are in line with the established quality standards. the ph parameter is in line with ministry of the environment and forestry regulation no. 68 of year 2016 and the tds parameter is in line with government of the republic of indonesia regulation no. 82/2001. 3.2 first stage processing based on the results of measurements for 2.5 hours, 10 sets of observation data were obtained for each parameter for q1 and q2. by calculating the average value of each data set, values can be obtained that represent the resulting outflow water quality from each reactor (table 3). table 3. recapitulation of water quality measurement in stage i processing parameter discharge aeration pond i reactor integrated sanitation outlet quality standard pumice silica sand zeolite ph q1 7.18 7.44 7.47 7.56 7.32 6.009.00 q2 7.33 7.36 7.37 7.50 tds (mg/l) q1 653 578 582 526 584 1000 q2 653 610 605 540 tss (mg/l) q1 70 43.40 12.60 34.20 27.00 30 q2 70 51.60 24.80 27.10 do (mg/l) q1 0.00 4.51 3.85 4.23 0.95 3 q2 0.39 3.56 3.60 3.90 the ph parameter for each reactor composed of pumice, silica sand, and zeolite could all meet the quality standard from 6.00-9.00. when compared with the results from the integrated sanitation outlet, the capabilities of the three first-stage processing reactors in neutralizing ph are not quite good. for the tds parameter, the three first-stage processing reactors could meet the quality standard of below 1,000 mg/l, but when compared with the integrated sanitation outlet, only the reactor filled with zeolite had the best processing result. for the tss parameter, only the reactor filled with silica sand could meet the tss quality standard of below 30 mg/l, and when compared with the integrated sanitation outlet, the conclusion is that the silica sand reactor is the best in processing suspended civil and environmental science journal vol. iii, no. 01, pp. 037-050, 2020 43 solids in domestic waste. for the last parameter of do, the three reactors could meet class iii quality standard of above 3 mg/l, and when compared with the integrated sanitation outlet, the conclusion is that the three reactor fillers can result in a better concentration of do (table 3). figure 6. reactor efficiency for the first stage of processing for the ph parameter, zeolite at q2 had the highest average ph efficiency enhancement with 5.33%, followed by silica sand at q1 with 4.01% and pumice at q1 with 3.61%. enhancement of ph was not uniform for both discharges; this is in line with the results of the study by deshpande [12] who explained that the effluent reactor ph in general is not affected by the influent flow rate and the aerated or non-aerated condition of the msl system. the percentages of efficiency of each reactor for tds with an influent of 653 mg/l at q1 was 11.53% for pumice, 10.86% for silica sand, and 19.51% for zeolite. meanwhile at q2, they were 6.66%, 7.41%, and 17.32% for pumice, silica sand, and zeolite respectively. the highest efficiency was with zeolite; this is because the pore affinity of pumice and between granules of pumice is smaller than that between granules of silica. the efficiencies of tss concentration elimination at q1 were 38.00% with a pumice reactor, 82.00% with silica sand, and 51.14% with zeolite. meanwhile at q2, the efficiencies were 26.29%, 64.57%, and 61.29% for pumice, silica sand, and zeolite respectively. tss efficiency is linear in nature, where a greater discharge leads to a smaller elimination percentage. this indicates that the function of intra-granular and inter-granular pores of permeable layers play an important role. this condition is in line with the observations by deshpande [12] who found that the best tss elimination is achieved through the filtration process with permeable layers and soil mixture block layers. on average, silica sand could eliminate tss well at the q1 and q2 discharges. the three permeable layers could increase the level of dissolved oxygen in effluents above 3 mg/l at both q1 and q2 (with percentages greater than 100%) with 150.43%, 128.43%, and 141.13% at q1 and 121.30%, 123.03%, and 134.52% at q2 respectively for permeable layers of pumice, silica sand, and zeolite. with q2, the results of efficiency enhancement were in an inverse relationship with the enhancement of dissolved oxygen; this may be possible because of the further reduced contact time with the aerobic area. this is in line with yidong et al. [13] who found that oxygen is trapped in the pores of permeable layers, and at a high discharge these pores are filled with wastewater (figure 6). q1 q2 q1 q2 q1 q2 pumice silica sand zeolite % tds removal 11,53 6,66 10,86 7,41 19,51 17,32 % tss removal 38,00 26,29 82,00 64,57 51,14 61,29 % ph enchancement 3,61 0,43 4,01 0,52 5,33 2,37 % do echancement 150,43 118,53 128,43 120,03 141,13 130,03 retention time 6 4 12,5 9 8 6 6 4 12,5 9 8 6 0 2 4 6 8 10 12 14 0,00 20,00 40,00 60,00 80,00 100,00 120,00 140,00 160,00 r e te n ti o n t im e ( m in u te ) p e rc e n ta g e ( % ) efficiency of msl in stage i civil and environmental science journal vol. iii, no. 01, pp. 037-050, 2020 44 table 4. selection of the best reactor in stage i of processing parameter factor q1 q2 pumice silica sand zeolite pumice silica sand zeolite ph meets quality standard 1 1 1 1 1 1 best ranking 3 2 1 3 2 1 tds meets quality standard 1 1 1 1 1 1 best ranking 2 2 1 3 2 1 tss meets quality standard 0 1 0 0 1 1 best ranking 1 3 2 1 3 2 do meets quality standard 1 1 1 1 1 1 best ranking 3 1 2 1 2 3 total score 12 12 9 11 13 11 total score for pumice, both discharges 23 total score for silica sand, both discharges 25 total score for zeolite, both discharges 20 referring to the results of effluent water quality measurements in table 3, the best reactor was selected in this stage of processing by considering whether the reactor effluents meet the quality standard of each parameter and the best processing ranking in eliminating pollutants. from the simple weighing method, the largest score was found to be 25 for reactor 2 with silica sand (table 4). silica sand was selected to be used as the permeable layer medium in the next stage, considering that silica sand at each stage met the criteria, while zeolite was found to have failed once for the tss parameter at the q1 discharge. the media of zeolite and silica sand are commonly used media in the process of water purification and their respective advantages and disadvantages being due to porosity, formation structure, chemical composition, and ion exchange capabilities of each media. 3.3 second stage of processing based on the results of measurement for 2.5 hours, 10 sets of observation data were obtained for each parameter at q1 and q2. calculating the average values of the data gives a value that represents the resulting quality of outflow water from each reactor. table 5. summary of water quality measurement for stage ii of processing parameter discharge aeration pond i reactor integrated sanitation outlet quality standard msl a-s msl b-s msl c-s ph q1 6.99 7.17 7.07 7.12 7.32 6.00-9.00 q2 6.96 6.85 6.91 6.95 tds (mg/l) q1 651 533 547 613 584 1000 q2 675 473 515 553 tss (mg/l) q1 93 18.90 26.30 34.10 27.00 30 q2 70 18.90 23.90 28.20 do (mg/l) q1 0.00 3.80 3.73 3.68 0.95 3 q2 0.00 2.87 3.37 3.06 from the summary of observations for the second stage of processing, the ph parameter of the three reactors msl a, msl b, and msl c could meet the quality standard from 6.00-9.00. in comparing the ph parameter with the outflow water from the integrated sanitation outlet, the processing capability of the reactors in the second stage is better because the averages are close to the neutral ph of 7. for the tds parameter, the three second-stage processing reactors could meet the quality standard of tds below 1000 mg/l, and compared with the integrated sanitation outlet, all reactors had a better average as they have lower average tds values. for the tss parameter, msl a and msl b could meet the quality standard of tss below 30 mg/l, but msl c could not meet the quality standard. when compared to the integrated sanitation outlet, the conclusion is that the msl a civil and environmental science journal vol. iii, no. 01, pp. 037-050, 2020 45 and msl b reactors are better in processing suspended solids in domestic waste, but the msl c reactor could not process solids better than the integrated sanitation facility. for the last parameter of do, the three second-stage processing reactors could meet the class iii quality standard of above 3 mg/l; when compared to the integrated sanitation outlet with its value of 0.95 mg/l, the conclusion is that the three reactors can result in a better do value as they meet the class iii quality standard (table 5). figure 7. msl system efficiency for the second stage of processing the reactor with the best average efficiency for elimination of tds concentration at the discharges of q1 and q2 was msl a with a value of 24.06%, followed by msl b with 19.89% and msl c with 11.94%. the reactor with the best efficiency for the tss parameter for both discharges was msl a with 71.72%, followed by msl b with 71.80% and msl c with 65.08%. for the ph parameter, msl c had the highest ph average enhancement efficiency of 2.11% from the initial ph, followed by msl b with 1.64% and msl a with 1.40%. for the do parameter, msl b had the greatest enhancement efficiency with 119.48% from the quality standard do value, followed by msl c with 114.25% and msl a with 111.23% (figure 7). in this research, all the msl systems linearly maintained a ph value of 7. the nitrification capability to oxidize iron also differed for each reactor, and thus the release of hydroxyl groups into the bulk phase also differed [5, 6]. for the q1 discharge, there was a decrease in tss elimination efficiency on average compared to elimination by layer of silica sand only (82%) but with a high discharge (q2) there was an increase in tss elimination efficiency, and this agrees with latrach [5, 6] because tss elimination is based on the mechanism of filtration and chemical adsorption that occurs on the soil mixture blocks. for the do parameter, the overall do value decreased because the oxygen present in the pores have been used in the process of nitrification and the pores have been occupied by wastewater, and thus an aeration process is needed to increase the performance of the msl system. msl a that utilized coconut shell charcoal had the best average efficiency for each parameter, followed by msl b that utilized rice husk charcoal and msl c with its corncob charcoal. according to the literature, coconut shell and rice husk charcoal contain high amounts of silica sand, which allows filtration of suspended solids; in addition, rice husk charcoal has a good porous quality with a low capability of water absorption, and the components of rice husk charcoal have a high amount of contained oxygen, which can increase the dissolved oxygen (do) concentration. q1 q2 q1 q2 q1 q2 msl a msl b msl c % tds removal 18,13 29,99 16,04 23,73 5,79 18,09 % tss removal 79,68 77,76 71,72 71,88 63,33 66,82 % ph enchancement 2,60 1,62 2,60 0,68 2,60 0,19 % do echancement 126,67 95,80 126,67 112,30 126,67 101,83 retention time 4,90 5,00 5,40 5,70 5,00 4,50 4,90 5,00 5,40 5,70 5,00 4,50 0,00 1,00 2,00 3,00 4,00 5,00 6,00 0,00 20,00 40,00 60,00 80,00 100,00 120,00 140,00 r e te n ti o n t im e ( m in u te ) p e rc e n ta g e ( % ) efficiency of msl in stage ii civil and environmental science journal vol. iii, no. 01, pp. 037-050, 2020 46 mutia et al. [8] concluded that variations of organic material in soil mixture blocks, particularly the source of charcoal, gives a significant effect to the parameter of tss and its elimination, as well as to the elimination of other pollutants. the results of filtration with combinations of the permeable layer with soil mixture blocks msl a-s, msl b-s, and msl c-s are shown in figure 8. figure 8. color of silica sand with nitrification process indications table 6. selection of the best reactor in stage ii of processing parameter factor q1 q2 msl a msl b msl c msl a msl b msl c ph meets quality standard 1 1 1 1 1 1 best ranking 1 3 2 3 2 1 tds meets quality standard 1 1 1 1 1 1 best ranking 3 2 1 3 2 1 tss meets quality standard 1 1 0 1 1 1 best ranking 3 2 1 3 2 1 do meets quality standard 1 1 1 1 1 1 best ranking 3 2 1 1 3 2 total score 14 13 8 14 13 9 total score of msl a, both discharges 28 total score of msl b, both discharges 26 total score of msl c, both discharges 17 from the simple weighing method, the largest score was found to be 28 for msl a (table 6). the msl reactor with the same soil mixture using coconut shell charcoal became the best free variable for the processing of wastewater in the second stage of processing. coconut shell charcoal in comparison to the other types of charcoal was quite optimal in eliminating tds and tss at both discharges. the best ranking was taken from the results of quality measurements for each parameter; smaller concentrations of tds and tss means better processing. higher concentrations of do means that the oxygen content of the outflow wastewater increases, while for the ph parameter, as the outflow water reaches a neutral ph of 7, its processing quality is enhanced. 3.4 third stage of processing based on the results of measurement for 2.5 hours, 10 sets of observation data were obtained for each parameter at q1 and q2. calculating the average values of the data gives a value that represents the resulting quality of outflow water from each reactor. civil and environmental science journal vol. iii, no. 01, pp. 037-050, 2020 47 table 7. summary of water quality measurement for stage iii of processing parameter discharge aeration pond i reactor integrated sanitation outlet quality standard msl am msl b-m msl c-m ph q1 7.12 7.27 7.21 7.09 7.32 6.00-9.00 q2 7.14 6.93 7.07 7.06 tds (mg/l) q1 705 494 471 524 584 1000 q2 715 510 495 564 tss (mg/l) q1 74 15.10 11.60 17.50 27.00 30 q2 93 20.60 18.10 27.50 do (mg/l) q1 0.00 3.48 3.87 3.75 0.95 3 q2 0.00 2.81 3.25 3.01 from the summary of observations for the third stage of processing, the ph parameter of the three reactors msl a-m, msl b-m, and msl c-m could meet the quality standard from 6.00-9.00. in comparing the ph parameter with the outflow water from the integrated sanitation outlet, the capability of all the msl-m reactors is better because all three reactors approach the neutral ph of 7.00. for the tds parameter, the three third-stage processing reactors could meet the quality standard of tds below 1000 mg/l, and compared with the integrated sanitation outlet, the outflow quality of the three msl-m reactors showed lower values. the third-stage reactor that was the most efficient in processing tds was msl b-m, with the average of the two discharges being 483 mg/l. for the tss parameter, the three msl-m reactors could meet the quality standard of tss below 30 mg/l. in comparison with the integrated sanitation for the tss parameter, the conclusion is that the three reactors are good and the msl b-m reactor produces outflow wastewater with the lowest tss value for the two discharges, being 14.85 mg/l. for the last parameter of do, the three third-stage processing reactors could meet the class iii quality standard of above 3 mg/l; in comparison with the integrated sanitation with its value of 0.95 mg/l, the conclusion is that the three reactors can result in a better do value (table 7). figure 9. msl system efficiency for the third stage of processing the reactor with the best efficiency for the parameter tds at both discharges was msl b-m with a value of 31.98%, followed by msl a-m with 29.29% and msl c-m with 23.29%. the reactor with q1 q2 q1 q2 q1 q2 m-msl a m-msl b m-msl c % tds removal 29,90 28,67 33,16 30,80 25,63 21,15 % tss removal 79,59 77,85 84,32 80,54 76,35 70,43 % ph enchancement 2,05 2,94 1,29 1,50 0,41 1,18 % do echancement 116,10 93,67 128,90 108,17 124,93 100,17 retention time 4,55 5,45 5,20 6,10 4,15 5,00 4,55 5,45 5,20 6,10 4,15 5,00 0,00 1,00 2,00 3,00 4,00 5,00 6,00 7,00 0,00 20,00 40,00 60,00 80,00 100,00 120,00 140,00 t im e (( m in u te ) % civil and environmental science journal vol. iii, no. 01, pp. 037-050, 2020 48 the best efficiency for the tss parameter at both discharges was msl b-m with 82.43%, followed by msl c-m with 78.72% and msl a-m with 73.39%. for the ph parameter, msl a-m had the highest ph enhancement efficiency with 2.11% from the initial ph, followed by msl b-m with 1.59% and msl c-m with 1.40%. for the do parameter, msl b-m had the greatest enhancement efficiency with 118.53% from the do quality standard, followed by msl c-m with 112.55% and msl a-m with 104.88% (figure 9). table 8. selection of the best reactor in stage iii of processing parameter factor q1 q2 m-msl a m-msl b m-msl c m-msl a m-msl b m-msl c ph meets quality standard 1 1 1 1 1 1 best ranking 1 2 3 1 3 2 tds meets quality standard 1 1 1 1 1 1 best ranking 2 3 1 2 3 1 tss meets quality standard 1 1 1 1 1 1 best ranking 2 3 1 2 3 1 do meets quality standard 1 1 1 1 1 1 best ranking 1 3 2 1 3 2 total score 10 15 11 10 16 10 total score of m-msl a, both discharges 20 total score of m-msl b, both discharges 31 total score of m-msl c, both discharges 21 in the third stage, it became evident that there was a significant difference on msl b for which the shape of its soil mixture block was modified. msl b-m became the best reactor, with the total score of q1 and q2 discharges being 31, followed by msl c-m and msl a-m (table 8). it can be noticed that the results of the msl b-m outflow for each parameter was dominantly constant and unchanging. according to latrach et al. [5, 6], the addition of soil mixture in msl-m to form the letter u shape can slow down contact of wastewater with the soil, which can maximize each process that occurs in msl (filtration, aerobic decomposition, adsorption, nitrification, and denitrification). the following is a comparison of the processing efficiency of the msl b reactor before modification (msl b-s) and after modification (msl b-m) of the soil block shape: figure 10. efficiency comparison of msl b-s and msl b-m reactors tds tss ph do %msl b-s (q1) 16,04 71,72 2,60 126,67 %msl b-m (q1) 33,16 84,32 1,29 128,90 0,00 20,00 40,00 60,00 80,00 100,00 120,00 140,00 p e rc e n ta g e ( % ) effiiciency comparison between standard msl b and modified msl b (q1) civil and environmental science journal vol. iii, no. 01, pp. 037-050, 2020 49 by taking the example of the efficiency msl b-s and msl b-m at q1 it can be seen that the msl that had been modified has a tendency to increase in efficiency. at a discharge of 0.0063 l/second, the increase in efficiency from stage ii to stage iii for the tds parameter was 17.12%. the increase of the tss parameter was 12.6%. the ph parameter had a decrease in efficiency of 1.31% and the increase in efficiency for the parameter do was 1.93% (figure 10). by looking at the scores of the three stages of processing, it can be concluded that for all stages, the msl b-m reactor with a score of 31 can be regarded as the best reactor (table 8). conclusion the multi-soil-layering (msl) system was tested with three reactor columns and three stages of processing in this research. in the first stage of processing, zeolite and pumice could not meet the quality standard for the tss parameter, while the effluent from silica sand was able to meet the quality standard and was selected as the best rock layer for the subsequent stage of processing. in the second stage of processing, msl a-s, msl b-s, and msl c-s at both discharges could meet the quality standards for each parameter. at q1, msl a-s had the best elimination capability, with the efficiencies of tds, tss, ph, and do respectively being 18.13%, 79.68%, 2.60%, and 126.67%, while at q2 they were 29.99%, 77.76%, -1.62%, and 95.80%. in the third stage of processing that utilized a modification of soil mixture blocks, msl a-m, msl b-m, and msl c-m increased in their efficiencies in comparison to the standard unmodified msl reactor. at the third stage, each parameter at both utilized discharges indicated that msl b-m was the most optimal reactor compared to all reactors that had their water quality measure. at q1, the efficiencies of msl b-m for the tds, tss, ph, and do parameters respectively were 33.16%, 84.32%, 1.29%, and 126.67% while at q2 they were 30.80%, 80.54%, -1.50%, and 112.30%. considering the change in water quality of the outflow for each processing, the hypothesis is that msl reactors do not have a uniform effect on the ph parameter. the resulting percentages of efficiency from reactors with longer retention times has a tendency to be greater compared to reactors with shorter retention times; this is related to the length of interaction and the contact time between wastewater and the processing materials, as rocks and soil mixtures. the reactor outflow results, in comparison with the integrated sanitation outlet, show that they are better in processing domestic wastewater with a relatively quick processing time, but there needs to be periodic rinsing of the silica sand granules and the soil mixture blocks so that the pores of the materials are not clogged by suspended solids. there needs to be further research on modifications to the msl system through the measurement of other pollutant parameters as well as research using other materials in order to provide further comparisons and literature. references [1] an, c.j., mcbean, e., huang, g.h., yao, y., zhang, p., chen, x.j., li, y.p. 2016. multi-soillayering systems for wastewater treatment in small and remote communities. j. environm. inf. 27, 131–144. http://dx.doi.org/10.3808/jei.201500328. [2] an, c.j., mcbean, e., huang, g.h., yao, y., zhang, p., chen, x.j., li, y.p. 2016. multi-soillayering systems for wastewater treatment in small and remote communities. j. environm. inf. 27, 131–144. http://dx.doi.org/10.3808/jei.201500328. [3] guan, y., zhang, y., zhong, c.n., huang, x.f., fu, j., zhao, d. 2015. effect of operating factors on the contaminants removal of a soil filter: multi-soil-layering system. environ. earth sci. 74 (3), 2679–2686. http://dx.doi.org/10.1007/s12665-015-4288-8. [4] lestari, h., haribowo, r., & yuliani, e. (2019). determination of pollution load capacity using qual2kw program on the musi river palembang. civil and environmental science journal, 2(2), pp.105-116. doi:https://doi.org/10.21776/ub.civense.2019.00202.4 [5] latrach, l., ouazzani, n., et al. 2018. optimization of hydraulic efficiency and wastewater treatment performances using a new design of vertical flow multi-soil-layering (msl) technology ecological engineering. 140-152. https://doi.org/10.1016/j.ecoleng.2018.04.003 http://dx.doi.org/10.1007/s12665-015-4288-8 https://doi.org/10.21776/ub.civense.2019.00202.4 civil and environmental science journal vol. iii, no. 01, pp. 037-050, 2020 50 [6] latrach, l., masunaga, t., ouazzani, n., hejjaj, a., mahi, m., mandi, l., 2015. removal of bacterial indicators and pathogens from domestic wastewater by the multi-soil layering (msl) system. soil sci. plant nutr. 61, 337–346. http://dx.doi.org/10.1080/ 00380768.2014.974480. [7] megah, s., rosita, w., haribowo., r. 2018. efisiensi pengolahan limbah domestik menggunakan metode multi soil layering (msl). jurnal teknik pengairan universitas brawijaya, 1-13. [8] mutia, r., elystia, s., yenie, e. 2015. metode multi soil layering dalam penyisihan parameter tss limbah cair kelapa sawit dengan variasi hydraulic loading rate (hlr) dan material organik pada lapisan anaerob. jom fteknik volume 2 no. 1 februari 2015. 16. [9] riyanto h, minami y, masahiko s, tsuyoshi i, koichi y, takaya h, ariyo k 2017 behavior of toxicity in river basins dominated by residential areas contemporary engineering sciences 10 (7), 305-315. [10] r haribowo, v dermawan, sn yudha., 2018. application of artificial neural network for defining the water quality in the river. civil and environmental science journal 1 (01), 12-18, 2018. [11] yamashita h, haribowo r, sekine m, oda n, kanno a, shimono y 2012 toxicity test using medaka (oryzias latipes) early fry and concentrated sample water as an index of aquatic habitat condition environmental science and pollution research 19 (7), 2581-2594. [12] deshpande, v. v., & thorvat, a. r. (2018). experimental investigation of treatment of domestic wastewater using multi soil layering (msl) system. aquademia: water, environment and technology, 2(2), 05. https://doi.org/10.20897/awet/3963. [13] yidong guan, chen xin, zhang shuai, luo ancheng. 2012. performance of multi-soil-layering system (msl) treating leachate from rural unsanitary landfills. science of the total environment 420:183-90. doi: 10.1016/j.scitotenv.2011.12.057 https://doi.org/10.20897/awet/3963 civil and environmental science journal vol. 4, no. 1, pp. 043-061, 2021 43 analysis on the effect of groyne type impermeable placement on sediment distribution in lariang river bend wahyu prasetyo1, pitojo tri juwono2, dian sisinggih2 1water resources engineer pt. mulya sakti wijaya, makassar, 90133 indonesia 2water resources engineering departement, brawijaya universitas, malang, 65145 indonesia gundol_88@yahoo.com1 received 01-12-2020; accepted 18-01-2021 abstract. sedimentation and erosion caused by differences in discharge is a problem that often occurs at river bends. one of the functions of placing the groyne is to reduce the river flow velocity along the riverbank, accelerate sedimentation, and ensure the embankment or river bank's safety against scouring. this study aimed to determine the distribution of current velocity, distribution of riverbed shear stress, and sediment distribution to the effect of groyne placement. there are 7 (seven) simulation models used to get the most effective groyne placement. from the model simulation results by adding a groyne building on the river's outer bend for the simulation model scenario 2 to scenario 7, the largest sedimentation production is in scenario 3, namely the height of riverbed sediment deposits 230 hours of 1.094 m. furthermore, the groyne building's effective placement is determined based on a maximum change in the riverbed scenario. in scenario 3, the placement and dimensions of the groyne length of 17.5 m; distance between groyne 24.4 m; the groyne is inclined upstream in the direction of flow 10°. keywords: erosion, groyne, river bends, sedimentation 1. introduction the river is the accumulation of water flowing to a lower place. water that is on the plain's surface, whether it comes from rainwater, springs, or glacial fluids, will flow through a channel to a lower place. at first, the channel through which it was passed was narrow and short. naturally, this water flow erodes the areas in which it passes. as a result, this channel was getting more comprehensive and more extended, and there was what was called a river. as a result of this water flow, it will cause impacts in erosion, transportation, and sedimentation. these three activities depend on the watershed slope, river water volume, and water flow velocity [12]. the greater the slope of the river flow, the greater the erosion and transportation activities. otherwise, the accumulation will be more intensive in bare areas, where the flow slowly so that water has the opportunity to settle the material it carries. this change occurs naturally due to the many treatments that 1 cite this as: prasetyo, w., juwono, p. t., & sisinggih, d. (2021). analysis on the effect of groyne type impermeable placement to sediment distribution in lariang river bend. civil and environmental science journal (civense), 4(1), 43-65. doi: https://doi.org/10.21776/ub.civense.2021.00401.5 civil and environmental science journal vol. 4, no. 1, pp. 043-061, 2021 44 exist along the river, such as dams, reservoirs, bridges, and inevitable natural conditions such as bends in rivers [3]. bends in rivers are a particular phenomenon to study because scouring and deposition often occur at river bends. in severe situations, large volumes of landslides can occur on river banks, which can cause damage to existing infrastructure. the cliff slide process occurs due to the continuous scouring process at the bottom of the channel. the scouring pattern that happens is very much influenced by discharge, riverbed slope, and time. the longer the water runoff occurs, and the greater the flow rate, the deeper and more prolonged the scouring occurs [8, 9, 13]. in rivers where the current velocity is high, it causes erosion, both on the bank and the riverbed. therefore a protective building is needed. cliff protection buildings can be in the form of lining, walls, sheet piles, gabions, groyne, and others. the groyne is one of the protective structures installed across the riverbank, aiming to slow down the flow's speed around the groyne. the erosion process will be avoided and even sedimentation will occur. thus, on the cliffs, where the erosion process was initially occurring, it becomes protected and even sedimentation occurs due to the groyne's presence [11]. several studies related to the groyne structure have been carried out [11] and state that one of the most effective scours countermeasures is using a groyne structure to protect the river bank from highspeed currents [6]. the purpose of this study was to determine the velocity distribution with the groyne building on the river bend; to determine the primary shear stress and the distribution of sedimentation in the presence of a groyne building on a river bend; analyzing the effect of the effective placement of the groyne to minimize erosion at river bends. 2. material and methods a. material administratively, the lariang river is included in the lariang watershed. it is located in 3 (three) provinces, namely central sulawesi, west sulawesi and south sulawesi provinces, which consists of 5 (five) districts, namely north mamuju regency, donggala regency, sigi regency, poso regency, and north luwu regency. the lariang watershed is located between 1° 11 '15 "2° 22" 48 " south latitude and 119° 17" 15 "120° 30" 7 " east longitude. the research location is located at 1° 26 '33 " south latitude and 119° 21" 36 " east longitude. figure 1. research site civil and environmental science journal vol. 4, no. 1, pp. 043-061, 2021 45 the lariang watershed, covering 7264.97 km2, is one part of the palu lariang river basin, consisting of 52 watersheds. the lariang river has an upstream in poso regency, central sulawesi province and north luwu regency, south sulawesi province, and empties into the makassar strait. the downstream area of the lariang watershed, which is administratively included in the north mamuju regency, is the area that has been the worst affected by the destructive force of the lariang river. the main problems in the downstream area of the lariang watershed are the scouring of cliffs river at the river's outer bend and inundation due to the lariang river's flooding. the data used in the study are as follows: 1. river geometry data measured in 2017. 2. designed flood discharge data calculated from the sulawesi river basin iii in 2017. 3. data for sediment gradient analysis baseline (bedload) from the sulawesi iii river basin in 2017. 4. data elevation of former flood historical water levels measured in 2014. b. methods the method used in the assessment of this study is a 2-dimensional numerical model simulation using the resources management associates-2 (rma2) and sed2d models as follows: • rma2 model rma2 model is a two-dimensional finite element numerical model used to solve hydrodynamic problems at location water, assuming an average depth. rma2 works in range the sub-flow critical. rma2 calculates water level elevation and horizontal flow velocity at each node in the model domain. the reynolds form in the equation navier-stokes used to calculate the turbulent flow. friction is calculated using the manning equation and the eddy viscosity coefficient is used to define turbulent characteristics. rma2 solves both lasting and dynamic problems. the numerical model rma2 solves the equation for the conservation of mass and momentum of water integrated into the mean depth (depth-averaged) in two horizontal dimensions. the vertical directional acceleration is negligible, so the velocity vector is excellent and the direction is the same along the water column. the average depth flow velocity u used by rma2 is stated in the following equation [4]: 𝑈 = 1 ℎ ∫ 𝑢(𝑧)𝑑𝑧 ℎ 0 with : u = flow velocity mean depth (in x direction) h = elemental water depth u(z) = flow velocity as a function of vertical direction z = vertical coordinates the form of the equation for rma2 that has been solved is [4]: ℎ 𝜕𝑢 𝜕𝑡 + ℎ𝑢 𝜕𝑢 𝜕𝑥 + ℎ𝑣 𝜕𝑢 𝜕𝑦 − ℎ 𝜌 [𝐸𝑥𝑥 𝜕2𝑢 𝜕𝑥2 + 𝐸𝑥𝑦 𝜕2𝑢 𝜕𝑦2 ] + 𝑔ℎ [ 𝜕𝑎 𝜕𝑥 + 𝜕ℎ 𝜕𝑥 ] + 𝑔𝑢𝑛2 (1,486ℎ 1 6) 2 (𝑢 2 + 𝑣 2) 1 2 − ζ𝑉𝑎 2𝑐𝑜𝑠ψ − 2hv⍵sinφ = 0 (1) ℎ 𝜕𝑣 𝜕𝑡 + ℎ𝑢 𝜕𝑣 𝜕𝑥 + ℎ𝑣 𝜕𝑣 𝜕𝑦 − ℎ 𝜌 [𝐸𝑦𝑥 𝜕2𝑣 𝜕𝑥2 + 𝐸𝑦𝑦 𝜕2𝑣 𝜕𝑦2 ] + 𝑔ℎ [ 𝜕𝑎 𝜕𝑦 + 𝜕ℎ 𝜕𝑦 ] + 𝑔𝑣𝑛2 (1,486ℎ 1 6) 2 (𝑢 2 + 𝑣 2) 1 2 − ζ𝑉𝑎 2𝑐𝑜𝑠ψ − 2hu⍵sinφ = 0 (2) 𝜕ℎ 𝜕𝑡 + ℎ ( 𝜕𝑢 𝜕𝑥 + 𝜕𝑣 𝜕𝑦 ) + 𝑢 𝜕ℎ 𝜕𝑥 + 𝑣 𝜕ℎ 𝜕𝑦 = 0 (3) civil and environmental science journal vol. 4, no. 1, pp. 043-061, 2021 46 where : h = water depth u, v = velocity x and y x,y,t = cartesian coordinates and time ρ = density of liquid e = eddy viscosity coefficient for xx = normal direction on x axis surface for yy = normal direction on y axis surface for xy and yx = shear direction on each surface g = acceleration due to gravity a = elevation of bottom n = manning’s roughness n-value 1.486 = conversion from si (metric) to non-si units ζ = empirical wind shear coefficient va = wind speed ψ = wind direction ⍵ = rate of earth’s angular rotation φ = local latitude • sed2d model sed2d software analyzes two sediments: non-cohesive sediments (sand) and cohesive sediments (clay). this numerical model only examines one sufficient grain size of each run, which requires a separate run model for each sufficient grain size. the concentration of sediment suspended calculated by using equation convection-diffusion equipped with a bed source term [7]: 𝜕𝐶 𝜕𝑡 + 𝑢 𝜕𝐶 𝜕𝑥 + 𝑣 𝜕𝐶 𝜕𝑦 = 𝜕 𝜕𝑥 (𝐷𝑥 𝜕𝐶 𝜕𝑥 ) + 𝜕 𝜕𝑦 ( 𝜕𝐶 𝜕𝑦 ) + 𝛼1𝐶 + 𝛼2 (4) where: c = concentration, kg/m3 t = time, sec u = flow velocity in x direction, m/sec x = primary flow direction, m v = flow velocity in y direction, m/sec y = direction perpendicular to x , m dx = effective diffusion coefficient in x direction, m 2/sec dy = effective diffusion coefficient in y direction, m 2/sec α1 = a coefficient for the source term, 1/sec α2 = the equilibrium concentration portion of the source term, kg/m 3/sec = α1ceq ackers and white's formulation is used to calculate the transport potential (ceq) sedimentary material about sand's size [1, 5]. meanwhile, the characteristic timing (tc) is somewhat subjective. because tc is the time required for the concentration in the flow field to change from c to ceq. in the case of deposition, the characteristic time is associated with falling velocity, and the following equation is used [7]: 𝑡𝑐 = 𝐶𝑑 𝐻 𝑉𝑠 or tc = dt (5) where: tc = characteristic time cd = coefficient for deposition d = flow depth vs = fall velocity of a sediment particle civil and environmental science journal vol. 4, no. 1, pp. 043-061, 2021 47 dt = computation time interval meanwhile, to calculate the river bed shear stress using the formula [7]: τb = ρ (u *)2 (6) where: ρ = water density u* = shear velocity for u*, use the bijker equation to calculate the total shear stress due to waves and currents. the equation is as follows [7]: 𝑢∗ = √ 1 2 𝑓𝑐 ū 2 + 1 4 𝑓𝑤 𝑢𝑜𝑚 2 (7) bed source quantity [2]: s = α1 c+α2 (8) the quantity of bed source is divided into two formulations, namely: a. for sand the bed source term's shape is s = α1c + α2, used for analysis deposition and erosion at the bottom. the method of calculating the alpha coefficient depends on the type of material. sediment transport at the bottom is controlled by the potential for flow transport and the availability of material at the base, so that the form of the equation bed source term becomes [7]: 𝑆 = 𝐶𝑒𝑞−𝐶 𝑡𝑐 (9) with : s = source term ceq = equilibrium concentration (transport potential) c = sediment concentration in the water column tc = characteristic time for effecting the transition for time characteristics using the case, it is deposition formulated as follows [7]: tc = greater form 𝐶𝑑 𝐷 𝑉𝑠 or dt with : tc = characteristic time cd = coefficient for deposition d = flow depth vs = fall velocity of a sediment particle dt = computation time interval b. for clay [7] 𝑆 = − 𝑉𝑠 𝐷 𝐶 (1 − 𝜏 𝜏𝑑 ) for c < 𝐶𝑐, 𝜏 < 𝜏𝑑 (10) 𝑆 = − 𝑉𝑘 𝐷 𝐶 7 3⁄ (1 − 𝜏 𝜏𝑑 ) for c > 𝐶𝑐 , 𝜏 > 𝜏𝑑 (11) with: τ = bed shear stress τd = critical shear stress for deposition cc = critical concentration = 300 mg/l civil and environmental science journal vol. 4, no. 1, pp. 043-061, 2021 48 • groyne formation a. normal groyne (perpendicular) the normal groyne is built to narrow the part of the river. the river has become too wide and on the convex side of the river bend. b. upstream inclined groyne on permeable inclined upstream, scouring will occur at the groyne's front end while sedimentation generally occurs near river cliffs and the flow will lead to the middle of the river. this groove is very useful for protecting the river cliffs. c. downstream inclined groyne on permeable groyne that leans downstream, scour at the front end of the groyne tends to decrease and hence deposition may occur downstream of the groyne. table 1. flow direction and axis angle groyne [10] location of groyne in river flow direction and axis angle groyne perpendicular 10° 15° outside 5° 15° inside bend 0° 10° in this simulation, the data required as the model input is secondary data obtained from bws sulawesi iii and primary data taken directly at the study location. these data are simulated into a model to determine velocity, shear stress and sediment distribution using 7 (seven) scenarios for placing groyne. the stages of the method used in this study are as follows: 1. input river geometry data is in the form of data contour and cross-section with 7 (seven) scenarios for placing the groyne. 2. input the boundary condition in the form of discharge data per unit time for the rma2 simulation. 3. simulation of the rma2 model aims to determine the water level and velocity of the flow direction, which will be used as model validation through the test mre (mean relative error) [5] the following calculations: 𝑀𝑅𝐸 = ℎ𝑐−ℎ0 h0 𝑋 100% (12) where : hc = water level elevation model ho = history flood elevation 4. calibration, to make the model to be used close to the actual condition. 5. simulation of the sed2d model, this model's input is in sediment grains gradation data and data suspended load. table 2. input value of sed2d model no parameter unit value 1 diffusion coeffisient m2/sec 100 2 initial concentration kg/m3 0.20 3 settling velocity m/sec 0.9 4 specific gravity kg/m3 2773 5 grain shape factor 0.67 6 characteristic deposition length factor ‘m 1.00 7 thickness ‘m 1.00 8 sand grain roughness 1.00 9 sand grain size mm 9.5 civil and environmental science journal vol. 4, no. 1, pp. 043-061, 2021 49 6. comparative analysis of simulation results aims to determine the more effective crib placement in reducing river bank scour 3. result and discussion a. mre test/calibration before proceeding to the modelling stage, it is necessary to validate the model against the initial simulation to ensure that the model can represent field conditions. validation is carried out on the modelling results to determine the model's suitability to the actual field conditions. in this case, it is done by comparing the modelling results' water level with the flood events' historical water level elevation data. based on the mre test, the model's accuracy level will be known to the field's actual conditions. the test results that are close to the relative error value, which is assumed to be ≤ 10%, show that the results are appropriate, so there is no need to calibrate the model (table 3). the test results show that the mre of the rma2 model was calibrated using a manning number of 0.03 and a turbulent exchange coefficient (eddy viscosity) of 500 m2/sec. the model results approach the actual conditions. tabel 3. result of mre test return flood discharge (years) water level (m) result of mre test (%) result model test flood history 1.25 18.23 17.82 2.30 20.00 18.81 19.33 2.69 b. scenario modelling 1 • model simulation rma2 rma2 model simulation scenario 1 is carried out when the river is in a condition with no groyne. the rma2 model simulation is conducted to obtain the distribution of river flow velocity at the research location (figure 2). figure 2 shows that the arrows are the direction of the flow and the colour gradations are dominated by green and blue. the green colour represents the current velocity value of 1.9 m/sec and the blue colour represents the current velocity value of 2.5 m/sec. so that in existing conditions, the distribution of flow velocity at the research location ranges from 1.1 m/sec – 2.5 m/sec, evenly distributed on the left, centre and right of the river. figure 2. rma simulation results (q20) scenario 1 figure 3. sed2d simulation results (q20) scenario 1 civil and environmental science journal vol. 4, no. 1, pp. 043-061, 2021 50 • model simulation sed2d this model aims to determine the shear stress and distribution of riverbed sediments with river conditions without buildings by looking at the effect of the discharge of q20 (figure 3). figure 3 shows that the colour gradation is dominated by blue. there are also yellow and green colours. the yellow colour means that there has been a change in the riverbed of -0.20 m, the green colour means that there is no change in the river bed, and the blue colour means that there has been a change in the riverbed of 0.20 m. the condition of the existing river is a change in the river bed due to the q20 flood discharge of 0.07 m to 0.20 m, spread evenly on the left, centre and right of the river. figure 4. distribution of shear stress (ʈ) riverbed scenario 1 (q20) figure 4 shows the distribution of riverbed shear stresses the effect of flood discharge 20 (q 20) on the river's cross section. figure 4 shows that the distribution of riverbed shear stress is evenly distributed on the left, centre and right of the river. c. scenario modelling 2 • model simulation rma2 the 2-step scenario modelling is the same as the modelling scenario 1 (existing), but in this scenario two, we will place 32 groynes on the outer bend of the river, with the dimensions of the groyne: length of 17.5m; groyne perpendicular to flow; distance between groyne 24.4m. figure 5 shows that the arrows are the direction of the flow and the colour gradations consisting of red, yellow, green, and blue. the red colour represents the current velocity value of 0.0 m/sec. the yellow colour represents the current velocity value of 0.98 m/sec. the green colour represents the current velocity value of 1.97 m/sec, and the blue colour represents the current velocity value of 2.95 m/sec. civil and environmental science journal vol. 4, no. 1, pp. 043-061, 2021 51 the red colour dominates the river's outer side (right bank), yellow to blue colours dominate the inside of the river (left bank) and the river's middle. placing the groyne building on the river's outer side (right bank) can reduce the river flow velocity. the low flow velocity allows sedimentation to occur on the river's outer side (right bank). the process of placing the groove as a river flow direction building can function following what was planned. figure 5. rma simulation results (q20) scenario 2 figure 6. sed2d simulation results (q20) scenario 2 figure 7. distribution of shear stress (ʈ) riverbed scenario 2 (q20) civil and environmental science journal vol. 4, no. 1, pp. 043-061, 2021 52 • model simulation sed2d the sed2d model simulation aims to determine the distribution of sediment and river bed shear stress by adding 32 groyne. the groyne's dimensions: length 17.5m; groyne perpendicular to flow; distance between groyne 24.4 m; due to the influence of q20. from figure 6, it can be seen that blue colours dominate the colour gradation. the blue colour means that there has been a change in the riverbed of 0.25 m. in scenario 2, there is a change in the river bed due to the q20 flood discharge of 0.03 m to 0.25 m, spread evenly on the left, centre and right of the river. the minimum river bed shear stress occurs on the river's right bank (outer river bend) and the maximum river bed shear stress occurs on the left bank of the river (inner river bend) (figure 7). low riverbed shear stress values allow sedimentation, while high riverbed shear stress values allow erosion. in this condition, there is a sedimentation process on the river's right bank (outer river bend) and an erosion process occurs on the left bank of the river (bend in the river). d. scenario modelling 3 • model simulation rma2 the 3-step scenario modelling the same as the modelling in scenario 2, it only changes the curb's direction towards the upstream direction of the flow by 10° (figure 8). figure 8 shows that the arrows are the direction of the flow and the colour gradations consisting of red, yellow, green, and blue. the red colour represents the current velocity value of 0.0 m/sec. the yellow colour represents the current velocity value of 1.00 m/sec. the green colour represents the current velocity value of 2.00 m/sec, and the blue colour represents the current velocity value of 3.00 m/sec. the red colour dominates the river's outer side (right bank), yellow to blue colours dominate the inside of the river (left bank) and the river's middle. placing the groyne building on the river's outer side (right bank) can reduce the river flow velocity to a low. the low flow velocity allows sedimentation to occur on the river's outer side (right bank). the process of placing the groove as a river flow direction building can function following what was planned. • model simulation sed2d the sed2d model simulation aims to determine the distribution of sediment and river bed shear stress by adding 32 groyne, with the groyne's dimensions: length of 17.5m; groyne inclined 10° to upstream; distance between groyne 24.4 m; due to the influence of q20. figure 8. rma simulation results (q20) scenario 3 figure 9. sed2d simulation results (q20) scenario 3 figure 9 show that the green and blue colours dominate the colour gradation. there is a change in the river bed in scenario three due to the q20 flood discharge of 0.13 m to 0.27 m, which is spread evenly on the left, centre and right of the river. civil and environmental science journal vol. 4, no. 1, pp. 043-061, 2021 53 figure 10. distribution of shear stress (ʈ) riverbed scenario 3 (q20) figure 10 shows that the minimum river bed shear stress occurs on the river's right bank (outer river bend) and the maximum river bed shear stress occurs on the left bank of the river (inner river bend). low riverbed shear stress values allow sedimentation. however, high riverbed shear stress values allow erosion. in this condition, there is a sedimentation process on the river's right bank (outer river bend) and an erosion process occurs on the left bank of the river (bend in the river). e. scenario modelling 4 • model simulation rma2 the 4-step scenario modelling the same as the modelling in scenario 2, it only changes the direction of the curb inclined towards the downstream direction of the flow by 10° (figure 11). figure 11. rma simulation results (q20) scenario 4 figure 12. sed2d simulation results (q20) scenario 4 civil and environmental science journal vol. 4, no. 1, pp. 043-061, 2021 54 figure 11 shows that the arrows are the direction of the flow and the colour gradations consisting of red, yellow, green, and blue. the red colour represents the current velocity value of 0.0 m/sec. the yellow colour represents the current velocity value of 1.03 m/sec. the green colour represents the current velocity value of 2.07 m/sec, and the blue colour represents the current velocity value of 3.10 m/sec. the red colour dominates the river's outer side (right bank), yellow to blue colours dominate the inside of the river (left bank) and the river's middle. placing the groyne building on the river's outer side (right bank) can reduce the river flow velocity to a low. the low flow velocity allows sedimentation to occur on the river's outer side (right bank). the process of placing the groove as a river flow direction building can function following what was planned. • model simulation sed2d the sed2d model simulation aims to determine the distribution of sediment and river bed shear stress by adding 32 groynes. the groyne's dimensions: length of 17.5m; groyne inclined 10° to the downstream; distance between groyne 24.4 m; due to the influence of q20. from figure 12, it can be seen that green and blue colours dominate the colour gradation. in scenario four, there is a change in the river bed due to the q20 flood discharge of 0.08 m to 0.22 m, spread evenly on the left, centre and right of the river. figure 13 shows that the minimum river bed shear stress occurs on the river's right bank (outer river bend) and the maximum river bed shear stress occurs on the left bank of the river (inner river bend). low riverbed shear stress values allow sedimentation. however, high riverbed shear stress values allow erosion. in this condition, there is a sedimentation process on the river's right bank (outer river bend), and an erosion process occurs on the left bank of the river (bend in the river). figure 13. distribution of shear stress (ʈ) riverbed scenario 4 (q20) civil and environmental science journal vol. 4, no. 1, pp. 043-061, 2021 55 figure 14. rma simulation results (q20) scenario 5 figure 15. sed2d simulation results (q20) scenario 5 f. scenario modelling 5 • model simulation rma2 the 5-step scenario modelling is the same as the modelling scenario 1 (existing), however, in this scenario five, 26 groynes placed on the outer bend of the river, with the dimensions of the groyne: length of 17.5m; groyne perpendicular to flow; distance between groyne 35.5m. figure 14 shows that the arrows are the direction of the flow and the colour gradations consisting of red, yellow, green, and blue. the red colour represents the current velocity value of 0.0 m/sec. the yellow colour represents the current velocity value of 1.02 m/sec. the green colour represents the current velocity value of 2.05 m/sec, and the blue colour represents the current velocity value of 3.07 m/sec. the red colour dominates the river's outer side (right bank), yellow to blue colours dominate the inside of the river (left bank) and the river's middle. placing the groyne building on the outer side of the river (right bank) can reduce the river flow velocity to a low. furthermore, the low flow velocity allows sedimentation to occur on the outer side of the river (right bank), so that the process of placing the groove as a river flow direction building can function following that was planned. • model simulation sed2d the sed2d model simulation aims to determine the distribution of sediment and river bed shear stress by adding 26 groyne, with the groyne's dimensions: length of 17.5m; groyne perpendicular to flow; distance between groyne 35.5 m; due to the influence of q20. from figure 15, it can be seen that blue colours dominate the colour gradation. in the condition of scenario 5, it is seen that there is a change in the river bed due to the q20 flood discharge of 0.06 m to 0.16 m, which is spread evenly on the left, centre and right of the river. figure 16 shows that the minimum river bed shear stress occurs on the river's right bank (outer river bend) and the maximum river bed shear stress occurs on the left bank of the river (inner river bend). low riverbed shear stress values allow sedimentation, while high riverbed shear stress values allow erosion, so that in this condition there is a sedimentation process on the right bank of the river (outer river bend) and an erosion process occurs on the left bank of the river (bend in the river). g. scenario modelling 6 • model simulation rma2 the 6-step scenario modelling the same as the modelling in scenario 5, it only changes the direction of the curb inclined towards the upstream direction of the flow by 10° (figure 17). civil and environmental science journal vol. 4, no. 1, pp. 043-061, 2021 56 figure 16. distribution of shear stress (ʈ) riverbed scenario 5 (q20) figure 17. rma simulation results (q20) scenario 6 figure 17 shows that the arrows are the direction of the flow and the colour gradations consisting of red, yellow, green, and blue. the red colour represents the current velocity value of 0.0 m/sec. the yellow colour represents the current velocity value of 1.00 m/sec. the green colour represents the current velocity value of 2.00 m/sec, and the blue colour represents the current velocity value of 3.00 m/sec. the red colour dominates the river's outer side (right bank), yellow to blue colours dominate the inside of the river (left bank) and the middle of the river. placing the groyne building on the outer side of the river (right bank) can reduce the river flow velocity to a low. furthermore, where the low flow velocity allows sedimentation to occur on the outer civil and environmental science journal vol. 4, no. 1, pp. 043-061, 2021 57 side of the river (right bank) so that the process of placing the groove as a river flow direction building can function by that was planned. • model simulation sed2d the sed2d model simulation aims to determine the distribution of sediment and river bed shear stress by adding 26 groyne, with the dimensions of the groyne: length of 17.5m; groyne inclined 10° to upstream; distance between groyne 35.5 m; due to the influence of q20. figure 18. sed2d simulation results (q20) scenario 6 from figure 18, it can be seen that green and blue colours dominate the colour gradation. in the condition of scenario 6, it is seen that there is a change in the river bed due to the q20 flood discharge of 0.06 m to 0.22 m, which is spread evenly on the left, centre and right of the river. figure 19. distribution of shear stress (ʈ) riverbed scenario 6 (q20) civil and environmental science journal vol. 4, no. 1, pp. 043-061, 2021 58 figure 19 shows that the minimum river bed shear stress occurs on the river's right bank (outer river bend), and the maximum river bed shear stress occurs on the left bank of the river (inner river bend). low riverbed shear stress values allow sedimentation, while high riverbed shear stress values allow erosion. in this condition there is a sedimentation process on the right bank of the river (outer river bend) and an erosion process occurs on the left bank of the river (bend in the river). h. scenario modelling 7 • model simulation rma2 the 7-step scenario modelling the same as the modelling in scenario 5, it only changes the direction of the curb inclined towards the downstream direction of the flow by 10° (figure 20). from figure 20, it can be seen that the arrows are the direction of the flow and the colour gradations consisting of red, yellow, green, and blue. the red colour represents the current velocity value of 0.0 m/sec, the yellow colour represents the current velocity value 1.02 m/sec, the green colour represents the current velocity value 2.04 m/sec, and the blue colour represents the current velocity value of 3.06 m/sec. the red colour dominates the outer side of the river (right bank), yellow to blue colours dominate the inside of the river (left bank) and the middle of the river. by placing the groyne building on the outer side of the river (right bank) can reduce the river flow velocity to a low, where the low flow velocity allows sedimentation to occur on the outer side of the river (right bank), so that the process of placing the groove as a river flow direction building can function in accordance with that was planned. figure 20. rma simulation results (q20) scenario 7 figure 21. sed2d simulation results (q20) scenario 7 • model simulation sed2d the sed2d model simulation aims to determine the distribution of sediment and river bed shear stress by adding 26 groyne, with the dimensions of the groyne: length of 17.5m; groyne inclined 10° to downstream; distance between groyne 35.5 m; due to the influence of q20. from figure 21, it can be seen that blue colours dominate the colour gradation. in scenario 4, there is a change in the river bed due to the q20 flood discharge of 0.05 m to 0.18 m, spread evenly on the left, centre, and right of the river. figure 22 shows that the minimum river bed shear stress occurs on the river's right bank (outer river bend) and the maximum river bed shear stress occurs on the left bank of the river (inner river bend). low riverbed shear stress values allow sedimentation, meanwhile high riverbed shear stress values allow erosion. in this condition, there is a sedimentation process on the river's right bank (outer river bend) and an erosion process occurs on the left bank of the river (bend in the river). civil and environmental science journal vol. 4, no. 1, pp. 043-061, 2021 59 figure 22. distribution of shear stress (ʈ) riverbed scenario 7 (q20) i. comparison of simulation results based on the simulations that have been carried out, the results are obtained in the form of velocity distribution, river bed shear stress, and sediment distribution due to the influence of groyne placement on the outer bend of the river. a comparative analysis of the groyne placement will be carried out from the simulation, which is more useful to reduce scouring on river banks. table 4. recapitulation of velocity distribution cross section velocity right bank (m/sec) scenario 1 scenario 2 scenario 3 scenario 4 scenario 5 scenario 6 scenario 7 p7 1.020 0.027 0.006 0.053 0.030 0.024 0.077 p2 1.391 0.012 0.033 0.027 0.141 0.026 0.110 r3 1.080 0.030 0.047 0.041 0.015 0.036 0.031 r7 1.822 0.035 0.109 0.115 0.041 0.028 0.035 r11 1.610 0.038 0.010 0.103 0.033 0.067 0.029 average 1.385 0.028 0.041 0.068 0.052 0.036 0.056 cross section velocity left bank (m/sec) scenario 1 scenario 2 scenario 3 scenario 4 scenario 5 scenario 6 scenario 7 p7 0.810 1.096 1.111 1.082 1.095 1.074 1.020 p2 1.267 1.719 1.672 1.661 1.602 1.689 1.685 r3 1.521 1.561 1.293 1.314 1.287 1.293 1.354 r7 1.536 2.323 2.335 2.348 2.320 2.359 2.351 r11 2.019 1.890 1.888 1.888 1.891 1.893 1.919 average 1.430 1.718 1.660 1.659 1.639 1.662 1.666 civil and environmental science journal vol. 4, no. 1, pp. 043-061, 2021 60 form table 4, by adding the curly structure on the outer bend of the river or the right bank of the river (scenario 2 – scenario 7), the current velocity on the right bank of the river has decreased significantly with an average value of the flow velocity of the right bank of the river is 0.047 m/sec. with the average value of the current velocity on the river's right bank, which is smaller than the grain sediment's velocity, the deposition process will occur on the right bank. whereas on the river's left bank, with the average value of the flow velocity of the river's left bank is greater than the velocity of grain sediment, then the scouring process will occur on the left bank of the river. form table 5, by adding the curly structure on the outer bend of the river or the right bank of the river (scenario 2 – scenario 7), the value of the riverbed shear stress on the right bank of the river has decreased significantly with an average value of the riverbed shear stress on the right bank of the river of 0.012 n/m2. with a small riverbed shear stress value, it can be said that grain movement has not occurred. while on the river's left bank, the average value of the riverbed shear stress on the left bank of the river is 10.554 n/m2, so it can be said that there will be movement in the grain or called sediment transport. from the analysis of current velocity distribution and river bed shear stress distribution, it can be stated that the flow velocity and river bed shear stress have an equivalent relationship in influencing the river geometry because these two parameters can cause the river to experience scouring and deposition. by placing the groyne on the outer bend of the river, it can reduce the current velocity and the shear stress of the river bed at the outer bend of the river, where the reduced value of the current velocity and the riverbed shear stress on the outer bend of the river can cause a sedimentation process or sedimentation process in the outer bend of the river walk naturally. tabel 5. recapitulation of shear stress cross section riverbed shear stress right bank (n/m2) scenario 1 scenario 2 scenario 3 scenario 4 scenario 5 scenario 6 scenario 7 p7 3.567 0.003 0.000 0.009 0.003 0.002 0.021 p2 6.794 0.001 0.004 0.003 0.061 0.002 0.035 r3 4.126 0.003 0.008 0.059 0.001 0.006 0.003 r7 12.144 0.004 0.040 0.012 0.006 0.004 0.006 r11 9.695 0.006 0.000 0.037 0.004 0.018 0.003 average 7.265 0.003 0.011 0.024 0.015 0.006 0.014 cross section riverbed shear stress left bank (n/m2) scenario 1 scenario 2 scenario 3 scenario 4 scenario 5 scenario 6 scenario 7 p7 2.253 3.993 4.097 3.882 3.992 3.831 3.450 p2 5.666 10.045 9.467 9.418 8.693 9.687 9.630 r3 8.178 7.628 5.755 5.899 5.713 5.763 6.288 r7 8.075 19.508 19.679 19.964 19.494 20.162 19.987 r11 13.868 13.421 13.331 13.270 13.358 13.438 13.770 average 7.608 10.919 10.466 10.487 10.250 10.576 10.625 table 6. recapitulation of riverbed changes cross section riverbed changes maximum (m) scenario 1 scenario 2 scenario 3 scenario 4 scenario 5 scenario 6 scenario 7 p7 0.031 0.138 0.213 0.146 0.029 0.147 0.028 p2 0.041 0.122 0.205 0.134 0.039 0.136 0.038 r3 0.059 0.118 0.242 0.147 0.057 0.150 0.057 r7 0.076 0.105 0.229 0.141 0.074 0.144 0.078 r11 0.095 0.104 0.205 0.141 0.095 0.144 0.099 total 0.301 0.588 1.094 0.709 0.294 0.721 0.301 civil and environmental science journal vol. 4, no. 1, pp. 043-061, 2021 61 from table 6, it is found that the maximum river bed change occurs in scenario 3 of 1.094 m. it means that from the simulation results of the sed2d model, the height of riverbed sediment deposits on the right bank of the river for 230 hours is 1.094 m. 4. conclusions one of the groyne's primary purposes is to reduce the river flow's speed along the riverbank, accelerate sedimentation, and ensure embankments/cliffs' safety against scouring. from the simulation results of the model on the lariang river by adding the groyne building on the outer bend of the river, it was found that for the simulation model scenario 2 to scenario 7, a reduction in current velocity and a decrease in river bed shear stress occurred along the river bank. from the model simulation results by adding a groyne building on the river's outer bend for the simulation model scenario 2 to scenario 7, the largest sedimentation production is in scenario 3, namely the height of riverbed sediment deposits 230 hours of 1,094 m. furthermore, the grout building's effective placement is determined based on a maximum change in the riverbed scenario. in this case scenario 3, wherein the groyne's placement and dimensions are the length of 17.5m; distance between groyne 24.4 m; the groyne is inclined upstream in the direction of flow 10°. references [1] ackers, p., and w. r. white (1973): sediment transport: new approach and analysis, corrections (1993). [2] asdak, c. 1995. hidrologi dan pengelolaan daerah aliran sungai, yogyakarta: gadjah mada university press. [3] chow, ven te, (1997), hidrolika saluran terbuka (open channel hydraulics), erlangga, bandung. [4] donnell, barbara p., letter, joseph v., mcanally, w. h., and others, “users guide for rma2 version 4.5,” [27 sept] 2011, [http://chl.wes.army.mil/software/tabs/docs.htp]. [5] iskandar, 2016. analisa pengaruh penempatan krib terhadap distribusi sedimen di pertemuan sungai garang dan kreo. jurnal teknik pengairan. e-issn: 2477-6068, p-issn: 2086-1761 [6] james zulfan, yiniarti eka kumala, 2018. efektivitas krib untuk mengurangi gerusan di tikungan luar sungai bengawan solo. jurnal teknik hidraulik, vol. 9 no. 2, desember 2018: 115 – 126 [7] letter, joseph v., teeter, teeter, allen m., donnell, barbara p., and others, “user’s guide for sed2d version 4.5 [20 jan] 2006, [http://chl.wes.army.mil/software/tabs/doc.htp] [8] soemarto, cd. 1987. hidrologi teknik. surabaya: penerbit usaha nasional. [9] soewarno. 1991. hidrologi, pengukuran dan pengolahan data aliran sungai (hidrometri). bandung: penerbit nova. [10] sosrodarsono, suyono dan masateru tominaga, k. 1994. perbaikan dan pengaturan sungai. jakarta: pt. pradnya paramita. [11] suharjoko, 2008. methode aplikasi bangunan krib sebagai pelindung terhadap bahaya erosi tebing sungai. jurnal aplikasi issn. 1907-753x [12] haribowo, r., dermawan, v., & yudha, n. (2018). application of artificial neural network for defining the water quality in the river. civil and environmental science journal (civense), 1(1), pp.12-18. doi:https://doi.org/10.21776/ub.civense.2018.00101.2. [13] juwono, p., asmaranto, r., & murdhianti, a. (2020). stability of existing banyukuwung dam in recent hydrology and geotechnical conditions. civil and environmental science journal (civense), 3(2), 60-71. doi:https://doi.org/10.21776/ub.civense.2020.00302.1. civil and environmental science journal vol. 4, no. 1, pp. 030-042, 2021 30 a study of irrigation performance index and real cost value of irrigation operations and maintenance in surak irrigation area tri budi prayogo, sri wahyuni, muhammad iqbal* water resources engineering department, brawijaya university, malang, 65145, indonesia muhammdiqbl@gmail.com1 received 16-09-2020; accepted 14-01-2021 abstract. irrigation asset management is required to maintain the value of irrigation asset function and condition. surak irrigation area is located in lawang sub-district, malang regency. the novelty of this research is the finding of priority to improve irrigation assets equipped with a budget. after resurveying in 2020, 21 points of damaged infrastructure were found in surak irrigation area. the irrigation performance index was found to be 78% (good condition) with the details were as follows: the physical infrastructure aspect was 39%, the water availability aspect was 5 %, the planting index aspect was 4%, the supporting facilities for operation and management aspect was 8%, the organizational and personnel aspect is 11%, the documentation aspect was 4%, and the water user association aspect was 7%. priority calculation utilized the ranking method, which ranks asset values from the lowest to the highest. the result was that 24 assets are in good condition, 43 assets are in good condition, and 146 are in excellent condition. the real cost value of irrigation operations and maintenance was calculated to be idr 1,561,742,000 with idr 208,507,000 for operating costs and idr 1,353,235,000 for maintenance costs. for rehabilitation, it was found that 24 assets need regular maintenance and repair, 24 assets need regular maintenance, and 146 assets need routine maintenance. keywords: asset management, irrigation, performance index, rehabilitation priority 1. introduction irrigation is a crucial factor for maximizing the potential of agriculture productivity to meet food demands. despite the vital position of irrigation in food demands, irrigated crops contribute to 21% of the total agricultural area and consume 69% of withdrawn water resources worldwide (aquastat) [1]. therefore, the agricultural sector has enormous water consumption. the water consumption often leads to surface and groundwater resource depletion in irrigated perimeters, which harms ecosystems and prejudices water access and food security. therefore, the sound management of water resources in 1 cite this as: prayogo, t. b., wahyuni, s., & iqbal, m. (2021). a study of irrigation performance index and real cost value of irrigation operations and maintenance in surak irrigation area. civil and environmental science journal (civense), 4(1), 30-42. doi: https://doi.org/10.21776/ub.civense.2021.00401.4 civil and environmental science journal vol. 4, no. 1, pp. 030-042, 2021 31 irrigated agriculture is key to sustainable development. irrigation asset management is required for the management of physical and non-physical assets contained in irrigation areas. a widespread study on water management led to two relevant concluding statements as follows; 1) it is impossible to feed a fast-growing population with improved living conditions in a region with existing low-level water management and agricultural trends"; 2) "food security is achievable with the existing resources in 2025 if and only if the implementation of proper water management measures is realized" [2]. the food demand in indonesia is supported by indonesia's irrigation policy reform that generated an overall sustained positive impact [3]. with expanding coverage and rising implementation quality, rice production is likely to increase further. according to one study, maintenance in irrigation has helped improve an irrigation system [4]. nevertheless, the improved condition did not elevate the overall declining condition of the irrigation system. by carrying optimal management of irrigation assets, the efficient steps can be determined to extend and maintain asset conditions, determine the priority of assets that require rehabilitation, and estimate the costs incurred for rehabilitation [5]. surak irrigation area is located in lawang sub-district, malang regency, and its primary channel extends across to purwosari sub-district, pasuruan regency. from the obtained preliminary data, there were damages to structures and channels in the area, which causes suboptimal performance of the surak irrigation area. 2. materials and methods 2.1. study location the location of the study is the surak irrigation area in lawang sub-district, malang regency. the intake of surak is the surak dam, located in lawang sub-district, malang regency, and the primary irrigation channel flows alongside the national road to the north until purwosari sub-district, pasuruan regency. figure 1. location of study the surak irrigation area's potential area is 875 ha, and its functional area is 795 ha. the water resources in surak irrigation area are taken from the surak river. the surak irrigation area is located in the brantas river basin. civil and environmental science journal vol. 4, no. 1, pp. 030-042, 2021 32 2.2. primary and secondary data collection the following are the data required in conducting this study: 1. identity data of surak irrigation area 2. physical asset infrastructure data 3. water availability data from 2017 to 2019 4. crop productivity data from 2017 to 2019 5. data on supporting facilities for operations and maintenance 6. organization and personnel data 7. documentation data 8. data of water user associations (wuas) 9. data on wages and material costs in 2019 2.3. stages of the study 1. primary and secondary data collection 2. survey of surak irrigation area 3. calculation of irrigation performance index a. physical infrastructure aspect b. water availability aspect c. crop productivity aspect d. supporting facilities aspect e. personnel organization aspect f. documentation aspect g. water user associations (wuas) aspect 4. priority ordering of physical infrastructure assets 5. calculation of real cost value of irrigation operation and maintenance 6. rehabilitation of irrigation assets 2.4. survey of surak irrigation area surveying the surak irrigation area was the first of many steps to obtain primary data from the field. data regarding dimensions, conditions, functions, coordinates, and documentation were obtained by carrying out the survey. the survey was carried out from the intake structure to the last tapping structure on the irrigation area channel. 2.5. irrigation performance index irrigation project performance evaluation is critical and vital to ensure the sustainability of irrigated agriculture [6]. there is a wide range of choices for characterizing all aspects of performance evaluation; nevertheless, there is still no agreed approach and framework to assess and evaluate irrigation performance. the irrigation performance index measures performance when planning an irrigation area and its performance level when implementing its operations and maintenance. [7]. table 1. percentage weights of the irrigation performance index aspect % physical infrastructure 45 water resource availability 9 crop productivity 6 supporting facilities 10 personnel organization 15 documentation 5 water user associations (wuas) 10 total 100 civil and environmental science journal vol. 4, no. 1, pp. 030-042, 2021 33 2.5.1. physical infrastructure what is meant by physical infrastructure is structure assets or channels in the surak irrigation area. the parameters included as aspects of physical infrastructure are channels, drainage channels, water level regulators, complementary structures, inspection roads, and offices and warehouses. 2.5.2. water resource availability water scarcity is a mounting challenge in many parts of the world, resulting from growing demand from different sources, including agriculture, mining, industry, hydroelectricity generation, and a rising population [8]. therefore, water resource availability is an essential aspect of irrigation performance assessment. water resource availability is defined as the fulfillment of irrigation water resource demands or the k factor calculation. this calculation is based on the average k factor in the first, second, and third planting seasons. 2.5.3. crop productivity the crop productivity aspect is divided into two parts: the actual planting area and rice productivity. the actual planting area aspect is calculated based on the comparison percentage of the actual planting area and the standard or potential area in the first, second, and third planting seasons. meanwhile, rice productivity compares actual rice productivity and the national average rice productivity (6.13 tons/ha) in the first, second, and third planting seasons. 2.5.4. supporting facilities to support various operational and maintenance activities of irrigation areas, it is necessary to possess equipment, transportation, communication tools, and execution offices to be perused by personnel on the field. for this aspect, the condition and percentage of operational support and maintenance facilities that can assist activities in the area were assessed. 2.5.5. personnel organization for this aspect, the structural organization that carries out operations and maintenance of irrigation was assessed based on its legality, personnel sufficiency on the field, and existing personnel's employment status. 2.5.6. documentation to make it easier to carry out a survey or census on the field, documentation for the irrigation area is essential. the documentation aspect assesses the completeness of existing documents such as data books, maps, drawings, and irrigation network schemes for the irrigation area. 2.5.7. water user associations (wuas) typical common-pool irrigation systems are characterized by the rivalry of consumption and exclusion difficulty if not correctly administered. therefore, it is essential for irrigation management to perform collective actions based on farmers' collaborative efforts or cooperation in rural communities, for example, through water user associations (wuas) [9]. transferring irrigation management responsibilities from government agencies to farmers has been essential in many countries [10]. as a result, farmers' participation, especially in wuas in irrigation management, has taken center stage. the irrigators who were considered beneficiaries are now considered partners in the planning, development, operations, and maintenance of irrigation systems. a study found that it is crucial to create an enabling environment to enable farmers to realize profits and other economic benefits to participate in irrigation infrastructure maintenance [11]. development agents should also create farmer organizations to improve farmer cohesion and social capital to civil and environmental science journal vol. 4, no. 1, pp. 030-042, 2021 34 participate in collective irrigation infrastructure maintenance. the evaluation of wua performance is an important management tool to aid in providing a good irrigation service because it may support the system management in the identification of the strengths and weaknesses of an organization as well as the improvement of organizational performance and productivity, taking into account its objectives [8]. the values of the aspect of wuas were determined based on the status and legality of wua associations, the institutional condition of wua associations, frequency of meetings of wuas with their observers or branches, active participation of wuas in surveys, wua participation in irrigation network repair or maintenance and natural disaster rehabilitation, wua fees for the repair and maintenance of tertiary plots, and wua participation in crop planning and water allocation. 2.6. the priority of irrigation asset rehabilitation the priority of irrigation asset rehabilitation was determined by calculating the physical infrastructure aspect with the ranking method. sorting the condition values from the smallest to the largest allows priority to be distinguished from the irrigation area's rehabilitation of assets. 2.7. calculation of real cost value of irrigation operations and maintenance the teal cost value of irrigation operation and maintenance is divided into operations and maintenance costs. the two aspects are then further divided into several other elements: overtime wages, office supplies, lubricants and paints for sluice gates, heavy equipment, business trips, and periodic maintenance. the costs of every item are assessed and controlled based on location and value [12]. 2.7.1. overtime wage the overtime wage aspect in an irrigation area is based on the number of observers, sluice guards, weir operational officers, and field staff assistants. the rate of the wage is different among staff members and follows the regulations specified in the area. 2.7.2. field materials for subsections of an irrigation area field materials for subsections of the irrigation area are based on the operations and maintenance manual. the calculation consists of fuel, materials for sluice gate maintenance, fieldwork supplies, materials for work residence maintenance, and self-managed maintenance materials. 2.7.3. lubricants and paints for sluice gates to maintain the condition of existing sluice gates in irrigation infrastructures, it is necessary to have lubricants and paints for sluice gates based on the number of sluice gates following the field's inventory. the material demand varies depending on the type and dimensions of the sluice gates. 2.7.4. heavy equipment and tools for subsections of an irrigation area heavy equipment and tools for an irrigation area's subsections is the cost needed to obtain vehicles and field tools. these are necessary to deploy sluice guards, weir operational officers, and observers. 2.7.5. business trips for regional technical implementation unit staff, observers, sluice guards, and weir operational officers calculation of business trips for regional technical implementation unit staff, observers, sluice guards, and weir operational officers is based on the frequency of business trips and the number of people. 2.7.6. other expenditures for regional technical implementation unit staff, observers, sluice guards, and weir operational officers other expenditures for regional technical implementation unit staff, observers, sluice guards, and weir operational officers involve operation and maintenance costs (for operational vehicle documents, civil and environmental science journal vol. 4, no. 1, pp. 030-042, 2021 35 costs of printing blanks for operation and maintenance activities, photocopy expenses, meeting and food costs, coaching, and training costs, cropping plan preparation costs, and emergency maintenance costs). 2.7.7. periodic maintenance it is defined as calculating the costs required to maintain physical infrastructure assets in an irrigation area. the calculation of the volume and area of damage from each asset in an irrigation area is obtained by calculating dimensions during the survey. analysis of periodic maintenance costs can be divided into two calculations: channel damage and structural damage. in the channel, the damage that occurs can damage the lining, or transported sediment, garbage, or mud that clogs the irrigation channel. meanwhile, structural damage concerns the need to replace or rehabilitate damaged sluice gates, repairs to structural portions, cleanup of household waste or weeds, and transported sediment, mud, or debris stuck to the sluice gates. after obtaining the volume and extent of damage in the channels or structures, the costs needed to carry out periodic maintenance can be calculated. the calculation is based on the analysis of the work unit price of different jobs and items. the work that needs to be carried out for channel and structure rehabilitation consists of plasterwork (m2), excavation of sediment (m3), river masonry installation (m3), lining masonry installation (m3), replacement of old lining with new lining (m3), and weed clearing (m2). for damage to structures that require replacement of the sluice gates, installation is carried out according to the sluice gates' dimensions and type. the cost prices of materials and wages are according to the location where the work is carried out. after calculating the periodic maintenance, a summary of the real cost value of irrigation operations and maintenance can be made. the costs required to carry out operations and maintenance in an irrigation area can then be found. 2.8. rehabilitation of physical infrastructure assets in irrigation area the rehabilitation of physical infrastructure assets is based on each of the assets [13]. assets with performance indices between 90-100% require routine maintenance, between 80-90% require periodic maintenance, between 60-80% require periodic repair, and below 60% require periodic maintenance in the form of rehabilitation or replacement. 3. results and discussion there are many methods to calculate the irrigation performance index value. the difference of the technique lies between the parameter and percentage in each of the aspects. irrigation performance index can be calculated using the software as such as pdsda-pai 1.0 or 2.0, web-based application e-paksi, fuzzy set theory, direct measurements for indicators, analysis hierarchy process (ahp), and remote sensing (rs although they offer a wide range of choices for characterizing all aspects of performance evaluation. however, still, no agreed approach could be provided to assess the performance of different irrigation systems. it could be concluded that the selection of the evaluation framework and method primarily depends on the nature of the irrigation system and the purpose of evaluation., the assessment was based upon the performance index assessment guide (revision no. 1) that was published as a guide by the water resources department in 2019. this assessment guide is derived from the irrigation performance index assessment based by the ministry of public works and public housing no. 32/2007. the six aspects of the assessment are physical infrastructure water resource availability, crop productivity, supporting facilities, personnel organization, documentation, water user associations (wuas). from previous research in barugbug irrigation area based on the method from no 32/2007, the result was valued at 74,24% and categorized in good condition.[14] additionally, using the same approach in pungkit irrigation area by sijoen using pdsda-pai v.1.0 that based on the same method, the result obtained valued at 68,68% and categorized in mediocre condition. [15]. civil and environmental science journal vol. 4, no. 1, pp. 030-042, 2021 36 the assessment guide provides a much more detailed assessment per aspect to estimate the irrigation condition's value than using the number 32/2007 method, such as filling percentage in the form without an explicit parameter. one of the many clear examples of the detailed parameter in the guide is the weir crest aspect. the following aspect divided into four assessments: weir condition, seepage, surface condition, and pillar in the drainage gate. every aspect has a different percentage of 60%, 10%, 10%, and 20%, respectively. in each element, there are four categories of conditions. it depends on the assessment of the quality of the weir. four types rely on the field's review: excellent (100 90%), good (80 ≤ 90%), average (60 ≤ 80%), and poor (>60%). for weir condition to categorize in excellent condition, it must have a perfect and intact weir without a decrease in elevation. otherwise, to be classified in poor condition, it must have poor, perforated, and peeled surface condition. for this reason, using this detailed guide to assessing the parameter in each aspect will decrease the bias of the surveyor since it has a clear understanding of the assessment. the condition result of the irrigation performance index assessment is different according to the method that has been used. as stated in method number 32/2007, an excellent condition valued at 100-80%, good condition at 79-70%, mediocre condition at 69-55%, and poor condition for value below 55%. [14]. this range value of categories is different from the guide assessment and will differentiate the assessment condition. 3.1. existing channel condition of surak irrigation area after surveying the surak irrigation area in 2020, there were 21 location points of damage. the 21 damage points can be categorized according to their types. they are comprised of 1 illegal structure in the middle of the channel, 14 points of damaged lining, and 6 points filled with sediment and household waste. the majority of the damage occurred in section 1 of the surak primary channel, with eight damage points. 3.2. irrigation performance index calculation 3.2.1. physical infrastructure the physical infrastructure assets in the surak irrigation area scored 39.1% from a maximum of 45%. the score of 39.1% is made up of the aspects of the intake structure that scored 12.8% from the maximum of 13%, the channel that scored 8.4% out of 10%, channel structures that scored 6.8% out of 9%, drainage and structures that scored 2.8% out of 4%, inspection roads that scored the maximum of 4%, and housing, offices, and warehouses that scored 4.4% from the maximum of 5%. the intake structure score of 12.8% was obtained from the weir aspects that scored 3.8%, the weir sediment gate and gears that scored 7%, and the sediment trap and drain gate that scored 2%. the irrigation channel score of 8.4% was obtained from the average condition of the existing channel in surak irrigation area. the aspects assessed for the irrigation channel were the shift in the channel profile, the number of illegal taps and leaks, sediment or erosion that affect its capacity, height and stability of the embankment, slope or wall conditions, and channel rehabilitation. regulatory and complementary structures scored 6.8%, which was obtained from the aspects of regulatory structures that scored 1.7%, discharge measurement structures that scored 2.04%, complementary structures that scored 1.76%, and structure rehabilitation that scored 1.28%. the regulating structure aspect scored 1.7%, obtained from primary and secondary channel structures that scored 0.9%, and tertiary tapping structures that scored 0.8%. the aspect of discharge measurement structures scored 2.04%, which was obtained from the structure's aspects that scored 0.86%, individual measurement structure that scored 0.73%, and individual tertiary tapping structures that scored 0.45%. the aspect of complementary structures scored 1.76%, which was obtained from an average asset value that scored 0.72% and wastes conditions that scored 1.04%. civil and environmental science journal vol. 4, no. 1, pp. 030-042, 2021 37 the aspect of inspection roads for surak irrigation area scored the maximum of 4%. the maximum score is that surak irrigation area is located along a national highway, making it easier to access channels and structures. only a few secondary sections require walking to reach them. the aspect of housing, offices, and warehouses scored 4.4% out of 5%. the regional technical implementation unit of pekalen river basin in the city of pasuruan, which manages the surak irrigation area, had 2% for the office aspect, 0.8% for the housing aspect, and 1.6% for the warehouse aspect. 3.2.2. water resource availability the aspect of water resources availability in the surak irrigation area scored 5.4% out of the maximum of 9%. the k factor calculations for the entire year of 2019 showed that planting season i was 0.59, planting season ii was 0.43, and planting season iii was 0.39. following the criteria and weight of irrigation performance assessment, the surak irrigation area has a reasonably small k factor. the first, second, and third planting seasons are less than 0.6. this condition is categorized as bad (< 60%) based on the irrigation system's performance appraisal criteria and weight. 3.2.3. crop productivity the actual crop index is the percentage ratio between the planted area and the irrigated area's total area. calculations for the entire year of 2019 showed that the averages were 89.3% for planting season i, 86.8% for planting season ii, and 4.9% for planting season iii. comparing the actual planting area and the standard area for planting seasons i, ii, and iii is < 60%. thus, according to the criteria and weight of the irrigation system performance appraisal, it can be concluded that the actual planted area in the surak irrigation area is categorized to be in bad condition. crop productivity is the percentage that becomes the parameter for paddy productivity in tons per hectare. in the irrigation system performance of evaluation weight criteria, rice productivity is parameterized as the comparison percentage of actual crop productivity to the national average rice productivity (6.13 tons/ha) in planting seasons i, ii, and iii. according to the data available at the regional technical implementation unit of pekalen river basin, the surak irrigation area, located in purwosari sub-district, has crop productivity of 7.5 tons/ha. 3.2.4. supporting facilities data for the aspect of supporting facilities obtained from interviews and surveys showed that the percentage for the number of personnel reaches 100%, which in other words is sufficient. almost all of them are in good condition, and they received a maximum score of 0.5%. there is still no heavy equipment that can support the operation and maintenance of the surak irrigation area, and therefore the score for the heavy equipment aspect is 0.9%. the accumulated score for the operation and maintenance aspect was 3.4%, from a maximum of 4%. there is still no transportation available at the regional technical implementation unit to support operations and maintenance for the transportation aspect, which has a weight of 2% for the surak irrigation area. as a result, the transportation aspect is categorized in bad condition (< 60%) with a score of 1.2% out of 2%. the office equipment and furniture at the regional technical implementation unit of pekalen river basin can be complete. there are desks, chairs, file cabinets, filing shelves, filing cabinets, computers, calculators, and stationery; almost all are in good condition. thus, supporting equipment for office and operations received a maximum score of 2%. communication equipment that can support operations and maintenance in the surak irrigation area, such as radio, ssb, walkie-talkies, and cell phones, still has not been provided by the regional technical implementation unit of pekalen river basin. even though the officers in the field have access to a good communication network, these must still be provided by themselves. therefore, communication equipment is categorized as being in bad condition (< 60%) and received a score of 1.2% out of 2%. the accumulated score for supporting facilities for operations and civil and environmental science journal vol. 4, no. 1, pp. 030-042, 2021 38 maintenance in the surak irrigation area was 7.8% out of the maximum of 10%. this aspect is categorized as good (60-80%). 3.2.5. personnel organization from the results of interviews conducted with observers, sluice guards, and weir operational officers representing the surak irrigation area, it was found that the frequency of routine meetings to discuss irrigation operations and maintenance issues was adequate, and they had carried out their duties following the operations and maintenance manual. from the interviews and observations, a score of 3.82% from 5% was obtained for organizational structure and maintenance. one observer's demand was met, but one weir officer's need was not met, while the demand for four sluice guards was also completed. thus, the score was 2.5% from a maximum of 4%. meanwhile, the observer's employment status is a civil servant, and one of the sluice guards and weir operational officers is a civil servant, which earned a score of 1.8% out of the maximum of 2%. to find out how much the observers, guards, and weir operational officers understood their tasks and functions, a questionnaire was distributed containing ten questions about irrigation operations and maintenance's understanding. each question weights 10%, which is then categorized again into several levels based on the answers given. from the results of the questionnaire, the average understanding of operations and maintenance for observers (75%) and guards and weir operational officer (65%) were categorized as good (60-80%). the data entry and reporting were carried out in an orderly, correct, and valid manner. for the personnel, the total score for understanding tasks and functions, and the frequency of training implementation and data input was 6.98% out of the maximum of 10%. the fundamental aspect of personnel organization attained a score of 10.8% out of the maximum of 15%. 3.2.6. documentation from the survey results at the regional technical implementation unit office of pekalen river basin to collect documentation data for the surak irrigation area, only several available documentation data were obtained, such as a map of the irrigation network scheme. there was still no printed documentation data on the office walls. the as-built drawings and maintenance maps even could not be provided. the surak irrigation area's authority had just been transferred from the regional technical implementation unit of purwosari to the regional technical implementation unit of pekalen river basin. for these two aspects, because the irrigation area data book was still not available, the condition is categorized as bad (< 60%) and scored 1.2% out of 2%. for maps and figures, they scored 2.6% out of 3% because schematic drawings were available. the total score for the documentation aspect was 3.8% out of the maximum of 5%. 3.2.7. water user associations (wuas) for the first aspect, the alliance of water user associations (wuas) of tirto makmur did not have association articles. thus it is categorized in bad condition (<60%) and scored 0.9% out of 1.5%. from the results of interviews with the regional technical implementation unit of purwosari as the previous authority of surak irrigation area, the alliance of water user associations (wuas) located in the surak irrigation area has not been developed because it is still at the stage of collecting contributions to finance the supervision of the sluice gate during the dry months. thus, it was categorized in bad condition (< 60%) and scored 0.15% out of 0.5%. the frequency of meetings of the wua alliance with observers is irregular, but the discussions were still held. 90-100% of alliances of water user associations (wuas) and water user associations (wuas) were present at the meetings. it was found through interviews with the regional technical implementation unit of purwosari and the regional technical implementation unit of pekalen river basin. therefore, this condition scored 0.8% out of a maximum of 2%. the alliance of water user associations (wuas) located in the surak irrigation area was still not active enough to carry out irrigation network surveys. it was scored 0.6% out of the maximum of 1%. civil and environmental science journal vol. 4, no. 1, pp. 030-042, 2021 39 the tirto makmur alliance is quite active in participating in the repair or maintenance of networks caused by natural disasters and was scored 1.8% out of the maximum of 2%. however, it is still not active enough to obtain contributions for the maintenance of irrigation networks and was scored 0.6% out of the maximum of 2%. the tirto makmur alliance has been quite active in participating in crop planning and water allocations and thus was scored 0.8% out of the maximum of 1%. 3.2.8. summary of surak irrigation area performance index after the seven aspects were scored, the total irrigation performance index for the surak irrigation area was scored. the irrigation performance index had a score of 77.56% and is categorized in good condition (60-80%). table 2. surak irrigation performance index aspect % physical infrastructure 39.1 water resource availability 5.4 crop productivity 4.4 supporting facilities 7.8 personnel organization 10.8 documentation 3.8 water user associations (wuas) 6.3 total 77.56 3.3. calculation of asset priority the priority for rehabilitating damaged assets was obtained from ranking the performance indices from lowest to highest. the evaluation followed the evaluation of the physical infrastructure aspects in scoring the irrigation performance index. the physical assets whose priorities were evaluated are in the form of building assets and channel assets. the total number of these two assets is 215 units, with 191 buildings and 24 channels. table 3. summary of physical infrastructure by condition aspect % excellent 146 good 43 average 24 total 213 3.4. calculation of real costs of irrigation operations and maintenance 3.4.1. calculation of overtime wages the calculation of overtime wages in an irrigation area depends on the number of observers, sluice guards, and weir operational officers. the surak irrigation area itself has one observer as well as five sluice guards and weir operational officers. data for overtime wages of observers, sluice guards, and weir operational officers were obtained from the operations and maintenance manual. the resulting wage of observers was idr 24,000,000 and of sluice guards and weir operational officers was idr 90,000,000. 3.4.2. field material for subsections of an irrigation area calculation of the demand for field material for an irrigation area's subsections was based on the operations and maintenance manual for the pekalen river basin. the material requirements are the result of surveying materials needed for operations and maintenance. the calculated costs were idr 17,043,360 for fuel, idr 12,775,181 for materials for maintaining the sluice gate, idr 6,110,575 for fieldwork equipment, and idr 593,250 for the cost of building civil and environmental science journal vol. 4, no. 1, pp. 030-042, 2021 40 materials. the price for materials for the maintenance of the work residence is non-existent because there are technicalities with the work residence. the total cost for the needs of on-the-field materials for subsections of an irrigation area was found to be idr 36,522,366. 3.4.3. lubricants and paints for sluice gates demand for lubricants and paints was calculated based on the number and type of sluice gates in the surak irrigation area. from the available data, it was found that the surak irrigation area has two types a sluice gates, 2 type b* sluice gates, and 16 type c2 sluice gates. each type of sluice gate has different needs for lubricants and gate painting. the required costs were found to be idr 10,520,811. 3.4.4. heavy equipment and tools for subsections of an irrigation area the costs of heavy equipment and machinery needs for the subsection of an irrigation area in the field are costs for purchasing vehicles and purchasing fieldwork equipment. although surak irrigation area still does not have a guard, the prices are still budgeted for the needs of future deployment of a guard. a vehicle's costs were found to be idr 40,000,000.00, and costs for purchasing fieldwork equipment were found to be idr 24,192,768.00. thus, the total costs of equipment and machinery needed for subsections of an irrigation area in the field were found to be idr 64,192,768.00. 3.4.5. business trips for regional technical implementation unit staff, observers, sluice guards, and weir operational officers the costs of business trip needs are adjusted to the regional technical implementation unit's deployment needs to locations in the field. the total budget is designated for one observer and one guard or officer. the resulting costs were found to be idr 2,700,000.00 per month and idr 6,264,000.00 per year. 3.4.6. other expenditures for regional technical implementation unit staff, observers, sluice guards, and weir operational officers other regional technical implementation unit staff, observers, sluice guards, and weir operational officers consist of operations and maintenance costs. the included cost items are operational vehicle documents, printing blanks for operation and maintenance activities, photocopies, meetings and food, coaching and training, cropping plan preparation, and emergency maintenance. the total costs were found to be idr 48,242,890.00. 3.4.7. calculation cost of periodic maintenance of the 21 location points that need to be rehabilitated, 14 of them consist of lining damage. the damages are comprised of collapsed left and right linings. from the survey results, the total volume and area of damage in the surak irrigation area and the resulting total volume of material that needs to be rehabilitated were found to be 66.87 m3. the other 6 points involve damage due to sediment and mud. according to the survey results, the calculated volume of sediments in the surak irrigation area was found to be 84.76 m3. the volume of damage to structures was calculated based on the conditions and types of damage that occurred to the structures. in the surak irrigation area, 19 assets were found with different kinds of damage. the work required to repair the damage constitutes plasterwork, sediment excavation, river masonry installation, surface masonry installation, and weed clearing. rehabilitation or replacement of sluice gates is already included in the analysis of work unit prices according to the dimensions of the sluice gates in the structures. structure b.sk.10i involves replacement of 2 gear spindles (b = 1.5 m, h = 1.5 m); structure b.mp.5 involves replacement of 2 tertiary sluice gates (b = 0.5 m, h = 0.6 m); and structure b.mp.4 involves replacement of 1 tertiary sluice gate (b = 0.5 m, h= 0.6 m) and another tertiary sluice gate (b = 0.2, h = 0.6). the calculation of the volume of materials that need to be rehabilitated in structures and channels is followed by calculating periodic maintenance's quantity and price. there are three aspects of the civil and environmental science journal vol. 4, no. 1, pp. 030-042, 2021 41 calculation of periodic maintenance: general items, channel rehabilitation, and structure rehabilitation. general items comprise the work required to start channel rehabilitation and structure rehabilitation. general items consist of deployment and return, temporary road construction and village road maintenance, and mutual check and as-built drawings. the calculation of the construction and channel work volumes was then multiplied by each item's work unit price according to current work unit prices and analyses of work unit prices for all the respective items. the resulting costs were found to be idr 89,792,947.29 for general items idr. 904,623,785.1 for channel work, and idr 173,081,155.30 for structure work. the total cost required for periodic maintenance was found to be idr 1,167,497,887.73. to account for vat, 10% was added to the cost, and after rounding, the resulting cost was found to be idr 1,284,247,600.00 (one billion two hundred eighty-four million two hundred forty-seven thousand six hundred rupiahs). 3.4.8. summary of real cost value of irrigation operation and maintenance calculations after calculating the real cost value of irrigation operations and maintenance, the surak irrigation area's total costs were calculated. costs of operational activities were found to be idr 208,506,890.00, and maintenance costs were found to be idr 1,353,234,758.82. the total costs of both operations and maintenance activities were found to be idr 1,561,741,648.82. 3.5. rehabilitation of physical infrastructure in surak irrigation area the rehabilitation of physical infrastructure in the surak irrigation area can be categorized based on the performance index. one hundred forty-six assets need routine maintenance (indices of 90-100%), 43 assets that need periodic maintenance (indices of 80-90%), and 24 assets that require periodic repair (indices of 60-80%). 4. conclusion from the results of the calculations that have been presented, it can be concluded that the surak irrigation area has 21 location points that need rehabilitation, and its irrigation performance index is 77.56%, which falls into the medium condition category (60-80%). additionally, if the performance index is categorized using the range from method no.32/2007, it will fall into the same condition. there is no significant difference from the results of the previous research on pungkit and barugbug. it caused by the method used is further derived from the existing techniques 32/2007. therefore, the results are still in the same range. however, the assessment results obtained have more specific details than previous studies. from the survey, there is a total of 213 physical infrastructure assets in the surak irrigation area. from the calculation of the irrigation performance index, 24 physical infrastructure assets are prioritized for maintenance. these 24 assets consist of 9 waterfall structures, five tapping structures, two side spillway structures, two tapping structures, three culverts, and three bridges. the calculated real cost value for irrigation operations and maintenance of the surak irrigation area is idr 1,561,741,648.82. following the calculation of priority and importance of physical infrastructure assets, 24 assets require repair maintenance, 43 assets need periodic maintenance, and 146 assets requiring routine maintenance. 5. acknowledgments gratitude is due to the regional technical implementation unit of pekalen river's operational and maintenance staff and the regional technical implementation unit of purwosari. references [1] d. a. zema, a. nicotra, l. mateos, and s. m. zimbone, "improvement of the irrigation performance in water users associations integrating data envelopment analysis and multiregression models," agric. water manag., 2018, doi: 10.1016/j.agwat.2018.04.032. civil and environmental science journal vol. 4, no. 1, pp. 030-042, 2021 42 [2] l. mateos et al., "irrigation performance before and after rehabilitation of a representative, small irrigation scheme besides the senegal river, mauritania," agric. water manag., 2010, doi: 10.1016/j.agwat.2010.01.021. [3] g. j. alaerts, "adaptive policy implementation: process and impact of indonesia's national irrigation reform 1999–2018," world dev., 2020, doi: 10.1016/j.worlddev.2020.104880. [4] sobriyah, sucipto, and a. h. wahyudi, “the maintenance evaluation of sungkur irrigation system at ponorogo regency,” 2013, doi: 10.1016/j.proeng.2013.03.060. [5] ministry of public works and public housing, peraturan menteri pekerjaan umum republik indonesia nomor 13/prt/m/2012 tentang pedoman teknis inventarisasi aset irigasi [minister of public works of the republic of indonesia regulation number 13/prt/m/2012 on the technical guidelines for survey of irrigation assets]. indonesia, 2012. [6] a. e. elshaikh, x. jiao, and s. hong yang, "performance evaluation of irrigation projects: theories, methods, and techniques," agricultural water management. 2018, doi: 10.1016/j.agwat.2018.02.034. [7] ministry of public works and public housing directorate general of water resources, kriteria dan bobot penilaian indeks kinerja irigasi revisi i [evaluation criteria and weights for the irrigation performance index, revision i]. 2018. [8] b. e. bravo-ureta, d. higgins, and a. arslan, "irrigation infrastructure and farm productivity in the philippines: a stochastic meta-frontier analysis," world dev., 2020, doi: 10.1016/j.worlddev.2020.105073. [9] t. takayama, h. matsuda, and t. nakatani, "the determinants of collective action in irrigation management systems: evidence from rural communities in japan," agric. water manag., 2018, doi: 10.1016/j.agwat.2018.04.031. [10] a. mishra, s. ghosh, r. k. mohanty, and p. s. brahamand, "performance evaluation of a rehabilitated minor irrigation project and augmentation of its water resource through secondary storage reservoir," agric. water manag., 2013, doi: 10.1016/j.agwat.2013.06.006. [11] s. sharaunga and m. mudhara, "determinants of farmers' participation in collective maintenance of irrigation infrastructure in kwazulu-natal," phys. chem. earth, 2018, doi: 10.1016/j.pce.2018.02.014. [12] ministry of public works and public housing, peraturan menteri pekerjaan umum republik indonesia nomor 28/prt/m/2016 tentang pedoman analisis harga satuan pekerjaan bidang pekerjaan umum [minister of public works of the republic of indonesia regulation number 28/prt/m/2016 on the guideline of analysis of work unit prices of public works]. 2016. [13] ministry of public works and public housing, menteri pekerjaan umum republik indonesia nomor 12/prt/m/2015 tentang eksploitasi dan pemeliharaan jaringan irigasi [minister of public works of the republic of indonesia regulation number 12/prt/m/2015 on the exploitation and maintenance of irrigation networks]. 2015. [14] mulyadi, i. soekarno, s. natasaputra, irrigation performance assessment by permen pu no.32/2007 and masscote methode approach with rapid appraisal procedure (rap) evaluation at barugbug irrigation area west java. jurnal irigasi – vol. 9, no. 2, october. 2014. [15] r. e. sijoen, w. soetopo, l. d. nugroho, analisa indeks kinerja dalam rehabilitasi daerah irigasi pungkit kecamatan lopok kabupaten sumbawa dengan menggunakan software pdsda-pai versi 1.0. 2015. civil and environmental science journal vol. 4, no. 2, pp. 141-153, 2021 141 the dynamics of flow discharge and suspension flow discharge in volcano watershed with agroforestry land cover la ode hadini1, junun sartohadi2, m. anggri setiawan3, djati mardiatno3 1 faculty of earth sciences and technology, universitas halu oleo, kendari 93132 2faculty of agriculture, universitas gadjah mada, yogyakarta 55281 3faculty of geography, universitas gadjah mada, yogyakarta 55281 hadini74@gmail.com1 received 12-01-2021; accepted 27-06-2021 abstract. the suspension flows the upper part of a volcano watershed, which has a very thick soil condition, is sensitive to land use. agroforestry is the dominant land use in the volcanic landscape of indonesia. this research, performed in the agroforestry area, covered the characteristics of the correspondence between flow discharge and suspension discharge during the flow. the suspension flow was measured at the outlet of key watershed areas, which yielded 436 suspension data. the measurement analysis was conducted at every rain event in the field and the laboratory. the crop characteristics in the catchment area were recorded in detail during the field survey. the characteristics of the channels converging toward the gully system were observed during the field survey. there were the relationship patterns between the peak flow discharge and the suspension discharge with the average time interval between the rain events, and the occurrence of suspension flow was 17.7 minutes, and the peak suspension content varied with an average of 1.03 g/l; then the grain size of the suspension was dominated by clay fraction with an average of 73% at the rising stage and average of 69% the falling stage. keywords: agroforestry, discharge, suspension, volcano, watershed. 1. introduction the land use pattern in volcanic lands in indonesia is distinctive. indonesia has more than 400 volcanoes, 127 of which are included in the active category [1]. the order of a volcanic landscape starts from the cone, the upper slope – the foot slope. this landscape's typical land use pattern is the nonintensive utilization of cone and upper slope due to high-intensity volcanic hazards [2]. production activities in the form of agroforestry have recently appeared in the middle slope [3]. agricultural land usually occupies areas from the foot slope [4]. the suspension flow from the upper part of a volcanic watershed with very thick soil conditions is sensitive to land utilization. the suspension flow dynamics illustrate the flow response to the dynamics 1 cite this as: hadini, l.o., sartohadi, j. &setiawan, m.a., mardiatno, d. (2021). the dynamics of flow discharge and suspension flow discharge in volcano watershed with agroforestry land cover. civil and environmental science journal (civense), 4(2), 141-153. doi: https://doi.org/10.21776/ub.civense.2021.00402.4 mailto:hadini74@gmail.com civil and environmental science journal vol. 4, no. 2, pp. 141-153, 2021 142 of the watershed characteristics, one of which is the land use pattern. the suspension flow dynamics are essential to identify the watershed criticality qualitatively. this approach, however, requires further development to achieve time and cost-effectiveness, and efficiency [5][6][7]. the suspension flow is strongly related to soil loss rate and soil fertility deterioration process. it also triggers deposition and sedimentation, which lead to siltation [8][9][10][11]. the dynamics of the suspension flow characteristics and the change in watershed conditions are observable during certain rainfall events. the relationship between these two dynamics is explainable through suspension hydrograph analysis. in a hydrograph, flow discharge and suspension discharge parameters depict the aforementioned dynamics [12][13][14][15][16][17][18][19]. these dynamics are associated with the balance system between rainfall as the input, infiltration, and soil water storage in a watershed area [18][20][21][22][23]. the suspension flow dynamics presented in the suspension hydrograph’s response demonstrate any changes in rain input, infiltration, and soil water storage. the studies of flow suspension dynamics under the land use of agroforestry have been reported to be optimal enough to control the formation of suspension flow [18][24][25][26][27][28]. however, they do not deal with the physical characteristics of watersheds and landscapes covered with homogeneous agroforestry as crucial watershed areas. furthermore, the studies of flow and suspension flow dynamics in volcanic watersheds have so far taken place in watershed areas with varied land use patterns along with other geophysical conditions that involve many assumptions or generalizations. therefore, the results of studies based on this assumption generalization pose a potential bias toward the real states in the field. this research aims to involve a key area approach particularly for a watershed with small area coverage and homogeneous agroforestry and geophysical conditions. this approach enables planning the watershed’s physical characteristics in a more detailed and uniform manner to create a study that approximates the actual conditions in the field. also, it can make a study applicable to volcanic watersheds with similar characteristics. the study of flow suspension dynamics in volcanic watersheds with agroforestry covers the following problems: the corresponding responses of flow and suspension, the time lag between rain events and the initial formation of suspension flow, and the grain size of the suspension during the flow. 2. material and methods this study used a key area method. with a large area of ±300 ha (0.03 km2), bompon watershed was designated as the key area because its land utilization was agroforestry, mainly in the volcanic foot slope area. it is a volcanic watershed on the borders of magelang regency, purworejo regency, and wonosobo regency, central java (figure 1). it lies between 9163200 mn 916400 mn and 396300 me 397800 me with an elevation between 377 and 539 m above sea level. unevenly distributed rainfall with an annual average of 2,214.5 mm typifies its climatic characteristics. bompon watershed is located in the transition zone between the material deposition zones of the tertiary and quaternary volcanoes on the foot slope of sumbing volcano. it experiences a volcanic intrusion that causes an intensive alteration process on the bedrocks. the intensive alteration and weathering processes result in a soil layer with a thickness of over 10 meters, which is categorized as super thick soil [24][25][26][27][28][29]. the vegetation cover is in the form of agroforestry, i.e., land use with diverse plant types like durian, coconut, green cottonwood, mahogany, albizia chinensis, rosewood, gnetum gnemon, lansium dookoo, lansium domesticum cv. kokossan, jackfruit, bamboo, banana, salacca zalacca, turmeric, javanese turmeric, and cardamom. at the base of the tree stands, there are plants attached to the ground surface, namely grass and aromatic ginger. the vegetation cover is dense (478.78 trees/m2), with a wide canopy spanning between 1-12 meters. the height variation of the vegetation stands forms a plant layering structure (multilayer canopy). the study used a key area method, which was carried out by measuring the suspension flow at the gully outlet; this measurement produced 436 suspension data. the suspension flow was measured at every rain event in the field and in the laboratory. the characteristics of the crop in the rain catchment area were recorded in detail during the field survey. in addition, the characteristics of the channels civil and environmental science journal vol. 4, no. 2, pp. 141-153, 2021 143 converging toward the gully system were observed in the field survey. these data were presented in tables and graphs (suspension hydrograph) to describe the causal relationship between rain phenomena and suspension flows. the suspension flow analysis was built based on rainfall and water level data. the rainfall data included the dynamics of rain depth, intensity, and duration at the initial formation of the suspension flow. the suspension was analyzed using the filtration method, which produced suspension weight and concentration data. the suspension discharge was obtained by multiplying the concentration of the suspensions by flow discharge, as strand (1982) proposed in [30]. the flow discharge obtained for each water level observed at the outlet of a stream gauge with broad-crested weir was calculated using the weir discharge equation [31]. figure 1. the location of key areas in the study site and the geomorphological unit conditions in bompon watershed. civil and environmental science journal vol. 4, no. 2, pp. 141-153, 2021 144 3. result and discussion 3.1. the correspondence pattern between flow discharge and suspension discharge during the rain events, the dynamics of the suspension flow showed correspondence patterns between flow discharge and suspension discharge in the rising and falling phases. at the rising stage, an increase in flow discharge was accompanied by a rise in the suspension discharge and vice versa, a decrease in flow discharge was followed by a decline in the suspension discharge (figure 2). at the peak condition, three correspondence patterns between the flow discharge and the suspension discharge were identified. namely, (1) the peak flow discharge corresponded to the peak suspension discharge, (2) the peak flow discharge preceded the peak suspension discharge, and (2) the peak flow discharge occurred after the peak suspension discharge. table 1. the suspension conditions during the flows in each rain event no rain events number of data rain intensity (mm/hour) peak suspension concentration cp (g/l) peak runoff discharge qp (l/s) peak suspension discharge qsp (g/s) type tqp and tqsp 1 2 3 5 6 7 11 1 18 february 2017 4 8.94 0.0711 13.2745 0.9432 tqp=tqsp 2 20 february 2017 10 8.88 0.2989 14.3273 4.2820 tqp>tqsp 3 21 february 2017-1 7 5.14 0.0016 8.4806 0.0136 tqp<tqsp 4 21 february 2017-2 9 4.44 0.0259 8.4806 0.2197 tqp=tqsp 5 22 february 2017 6 6.86 0.0252 8.0463 0.2025 tqp<tqsp 6 23 february 2017 2 1.80 0.0081 7.2035 0.0586 tqp=tqsp 7 25 february 2017 28 10.71 0.9894 28.4727 28.1720 tqp=tqsp 8 27 february 2017 2 4.40 0.0147 7.2035 0.1057 tqp=tqsp 9 28 february 2017 25 19.55 2.3453 43.5071 102.0355 tqp=tqsp 10 01 march 2017 2 6.60 0.1560 8.4806 1.3230 tqp=tqsp 11 01 march 2017-2 31 29.25 3.0703 129.9952 399.1225 tqp=tqsp 12 02 march 2017 34 22.34 1.9138 106.7442 204.2839 tqp=tqsp 13 05 march 2017 13 12.74 0.5655 39.5293 1.9314 tqp>tqsp 14 07 march 2017 11 27.16 0.3209 25.0950 8.0522 tqp>tqsp 15 18 march 2017 15 25.34 0.6623 18.8337 12.4739 tqp=tqsp 16 25 march 2017 10 16.80 0.9541 18.8337 17.9699 tqp=tqsp 17 26 march 2017 28 36.39 2.8932 142.2171 411.4681 tqp=tqsp 18 5 april 2017 39 75.08 2.7803 316.0675 878.7592 tqp<tqsp 19 6 april 2017 23 26.45 0.8329 118.1667 98.4224 tqp<tqsp 20 18 april 2017 13 29.18 0.9152 32.0076 29.2937 tqp=tqsp 21 19 january 2018 3 10.58 0.1120 10.7772 1.2066 tqp<tqsp 22 20 january 2018 7 3.45 0.8137 11.7526 9.5627 tqp=tqsp 23 21 january 2018 9 5.64 0.1742 8.4806 1.4773 tqp>tqsp 24 23 january 2018 2 4.60 0.2566 6.3958 1.6410 tqp=tqsp 25 24 january 2018-1 5 1.80 0.1519 10.7772 1.6368 tqp>tqsp 26 24 january 2018-2 21 9.60 2.1257 65.4142 139.0481 tqp=tqsp 27 24 january 2018-3 4 2.52 0.2945 10.7772 3.1741 tqp=tqsp 28 24 january 2018-4 4 3.84 0.2765 10.7772 2.9798 tqp<tqsp 29 26 january 2018 3 3.75 0.0553 14.3273 0.7918 tqp>tqsp 30 29 january 2018 3 7.80 0.1513 9.3745 1.4187 tqp=tqsp 31 31 january 2018-1 5 21.42 0.6379 8.4806 5.4094 tqp=tqsp 32 31 january 2018-2 6 16.80 0.1665 8.4806 1.4118 tqp<tqsp 33 1 february 2018 7 22.14 1.2545 14.8651 18.6486 tqp=tqsp 34 4 february 2018-1 5 20.88 0.7136 11.2610 8.0355 tqp=tqsp 35 4 february 2018-2 14 17.28 1.1217 51.8768 58.1903 tqp<tqsp 36 08 february 2018 5 12.48 4.7086 21.2571 100.0904 tqp=tqsp 37 13 februri 2018 21 45.12 2.7227 115.8493 315.4219 tqp=tqsp 38 23 february 2018 12 38.40 0.9552 47.6241 45.4924 tqp>tqsp 39 24 february 2018 5 16.56 0.8113 13.2745 10.7700 tqp=tqsp 40 07 march 2018 11 15.10 2.2446 32.0076 71.8442 tqp=tqsp 41 08 march 2018 16 49.69 3.7600 106.7442 401.3581 tqp=tqsp total 480 min. 2 1.80 0.0016 6.3958 0.0136 0.4500 mean 12 17.26 1.0330 41.1108 82.8962 4.31 max. 39 75.08 4.7086 316.0675 878.7592 18.7692 civil and environmental science journal vol. 4, no. 2, pp. 141-153, 2021 145 in general, the peak conditions showed a corresponding pattern between the peak flow discharge and the peak suspension discharge. out of the 41 rain events observed in the field, (1) the peak flow discharge corresponded to the peak suspension discharge in 26 events, (2) the peak flow discharge preceded the peak suspension discharge in 7 events, and (3) the peak flow discharge occurred after the peak suspension discharge in 8 events (table 1). the flow discharge condition substantially affects the suspension discharge; therefore, it determines the correspondence shape patterns generated by the peak flow discharge and the peak suspension discharge. the influence of flow discharge on suspension discharge is as reported in [32] [33] and [34]. the dynamics of runoff discharge are part of the balance system between the dynamics of rain input, infiltration capacity, and soil water storage [13]. the rain input triggers the formation of suspension flow that follows the dynamics of flow (runoff) formation when infiltration capacity and soil water storage are exceeded [12][14][15][35][36]. figure 2. the types in the correspondence patterns of the peak suspension discharge and the peak flow discharge during the flows in each and several rain events (rain event no. 11 in of the tqp=tqsp; rain event no. 2 in of the tqp>tqsp; and rain even no 19, in of the tqp<tqsp types) civil and environmental science journal vol. 4, no. 2, pp. 141-153, 2021 146 the response of runoff and suspension flow formation dynamics is identifiable by suspension hydrograph analysis. hydrograph analysis illustrates the fluctuating movement of suspension flow following the dynamics of the rainfall characteristics [16][17][18][19]. figure 2 shows that at the beginning of a rain event, the rain intensity and duration are still low, and, therefore, the flow discharge tends to be small. as the rain intensity and duration increase, the flow discharge and the peak suspension flow rise. increased suspension flow discharge occurs because sediment production by raindrops and scouring (erosion) by water flows on the ground surface also increases. increased suspension discharge at the same time as high flow discharge is caused by adequate suspension transport energy. at the recession stage, the rain intensity decreases and, therefore, the flow discharge declines. decreased flow discharge reduces suspension production and sediment transport energy; accordingly, the suspension discharge becomes lower. 3.2. the time lag of the suspension flow formation the time lag from rain events to the initial formation of suspension flow at the outlet varies widely (table 2). it ranges between 4 and 55 minutes with an average of 17.7 minutes and a standard deviation of ± 13 minutes. a high standard deviation indicates that the time lag from the beginning of the suspension flow formation and the rain events to the time at which the flows reach the outlet is highly diverse. in this research, the time lag of the initial formation of suspension flow is controlled by the response of the highly complex watershed condition, which includes the dynamics of the intensity and duration of the previous rain events, the channel’s base flow, the intensity dynamics of the occurring rain event. the statistical analysis results from the correlation test showed that the causal factors with significant correlation coefficients were rain intensity (0.381) and runoff discharge (0.443), whose significance levels were 0.05 and 0.001, respectively. the other factors, namely the dynamics of the time lag, the maximum intensity and duration of the previous rain events, and the base flow condition of the channel, had weak influence with insignificant correlation coefficients. this study generally revealed different time lags from rain events to the initial formation of the suspension flow as a combination of the dynamics of the intensity and duration of previous rain events, the state of the channel’s base flow, and the intensity dynamics of the occurring rainfall. at the beginning of the suspension flow formation, the rain intensity ranged from 1.2 to 97.2 mm/hour with an average of 15.6 mm/hour. the lowest rain intensity to initiate the formation of the suspension flow was 1.2 mm/hour with a time lag of 8-10 minutes. at the beginning of the suspension flow formation, the highest rain intensity was 97.2 mm/hour, with a time lag of 24 minutes. low rain intensity with a shorter time lag is possible when the previous rainfall has high intensity and long duration. the base flow is present at the channel during the occurring rain event (events no. 15 and 17). in rain events no. 15 and 17, the lowest rain intensity (1.2 mm/hour) resulted in shorter time lags, i.e., 8 minutes and 10 minutes, respectively, when the previous rain events had high intensities, i.e., 39.6 mm/hour and 32.4 mm/hour, and long durations, i.e., 90 minutes and 120 minutes, respectively. with high rainfall intensity of 22.14 mm/hours, the time lag was wide (slow) because the previous rainfall had low intensity and short duration and the base flow in the occurring rain event was low (event no. 33). in the event no. 33, the rain intensity was 97.2 mm/hour, but it had a long time lag, i.e., 24 minutes, because of the low intensity (7.2 mm/hour) and short duration (15 minutes) of the previous rainfall. the time lag of the initial formation of suspension flow also varied even when the rain fell with the same intensity. in several observations (events no. 9, 16, 34), the rain intensities were equal (2.4 mm/hour). however, the previous rain events had different intensities, i.e., 6 mm/hour, 4.8 mm/hour, and 97.2 mm/hour, and different durations, i.e., 256 minutes, 75 minutes, and 83 minutes, respectively, indicating different time lags, i.e., 10 minutes, 5 minutes, and 27 minutes, respectively. events no. 15 and 17 also had equal rain intensities, i.e., 1.2 mm/hour. however, the rain events preceding them had different intensities, i.e., 39.6 mm/hour and 32.4 mm/hour, and different durations, i.e., 90 minutes and 120 minutes, which also resulted in different time lags, i.e., 8 minutes and 5 minutes. civil and environmental science journal vol. 4, no. 2, pp. 141-153, 2021 147 table 2. the dynamics of the aspects of previous rain events, occurring rain events, and the formation of suspension runoff no. rain events previous rain events occurring rain events suspension flow events no. rain events time lag to previous rain (hour) max. rain intensity (mm/hour) rain depth (mm) rain duration (minute) rain intensity at the beginning of suspension flow (mm/hour) rain depth at the initial flow the time lag between the initial formation of suspension flow and flow reaching outlet (minutes) base flow condition (mm) suspension flow events runoff discharge (l/s) suspension discharge (gram/s) 1 2 3 4 5 6 7 8 9 10 11 12 13 1 16/02/2017 21 1.2 2.1 15 2.6 4.2 35 not formed 2 17/02/2017 24 3.6 5.1 15 1.2 0.3 35 not formed 3 18/02/2017 18 1.2 0.3 15 15.6 9.6 10 32 formed 11.75 0.08 4 19/02/2017 27 4.8 15.6 45 2.4 1.5 5 not formed 5 20/02/2017 23 2.4 1.5 15 20.4 24.6 55 25 formed 7.2 0.33 6 21/02/2017 (1) 14 20.4 24.6 95 10.8 6 10 22 formed 7.2 0.45 7 21/02/2017 (2) 10 10.8 6 30 16.6 18.3 20 25 formed 7.2 0.04 8 22/02/2017 24 16.6 18.3 120 6 14.7 37 25 formed 7.2 0.19 9 23/02/2017 11 6 14.7 256 2.4 1.5 10 25 formed 7.2 0.06 10 24/02/2017 33 2.4 1.5 30 4.8 4.5 19 not formed 11 25/02/2017 16 9.6 8.7 135 14.4 24.9 28 22 formed 7.2 0.04 12 26/02/2017 18 14.4 24.9 225 4.8 4.5 12 05 not formed 13 27/02/2017 20 4.8 4.5 90 7.2 4.8 8 25 formed 7.2 0.11 14 28/02/2017 13 7.2 4.8 60 6 1.5 14 25 formed 8.48 0.52 15 01/03/2017 (1) 15 39.6 25.5 90 1.2 0.3 10 25 formed 8.48 1.32 16 01/03/2017 (2) 2 4.8 6 75 2.4 0.6 5 25 formed 8.48 1.87 17 02/03/2017 20 32.4 51.3 120 1.2 1.2 8 30 formed 8.48 0.99 18 04/03/2017 40 33.6 36 105 2.4 1.8 25 not formed 19 05/03/2017 28 2.4 2.4 45 2.7 10.8 4 35 formed 13.27 2.08 20 06/03/2017 24 21.6 9.9 60 28.4 1.4 01 not formed 21 07/03/2017 23 26.4 6.9 15 49.2 12.3 14 30 formed 10.78 1.27 22 14/03/2017 (1) 72 12 4.8 15 6 1.5 5 not formed continued to the next page civil and environmental science journal vol. 4, no. 2, pp. 141-153, 2021 148 table 2 (continued) 1 2 3 4 5 6 7 8 9 10 11 12 13 23 14/03/2017 (2) 2 6 2.1 15 2.4 1.5 5 not formed 24 14/03/2017 (3) 1 9.6 12.9 60 2.4 2.4 5 not formed 25 17/03/2017 48 28 21.3 75 2.4 2.2 32 not formed 26 18/03/2017 17 4.8 2.4 90 28.8 7.2 39 formed 1.58 1.41 27 20/03/2017 21 40.8 57 150 4.8 1.8 not formed 28 24/03/2017 72 18 6.9 45 2.4 1.5 22 not formed 29 25/03/2017 16 2.4 2.4 30 5.1 20.4 10 15 formed 4.54 0.54 30 26/03/2017 11 30 42 120 9.6 38.4 14 15 formed 4.54 0.94 31 04/04/2017 (1) 15 2.4 19.8 75 8.4 2.4 not formed 32 04/04/2017 (2) 8 8.4 3.1 15 7.2 1.8 not formed 33 05/04/2017 19 7.2 5.7 15 97.2 24.3 24 15 formed 18.83 11.13 34 06/04/2017 19 97.2 74.4 83 2.4 0.6 27 15 formed 4.54 0.38 35 17/04/2017 120 2.4 1.2 15 16.8 5.4 not formed 36 18/04/2017 17 16.8 5.4 15 22.8 5.7 12 formed 0.55 0.02 mean 24.5 15.3 14.8 68.7 11.7 7.4 17.7 21 7.7 1.2 max. 120 97.2 74.4 256 97.2 38.4 55 35 18.83 11.13 min. 1 1.2 0.3 15 1.2 0.3 4 01 0.55 0.02 sdev. 22.6 18.2 17.6 58.6 17.9 9.1 13.0 10 4.0 2.4 source: field data processing (2017) civil and environmental science journal vol. 4, no. 2, pp. 141-153, 2021 149 this study argued that the time lag of the initial formation of the suspension flow was influenced dynamically by a combination of factors, including the intensity and duration of previous rain events, the intensity of the occurring rainfall, and the base flow of the channel. the combination of these factors significantly controls the initial formation of suspension flow and is supported by the concept of flow formation mechanism. the flow formation mechanism explains that a flow forms when the soil surface receives rain input and absorbs water vertically into the soils by infiltration and percolation. as well as when these processes affect the initial humidity status of the soil surface [36], make the soil watersaturated, and form runoff on the soil surface in the event of excess rainfall [24][22][35]. this study provides the time lag between the initial formation of suspension flow and rain event, which tends to be longer (17.7 minutes) in a volcanic watershed with super thick soils and land cover in the form of agroforestry. the super thick soil in the volcanic watershed has a high clay content (> 50%), and it can bind and store more water; therefore, suspension flow takes a longer time to form [40]. the plant root density under the agroforestry practices is beneficial in initiating the formation of fractures and secondary soil pores to increase infiltration and soil water storage capacity. soil conditions with high infiltration and soil water storage capacity can slow down the process of runoff (flow) formation that carries suspension on the surface, as previously reported by [16][37]. according to [38], soil permeability reflects soil infiltration capacity. the permeability of the super thick soils in the study area ranged from 0.0259 cm/hour to 80.0759 cm/hour with an average of 0.4492 cm/hour (slow). slow soil permeability triggers a faster formation of suspension flow on the soil surface. in line with [39], the combination of initial water content and infiltration affects the initial infiltration rate. when the need to reach the initial soil moisture content is higher, the lower the initial infiltration rate. suspension flow forms when rain input exceeds infiltration capacity; in other words, the formation of suspension flow is highly dependent on the fulfillment of infiltration capacity. the time lag between the suspension flow formation and rain event in this research was wide (17.7 minutes). the wide time lag proves that the vegetation roots in agroforestry land use, which create fractures and soil pores, can increase water absorption in infiltration and soil water storage capacity. the super thick soil condition with high infiltration capacity and large soil water storage in the volcanic watershed can store more water and slow the formation of suspension flow. 3.3. the characteristics of the grain size of the suspension the results presented in table 1 show that the suspension level at the peak suspension flow discharge has a concentration ranging from 0.0016 g/l to 4.71 g/l with an average of 1.03 g/l. the most negligible suspension concentration was 0.0016 g/l, which occurred in the event no. 2 with a peak runoff discharge of 8.48 l/s. the highest suspension concentration was 4.71 g/l, which happened in rain event no. 36 with a peak runoff discharge of 21.26 l/s. in general, the study shows that the peak flow discharge influences the suspension level, i.e., low peak flow discharge has a small suspension concentration. in contrast, high peak flow discharge has a large suspension concentration. the situation in which peak flow discharge affects suspension content is in line with the results of previous studies, including the correlation between suspension’s grain size and flow conditions, namely flow discharge and rate [41][42]. in the study area, the grain size of the suspension in the suspension flow is dominated by clay fraction. the dominant clay fraction corresponds to the clay fraction found in the surface soil layer in the volcanic watershed area. the grain size of the suspension was grouped according to the percentages of the clay, silt, and sand fractions whose granular scales are <0.002 mm, 0.002-0.02 mm, and 0.02-2 mm, respectively. the grain size of the suspension at the rising stage had the following mean percentages: 2% sand, 26% silt, and 73% clay. at the recession stage, the grain size of the suspension was composed of the following mean percentages: 3% sand, 28% silt, and 69% clay. the fraction of the surface soil layer consisted of the following mean percentages: 2% sand, 26% silt, and 73% clay. during the flow events, the clay-sized suspension fraction showed a decrease from 73% at the rising stage to 69% at the falling phase. civil and environmental science journal vol. 4, no. 2, pp. 141-153, 2021 150 meanwhile, the sand-sized suspension increased from 2% to 3%, and the silt-sized suspension also increased from 26% to 29%. the increases in the sand and silt-sized fractions and the decline in claysized grain in the suspension during the flow events not only indicate different levels of transportability between the sand, silt, and clay-sized suspension but also demonstrate an increase in the transportation of sediment originating in the channel during the flow events. clay fractions are mostly transported in the rising phase when flow discharge is low because clay has a very small and delicate size that is more easily suspended and transported. meanwhile, the silt and sand-sized fractions are mostly carried in the recession phase when flow discharge accumulates and becomes larger. silt and sand are larger and coarser so that their disaggregation and transportation processes require stronger flow discharge energy and more prolonged time [43][44][45]. the increased silt and sand contents in the suspension during the flow events indicate that the increased flow discharge can trigger intensive soil disaggregation and sediment transport. this research argues that significant accumulation of flow discharge prompts intensive suspension transport and flow in a volcanic watershed area, which occurs not only on soils with clay content but also on sand and silt fractions. 4. conclusions during the rain events, the dynamics of the suspension flow showed correspondence patterns between flow discharge and suspension discharge in the rising and falling phases. at the peak condition, there are three relationship patterns between the peak flow discharge and the peak suspension discharge, namely (1) the peak flow discharge corresponds to the peak suspension discharge, (2) the peak flow discharge precedes the peak suspension discharge, and (3) the peak flow discharge occurs after the peak suspension discharge. the time lag from rain events to the formation of suspension flow ranges from 4 minutes to 55 minutes, with an average of 17.7 minutes. the wide time lag proves that the vegetation roots in agroforestry land use, which create fractures and soil pores, can increase water absorption in infiltration and soil water storage capacity. the peak suspension content varies between 0.0016 g/l and 4.71 g/l with an average of 1.03 g/l. the grain size of the suspension is mainly from clay fraction with a range of 71% to 76%, and the average is 73% in the rising phase. furthermore, the recession phase ranges between 68% and 71%, with an average of 69%. silt and sand fractions in the suspension are averagely 26% and 2% in the rising phase and 28% and 3% at the recession phase. acknowledgments the authors would like to express their gratitude to all parties, especially the transbulent team for the togetherness during data collection in the field until the realization of this publication material. the authors would also like to thank lpdp (lembaga pengelola dana pendidikan―indonesia endowment fund for education) for the financial support during the course of this education program. references [1] badan geologi indonesia, 2011, data dasar gunung api indonesia, edisi ke-2, kementrian energi dan sumber daya mineral, bandung. [2] asriningrum, w., noviar, h., & suwarsono. 2004. pengembangan metode zonasi daerah bahaya letusan gunungapi studi kasus gunung merapi. jurnal penginderaan jauh dan pengolahan data citra digital, 1(1), pp.66–75. [3] nandini, r & narendra, b.h. 2012. karakteristik lahan kritis bekas letusan gunung batur di kabupaten bangli, bali. penelitian hutan dan konservasi alam, 9(3), pp.199–211. [4] bachri, s., utaya, s., nurdiansyah, f.d., nurjanah, a.e., tyas, lwn., purnama, d.s., & adillah, a.a. 2017. analisis dan optimalisasi potensi lahan pertanian sebagai kajian dampak positif erupsi gunungapi kelud 2014. majalah geografi indonesia, 1790. [5] kimmins, j.p., rempel, r.s., welham, c.v.j., seely, b., & van rees, k.c.j. 2007. biophysical sustainability, process-based monitoring and forest ecosystem management decision support systems. the forestry chronicle, 83(4), pp.502–514. civil and environmental science journal vol. 4, no. 2, pp. 141-153, 2021 151 [6] verstraeten, g., prosser, i.p., & fogarty, p., 2007. predicting the spatial patterns of hillslope sediment delivery to river channels in the murrumbidgee catchment, australia. journal of hydrology, 334(3-4), pp.440–454. [7] kironoto, b.a., 2008. konsentrasi sedimen suspensi rata-rata kedalaman berdasarkan pengukuran 1, 2, dan 3 titik pada aliran seragam saluran terbuka. dinamika teknik sipil, 8(1), pp.59–71. [8] panagos, p, borrelli, p, poesen, j, ballabio, lugato, e., meusburger, k., montanarella, l., & allewl, c. 2015. the new assessment of soil loss by water erosion in europe. environmental science & policy, 54, 438–447. http://doi.org/10.1016/j.envsci.2015.08.012. [9] suripin, 2002. pelestarian sumber daya tanah dan air. andi offset. yogyakarta. [10] merritt, w.s., lecther, r.a., & jakeman, aj. 2003. a review of erosion and sediment transport model. environment model software, 18: 761-799. [11] ma’wa, j., & andawayanti, u. 2009. studi pendugaan sisa usia guna waduk sengguruh dengan pendekatan erosi dan sedimentasi. [12] parsons, a.j., & wainwright, j. 2000. modeling surface runoff. in schmidt, j. (ed). soil erosion, application of physically based models. germany: springer. [13] handayani, y.l., jayadi, r., & triatmojo, b., 2005. optimasi tata guna lahan dan penerapan rekayasa teknik dalam analisa banjir di daerah aliran sungai: studi kasus daerah aliran sungai ciliwung hulu di bendung katulampa. manusia dan lingkungan, 12(2), pp.53–61. [14] oktarina, n.r. 2005. analisis hidrograf limpasan akibat variasi intensitas hujan dan kemiringan lahan (kajian laboratorium dengan simulator hujan). jurnal teknik sipil dan lingkungan. vol. 3, no. 1, maret 2015. [15] walker, s., & mostaghimi, s. 2009. watershed-based systems. in moore, k.m. (ed). the sciences and art of adaptive management innovating for sustainable agriculture and natural resource management. ankeny, iowa: soil and water conservation society. [16] handayani, w., & indrajaya, y. 2011. analisis hubungan curah hujan dan debit sub sub das ngatabaru, sulawesi tengah. jurnal penelitian hutan dan koservasi alam, vol. 8, no.2, pp.143–153. [17] bisantino, t., bingner, r., chouaib, w., gentile, f., & liuzzi, g.t. 2013. estimation of runoff, peak discharge and sediment load at the event scale in a medium-size mediterranean watershed using the annagnps model. land degradation & development. available at: 10.1002/ldr.2213. [18] miller, j.r. mackin, g., & miller, s.m.o. 2015. application of geochemical tracers to fluvial sediment, london: springer. [19] gao, p., deng, j.,chai, x., mu, x., zhao, g., shao, h., & sun, w. 2017. science of the total environment dynamic sediment discharge in the hekou – longmen region of yellow river and soil and water conservation implications. science of the total environment, the, 578, pp.56–66. available at: http://dx.doi.org/10.1016/j.scitotenv.2016.06.128. [20] hergarten, st., paul, g., & neugebauer, h.j. 2000. modeling surface runoff. in schmidt, j. (ed). soil erosion, application of physically based models. germany: springer. [21] poesen, j., nachtergaele, j., verstraeten, g., & valentina, c. 2003. gully erosion and environmental change: importance and research needs. catena, 50, 91-133. http://dx.doi.org/10.1016/s0341-8162(02)00143-1. [22] arsyad, s. 2006. konservasi tanah dan air. bandung: ipb press. [23] fryirs, k.a. & brierley, g.j. 2013. geomorphic analysis of river systems 1st ed., a john wiley & sons, ltd., publication. [24] soemarto, c.d. 1999. hidrologi teknik. pusat pendidikan manajemen dan teknologi terapan. malang. [25] dariah, a., subagyo, h., tafakresnanto, s., & marwanto, s. 2003. kepekaan tanah terhadap erosi. jurnal akta agrosia vol. 8, no.2. [26] morgan, r.p.c. 2005. soil erosion and conservation: third edition. usa; blackwell. civil and environmental science journal vol. 4, no. 2, pp. 141-153, 2021 152 [27] nicótina, l. et al. 2011. hydrologic controls on equilibrium soil depths. water resources research, 47(4), pp.1–11. [28] rusdi, alibasyah, m. r., & abubakar, k. 2013. evaluasi degradasi lahan diakibatkan erosi pada areal pertanian di kecamatan lembah seulawah kabupaten aceh besar. jurnal konservasi sumber daya lahan. pascasarjana universitas syiah kuala, vol. 1, no. 1, mei 2013, 1(1), 24–39. [29] sartohadi, j. 2013. genesis tanah supertebal dan kaitannya dengan longsor dalam di hulu das bogowonto jawa tengah. hibah penelitian dosen. lppm ugm yogyakarta. [30] wulandari, d.a., suripin, and syafrudin. 2014. evaluasi penggunaan lengkung laju debitsedimen (sediment-discharge rating curve) untuk memprediksi sedimen layang. http://eprints.undip.ac.id/4670/dya. [31] herschy, r.w., 2009. streamflow measurement third edit. t. & francis, ed., 2 park square, milton park, abingdon, oxon ox14 4rn. [32] soewarno. 1991. hidrologi pengukuran dan pengukuran daerah aliran sungai. bandung: nova. [33] arianti, f.d., suratman, martono, e., & suprayogi, s. 2012. dampak pengelolaan lahan pertanian terhadap hasil sedimen di daerah aliran sungai galeh kabupaten semarang. jurnal manusia dan lingkungan. vol. 19, no. 3. available at: http://ilib.ugm.ac.id/jurnal/detail.php?dataid=12641 [accessed september 19, 2015]. [34] maulana, r.a., lubis, k.s., & marbun, p. 2014. uji korelasi antara debit aliran sungai dan konsentrasi sedimen melayang pada muara sub das padang di kota tebing tinggi. jurnal online agroekoteknologi, 2(2337), pp.1518–1528. [35] triatmodjo, b. 2013. hidrologi terapan. cetakan ke-3, beta offset, yogyakarta. [36] neno, a.k. et al. 2016. hubungan debit air dan tinggi muka air di sungai lambagu kecamatan tawaeli kota palu. warta rimba,vol. 4 nomor 2 desember 2016, 4, pp.1–8. [36] wang, j., huang, j., wu, p., zhao, x., gao, x., dumlao, m., si, b.c. 2015. effects of soil managements on surface runoff and soil water content in jujube orchard under simulated rainfalls. catena, 135, pp.193–201. available at: http://www.sciencedirect.com/science/article/pii/s0341816215300795 [accessed september 16, 2015]. [37] gumiere, s.j., bailly, j.s., cheviron, b., raclot, d., bissonnais, y.l., & rousseau, a.n. 2015. evaluating the impact of the spatial distribution of land management practices on water erosion: case study of a mediterranean catchment. j. hydrol. eng., 2015, 20(6): c5014004, 20(2004), pp.1–10. [38] haridjadja o, murtilaksono, k., sudarmo, rahman, l.m. 1990. hidrologi pertanian. jurusan tanah. fakultas pertanian. bogor (id): institut pertanian bogor. [39] asdak, c. 2002. hidrologi dan pengelolaan daerah aliran sungai. yogyakarta: gadjah mada university press. [40] mbaya, l.a., ayuba, h.k., & abdullahi, j. 2012. an assessment of gully erosion in gombe town, gombe state. journal of geography and geology, 4(3), pp.110–122. [41] steegen, a., govers, g., nachtergaele, j., takken, i., & poesen, j. 2000. sediment export by water from an agricultural catchment in the loam belt of central belgium. geomorphology, 33, pp.25–36. [42] tillinghast, e.d., hunt, w.f., & jennings, g.d., 2011. stormwater control measure (scm) design standards to limit stream erosion for piedmont north carolina. journal of hydrology, 411(34), pp.185–196. available at: http://dx.doi.org/10.1016/j.jhydrol.2011.09.027. [43] castillo, v.m., mosch, w.m., garcía, c.c., barberá, g.g., cano, j.a.n., & bermúdez, f.l. 2007. effectiveness and geomorphological impacts of check dams for soil erosion control in a semiarid mediterranean catchment: el cárcavo (murcia, spain). catena, 70(3), pp.416–427. available at: http://www.sciencedirect.com/science/article/pii/s0341816206002438 [accessed on september 16, 2015]. civil and environmental science journal vol. 4, no. 2, pp. 141-153, 2021 153 [44] haregeweyn, n., melesse, b., tsunekawa, a., tsubo, m., meshesha, d., & balana, b.b. 2012. reservoir sedimentation and its mitigating strategies: a case study of angereb reservoir (nw ethiopia). journal of soils and sediments, 12(2), pp.291–305. [45] nugroho, s.h. dan basit, a., 2014. sebaran sedimen berdasarkan analisis ukuran butir di teluk weda, maluku utara. jurnal ilmu dan teknologi kelautan tropis, 6(1), pp.229–240. open access proceedings journal of physics: conference series civil and environmental science journal vol. iii, no. 02, pp. 060-071, 2020 60 stability of existing banyukuwung dam in recent hydrology and geotechnical conditions pitojo tri juwono1, runi asmaranto1*, ari murdhianti2 1water resources engineering department, faculty of engineering, universitas brawijaya, malang, 65145, indonesia 2associate expert water resources and dam, pt. triando konsultama, malang, 65145, indonesia runi_asmaranto@ub.ac.id1 received 08-04-2019; accepted 25-06-2020 abstract. banyukuwung dam is located in the villages of sukorejo and sudo, sumber district, rembang regency, central java province. this dam was built in 1995-1997 to serve the needs of 7750 ha of irrigation water and 35 l/s of raw water needs. dam type is homogeneous reservoir, has a height of 19.40 m above the riverbed and 25.40 m above the foundation excavation. the length of the dam peak is 181.00 m and the width is 5.00 m while the reservoir volume under normal water conditions is 1.64 million m3. along with seasonal changes and extreme hydrological behavior and based on an investigation of current geotechnical conditions, stability analysis is needed based on these two conditions. it is very important to plan operational and maintenance activities related to the dam maintenance program. so that it is expected to be useful for the relevant agencies in making operational decisions. the purpose of this study was to determine the stability of the existing banyukuwung dam based on the latest hydrological and geotechnical behavior. the results are expected to provide recommendations in the management, operation and maintenance of the dam manager keywords: banyukuwung reservoir, dam stability, hydrogeotechnical 1. introduction water resources are very important for humans because they are basic human needs. from all of the water on the surface of the earth, only 2.5% is in the form of fresh water. with this very limited amount, then needs the presence of protection on the existence of water resources and their optimal use. in the context of the maximum utilization of water sources, needed the development effort and good water management namely by building reservoirs to store water. banyukuwung dam is located in sumber district, rembang regency, it was built in 1995 [2]. in general, the dam is to collect water that is used to meet various needs including irrigation, raw water, flood control, tourism and others. analysis of the existing banyukuwung dam stabilization needs to be done considering the age of the building which is old and there are some symptoms of damage due to hydraulic behavior, so that the preservation of building functions will be maintained [1][2][3]. 1 cite this as: juwono, p., asmaranto, r., & murdhianti, a. (2020). stability of existing banyukuwung dam in recent hydrology and geotechnical conditions. civil and environmental science journal (civense), 3(2), 6071. doi: https://doi.org/10.21776/ub.civense.2020.00302.1 civil and environmental science journal vol. iii, no. 02, pp. 060-071, 2020 61 2. material and methods 2.1. study location the study location is banyukuwung dam which is located at the coordinate 06°46’51” s and 111°19’18,9” e in banyukuwung, sukorejo and sudo village, sumber subdistrict, rembang regency, central java province. figure 1. location of study banyukuwung dam was built to provide 35 l/s raw water estimated to be able to meet the water needs of ± 20,000 residents in rembang regency, especially kaliori district; and to provide irrigation supplies of around 775 ha through the pentil weir [2]. 2.2. primary and secondary data collection data needed in the processing of this study, among others [2][5]; 1. rainfall data from banyukuwung station for 1973-2017 2. map of the indonesian earthquake 2017 3. geotechnical investigation data of the foundation and body of dam 4. cross section of banyukuwung dam body 5. instrumentation measurement of standpipe piezometer 2.3. study stage the steps of this study are arranged systematically so that facilitate the completion of this analysis. the steps of the study that conducted are as follows [5][6]; 1. primary and secondary data collection 2. determine the regional rainfall 3. test the skewness of rainfall data 4. frequency analysis test 5. goodness of fit test 6. maximum annual daily rainfall 7. analysis of design flood discharge with the latest hydrological conditions 8. flood routing 9. analysis of seepage in the body of the dam using the latest geotechnical data 10. analysis of dam body stability using bishop modified methods uses the latest soil sampling data 2.4. geotechnical survey and investigation a geotechnical investigation survey was conducted to find out the latest geotechnical parameters which include [5][11] sukorejo village rembang regency banyukuwung dam civil and environmental science journal vol. iii, no. 02, pp. 060-071, 2020 62 1. piezometer measurement 2. investigation of undisturbed sampling at : a. physical properties of landfill and foundation b. mechanical properties of soil embankments and foundations c. permeability of embankments and foundation. investigation of land in the field was carried out by pt supraharmonia in collaboration with the dam manager. the location of undisturbed sampling points is as follows: figure 2. drilling bor location of soil properties investigation table. 1. coordinate of drilling bore and depth location x y depth (m) db-1 535460.61 9250423.01 15 m db -2 535403.03 9250413.43 15 m db -3 535398.74 9250439.85 10 m db -4 535396.65 9250459.20 10 m db -5 535327.03 9250448.97 10 m 5 (five) drilling point locations (2 @ 15 m and 3 @ 10 m accompanied by a standard penetration test) have been carried out accompanied by fairly undisturbed samples in several depths of soil. 2.5. hydrological analysis hydrological analysis is done by comparing the analysis of rainfall and flood plans based on the results of analysis of studies in 1999, 2015 and present conditions. hydrological calculations use basic rain data at sulang and sumber rain stations. flood tracing is conducted to determine the modification of flood flow, to find out the maximum outflow discharge and maximum water level above the overflow threshold. frequency analysis can be applied to river discharge or rain data using annual maximum data, the largest data that occurs during one year, measured over several years. there are several forms of continuous (theoretical) distribution functions, which are often used in frequency analysis for hydrology such as the normal distribution, normal log, gumbel, pearson, pearson log, etc [8][15]. db-5 db-1 db-2 db-3 db-4 civil and environmental science journal vol. iii, no. 02, pp. 060-071, 2020 63 figure 3. banyukuwung catchment area (11.20 km2) 2.6. design flood discharge design flood discharge is a flood discharge used to plan the safety level of danger with the largest probability number. to analyze the design flood discharge can be done using the hydrograph method which is conducted using the assist of a synthetic unit hydrograph model and non-hydrographic methods carried out with the help of frequency analysis techniques. in this study conducted the comparison of nakayasu synthetic unit hydrograph method [17], gamma i synthetic unit hydrograph [16] and hss itb synthetic unit hydrograph method [6][8] 2.7. flood routing to obtain the flood water level on the dam body it is necessary to conduct flood routing to determine the outflow discharge of the flood storage in the reservoir [11][17]. the width threshold type spillway is used with elevation and volume as follows [4][12]; q = cd × b × h3/2 ……….(1) with: cd = discharge coefficient b = diversion width (m) h = water level above the spillway (m) t a b le 2 . s o il d a ta o f d ri ll in g b o re f ro m l a b o ra to ry t e st s a m p le n o . 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 b o r e h o le n o . d b -1 d b -2 d b -3 d b -4 d b -5 s a m p le d e p th , m 2 – 2 .5 8 – 8 .5 1 2 -1 2 .5 0 .5 -1 6 -6 .5 1 4 -1 4 .5 2 -2 .5 4 -4 .5 8 -8 .5 2 -2 .5 4 -4 .5 6 -6 .5 0 .5 -1 4 -4 .5 8 -8 .5 s p e c if ic g ra v it y , g s 2 .5 3 2 .5 2 2 .5 2 2 .6 1 2 .6 9 2 .7 1 2 .6 8 2 .6 5 2 .6 9 2 .6 6 2 .6 9 2 .7 2 .5 4 2 .6 4 2 .7 l iq u id l im it ( l l ) 5 2 5 5 4 5 8 5 4 0 3 1 3 8 4 2 3 9 3 7 3 9 3 8 5 3 3 5 3 1 p la st ic l im it ( l l ) 1 7 2 1 1 9 3 3 2 8 2 4 3 0 3 4 3 0 3 0 3 0 2 7 2 0 2 7 2 4 s h ri n k a g e l im it ( s l ) 1 0 1 1 1 1 1 2 1 9 1 9 2 4 2 3 2 4 1 5 1 2 1 0 8 1 3 1 1 in d e k s p la st ic it y ( ip ) 3 5 3 4 2 6 5 2 1 2 7 8 8 9 7 0 1 1 3 3 8 7 l iq u id it y i n d e k s (l i) 0 .8 3 0 .6 8 0 .6 5 0 .5 4 0 .5 8 0 .1 4 0 .5 0 .2 5 0 .1 1 0 .2 9 0 .1 1 0 .1 8 0 .8 5 1 .6 3 0 .1 4 w e t d e n si ty , g r/ c m 3 1 .6 2 1 .6 1 .6 5 1 .5 4 1 .7 6 1 .8 9 1 .8 8 1 .8 4 1 .9 2 1 .9 0 1 .9 2 1 .9 5 1 .6 1 1 .7 7 1 .8 8 d ry d e n si ty , g r/ c m 3 1 .1 1 1 .1 1 1 .2 1 0 .9 6 1 .3 1 .5 1 1 .4 1 .3 5 1 .4 7 1 .4 4 1 .4 7 1 .5 1 1 .0 9 1 .3 4 1 .5 n a tu ra l w a te r c o n te n t, % 4 6 4 4 3 6 6 1 3 5 2 5 3 4 3 6 3 1 3 2 3 1 2 9 4 8 3 2 2 5 p o ro si ty 0 .5 6 0 .5 6 0 .5 2 0 .6 3 0 .5 2 0 .4 4 0 .4 8 0 .4 9 0 .4 6 0 .4 6 0 .4 6 0 .4 4 0 .5 7 1 .4 9 0 .4 4 v o id r a si o 1 .2 6 1 .2 7 1 .0 8 1 .7 3 1 .0 6 0 .7 9 0 .9 1 0 .9 6 0 .8 4 0 .8 5 0 .8 4 0 .7 9 1 .3 3 0 .8 7 0 .8 u s c s c la ss if ic a ti o n c h c h c l c h m l m l m l m l m l m l m l m l c h m l m l civil and environmental science journal vol. iii, no. 02, pp. 060-071, 2020 64 in many cases, to build a fill type dam it is expected to be able to calculate the stability of the talud in order to check the safety of the natural talud, the cut talud, and the fill talud obtained. [1][2]. to determine the condition of the stability of the dam slope, used the modified bishop method. bishop introduced a more thorough solution than a simple slice method. in this method, the effect of the forces on the edge of each slice is taken into account, as follows [3][4][5][14]. tr= 𝑁𝑟   𝑡𝑎𝑛( 𝜑𝑑 ) + 𝑐𝑑  𝛥𝐿𝑛 = 𝑁𝑟 ( 𝑡𝑎𝑛 𝜑 𝐹𝑠 ) + 𝑐 𝛥𝐿𝑛 𝐹𝑠 …………………………………….. (2) 𝑁𝑟 = 𝑊𝑛+𝛥𝑇− 𝑐 𝛥𝐿𝑛 𝐹𝑠  𝑠𝑖𝑛 𝛼𝑛 𝑐𝑜𝑠  𝛼𝑛+ 𝑡𝑎𝑛  𝜑  𝑠𝑖𝑛  𝛼𝑛 𝐹𝑠 ……....……………………………………………………….. (3) 𝐹𝑠 = ∑ (𝑐𝑏𝑛+𝑊𝑛  𝑡𝑎𝑛 𝜑)  1 𝑚𝛼 (𝑛) 𝑛=𝑝 𝑛=1 ∑ 𝑊𝑛 𝑛=𝑝 𝑛=1  𝑠𝑖𝑛  𝛼𝑛 ………………………………………………………….. (4) 2.8. stability against seepage seepage through dam bodies, foundations, abutment, or hills around the reservoir must be controlled, so that excessive uplift force may not occur. the safety of soil fill type dam can be calculated based on the following formula [5]; 𝐹𝑠 = 𝐼𝑐 𝐼𝑒 ≥ 4 …………………………………………………………………………......... (5) 3. result and discussion 3. 1. rain storm and design flood based on the results of frequency analysis based on rainfall data at banyukuwung station, obtained rainfall design and design flood as follows: table 3. recapitulation of the calculation results of rain storm – design flood return period (tr) tr rain storm r (mm) design flood q (m3/s) 1999 2015 2016 2019 1999 2015 2016 2019 10 140.77 98.08 108.91 99.57 140.77 98.08 108.91 99.57 100 216.07 114.64 127.75 124.68 216.07 114.64 127.75 124.68 1000 308.18 126.75 141.53 140.71 308.18 126.75 141.53 140.71 pmp 700 315.53 317 260.60 700 315.53 317 260.60 based on the above analysis, it can be seen that there was a decrease in design flood discharge when compared to the data ranges of the previous year (2015 and 2016). while the difference is significant in 1999, because the catchment area of the reservoir studied was different. table 4 shows the results of the calculation of the rainfall and flood design with return periode each t = 50, 100 and 1000 years. moreover, it is also compared with condition of 0.5 pmf (probable maximum flood) and pmf. civil and environmental science journal vol. iii, no. 02, pp. 060-071, 2020 65 t a b le 4 . t h e r e su lt s o f th e c a lc u la ti o n o f ra in fa ll a n d f lo o d d e si g n i n v a ri o u s t ( re tu rn p e ri o d e ) m o n o n o b e ( 1 h r) t r a in fa ll d e si g n in fl o w o f d e si g n fl o o d o u tf lo w o f d e si g n f lo o d n o te n a k a y a su s n y d e r n a k a y a su e le v a ti o n h d f re e b o a rd s n y d e r e le v a ti o n h d f re e b o a rd (y e a r) (m m ) (m 3 /s ) (m 3 /s ) (m 3 /s ) (m ) (m ) (m ) (m 3 /s ) (m ) (m ) (m ) 5 0 1 1 8 .5 1 1 1 1 .0 8 5 9 .6 6 6 3 .8 9 5 3 .2 2 1 .7 2 0 .7 8 4 7 .1 2 5 2 .8 9 1 .3 9 1 .1 1 1 0 0 1 2 4 .6 8 1 1 6 .8 5 6 2 .7 5 6 7 .3 2 5 3 .2 8 1 .7 8 0 .7 2 4 9 .7 4 5 2 .9 4 1 .4 4 1 .0 6 1 0 0 0 1 4 0 .7 1 1 3 1 .8 5 7 0 .7 9 7 6 .2 9 5 3 .4 4 1 .9 4 0 .5 6 5 6 .5 5 5 3 .0 7 1 .5 7 0 .9 3 0 .5 p m f 1 3 0 .3 0 1 2 1 .9 8 6 5 .4 4 7 0 .3 4 5 3 .4 4 1 .8 4 0 .6 6 5 1 .9 8 5 2 .9 8 1 .4 8 1 .0 2 p m f 2 6 0 .6 0 2 4 3 .9 7 1 3 0 .8 9 1 4 4 .9 5 5 4 .4 7 2 .9 7 -0 .4 7 1 0 9 .1 1 5 3 .9 7 2 .4 7 0 .0 3 o v e rt o p p in g p m f 7 5 0 7 5 0 .0 0 7 0 1 .6 7 3 7 6 .2 2 4 3 3 .1 5 5 8 .2 7 6 .7 7 -4 .2 7 3 3 1 .9 1 5 6 .9 5 .4 0 -2 .9 0 o v e rt o p p in g p m f e m e rg e n c y sp il lw a y 2 6 0 .6 0 2 4 3 .9 7 1 3 0 .8 9 1 3 3 .9 8 5 3 .2 5 1 .7 5 0 .7 5 8 1 .4 9 5 2 .7 6 1 .2 6 1 .2 4 p m f 7 5 0 e m e rg e n c y sp il lw a y 7 5 0 .0 7 0 1 .6 7 3 7 6 .2 2 3 9 8 .3 4 5 6 .1 3 3 .6 3 -1 .1 3 2 8 8 .7 3 5 4 .4 3 2 .9 3 -0 .4 3 o v e rt o p p in g p s a -0 7 t r a in fa ll d e si g n in fl o w o f d e si g n f lo o d o u tf lo w o f d e si g n f lo o d n o te n a k a y a su s n y d e r n a k a y a su e le v a ti o n h d f re e b o a rd s n y d e r e le v a ti o n h d f re e b o a rd (y e a r) (m m ) (m 3 /s ) (m 3 /s ) (m 3 /s ) (m ) (m ) (m ) (m 3 /s ) (m ) (m ) (m ) 5 0 5 9 .1 8 9 4 .4 5 6 7 .6 6 2 6 .2 4 5 2 .4 5 0 .9 5 1 .5 5 5 3 .3 6 5 3 .0 1 1 .5 1 0 .9 9 1 0 0 6 2 .2 7 9 9 .3 9 7 1 .2 4 2 7 .8 9 5 2 .4 9 0 .9 9 1 .5 1 5 6 .4 8 5 3 .0 7 1 .5 7 0 .9 3 1 0 0 0 7 0 .3 1 1 1 2 .2 3 8 0 .5 5 3 2 .2 8 5 2 .5 9 1 .0 9 1 .4 1 6 4 .6 1 5 3 .2 2 1 .7 2 0 .7 8 0 .5 p m f 6 5 .2 1 1 0 4 .1 3 7 5 .1 0 2 9 .3 9 5 2 .5 2 1 .0 2 1 .4 8 5 9 .9 0 5 3 .1 4 1 .6 4 0 .8 6 p m f 1 3 0 .4 3 2 0 8 .2 6 1 5 0 .2 0 6 8 .8 7 5 3 .3 3 1 .8 3 0 .6 7 1 2 7 .1 4 5 4 .2 4 2 .7 4 -0 .2 4 o v e rt o p p in g p m f 7 5 0 3 7 5 .8 4 6 0 0 .5 1 4 3 6 .5 6 2 1 7 .6 2 5 5 .6 7 4 .1 7 -1 .6 7 3 5 3 .3 9 5 7 .6 3 6 .1 3 -3 .6 3 o v e rt o p p in g p m f e m e rg e n c y sp il lw a y 1 3 0 .4 3 2 0 8 .2 6 1 5 0 .2 0 3 5 .9 8 5 2 .2 3 0 .7 3 1 .7 7 8 1 .6 3 5 2 .7 6 1 .2 6 1 .2 4 p m f 7 5 0 e m e rg e n c y sp il lw a y 3 7 5 .8 4 6 0 0 .5 1 4 3 6 .5 6 1 4 4 .6 4 5 3 .3 5 1 .8 5 0 .6 5 3 3 0 .5 1 5 4 .7 0 3 .2 0 -0 .7 0 o v e rt o p p in g civil and environmental science journal vol. iii, no. 02, pp. 060-071, 2020 66 it b 1 a n d i t b 2 ( r = m o n o n o b e 6 h o u r) t r a in fa ll d e si g n in fl o w o f d e si g n f lo o d o u tf lo w o f d e si g n f lo o d n o te n a k a y a su s n y d e r n a k a y a su e le v a ti o n h d f re e b o a rd s n y d e r e le v a ti o n h d f re e b o a rd (y e a r) (m m ) (m 3 /s ) (m 3 /s ) (m 3 /s ) (m ) (m ) (m ) (m 3 /s ) (m ) (m ) (m ) 5 0 1 1 8 .5 1 5 8 .2 9 7 5 .5 0 2 1 .1 0 5 2 .3 1 0 .8 1 1 .6 9 2 1 .3 6 5 2 .3 2 0 .8 2 1 .6 8 1 0 0 1 2 4 .6 8 6 1 .3 1 7 9 .4 2 2 2 .3 9 5 2 .3 5 0 .8 5 1 .6 5 2 2 .6 2 5 2 .3 6 0 .8 5 1 .6 4 1 0 0 0 1 4 0 .7 1 6 9 .1 6 8 9 .6 0 2 5 .7 3 5 2 .4 3 0 .9 3 1 .5 7 2 5 .8 9 5 2 .4 4 0 .9 4 1 .5 6 0 .5 p m f 1 3 0 .3 0 6 3 .9 4 8 2 .8 6 2 3 .2 8 5 2 .3 7 0 .8 7 1 .6 3 2 3 .6 0 5 2 .3 8 0 .8 8 1 .6 2 p m f 2 6 0 .6 0 1 2 7 .8 7 1 6 5 .7 2 5 2 .6 7 5 3 .0 2 1 .5 2 0 .9 8 5 2 .6 6 5 3 .0 3 1 .5 3 0 .9 7 p m f 7 5 0 7 5 0 .0 3 6 7 .5 5 4 7 6 .4 8 1 8 2 .6 0 5 5 .1 2 3 .6 2 -1 .1 2 1 8 8 .8 9 5 5 .2 6 3 .7 6 -1 .2 6 o v e rt o p p in g p m f e m e rg e n c y sp il lw a y 7 5 0 .0 3 6 7 .5 5 4 7 6 .4 8 7 5 .9 6 5 2 .7 0 1 .2 0 1 .3 0 8 1 .7 8 5 2 .7 6 1 .2 6 1 .2 4 i t b 1 a n d i t b 2 ( p s a 0 0 7 = 1 2 h o u r) t r a in fa ll d e si g n in fl o w o f d e si g n f lo o d o u tf lo w o f d e si g n f lo o d n o te n a k a y a su s n y d e r n a k a y a su e le v a ti o n h d f re e b o a rd s n y d e r e le v a ti o n h d f re e b o a rd (y e a r) (m m ) (m 3 /s ) (m 3 /s ) (m 3 /s ) (m ) (m ) (m ) (m 3 /s ) (m ) (m ) (m ) 5 0 5 9 .1 8 5 8 .8 3 6 5 .0 1 2 4 .3 1 5 2 .3 9 0 .8 9 1 .6 1 2 3 .2 1 5 2 .3 7 0 .8 7 1 .6 3 1 0 0 6 2 .2 7 6 1 .9 2 6 8 .4 2 2 5 .8 5 5 2 .4 3 0 .9 3 1 .5 7 2 4 .6 4 5 2 .4 0 0 .9 0 1 .6 0 1 0 0 0 7 0 .3 1 6 9 .9 4 7 7 .2 7 2 9 .8 8 5 2 .5 3 1 .0 3 1 .4 7 2 8 .4 9 5 2 .5 0 1 .0 1 .5 0 0 .5 p m f 6 5 .2 1 6 4 .9 7 7 1 .7 4 2 7 .2 5 5 2 .4 7 0 .9 7 1 .5 3 2 5 .9 9 5 2 .4 4 0 .9 4 1 .5 6 p m f 1 3 0 .4 3 1 2 9 .9 3 1 4 3 .4 8 6 2 .3 1 5 3 .2 0 1 .7 0 0 .8 0 5 9 .5 5 5 3 .1 5 1 .6 5 0 .8 5 p m f 7 5 0 3 7 5 .8 4 3 7 5 .2 1 4 1 4 .1 3 2 1 9 .5 5 5 5 .6 0 4 .1 0 -1 .6 2 1 0 .4 7 5 5 .5 1 4 .0 1 -1 .5 1 o v e rt o p p in g p m f e m e rg e n c y sp il lw a y 3 7 5 .8 4 3 7 5 .2 1 4 1 4 .1 3 7 8 .7 4 5 2 .7 3 1 .2 3 1 .2 7 8 1 .8 9 5 2 .7 6 1 .2 6 1 .2 4 n o te d : e le v a ti o n o f sp il lw a y = 5 1 .5 m ; e le v a ti o n o f d a m = 5 4 .0 m civil and environmental science journal vol. iii, no. 02, pp. 060-071, 2020 67 based on the results of the flood discharge analysis above it can be seen that the condition of the dam is safe against flood discharge of 0.5x qpmf and below. however, it is not safe against qpmf discharge, overtopping will occur, and the watch height is less than the required minimum of 0.75 m. however, if an emergency spillway is utilized, the condition is still safe from qpmf flooding. based on field conditions, the emergency spillway is tending to solidify because it is used as a traffic access for residents in the fields/rice fields. 3. 2. reservoir capacity based on the results of the latest bathymetry measurements, it is known that the reservoir volume at normally water level (nwl) is 1,764,897 m3. while based on the results of a previous study in 1999 from pt.indrakarya [2] the volume of reservoir was 2,293,800 m3, this shows that there was a reduction in sediment by 0.529 million m3, within a period of 19 years or sediment deposition of 27.84 m3/ year. the curved graph of the banyukuwung reservoir capacity results of the latest bathymetry measurements are as follows figure 4. figure 4. reservoir capacity of banyukuwung dam on 2018 3. 3. dam stability analysis 3.3.1.geotechnical properties banyukuwung dam is a type of landfill with material in the form of grayish yellow clay to blackish gray with n values between 9/30 cm to 16/30 cm. whereas in bedrock n values range from 45/30 cm to above 60 / 30cm. permeability test shows that the pile material is waterproof, with k values ranging from 10-5 to 10-8 cm/s. in bedrock k values range from 10-6 to 10-9 cm/sec. the results of laboratory analysis of soil mechanics show that the embankment has a specific gravity of 2.3 to 2.7 with a content weight of 1.51 2.07 gr/cc. atterberg limit shows ll value of 60.8% 69.9%, pl value = 17.6% 25.8%, and pi value = 40.4% 44.1%, so it is included in the ml group (siltlow plasticity). consolidated undrained (cu) triaxial test results the value of c '= 0.14 0.19 kg/cm2 and  = 30o 31o. while the unconsolidated undrained (uu) triaxial results of c = 0.16 0.26 kg/cm2 and  = 22o 29o while the consolidation parameters, cc = 0.2498 0.3019. the area around the pool has hilly morphology with lithology of clay, silt, silty clay and clayey silt which is mostly agricultural land. civil and environmental science journal vol. iii, no. 02, pp. 060-071, 2020 68 3.3.2.seepage analysis of dams the amount of seepage that comes out of the dam body is calculated by finite element in the form of flux, namely the discharge (q) of the seepage that passes through the dam core [7]. the seepage analysis analyzed was at the flood water level (fwl el. +52.5 m), normal water level (nwl el. +51.5 m), and lowest water level (lwl el. +42 m) shown if figure 3 – 5. figure 5. seepage through dam body in fwl conditions figure 6. dam body seepage in nwl conditions figure 7. dam body seepage in lwl conditions the results of seepage analysis on water level conditions are presented as follows: fwl +52.5 m = 9.36 x 10-9 m³/s/m nwl +51.5 m = 8.56 x 10-9 m³/s/m lwl +42 m = 1.11 x 10-9 m³/s/m average = 6.34 x 10-9 m³/s/m x 352 m = 2.23 x 10-6 m³/s average seepage capacity (2.23 x10-6 m³/s) <1% of the average q of river inflow (1.69.10-4 m³/s). therefore, it can be seen the seepage capacity that occurs in the foundation and body of the banyukuwung dam still meets the requirements specified: q average river inflow = 0.016905 m³/s 1% of the average river q = 1.69.10-4 m³/s. 3.3.3. slope stability analysis dam slope stability was analyzed using the bishop modification method produced as shown in figure 8, for optimum base eartquake (obe) conditions with 100 years earthquake return period. the calculation results are then tabulated as follows. civil and environmental science journal vol. iii, no. 02, pp. 060-071, 2020 69 figure 8. analysis of the dam slope stability with obe earthquake load (return periode t = 100 years) table 5. safety factor of obe condition – water level (upstream,us/downstream,ds) condition of dam fs safety factor note y/h = 0.25 y/h = 0.5 y/h = 0.75 y/h = 1 us-empty 1.1 2.46 2.53 2.57 2.60 safe ds-empty 1.1 2.64 2.73 2.78 2.81 safe us -lwl 1.1 2.16 2.22 2.25 2.28 safe ds-lwl 1.1 2.60 2.68 2.72 2.75 safe us-nwl 1.1 2.41 2.51 2.56 2.61 safe ds-nwl 1.1 2.00 2.07 2.10 2.14 safe us-fwl 1.1 2.62 2.75 2.81 2.88 safe ds-fwl 1.1 1.85 1.91 1.95 1.97 safe results of dam slope stability analysis with maximum design earthquake (mde) t = 3000 yr with earthquake map of the 2010, as follows table 6. table 6. safety factor of mde condition – water level (upstream,us/downstream,ds) condition of dam fs safety factor note y/h = 0.25 y/h = 0.5 y/h = 0.75 y/h = 1 us-empty 1.1 1.33 1.46 1.53 1.61 safe ds-empty 1.1 1.31 1.46 1.54 1.62 safe us -lwl 1.1 1.18 1.29 1.34 1.41 safe ds-lwl 1.1 1.33 1.48 1.55 1.64 safe us-nwl 1.1 1.10 1.28 1.28 1.36 safe ds-nwl 1.1 0.98 * 1.09 1.15 1.21 not safe us-fwl 1.1 1.11 1.24 1.31 1.40 safe ds-fwl 1.1 0.911 * 1.01 1.07 1.13 not safe based on the table above it can be seen that the nwl and fwl conditions, with a ratio of y/h = 0.25, the downstream slope conditions are less safe (critical) in the earthquake return period = 3000 . results of dam slope stability analysis with maximum design earthquake (mde) t = 3000 yr with map of the 2017 earthquake, as follows table 7. civil and environmental science journal vol. iii, no. 02, pp. 060-071, 2020 70 table 7. safety factor of obe condition – water level (upstream,us/downstream,ds) condition of dam fs safety factor noted y/h = 0.25 y/h = 0.5 y/h = 0.75 y/h = 1 us-empty 1.1 1.46 1.60 1.66 1.74 safe ds-empty 1.1 1.46 1.61 1.69 1.77 safe us -lwl 1.1 1.29 1.40 1.46 1.52 safe ds-lwl 1.1 1.48 1.63 1.70 1.78 safe us-nwl 1.1 1.29 1.35 1.42 1.50 safe ds-nwl 1.1 1.10 1.21 1.27 1.33 safe us-fwl 1.1 1.24 1.39 1.46 1.55 safe ds-fwl 1.1 1.02 * 1.12 1.17 1.23 not safe based on the table above, it can be seen that in the fwl condition, with a ratio of y/h = 0.25, the downstream slope condition is less safe (critical) in the earthquake return period = 3000 yr 4. conclusions based on the results of the analysis above on the stability conditions of the banyukuwung dam, it can be concluded as follows: under normal load conditions, the hydrological and flood hydraulic conditions are in the "sufficient" category, the seepage condition is safe and the review of the body structure aspects of the dam is "safe". whereas in terms of dynamic (extraordinary) load conditions, the hydrological and flood hydraulic conditions of the category of "less", seepage conditions are safe, while the condition of the dam's body structure is "less safe". consequently, the safety status of the dam is “enough”, but there is a threat to the hydrological/hydraulics conditions at the qpmf discharge potentially overtopping. while the stability of the dam slope there is a threat to the maximum design earthquake (mde), t = 3000 year dynamic load conditions. however, if we look at the design criteria for the banyukuwung dam, it was originally designed according to the small pond criteria, so that the above conditions are quite understandable that if a safety review is carried out based on the criteria of a large dam, there are a number of parameters that need to be adjusted accordingly. acknowledgements thank you to the faculty of engineering universitas brawijaya, which has provided research opportunities and also to the head of the pemali juana river region center, especially the operation and maintenance work unit that has supported the writing of this research. references [1] ipcc., 2007 intergovernmental panel on climate change, ipcc fourth assessment report: climate change [2] ammar rouaiguia and mohammed a. dahim, 2013. numerical modeling of slope stability analysis, international journal of engineering science and innovative technology (ijesit), issn: 2319-5967 [3] torimtubun, angelina tutulenan, 2018. analisa banjir akibat keruntuhan bendungan banyukuwung dengan menggunakan hec-ras. undergraduate thesis, universitas brawijaya. [4] anonymous, 2004. stability analysis of earth fill dams due to earthquake load. guidelines of pdt 14-2004. ministry public work and transport. [5] anonymous, 2003. guidelines inspection/evaluation dam and the guidelines for common criteria dam design, sk dirjen sda/kkb no.05 / kpts / 2003. dam safety commission. civil and environmental science journal vol. iii, no. 02, pp. 060-071, 2020 71 [6] asmaranto, r., suryono, a., & hidayat, m. 2019. inspections of hydro-geotechnical on ngancar dam. civil and environmental science journal, 2(2), pp.117-127. doi:https://doi.org/10.21776/ub.civense.2019.00202.5 [7] asmaranto, runi et.al. 2020. safety evaluation of the existing grawan dam based on hydrogeotechnical behaviour conditions to ensure the availability of water resources, published under licence by iop publishing ltd, iop conference series: earth and environmental science, volume 437, the 3rd international conference of water resources development and environmental protection 12–13 october 2019, malang https://iopscience.iop.org/article/10.1088/1755-1315/437/1/012006, [8] e fadaei kermani and g. a barani. 2012. seepage analysis through earth dam based on finite difference method, journal of basic and applied scientific research issn 2090-4304 vol 2 (11) page 11621-11625 [9] fahim ashkar and taha b. m. j. ouarda, approximate confidence intervals for quantiles of gamma and generalized gamma distributions, journal of hydrologic engineering, 10.1061/(asce)1084-0699(1998)3:1(43), 3, 1, (43-51), (1998). [10] j.r. swaisgood p.e. 2003. embankment dam deformations caused by earthquakes. colorado. usa [11] ms abhilasha p.s and t.g antony balan. 2013. numerical analysis of seepage in embankment dams, iosr journal of mechanical and civil engineering (iosr-jmce) e-issn: 2278-1684, p-issn: 2320-334x pp 13-23 [12] pr. bamane and dr.s.s.valunjkar. 2014. dam safety instrumentation, american journal of engineering research (ajer) e-issn: 2320-0847 p-issn: 2320-0936 page 58-62 [13] sosrodarsono, suyono & takeda, kensaku. 1989. bendungan type urugan. jakarta: erlangga. [14] xiaoli ding and hui qin. 1998. geotechnical instruments in structural monitoring, journal of geospatial engineering, vol. 2, no.2, pp.45-56 [15] yu zhao, zi-yhi tong and qing lu. 2014. slope stability analysis using slice-wise factor of safety, hindawi publishing corporation, mathematical problems in engineering, volume 2014, article id 712145, 6 pages. [16] virgiawan eric a, etal. 2014. analisa keruntuhan bendungan gondang dengan menggunakan program zhong xing hy21. jurnal teknik pengairan [17] harto, sri br. 2009. analisa hidrologi. yogyakarta: biro penerbit keluarga mahasiswa ugm [18] soemarto, c.d. hidrologi teknik. 1995. jakarta: erlangga