








































Georgian Geographical Journal 

 

Impact of River Flow Regulation on Deltas 
in the Black Sea Basin   
Vladimir Starodubtsev1 , Manoni Kodua2* ,Maryna Ladyka1

Vyacheslav Bogdanets3  
1 Department of Agrosphere Ecology and Environmental Control, National 
University of Life and Environmental Sciences of Ukraine, Kyiv. 
2 Department of Hydro-engineering, Georgian Technical University, Tbilisi, 
Georgia.  
3 Department of Geodesy and Cartography, National University of Life and 
Environmental Sciences of Ukraine, Kyiv 
* Corresponding author: m.kodua@gtu.ge 

 

 

 

 

 

 

 
 
 
 
 
 
 
Introduction  

Deltas, which form when rivers flow into oceans, seas, and lakes, are of great ecological and economic 
importance due to their geographical location and rich natural resources—land, water, and biological. 
However, in the last century and a half, their natural environment has been undergoing obvious 
degradation due to the construction of huge hydroelectric power plants and reservoirs and increasing 
diversion of water from rivers for irrigation, industrial, municipal, and drinking water supply, as well 
as economic development of the deltas. It is the regulation of river flow and intensive economic activity 
in their basins that lead to significant changes in the natural environment of river deltas. (Starodubtsev, 
2007) This process is becoming global but manifests itself differently, including wetlands 
desertification (Starodubtsev & Petrenko, 2005; Starodubtsev & Truskavetsky, 2011), depending on the 
climate of the region, the morphological characteristics of deltas, sediment transport, the volume of 
runoff and the nature of its regulation, and the intensity of water use and water salinity, as well as several 
other factors. The conditions in which rivers flow into bodies of water (oceans, seas, estuaries, and 
lakes) also significantly influence processes in deltas. 

The most famous in the last century were the strongest processes of degradation and desertification 
(we use this term not only for drylands but also for wetlands turning into deserts) in delta landscapes. 

The Colorado River is located on the US-Mexico border (Glenn, 1966).   Then they manifested 
themselves catastrophically in Central Asia and rapidly spread to other climatic zones around the world. 
To study these processes, large scientific schools were formed in the USA (Coleman J.M., Vorosmarty 

Georgian Geographical Journal, 2025, 5(1), 15-30 
© The Author(s) 2025 

 
This article is an open access article distributed under 
the terms and conditions of the Creative Commons 
Attribution (CC BY) license (https:// 
creativecommons.org/licenses/by/ 4.0/). 
DOI: https://journals.4science.ge/index.php/GGJ 

Abstract 
The study aimed to analyse the impacts of flow regulation and economic 
activity on river deltas in the Black Sea Basin (Rioni, Chorokhi, 
Kizilirmak, Dnieper, Dniester, and Danube). The relevance of this 
problem is because changes occurring in deltas significantly affect their 
natural resources and the prospects for their use. A comparative analysis 
of the deltas of the basin allows us to show the features and scale of 
changes occurring in them. The main methods used for this investigation 
were cartography, GIS modelling, and some field expedition routes. 
Natural conditions, delta morphology, sediment transport, flow 
discharge, and land use shape the features of delta transformation in 
these rivers. Erosion processes are observed as sediment accumulates in 
deltas exposed to coastal currents and waves (Rioni and Chorokhi in 
Georgia, Kizilirmak in Turkey). River flow regulation by reservoirs has 
reduced the flow of water into the delta and has decreased sediment 
influx. Deltas of the Dnieper and Dniester Rivers in Ukraine mostly 
depend on water releases from reservoirs. It is noticed that both the sea 
and the river influence the Danube Delta. The results obtained are useful 
for the construction and operation of infrastructure in deltas; the use of 
these areas for recreation, agriculture, and forestry; the protection of 
Ramsar wetlands; and the creation of new human settlements. 

Keywords: river delta, Black Sea basin, flow regulation, wetlands, 
coast. 

Citation: Starodubtsev, V.; Kodua, M.; 
Ladyka, M.; Bogdanets, V. Impact of River 
Flow Regulation on Deltas in the Black Sea 
Basin. Georgian Geographical Journal. 
2025, 5(1), 15-30. 
https://doi.org/10.52340/ggj.2025.05.01.03 

mailto:m.kodua@gtu.ge
https://orcid.org/0000-0002-7053-2032
https://orcid.org/0000-0002-3186-9062
https://orcid.org/0000-0002-5164-7117
https://orcid.org/0000-0003-0051-1778


Starodubtsev et al. 2025 5(1) 

 
 

C.J., Syvitski J.P.M.), in Eastern Europe and Central Asia (Mikhailov V.N., Kovda V.A., Borovsky 
V.M., Novikova N.M., etc.), as well as many prominent researchers in other regions, including in 
Georgia, Turkey, Ukraine, Romania, etc., whose works are mentioned in this message. 

In the Black Sea basin (Fig. 1), we analyse changes in river deltas flowing into the sea and subject to 
strong influence of alongshore currents and waves (Rioni and Chorokhi in Georgia, Kizilirmak and 
Yesilirmak in Turkey), deltas formed in long estuaries (Dnieper and Dniester in Ukraine), as well as 
the Danube delta, which has a more complex influence of both sea and river. 

 
Figure 1. River basins of the Black Sea: 1 – Danube, 2 – Dniester, 3 – Dnieper, 

4 – Don, 5 – Kuban, 6 – Rioni, 7 – Yesilirmak, 8 – Kizilirmak, 9 – Chorokhi 

Economic activities in river basins flowing into the Black Sea caused a decrease in water flow into 
the sea by the end of the 20th century from approximately 381 to 348 km3, and sediment from 95 to 
52.2 million m3 (Jaoshvili, 2002; Jaoshvili, 1986). And now this process is actively continuing 
(Mikhailova & Jaoshvili, 1998; Mikhailova, 2009; Berkun, 2015) causing significant changes in land 
cover in deltas. Other factors influencing the formation of landscapes in the deltas of the Black Sea 
basin are the economic development of delta plains, including recreational ones, the growth of 
settlements, and hydraulic engineering construction on the coast and in the water area. Sometimes such 
factors are even environmental protection measures in the delta itself or in the entire river basin. And, 
of course, the active erosion and accumulative activity of the water masses of the sea remains. 
Methods and Materials 

The main methods used for this investigation were cartography, GIS modelling, and some field 
expedition routes. On the eastern coast of the Black Sea within Georgia, we are considering the deltas 
of two large rivers, formed in the conditions of Mediterranean-type subtropics in the south (Chorokhi 
River) and humid subtropics in the central part of this coast (Rioni River) (Tsereteli et al., 2011). The 
Chorokhi River basin (22,100 km²) is located mostly in Turkey (91%), and only the lower part of the 
riverbed and delta (9%) are in Georgia (Fig. 2). Dams and reservoirs classify Chorokhi as highly 
regulated. In total, it is planned to build 27 hydroelectric dams with reservoirs in its basin (Fig. 3), only 
one of which is in Georgia on the Adzharistskali tributary. Under such strong regulation by dams, the 
annual flow of the river decreased from 8.71 km³ (Jaoshvili, 2002; Jaoshvili, 1986) to 6,824 km³ (Sezer, 
2009), and the sediment runoff, which amounted (Jaoshvili, 2003) to 4,920,000 m³/year (according to 
other sources, up to 5.8 million m³), decreased accordingly, but we did not find exact values in scientific 
publications. It was noted that of the total amount of sediment, 2,310,000 m³/year accumulated in the 
coastal zone, forming a delta and shelf, and 2,610,000 m³/year was carried out to the sea. It was noted 
that of the total amount of sediment, 2,310,000 m³/year accumulated in the coastal zone, forming a delta 
and shelf, and 2,610,000 m³/year was carried out to the sea. A rapid decrease in sediment runoff, visible 
even on satellite images, creates, according to many scientists (Jaoshvili, 1986; Berkun, 2015; Eruz et 
al., 2005; Hay, 1994; Mikhailova, 2009) a real threat to the ecosystems of the delta, the erosion of the 
sea edge, and the destruction of the beaches of the city of Batumi. 



Starodubtsev et al. 2025 5(1) 

 
 

Figure.2. Basin of the Chorokhi (2) and Rioni (1) rivers in winter (left, Terra satellite image) and geomorphological 
features of the delta (right, Google Earth) 

 
Figure. 3. Placement of dams and hydroelectric power stations on the Chorokhi River 

(Berkun et al., 2015) 

Indeed, the southern and southeastern coast of the Black Sea is characterized by the development of 
erosion and coastal retreat under the influence of regulation of river flow and sediment accumulation in 
reservoirs (Berkun, 2015; Hay, 1994; Klaphake & Waltina, 2011; Mikhailova & Jaoshvili, 1998). The 
manifestation of this process in the Chorokhi River basin and the interaction of land and sea in the 
Chorokhi delta area became the subject of our research using remote sensing methods. At the first stage 
of the study, high-quality Landsat-5 and 8 images were used for the period 1980-2015 (Starodubtsev, 
2014; Starodubtsev & Basarab , 2017a). And at the second stage, the entire period of operation of the 
Landsat 2, 4-5, 8, 9 satellites for 1975-2024 is considered, but these materials have not yet been fully 
analysed. 

 
Figure 4.  Sediment input into the Chorokhi River delta in 1987 (left) and 2015 (right) 



Starodubtsev et al. 2025 5(1) 

 
 

Visualization and classification of images (Fig. 5) made it possible to approximately assess the 
processes of some drainage of this delta territory due to the regulation of the river flow and the 
intensification of its economic development. Thus, over the entire territory of 3,730 hectares, the area 
of water surface decreased from 303 to 251 hectares, the area of wetlands decreased from 594 to 237 
hectares, but the area of gardens and meadows increased noticeably - from 487 to 921 hectares. The 
area of forests and built-up areas has not changed significantly. 

 
Figure 5. The Chorokhi River delta in Landsat 5 (1987) and Landsat 8 (2015) 
images and their classification: 1 - water surface, 2 - buildings, 3 - impervious 

areas, 4 - wetlands, 5 - forests and parks, 6 - meadows and gardens. 

To determine changes in the shoreline of the delta, a shapefile of this delta in the Landsat-8 image in 
2015 was superimposed on the Landsat-5 image in 1987. The results indicate the retreat of the 
coastline—that is, coastal erosion— in the river mouth and in the area between the mouth and the city 
of Batumi. Considering the approximate nature of the values obtained in this way, we note that in the 
river mouth the coastline shifted to the east over the period 1987-2015 by 120-150 m, and in the area 
between the mouth of the river and the city of Batumi these values were -60-90 m, respectively. Within 
the city of Batumi itself, the coastline displacement was mostly less than 1 pixel (30 m) and in a westerly 
direction. That is, a weak tendency towards sediment accumulation appeared here. This value was 
clarified using the Planet Earth mapping service (Fig. 6). For this purpose, the function of this service, 
“change of image over time”, was used, which made it possible to approximately identify the 
displacement of the coastline towards the sea for the period 2004-2016, amounting to 10-35 m. The 
same trend of increasing the width of the beach coast in Batumi was confirmed in 2018 and then in 
2024. 

To determine specific territories where changes occurred, as well as their areas, the “change detection” 
function of a specialised program was used (Fig. 7). As a result, it was revealed that in the area of the 
mouth of the Chorokhi River, during the period from 1987 to 2015, The areas that most protruded into 
the sea, covering an area of 14 hectares, were eroded, while at the same time, part of the sediments 
formed as a result of erosion of the riverbed accumulated at the mouth. In the area from the river mouth 
to the city of Batumi, a one-way directional process of bank erosion was noted over an area of 16 
hectares. In the area of the city of Batumi itself, sediment accumulation occurred on an area of 20.5 
hectares and the coast extended tens of meters into the sea. Sediment accumulation was also noted north 
of Batumi (in the bay). 



Starodubtsev et al. 2025 5(1) 

 
 

 

Figure 6. Changes in the coastline in the city of Batumi for the period 2004-2018  

To ensure the reliability of the data obtained, an attempt was made to analyse images of the Landsat 
space satellites for the entire period of their operation, that is, from 1976 to 2024. However, the images 
for the period 1976-1986 were of low quality, so the results obtained will be refined. Nevertheless, we 
present them in this message. In the city of Batumi for the period 1976-2000 the increase in the beach 
coast was 45 m over the period 2000-2024 - another 30 m, and in total for 1976-2024 - 75 m. In the 
middle of the space between the mouth of the Chorokhi River and Batumi, due to erosion, the coastline 
retreated to the east in 1976-2000 by 75 m, in 2000-2024 - by 50 m, and in total for 1976-2024 - by 125 
m. At the same time, at the very mouth of Chorokhi, the processes of erosion and accumulation 
alternated in years of different water content. 

 
Figure 7. Changes in the coastline in the Chorokhi River delta for the period 1987-2016 

Results 
Rioni estuaries 

The Rioni River is located in Georgia and has a length of 327 km, and a drainage area of 13,400 km2. 
It begins in the Caucasus Mountains, and below the city of Kutaisi it flows through the fertile Colchis 
lowland with a humid subtropical climate (Fig.8) and flows into the Black Sea near the city of Poti. The 
annual volume of water flow is estimated at 13.37 km3, including 9.62 km3 of water flowing along the 
northern (new) channel, and 3.75 km3 of water flowing through the southern channel (Jaoshvili, 2002). 
The flow of the Rioni is regulated by a cascade of small hydroelectric power stations (Lajanuri, Gumati 
1 and 2, Rioni Vartsikhe hydroelectric power stations), but due to the small volume of reservoirs, they 
did not have a significant impact on the river’s water flow. Important changes in flow occurred when 
in 1939 the mouth of the Rioni was artificially diverted north of the city of Poti to protect it from floods, 
and in 1959 part of the river's flow was returned to the old channel (Fig. 8). The river's water resources 
are used mainly for energy, water supply and irrigation. 



Starodubtsev et al. 2025 5(1) 

 
 

 
Figure 8. Artificial direction of the Rioni flow along the northern channel - left and changes in processes on the coast in 

connection with the creation of a new port (Saghinadze et al et., 2024) 

The formation of the area between the old and new channels of the Rioni River (Rioni delta) is also 
significantly influenced by modern changes in the sediment flow of the river (3.54 million tonnes per 
year) and along-shore sediment flows of the Black Sea. The natural dynamics of sediment in the river 
were changed due to flow regulation, but after the reservoirs were filled with sediment, their flow began 
to return to the natural state (Jaoshvili, 2002). The direction of the river flow in 1939 along the northern 
channel to protect the city of Poti from floods had a dramatic effect on the influx of sediment at the 
mouth of the Rioni. As a result, the urban area began to be eroded, so part of the river flow was again 
returned to the old channel. In 1939, the direction of the river flow along the northern channel had a 
dramatic effect on the influx of sediment at the mouth of the Rioni, protecting the city of Poti from 
floods. As a result, the urban area began to be eroded, so part of the river flow was again returned to 
the old channel. And in the northern channel, the bank began to grow. The creation of the delta area 
here and how the river and sea interact were mostly influenced by the movement of sediment along the 
shore towards the centre of Colchic Lowland. But with the transfer of the Rioni flow along the northern 
channel, the growth of the coast here led to a shift in the sediment flow to the north (Fig. 9). 

 
Figure 9.  Sediment movement near the coast of Rioni delta (Sentinel-2, 2024-06-02) 

And the process of sediment accumulation between the mouths of the Rioni and Khobi rivers has 
intensified in recent decades in connection with the reconstruction of port facilities here and has led to 
further growth of the coast. It is this process that we studied using modelling methods and remote 
sensing. 

The remote sensing technique for the case of Rioni was based on a comparison of Landsat 2, 5 and 8 
satellite images for the period 1975-2016. To compare images from different years, a shapefile (aoi) 
was created on the 2016 image. It was superimposed sequentially on images from 1975, 1980, 1987, 
2000 and 2009, which made it possible to identify an area of the sea that was gradually replaced by land 
due to sediment accumulation (Fig. 10). Now such research continues for the period until 2024 using 



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the “change detection” computer technique. The landscapes of the Rioni delta were analysed using 
“unsupervised classification”. The calculation of land and water surface areas within the study area 
(2943 hectares) showed that the size of the land for the period 1975–2016 increased by 366 hectares 
(Table 1). That is, the rate of land growth during this period averaged 8.93 hectares per year (according 
to modelling data, land growth towards the sea was 7-8 m/year). It is important to note that in recent 
decades the rate of land growth has slowed to 6-7 hectares/year.  

  
Figure 10. Changes in the delta coastline for 1975-2016 

New lands formed in the coast of the delta are mainly a recreational resource. But it is also important 
to assess changes in land cover throughout the delta, which serves as a resource for agricultural 
production, environmental protection measures and the development of the city of Poti with all its 
infrastructure. Considering the low quality of Landsat-2 images, the assessment of changes in the 
structure of land cover was made only using the Landsat-5 and 8 satellites for the period 1987-2016 
(Fig.11).    

Table 1. Changes in the structure of land cover of the Rioni delta within the 
boundaries of the studied territory for the period 1987-2016, ha 

Land 
 

Land area, ha Сhanges in area, ha 
 1987 2016 

Water surface 566 386 -180 
Buildings (residential, 
communal, industrial) 

668 737 +69 

Landscape gardening 587 632 +45 
Forests (including 
floodplains) 

490 682 +192 

Wet meadows with shrubs 399 279 -120 
Wetlands 233 227 -6 
Total 2943 2943 _ 

 
In general, changes in the land cover of deltaic region of the Rioni River are due to the redistribution 

of river flow into the northern and southern channels, alongshore sediment flows into the sea and, to a 
lesser extent, regulation of flow by dams and reservoirs. A study of the dynamics of the delta in time 
and space based on remote sensing data from Landsat satellites showed that for the period from 1975 
to 2016. The area of the part of the delta we studied increased by 366 hectares, and the average rate of 
its increase was 8.93 hectares/year. The protrusion of the delta into the sea occurs in the northern and 
middle part of this region, in the southern part (the city of Poti) the coastline is now relatively stable 
with tendency to erosion, and to the south there is coastal erosion. The obtained parameters for the 
increase in the Rioni delta can be used for forecasting for the coming years, especially in connection 



Starodubtsev et al. 2025 5(1) 

 
 

with the construction of a new port. The new lands formed in the delta of the Rioni River are mainly a 
recreational resource. But throughout the delta there is an improvement in the agro-ecological condition 
of the lands, which serve as a resource for the development of the region. 
 

 
Figure 11. Changes in the structure of land cover in the Rioni River delta. (In both legends: 1 - water 

surface, 2 - wetlands, 3 - wet meadows. In the legend for the 1987 image: 4 - buildings, 5 - gardens and 
parks, 6 - forests. In the legend for the 2016 image.: 4, 5 and 8 – individual, communal and industrial 

buildings, 6 – landscape gardening, 7 – forests 

    Delta of the Kizilirmak River 
 River deltas on the southern coast of the Black Sea (within Turkey) are formed both under flow 

regulation by dams and reservoirs and under the influence of powerful waves and latitudinal longshore 
currents. The largest river here is the Kizilirmak, whose delta is of international importance as a wetland 
for waterfowl habitat. Farmland, including irrigated fields and fruit plantations, occupies the flat areas. 
The length of the river is 1355 km, and the drainage area is 78646 km² (Jaoshvili, 2002). It originates 
in the mountains in inland Anatolia; in its lower reaches, it cuts into a plateau to a depth of about 600 
m and flows into the sea on a swampy plain near the city of Bafra. The river mouth has formed an 
underwater sandbar (Jaoshvili, 2002), which influences the modern processes of coastal erosion. 

The modern delta, which is a plain dotted with a network of channels and canals, was formed over a 
period of about 10,000 years (Erdoğan, 1970). It lies at altitudes of 0-15 m and ends in a swampy 
lowland with lagoons, bordered by dunes. Today, most of the delta is used for agricultural production, 
including rice growing. And behind the barrier of sand dunes, the configuration of which was 
determined by the interaction of the influx of river sediments and alongshore sea currents, lagoons were 
formed that have unique environmental value (Erdoğan, 1970). 

Our research includes an analytical review of published materials on the problem of degradation of 
delta wetlands, as well as an analysis of temporal and spatial changes in the Kizilirmak River delta 
based on Landsat satellite images for 1980–2016 and then until 2024. Big changes in the land cover of 
the delta happen because of 1) erosion and buildup of materials on the sea coast (Algan et al., 2000; 
Hay, 1994); 2) less river water and sediment flowing into the delta, which harms the wetland areas; 3) 
different ways the land is used (like for irrigation, farming, grazing, and protecting wetlands). Erosion-
accumulation processes on the sea coast depend on the wave activity of the sea and along-shore currents, 
on the one hand, and the accumulation of river sediments, on the other. In the Kizilirmak delta, the 
amount of river sediment coming in dropped significantly after the Altynkaya and Derbent reservoirs 
were built nearby (Fig. 12). And the activity in the sea (winds, waves, currents) remained almost the 
same. Therefore, we compared the delta coastline in 2010 and 1980, that is, over 3 decades, as well as 
in 2014 (Fig. 13). 



Starodubtsev et al. 2025 5(1) 

 
 

 
Figure 12. The Kizilirmak River delta before and after the construction of reservoirs 

in the lower reaches and straightening of the riverbed (Landsat images 2 and 8) 

And the activity of the sea (winds, waves, currents) remained almost the same (Fig. 13). Therefore, 
we compared the delta coastline in 2010 and 1980, that is, over 3 decades, as well as in 2014 (Fig. 13). 
An approximate graphical assessment of changes in the coastline for the period 1980-2010. showed that 
the western coast (Fig. 13, site 4) has changed little. Erosion here appeared at a distance of 0-60 m, that 
is, within one pixel on the raster image. Erosion was more severe to the east of the river mouth (Fig. 
13, site 1), spreading here over a distance from 60-120 m to 360-420 m (6-7 pixels). At the same time, 
on the eastern coast, areas of sediment accumulation were identified, where the sea retreated by 120-
240 m (site 2) and from 120-180 to 240-360 m (Fig. 13, site 3). We compared these results with data 
from (Ozturk et al., 2015), according to which coastal erosion east of the river mouth amounted to 655 
m. Moreover, special spurs (Fig. 14) weaken erosion processes here, but do not prevent them 
completely. 

 
Figure 13. Changes in the delta coastline for the period 1980-2010 (1, 4 – erosion; 2, 3 - accumulation) 

Conclusions: a) Reduced water and sediment flow into the Kizilirmak River delta and economic 
activities in it have caused noticeable changes in land cover; b) The interaction of land and sea in 
conditions of a decrease in the influx of river sediments caused the activation of erosion-accumulation 
processes in the delta. Wave activity and alongshore currents caused coastal erosion mainly east of the 
river mouth and local accumulation of sediment on the east coast; c) The water surface of lakes and 
estuaries in the delta has decreased by 1-2 thousand hectares over a 30-year period due to the 
transformation of water bodies into wetlands. Quantitative indicators of the decrease in wetlands in the 
Kizilirmak Teka delta need to be clarified by further monitoring. 

Dnieper delta 
The Dnieper River flows through the territory of three countries - Ukraine, Belarus and Russia. The 

total area of the basin is 504 thousand km2, of which: 20% is in the Russian Federation, 23% - in the 
Republic of Belarus, and 57% (296,317 thousand km2) - within Ukraine. The total length of the Dnieper 
is 2,201 km, within Ukraine – 1,121 km (Vishnevsky, 2011). Before the war between the Russian 
Federation and Ukraine, more than 20 million people lived in the Ukrainian part of the Dnieper basin, 



Starodubtsev et al. 2025 5(1) 

 
 

but now this number has significantly decreased. The plowed area of the basin is 69% of its total area, 
that is, it is quite high. 

 
Figure 14. Protection of the banks from erosion east of the mouth of the Kizilirmak River with special spurs 

created in 1999-2010 (Sentinel-2)  

The degree of regulation of the flow of the Dnipro is very high. The river is regulated by a cascade of 
Dnieper reservoirs – Kyiv (previously – Kiev), Kaniv, Kremenchuk, Kamianske (previously - 
Dniprodzerzhynsk), Dnipro, Kakhovka (destroyed on 6 June 2023). Regulation of the Dnieper flow 
began back in 1932 with the construction of the Dnieper hydroelectric power station, but this did not 
noticeably affect the landscapes of the river delta. More significant changes in the water regime of the 
delta and its ecosystems began in 1956-1957, when the large Kakhovka reservoir, created for irrigation, 
energy, water supply and water transport, was filled. And then, until 1975, a whole cascade of 6 
reservoirs was created with a total volume of 43.8 km3, a useful volume of 18.5 km3 and an area of 
about 7000 km2. During the same period, large canals were built that drain water from the Dnieper 
(North Crimean, Kakhovsky, Dnieper-Donbass, Dnieper-Ingulets, Dnieper – Kryvy Rig), and the 
consumption of Dnieper water for municipal, industrial and agricultural water supply increased.   The 
total area of the water in the reservoirs of the cascade is about 7,000 km2 with a total water volume of 
43.71 km3 and useful volume of 18.5 km3. There are some large canals that divert water from the 
Dnieper River: The Dnipro-Donbas canal, the Kakhovsky main canal, the North-Crimean canal, the 
Dnipro-Kryvyi Rih canal and the Dnipro-Ingulets canal.  

 
Figure 15. Deltas of the north-western coast of the Black Sea (1 – Dnieper, 2 – Dniester, 3 – Danube) Results 

 

The average long-term rate of the natural flow of the Dnieper previously increased downstream from 
593 m3/s at the "Nedanchichi" hydropost (the entry point for the territory of Ukraine) to 1,690 m3/s at 
the mouth of the Dnieper. Now the flow rates are fully regulated by the reservoirs and in the last decade, 
which was low-water, amounted to 500-600 m3/s. Average long-term natural volume of runoff in the 
estuary was 53.3 km3, and now it has decreased by approximately 11 km3, that is, it has become 20% 
less than the natural one. Inflow of sediments during this period also decreased from 2.6 to 0.6-0.8 
million t/year, as they now accumulate mainly in the upper (Kyiv) reservoir. It is important to note that 



Starodubtsev et al. 2025 5(1) 

 
 

at the top of all reservoirs of the cascade, except for the deep and narrow Dnieper one, peculiar delta-
like hydromorphic landscapes began to form due to the accumulation of solid runoff, organic sediments 
and the development of wetland vegetation and floodplain forests. However, this process is still at the 
initial stage due to the small amount of solid runoff from the Dnieper in comparison, for example, with 
the formation of a new delta in the Kapchagai Reservoir on the Ili River in Kazakhstan, where the solid 
runoff exceeds 11 million tons per year (Starodubtsev, 2007c). The most active process of such delta-
like landscapes formation takes place in the Kyiv Reservoir, the first in the cascade, which accumulates 
almost the entire solid runoff of the Dnieper - on an area of about 20000 ha. It continues in the large 
Kremenchutsk and Kakhovka reservoirs, and only fragmentarily in the small Kaniv and Kamianske 
reservoirs. These new landscapes have a very large significance for biodiversity, nature protection, 
recreation, hunting, sport, etc. 

 
Figure 16. Dnieper Delta before flooding (2023-06-03) 

 
Figure 17. The Dnieper Delta is flooded on the 4th day (2023-06-09) 

The Dnieper Delta is formed in a narrow long canyon and ends with the Dnieper-Bug estuary on the 
Black Sea coast. It begins near the village of Oleshki, stretches for more than 42 km and ends in the 
Dnipro-Buzka estuary. The total area of the delta is estimated at approximately 350 square kilometers. 
This area is very rich in biodiversity, so it is included in the list of wetlands of international importance 
protected by the Ramsar Convention. Before the construction of a cascade of dams and reservoirs, the 
delta gradually grew in the estuary towards the Black Sea, representing a collection of numerous 
channels, lakes, islands, swamps overgrown with reeds, and weakly expressed ramparts with shrub and 
tree vegetation. However, after a flow regulation the influx of water and sediment into the delta has 
decreased, water quality has deteriorated, and powerful flood spills, which now occur only in record-
high water years, have practically ceased. The restructuring of landscapes began, accumulative 
processes and the protrusion of the delta into the Dnieper-Bug estuary noticeably weakened. Stagnation 
processes, eutrophication of lakes and streams increased. The massive construction of country houses 
on the levees along the large straits greatly contributed to the processes of eutrophication. 

Our research is carried out in the contour from the Antonovsky automobile bridge across the Dnieper 
River to the estuary on an area of 37.4 thousand hectares. Schematic zoning of the delta based on 
ground-based route studies and analysis of Landsat satellite images for the period 1975-2013. made it 
possible to identify areas with different intensity of overgrowing of water bodies with hydrophylic and 
hydrophytic vegetation, “blooming” of water, and areas of economic use. However, in recent years, 
there has been a noticeable lack of water on the Dnieper and a decrease in water flows from the 



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Kakhovka reservoir to the delta, reaching 300-500 m3/s in certain periods. This led to an intensification 
of the processes of overgrowing the delta with coastal aquatic vegetation and a significant increase in 
the areas of floodplains with trees and shrubs. The area of settlements, dachas and anthropogenically 
modified territories is also noticeably increasing, reaching more than 4 thousand hectares in 2015. The 
“blooming” of water in the estuaries and lakes of the delta has also increased. Such trends persisted 
until 2021, after which changes were caused by the war in Ukraine. 

 
Figure 18. Dnieper Delta on the 12th day after flooding with destroyed vegetation and covered 

As the delta changes, the likelihood of fires increases, destroying all unique biota. Thus, in the spring 
of 2016, the consequences of large fires that occurred in the autumn-winter period were revealed. The 
area of the fires amounted to more than 5 thousand hectares, of which on an area of 2.8 thousand 
hectares the vegetation was completely burned out, including trees and shrubs, and on an area of 2.2 
thousand hectares - partially. Since 2022, with the outbreak of the war, the area of fires in the territories 
adjacent to the delta has sharply increased due to shelling and bombing. 

 
Figure 19. Gradual restoration of delta wetlands after 3 months with traces of fires from artillery 

Profound changes in the Dnieper delta occurred after the destruction of the dam and power station of 
the Kakhovka reservoir on June 6, 2023. These changes are shown at these satellite images (Fig16-19): 

 
Figure 20.  Delta of the Danube River (Landsat-5) 



Starodubtsev et al. 2025 5(1) 

 
 

Danube Delta. 
The Danube River is the second largest river in Europe with a catchment area of 817,000 km². The 

Danube basin covers the territory of 18 countries, the largest parts of the basin are in Romania (28.9% 
of the area), Hungary - 11.7%, Austria - 10.3%, Serbia - 10.3%. The length of the river is 2857 km. The 
average annual flow of the Danube is, according to various estimates, from 203 to 210 billion m3 (57% 
of the annual flow of all rivers flowing into the Black Sea), and the average flow rate is 6500 m3/s. 
Sediment runoff in its natural state was approximately 56-83 million tons every year, but under the 
influence of economic activity (water regulation and water use) it has significantly decreased (Fig. 20). 

 
Figure 21. Our field routs in the Ukrainian part of the Danube delta 

The source of the Danube is in the mountains in Germany, and then it flows along the Middle Danube 
lowland to the "Iron Gate" gorge in the south of the Carpathians and on to the Black Sea. The importance 
of the Danube basin for the European economy is extremely high. When it flows into the Black Sea, 
the Danube forms a giant delta with an area of 5640 km². The top of the delta is near Cape Izmailsky 
Chatal, 80 km from the mouth. Here, the main channel of the Danube first branches into the Kiliy 
estuary, which flows into the sea on the territory of Ukraine, and the Tulchyn estuary, which 17 km 
downstream divides into the Georgievske and Sulinske estuaries, which flow into the Black Sea in 
Romania. Floodplains, with a multitude of canals, lakes, and marshes, primarily cover the area. The 
delta was quickly pushed into the sea by a large amount of sediment before the flow of the Danube was 
intensively regulated by reservoirs, especially on its numerous tributaries. However, due to hydraulic 
construction in the basin and the ever-increasing use of Danube water in its economy, the total flow of 
water and especially sediment is significantly reduced. Thus, the delta's advance into the sea has slowed, 
and the processes of accumulation and erosion of the delta's sea edge are clear. A cross-border biosphere 
reserve, "Danube Delta," has been created in the Danube Delta and is included in the World Network 
of Biosphere Reserves. It includes the 580,000 ha Danube Delta Biosphere Reserve in Romania and the 
Danube Biosphere Reserve in Ukraine.  

For now, our research is focused mainly on the Ukrainian part of the delta, where the process of the 
delta's extension into the sea continues), which, however, becomes more complicated from year to year 
depending on the water level of the year and the peculiarities of the influence of sea currents and waves. 
In general, our preliminary calculations (Starodubtsev, 2013)indicate that in the Danube delta, the area 
of the water surface decreases by an average of 500 ha each year due to the overgrowth of lakes and 
channels with air-water and water vegetation, economic development of land, and partly due to the 
increase in the area of the Chiliya part of the delta, which we explored by land routes (Fig.21). 

The state of wetlands and their gradual agricultural development, especially in the northwestern part, 
significantly affects the state of wetlands. As for the sea edge of the Danube delta, it changes depending 
on the inflow of sediments and the influence of sea currents and waves. In the north-eastern and central 
parts of the delta, the delta is moving slowly into the sea, that is, mineral and organic sediments are 
accumulating and the area of the delta is increasing, especially its Ukrainian part. And in the 
northeastern part of the delta, erosion and erosion of the shore prevail. 



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A very serious problem for the biodiversity of the huge delta is the frequent and large-scale fires that 
occur due to natural phenomena, but to a greater extent due to the irresponsible (and sometimes 
intentional) actions of poachers and even the personnel of the biosphere reserve (Fig.22). 

Such fires cause great damage both to the unique colonies of migratory birds and to all species of the 
delta's animal world. Fires cause irreparable damage to floodplain forests and shrubs, which take an 
immeasurably longer time (years) to regenerate compared to grassy vegetation. 

 
Figure 22. Fires in the northeastern part of the Danube Delta (Sentined-2 satellite images) 

Conclusion 
The way river flow regulation affects river deltas, and the local economy varies based on the climate, 

landforms, how the flow is managed, and other natural characteristics of the delta area. In the Black Sea 
basin, it's easy to see that changes in the deltas are mainly influenced by how they interact with the sea. 
In the Black Sea basin, changes in the deltas can be clearly traced, primarily depending on how they 
interact with the sea. On the Caucasian coast, deltas experience the influence of alongshore flows of sea 
water and sediments from the north, leading to coastal erosion at river mouths and sediment 
accumulation north of these mouths. Therefore, the erosion of the recreational zone (beach) in Batumi 
remains a topic of discussion now. Erosion processes are also taking place in the southern part of Poti 
city, but sediments are actively accumulating in the middle and northern parts of the coast. And their 
accumulation can create problems for the infrastructure under construction, around the new Port. 

The deltas of the rivers on the Turkish coast, particularly the Kizilirmak River, are strongly influenced 
by the alongshore currents in the eastern direction. Their western shores have already formed high dune 
formations that slow down erosion processes. But in the mouths of rivers and on the eastern shores, 
turbulent flows intensively erode the shores, so special protective structures are already being built here 
to protect against erosion, although they do not fully protect against it. It is important to note that the 
circulating water flows along the eastern shore form alternating areas of erosion and sediment 
accumulation. 

And this affects personally valuable extensive wetlands and the infrastructure of the coast occupied 
by recreational organisations and settlements. 

Regulation of the flow of the rivers along the Caucasian and Turkish coasts in general optimises the 
water regime of the deltas and promotes their effective use in agriculture, horticulture, and recreation. 
However, we need to take measures to protect the valuable Ramsar wetlands. 

Long estuaries form the deltas of the northern coast of the sea (Dnieper, Dniester), which do not 
interact with the sea. Therefore, their landscapes have sharply slowed their advance toward the sea and 
are experiencing stagnant phenomena. To optimise the water regime of ecosystems and support 



Starodubtsev et al. 2025 5(1) 

 
 

fisheries, they need spring flushing releases from reservoirs. They currently face the devastating effects 
of war. 

Both the river and the sea influence the Danube Delta. On a huge area of wetlands, there is a tendency 
to decrease the area under water (lakes, channels) and increase under vegetation at a rate of about 500 
hectares per hour. The northwestern part of the delta is being developed for agriculture. On the seacoast 
of the delta, mineral and organic deposits mainly accumulate in the northern (Ukrainian) and middle 
parts, but erosion occurs in the southern part. 
Competing interests 

The authors declare that they have no competing interests. 
Authors’ contribution 

V.S. made the biggest contribution, conceived of the presented idea, and took the lead in writing the 
manuscript. M. K. characterized Chorokhi and Rioni deltas. M. L. characterized Dnieper and Danube 
deltas.  V. B. performed the cartographic part. All authors provided critical feedback and helped shape 
the research, analysis, and manuscript.  

ORCID iD 

Vladimir Starodubtsev https://orcid.org/0000-0002-7053-2032 
Manoni Kodua https://orcid.org/0000-0002-3186-9062 
Maryna Ladyka https://orcid.org/0000-0002-5164-7117 
Vyacheslav Bogdanets https://orcid.org/0000-0003-0051-1778 

Reference 
Bayram, A., & Kenanoglu, M. (2016). Variation of total suspended solids versus turbidity and Secchi disk depth 

in the Borçka Dam Reservoir, Çoruh River Basin. Lake Reserv Manag, Vol 32, 209-221. 

Berkun, M., Aras E., & Akdemir, U. O. (2015). Water runoff, sediment transport and related impacts in the 
southeastern Black Sea rivers. Environmental Engineering and Management Journal, 14(4), 781-791. 

Erdoğan, A. (1970). Geomorphology of the Kızılırmak Valley: Between Bafra Burnu and Delice Junction. 
Ankara: Ankara Üniversitesi Basımevi. 

Eruz, C., Kose, E., Guneroglu, A., Basar, E., Sivri, N., Feyzioglu, A. M., & Toraman, C. (2005). Suspended 
Solids Dynamics in the Eastern Black Sea rivers (in Turkish). Turk Sucul Yasam Dergisi, 4, 235-239. 

Gagoshidze, Sh,, Kodua, M., Saghinadze, I., & Kadaria, I. (2017). River hydro construction and 
geomorphological processes in the Black Sea coast of Georgia. Tbilisi: 1st ed. Technical University.  

Glenn, E.P., Lee C., Felger, R., & Zengel, S. (1966). Effect of water management on the wetlands of the 
Colorado River delta. Conservation Biology 10(4), 1175-1186. 

Hay, B. J. (1994). Sediment and water discharge rates of Turkish Black Sea rivers before and after hydropower 
dam construction. Environmental Geology, 23, 276-283. 

Jaoshvili, Sh. (1986). Rivers of the Black Sea (In Russian). Tbilisi: Sabtchota Sakartvelo. 

Jaoshvili, Sh. (2002). The rivers of the Black Sea. Technical reports 71. Kopenhagen: European Environment 
Agency, 1-58. 

Kiknadze, A. G. (1976). Dynamic systems and sediment budget in streams along the Black Sea coast of 
Georgia. In Dynamics of seacoasts (In Russian) (pp. 68–70). Tbilisi: Metsniereba. 

Klaphake, A., & Scheumann, W. (2011). Coruh River Basin: Hydropower development and transboundary 
cooperation. In Springer eBooks (pp. 251–261). https://doi.org/10.1007/978-3-642-19636-2_14. 

Makatsaria, A. (1973). Causes and possible measures to eliminate coastal erosion near the city of Poti. Works of 
Geographer Communities of Georgia. Tbilisi: Metsniereba. 

Mikhailova, M, V. (2009). Water and sediment runoff at the mouths of rivers flowing into the Black Sea. 
Environmental Research. Engineering and Management, Vol. 48, 5-10. 

Mikhailova, M. V., & Jaoshvili, Sh. V. (1998). Hydrology-morphological processes in the mouth area of the 
Rioni and their anthropogenic change (In Russian). Water Resources, Vol. 25, 152-160. 

Ozturk, D., Beyazit, I., & Kilic, F. (2015). Spatiotemporal Analysis of Shoreline Changes of the Kizilirmak 
Delta. Journal of Coastal Research 31(6), 1389-1402. doi: https://doi.org/10.2112/JCOASTRES-D-14-
00159.1 

https://orcid.org/0000-0002-7053-2032
https://orcid.org/0000-0002-3186-9062
https://orcid.org/0000-0002-5164-7117
https://orcid.org/0000-0003-0051-1778
https://orcid.org/0000-0002-7053-2032
https://orcid.org/0000-0002-3186-9062
https://orcid.org/0000-0002-5164-7117
https://orcid.org/0000-0003-0051-1778


Starodubtsev et al. 2025 5(1) 

 
 

Saghinadze, I. (2013). Calculation of the coastal currents of the Black Sea in the area of Poti. Journal of 
Georgian Engineering News, 2(66), 101-104. 

Saghinadze, I., & Kodua, M. (2019). A Mathematical Model of Sediment Transport of the Poti Coastal Zone. 
International Journal of Engineering Research and Technology, 12(12), 3032-3037. 

Saghinadze, I., Kodua, M., & Pkhakadze, M. (2024). The Influence of the New Breakwater of Poti Port on 
Litho-dynamics of the Coastline. International Journal of Engineering Trends and Technology 72(5), 227-
231. 

Sezer, U. (2009). Coruh river development plan. International Workshop on Transboundary Water Resources 
Management. Tbilisi: KS (DSI). 

Starodubtsev V. M. (2013). Changes in the Danube Delta According to Remote Sensing Data by Landsat 
Satellite. Arid Ecosystems, 4(3), 258-262. 

Starodubtsev V, M. (2014). Flow regulation impact on land cover changes in river deltas of the Black Sea basin. 
Retrieved from http://www.sworld.com.ua/index.php/ru/conference/the-content-of-conferences/archives-
of-individual-conferences/june-20 

Starodubtsev V, M., & Petrenko, L. R. (2005). Soil desertification in the river deltas (Part 1). Kyiv: Nora-Druk. 

Starodubtsev V, M., & Truskavetsky S, R. (2011). Desertification processes in the Ili River delta under 
anthropogenic pressure. Water Resources, 38, 253-256. 

Starodubtsev, V. M. (2007). Degradation Processes in Deltas of the Rivers with Flow Regulation. Basin Water 
Management. Intern. Congress on River Basin Management, 828-843. Retrieved from 
http://www2.dsi.gov.tr/english/congress2007/chapter2/66.pdf 

Starodubtsev, V. M. (2017). Changes in land cover in the Rioni River delta. Scientific World, 49, 98-108. 
Retrieved from http://www.sworld.education/ntsw/49-2.pdf 

Starodubtsev, V. M., & Basarab R, M. (2017). Changes in the Chorokhi River delta under the influence of 
economic activity. Scientific works of SWorld, 2(48), 106-115.  

Starodubtsev, V. M., & Rudchenko L, M. (2017a). Changes in land cover of the Kizilirmak River delta. SWorld 
Journal. Retrieved from http://wwww.sworld.education/index.php/ru/geography-ua217/physical-
economic-and-social-geography-ua217/29304-ua217-047. 

Starodubtsev, V. M., & Rudchenko, L. M. (2017b). Changes in land cover of the Yeshilirmak river delta. 
Bioresources and environmental management. NUBiP of Ukraine, 9(3-4), 8. Retrieved from 
http://journals.nubip.edu.ua/index.php/Bio/article/view/8986/8262 

Starodubtsev, V. M., & Struk, V. (2013). Danube delta: view from space. Kherson: Oldi plus. 

Tsereteli, E., Gobejishvili, R., Bolashvili, N., Geladze, V., & Gaprindashvili, G. (2011). Crisis intensification of 
Geoecological Situation of The Caucasus Black Sea Coast and The Strategy of Risk Reduction. Procedia - 
Social and Behavioral Sciences, 19, 709-715. https://doi.org/10.1016/j.sbspro.2011.05.189 

 


