AMQ70 Luberti et al Vergari ProofCopy 3b doi Available online http://amq.aiqua.it ISSN (print): 2279-7327, ISSN (online): 2279-7335 Alpine and Mediterranean Quaternary, 31 (2), 2018, 119 - 132 ANTHROPOGENIC MODIFICATIONS TO THE DRAINAGE NETWORK OF ROME (ITALY): THE CASE STUDY OF THE AQUA MARIANA Gian Marco Luberti 1, Francesca Vergari 2, Roberta Marini 2, Alessia Pica 2, Maurizio Del Monte 2 1 Istituto Superiore per la Protezione e la Ricerca Ambientale, Italy 2 Dipartimento di Scienze della Terra, Sapienza Università di Roma, Italy Corresponding author: F. Vergari ABSTRACT: Rome is characterized by millennia of urbanization. Long lasting geomorphological investigations have allowed the geomorphological description of the city centre and the valorisation of its geomorphological heritage. In this paper the spatial change of the hydrographic network in historical times is illustrated, with some examples showing how deep has been, and still it is, the link between the historical-cultural development and the natural geomorphological and hydrological characteristics of the Roman territory. In particular, the most relevant human interventions on the drainage network, in the southern area of the city cen- tre, have been investigated. Before the land-use modifications of Roman-age, this area was drained by the most important left tributary of the Tiber River within the city walls, the Nodicus River, more recently known as Aqua Mariana. This stream has under- gone many anthropogenic modifications and diversions during the centuries, and its original path is known only downstream of the San Giovanni Basilica. According to geomorphological, archaeological and geological evidences, it is possible to hypothesize that the dimension of the pre-urbanization drainage basin, as known and reconstructed in the available literature, should have been until now underestimated. Keywords: Rome (Italy), urban geomorphology, urban landscape, Tiber River, Aqua Mariana, Nodicus River 1. INTRODUCTION The history and cultural heritage of Rome are well known all over the world. Not so its geo-environmental heritage, which is also very important and has guided the initial settlement choices and the subsequent growth of one of the most important cities for the development of civilization. Although many geomorphological features have been hidden or completely eliminated during millennial urbanization processes, the landscape of Rome still preserves the main landforms of the original physical landscape. After a general description of the geo-environ- mental characteristics of the area corresponding to the historical centre of the Urbs and the lower Tiber Valley, to the neighbouring coastal belt, the historical spatial changes of the hydrographic network are illustrated in more detail. By some examples we demonstrate how deep has been, and still it is, the link between the his- torical-cultural development and the natural geomor- phological and hydrological characteristics of the Ro- man territory. In this paper, we focus on the most relevant hu- man interventions on the drainage network within the city walls. In ancient times, the southern area of the Urbs was drained by the Nodicus River, according to Lanciani (1881), that was the most important left tribu- tary of the Tiber River (TR) in the city. Geomorphologi- cal, archaeological and geological evidences show that Nodicus was a very significant tributary of the TR in terms of fluvial energy, as attested by the wide valley hosting the Circus Maximus. Despite the extensive ur- ban modifications during the Roman times, including land reclamation and backfilling, the Medieval Aqua Mariana artificial stream was carried out to flow within the Nodicus valley, at least downstream of the San Gio- vanni Basilica. As a consequence, we hypothesize that, until now, the Nodicus River’s dimensions, in terms of drainage-basin area and hydrographic-network evolution have been underestimated. 2. STUDY AREA Rome is located in the Tyrrhenian side of central Italy, W of the Lazio-Abruzzo Central Apennine (Fig. 1). The physical landscape, mainly hilly, is characterized by the presence of two volcanic reliefs, i.e. the Sabatini Mountains and the Alban Hills (Latium volcano). On the right and on the left sides of the TR, which links the city to the coast, two clearly different areas from a geomor- phological point of view are present. The territory on the left side of the TR (SE) hosts a large volcanic plateau, which formed during the Middle-Upper Pleistocene from https://doi.org/10.26382/AMQ.2018.08 120 Luberti G.M. et al. several eruptive phases belonging to both previous vol- canic districts. Over the same time, this plateau started to be deeply carved by the Tiber fluvial system, many times, in occasion of sea-level low standing (Bellotti et al., 2007). Thus, in the Upper Pleistocene a long phase of in-depth fluvial incision carved the same valleys as canyons or gorges (Pica et al., 2016; 2017, and refer- ences therein). The TR tributaries created a series of very deep valleys, with steep slopes. The most impor- tant valleys, including those drained by the main water course, today appear flat-bottomed, due to post-glacial fluvial depositional processes, which originated the flat surface (Fig. 2) corresponding to the current city centre (Campus Martius, Campo de' Fiori). The fluvial incision led to the development of nu- merous elongated ridges in the interfluvium areas, flat at the summit, which still dominate the urban landscape of this eastern sector; this is the typical shape of some of the famous Roman-age "Seven Hills", such as the Quiri- nale. Other hills, such as the Aventino and the Palatino, appear instead as small isolated reliefs, with steep slopes, sloping from the flat top towards the underlying alluvial plain of the TR (Fig. 3). In the western side of the TR, the alluvial plain ends at the foot of the ridge that connects, from N to S, the ridges of Monte Mario and Gianicolo (Figs. 2 and 3). The summit of this ridge reaches 139 m a.s.l., while the hills on the east side do not exceed 50 ÷ 60 m a.s.l. The basal outcropping lithologies of the study area (Fig. 2) consist of marine clays and marls (Pliocene and Early Pleistocene), up to 800 m thick. The marine sedi- mentary succession, accumulated in the depressions formed during the extensional tectonics of the Tyrrhe- nian margin of the Apennines, is overlain by epiconti- nental sediments deposited during the subsequent, pro- gressive, crustal uplift. Starting from about 0.8 Ma the Sabatini Mountains and Alban Hills volcanic complexes produced different rocks; in fact stratified lavas and py- roclastic flow, surge and fall deposits, are widespread throughout Rome (Fig. 2). These volcanic products alter- nated with sedimentary deposits and both were submit- ted to a very complex interplay of erosional and deposi- tional processes during sea level fluctuations, tectonic displacements and volcanic activity (Luberti et al., 2017 and references therein). The emplacement of volcanic products changed the topography and hydrography of the area (Heiken et al. 2005 and references therein): the ancient streams and the Tiber trunk (known as "Paleotevere") progres- sively moved towards the Monte Mario-Gianicolo ridge. Fig. 1 - The present-day urban area of Rome. It extends from the volcanic flanks of the Sabatini Mountains and the Alban Hills, located NW and SE respectively, to the Tiber River mouth, SW of the city centre. The urban centre, which is represented in Figure 2, is within the square blue frame. Upper-left corner coordinates: 42° 13’ 29’’ N, 12° 00’ 58’’ E (mosaic from NASA satellite images). 121 Anthropogenic modifications to the Aqua Mariana stream (Rome) Fig. 2 - The main outcropping lithologies of the city centre (modified after Del Monte et al., 2016, whose study area is marked by the blue line). The main valleys of Tiber River and its tributaries are recognizable, as well as the main ridges. A: trace of the geomorphologic cross section in Fig. 3. Upper-left corner coordinates: 41° 57’ 56’’ N, 12° 25’ 13’’ E. Fig. 3 - A schematic cross section along the city centre showing the main geomorphological features of the area (modified after Del Monte et al., 2013). The trace of the cross section is marked in Fig. 2. The last change of both the Rome urban area and the facing coastline is connected to the development of the TR hydrographic network during the major sea-level lowering, in correspondence of the Last Glacial Maxi- mum (LGM). The significant drop in sea level induced strong erosional processes; in the city centre, the TR and its tributaries cut into the Plio-Pleistocene succes- sion to an elevation of 50 m below the present sea level. During the following post-glacial sea level rise (17-5 ka; Bellotti et al., 2007), alluvial sediments, up to 60 m thick, were deposited (Bozzano et al., 2000; Ascani et al., 2008) (Fig. 3). During the last three thousand years, human activi- ties contributed to remodelling the topographic surface, profoundly modifying the hydrographic network and depositing almost everywhere a large quantity of anthro- pogenic heterogeneous and heterometric materials, deriving from various types of waste, fragments of bricks, tiles, amphorae, etc., all incorporated into a finer matrix, made up of volcanic, alluvial and colluvial materi- als. This "anthropogenic layer" continuously covers the entire Roman area, with a thickness that can vary from a few centimetres to several metres or even tens of metres in the valley bottoms (Del Monte et al., 2016). 3. METHODOLOGY: MULTI-DISCIPLINARY AND MULTI-TEMPORAL GEOMORPHOLOGICAL INVESTI- GATIONS The investigations, aiming at reconstructing the natural landscape of the city centre together with the main anthropogenic topographic and hydrographic modifications, were performed over several years, dur- ing which a detailed geomorphological survey and multi- temporal analysis of aerial photographs and topographic maps were carried out. To obtain information on morphological changes over longer periods, the geomorphological survey was supported by the analysis of aerial photographs (stereoscopic and non-stereoscopic) taken in the last 80 years. The results of the aerial photo analysis were matched with the geomorphological study of the ‘Piano topografico di Roma e Suburbio’, a topographic map surveyed in 1907 for the Urbanisation Plan of Rome, and updated in 1924, at 1:5000 scale with a contour interval of 1 m (IGM, 1924). Furthermore, in order to detect ancient modifications to the topographic surface, the analysis of historical cartography was conducted using both the available previous maps, surveyed with trigonometric methods, and other maps without contours and having planimetric precision. Among them, we in- cluded the maps by Moltke (1852) and Presidenza del Censo (1839); moreover, the Urbs map by Nolli (1748a), even though it only covers the area inside the imperial city walls. In addition, more ancient ‘bird’s eye’ maps were useful to detect some landforms (e.g. Dupérac, 1577; Falda, 1676; Frutaz, 1962). Moreover, important infor- mation on missing natural landforms was obtained from paintings and further iconographic documents. A number of old papers were also consulted, such as historical books, archaeological papers and the ar- chaeological map of Rome of Lanciani (1893-1901). In order to collect relevant information to the study of the geomorphologic characteristics before the man-made modifications, many recent studies on the ancient topog- raphy of Rome (e.g. Quilici, 1990) were examined, as well as the preliminary archaeological results from the works for the construction of the metropolitan railway line C (San Giovanni underground station explanatory panels, edited and organized by MiBACT and Roma Capitale). Locally, useful information about the thickness of the anthropogenic deposits, which mask natural depos- its and landforms, was also collected from the drilling databases (Ventriglia, 1971, 2002) and some geothe- matic maps, such as the ‘Anthropogenic deposit thick- ness’ maps (Corazza & Marra, 1995; Ventriglia, 1971). The spatial distribution of bedrock was traced ac- cording to the lithostratigraphic map of Ventriglia (2002) and also taking into account both other geological maps (Funiciello & Giordano, 2008; Marra & Rosa, 1995) and a large body of literature. 4. THE FLUVIAL LANDSCAPE OF ROME OVER HISTORICAL TIME AND ITS ANTHROPOGENIC MODIFICATIONS In the historical centre, the valleys crossed by the TR and its main tributaries today present a flat-bottomed configuration, due to both the depositional processes occurred since the end of last glacial and more recently the urbanisation. The main river plain (Fig. 4) extends, to E, at the foot of the slopes of the Pincio, Quirinale, Capi- tolino and Aventino hills, and to W at the foot of the Gianicolo-Monte Mario ridge. The main channels (including the TR) still show the effects of lateral and/or linear erosion, despite the erosion mitigation works oper- ated. On the west bank of the TR, the landforms shaped by the action of the surface running water are still very widespread throughout the area. The Monte Mario ridge is deeply furrowed by the Valle Aurelia, which slope progressively declines towards the TR, describing an anti-clockwise pattern near the Vatican City (Figs. 1 and 2). A good number of the fluvial channels, in particular the smaller ones, are still in the linear incision phase. A series of small, narrow and deep valleys affects the slopes of the Monte Mario-Gianicolo ridge, on the top of which few outcrops of volcanic products are observed. Even small through-shaped valleys are quite common; their genesis is due to the combined erosional action of surface runoff and gravitational processes. At the time of the foundation of Rome, Trastevere (Trans Tiberim), a flat area located at the foot of the Gianicolo ridge, was a marsh controlled by the Etrus- cans. Today's district lies entirely on the alluvial plain of the TR (Figs. 3 and 4). On the left bank of the TR, the fluvial plain is over- looked by a relief summit slightly inclined, considerably dissected by the erosive action of the TR system and its tributaries. Today the main fluvial valleys, partially filled by the post-glacial alluvial deposits, show a similar shape, though obviously varying in size. For example, 122 Luberti G.M. et al. the Murcia Valley, a small depression with a flat bottom (Fig. 2), perfectly straight for a length of two kilometres and about two hundred metres wide, represented an ideal natural landform for hosting a large stadium like the Circus Maximus (Del Monte et al., 2013; Del Monte, 2017). The urbanization of this fluvial landscape started a long time ago. It is well known that the ancients began to build Rome on the legendary Seven Hills. The first villages were built on the hills closest to the Tiber River and Isle (Coarelli, 2001); these hills, some tens of me- tres higher than the Tiber alluvial plain, being character- ized by steep slopes but rather flat summits, were easy to defend from enemy attacks and, at the same time, suitable to host stable settlements, being far from the marshes at the bottom of the valleys. Moreover, in this side of the TR, the erosional processes, already de- scribed in the previous paragraph, were and still are, of lower intensity and frequency (Del Monte et al., 2016). Thus, the Seven Hills and the other surrounding hills originated from the fluvial processes operated by the Tiber drainage system, which carved them during the Upper Pleistocene, and then were partially remodelled by natural and anthropogenic processes during the Holocene. During modern times all the historic hills of Rome have changed their shape. In the historic centre, many of the small natural hills have disappeared, flattened or buried up to the point that they can no longer be distin- guished. And yet, as already seen (Fig. 3), the most relevant part of the historical hills, i.e. those that have not undergone a complete demolition by human activi- ties, is detectable. The anthropogenic modifications of natural proc- esses and landforms have been relevant, in the city centre, at least since the 6th Century BC when the Ser- viane Walls were built with tuff-rock blocks excavated from local quarries. When the urbanisation moved from the hills down to the plains, several land-reclamation works were put in place, among which the realisation of the Cloaca Maxima for the drainage of the Velabrum minus. Another significant Roman-age anthropogenic change was the excavation of the saddle between the Capitolino and Quirinale hills. Conversely, the removal of Velia Hill, located between the Palatino and Esquilino, was operated in AD 1932 (Insolera, 2001). Over two millennia, human activities, in addition to earthquakes, floods and other natural processes (Berti et al., 2004), have progressively covered the surface of the historical city centre with layers of materials made up of the re- mains of collapsed buildings, rubbish and the ruins of ancient temples and monuments mixed with colluvium and alluvium. The TR embankments, built in the last century, now protect the city centre from flooding. Before the urbanisation, the Urbs territory was characterized by a rather dense hydrographic network, 123 Fig. 4 - Panoramic view from the Gianicolo Hill to NE (refer to Figure 2). The alluvial plain is visible in the middle of the picture, where the Tiber River is marked by the horizontal belt of trees separating the Trastevere and the Campus Martius districts. Beyond the plain, the Pincio and Quirinale hills represent the higher portions of the city in this photo. In the background, the Apennine chain. Anthropogenic modifications to the Aqua Mariana stream (Rome) whose channels drained the water of the respective watersheds. One of the most frequent forms - in the context of those modified by human activities - consists of partially filled river valleys, which have changed the shape of their natural valley section. These are valleys where the volume of anthropogenic deposits is often considerable, sometimes such as to reach a thickness equal to half (or even more) of the original altitude differ- ence between the thalweg and the top of the slopes (Fig. 5). This type of modified valley sections (sensu Del Monte et al., 2016) is well represented in the historical centre: in the east side of the Tiber, the Spinon Valley (Lanciani, 1881), between the Palatino and the Capito- lino, that of the Fosso Labicano, downstream and up- stream of the Colosseum, the Murcia Valley, the Valle Giulia, further N, and other valleys of the Monti Parioli. Also, to W of the TR, some valleys, such as the Inferno- Aurelia Valley (Del Monte et al., 2016), exhibit a similar configuration. Another type of anthropogenic landform well repre- sented in the territory of the historical centre is a "disappeared" form (sensu Del Monte et al., 2016), or rather an anthropogenic landform that completely oblit- erated the pre-existing natural valley. It is a mostly flat or weakly undulating surface, under which a valley lies buried by huge quantities of anthropogenic filling depos- its. In this case, its obscured (or invisible, sensu Clivaz & Reynard, 2017) landform (the natural valley) was de- tected by the authors after a multi-temporal analysis of topographic maps and aerial photographs. Its presence is more widespread E of the Tiber. The two landform typologies (i.e. modified and obliterated valleys) are well represented just outside the city walls, along the upper part of the Sant’Agnese stream (Fig. 2), which from Porta Pia and Piazza Fiume stretched for miles to NE, ending in the Aniene River (see the valley in Fig. 2) after passing Viale Libia (Fig. 5). 5. THE AQUA MARIANA The most relevant human interventions on the drainage network have been realized in the southern part of the city centre, in the area drained, in ancient times, by the most important left tributary of the TR within the walls. Its original path is known, with reason- able certainty, only downstream of the San Giovanni Basilica, and this valley stretch was covered by the an- cient Nodicus stream (Lanciani, 1881; Corazza & Lombardi, 1995). Conversely, in many historical maps of the period between the 16th century and the first dec- ades of the 20th century, the watercourse was indicated as Aqua Mariana or - improperly - Aqua Crabra (Frutaz, 1962, e.g. in Fig. 6). According to such historical topog- raphic maps, there is no doubt that the Aqua Mariana has represented for centuries the only important tribu- tary on the east side of the TR within the walls. The Aqua Mariana stream originated from the vol- canic system of the Alban Hills, near to the Lake of Cas- tel Gandolfo, being part of its centrifugal drainage net- work (Fig. 7). From the Marino village, close to the volcanic cra- ter, the stream flowed to NW on the volcanic flank, down 124 Fig. 5 - The Sant’Agnese valley landforms depicted: a) in the IGM 1924 topographic map (some 'disappeared valley' landforms, including the one at the waterhead section between Porta Pia and Viale Regina Margherita, are highlighted), and b) in a recent topographic map (almost all the pre-existing valleys have disappeared, except for a few that were only partially filled by man-made deposits, so they are still recognizable although deeply modified). In both a and b: the red line in the lower-left corner marks the Aureliane city walls; upper-left corner coordinates: 41° 56’ 03’’ N, 12° 29’ 37’’ E. Luberti G.M. et al. to the San Giovanni and Porta Asinaria gates (D in Fig. 8, and Fig. 9), located close to the San Giovanni Basilica (4th century AD). From that gate, the stream flowed S of the Celio Hill and out of the Aureliane Walls (whose whole circuit is shown in Fig. 6), built in the 3rd cen- tury AD. At the Porta Metronia gate (C in Fig. 8), it entered into the city. Here, the stream direction varied to NW, passing in the Murcia Valley (B in Fig. 8), the wide and long fluvial depression facing the Tiber Valley carved by the ancient Nodicus stream and exploited by the Romans for the Circus Maximus construc- tion. The Aqua Mariana flowed into the TR (A in Fig. 8), in front of Tiber Isle. For over a cen- tury the terminal stretch of the river has no longer been visible, due to urbanization inter- ventions. Archive resources attest that the Aqua Mariana was actually an artificial stream, cre- ated in the 12th century AD, diverting a tributary of the Aqua Crabra River (Fig. 7), which was a natural stream, to the Murcia Valley and then to the TR. In ancient times, according to the Medieval sources, the Aqua Crabra flowed to N, in the Aniene River. The Aqua Crabra was reported by Frontino, ‘curator of the waters’ at the time of Vespasian, to be the third river of Latium vetus in importance, after the Tiber and 125 Fig. 7 - Drainage network of the SE suburban area of Rome at the end of the 19th century AD. The red lines subdivide the portion of the Tiber River Basin represented in this image in three main sectors: sector XVII borders lower basin of the Aniene River (including the Aqua Crabra); sector XVIII indicates the Treia- Rome mid-portion of the Tiber River Basin (including the Aqua Mariana sub- basin); sector XIX - borders the lower basin of the Tiber River, from Rome to its delta. Nord upward. (Modified from ‘Hydrographic map of the Tiber-river ba- sin’ (Carta Idrografica del Bacino del Tevere: Anonymous, 1880) scale 1:259200, partial reproduction). Fig. 6 - The AD 1565 topographic map by Bernardo Gamucci, who depicted the ancient city (Urbs). The Aqua Crabra (blue line) is drawn as the only Tiber River tributary, as it actually was at the time of the author. (Modified from Frutaz, 1962). Anthropogenic modifications to the Aqua Mariana stream (Rome) the Aniene rivers. Therefore, it was judged by Pope Callistus II to be suitable for ensuring the water needs of the city within the Aurelian Walls, given the shortage of water that had passed since the 6th century AD, be- cause of the damage to the ancient aqueducts operated by the king of Goths Witiges. The water deviation from the Aqua Crabra was made in the Morena area, using an under- ground section of the Claudian aqueduct and, downwards, channelling the water into an artifi- cial riverbed, mainly built on ancient aban- doned river sections (Lanciani, 1881; An- noscia, 2007; Bultrini, 2012; Capelli, 2015). This hydrographic structure remained as previously described until the middle of the 20th century, when, because of floods affecting the urban area, the Aqua Mariana water was furtherly diverted to W, becoming part of the river basin of the Fosso dell’Almone-Caffarella (Capelli, 2015). After this second river devia- tion, the catchment area of the ancient Nodicus, the tributary of the TR that ran through the Murcia Valley, therefore seemed to return to the dimensions represented by Quilici (1990), and by Corazza & Lombardi (1995) (Fig. 10). The geomorphological features and di- mensions of the Murcia Valley, however, ap- pear to conform to a much wider river basin (Del Monte et al., 2013, 2016). Hence, the hypothesis that the original plano-altimetric configuration of the flu- vial system belonging to the Murcia Valley and the Nodicus is different, at the time of ancient Rome, from 126 Fig. 8 - The urban portion of the Aqua Mariana stream, marked in blue, as depicted in the Urbis Ichnographiam map by Nolli (1748b), here partially shown, modified. Legend: A) its confluence into the Tiber River; B) the Murcia Valley, where the Circus Maximus is located; C) the Porta Metronia gate; D) the Porta Asinaria gate. Fig. 9 - The Aqua Mariana stream flowing out of the Aureliane Walls, from the Porta San Giovanni white gate to the imperial-age Porta Asinaria towered gate. On the right, the Vicolo delle Tre Madonne road. The toponyms are depicted in the Presidenza del Censo map, 1839 (in the upper right box, par- tial reproduction). Photographer: anonymous, mid 1800s. Luberti G.M. et al. those reconstructed and represented by different au- thors (Quilici, 1990, Fig. 10; Corazza & Lombardi, 1995; Lombardi & Corazza, 2008), seems to be reasonable. Such a hypothesis is here argumented by geomor- phological, archaeological and geological evidences. 5.1. Geomorphological evidence The morphology of the Murcia Valley and minor valleys belonging to its river basin, as well as the devel- opment over time of the hydrographic network, undoubt- edly derive from both the erosional fluvial action oc- curred up to the Last Glacial Maximum and the subse- quent sedimentation by a natural river system (Del Monte et al., 2013, 2016). At the bottom of the valley between the Palatino and Aventino hills (Figs. 10, 11 and 12), the Circus Maximus would have found optimal positioning (Fig. 8), thanks to the considerable width and the particular shape of the Murcia Valley (Fig. 12). In the portion of the TR alluvial plain close to that valley, the Velabra marshes were originally located, and after land reclamation the Forum Boarium was built in that flat area (Figs. 10 and 11). The downstream confluence of the Nodicus might have favoured a lowering of the flu- vial current of the Tiber, determining the sedimentation of solid load and the formation of the Tiber Isle (Del Monte et al., 2013). According to Marra et al. (2018), the Tiber Isle origin might have been triggered by the east- ward diversion and loss of energy of the Tiber stream, as a consequence of the sudden collapse of the Forum Boarium area because of fault displacements. At this regard, it is to underline that the collapse of the Forum Boarium area would more likely have determined an increase in slope and fluvial power, favouring the ero- sion upstream. Conversely, fluvial deepening effects can be observed just downstream of Tiber Isle, e.g. on the west flank of the Aventino Hill. The eastward migration of the Tiber stream might be simply due to the normal fluvial dynamics, during a free meandering phase. Some reconstructions show (Lombardi & Corazza, 2008) the trunk of this ancient river system would seem to come from the area where the Colosseum was built, i.e. from the narrow Labicana Valley that separates the Oppio and Palatino hills from the Celio (Fig. 10). Numer- ous other sources (Lanciani, 1881; Quilici, 1990; Corazza & Lombardi, 1995) and the current morphology show instead that a wider valley section - similar to that of the Murcia Valley – comes from SE, along the same direction (Fig. 10). Thus, the valley located between the Oppio-Palatino and the Celio, comparable in size to the Spinon Valley, would have been, in reality, travelled by a 127 Fig. 10 - The Nodicus River Basin (red line) as delineated according to the pre-urbanization topography reconstructed by Quilici (1990). The red ‘M’ depicts the location of the ‘Via La Spezia’ site. Anthropogenic modifications to the Aqua Mariana stream (Rome) 128 Fig. 11 - The geological map drawn by Giuseppe Ponzi in 1850 (partial reproduction of the original sheet, ISPRA Library). The map is useful to depict the landscape of the city centre. Numbers and colours refer to the main lithologies: 1. Volcanic tuffs (fuchsia); 2. sands and gravels (yellow). The light-blue colour around the Tiber River represents the ‘level of the water at the ancient diluvium time’, even if the map shows the walls of the city. According to the author, at the ‘diluvium time’ the water level was some tens of metres above the present- day level of the Tiber River, so covering the alluvial plains and the lower portions of the hills. Luberti G.M. et al. small right tributary of the Nodicus. 5.2. Archaeological evidence According to Lanciani (1881), the upstream portion of the Murcia Valley was actually travelled by the Nodicus River, which, in the area that then hosted the Baths of Caracalla, received the contributions of many tributaries. The main trunk seems to come from the E (Fig. 10), where, according to Lanciani (1881) and Gnoli (1939), there was a marshy area (Palus Decenniae), whose existence was later confirmed by archaeological excavations (Demetrescu et al., 2011). Such archaeo- logical and geognostic investigations, connected to the construction of the metropolitan railway line C, high- lighted frequent protohistoric floods in the area around the Palus Decenniae (Fig. 10), confirming the hypothe- sis that a considerable water course passed, in antiq- uity, in the stretch between Porta Metronia and Porta Asinaria, just in correspondence of the artificial riverbed that would have been created for the outflow of the Aqua Mariana artificial stream (Fig. 9). Moreover, more recent archaeological investiga- tions indicate that in the ‘Via La Spezia’ site (depicted in Fig. 10) in the 3rd century BC a bank with a length of more than 130 m and direction NE-SW was put in place in order to defend roads and crops from the floods, and an artificial basin 70x35 m wide and with a mean depth of 2 m, dating 1st century AD, was revealed, about 15 m below the present-day ground level. It is the widest Ro- man-age artificial basin that has ever been discovered. Artefacts that were recovered within the basin suggest that it was both a water storage and fish farm basin. At the end of the 1st century AD the farm was abandoned and the basin filled with anthropogenic deposits. From the end of the 2nd to the beginning of the 4th centuries AD relevant land-reclamation works were made (Ministero dei beni e delle attività culturali e del turismo - Ministry of Cultural Heritage and Tourism, 2018). Owing to the abovementioned evidence, it is rea- sonable to state that about two thousand years ago, this river had to be very important, both for the extension of its basin, and for river flow and power. 5.3. Geological evidence The Nodicus River, according to the geological evidence, had the greatest fluvial energy, compared with those of the other streams in the Urbs. At the Cir- cus Maximus a 12 m thick gravel stratum with thin inter- bedded clay layers was shortly described by Signorini (1939). An erosional surface separates it by the underly- ing Pliocene deposits. According to the interpretation given by Ventriglia (1971), this body is part of the fluvial sedimentation that took place after the Last Glacial pe- riod, i.e. Upper Pleistocene-Holocene. Recently, Marra et al. (2016) geochronologically determined that the deposition of the basal gravel stratum in the Rome’s basin occurred between the Last Glacial Termination and the Meltwater Pulse 1a (Stanford et al., 2011), i.e. during the uppermost Pleistocene. This stratum is gen- erally up to 10-15 m thick, even in the TR urban sections (Bozzano et al., 2000; Marra et al., 2008, 2013). How- ever, the gravel stratum is very often missing in most of the Tiber tributaries S of the Aniene confluence, or it is very thin. In the city centre, a less than 5 m thick gravel stratum was detected at the Colosseum, but it is not clear whether it is referred to Paleotiber gravels depos- ited at the beginning of Middle Pleistocene, as sug- gested by Bozzano et al. (1995) or to the uppermost Pleistocene deposits, as stated by Pagliaroli et al. (2014). Since Corazza (2012) reported that gravels de- tected in a borehole located before the confluence of the Colosseum stream in the Murcia Valley are just made of calcareous and siliceous centimetric clasts, whereas the gravels at the Circus Maximus are composed of both calcareous and siliceous, and tufaceous clasts up to 6-7 cm, it is more likely that only the gravels detected in the Murcia Valley are related to the Upper Pleistocene early sedimentation of materials partially eroded from volcanic rocks, whose massive eruptions started not before 600 ka (Luberti et al., 2017). These geological data imply that the Nodicus was surely the greatest river within the Urbs, in terms of rate of flow and energy, with the obvi- ous exception of the Tiber. The thickness and the fining-upward stratigraphic succession of the whole MIS 1 fluvial deposits in the Murcia Valley are similar to those of some downstream Tiber’s tributaries that are characterised by much greater hydrographic basins. Among them, in the Fosso di Vallerano Valley ('F. di Castello' in Fig. 7), which is approximately 10 km S of the city centre, the uppermost- Pleistocene basal polygenic gravels up to 10 m thick were detected about 1 km from its confluence into the TR (Bozzano et al., 2016). However, the Fosso di Valler- ano basin, which originates from the Alban Hills close to 129 Fig. 12 - View of the Murcia valley. The photo was taken from the Terme di Caracalla area (F.A.O. building) to N. Anthropogenic modifications to the Aqua Mariana stream (Rome) Castel Gandolfo village, is 67 km2 wide and its main stream is 23 km long. For comparison, the Fosso di Grottaperfetta basin, about 4 km S of the city centre, is 14 km2 wide and the length of its main stream is 11 km (Ventriglia, 2002). In that valley several boreholes lo- cated about 1 km from the Tiber plain detected a very thin gravel stratum up to 3 m thick just in the central portion of the Upper Pleistocene palaeovalley. More- over, the fining-upward deposits are characterised by several peat layers (Cinti et al., 2008). 6. CONCLUSIONS Taking into account the evidence above discussed, it is reasonable to assume that the ancient fluvial basin belonging to the Murcia Valley was much wider than that inferable from the current topography and those reconstructed from the studies of Quilici (1990) or sim- ply represented in Corazza & Lombardi (1995), and Lombardi & Corazza (2008), all belonging to an area that is too limited. The main water course, before reaching the Murcia Valley, was very likely to follow the outflow direction then followed by the Aqua Mariana, the artificial channel that was built in the 12th century AD (Fig. 7). In other words, Pope Callistus II may have restored, we do not know how consciously, a natural outflow line, in the same place where it naturally developed and was still active at the time of Romulus. The shape and size of the Murcia Valley, decidedly disproportionate to the modest dimensions of the water catchment area that can be deduced from the present day topographic map, confirm the importance of the ancient river that ran between the Aventino and the Celio-Palatino up to about two thousand years ago. ACKNOWLEDGEMENTS The authors thank the Ministero dei beni e delle attività culturali e del turismo (MiBACT, Ministry of Cul- tural Heritage and Tourism) and the Municipality of Roma Capitale for having provided information on ar- chaeological preliminary results concerning the metro- politan railway line C. In addition, they are grateful to the Associate Editor Adele Bertini and the Reviewers Piero Bellotti and Emmanuel Reynard for supportive com- ments and suggestions. The final manuscript benefited also from insightful suggestions from Gabriella Forno (University of Turin). REFERENCES Annoscia G.M. (2007) - Fonti e strutture per la cono- scenza del sistema idrico di Roma nel Medioevo. Aracne Ed., pp. 375. Anonymous (1880) - Carta idrografica con l'indicazione dei principali affluenti del fiume Tevere e delle stazioni metereologiche e idrometriche. Tiber River watershed map, scale 1:259200, 1 sheet 90 x 61 cm, Roma, Lit. Virano e Teano. Ascani F., Bozzano F., Buccellato A., Del Monte M., Matteucci R., Vergari F. (2008) - Evoluzione del paesaggio e antiche vie di drenaggio nell’area de “Il Castellaccio” (Roma) da indagini geologiche, geomorfologiche e archeologiche. Geologica Ro- mana, 41, 93-116. Bellotti P., Calderoni G., Carboni M.G., Di Bella L., Tor- tora P., Valeri P., Zernitskaya V. (2007) - Late Quaternary landscape evolution of the Tiber River delta plain (Central Italy): new evidence from pol- len data, biostratigraphy and 14C dating. Z. Geo- morphology, 126(4), 505-534. Berti D., Esposito E., Giusti C., Luberti G.M., Piccardi L., Porfido S., Violante C., Vittori E. (2004) - Geologi- cal setting, hazards and urban growth in some historical towns in Italy. Atti 32nd IGC-Firenze. Memorie Descrittive della Carta Geologica d’Italia, 63(6), 1-72. Bozzano F., Funiciello R., Marra F., Rovelli A., Valentini G. (1995) - Il sottosuolo dell’area dell’Anfiteatro Flavio in Roma. Geologia Applicata e Idrogeologia, 30(1), 405-422. Bozzano F., Andreucci A., Gaeta M., Salucci R. (2000) - A geological model of the buried Tiber River valley beneath the historical centre of Rome. Bulletin of Engineering Geology and the Environment, 59, 1- 21. Bozzano F., Lenti L., Marra F., Martino S., Paciello A., Scarascia Mugnozza G., Varone C. (2016) - Seis- mic response of the geologically complex alluvial valley at the “Europarco Business Park” (Rome- Italy) through instrumental records and numerical modelling. Italian Journal of Engineering Geology and Environment, 16(1), 37-55. Doi: 10.4408/IJEGE.2016-01.O-04 Bultrini E. (2012) - L’acqua Crabra: un fiume scomparso vicende del confine naturale tra Roma e la Civitas Tusculana. Archivio della Società romana di storia patria, 135, 63-83. Capelli G. (2015) - La Marrana dell’acqua Mariana. Un corso d’acqua al servizio dei Papi. Acque Sotterra- nee - Italian Journal of Groundwater, ASr15092, 79-82. Doi: 10.7343/AS-135-15-0162 Cinti F.R., Marra F., Bozzano F., Cara F., Di Giulio G., Boschi E. (2008) - Chronostratigraphic study of the Grottaperfetta alluvial valley in the city of Rome (Italy): investigating possible interaction between sedimentary and tectonic processes. Annals of Geophysics, 51(5,6), 849-865. Clivaz M., Reynard E. (2017) - How to integrate invisible geo-morphosites in an inventory: a case study in the Rhone River valley (Switzerland). Geoheritage. Doi: 10.1007/s12371-017-0222-7 Coarelli F. (2001) - Roma. Guide Archeologiche Laterza, ed. Laterza, Roma, pp. 488. Corazza A. (2012) - Analisi dei fattori di pericolosità geologica presenti nella città di Roma attraverso l’esame di alcuni casi di studio. Ph.D. Thesis in Environmental Geology and Geodynamics, a.y. 2011/2012, Università degli studi di Roma Tre, pp. 282. http://hdl.handle.net/2307/3989. Corazza A., Lombardi L. (1995) - Idrogeologia dell'area del centro storico di Roma. In: La geologia di Ro- ma: il centro storico. Memorie Descrittive della 130 Luberti G.M. et al. Carta Geologica d’Italia, 50, 179-211. Corazza A., Marra F. (1995) - Carta dello spessore dei terreni di riporto. In: La geologia di Roma: il centro storico. Memorie Descrittive della Carta Geologica d’Italia, 50, tav. 13. Del Monte M. (2017) - Aeternae Urbis Geomorphologia - Geomorphology of Rome, Aeterna Urbs. In: Soldati M., Marchetti M. (eds) Landscapes and Landforms of Italy. Springer, Cham, 339-350. Doi: 10.1007/978-3-319-26194-2 Del Monte M., Fredi P., Pica A., Vergari F. (2013) - Geo- sites within Rome City center (Italy): a mixture of cultural and geomorphological heritage. Geografia Fisica e Dinamica Quaternaria, 36 (2), 241-257. Doi: 10.4461/GFDQ.2013.36.20 Del Monte M., D’Orefice M., Luberti G.M., Marini R., Pica A., Vergari F. (2016) - Geomorphological classification of urban landscapes: the case study of Rome (Italy). Journal of Maps, 12 (Iss. Sup1), 178-189, pls. 1. Doi: 10.1080/17445647.2016.1187977 Demetrescu E., Fontana S., Rea R. (2011) - Conoscen- ze pregresse e nuovi dati: l’evoluzione del paesag- gio. In: Cantieristica archeologica e opere pubbli- che. La Linea C della Metropolitana di Roma, trat- ta T4: stazioni San Giovanni, Lodi. Indagini 2010- 2011. Mondadori Electa, Milano, 61-90. Dupérac E. (1577) - Nova Urbis Romae Descriptio. Pro- vided by the Roma Tre University, Architecture Dept. Library. Falda G.B. (1676) - Novissima et accuratissima delinea- tio Romae veteris et novae. In viatorum usum et commoditatem excusa. One 500×590 mm sheet map. Provided by the Archivio Capitolino, Comune di Roma. Frutaz A.P. (1962) - Le piante di Roma. Istituto Nazio- nale di Studi Romani, pp. 358. Funiciello R., Giordano G. (2008) - La nuova carta geo- logica di Roma: litostratigrafia e organizzazione stratigrafica. In: Funiciello R., Praturlon A., Giorda- no G. (eds.) La geologia di Roma dal centro stori- co alla periferia. Memorie Descrittive della Carta Geologica d’Italia, 80(1), 39-85. Gnoli U. (1939) - Topografia e toponomastica di Roma medioevale e moderna. Staderini Editore, Roma. Heiken G., Funiciello R., De Rita D. (2005) - The Seven Hills of Rome. Princeton University Press, Prince- ton, 264 pp. IGM (1924) - Piano Topografico di Roma e suburbio, Fogli 1-12. Istituto Geografico Militare. Maps sur- veyed in 1907, updated in 1924. Scale 1:5000 maps, provided by the Archivio Capitolino, Comu- ne di Roma. Insolera I. (2001) - Roma Fascista nelle fotografie dell’Istituto Luce. Editori riuniti, Roma, pp. 271. Lanciani R. (1881) - Topografia di Roma antica. I com- mentarii di Frontino intorno le acque e gli acque- dotti. Memorie Reale Accademia Lincei, ser. 3, 4, 215-614. Lanciani R. (1893-1901) - Forma Urbis Romae. Ulrico HOEPLI, 46 pls. Lombardi G., Corazza A. (2008) - L’acqua e la città in epoca antica. In: La geologia di Roma. Dal centro storico alla periferia. Memorie Descrittive della Carta Geologica d’Italia, 80 (1), 189-219. Luberti G.M., Marra F., Florindo F. (2017) - A review of the stratigraphy of Rome (Italy) according to geo- chronologically and paleomagnetically constrained aggradational successions, glacio-eustatic forcing and volcano-tectonic processes. Quaternary Inter- national, 438(B), 40-67. Doi: 10.1016/j.quaint.2017.01.044 Marra F., Florindo F., Boschi E. (2008) - History of gla- cial terminations from the Tiber River, Rome: In- sights into glacial forcing mechanisms. Paleocean- ography, 23(2), 1-17. Doi: 10.1029/2007PA001543 Marra F., Bozzano F., Cinti F.R. (2013) - Chronostrati- graphic and lithologic features of the Tiber River sediments (Rome, Italy): implications on the post- glacial sea level rise and Holocene climate. Glob. Planet. Change, 107, 157-176. Doi: 10.1016/j.gloplacha.2013.05.002 Marra F., Rohling E.J., Florindo F., Jicha B., Nomade S., Pereira A., Renne P.R. (2016) - Independent 40Ar/39Ar and 14C age constraints on the last five glacial terminations from the aggradational succes- sions of the Tiber River, Rome (Italy). Earth Planet Sci. Lett., 449, 105-117. Doi: 10.1016/ j.epsl.2016.05.037 Marra F., Motta L., Brock A.L., Macrì P., Florindo F., Sadori L., Terrenato N. (2018) - Rome in its set- ting. Post-glacial aggradation history of the Tiber River alluvial deposits and tectonic origin of the Tiber Island. PLoS ONE, 13(3). Doi: 10.1371/journal.pone.0194838 Marra F., Rosa C. (1995) - Stratigrafia e assetto geologi- co dell’area romana - In: La geologia di Roma: il centro storico. Memorie Descrittive della Carta Geologica d’Italia, 50, 49-118. MiBACT, Ministry of Cultural Heritage and Tourism (2018) - San Giovanni underground station, ex- planatory panels edited and organized by MiBACT and Roma Capitale. San Giovanni Metro C, exhibi- tion hall, Rome. Moltke H.K.B. Graf Von (1852) - Carta Topografica di Roma e dei suoi contorni fino alla distanza di 10 miglia fuori le mura, indicante tutti i siti ed edifizii moderni ed i ruderi antichi ivi esistenti. Eseguita coll’appoggio delle osservazioni astronomiche e per mezzo della mensola delineata sulla proporzio- ne di 1:25.000 dal Barone di Moltke Aiutante di campo di S.A. Reale il Principe Enrico di Prussia a Roma negli anni 1845 e 1846. Simone Schropp e C°, Berlino. Map provided by the Dpt. of Earth Sc., ‘Sapienza’ University of Rome. Nolli G.B. (1748a) - Nuova pianta di Roma data in luce da Giambattista Nolli l’anno MDCCXLVIII. Alla santità di nostro signore Papa Benedetto XIV la nuova topografia di Roma ossequiosamente offeri- sce e dedica l’umilissimo servo Giambattista Nolli comasco. Map of 12 elements: 430/440×680/690 mm and 480×720 mm. Provided by the Archivio Capitolino, Comune di Roma. 131 Anthropogenic modifications to the Aqua Mariana stream (Rome) Nolli G.B. (1748b) - Roma: Silvio Valenti tit. S. Callix. presb. s. r. e. card. camerario Benedicti 14. P. M. administro urbis ichnographiam a Leonardo Bufali- no ligneis formis evulgatam servata proportione contractam atque aeri incisam Jo. Baptista Nolli inc. Franc. Monaco & Carol. Nolli. Map of one sheet. Provided by the Archivio Capitolino, Comu- ne di Roma. Pagliaroli A., Quadrio B., Lanzo G., Sanò T. (2014) - Numerical modelling of site effects in the Palatine hill, Roman Forum, and Coliseum Archaeological Area. Bulletin of Earthquake Engineering, 12(3), 1383-1403. Pica A., Vergari F., Fredi P., Del Monte M. (2016) - The Aetena Urbs Geomorphological Heritage (Rome, Italy). Geoheritage, 8(1), 31-42. Doi: 10.1007/s12371-015-0150-3 Pica A., Reynard E., Grangier L., Ghiraldi L., Perotti L., Del Monte M. (2017) - GeoGuides, Urban Geot- ourism Offer Powered by Mobile Application Tech- nology. Geoheritage, 10(2), 311-326. Doi: 10.1007/s12371-017-0237-0 Ponzi G. (1850) - Geologia del bacino di Roma. Geolo- gic map enclosed to: Ponzi G., Sulla storia fisica del bacino di Roma: memoria di Giuseppe Ponzi da servire da appendice all'opera Il suolo fisico di Roma di G. Brocchi. Roma: Tip. delle Belle arti, pp. 24. Presidenza del Censo (1839) - Carta topografica del suburbano di Roma, desunta dalle mappe del nuovo censimento e trigonometricamente delinea- ta nella proporzione di 1.15000 per ordine dell’E.mo e R.mo Principe Sig. Cardinale Gio. Francesco Falzacappa. Stato Pontificio, Roma. Provided by the Archivio Capitolino, Comune di Roma. 132 Quilici L. (1990) - Forma e urbanistica di Roma arcaica. In: Cristofani M., La grande Roma dei Tarquini. Catalogo della mostra in Roma, 12 giugno - 30 settembre 1990, L’Erma di Bretschneider, Roma, 28-44. Signorini R. (1939) - Risultati geologici della perforazio- ne eseguita dall’AGIP alla mostra autarchica del minerale nel Circo Massimo di Roma. Bollettino della Società Geologica Italiana, 63., fasc. 2-3, 1- 3. Stanford J.D., Hemingway R., Rohling E.J., Challenor P.G., Medina-Elizalde M., Lester A.J. (2011) - Sea -level probability for the last deglaciation: a statisti- cal analysis of far-field records. Glob. Planet. Change, 79, 193-203. DOI: 10.1016/j.gloplacha.2010.11.002 Ventriglia U. (1971) - Geologia della città di Roma. Am- ministrazione Provinciale di Roma, pp. 417. Ventriglia U. (2002) - Geologia del territorio del comune di Roma. Amministrazione Provinciale di Roma, pp. 810. Ms. received: March 3, 2018 Final text received: September 3, 2018 Luberti G.M. et al.