Natural and Anthropic Constraints on Historical Morphological Dynamics in the Middle Stretch of the Po River (Northern Italy)

Abstract

Geo-historical information deduced from geo-iconographical resources, derived from extensive research and the selection of cartographies and historical documents, enabled the investigation of the natural and anthropic transformations of the perifluvial area of the Po River in the Emilia-Romagna region (Italy). This territory, significant in terms of its historical, cultural, and environmental contexts, for centuries has been the scene of flood events. These have characterised the morphological and dynamic variability in the riverbed and relative floodplain. The close relationship between man and river is well documented: the interference induced by anthropic activity has alternated with the sometimes-damaging effects of river dynamics. The attention given to the fluvial region of the Po River and its main tributaries, in a peculiar lowland sector near Parma, is critical for understanding spatial–temporal changes contributing to current geo-hydrological risks. A GIS project outlined the geomorphological aspects that define the considerable variations in the course of the Po River (involving width reductions of up to 66% and length changes of up to 14%) and its confluences from the 16th to the 21st century. Knowledge of anthropic modifications is essential as a tool within land-use planning and enhancing community awareness in risk-mitigation activities and strategic management. This study highlights the importance of interdisciplinary geo-historical studies that are complementary in order to decode river dynamics in damaging flood events and latent hazards in an altered river environment.

1. Introduction

In Italy, there are many water bodies that have undergone major transformations, especially in the vast lowland areas, due to overlapping anthropogenic interventions, the expansion of inhabited areas, and land use of various kinds (road, rail, ship, and airport infrastructures; the extraction of natural resources; industrial areas; intensive farming; livestock breeding activities, etc.) [1,2,3,4,5,6]. Geographical as well as political dynamics and intense anthropic uses have also led to significant geomorphological transformations of river territories.

In fact, human activities on the territories have appreciably modified the river plain environment through time. The main watercourses, and often minor hydrographic networks, show important changes over time [7,8]. The extent of the modifications is often such that they have obliterated the original courses of watercourses, reducing or nullifying the risk perception in the population [9].

River confluence areas are also particularly significant; in fact, they are a fundamental element for a river basin in terms of their effects on its geomorphology and hydrology [1]. In the confluence zone, watercourses combine their solid–liquid contributions, creating conditions of increased turbulence, flow variations, and altered sediment transport/erosion/deposition balances. The interaction of tributaries with a main river can influence grain-size distribution and the composition of sediment stored in alluvial plains. In fact, these processes contribute significantly to the solid transport capacity of the main river in terms of the volume, timing, and mode of sediment transported downstream. These factors therefore modify the flow patterns that govern the morphology in the confluence areas and downstream sectors, leading to variations in the river pattern. Several authors have attempted to represent these areas with hydraulic models, paying particular attention to the morphodynamic and hydraulic elements of the basins [4,7,10,11].

Different water management strategies in different historical periods influenced the spatial distribution of urbanisation sites and are also related to the importance of agricultural suitability over flood risks.

For an in-depth study of these issues, a representative area of fluvial and anthropic transformations in the lowland stretches was identified in relation to geomorphological confluence: the floodplain of the Po River. The Po River, Italy’s longest river, has always been subject to flood events that have shaped its course and surrounding environment [12]. From its source on the Monviso mountain slopes (3841 m a.s.l.) in the Western Italian Alps to its Delta in the Adriatic Sea, the Po River has gone through centuries of geomorphological, hydrological–hydraulic, and anthropogenic changes.

The Po River basin runs through all the regions of Northern Italy, mainly involving Piedmont, Lombardy, Emilia-Romagna, and Veneto, whose administrative borders are marked by some stretches of the Po River. Riverine areas represent complex human–water systems [13,14,15], as floodplains have always been among the most suitable environments for human subsistence; these conditions highlight the influence of flood geomorphology on the settlement strategies in the Po floodplain.

Geomorphological studies also rely on land-use analyses in relation to historical vicissitudes in the riparian areas close to the Po River, which drains an area of approximately 75,000 km², with more than 600 km of linear development transversely east–west along the Po River floodplain, known as the Pianura Padana [16].

Indeed, the Po floodplain, the largest in Italian territory, is also the most intensively utilised from both industrial and agricultural perspectives, contributing to approximately one-third of the national GDP [17].

Analysis made it possible to reconstruct planimetric variations, the directions, and morphological transformations of the course of the river in areas close to the main watercourse and its main tributaries, which are of great historical and economic interest.

Various studies contributed to the research, part of the PRIN (Italian Projects of Significant National Interest, 2020), called FONTES (Geo-historical sources and information systems for territorial knowledge and the management of environmental and cultural risks) [18]. The aim of the PRIN project was to make the knowledge derived from multidisciplinary studies, converging in geographic, geocartographic, and geo-historical in-depth studies, available, implementable, and operational in the geological and hydraulic fields. The historical documentary material collected contributed to reconstructing the transformation of the territory over the centuries and to interpreting its geo-hydrological vulnerability. This type of risk has been addressed over time through engineering works and interventions that have significantly affected the morphology and dynamics of the water system.

The national FONTES project proposes the development of organisation, filing, and localisation systems (by means of databases and WebGIS) that can be functional in providing decision support and intended for the identification, assessment, and management of environmental as well as cultural vulnerability elements recognisable in river regions, particularly in the middle course of the Po River and some of its tributaries.

The interpretation of historical documentary sources (textual, cartographic, and iconographic) has played a fundamental role in the identification of these elements. Those deriving from the current observation of the territory, in order to develop integrated cognitive and evaluative procedures, supplement these analyses. This approach highlighted the fact that only multidisciplinary activity was able to provide a correct cognitive process of the river territory and of the predictions of the dynamic–morphological trends. The project, which stands as a synthesis of geo-historical, historical–architectural, and geological research, finds its focus in the research, identification, systematisation, and valorisation of the historical and cartographic sources relating to the area under examination [19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34].

Beyond the reconstruction of the interactions between flood-related impacts and the historical fluvial setting, the described research also contributes to the advancement of methodological approaches for the development of more-effective strategies for flood risk mitigation. A further objective of the research was to structure a geographic database aimed at the cataloguing, consultation, and analysis of spatial data by different types of users in order to enable their functional use by land managers and planners. In such research, the interpretation of historical context is the starting point but also the correct target for the information needed to increase knowledge and its dissemination through the enhancement of its searchability through digital repositories. The case study is therefore focused on a significant stretch of the Po River of about 35 km, on which it was possible to find a rich amount of historical and recent spatial data.

This study also aims to examine the most significant flood dynamics of the Po River, with particular attention to the reactivation of historical riverbeds and related morphologies, analysing the morphological effects of the main floods of the 20th century and their impact.

2. General Settings

2.1. The Study Area

The Po River rises in the Western Alps (by the Monviso Peak, 3841 m a.s.l.) (Alpi Cozie) [35] and flows easterly, receiving over 140 tributaries, which drain an area of about 75,000 km², making it one of the largest river basins in Europe. This study focused on the stretch of the Po River downstream from the town of Cremona (Lombardy region) to the territory of Boretto, which runs along the right bank under the jurisdiction of the Emilia-Romagna region, and covers an area of approximately 100 km² (Figure 1).

Large outcrops of crystalline–metamorphic rocks and ophiolite complexes, as well as Mesozoic carbonate rocks, are largely exposed in the Southern and Eastern Alps, characterising the medium-upper Po basin. The geological characterisation is completed by the extensive coverage of the current alluvial plain deposits, variously represented by debris attributable to the meandering course of the Po River, by distal alluvial fans and Apennine alluvial plain deposits. In the Po River sedimentary basin, we therefore find gravels and sands of river channel filling, which form thin layers interspersed in a silty or silt–clayey succession that form channelled bodies [36]. The alluvial fan deposits of the minor hydrographic network are represented by alternating sands and silts; locally, there are levee breach deposits or overflow deposits and subordinate gravelly river channel bodies. The complex geomorphological evolution of the Po Valley [37,38,39] is also connected to climate change. Particularly significant for the geomorphological evolution of the Po and Alpine rivers were the Last Glacial Maximum (LGM), also known as the Würm Glaciation (around 20,000 years ago), and the first deglaciation that occurred between 20,000 and 12,000 years ago, corresponding to a phase of rapid generalised climate warming [40,41].

The geological stratigraphy shows the Holocene northward migration of the Po River, resulting in the erosion of the distal alpine deposits of the LGM and the formation of a fluvial escarpment parallel to the course of the Po River. Late Pleistocene and Holocene climatic changes also influenced river dynamics by controlling the balance between sediment supply and runoff through glacier dynamics. The Apennine, Alpine, and Po River systems responded in different ways to climatic forcing, through the influence of local factors. The lithology, drainage area, and average elevation of river basins, as well as the gradients of rivers and valleys, have determined the type of sedimentary response (e.g., by sediment aggradation or degradation) [10].

The study area includes the confluence sectors of some important watercourses in the Po River, including the Taro, Parma, and Enza rivers [42,43,44,45] (Figure 1). For these watercourses, there is historical evidence of countless hydraulic interventions, such as channelling, bank defences, regulation, and embankments, related to the attempt to mitigate the damaging effects of floods and to control water discharge [10,46]. Anthropogenic interventions have compounded the natural dynamics of the Po River, including frequent course alterations driven by hydrological events such as floods. These combined processes have contributed to the development of distinct fluvial morphologies aligned with former riverbeds, which represent different evolutionary stages of the river system. These historical riverbeds provide geomorphological evidence of fluvial erosion and sedimentation processes, especially in areas characterised by meanders and floodplain environments.

2.2. Historical–Political Framework of the Study Area

The anthropogenic interaction with the fluvial and perifluvial environment of the Po River stretch, between the provinces of Parma and Reggio Emilia, is highlighted by persistent hydraulic problems and historically documented adverse effects. These processes are further exacerbated by the presence of administrative boundaries and defensive structures. This study covers a time span of approximately 500 years, during which a significant body of cartographic, iconographic, and textual documentation regarding the critical conditions of the Po River and its tributaries has been compiled.

In 1545, the territories of Parma and Piacenza, initially under the Duchy of Milan and later, from 1512, under the Papal States, were elevated to two distinct duchies, unified under the rule of the Farnese family until 1731. Subsequently, the throne passed to the children of Elisabeth Farnese, the second wife of Philip V of Spain, giving rise to the Parma branch of the Bourbon-Parma Dynasty, who, through the Treaty of Aquisgrana (Aix-la-Chapelle), also acquired the small Duchy of Guastalla, where a cadet branch of the Gonzaga family had recently become extinct. Following the Napoleonic Era, the Congress of Vienna assigned the Duchies of Parma, Piacenza, and Guastalla to Maria Luigia of Austria. Upon her death in 1847, the Bourbons took over, maintaining control until 1859, when the region was annexed to the provinces of Emilia and later to the Kingdom of Italy.

The study area, which in the modern period corresponded to the northeastern portion of the Duchy of Parma, bordered the Estense Duchy of Modena and Reggio Emilia, to the east of the Enza River, and the Duchy of Milan, to the north of the Po River. It also included the small fief of Mezzani, which was under the jurisdiction of the Episcope of Parma until 1763.

The complex territorial organisation within the riverine area of the Po River has long been characterised by land parcelization and the heterogeneous distribution of interests and interventions with multiple objectives, including (i) the mitigation of flood-related damage; (ii) the utilisation of the river stretch for navigation, irrigation, and hydraulic power; and (iii) the preservation of boundary limits, through the reduction in land losses and the acquisition of new areas in response to lateral shifts in the river course. In order to fully exploit the available documentary resources, it was essential to reconstruct in detail the historical–institutional context (

Table 1. Main geo-political Bodies contexts that affected the study area.

Historical and Institutional Context	Date
Duchy of Milan	1395–1535
Alternation between the Kingdom of France and the Papal States	1500–1545
Farnese Duchies of Parma and Piacenza	1545–1731
Interregnum with alternation between Spanish and Austrian rule	1732–1748
Bourbon Duchies of Parma, Piacenza, and Guastalla	1748–1802
French General Administration	1802–1808
French Empire	1808–1814
Duchies of Parma, Piacenza, and Guastalla under Maria Luigia of Austria	1815–1847
Parma States under the Bourbon-Parma Dynasty	1848–1859
Kingdom of Italy	1861–1946
Italian Republic	1946–today

) and to identify the archival collections containing cartographic materials crucial for a diachronic geomorphological analysis of the river system (Figure 2).

2.3. Constraints on the Po Riverine Area in the Parma Stretch

The territory close to the Po River in the A–B stretch (see Figure 1) has undergone many conditionings that over the centuries have transformed morphologies and river dynamics, even in the confluence areas, at times altering the effects of flood outflows. The main conditionings can be traced back to a dual origin: (I) natural, which includes planimetric variations, changes in water direction, confluence regression, the conditioning of tributaries by the solid material transported and deposited, the morphological formative effects during floods, the reactivation of relict or ancient riverbeds, etc.; (II) anthropic, which refers to the implementation of all interventions aimed at regulating water exploitation and defending the watercourse, such as confinement, rectification, hydraulic works, mills, diversions, etc.

The analysis was carried out by examining historical sources, consulting archive documents, bibliographic material, cartographies, and data collected during the reconnaissance carried out by CNR IRPI (Research Institute for Hydrogeological Protection) staff over various decades of activity since the 1970s, when the research centre was established [47]. The data available online and the numerous aerial images photo-interpreted appropriately were also consulted, from which it was possible to draw up a summary of the transformations in the area.

To appreciate the fluvial variability, it was also necessary to consider the effects of the numerous flood events that have repeatedly affected the area. Remnant morphologies, such as abandoned meanders and areas of ancient floodplains, offer clues to past river dynamics. These morphologies can provide valuable information on historical climatic conditions and changes in land use. During floods, water currents increase their energy, causing intense erosion of the riverbanks and riverbed. This erosion leads to the removal of materials (sands, gravels, and clays) that can be washed downstream. At the end of the flood stage, sediments are deposited elsewhere, generating new geomorphological forms such as islands, bends, and meanders. Floods can lead to significant altimetric and lateral variation in the riverbed, with the creation of new channels or the abandonment of existing ones. This process is often accompanied by lateral migration of the river, particularly in stretches with bends and meanders. Floods can create temporary wetlands, which become habitats for many species of fauna and flora. These areas can remain for years after a flood, contributing to greater biodiversity.

Historical analysis has led to documenting the first major transformations of the river network of the Po, with a shift in the 12th century of the mouth from south to north in the Ferrara area (outside the examined area), and in the upstream stretch. The main levees and the “golena” (floodplain), artificial structures built to contain river water and prevent flooding, have had a significant impact on the geomorphological transformations of the Po River. These engineering interventions, carried out since the 17th century, have modified not only the river’s morphology, but also its ecosystems and hydrological regime, comprising the anthropic contribution element of the hydrological cycle [32]. Embankment structures and longitudinal hydraulic works (e.g., cliffs) have stabilised the course of the Po, reducing its natural width and limiting its ability to migrate laterally; this resulted in a decrease in the river’s dynamicity, with consequences for the formation and geometry of meanders and the processes of erosion and sedimentation.

The regularisation of the river course led to a general lowering of the riverbed and a change in the transverse profile of the river, influencing geomorphological processes, as was the case for other Italian watercourses [7,48,49,50]. By altering the riverbed morphologies, cross-sections have undergone profound variations, often making evaluations of flow rates and floodwater levels unreliable when comparing them analytically [51]. The construction of embankments has altered the sedimentary regime of the Po, with variation in the sectors in terms of storage and erosion [52], modifying the original geomorphological behaviour. The interaction between accelerated currents and rigid banks has contributed to greater bank erosion at the embankments, with consequent habitat loss and alterations in riparian ecosystems. The geomorphological transformations due to bank defences and embankments have also had repercussions on river ecosystems, not only along the Po River but also along its tributaries, which have had to adapt to the geomorphological variations in the main watercourse by altering longitudinal profiles [50]. Reductions in environmental variability and natural habitats have affected aquatic biodiversity as well as the lateral continuity of transported sediments, with a drastic reduction in tributary inputs (especially in the intra-alpine sections of the Po River basin and tributaries) [53]. The levees’ ineffectiveness, sometimes unexpected (through collapse, seepage, overflow, and failure), has historically also affected flood management [54]. Their presence has increased the vulnerability of the river system and exposed structures [55,56]. Climatic changes have made the management of embankments even more critical, requiring constant analysis of their effectiveness, also due to the increase in vulnerable areas [57,58,59,60,61,62,63,64,65].

3. Materials and Methods

3.1. Multiresource Thematic Database

For the retrospective geomorphological analysis, research was conducted in local historical archives, parish archives, and, most importantly, state archives, where both ancient and recent inventories were consulted in order to retrieve and select documentary resources, records, and maps spanning from the 16th to the 20th century. All of the catalogued data were integrated into a specially structured thematic database (DB). The FONTES research group is enhancing the detail of the recorded elements, thereby improving the effectiveness of queries to the aforementioned DB. Additionally, a specific QGIS plugin has been added for the insertion of catalogued materials, some of which have been used previously and will be used for future research. The references are the most recent archival and bibliographic models and standards. In terms of Italian cataloguing regulations, an important reference is the Guide to Catalogation (Italian National Library System, SBN), which provides a detailed definition of the descriptive elements and important guidelines regarding the treatment of historical cartographic resources. The FONTES project represents the latest activity in a series of research initiatives that have resulted in numerous published findings [66,67,68], and, most importantly, in the consolidation of interdisciplinary and transdisciplinary research networks.

The analysis of the documentary material revealed that not all historical maps could provide reliable or useful information regarding the river’s course during the represented period. The characteristics of individual maps depend primarily on the original purpose of the representation and the ability and interest of the cartographer to capture specific landscape features and transfer them to scale on the map. Another important aspect is the context in which the documents were produced, in addition to the expertise, role, and purposes of the producers and/or possible patrons [69]. These insights are essential for understanding the significance of the historical documents used in research, to avoid errors and misunderstandings in interpreting their contribution to knowledge [70].

The thematic DB has been populated with thousands of historical maps, and further document integrations are ongoing, related to resources stored at the CNR IRPI, which are currently being catalogued and reorganised. These constitute the knowledge base of the CNR IRPI, including archival documents, newspaper clippings, iconographic collections, historical maps, and terrestrial as well as aerial photographs. The process resulting from the structuring and implementation of the DB has allowed for a broader interpretation of geo-historical sources, fostering the development of different thematic reading keys (geographical, economic, geomorphological, etc.), which will be the subject of further specific ongoing research. The DB currently includes several generic and specific data entries; the goal of the DB is to provide a tool that incorporates the most recent archival and bibliographic models and standards (with particular attention to resource metadata and web interoperability), while also meeting the needs of the FONTES project. To provide a structured framework for this approach and to extend its intervention potential beyond the constraints of the three-year funding period, the Interuniversity Centre FONTES—Studies, Research, and Tools for the Understanding and Valorization of Identities and Territories was established, with the authors and their institutions as active members [18].

3.2. GIS Project

A substantial part of the documentary material was transferred, after appropriate georeferencing (including map rototranslations), as information layers into an open-source GIS project (QGIS software version 3.38.3, reference system WGS84/32N EPSG 32632), in which the river geometries represented in the historical cartographies and aerial images were transposed. This approach made it possible to analyse, albeit not continuously, over 400 years of riverbed variations in the Po River and its tributaries in the confluence sectors (Table 2). In fact, through a multi-temporal comparison, the morphological evolution of the alluvial plain and river area was reconstructed.

The geopolitical aspects of feudal and state borders, landscape transformations, and the roles of defence and mitigation structures in response to the Po River’s fluvial behaviour and the effects of flooding events, including the aggravation connected to the damage of embankment structures were examined. Using historical maps from the 16th century to more recent ones, the change in land use and the variations in the active riverbed over the centuries were highlighted. The analysis of the historical maps, found thanks to extensive research, interpretation, and selection, made it possible to highlight how the course of the Po and its confluences has changed over time. The cartographic work of Smeraldo Smeraldi, a cartographer and engineer who carried out his activities in the context of the Duchies of Parma and Piacenza, which consists of a number of topographies dated between 1580 and 1634, represented an important resource for the project [70,71,72,73,74,75]. The high level of geometric detail used by Smeraldi in his drawings provided functional cognitive tools at the time, representing the importance of topographies in the disputes and territorial annexation policies operated by the Farnese. In the present day, this feature has enabled the use of cartographies in cartographic design in a GIS environment, representing the oldest geometric element used for the representation of river geometries.

Equally significant for restitution in a GIS environment are the maps of the “Brioschi collection” at a scale of 1:15,000, drawn up for the Royal Commission to analyse the conditions of the Po after the flood of 1821 and 1853, chaired by Senator Francesco Brioschi. The Brioschi collection is unique in Italy for its technical characteristics and the beauty of its watercolour plates, which depict maps of the Po River basin in the stretch from Pavia to the Adriatic Sea. Another collection, consisting of 300 maps, is the ‘Po River Collection’, which includes maps, sections, profiles, and photographs of the river made between 1708 and 1926 [76]. These resources have both contributed to the reconstruction of the course of the Po River over the last two centuries.

For the purpose of representing fluvial elements within a GIS environment, as previously noted, historical drawings, maps, and iconographic sources were integrated with aerial photographs to support the interpretation of fluvial morphologies in more recent periods. Aerial imagery, available for the study area beginning in the 1950s, provides additional data on morphological changes, particularly in relation to alterations in meanders and riverbanks. Especially valuable are aerial images capturing flooded areas during major flood events, such as those of October 1977 [77], October 2000 [78], and 2024 [79], which have been digitised and georeferenced for integration into QGIS. The current configuration of the Po River has therefore been reconstructed through the integration of recent aerial photographs, satellite imagery, and data retrieved from regional and national web-based GIS platforms (Table 2).

Table 2. Main historical maps used for GIS project and analysis geomorphological fluvial variations.

Original Name	Description	Date	Source
P. Gozzi, Mappa dei territori rivieraschi del Po da Castelnuovo Bocca d’Adda a Brescello	Copy from the second half of the 18th century of a 1588 of map drawn by Cartographer and Engineer Smeraldi Smeraldo	1588	[80]
G. Cocconcelli, «Delineazione de’ Confini tanto controversi, quanto pacifici trà li Ducati di Parma, Piacenza e Guastalla e la Lombardia Austriaca»	Topographic map of the Po River, in the section between the Province of Pavia and Guastalla	1788	[80,81,82,83,84,85]
Topografia militare dei Ducati di Parma, Piacenza e Guastalla	Topographical maps of the Duchies of Parma, Piacenza and Guastalla, 1:28,800 scale	surveys 1820–1821	[80]
Carta del corso del Po dal Ticino al Mare	Map of the Po River course from Ticino to the Sea also known as “Brioschi Collection” 1:15,000 scale	surveys 1821 updated in 1853	[76]
Istituto Geografico Militare Italiano	Maps of National cartographic authority, 1:25,000 scale	1881–1888	[86]
CNR IRPI Archive	Maps of, 1:100,000 scale	1920	[47,86]
Po river basin images	Aerial photographs	1953,1960,1973,1977, 1980, and 1990	[77]
Technical Regional Italian Maps	Carta tecnica regionale (Regione Emilia-Romagna), scala 1:10,000	2000	[79]
Emilia-Romagna regional aerial photographs	Aerial Photographs	2011, 2019, and 2024	[79]
Autorità di Bacino distrettuale del Fiume Po Map	Lidar images an DTM	2005	[87]
Po river satellite images	Satellite images (SAR 2)	1992, 1996, and 2000	[78]
Corine Land Cover	Land-Use Lombardy and Emilia-Romagna regions	1853, 1976,1980, 1994, 1999, 2020, and 2021	[79,88]

Table 2. Main historical maps used for GIS project and analysis geomorphological fluvial variations.

Original Name	Description	Date	Source
P. Gozzi, Mappa dei territori rivieraschi del Po da Castelnuovo Bocca d’Adda a Brescello	Copy from the second half of the 18th century of a 1588 of map drawn by Cartographer and Engineer Smeraldi Smeraldo	1588	[80]
G. Cocconcelli, «Delineazione de’ Confini tanto controversi, quanto pacifici trà li Ducati di Parma, Piacenza e Guastalla e la Lombardia Austriaca»	Topographic map of the Po River, in the section between the Province of Pavia and Guastalla	1788	[80,81,82,83,84,85]
Topografia militare dei Ducati di Parma, Piacenza e Guastalla	Topographical maps of the Duchies of Parma, Piacenza and Guastalla, 1:28,800 scale	surveys 1820–1821	[80]
Carta del corso del Po dal Ticino al Mare	Map of the Po River course from Ticino to the Sea also known as “Brioschi Collection” 1:15,000 scale	surveys 1821 updated in 1853	[76]
Istituto Geografico Militare Italiano	Maps of National cartographic authority, 1:25,000 scale	1881–1888	[86]
CNR IRPI Archive	Maps of, 1:100,000 scale	1920	[47,86]
Po river basin images	Aerial photographs	1953,1960,1973,1977, 1980, and 1990	[77]
Technical Regional Italian Maps	Carta tecnica regionale (Regione Emilia-Romagna), scala 1:10,000	2000	[79]
Emilia-Romagna regional aerial photographs	Aerial Photographs	2011, 2019, and 2024	[79]
Autorità di Bacino distrettuale del Fiume Po Map	Lidar images an DTM	2005	[87]
Po river satellite images	Satellite images (SAR 2)	1992, 1996, and 2000	[78]
Corine Land Cover	Land-Use Lombardy and Emilia-Romagna regions	1853, 1976,1980, 1994, 1999, 2020, and 2021	[79,88]

For the analysis of relict river morphologies, digital terrain models (DTMs) are very useful, e.g., [89,90]. Lidar and satellite images were also used to analyse the section of the Po River examined [78,87]. The elaboration of the images through the QGIS software made it possible to consider only the geomorphological depressed areas of the terrain. Specifically, from the mosaic of the Po River DTM acquired in 2005 [87], 44 square tiles were selected (with an area of 4 km²) of the stretch of the Po River between the confluence of the Taro River and the Viadana Municipality. Considering that such a fragmented mosaic would not have allowed a uniform analysis, the tiles were merged using the QGIS process ‘Build Virtual Raster’, and the result was saved as a geotiff. The identification of the morphological traces of historical riverbeds imprinted in the river region, corresponding to relict morphologies of ancient Po River courses, cannot be directly realised on the DTM. This is because the difference in altitude between the upstream and downstream stretches, even if minimal, is sufficient to invalidate the extrapolation of fluvial morphologies with an altitude lower than the average terrain level. Therefore, in order to be able to locate the traces of relict, or obsolete, riverbeds, it was necessary to define the relative elevation model (REM). To do this, the median of the Po course at 2000 (the year closest to the year of the DTM acquisition) was taken, and through the GDAL GIS tool (Geospatial Data Abstraction Library) (points along geometry) process points were identified along the median, whose distance between one and the other coincides with the average width of the active riverbed. Once this punctual layer was obtained, through the ‘Sample Raster Values’ process, an ‘elevation’ field was attributed to each point, calculated thanks to the DTM. Then, using the ‘IDW Inter-polation’ process, a temporary DTM was created, with the same resolution as the source DTM, and, finally, using the ‘Raster Calculator’ command, the interpolated DTM was subtracted from the source DTM, thus obtaining the REM of the stretch of the Po between the mouth of the Taro River and Viadana. The creation of a REM, in this case a detrended DTM, makes it possible to recalculate the heights of the DTM by setting a fictitious value as the altimetric zero, which in this case coincides with the height of the median of the watercourse. In this way, the elevations identified by the REM will be relative to the watercourse. Next, the REM of the stretch of interest was polygonised by using the ‘Polygonise’ (raster to vector) command, setting an elevation accuracy of 1 metre. At this point, all polygons with a relative elevation of less than 10 metres were extracted and the polygon layer relating to the relict morphologies was identified.

This analysis was possible due to the ease with which the Po River in this stretch was able to affect low-resistance deposits. In practice, the riverbeds and forms “imprinted” on the fluvial area that have left depressed forms with respect to the country plane attributable to ancient riverbeds were highlighted. In this way, the most “formative” morphologies for the stretch under examination were considered, relating them to the territory occupied by the historical riverbeds whose planimetric course was reconstructed with the geomorphological analysis of historical maps, drawings, technical attachments, and area images. In this way, areas referable to ancient (or relict) river courses were highlighted. These geometries (in altimetric negative) were transformed into polygonal areas whose area and planimetric development could be defined. Each riverbed obtained from the geometric transposition obtained from the analysis of the maps and aerial images was subsequently analytically evaluated in relation to the morphologies of the river plain, in order to assess the extent of the variations in each period considered. Each historical course of the Po River was also compared to the morphology imprinted on the river plain, defined by the depressed footprint of the DTM previously described, in order to assess which riverbed was referable to a ‘formative’ flood. This term refers to a flood with ‘formative or dominant flow’, i.e., with a flow rate that is sufficiently frequent and energetic for determining the morphology of the riverbed [91].

3.3. Land Use

In response to the numerous flood events that affected the course of the Po River in the section examined, water management systems began to be implemented, including embankments and diversion channels. The construction of these works led to a significant change in the morphology of the river and its beds, reducing the frequency of floods but increasing erosion in existing beds. The earliest flood defence structures for settlements along the Po River appear to date back at least to the Etruscan period (6th century BC). During Roman times, and especially in the Middle Ages, efforts began to be made toward river canalization, leading to the development of significant levee systems, already documented by the 17th century. These structures were generally set back from the active river channel, partly due to the river’s wide meandering morphology; where the river’s course was more stable, levees were constructed closer to the channel. Behind these levees, low-lying areas with extensive marshlands persisted, which became the focus of targeted land reclamation works during the modern era, particularly under the Napoleonic regime. The system of flood defences and ongoing maintenance efforts aimed to protect both settlements and local agricultural and energy-related activities (such as floating mills). Nevertheless, flooding from the Po and its tributaries continued to challenge local populations well into the 19th century, with recurrent overflows ultimately prompting the newly unified Italian government to establish the Brioschi Commission. The embankment system succeeded in avoiding the effects of significant floods of the Po River in the Parma section, which instead caused numerous damages upstream of Cremona (e.g., flood events in 1907, 1917, and 1926) [12].

Morphological analysis shows how the floods caused variations in the profile of the riverbed and the increase in sediment volumes, modifying the geometry of the watercourses. The formation of new meander areas and bank erosion resulted from these events, affecting the river ecosystem. Embankments and other artificial structures built to contain river water and prevent flooding have therefore had a significant impact on the geomorphological transformations of the Po River [92]. The regularisation of the riverbed led to a lowering of the water level and a change in the river’s transverse profile, affecting geomorphological processes [7]. The transformations disrupted the use of the watercourse, which, for example, in Roman times was also used with large boats due to the greater extension and flow rate of the riverbed.

The originally extensive floodplain corridors facilitated greater lateral channel mobility and planform dynamics. Over time, these areas were progressively constrained to allow for intensified agricultural land use, including within confluence zones, in which historically agricultural practices had always been conditioned by the occurrence of wetland and marsh-like conditions. Sedimentation has concentrated in specific areas, creating new geomorphological forms, while other areas have suffered erosion [52].

The increase in urbanised areas in former river areas has also led to an alteration in the river environment. The expansion of urban areas and communication routes, including river crossings, has acted as a conditioning element for the river, which has had to adapt, altering its morphological structure. The land was examined in the context of anthropogenic transformations by means of the expansion of land uses reconstructed using a specific European cover classes database CORINE (Coordination of Information on the Environment) Land Cover (CLC) [79,88].

3.4. Flood Events in the Po River and Tributary Hydraulic Network in the Province of Parma

In the extensive lowland sector of the Po River, the most evident effects of fluvial geomorphological variations have been documented. The section under examination (A–B, Figure 1) is located in this context. Historical documents show that the Po River has experienced significant flooding over the centuries [12,93]. Disastrous events have profoundly affected spatial planning and urbanisation, leading to a series of crisis prevention and management measures. Among the oldest records of flooding of the Po River in the area under examination are the reconstructions of the Roman historian Titus Livius [94]. Titus Livius reports the floods of 204 and 180 B.C., which were followed by many others, e.g., the one of 589 A.D. that submerged entire areas, such as Brescello and Modena. In the centuries that followed, the Taro, Parma, and Enza tri-barren rivers also showed the devastating effects of their floods, causing riverbanks to break, victims, the destruction of built-up areas, and widespread flooding. In the last decade of the 13th century, at least two flood events of the Po River changed the morphology of the landscape. Equally devastating were the dozens of events that occurred between the 16th and 18th centuries (Figure 3 and Figure 4) [80,94], such as those of 1705 and 1706, of which the chronicles report numerous victims [26].

The 19th century also saw significant flood events that profoundly affected this sector of the Po Valley. During this period, increasing urbanisation led to changes in land use and agricultural practices that affected the water regime. Among the major floods, events of the 19th century Po River documented in the Emilia-Romagna region occurred in November 1801 and subsequently in 1840 and October 1868, with floods that devastated towns along the river and caused serious damage to structures and crops. Historical documents highlight the social and economic impacts of these events, with thousands of people forced to evacuate their homes. The 20th century saw a further intensification of human activities and an increase in the construction of hydraulic works, which had a substantial impact on the behaviour of the Po River. In particular, the events of 1917 and 1926 were followed by catastrophic floods in 1951 and, to a lesser extent, 1953, which affected large areas of the Po Valley. The 1951 floods were among the most devastating in history, with a high number of victims and considerable economic damage [12].

The November 1951 flood event is considered the most significant due to the extent of the flooded areas and the persistence of the flooding of the Po River, with considerable hydrometric levels reached due to the concomitance of flow rates at the crest, even from the main tributaries [95,96,97]. The levels reached the embankments on 14 November 1951, which, at various points, saw their stability jeopardised due to the hydrostatic load exerted by the mass of water. In the provinces of Parma and Reggio Emilia, a number of embankment breaks occurred (due to regurgitation/backflow, infiltration, and syphoning), which led to widespread flooding as the days passed, especially towards the towns of Boretto and Brescello; the submerged areas on the right bank of the Po reached an extension of about 130 km² [98]. In the province of Rovigo, located further downstream, the banks were instead completely overtopped, with the collapse of large portions of the defence system. The maximum extent of the flooding occurred on 25 November, with about 10,000 km² submerged; the water flowed for about two months [98]. These events led to the implementation of more-structured water management policies.

In the 1960s and 1970s, the Italian Government initiated a series of hydraulic engineering projects, including the construction of dams and lamination basins. These works had a direct impact on the river’s ecology, altering sediments and water flow, while relict morphologies were largely destroyed by these structures. However, in September 1972 and October 1977, two flooding events occurred that again inter-occupied the Po River stretch in the Parma area.

In the 21st century, new challenges related to climate change have become evident, with increasingly intense and frequent flood events [47]. Significant flood events occurred in 2000, 2009, 2023, and 2024, each of which caused severe damage to infrastructure and raised concerns about the capacity of water management systems to cope with the new challenges. The land management practices analysis in relation to the flood patterns and to the fluvial relict morphologies were used to track the environmental change. The confluences with the Taro, Parma, and Enza tributaries played a decisive role in flood dynamics and morphological changes in the territory, introducing geomorphological complexity in the analysed area [46,99]. The Taro River, with its more mountainous basin, contributes to high flows during heavy rainfall. Although the Parma River has a smaller basin, its runoff characteristics contribute to rapid changes in the level of the Po River. The Enza River, the main tributary of the Reggio Emilia province, has historically had a significant impact, with erosion and sedimentation modifying the banks of the Po over the years.

By comparing the major flood events since the 20th century, we can highlight the variations in levels and hydraulic flow rates that have been recorded at the various instrumented sections, for which a bathymetric survey of the riverbed was previously carried out to reduce the error of comparing very different sections (

Table 3. Historical data on the hydrometric level related to major floods of the Po River in 20th century [76,100,101,102,103]. The floods levels are referred to level of hydrometric zero. The water level monitoring stations is shown in Figure 1 (Piacenza and Cremona are outside the focus area, Casalmaggiore is near to C monitoring site, and Boretto is near to B monitoring site). N.A.: not available.

Hydrometric Level Monitoring Station	Elevation of Hydrometric Zero	1917 Flood Level (m)	1926 Flood Level (m)	1951 Flood Level (m)	1977 Flood Level (m)	1994 Flood Level (m)	2000 Flood Level (m)	2024 Flood Level (m)
Piacenza	42.16	9.00	9.63	10.25	7.62	9.98	10.50	6.14
Cremona	34.34	5.41	5.20	5.95	5.12	5.87	6.15	2.40
Casalmaggiore	23.49	6.54	6.37	7.64	6.64	7.58	8.01	4.96
Boretto	19.95	7.72	N.A.	8.59	7.65	8.43	9.06	5.70

) (Piacenza, Cremona, Casalmaggiore, and Boretto site monitoring; see Figure 1) [76,100,101,102,103].

With this in mind, historical levee routes were also analysed [76,104,105] in conjunction with some more recent flood events. From the location of the routes (transformed into shapefiles in the aforementioned project in a GIS environment), it was checked whether the propagation of the floods during the routes took place in directions facilitated by the presence of relict or obsolete riverbanks, and to identify which river course predisposed the runoff dynamics.

4. Results

4.1. Database: Multithematic Spatial Interpretation and Knowledge Sharing

The historical analysis enabled the collection of several thousand documents, primarily cartographic materials, maps, graphical representations, cross-sections, and technical details (e.g., embankments, retaining structures, and boundaries), which have been digitally reproduced and catalogued in a database (DB). This database contains detailed archival and technical metadata, which can be queried using multiple search keys. It constitutes the first multithematic product focused on a fluvial territory analysed over a timespan of approximately 450 years. The database encompasses administrative, boundary-related, and geographical themes, allowing for in-depth investigation into the historical–political and geomorphological evolution of the examined riverine area. Significant insights have emerged regarding the area’s exposure to geo-hydrological risk, particularly in relation to its inherent susceptibility to flood events, even in zones where mitigation and containment measures have been repeatedly implemented. The database, which remains open to continuous updates, will be made publicly accessible upon the completion of the PRIN FONTES project [18].

4.2. The Geomorphological Transformations of the Riverine Area

From the transposition of the historical riverbeds into the specifically created GIS project and their transformation into polygonal shapefiles (Figure 5), together with the restitution of the relict morphologies (as indicated in Section 3.2), it was possible to analytically compare certain morphological elements.

All the polygons identifying the Po riverbeds in the different years are comparable along the same stretch between points A and B. The Po riverbed for the period considered, 1588–2019, firstly maintains (16th century) a slightly sinuous monocursal course with large islands, especially at the confluences of the main tributaries, and numerous depositional bars. At the end of the 18th century, the Po River drew more-pronounced meanders with widespread smaller islands than in the previous period. During alluvial events occurring in the second half of the 1700s, or more likely due to geomorphological interference induced by the positioning of anthropic interventions, meander cuts occurred, leading to a shortening of the river stretch and locally to loops and meanders, with fluvial islands and depositional bars. In the first half of the 19th century, the Po River in the section examined developed a monocursal course with elongated islands, alternating with deposit bars; erosive processes in the concave banks were accentuated in the more curved sections. Some sectors outside the main riverbed remained active, where these were not confined by the embankment structures. During the 20th century, the narrowing of fluvial morphologies became inexorable, with the progressive reduction in river islands, which increasingly lost their connection to the surrounding active channel, further constricting the channel width along several reaches.

The stretch of embankment upstream of the town of Casalmaggiore (in the centre of Figure 5) fixed the course extremely rigidly for several decades. The embankment itself suffers numerous damages during significant flood events, as witnessed by historical chronicles. The morphology consolidates in a monocursal trend, with islands recurring continuously until the 2000s. Since the 21st century, the narrowing of the riverbed throughout the entire stretch is very evident, with significant losses in width.

In order to assess the extent of anthropic transformations, an area of one square kilometre from the current median of the Po River was therefore considered in the GIS project for both banks (defined as ‘Buffer 1 km’). Within this area, bounded upstream and downstream by the beginning and end sections (A and B, in Figure 1), the land-use transformations obtained from the comparison of the 1980 and 2021 CLCs were considered (Figure 6). Only for the fluvial part of the territory in the Emilia-Romagna region was comparison extended to the earlier period, with data referring to the land use of 1853, allowing for reconstruction of a wider period (1853–2021) (Figure 7). For hydraulic and flood mitigation works, reference was made to the current layout [87], which, however, does not take into account hydraulic works that have been removed or destroyed over time.

4.2.1. Fragility of the Embankment System Facing Relict Morphologies

The analysis of the relict morphology, obtained from the negative survey of the 2005 DTM [87] and transformed into a polygon with an extension between A and B, made it possible to verify which riverbeds between the 16th and 21st centuries were most decisive in modelling the fluvial territory of the stretch of the Po River. This morphology, which includes the summation of the significant transformations for the river region considered, reaches an extension of approximately 57 km² (Figure 8).

Each polygon corresponding to the individual riverbeds in the different years was superimposed on the relict morphology by extracting the overlapping area. It was intended that a greater overlap (expressed as a percentage) would correspond to a greater persistence of river morphology. Obviously, the presence of hydraulic works has heavily conditioned the Po fluvial regimes. As a result, the greatest overlap was observed for the 1588 riverbed (with 42% overlap) (

Table 4. Percentage of areal overlap of riverbeds on relict morphologies (from DTM).

Year	Area (km2)	Overlapping (%)
1588	24.1	42.1%
1788	22.4	39.1%
1820	21.5	37.4%
1853	16.3	28.4%
1888	18.7	32.6%
1920	19.0	33.1%
1953	21.1	36.8%
1960	17.1	29.8%
1973	20.2	35.3%
1980	19.6	34.2%
1990	10.6	18.5%
2000	16.1	28.2%
2011	12.5	21.9%
2019	11.3	19.8%

).

The relict fluvial morphology has further enabled the identification of specific levee breaches that, over different flood events, have directed overbank flows along paleo-channels and morphologically inherited flood pathways embedded into the geomorphic structure of the floodplain (Figure 9 and

Table 5. List of levee breaches that are referable to apparently relict or obsolete river geometries. The first column lists the codes of all the documented levee breaches, which are also shown in Figure 9. The second column indicates the years corresponding to specific channel patterns included within a 5 m buffer from the identified levee breach point.

Levee Breach Code	Year of Channel-Pattern Included in Levee Breach Point 5 m Buffer
1801_034010_dx1	1801
1801_034010_dx2	1801
1810_019057_sx1	1810, 1821, 1853, 1888, 1920, 1960, 1973, 1980, 1990, 2000, 2011, 2020
1839_034010_dx1	1839
1855_034010_dx1	1855
1855_034010_dx2	1855
1857_034021_dx1	1857
1857_034021_dx2	1857
1857_035006_dx1	1857
1868_034010_dx1	1868, 1888, 1920
1868_034010_dx2	1868, 1888, 1920
1868_034021_dx1	1868
1868_034021_dx2	1868
1951_034010_dx1	1951
1951_034021_dx1	1951
1982_019052_sx1	1588, 1821, 1953, 1982
1982_019108_sx1	1588, 1821, 1888, 1982
1982_019108_sx2	1588, 1821, 1982
1982_019108_sx3	1588, 1982
1994_019052_sx1	1788, 1994
1994_019052_sx2	1788, 1994
1994_019052_sx3	1588, 1853, 1994
1994_019052_sx4	1588, 1821, 1994
1994_019108_sx1	1588, 1821, 1994
1994_034010_dx1	1994
1994_034021_dx1	1821, 1994
1994_034021_dx2	1980, 1994
1994_034021_dx3	1588, 1994
1994_034021_dx4	1588, 1994
1994_034021_dx5	1994
2000_019061_sx1	1588, 2000
2000_019108_sx1	1588, 1788, 2000
2000_019108_sx2	1588, 2000

).

The floodwater spread on the plain following the paths of the numerous abandoned channels that are linked to the Po River and represent a potential flood hazard in the plain outside the flood corridor. Despite historical hydrographic variations in the Po River floodplain, similarity exists between the modes of levee breaching and floodwater spreading. The localisation of levees, related to the channel morphodynamics and the abandoned channel system, can provide vulnerability indications of the breaching-prone sites. These morphologies, in fact, correspond in the sub-bed and subsoil to river deposits with draining characteristics typical of ancient riverbeds, with specific solid transport capacity and therefore corresponding deposits, which may condition the propagation of any floodwaters outside the embankment system. In this sense, with a view to preventing flood risk, it is advisable to constantly verify the effectiveness of the embankment system, especially where there are evident relict riverbeds outside the embankment system that, in the case of an embankment failure, can condition the flow directions and cause further damage following flood events [97].

4.2.2. Reduction in Riverine Areas

Since the 21st century, the narrowing of the riverbed observed by the GIS project throughout the examined section is very evident, with losses in width. For each reconstructed historical riverbed, widths were measured in specific and significant sections, which were also used in the past for comparisons between different flood events. From these, important considerations regarding planimetric variations at reference sites were obtained (

Table 6. Riverbed widths of the Po River at different times in representative sections (A, B, C, and D, in Figure 1).

Year	Riverbed Width (km)
	A	B	C	D
1588	5.5	0.9	1.3	1.2
1788	1.9	1.2	1.1	2.1
1821	1.7	0.6	1.0	2.1
1853	1.3	0.7	0.5	0.8
1888	2.7	0.9	0.5	1.3
1920	2.7	1.0	0.8	1.1
1953	1.4	0.4	1.1	1.2
1960	1.5	0.7	1.5	1.1
1973	1.6	0.4	1.4	1.3
1980	1.6	0.4	1.3	1.4
1990	1.7	0.2	1.4	1.5
2000	1.8	0.4	1.0	1.5
2011	1.8	0.4	1.2	1.3
2019	1.9	0.3	1.3	1.2

, Figure 10).

This analysis for the period 1588–2019 shows, first of all, a reduction in the active river surface of about 66% (section A, Foce Taro locality; see Figure 1), including river morphologies (islands and depositional bars), an elongation of the river shaft of about 14% due to the increase in riverbed sinuosity, and, in a strikingly conspicuous manner, planimetric variation (Figure 5). The reductions in riverine areas also reflect a variability in the geometry of the Po riverbed, which is connected to the capacity, intensity and frequency of erosion, transport, and sediment deposition of the watercourse. This aspect is very significant for comparing two or more flood events and attributing greater or lesser severity/intensity to their effects. It seems evident, however, that in the floods of the 20th century, the Po River manifested increasingly faster discharge propagation times to the various sections due to a limitation of the river course (Table 3). A comparison of the sections reconstructed based on the official bathymetric data [76] shows extreme variability of the riverbed at some sections considered significant (e.g., the Viadana and Casalmaggiore monitoring sites) (Figure 11).

In the event of a flood, as seen in some of the most significant floods of the 20th century, the sections occupied by the waters were very large, spanning the entire available area contained between the embankments. In particular, flood dynamics highlighted the need for greater spaces to exclude the compromise of the embankment structures themselves and the reactivation of relict or obsolete riverbeds. For example, the aerial survey conducted after the October 1977 flood event (Figure 12) [77] made it possible to calculate the area inundated by floodwaters, which amounted to approximately 40 km² within the A–C reach alone. The georeferenced image, along with the digitised geometries transposed into a GIS environment, enabled a comparison between the extent of the 1977 flood and that of historical flood events. The resulting geometries demonstrated that nearly the entire 1977 flood area corresponded to the floodplain extent recorded in 1588, which covered more than 45 km².

Similar considerations were made with the areas flooded in later years. For all flooded areas, an overlay was made with the morphologies obtained from the DTM (Figure 13 and

Table 7. Overlapping of the areas occupied by the 20th century floods on the relict morphologies for section A and C only.

Year	Area (km2)	Overlap with Historical Morphology (%)
1977	40.4	61.3%
2000	62.4	43.7%
2024	21.3	54.4%

).

4.2.3. Migration of the Tributaries Confluences in the Po River

From the graphic restitution of the riverbeds in the various periods, it was possible to analyse the position of the confluences of the three main tributaries on the right (Taro, Parma, and Enza) (Figure 14). In this regard, the planimetric displacements were highlighted through the position of the coordinates of each point in the GIS environment. From the observation of the map, they appear to migrate laterally in an extremely variable manner (Figure 15) [106,107]. This is comparable for the different graphical representations of historical riverbeds (Figure 14). The variability of inputs into the Po River, the main receptor, and of deposits in the confluence sectors has profoundly influenced the river’s behaviour in the downstream section, even for tens of kilometres from each confluence.

5. Discussion

This contribution presents an examination of Po River variations and the inputs into them of the Taro, Enza, and Parma watercourses, according to a chronology covering more than five centuries (1588–2024). The documents of geo-historical interest consulted and analysed made it possible to depict the river territory over a sufficiently significant period, during which numerous more- or less-formative alluvial events occurred from a geomorphological point of view. Within the framework of the transformations observed over the last two centuries, qualitative and quantitative insights were possible in relation to documented relevant changes.

For the 20th century, important considerations on flood dynamics were possible thanks to the retrieval of specific documentation, especially that from aerial and satellite images, with which it was possible to make comparisons with historical situations. Remnant morphologies, such as abandoned meanders and areas of ancient floodplains, offered cognitive elements of past river dynamics. The research showed that historical morphologies could provide valuable information on past climatic conditions and land-use changes. In addition, the reconstruction of spatio-temporal patterns made it possible to highlight extreme hydrological events, such as floods and hydrological droughts, e.g., [108]. The study of geo-history through close collaboration between different disciplines has been directed towards the management of river regions over time. The integrated use of historical cartography, aerial photographs, indirect data, spatial models (DTMs), and satellite images [78] is therefore an essential contribution to understanding the morphological dynamics of rivers. For the preceding centuries, such data could be inferred from maps created for different purposes than those presented here: cadastral surveys, land registers, and large-scale topographies might convey valuable information, regardless of the level of geometric accuracy. By combining historical data with current information, it was possible to create dynamic maps of morphological changes. Further details could be derived from more-detailed DTMs [109,110,111,112,113], the integration of other techniques (e.g., photogrammetry and multispectral analysis) that could also provide information on vegetation cover (and thus also on land-use changes), and changes in the hydrological regime [114]. These technologies make it possible to monitor river variations in real time and assess the impact of extreme events, such as floods.

The reference field of this study is that of knowledge and mitigation of hydrogeological risk in areas of high anthropic and natural transformation. The application horizon is aimed at the public engagement relationship between academic research and land managers. The research interest therefore turns not only to theoretical–methodological reflections and related case studies, but also to the in-depth study of methodologies and tools to support decision-making systems on the part of land managers, particularly in relation to the knowledge and management of cultural and environmental risks in river regions. In addition, the current debate on sustainable water resource management has broadened, agreeing on the importance of preserving historical morphologies and floodplains to preserve biodiversity and mitigate the impact of floods. This aspect, from a regulatory point of view, has led to important instruments such as the Flood Risk Management Plans [82], which represent the reference tools of the District Basin Authorities of the Po River for mapping the areas of flood hazard as well as risk and identifying the measures to be implemented to reduce the harmful consequences on human life, territory, cultural heritage, and economic–social activities. These plans are being implemented to also address current challenges related to changes in the climate regime and critical points of hydraulic networks, e.g., [87].

The reconstruction of flood scenarios on the basis of integrated historical documentation (aerial photographs, archival documents, period images, etc.) and their comparative analysis shows that it is possible to recognise the natural and anthropic factors that have favoured the triggering of water propagation currents on the ground plane and thus influenced the direction and expansion of flooding on previously identifiable morphologies. The use of GIS and remote sensing technologies has revolutionised the monitoring of river morphologies, making it possible to obtain detailed data on dynamic changes in the riverine areas. Using all of the resources mentioned, it is possible to define survey strategies and methods for assessing the fragility of existing riverbank systems and the mitigation of damaging effects in light of the activation/reactivation of ancient routes, as shown by studies on riverbank routes and the effects of past floods.

Possible applications derived from the information obtained through research such as that presented may include (i) the identification of preferential flow paths during significant flood events (also polluted floods); (ii) the prediction of potential river breaches where relict flow channels intersect weak levee structures that do not provide adequate containment; (iii) the recurrence analysis of damage to levee systems, including the identification of segments most susceptible to failure; (iv) the identification of currently inhabited or utilised areas located within zones historically occupied by the river system (including through the analysis of historical toponyms); (v) the recognition of variations in fluvial patterns associated with hydraulic regimes different from those observed today; (vi) the detection of morphological anomalies corresponding to former tributary confluences; (vii) the assessment of aquifer behaviour in relation to the position of the main river channel; (viii) the interpretation of surface water persistence in areas located at a considerable distance from the current river course, as a result of the presence of relict fluvial morphologies that have been partially reworked or modified by anthropogenic activities. The main limitations in conducting research of the type presented are related to the temporal continuity and reliability of the available sources, their accurate interpretation and historical contextualization, the ability to integrate different data (typology and source), and the historical significance of the area under investigation.

The PRIN FONTES project, within which this work is situated, has led to the development of an interdisciplinary methodology for identifying issues, events, and interventions that have occurred over the past five centuries and are thus documented through cartographic materials and reports. Starting with the transcription of individual relevant elements into a database, a georeferenced database has been created in which each item can be queried within a corpus of over 2300 maps resulting from this research and supplemented by the digitised materials from the extensive CNR-IRPI archive. This tool will soon be available for free online access.

6. Conclusions

The floods of the Po River, which had a profound impact on the Po Valley for thousands of years, highlight the complexity of the interactions between natural factors and human activities. The analysis of historical riverbeds and relict morphologies offers important insights into the river’s behaviour and the need to adopt sustainable water resource management and flood risk mitigation strategies. Only through an integrated approach that considers ecological, social, and engineering aspects is it possible to address future flooding challenges and promote community resilience along the Po River.

Within the framework of these considerations, the importance of not limiting the geographical analysis to the spatial data found emerges, but they are examined with a geo-historical approach. The cartographic document must be examined in the entire process of conception, production, and representation. This approach allows geo-historical research for risk mitigation to provide a higher degree of reliability and interpretive responsibility. The realisation of spatial data consultation systems (such as databases and WebGIS), even of complex and multidisciplinary origin, through reasoned databases and shared platforms, allows geographic, patrimonial, administrative, territorial, statistical, and economic evaluations of great importance, also in support of river mitigation actions. The current challenges in the field of the mitigation of damaging effects must pass from a correct re-interpretation of the territory (with punctual evaluations that can vary, for example, from the relocation of anthropic structures to the decommissioning of embankment systems or the reinforcement of defensive elements of high fragility, also highlighted on a historical basis), as suggested by the new management initiatives.

Cognitive tools, such as those described above, can lead to more appropriate land management choices, greater awareness on the part of resident populations, and better sharing as well as knowledge of the “man-river” environment. The creation of predictive models based on historical and current data offers important tools for geo-hydrological risk mitigation, the sustainable management of water resources, and the conservation of river ecosystems.

The important hydraulic reclamation activity of the Po Valley, which had already started in pre-Roman times, led to the possibility of using large areas of alluvial plains and abandoned river channels for building purposes. Urbanised areas have moved closer and closer to the riverbanks, leading to a false perception of safety offered by the mitigation and defence solutions implemented in addition to the expansion of urban spaces erroneously considered safe, making ever-larger areas of territory vulnerable.

Among the results achieved, a contribution derives from the investigation of routes, embankment systems, and river behaviour during a flood event: it is appropriate to assess the flood risk caused by the propensity of embankment breakage in relation to the increased vulnerability along the areas close to the linear development of the embankments for the probability of flood hazard and expansion according to the reactivation dynamics of relict or obsolete riverbeds. Resident communities also play a crucial role in monitoring and protecting historical morphologies, as they are often the first to be affected by flooding. Traditional knowledge, integrated with modern technologies, can therefore contribute to more effective and resilient management. Resident communities, particularly the most vulnerable ones, also play a crucial role in monitoring and protecting historical morphologies. It is at this scale that a greater awareness of the centuries-long dynamics that have shaped the relationship between the river and communities can contribute to identifying changes and making more-informed decisions in environmental and hydraulic planning, as well as in defining more resilient collective identities capable of effectively integrating advanced technologies, geo-historical knowledge, and local traditions for risk management.