## 2 Material and Methods  
### Geological Setting  
The study area comprises the Po Plain, which represents the surface expression of a syntectonic sedimentary wedge framed between the Alps to the north and the Apennines to the south (Figure 1) [14]. The Po plain is drained by the Po River, the longest Italian river (652 km) that flows eastward from the western Alps into the Adriatic Sea (Figure 1). The Po River drainage basin is about 75,000 km\({}^{2}\)[15] and includes about 141 tributaries emerging from the surrounding Apenninic and Alpine chains. These tributaries deliver water and sediment to the Po River from south and north, respectively (Figure 1). In the western sector of the Po drainage basin, including the Western Apennines, Western and CentralAlps, crystalline-metamorphic and ophiolite complexes crop out extensively (Figure 1). On the other hand, Southern and Eastern Alps are mostly characterized by carbonate (limestone and dolostones) outcrops (Figure 1). The majority of the sediment delivered by the Apenninic rivers derives from Cretaceous to Pliocene sedimentary successions dominated by chaotic clays, turbidites (sandstone/marl alternations), and sandstones [16]. Important outcrops composed of evaporites (i.e., gypsum) from the Gessoso-Solfifera Formation are also present in the Apennines [17] (Figure 1).  
The Po Plain can be subdivided into minor alluvial sectors as the easternmost Venetian-Friulian Plain (VFP in Figure 1), which was formed by alluvial systems external to the Po drainage basin [18]; the Lombardy-Piedmont Plain (LPP in Figure 1), west of the Garda Lake; and the Emilia-Romagna Plain (ERP in Figure 1), south of the Po River (Figure 1).  
The Po Basin is filled with Plio-Quaternary sediments, up to 8 km-thick in the main depocenters south to the Po River, and thin northward [19; 20]. Beneath the Venetian plain, thicknesses are about 1 km, and less than 500 m in the Friulian and Lombard areas [21]. The sedimentary infill is characterized by a shallowing-upward tendency, from Pliocene deep-marine to Quaternary shallow-marine and continental deposits [22; 23]. Along the Po Basin, Late Quaternary strata show a vertical cyclic change in fluvial-channel stacking pattern (i.e., amalgamated fluvial-channel bodies vs. individual fluvial-channel deposits within mud-dominated strata) reflecting the alternation of glacial-interglacial periods during the Middle-Late Pleistocene [24]. Beneath the coastal plains, equivalent glacio-eustatic evidence on the stratigraphic architecture is documented by the cyclic alternation of vertically-stacked coastal to marine (interglacial) and continental (glacial) deposits [25; 26; 27; 28]. The Holocene succession, in the Po coastal plain consists of a transgressive-regressive sedimentary wedge of coastal to marine sediments overlying fully alluvial Pleistocene deposits [29]. By contrast, the proximal and more superficial portion of the Po Plain is mainly characterized by modern river courses associated with abandoned fluvial channels and ribbon-shaped fluvial ridges, commonly elevated several meters above the adjacent floodplain [30].  
Large alluvial fans, up to 3000 km\({}^{2}\), composed of Late Pleistocene fluviogalacial deposits crop out extensively in the VFP and LPP [31; 32]. Their piedmont sectors are generally characterized by gravel deposits, whereas the distal portion is generally composed of finer-grained materials. Alluvial fans of minor extent are also present in the ERP, close to the Apenninic margin [33; 34]. These alluvial fans mainly consist of amalgamated gravel bodies that thin out toward more distal sectors, where gravels are progressively replaced by fluvial channel sands and floodplain silty-clays [35].