## 5 Results and Discussion
### The Characterisation of the Croso Stream Slope
According to IFFI and SIFraP sources ([29,43] and later review), in the Piedmont Region, at least 1230.8 km\({}^{2}\) (4.8% of the territory) are exposed to Hazard 3 and Hazard 4 categories. The most recent data (2020) include, in the whole Piedmont region, a record of 36787 inventoried landslides of which 3553 (9.66%) are slow earth/debris flow movements and 3859 (10.49%) are fast earth/debris flow movements, as those occurring within the Croso stream hydrographic basin (8-13; 19 in Table 2). The calcschists represents the lithotype characterised by the highest Landslide Susceptibility Index (>35%) of the whole Piedmont territory [56]. In the IFFI system, the nested-to-each-other landslides are grouped according to a main ID (2 nd column; Table 2), but the single landslide body could be distinguished using the sub-ID (3 rd column; Table 2). In general, along the investigated slope there are landslides related to different typologies: A1) simple geometry landslides that can be mapped  
Figure 5: Sediment connectivity and hydrogeological instabilities within the Croso stream basin. **(a)** the _Index of Connectivity_ map with channel network as target elaborated according to [40] using the DTM 5 m resolution; **(b)** the alluvial fan (source [[http://webgis.arpa.piemonte.it/geoportale/](http://webgis.arpa.piemonte.it/geoportale/)]([http://webgis.arpa.piemonte.it/geoportale/](http://webgis.arpa.piemonte.it/geoportale/))) and landslides retrieved from the WMS of the IFFI–Italian Landslides inventory (source ttp://www.progettoiffi.isprambiente.it/cartografia-on-line/ recently moved to [[https://idrogeo.isprambiente.it/app/](https://idrogeo.isprambiente.it/app/)]([https://idrogeo.isprambiente.it/app/](https://idrogeo.isprambiente.it/app/))) (for numbers refer to Table 2). Background courtesy of Environmental Systems Research Institute (ESRI) DigitalGlobe & GeoEye (GIS User commonly; [[http://microsites.digitalglobe.com/arcgis/](http://microsites.digitalglobe.com/arcgis/)]([http://microsites.digitalglobe.com/arcgis/](http://microsites.digitalglobe.com/arcgis/))). with a proper polygon, because wider than 10000 m\({}^{3}\) (1-5; 17-19, Figure 5a; Table 2); B1) complex geometry landslides that, as mentioned before, can be connected each other by a common factor and that are distinguished by using the sub-ID (6-16, Figure 5a; Table 2). As in this case, the Deep Seated Gravitational Deformation (DSDG; 6 in Table 2) is combined with other types of landslide. In Table 3, the analysed debris flow is categorised with the IFFI ID 10300484-03 (8 in Figure 5a). It is part, together with others (6-16 in Figure 5a), of a complex system including related to the DSGD (6 in Table 2) and involving a significant part of the slope where the San Domenico village is built. The analysed debris flow incision is located within the stripe of calcschists of the Valais Unit (Vc in Table 2 Figure 2a), foliated carbonate rocks quite degraded that, as mentioned before, are characterised, at a regional level, by the highest Landslide Susceptibility Index [56]. More in detail, along the stream a fault puts in contact the orthogneiss (Ao in Table 2), in a very foliated facies, on the left hydrographic side, with the carbonate facies of the Lebendun Unit (Lm in Table 2), on the right hydrographic side. Along the stream, cataclasites rocks are recurrent, representing a potential weakness zone. Moreover, the detachment niche is located at the edge of the glacial terrace of the Alpe Ciamporino (Figure 6b), where a thickness of several meters of glacial deposits covered by continue natural grasslands are present. Here, the dendritic pattern of the stream changes into a single channel stream that incises the glacial deposits making them unstable and contributing to the feeding of the debris flow. The Croso stream debris flow is the only landslide occurrence along the investigated slope that is provided of a \"IFFI second level\" form.