## 2 Materials and Methods
### Selected Landside Causal Factors  
The causal factors identified for this analysis were 7, some topographic and dem-derived, such as the aspect, slope and TWI (Topographic Wetness Index), the other climatic such as the analysis of extreme precipitation, then the geological one related to lithology, and finally two satellite factors, the CORINE land cover (CLC) and NDVI (normalized difference vegetation index). Ten dip directions were considered to calculate aspect, in order to assess whether there is a particular exposure that statistically is more likely to trigger landslide movements, The appearance data have been reclassified into the following classes:  
* Flat (0\({}^{\circ}\)),
* North (0-22.5\({}^{\circ}\)),
* Northeast (22.5-67.5\({}^{\circ}\)),
* East (67.5-112.5\({}^{\circ}\)),
* Southeast (112.5-157.5\({}^{\circ}\)),
* South (157.5-202.5\({}^{\circ}\)),
* Southwest (202.5-247.5\({}^{\circ}\)),
* West (247.5-292.5\({}^{\circ}\)),
* Northwest (292.5-337.5\({}^{\circ}\)), and
* North (337.5-360\({}^{\circ}\)). The classification of the exposure was certainly very detailed with subdivisions according to the wind rose every 45\({}^{\circ}\) of inclination; however, it was interesting to have a more precise differentiation, also for future analyses. As for the slope, it was grouped into four groups from 0\({}^{\circ}\) to 16\({}^{\circ}\), from 16\({}^{\circ}\) to 25\({}^{\circ}\), from 25\({}^{\circ}\) to 35\({}^{\circ}\) and higher than 35\({}^{\circ}\). Geologically, due to the characteristic friction angles of each debris, there is a certain dependence on the inclination of the topography, while the division into classes has been borrowed from other international research, which has shown a differential landslide triggering capacity for the specified values [42]. The TWI is an index used to measure how local topography controls local hydrological processes and shows the spatial spread of surface saturation  
Figure 3: Model flow diagram. and soil moisture, in fact the following algorithm must show the impact of the local terrain on drainage [43]:  
\[TWI=\ln\biggl{(}\frac{A}{\tan\beta}\biggr{)} \tag{6}\]  
where \(A\) is the specific catchment area of a portion of land, where \(\beta\) is the slope angle. It is common scientific knowledge that especially in the case of the landslide movements evaluated in this study, the imbibition of debris can increase the weight of the debris and allow the activation of a movement. The following classes created on the basis of the TWI were chosen:  
* 0-2,
* 2-4,
* 4-6,
* 6-8,
* 8-10,
* 10-12, and
* 12-23. The classes were chosen using homogeneous differences between one and the other, with the last one being extended because for many of the values belonging to it, it is not sufficiently represented. To spatially assess land use, the CLC updated to 2018 was used, thus with the measurements obtained from Sentinel-2, with the first level dividing the study area into the following homogeneous territories:  
1. Artificial Surfaces,
2. Utilized Agricultural Areas,
3. Wooded Territories and Semi-Natural Environments,
4. Humid Zones (that are not present in the study area), and
5. Water Bodies. The geology of the area, as in any susceptibility analysis, is very important, but equally fundamental is the aggregation between the various formations, on homogenous groups, in order to obtain a certain significance that would be lacking, especially over large areas where there may be many formations, due to the extreme fragmentation. The lithotypes have been grouped into the following hydrogeological classes [44]:  
* Deposits;
* Limestones, flinty limestones, subordinately marls and clay marls;
* Marls, clay marls and marly limestones;
* Sandstones, marly clays, subordinately conglomerates;
* Shales and marls encompassing calcareous, marly limestone and arenaceous bodies.