## 5 Results and Discussion  
### The Characterisation of the Croso Stream Slope  
In Figure 5, the results of the index of connectivity map elaboration (a), and of the IFFI database analyses (b) are reported. The structure of the Croso stream hydrographic basin is clear in terms of sediment connectivity in Figure 5a, where the Index of Connectivity map is reported. In the IC map the distinction between the areas characterised by low connectivity (green) and the area characterised by high connectivity (red) is evident. A high connectivity area is represented by the head of the Croso stream basin where several debris transport channels intersect the detachment niches of diffuse rockfalls/topplings (18, Figure 5b and in Table 2). Low connectivity areas correspond to the accumulation areas that act like a sink, as the terrace on which the Alpe Ciamporino is located. From this area, towards down-valley, the high connectivity conditions recur and concentrate along minor streams and small V-shaped valleys located in correspondence of weakness zones (e.g., 8, Figure 5a, Table 2). Hence, the debris stored within the Alpe Ciamporino sink is transported along the Croso stream, together with the debris produced along the incision, along the Croso stream during the heavy rainfall events. At the confluence with the Caiirasca stream, debris flow events feed the alluvial fan (Figure 5a). According to the IFFI database, the structure of the slope is quite articulated and characterised by different kinds of geomorphological instabilities as reported in Figure 5a and Table 2. As mentioned before, up-valley to the study area, the Caiirasca gorge is deeply incised as attested to by the intense erosive action of the Caiirasca stream, which the Croso stream flows into. \begin{table}
\begin{tabular}{c c c c c c c c} \hline
**ID** & **IFFI** & **IFFI** & **Landslide** & **Activity** & **Lithology** & **Land** & **IFFI** & **Area** \\
**(Figure 5b)** & **Idfrana** & **Sub-Id** & **Classification** & **Degree** & **1:250,000** & **Use** & **Method** & **(m\({}^{2}\))** \\ \hline
1 & 10300266- & 00 & D-R/T & A7R/S & Lp & Ng & P & 41562 \\
2 & 10300267- & 00 & D-R/T & A/R/S & Lp & Ng & P & 8880 \\
3 & 10300271- & 00 & Rf/T & Q & Lp & Ng & P & 52058 \\
4 & 10300274- & 00 & Rf/T & Q & Lp & Ng & P & 48159 \\
5 & 10300275- & 00 & Rf/T & Q & Lp & Ng-Bt & P & 47248 \\
6 & & 01 & DSGD & n.d. & Lp-m-ms, Ve, Ao & Ng-Bt-Cf & P & 1892974 \\
7 & & 02 & C & Q & Lp & Ng & P & 200507 \\
8 & & **03** & E/Df & **Q** & **Vs** & **Ng-Cf** & P & **116899** \\
9 & & 04 & E/Df & Q & Ao & Cf & P & 5534 \\
10 & & 05 & E/Df & Q & Lm-ms, Ve & Ng & P & 20161 \\
11 & **10300484-** & 06 & E/Df & Q & Lm-ms, Ve & Ng & P & 21952 \\
12 & & 07 & E/Df & Q & Lm-ms & Ng & P & 1528 \\
13 & & 08 & E/Df & Q & Lm-ms & Ng & P & 5945 \\
14 & & 09 & C & Q & Lm-ms & Ng & P & 3779 \\
15 & & 10 & D-R/T & A/R/S & Ve & Ng-Cf & P & 5860 \\
16 & & 11 & D-R/T & A/R/S & Ve & Ng-Cf & P & 11262 \\
17 & 10300497- & 07 & D-R/T & A/R/S & Ao & Cf & P & 58294 \\
18 & 10310431- & 00 & D-R/T & A/R/S & Lp & Br-Ng & Ha & 739041 \\
19 & 10350258- & 00 & E/Df & n.d. & Vs & Cf & Ha & 9018 \\ \hline \end{tabular}
\end{table} 
Table 2: Landslides located along the investigated slope and included in the IFFI database (_Activity degree codes_: A = Active; R = Reactivates: S = Suspended; Q=Quiescent; n.d. = not determined; _Landslide classification codes_: D-R/f/F = Diffuse rockfall/toppling; Rf/T = Rockfall/toppling; DSGD = Deep Seated Gravitational Deformation; C = Complex; E/Df = Earth/Debris flow; _Lithology_: Lp = Lebendun paragneis; Lm-ms = Lebendun marble and micaschists; Vc = Valais calcshists; Ao = Antigorio ortogneis; _Land Use codes (CLC Corine Land Cover 2012 Level IV)_: Ng = Natural grassland; Bt = Broadleeves trees; Cf = Coniferous forest; _IFFI Method codes_: P = Photinterpretation; Ha = Historical archives). The Croso stream incision affected by debris flows is depicted in bold characters.