## 4 Results
### Deep-Seated Gravitational Slope Deformations  
We compared the ground velocity map obtained through the GPOD-SBAS processing to the DsGSD phenomena present in the area of investigation, according to the IFFI (Italian Landslides Inventory) catalogue [88], and found a good correlation between deforming areas observed and the occurrence of DsGSD phenomena. We performed this comparison making use of Envisat results (both ascending and descending orbits), which present the best coverage of the VDA study area and a higher number of targets with respect to the ERS-1/2 results. Considering the ascending orbit, the inventoried DsGSDs included within the track considered are 179, and only 44% present targets inside, of which 25% present more than ten targets. Considering the descending orbit, 191 DsGSDs inventoried are included within the track considered; in this case, 35% of these phenomena present targets inside, of which only 19% present more than ten targets (Table 3). Moreover, the highest coherent target density for the east face-oriented DsGSD cases in ascending orbit, and for the west face-oriented DsGSD cases in descending orbit was observed. Two specific examples are reported and illustrated in Figures 8 and 9. The first example is the Beauregard DsGSD, located in the southwest portion of the region, while the second is the Quart DsGSD, located in the middle portion of the principal valley. The Beauregard DsGSD is an extended phenomena, going from 1700 m a.s.l., close to the valley bottom, up to 2900 m a.s.l. in the northern sector, corresponding to its main scrap. In [89], a non-homogeneous deformation pattern of this phenomenon is described, with the upper part \begin{table}
\begin{tabular}{c c c c c} \hline  & **DsGSD** & **Number of DsGSD** & **Number of DsGSD** & **Number of DsGSD** \\  & **(from IFFI)** & **(within the Track)** & **Covered by Targets** & **with >10 Targets** \\ \hline ENVISAT Ascending & & 179 & 79 & 44 \\ ENVISAT Desending & & 191 & 66 & 36 \\ \hline \end{tabular}
\end{table} 
Table 3: Summary of the number of deep-seated gravitational slope deformations (DsGSDs) inventoried in the IFFI project covered by targets generated by the GPOD-SBAS process. Figure 7: Surface velocities measured along the satellite LOS for the ERS-1/2 dataset in ascending orbit for the time period from June 1995 to May 2000. The **light blue** polygons correspond to the present glaciers. presenting the highest displacement rates, and a slow and constant deformation along the basal portion of the phenomenon. Exploiting our results (Figure 8a), we noted a good density of the target distribution, higher than that in other DsGSDs. The target distribution mainly covers the upper-northern and the central sector, while no targets were revealed in the southern part and in general at the DsGSD toe, where only a small basal portion of the landslide close to the dam structure is covered. The distribution of the targets is influenced by the distribution of bedrock outcrops: in the area covered by grassland or woods, the number of targets is very poor. Figure 8: (**a**) Mean deformation velocity map of the Beauregard DsGSD case study, for Envisat ascending dataset. (**b**,**c**) Time series corresponding to the targets signed by the **white** dots in the map. In general, we notice a good agreement between our results and the hypothesized kinematic domains presence. In fact, it is possible to identify two distinct portions presenting different LOS velocity values for the observed period: (i) the upper sector, corresponding to the main scarp and constitute by two sub-domains belonging to the DsGSDs (reported in the IFFI project), present velocities ranging from \(-1.04\) up to \(-0.5\) cm/year, while (ii) the basal sector present the lowest LOS velocity, with a range variable from \(-0.4\) to \(-0.2\) cm/year.