## 4 Regional Scale Analysis
### Hazard Indicators
The final hazard map is obtained by combining in an arithmetic average of the different indicators (Figure 4). As shown in the maps of the individual indices previously mentioned, the areas with the highest hazard values are located as follows:  
* In the northwest along the border with France, in Val Veny, Val Ferret, and Valle di La Thuile (Courmayeur area, Mont-Blanc, Col d'Arguerey, Aiguille-des-Glaciers, Aiguille-de-Bionnassay, Dent-du-Geant);
* In the northeast along the border with Switzerland, near the Matterhorn and Monte Rosa groups;
* In the area of the mountain ranges to the south, along the steep slopes of Valgrisenche, Val di Riemes, Valsavarenche, and Val di Cogne. However, other high hazard areas are located along the central part of Valle d'Aosta, with hazard scores of up to 26 out of 41 (maximum value), due to a combination of lithological types susceptible to instability, landslides that have already occurred in the past and are likely to recur, the absence of vegetation, and the slope facing south. The obtained result is very useful to make a comparison with the existing documentation included in the Piano Territoriale Paesistico--PTP (Territorial Landscape Plan), approved on 10 April 1998 through regional law n. 13. Valle d'Aosta has produced, for the entire regional territory, a map of geological and hydraulic hazards on a scale of 1: 100,000, as reported in Figure 5.  
Figure 4: Aggregated hazard value: glacier melting landslide susceptibility map. The map was created through QGIS (v. 3.26.0) software, employing the data outlined in Table 1.  
With regard to the protection against hydrogeological risks and instabilities, the PTP adopts regional law n. 32 of 1996, which identifies four classes of areas, with different degrees of hydrogeological hazards:  
1. [label=(0)]
2. Extensively disrupted areas susceptible to further evolution to a very high hazard level, including large landslides, avalanche areas, active debris layers, active alluvial conoids, and floodplains; unstable areas with very high propensity to disruption; minor flooding areas, with very high probability of hydrogeological events; and the probability of hydrogeological events;
3. Unstable areas, with a locally high level of hazard: areas that are floodable during exceptional events and sectors of slopes that are more vulnerable during hydrological emergencies due to the potential for landslides, especially of surface soils;
4. Areas with moderate instability and a low hazard level: floodable areas with secular frequency and areas characterized by local instability phenomena for potential landslides during hydrological events;
5. Areas that do not present particular problems from the point of view of hydrogeological hazard: flat valley bottom territories and morphological terraces free from instability phenomena. A comparison of the two mappings reveals a similarity of results, even though the present methodology introduces additional parameters beyond those of the Piano Territoriale Paesistico. The proposed methodology aims to specify hazard levels on \(10\times 10\) metre \"pixels\", derived from the resolution of the starting datasets for the individual indicators presented in the previous section. In addition, the work carried out analyses on a specific type of risk, which is the risk of slope instability, while the existing documentation of Figure 5 refers to hydrogeological risk in general. Figure 5: Geological and hydraulic hazard map included in Piano Territoriale Paesistico. Data from the Geoportale of Valle d’Aosta region.