Hydrogeological analyses of the Champlas du Col deep-seated landslide (NW Piemonte, Italy)

Mountainous regions, due to their geomorphological features, are particularly prone to ground instabilities. In recent decades, there has been growing recognition of the role of climatic factors, such as heavy rainfall, in the occurrence and movement patterns of landslides in these areas, which are also vulnerable due to the presence of population centers and infrastructure. Slow-moving landslides, such as complex-type landslides or Deep Seated Gravitational Slope Deformation (DSGSD), which involve large slope volumes, are highly dependent on seasonal rainfall patterns and snowmelt. The Susa Valley (in the NW of the Piedmont Region, Italy) is a clear example in this context. The displacement rates are influenced by changes in groundwater pressure, which are closely associated with net rainfall and snowmelt process. Therefore, the reconstruction of ground instability scenarios includes the development of a hydrogeological analysis aimed at improving the comprehension of climate impacts on water resources and, consequently, slope movements. As a first step, the collection of piezometers or monitoring mountain springs data, along with the implementation of suitable statistical analyses, enables the detection of groundwater fluctuations. The influence of these parameters on the increase in displacement trends, recorded by in-situ instruments (e.g., inclinometers), is further investigated by correlating the landslide body displacements with seasonal variations in spring water levels and precipitation inputs. Within this framework, it is useful to define the main infiltration pathways and to identify the conditions responsible for soil saturation that affect slope stability by performing a numerical analysis. In conclusion, the current research makes a significant contribution to the interpretation of ground instability in mountainous regions, emphasizing the role of predisposing factors.