Controlling factors for deep-seated gravitational slope deformation in the Aosta Valley (NW-Alps, Italy)

Deep-seated gravitational slope deformation (DSGSD) is a common and widespread type of large slope instability in the Alps. In the Aosta Valley region in NW Italy, DSGSDs occupy at least 13.5% of the regional territory. In this study, regional distribution analyses have been coupled with local detailed geological and geomorphological surveys of individual phenomena to detect the controlling factors, deformation processes and evolution stages of DSGSD. Data and maps from field and remote-sensing investigations have been supported by drill data and geomechanical and hydrogeochemical analyses from project studies for hydroelectric plants and tunnels. Several phenomena related to DSGSD have been studied thoroughly: gravity-induced stresses, tectonic-metamorphic setting, morphostructural relations, glacial and periglacial morphodynamics, recent tectonic evolution, hydrogeological conditions and karst phenomena have been generically indicated as controlling factors. In the studied area three of the controlling factors were crucial in differentiating the form and evolution of DSGSDs: deep dissolution, surface tectonics, and tectonostructural setting. They are presented as possible end members of a classification scheme for DSGSDs.