DSGSD developed along the Cenischia-Nizza tectonic system in the Rodoretto Valley (Western Alps)

The Rodoretto Valley, a left tributary of the Germanasca Valley, is located in the Western Alps (NW Italy) from 1200 m to 2900 m a. s. l. This area is shaped by glaciers, and subsequently by watercourses, in the Greenstone and Schist Complex (Penninic Domain), near the N-S tectonic contact with the Dora Maira Massif. The Rodoretto Valley is extensively involved by deep seated gravitational slope deformation (DSGSD), responsible for developing of many gravitational morpho-structures (as doubled ridges, minor scarps, trenches) and landslide accumulations (Forno et al.,2012; 2013). The deep-seated gravitational slope deformation effects on the Quaternary sediment facies and distribution were particularly investigated. The main conditions that favoured the DSGSD evolution are: - high relief energy; - strong shaping by glaciers; - great deepening by watercourses; - bad geomechanical conditions of the bedrock, characterized by a high fracturing degree. Research was conducted through the traditional geological survey, with high detail, and using also geomatics techniques in order to produce a geological and morphological map. UAV (Unmanned Aerial Vehicle) flight was carried out for DSM (digital surface model) images generation, combined with topographic surveys of terrain employing total station and GNSS (Global Navigation Satellite System) instruments for georeferencing the images. These geomatics techniques had greatly helped in the detailed geological mapping in largely inaccessible areas. The combined geological and geomatics surveys lead to suppose that the critical geomechanical conditions of bedrock are strictly related to the crossing of two major tectonic discontinuity systems with N-S (Cenischia-Nizza System) and NNW-SSE trend respectively, suggesting a link with the active tectonics. The distribution of many structural and morphostructural elements suggests the presence of sliding surfaces connected to the DSGSD, that can probably lie below the current Rodoretto Valley floor, as a result of the great deepening of the main Germanasca Valley. DSGSD susceptibility is a mix of predisposing factors reducing the slopes stability. The major factors that influence the DSGSD processes are represented by slope gradient and rainfall aggressiveness (Taddia et al., 2015). The knowledgeof the interaction among the predisposing factors may provide powerful information about the location of likely future landslides phenomena, essential for land planning. Forno M.G., Lingua A., Lo Russo S. & Taddia G. 2012. Morphological Features of Rodoretto Valley Deep-Seated Gravitational Slope Deformations. Amer. Journ. Environ. Sci, 8(6), 648-660. Forno M.G., Lingua A., Lo Russo S., Taddia G. & Piras M. 2013. GSTOP: a new tool for 3D Geomorphological survey and mapping, Eur. Journ. Remote Sensing, 46(1), 234-249. Taddia G., Gnavi L., Piras M., Forno M.G., Lingua A. & Lo Russo S. 2015. Landslide susceptibility zoning using GIS tools: an application in the Germanasca Valley (NW Italy). In: Engineering Geology for Society and Territory, 2 (Landslide Processes), Springer International Publishing, 177-181.