Combined approach for hillslope hydrogeological assessment, in rainfall-induced shallow landslides prone area

Agricoltural fields in steep terrains can be affected by several problems, such as shallow slope instabilities, triggered during very intense thunderstorms or prolonged rainy periods. These phenomena can provoke severe damages to vineyards, with a general loss of fertility and biodiversity in the soil horizons. It becomes fundamental a multidisciplinary characterization of the slopes where agricultural fields are cultivated, to assess the effects of hydrogeological conditions in the probability of occurrence of slope instabilities, starting from the hydrogeological assessment. An integrated method, combining geotechnical characterization and geophysical surveys is proposed. At this purpose two experimental test sites, in Italian Northern Apennines (Oltrepo Pavese), with different geological and geomorphological characteristics, were chosen. From one side geotechnical and physical characterization of first soil horizons were achieved through field data collections, performing 2-meters depth trenches and collecting soil samples for each horizon along the trenches verticals. From the other side resistivity models of the first subsoil were performed through different electrical resistivity tomographies (2D-3D), calibrated and interpreted with the soil profiles derived from trenches. Finally, resistivity variations were correlated to soil horizons geotechnical parameters to perform hydrogeological conceptual models of the first soil horizons.