Monitoring of hydrological parameters for the identification of shallow landslides triggering: a case study from Northern Italy

Long-term continuous hydrological monitoring of slope susceptible to shallow landslides is a fundamental tool for analyzing the main soil hydrological behaviors and identifying the conditions which lead to shallow failures. In this work, a case study of a long-term hydrological monitoring, in the period 2012–2015, of a slope susceptible to shallow landslides located in Oltrepò Pavese (Northern Italy) is presented. The soil is characterized by different hydrological behaviors along the year, due to rainfall trends. The main triggering mechanism develops in wet seasons (winter and spring), when soil approaches saturated conditions, for uprising of a perched water table at about 1 m from ground surface, in consequence of the most intense rainfalls (about > 60 mm in 48 h). Slope stability analysis shows that unstable conditions (safety factor < 1.0) are reached in correspondence of similar events. Safety factor trends allow to catch unstable conditions on the basis of both water content and pore water pressure.