Physically-based regional landslide forecasting modelling: Model set-up and validation

In this work, the HIgh REsolution Slope Stability Simulator (HIRESSS) model was applied to predict the occurrence of shallow landslides on a regional scale. HIRESSS is a physically based distributed slope stability simulator for analyzing the occurrence of shallow landslides during a rainfall event. The modeling software consists of two parts: hydrological and a geotechnical. The hydrological model is based on an analytical solution of an approximated form of the Richards equation, while the geotechnical stability model is based on an infinite slope model that accounts for unsaturated soil conditions. The model was applied in the Aosta Valley region, located in the northwest of the Alpine chain. The Aosta Valley is highly susceptible to landslides, especially shallow, rapid landslides and rockfalls. The geotechnical and hydrological characteristics of the slopes were recorded in two field measurement campaigns at 12 measurement points. To account for the effects of vegetation on landslides the soil reinforcement due to the presence of roots was also taken into account. The model was applied in back analysis for an event that affected the Aosta Valley in 2009, triggering several fast shallow landslides. In this work the model setup and the validation of the model outcomes are described.