Assessment of shallow landsliding by using a physically based model of hillslope stability

A model for the simulation of shallow landsliding triggered by heavy rainstorms is analysed and discussed. The model is applied in two mountainous catchments in the Dolomites (Eastern Italian Alps): the Cordon catchment (5 km^2) and the Vauz catchment (1.9 km^2), where field surveys provided a description of hydraulic and geotechnical properties of soils and an inventory of landslide scars is available. The stability mapping procedure, which is similar to that proposed by Montgomery and Dietrich (1994 Water Resources Research 30: 1153), combines steady-state hydrologic concepts with the infinite slope stability model. The model provides an estimate of the spatial distribution of the critical rainfall, which is the minimum steady-state rainfall predicted to cause instability. The comparison of the landslides observed in the study basins with model predictions shows that the distribution of critical rainfall obtained from the model provides a surrogate for failure initiation probability as a function of topographic location.