Analysis of landslide triggering conditions in the Sarno area using a physically based model

Abstract. Rainfall is recognized as a major precursor of many types of slope movements. The technical literature reports both study cases and models of landslides induced by rainfall. Subsurface hydrology has a dominant role since changes in the soil water content significantly affect the soil shear strength. The analytical approaches used are very different, ranging from statistical models to distributed and complete models. The latter take several components into account, including specific site conditions, mechanical, hydraulic and physical soil properties, local seepage conditions, and the contribution of these to soil strength.

This paper reports a study using a complete model, named SUSHI (Saturated Unsaturated Simulation for Hillslope Instability), to simulate the role of subsurface hydrology in rain-induced landslides, on a case of great interest both in terms of its complexity and its severity.

The landslide-prone area in question is located in Campania (southern Italy), where disastrous mudflows occurred in May 1998. The region has long been affected by rainfall-induced slope instabilities, which often involve large areas and affect many people. The application allows a better understanding of the role of rainfall infiltration and suction changes in the triggering mechanism of the phenomena. These changes must be carefully considered when assessing hazard levels and planning mitigation interventions regarding slope stability.