Weather-induced landslide activity in clayey slopes: modelling for the design of site-scale early warning system

Based upon both phenomenological and numerical analyses, current landslide activity in clayey slopes has been found to be recurrently prompted by the soil–vegetation–atmosphere interaction taking place in the very topsoil layers. This interaction can cause transient seepage down to large depth in the slope, resulting in significant variations of pore water pressures and available strength with time at both very shallow depth and large depth below the water table, i.e., variation of the slope equilibrium, defined as slope–vegetation–atmosphere interaction. Such interaction may be the triggering factor of the activity of either shallow landslides or deep slow landslide bodies in clayey soils. This paper reports the results of a research insight into both the pore water pressure and the safety factor variations determined by the soil–vegetation–atmosphere interaction at the ground surface of slopes made of clayey turbidites, location of seasonal acceleration of deep landslide displacements and of shallow landsliding. The analyses are carried out making reference to a representative slope and are validated against field data. The results of the numerical analyses are shown to succeed in reproducing the current weather-induced activity of the landslide bodies, so that the adopted modeling represents a tool to be used within early warning systems for the mitigation of the landslide risk in the slope scenarios of reference in the paper.