Heavy Rainfall Triggering Shallow Landslides: A Susceptibility Assessment by a GIS-Approach in a Ligurian Apennine Catchment (Italy)

In recent decades, the Entella River basin (eastern Liguria) has been affected by severalrainfall events that induced widespread shallow landslides and earth flows on the slopes; roads,buildings, structures and infrastructure suffered extensive damage due to the instability processes. Inthis paper, a GIS-based approach for analyzing and assessing a simplified landslide susceptibilityin the Entella River catchment is presented. Starting from landslide information mainly providedfrom newspaper articles and unpublished reports from municipal archives, we performed a series ofcomparative analyses using a set of thematic maps to assess the influence of predisposing natural andanthropic factors. By evaluating the statistical distribution of landslides in different categories, weassigned weighted values to each parameter, according to their influence on the instability processes.A simplified, reproducible, but effective approach to assess landslide susceptibility in the study areawas performed by combining all predisposing factors. The resulting scores in proneness to slopeinstability classes may be used to generate a simplified landslides susceptibility map of the catchmentarea which would be easy to regularly update every time a rainfall event that is able to trigger shallowlandslides occurs; this would provide a useful tool for local authorities and decision makers foridentifying areas which could potentially be affected by instability processes, and would help indetermining the most suitable measures in land-planning and landslide risk management