Topographic and Pedological Rainfall Thresholds for the Prediction of Shallow Landslides in Central Italy

In Italy, rainfall induced shallow landslides are frequent phenomena that cause casualtiesevery year. At the national and regional scales, empirical rainfall thresholds can predict theoccurrence of single or multiple rainfall-induced shallow landslides. In this work, weupdated a historical catalogue listing 553 rainfall events that triggered 723 landslides inthe Abruzzo, Marche and Umbria regions, central Italy, between February 2002 and March2011. For each event, the rainfall duration (D) and the cumulated event rainfall (E)responsible for the failure are known, together with the exact or approximate location ofthe landslide. To analyse the influence of topography and soil characteristics on theoccurrence of rainfall induced shallow landslides, we subdivided the study area in threetopographic divisions, and eight soil domains. We analysed the (D, E) rainfall conditionsthat resulted in the documented shallow landslides in each topographic division andregional soil domain, and we defined ED rainfall thresholds at 5 % exceedance probabilitylevel for the two subdivisions. We expect that the new topographic and pedologicalthresholds will contribute to forecast shallow landslides in central Italy, and in areascharacterized by similar morphological and soil settings.