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 casualties every year. At the national and regional scales, empirical rainfall thresholds can predict the occurrence of single or multiple rainfall-induced shallow landslides. In this work, we updated a historical catalogue listing 553 rainfall events that triggered 723 landslides in the Abruzzo, Marche and Umbria regions, central Italy, between February 2002 and March 2011. 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 of the landslide. To analyse the influence of topography and soil characteristics on the occurrence of rainfall induced shallow landslides, we subdivided the study area in three topographic divisions, and eight soil domains. We analysed the (D, E) rainfall conditions that resulted in the documented shallow landslides in each topographic division and regional soil domain, and we defined ED rainfall thresholds at 5 % exceedance probability level for the two subdivisions. We expect that the new topographic and pedological thresholds will contribute to forecast shallow landslides in central Italy, and in areas characterized by similar morphological and soil settings.