The role of geographic and seasonal factors and land cover change on empirical rainfall thresholds in Italy

In Italy, the prediction of rainfall-induced shallow landslides is a fundamental aim for civil protection purposes. In fact, severe events in the past caused economic damage and loss of human lives. For the purpose, we have investigated the rainfall conditions responsible for the occurrence of shallow landslides in Italy. Our work focused on the definition of empirical rainfall thresholds for their use in national landslide warning systems. The thresholds are based on the statistical analysis of past rainfall conditions that have resulted in landslides. However, the rainfall conditions that have resulted in landslides in the past may vary in the future due to climatic changes (i.e., changes in rainfall intensity and frequency, and patterns of the triggering events) and to landscape changes (i.e., land use and land cover changes). We have studied a catalogue of 1980 rainfall events that have resulted in 2407 shallow landslides in Italy from 1996 to 2012, and we investigated how the triggering rainfall conditions and the thresholds vary depending on geographical, seasonal and land cover factors.