Landslide triggering and local rainfall thresholds in Bradanic Foredeep, Basilicata region (southern Italy).

It is recognised that a lot of the landslides occurred in the Mediterranean region are triggered by short intense storms. Due to its geological, geomorphological and climatic settings, the Bradanic Foredeep (Basilicata region) is affected by the widespread presence of landslides. The main objective of this paper is to identify the empirical triggering thresholds in Bradanic Foredeep and to investigate the role of antecedent rainfall. Using a variety of information sources, we have compiled a catalogue listing 97 rainfall events linked to landslides triggering in the investigated area. For each event in the catalogue, the exact or approximate location of the landslide and the time or period of initiation of the slope failure is known, together with information on the rainfall duration D, and the rainfall mean intensity I , that have resulted in the slope failure. The local rainfall threshold for the study area has been established using the statistical Frequentist approach. The comparison with regional thresholds proposed for other Italian regions has revealed that the Bradanic Foredeep thresholds are lower; which is probably due to the different quality of rainfall dataset. In fact, all the previous threshold have been evaluated starting from hourly data, while for the Basilicata region only daily data are available. Throughout this study we could not identify a significant correlation between antecedent rainfall and critical rainfall.