Performance of I-D Thresholds and FLaIR Model for Recent Landslide Events in Calabria Region (Southern Italy

During the period 2008–2010 heavy and persistent rainfall events induced thousands of shallow landslides and hundreds of deep-seated landslides in Calabria Region (Southern Italy), with more than 2,000 crisis points and damages related to about 94 % of the municipalities. These events are comparable, or even worse, with those occurred in the 50’s and in the early 70’s. In this context, the performance of mathematical models, which are used for the Early Warning System of Calabria Region, is evaluated. In details, Intensity–Duration (I–D) thresholds for several temporal aggregations (hourly and multi daily) of rainfall heights and the hydrological model named FLaIR (Forecasting of Landslides Induced by Rainfall, Sirangelo and Versace 1996) are considered. Moreover, the use of a regional approach for these models was also tested, which is particularly useful when it is necessary to predict the triggering of landslide movements in vast areas where there are concerns not only about the reactivation of pre-existing movements, but also activation of new movements whose exact location is unforeseeable and for which there is no available past information. The obtained results highlight a good model performance, in particular for FLaIR, which can be considered as a general case of I–D rainfall thresholds (Capparelli et al. 2009) and it is characterized by a more flexibility, as it takes into account the real pattern of rainfall heights along the time, and not average values of temporal intensity