Analysis of damaging hydrogeological events in a Mediterranean region (Calabria)

Damaging Hydrogeological Events (DHEs) are periods of severe weather conditions affecting wide areas for several days, and causing mainly damaging landslides and floods. In order to characterize the DHEs, we analysed the historical series of the events that affected a Mediterranean region (Calabria, southern Italy) throughout 92 years of observation. Depending on their magnitude, we classified the events as: major catastrophic, catastrophic, extraordinary and ordinary. In winter events, damaged areas and damage were greater than those resulting from the other seasons. Nevertheless, the majority of the events took place in autumn, when, in addition to landslides, a relevant percentage of flash floods and floods also occurred. Results also show that the frequency of major catastrophic and catastrophic events has decreased since 1971, and that, in recent decades, Calabria has suffered from damaging effects even though rain did not reached extreme characteristics. In fact, the duration of triggering rain, the maximum daily rain of the events and the out coming frequency of the high return period of rain show a decreasing pattern throughout the study period. As to what concerns the damaging phenomena, landslides were identified as the most frequent in every season and in every type of events,, the eastern side of the region was the most frequently and heavily damaged. According to literature, the trend of number of victims per event is also decreasing. The proposed analysis can be applied to different study areas in order to assess the relative magnitude of DHEs and their evolution throughout the years. The classification criterion can be useful to compare different events for either scientific or insurance purposes, and to identify the typical rainfall-damage scenario of a study area.