Geomorphic impact of prolonged rainfall in a Calabrian stream basin (Italy)

The present paper reports a brief description of geomorphic effects induced in a Calabrian stream basin (T. Pagliara) by the extreme meteoric event which occurred in winter 1972-73. A hydrological model was applied in order to outline the relationship between rainfall and main landslide activations in the study basin. The combined analysis of both observed geomorphic effects and triggering rainfalls allowed us to evaluate the hazard related to a hypothesised meteoric event comparable to that of winter 1972-73. Some quantitative elements are also given in order to provide a starting point for implementing an "instability scenario" for the study area. Among the results, the heaviest widespread landslide activations in Pagliara basin only occurred when heavy rainfall, lasting 3-5 consecutive days, reached threshold values (more than 200 mm) at the end of prolonged periods of rain (about 900 mm in three months).