Rainfall intensity-duration thresholds for triggering shallow landslides in the Eastern Liguria Riviera (Italy)

The Eastern Ligurian Riviera, including the famous Cinque Terre, is frequently hit by heavy rainfall, which often induces shallow landslides and floods, causing damage and sometimes death. In this context, the assessment of the rainfall thresholds for shallow landslides initiation is very important in order to improve forecasting and to arrange efficient warning systems. With this purpose, a detailed analysis of the main rainstorms was carried out. The hourly rainfall recorded from 1967 to 2006 was analysed and compared with the occurrence of shallow landslides. Critical threshold curves were defined, in terms of duration and intensity, applying statistical techniques (logistic regression) in order to separate rainfall events that induced failures and events that did not. The rainfall thresholds obtained in this work were compared with the local and regional curves proposed by various authors. The results of this analysis suggest that in the study area landslide activity initiation requires higher amount of rainfall and intensity than elsewhere.