Comparison of statistical techniques for shallow landslide rainfall thresholds definition: a case study in Eastern Liguria (Italy)

The Eastern Ligurian Riviera (ELR, Italy) is frequently hit by rainstorm, which often induces shallow landslides causing damage and sometimes death. With the aim of determining the Intensity–Duration (ID) rainfall thresholds for the shallow landslide occurrence, the main rainfall events recorded from 1967 to 2006 were analyzed and classified in events inducing Shallow landslides (Sh) and event that did not trigger shallow landslides (NSh). ID thresholds were defined determining the lower limit of Sh events above which shallow landslides occurred and separating Sh from NSh events. The quantile regression was used in the first approach, while the logistic regression method was applied in the second one. The ID thresholds were validated using the rainfall events recorded in ELR from 2008 to 2014. A contingency table was created and contingencies and skill scores were computed. The ID thresholds obtained for the ELR can provide a guidance to set up shallow landslide warning systems and plan emergency actions.