Further hydrological analyses on landslide initiation in the Sarno area (Italy)

In a wide area of Campania, characterised by mountain ridges covered by pyroclastic deposits, landslides occur after intense rainstorms that follow an accumulation of a certain amount of prestorm seasonal rainfall. Instabilities begin as soil slides, and evolve to debris avalanche-flow along steep slopes. This study extends the hydrological analyses carried out by FIORILLO & WILSON (2004) on these landslides. Further 10-years of rainfall records allow to verify a previous hypothesis on the soil moisture accumulation into the soil. Analyses have been focused in the Sarno area (P.zzo d’Alvano), where a high-elevation rain-gauge is available since 1998, which allows also to compare data with lowelevation rain gauges. Analyses show that numerous large-scale debris flows induced by the May 1998 storm depend heavily on the antecedent rainfall distribution and on the soil moisture storage characteristics.