Rainfall as triggering factor of slope movements in southern Italy: Montalbano Ionico case record

The aim of this paper is to define the role of rainfall on landslides in Southern Italy by using hydrological/statistical approach. Among the villages affected by slope movements, Montalbano Ionico has been selected as example of shallow landslides. Its most recent landslide evolution is characterized by low intensity phenomena that can be classified as retrogressive and widening composite rapid earth slide - earth fall. Their high frequency and the caused damage imply a high risk degree. This study confirms how complex and how very diverse are the phenomena that govern the effects of rainfall upon slope stability. Nevertheless, geomorphological analyses focus on the importance of some previous instability marks to predict the future slope evolution by landslides; when these marks exist, the weight of unusually heavy cumulative rainfall on the successive landslide collapse is resulted 30% - 40%.