Landslide inventory and rockfall risk assessment of a strategic urban area (Palermo, Sicily)

This study concerns the assessment of the rockfall risk for two strategic sectors of the Mount Pellegrino, one of the most relevant place in the city of Palermo. During the last two decades, several rockfalls affected the study area setting up a serious threat to the people, structures and infrastructures preventing the economic and social development. For these landslides a detailed GIS inventory was realized; the most dangerous rockfalls occurred within the two study sectors. In both areas we have carried out detailed field surveys and the geo-mechanical characterization of the rock slopes. These analyses allowed to define the rock mass parameters, the set of discontinuities and the kinematics. The back analyses for the past events were conducted permitting to define the blocks trajectories using a numerical model for rockfall simulation. Through this procedure the hazardous areas have been identified and the map of the landslide risk was produced considering the possible spread of the blocks both on land and at sea. The results were exploited to compare this map with the existent map in the framework of the Sicilian Master Plan for hydrogeological risk (PAI), showing that the new risk areas are larger than those previously mapped.