Safeguarding historic towns on hilltops threatened by land sliding: The case of San Fratello in Sicily

The paper presents the case history of San Fratello, a small town in the Nebrodi Mountains in Sicily rich in history and having very peculiar environmental and cultural characteristics. Both slopes of the narrow ridge where San Fratello lies were affected in 1754, 1922, 1986 and 2010 by very large landslides. The landslide of February 2010 is largely the reactivation of that of 1754. It destroyed many infrastructures and seriously damaged more than 200 buildings and caused the evacuation of 25% of the population. Emergency actions to block regression of uphill movements and secure the buildings and their inhabitants as quickly as possible, were carried out. The sliding slope down to the town was left to its natural evolution. The paper presents the results of the geomorphological and geotechnical analyses recently carried out to understand the whole landslide reactivation mechanisms. It is felt necessary to define an advanced geotechnical model of the landslide for quantitative evaluation of hazard and rational landslide risk management in the area.