SLOPE INSTABILITY IN HISTORIC HILLTOP TOWNS OF BASILICATA, SOUTHERN ITALY

The importance of preserving Italian hilltop towns through a general g eotechnical strategy is discussed and is followed by a specific review of the hydrogeological conditions responsible for regional mass movem ents at ancient hilltop towns in Basilicata. A historical survey of re activations in colluvial deposits al selected sites in the region sugg ested that increased activity was taking place in response to extreme rainfall events, possibly related to long-term climatic changes. The i mportance of natural and anthropogenic processes along critical hydrog eological boundary conditions in relation to this activity is then rev iewed and one example of urban landsliding from Grassano in the Basent o valley is described. Local structure, such as faulting, was shown to be especially important in the location of both groundwater discharge (springs) and the landsliding. The landslide activity in the town was also shown to be related to a period of population expansion and poss ible domestic water leakages following the provision of a pumped suppl y. It is suggested that these anthropogenic processes reduce the usefu lness of empirical links between landslide frequency, rainfall extreme s or other explanations involving climatic change. Finally. a strategy for landslide management based on the use of hydrogeological conceptu al models and GIS technology is proposed.