G.I.S. ANALYSIS FOR LANDSLIDE SUSCEPTIBILITY ASSESSMENT: AN EXAMPLE IN THE CILENTO AREA (SOUTHERN ITALY)

The aim of present work is the assessment and mapping of landslide susceptibility in a test area located in Cilento National Park (more precisely in Caselle in Pittari, situated in Campania, a region in Southern Italy).

From the geologic point of view, this area of study is characterized by the outcrop of two stratigraphic-structural units, both deformed during Alpine orogenesis: the Alburno-Cervati unit (cretaceous), resulted from deformation of the central portion of the Campano-Lucanian carbonate platform, and the North-Calabrian unit (cenozoic) resulted from the deformation of sin-orogenic basin. The first unit is constituted by limestone formations and the second one by clayey, sandy, carbonate flysch.

We studied the distribution and the characterization of landslides in the study area through photointerpretation and geomorphologic survey. This research shows that in the above mentioned area there are two types of landslides: slow earth flow and rock falls. Slow earth flow are numerous in the flysch formations and their landslide masses are quite large. Rock falls occur in limestone formations. They are less frequent and do not reach vast proportions.

GIS-based techniques are the best approach to the study of landslide susceptibility because they allow the management of several themes concerning instability factors. Besides, morphometric characteristics, playing an important role in landsliding processes, can be determined through the analysis of the digital terrain model. Here follows a list of the main phases of our analysis focusing on the mapping of earth flow susceptibility: - selection of the most useful instability factors (i.e.: lithology, slope, land use, hydrography, etc.); - multivariate statistic analysis of the selected factors in landslide areas; - creation of a model of susceptibility; - mapping of landslide susceptibility; - testing phase.

This method is based on the concept that instability factors in susceptible areas are similar to those observed in areas in which landslides have already happened. The application of this method would be useful to locate potential unstable areas, and so to predict the occurrence of future landslides.