Rockfalls in the cliff of Pitigliano (Central Italy): integrated techniques for landslide hazard assessment

Pitigliano (Southern Tuscany, Italy) is an interesting case-history for the analysis of interactions between geotechnical features, man-induced factors and geological hazards. The landscape of the town, in fact, is the consequence of a continuous geomorphological evolution and slope instability phenomena, such as rockfalls, toppling and associated debris slides, which destroyed buildings and reduced the extension of the urban area. Even if this situation is very frequent in Central Italy and some other towns are affected by the same problems, Pitigliano provides an additional element of interest, represented by the presence of an extensive network of chambers and passages excavated probably starting from Medieval times. The survey of these tunnels constituted the first step of an extensive engineering geology survey of the cliff, carried out in order to obtain a complete set of information about the rock mass. This paper summarizes the methods and techniques used in this study and the results: the survey of tunnels and chambers (that led to the identification of about one hundred different underground paths) has been realized with speleological techniques; a laser scanning survey allowed the reconstruction of the digital elevation model of the cliff and the integration of structural data in impervious areas; characterization and classifications of the rock mass have been performed through traditional methods; for the localization of the most critical sectors of the cliff kinematical analyses have been carried out; finally, an innovative wireless monitoring system of some critical cracks has been implemented. The results of these different analyses represent an interesting case history and a complete data set for the realization of consolidation works that are being carried out.