High-resolution mapping of rock fall instability through the integration of photogrammetric, geomorphological and engineering�geological surveys.

A semi-quantitative methodology for rock fall susceptibility assessment is presented. The test area is located along the Amalfi coast (Sorrento Peninsula, Southern Italy) which is characterized by high relief energy and very steep slopes, made up of dolomite limestone of Mesozoic age. Generally, the cliffs are strongly jointed and affected by karst processes. For this reason rock falls, rock slides and, more seldom, topples are very frequent in the area. The Study took a multidisciplinary approach mixing classical field geology observations with typically geo-mechanical ones and required the support of highly professional staff, such as applied geologists, experts in photogrammetric survey techniques and engineers for stabilization works planning. The acquisition of the data involves a detailed large-scale study (scale 1:500). This methodology is mainly suitable for the study of single cliffs or slope with limited dimensions. Cartographic representation is a main problem in the study of a vertical cliff. A frontal topographic survey (terrestrial photogrammetry) was first carried out. After this, different geo-thematic maps showing the main geological, geomorphological and geostructural information were elaborated and then compared, allowing the elaboration of the triggering susceptibility map. The semi-quantitative proposed method has a good accuracy in the realization of the potential detachment area of rock falls, in order to predispose stabilization works and to rationalize the disposal resources for the hazard mitigation in the unstable areas near human utilization (urban centres, roads, etc.).