![]() The Sorrento Peninsula is a structural ridge characterized by high relief and very steep slopes, made up of fractured and karsified dolomite limestone of Mesozoic age, locally covered by Quaternary pyroclastic deposits (Fig. The methodologies used to define the hazard level generally take into consideration the joint attitude General setting and case study ![]() Such landslides are more and more frequently subject to studies aimed at prevention, requiring drawing up “risk” and “hazard” maps (IDNDR, 1992 Canuti and Casagli, 1994 Cruden and Varnes, 1996 Einstein, 1997). Rock falls are complex natural phenomena in which two main moments can be distinguished: block detachment from the rock mass, and falling and rolling downhill with subsequent arrest. Section snippets Previous studies for triggering susceptibility assessment In fact, being a photogrammetric map, it allows location and quantification of the intervention areas (surface and volumes) with great precision, thus giving the possibility of estimating expenses in detail. This map can be useful for a subsequent study aimed at planning various interventions of hazard mitigation. After this, different geo-thematic maps showing the main geological, geomorphological and geostructural information were constructed and then compared, allowing the development of the triggering susceptibility map. It is the result of much experience on various rocky cliffs of the Sorrento Peninsula, where many built-up areas and roads have been frequently affected by these phenomena.Īs cartographic representation is a main problem in the study of a vertical cliff, a frontal topographic survey (terrestrial photogrammetry) was first carried out. ![]() In the present study, a simple and easy-to-use methodology (partly belonging to the second type) to assess rock falls and create susceptibility maps is proposed. Physically based approaches that evaluate stability using physical laws (Terlien et al., 1995). Heuristic or multi-criterion methods based on expert experience (Leroi, 1996) associating weights to various instability factors (Wagner et al., 1990 Gupta et al., 1999 Meisina et al., 2001). Methods using statistical techniques (Carrara, 1983 Carrara et al., 1995 Chung et al., 1995), involving comparison of an inventory of observed landslides with the distribution of physical factors causing landslides, either directly or indirectly. In general, three types of approaches can be distinguished (Guzzetti et al., 1999 Crosta et al., 2001 Baillifard et al., 2003): 1. There are numerous methodologies, both on a national and international scale, to assess triggering and invasion susceptibility. Moreover, their sudden triggering and high speed make it difficult to warn people in proper time, thus producing risky situations. Even when of small dimensions, they can cause serious damage to buildings and roads, sometimes interrupting communication between built-up areas. Rock falls are among the phenomena more frequently causing problems for communities in mountainous geological settings. 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.). 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. A frontal topographic survey (terrestrial photogrammetry) was first carried out. This methodology is mainly suitable for the study of single cliffs or slope with limited dimensions.Ĭartographic representation is a main problem in the study of a vertical cliff. The acquisition of the data involves a detailed large-scale study (scale 1:500). 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. For this reason rock falls, rock slides and, more seldom, topples are very frequent in the area. Generally, the cliffs are strongly jointed and affected by karst processes. 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. ![]() A semi-quantitative methodology for rock fall susceptibility assessment is presented.
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