THE IMPRESSIVE COASTAL CLIFFS OF CAPO CACCIA IN NORTH-WESTERN SARDINIA (ITALY). OUTLINES FOR LANDSLIDE RISK ASSESSMENT

Abstract: The coast between Capo Caccia and Punta Giglio promontories in the north-west of Sardinia is characterized by high cliffs extended for more than 37 km. Here the cliffs are interrupted only by the beach of Porto Conte and small rocky coves. They are made almost entirely of Mesozoic limestone rocks, which generally give rise to high coasts with different contexts of development and risk. Only a short section in the northernmost portion is given by marly-clayey rocks of Triassic. They form a highly unstable cliff, due to the presence of interbedded gypsum. This coast is formed by the recent flooding of the bay of Porto Conte, because in the past it was a large karst valley. In fact, the landscape of this area is dominated by karst landforms and a dense underground hydrographic network. The most famous karst caves are located in the continental part but, recently, the submerged caves have become an attractive location for divers. Finally, it is clear that the whole cliff of Capo Caccia and Punta Giglio has undergone a rapid evolution, driven by intense fracturing of the limestone as well as the deep and dense karstic process. This rapid evolution is demonstrated by the numerous landslides occurred along the coast and the absence/scarcity of sea level notches. In order to identify areas at risk of landslides along this coast so impressive, moreover corresponding to a Marine Protected Area and in part to a Regional Park, was made a GIS-based map of geomorphological risk related to the instability of the cliff. Such map shows four classes of hazard determined by the detection of fractures recognized only along the face of the cliffs and landslide processes occurring along it.