The impressive coastal cliffs of Capo Caccia in north-western Sardinia (Italy). Outlines for landslide risk assessment

The coast between Capo Caccia and Punta Giglio promontories in thenorth-west of Sardinia is characterized by high cliffs extended for more than 37km. Here the cliffs are interrupted only by the beach of Porto Conte and smallrocky coves. They are made almost entirely of Mesozoic limestone rocks, whichgenerally 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 ofTriassic. They form a highly unstable cliff, due to the presence of interbeddedgypsum. 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 isdominated by karst landforms and a dense underground hydrographic network.The most famous karst caves are located in the continental part but, recently, thesubmerged caves have become an attractive location for divers. Finally, it is clearthat the whole cliff of Capo Caccia and Punta Giglio has undergone a rapidevolution, driven by intense fracturing of the limestone as well as the deep anddense karstic process. This rapid evolution is demonstrated by the numerouslandslides 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 RegionalPark, was made a GIS-based map of geomorphological risk related to theinstability of the cliff. Such map shows four classes of hazard determined by thedetection of fractures recognized only along the face of the cliffs and landslideprocesses occurring along it.