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.