Hazard factors in high rocky coasts of Capri island (Gulf of Naples, Italy)

Capri island is located in the Tyrrhenian Sea, on the south side of the Gulf of Naples, Italy. Studies of the emerged and submerged coastal zone of the island through direct investigation, the study of aerial and satellite photographs, and bathymetric relief to a depth of-20/-30m has determined the morphological and morphoevolutive features and identified hazard factors that characterize the high rocky coasts of island. The island is almost completely bordered by high and steep rocky coasts (coastal cliffs) of structural control, often articulated in a succession of prominent headlands and embayments. The effects of a parallel retreat of the coastal cliffs are evident in the eastern coastal area resulting in a high degree of hazard in this stretch. The morphology of the coastal system consists in a cliff with sloping shore platform at the base of the cliff. The presence of the shore platform, which controls the erosional and shaping activities by wave motion of the cliff, plays an important role and represents the main hazard factor. The other main erosional processes on rocky coast represent subordinated hazard factors. Namely, structural and stratigraphic features (hard limestone, above clastic less resistant rocks, involved in rock falls caused by basal mechanical wave erosion; the rock strata dipping seaward; presence of NW-SE trending fault), high and very steep cliffs and limestone features. Instead, the western sector of the island of Capri has a limestone coast with a plunging cliff; the water depth at the base of the cliff is greater than the breaker depth. The waves are reflected from the cliff face and the mechanical wave erosion and subsequent mass movements do not occur; weathering and bio-erosion processes are the major erosive mechanisms. As a result the coastal hazard for the western sector is very low.