An integrated approach for coastal cliff susceptibility: The case study of Procida Island (southern Italy)

Procida Island, located in the Gulf of Naples (southern Italy), is characterized by steep cliffed coasts, articulated in a succession of headlands and small embayments with narrow pocket beaches, such as Ciraccio and Chiaia, often characterized by instability. In this study, amethodology for coastal cliff susceptibility assessment has been conceived based on hydraulic and geo-morphological characteristics, which supported the construction of a Cliff Stability Index (CSI). The geomorphological characteristics are related to the whole cliff face, the cliffmaterial resistance, and the cliff failure mechanisms. The hydraulic actions on the cliff are related to thewave impactwhich is exerted by the breaking waves once the wave run-up distance exceeds the beachwidth. The index takes into account the slope of the cliff, the rock strength, thewave energy at the cliff base produced by the broken wave and the presence of defence structures at the cliff base. The resulting index classification, obtained by addition of the partial sub-indices, has been compared with the observed coastal cliff evolution from 1954 to 2021.

Automated summary

This study proposes a methodology for assessing coastal cliff susceptibility based on hydraulic and geomorphological characteristics, and constructs a Cliff Stability Index (CSI). The index takes into account various factors such as cliff slope, rock strength, wave energy, and defense structures, and its effectiveness is verified by comparing it with observed coastal cliff evolution.