A preliminary method for assessing sea cliff instability hazard: study cases along apulian coastline

Abstract

The instability processes of sea cliffs are the result of the influence of different hazard factors that depends mainly on the coastal morphology. For this reason, the hazard associated to instability processes affecting cliffs can be carried out by means of different methodological approaches. In particular, the presence of a beach at the cliff toe, which dampens the impulsive impact of sea waves and reduces the marine processes of erosion on the cliff, allows to analyze it as a generic rocky slope with same morphology and identical geo-structural characters. Among different stability methods, heuristic approaches can provide a preliminary evaluation of the stability conditions of cliffs and a zonation of the cliff portions most susceptible to instability phenomena. In presence of fractured, anisotropic and discontinuous rocky cliffs, the stability analyses through a deterministic approach are difficult to be performed. This paper presents a procedure to assess the stability conditions of three rocky cliffs located along the Apulia coast based on a heuristic slope instability system, the Slope Mass Rating (SMR) of Romana (1985). This model was used to individuate the most unstable areas on the cliff walls, mostly prone to rockfall hazard. This procedure is particularly useful, as can address more detailed study on the cliff portions most susceptible to block detachment.