Karst collapse susceptibility assessment: A case study on the Amalfi Coast (Southern Italy)

This paper presents a study to evaluate the collapse susceptibility of a karst cave located along a slope on the Amalfi coast (southern Italy) and the presumable geomorphological evolution of the whole slope as a result of cave roof collapse. In the study area, several natural karst caves with volumes varying between 1000 and > 10,000 m3 were inventoried and the most likely genetic processes were identified. Some of them proved to be remnants of already collapsed caves, while others were in precarious stability conditions. The caves are usually located upslope or very close to the main populated resorts. A detailed geological, geomorphological and geostructural study was performed on a very wide, deep cave (called the “Saraceno” cave), on which the resort town of Conca de' Marini has been built. The study was carried out through a multidisciplinary approach, which included classical field geological observations, sometimes requiring the support of rock-climbing geologists, experts in photogrammetric surveys and terrestrial laser scanning techniques (TLS). TLS surveys allowed the reconstruction of an accurate geometric and geostructural model of the cave and its relationship with the upslope Conca de' Marini resort. Furthermore, it allowed the thickness of the cave overburden to be determined in detail; ground surfaces most susceptible to collapse were also identified. In the event of possible widespread collapse, several buildings and transportation infrastructures could be involved. As the cave is located on a very steep slope, a debris avalanche could be triggered in the event of a catastrophic failure, and the landslide debris, characterized by a presumably high magnitude and velocity, could involve a wide slope area down to the coast. The failure evolution could be very similar to that which took place in Amalfi in the late 19th century.