Approaches for mapping suscepibility to rockfalls initiation in carbonate rock-masses. A case study from the from the Sorrento coast (southern Italy)

Abstract

Most of the shoreline of the Campania region, Southern Italy, is characterized by steep and high rocky slopes, then several localities, densely populated and highly touristic attractive for the worldwide famous landscapes are exposed to an high rockfall risk. Particularly, the touristic localities on the Sorrentine Peninsula, such as Sorrento, Vico Equense and Amalfi, can be considered among the most representative case-studies prone to the recurrent instability of rockblocks. Due to the frequent location of settlements and roads underneath and at very limited or null distances from the carbonate steep slopes, a diffuse condition of high rockfall risk exists. Consequently, the assessment of priorities in directing active remedial works to be carried out on the unstable rock slopes is still a challenging issue.In order to find an effective method for assessing the susceptibility to rockfall initiation with approaches suitable for detailed mapping, a combined application of standard methods was tested.The Romana's Slope Mass Rating (SMR) and the Matheson's graphical tests, for assessing the number of fundamental instability mechanisms, were applied in a test site of the Sorrento coast. Results of the two methods were separately evaluated and then combined in a new rating approach by indexing the respective susceptibility classes. In addition, the number of joint sets and the macro-structural features of the rock-mass (faults and master joints) were considered. By means of statistical analyses of rockfalls occurred in the test area, the results obtained with the new combined approach were found more accurate in assessing and mapping the most susceptible areas.