The Monte Gallo area is a carbonate relief that develops a significant nature reserve and highly attracts tourism to the urbanized area of the City of Palermo (Southern Italy). The slopes are affected by several rockfall events, which have also caused death, injuries, material damage, and a strong social and economic impact. Here, a detailed geological and geotechnical study to assess the rockfall hazard relating to two sectors of the mount has been carried out. The hazard assessment at the slope scale was performed based on geological, geomorphological, geomechanical, and seismic analysis. Using both analytical and empirical methods and by means of different software, the reconstruction of the propagation areas for the eastern sector of the Mount was possible. Results were used to better understand the overall structure, characterize the rockfall source areas’ kinematics, and recognize the basic failure mechanisms. The obtained runout areas were compared with each other and with those of previous studies conducted in a neighboring area, as well as with the corresponding hazard area maps of the official cartography, which is being updated. It is expected to be supplemented with maps derived from empirical models.
The coastal sector of central-northern Sicily ranging from Capo Zafferano to Capo San Vito is characterized by isolated carbonate reliefs that are fundamental for the territory from an economic, social, tourist, and naturalistic perspective. The peculiar lithological and structural setting, the climate conditions, and the seismicity of the area define the conditions for the triggering of rockfall phenomena which have caused considerable material damage and, in certain cases, the loss of human life as well. These structures result from the ancient and the recent tectonic evolution that led to the present-day arrangement of the chain sector of the Sicilian collisional complex. The sizes and type of rockfall differ depending on the structural setting and the morphological processes on the slopes; the extension of propagation areas of the rockfall is conditioned by various factors such as the block size, the outcropping lithology, and slope morphology. In these areas, there are elements that are potentially at risk. Therefore it becomes essential to define the potential hazard areas to assess the risk on the territory and planning mitigation interventions. For the study area (Monte Gallo, Northern Sicily), the map containing potential block propagation areas is available (hazard zones of the national guidelines of the Italian Basin Master Plan for geo-hydrological risk mitigation - PAI). These maps overview the landslides and could be implemented through additional studies useful for planning and monitoring geomorphological risk. To provide a scenario for the danger in consideration, the analysis of the eastern sector of the Mount has been carried out; the result of such analyses is the area of propagation of the landslides and the potential trajectories of the boulders. Geological and geotechnical analyses have been conducted, and the acquired data were processed using the ‘reach angle’ empirical model [1,2] and the ‘lumped mass’ analytical model [3,4]; in this way, it was possible to obtain the runout zones and trajectories respectively; in addition, such applications have been conducted employing different software both open source and paid. The achieved results were compared with each other and to the hazard maps of the PAI [5] and those of previous studies in a sector close to the study area [6,7].