Lateral spreading phenomena and weathering processes from the Tropea area (Calabria, southern Italy)

This paper describes the lateral spreading landslides, the weathering processes and the hydrogeological risk patterns of the NW sector of Monte Poro (Calabria, southern Italy), based on the development of a multidisciplinary research. The tectonic uplift of the area combined with the litho-structural features of the sedimentary deposits overlying the intensely weathered granitoid complex produces important gravitational phenomena characterized by lateral spreading kinematics. The contact between deposits with a different behaviour, together with the high slope energy related to the tectonic uplift processes, is the main cause of widespread fracturing and disjoint of the lithologies associated with lateral spreading phenomena. These phenomena are also testified by the various trenches and cracks characterized by a parallel orientation relatively to the main fluvial incisions. Measures of these deformations were obtained with a quantitative result by the use of Interferometric Stacking methods. The experimental results confirm this morphological scenario characterized by strain values ranging between 20 and 25 mm/year relatively to the landslides detected. Geomorphological analysis of the drainage basins in the study area indicates a juvenile stage of the stream networks. This pattern is consistent with the high rate of tectonic uplift of the area, hence the continuous rejuvenation of the stream networks and their low level of hierarchy. These conditions of geomorphic equilibrium of the stream networks, the widespread occurrence of geological instability in continuous evolution, are the main causes of high hydrogeological risk conditions for this coastal area.