Landslide types and their relationships with weathering in a Calabrian basin,southern Italy

The basin of the Alaco River, in the Serre Massif of Calabria (Italy), is characterized by outcropping Palaeozoic granitoid rocks. The complex neotectonic history of the area and adverse climatic conditions, both active at least since the Quaternary, resulted in deep weathering of the crystalline rocks. Field observations, integrated with laboratory and in situ tests, allowed the weathering profile to be defined following the six-fold scheme proposed by the Hong Kong Geotechnical Control Office. The weathered rocks evidence a wide variety of mass movements, which were mapped over the entire basin. Debris flow-type instabilities dominate in the residual and saprolitic soils, while falls and slides are more significant in the less weathered rocks. In view of the complex vertical and lateral weathering in the rock mass and the high to very high overall susceptibility of the outcropping rocks to landsliding, it is difficult to postulate any direct relationships between individual types of mass movement and weathering grade.