Hydrological monitoring and modeling of pyroclastic soil covers for assessing debris flows hazard in volcanic and peri-volcanic areas of Campania region (southern Italy)

Abstract

The shallow landsliding involving pyroclastic coverings mantling peri-Vesuvian and Phlegraean slopes (Campania region, southern Italy) represent a challenging theme which can be analyzed through different approaches. These landslides are characterized by a series of processes whose triggering mechanisms are affected by geological, geomorphological and hydrological factors. Due to the aim of this research project, the manuscript was organized considering results of the research activities carried out for two sample areas of the Campania region, which are affected by the same type of geohazard. Different geological settings and similar geomorphological features which characterize Phlegraean and peri-Vesuvian slopes were described, shifting attention mostly about the origin of the pyroclastic soils involved by slope instabilities. In particular, volcano-tectonic activity occurred in the Campanian Plain was described, analyzing the evolutionary phases of two main volcanic districts of the area: the Somma-Vesuvius volcano and Phlegraean Fields volcanic district. After this introduction, hydrological and slope stability processes were described to define the predisposing and triggering features of rainfall-induced flow-type landslides, as well as their rheology and kinematics. For these reasons, a detailed description of the hydrological slope processes, related to rainfall events, and hydro-mechanical properties of the involved materials were described. In addition, following the different landslide classifications, these slope instabilities were described. Finally, to underline the relevance of this geohazard, which strongly affect the urban settlements located at the foothill of peri-Vesuvian mountains and Phlegraean slopes, main documented historical and recent cases of landslide events were shown. The main section of this manuscript is represented by the description of the methods and results of the hydrological monitoring and numerical modeling activities. In detail, settings of field monitoring stations, located in the two sample areas, and the reconstruction of physically-based models, used for the hydrological modeling at slope and regional scale, were described. As a final result, rainfall thresholds, by using a deterministic approach, and landslide susceptibility maps were estimated. Finally, results were analyzed and then discussed by comparison with results from prior literature.