The role of hydrological circulation in the initiation process of debris flows in the Campanian volcanic terrain

Volcaniclastic debris flows are highly concentrated flows of rock debris, mud and water in which the sediment is of volcanic origin. These phenomena can be syneruptive, posteruptive, or unrelated to an eruption. To be generated, the coexistence of steep slopes, unconsolidated sediments and an adequate amount of water is necessary.

The aim of this project is to investigate the role of water circulation in the initiation processes of debris flows to enhance our ability to anticipate potential new debris flows in the Campanian Volcanism area, focusing on the Sarno area. Sarno is a small municipality located in the Vesuvius Volcanism area (western side of the Campanian Apennines) that is sadly infamous for the major debris flow events that, on the 6th of May 1998, destroyed the town and killed around 150 people.

The study area exhibits a convergence of geomorphological and lithostratigraphic settings that contribute to enhancing its exposure to hazards: i) the presence of a calcareous bedrock with very steep slopes (30-45°) mantled by ii) an alternation of colluvium and pyroclastic deposits, and iii) natural scarps and man-made cuts that further worsen the stability conditions.

This research employs a multimethodological approach including i) geotechnical and rheological analyses of the sediments; ii) X-ray Diffraction for the mineralogical characterisation, particularly of the clay fraction; iii) large-scale experiments to investigate the role of water circulation in the sediments during simulated rainfall in the triggering of volcaniclastic debris flows; iv) in situ Time-Domain Reflectometry measurements at Pizzo D’Alvano for soil moisture vertical distribution and v) simultaneously acquisition-surveys by using a drone-mounted passive radiometer for spatial soil moisture distribution. Integrating these methods aims to achieve understanding of the water content distribution in the debris flow initiation process that could be potentially used in the rainfall-triggered landslide early-warning systems.