Debris flow numerical simulation using multiple kinds of rheological models: a case study in Cervinara (southern Italy)

Excessive rainfall in mountain catchments may trigger landslides or destabilize saturated streambeds. The resulting debris flow may propagate along the drainage network and reach urbanized areas, causing damage and loss of life. To ensure an efficient delimitation of such risk-prone areas, numerical models are often adopted to compute the time evolution of the flow. To this end, we apply a custom made monophasic Shallow Water based finite volume solver to the mass-flow like events occurred in Cervinara (Southern Italy) on 15-16 December 1999 which caused 6 fatalities and serious damage to buildings and structures. Several landslides were triggered that day and one in particular was able to propagate downstream, reaching the urbanized areas of Ioffredo and Cervinara. The event was comparatively simulated using two different rheological models, i.e. Voellmy and O’Brien, implemented inside the solver in order to assess which of them was able to better replicate the main characteristics of the flow. Validation was performed considering the extension of the inundated areas in the town and maximum flow velocity recorded on the field previously available. The adoption of an unstructured grid allowed both the representation of the urbanized areas by introducing the buildings as holes inside the mesh and the computation of the forces exerted on the buildings by the flow.