Modelling of debris flows and flash floods propagation: a case study from Italian Alps

Storage basins, check dams, barriers and other control works are often used to reduce threats and damage from flow-like mass movements. This paper deals with the effectiveness of two storage basins of the Italian Alps against debris flows followed by a flash flood induced by short heavy rainfall in 2009. Referring to detailed field data, the propagation of flows and their interaction with the control works are analysed by using an advanced numerical depth-averaged flow propagation model based on SPH (Smooth Particle Hydrodynamics) technique. The Froude dynamic similitude is here used to provide a quantitative descriptor of the dynamic features of the flows. The numerical results show that debris flows accumulated in the storage basins since they propagated downslope like subcritical flows. On the contrary, flash floods overpassed the control works having moved along the entire path as supercritical flows. Those findings are fully supported by some previous studies and provide a further contribution to the relevant topic of granular flow-obstacle interaction.