A Method to Evaluate Debris Flow Triggering and Propagation by Numerical Analyses

Abstract

Debris flows travel at very rapid to extremely rapid velocity, often involve significant entrainment of soil and occur periodically along gullies and first or second order drainage channels. Owing to their characteristics, these phenomena can cause losses of human lives and significant socio-economic disasters. In weathered gneiss, the analysis of these phenomena is very complex due to the heterogeneity of soils and the difficulty of undisturbed sample taking. On these soils, a preliminary characterization of triggering and propagation phases could be carried out through a debris flow numerical analysis. The paper proposes a methodology for the analysis of a debris flow based on the combined use of two physically based models (TRIGRS and SPH). TRIGRS was used for the analysis of the triggering phase and allowed estimating the mobilized triggering volumes; SPH, using the triggering volumes, allowed the analysis of the propagation phase. The methodology has been applied to a debris flow occurred in Calabria (southern Italy). The obtained results show a good agreement with the real case in terms of both triggering phase, propagation zones as well as of depositional area, and represent the starting point on which to identify debris flow risk mitigation measures.