A Three stage Method for Debris Flow Analysis

Rainfall-induced debris flows are characterised by high velocity, can be triggered by a slide and occur on established paths, usually first- or second-order drainage channels. During flow path, these phenomena entrain a strong quantity of material and water. Debris flow risk assessment and risk mitigation measure design involve forecasting spatial (susceptibility) and temporal (hazard) landslide distribution. The landslide susceptibility analysis provides the most susceptible areas to landslides and suggests where disaster protection measures are necessary to reduce the exposure of elements at risk and increase the community resilience. In this context, the paper proposes a methodology for debris flow susceptibility and hazard analysis. The methodology examines both debris flow triggering and propagation stages through two physically based models. The “Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability” (TRIGRS) model provided information about the location and initial volume of potential landslides. The “Smoothed Particle Hydrodynamics” (SPH) model, using the triggering volumes as input data, allowed for back analysis of the propagation in terms of both main pathway and depositional area. The models can be easily implemented over large areas for fast landslide risk analysis and are able to provide interesting information for the design of disaster mitigation structures.