Johan Gaume - EPFL - New insights into the initiation and dynamics of snow avalanches and cascading mass movements

Exceptional instabilities in alpine regions can trigger complex process chains involving rock, ice and snow avalanches, debris flows, lake outbursts and tsunamis. Global warming influences such gravitational mass movements leading to an increase in the frequency and magnitude of catastrophic events. Modeling these complex phenomena requires appropriate computational approaches. Over the past years, the Material Point Method (MPM) coupled with finite strain elastoplasticity has shown promise in modeling the initiation and dynamics of gravitational mass movements including the interaction between different materials and solid-fluid transitions. Here, we show how MPM simulations allowed us to advance our understanding of avalanche release, flow regime transitions as well as erosion/deposition mechanisms and associated wave phenomena. In addition, we present an extension of the model including multi-phase solid-fluid interactions and different constitutive models (rock, snow, ice and water). These new developments allowed us to simulate glacier calving and ensuing tsunamis as well as the propagation of cascading alpine mass movements. While our simulations require a significant computational effort, they can be used as numerical full-scale experiments to calibrate and parameterize more efficient depth-averaged models for engineering purposes. Our models can thus contribute to anticipate the consequences of future alpine mass movements and cascading events, which is tremendously important to evaluate the resilience of existing protection systems, update hazard mapping procedures, and define adaptation strategies in a climate change context.