Simulating Snow Process Chains: Avalanche-River Interactions wirh r.avaflow

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200204857

ABSTRACT: r.avaflow is an open source tool for the simulation of gravitational mass flows and related complex process chains. Simulations can be performed using a classical single phase or a general two phase mixture flow model. The applicability of the tool has been evaluated with several back calculations of different natural hazard events. In this work we focus on snow avalanches. We first back calculated the 2009 Costa della Madonna snow avalanche event (north-east Italy) with the single phase model. With multiple simulations we optimized the material parameters that successfully minimized the difference between simulated and observed runout distances. Going beyond classical avalanche simulations, a complex process chain has been reconstructed, using the two phase model with entrainment applied in r.avaflow. The test case referred to the Damalanche that took place in January 2014 in Alaska, near the city of Valdez, and involved multiple avalanches, river flow and their interactions. The impacted river was completely dammed by a series of wet avalanches that entrained debris along their travel paths. A first simulation representing the steady state of the river was obtained whereas three successively released avalanches were discharged in the final simulation. We were able to reconstruct the cascade of effects including the
different processes and could reconstruct similar affected areas as observed. Challenges included density differences of the involved materials or the initial conditions. In total, the single and multiphase test cases were well represented by r.avaflow, underlining its applicability to real complex events.
KEYWORDS: process chains, Damalanche, snow river interaction, avalanche simulation, open source, r.avaflow.