Calculating dense-snow avalanche runout using a Voellmy-fluid model with active/passive longitudinal straining

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Abstract
A quasi-one-dimensional dense-snow avalanche model has been developed to predict avalanche runout and flow velocity in a general two-dimensional terrain. The model contains three different dense-snow-avalanche flow laws. These are: (1) a Voellmy-fluid flow law with longitudinal active/passive straining, (2) a Voellmy-fluid flow-law advanced by Russian researchers in which the Coulomb-like dry friction is limited by a yield stress, and (3) a modified Criminale—Ericksen—Filby fluid model proposed by Norwegian researchers. The application of the Voellmy-fluid law with active/passive straining to solve practical avalanche-dynamics problems is evaluated by applying the model to simulate laboratory experiments and field case-studies. The model is additionally evaluated by comparing simulation results using the Russian and Norwegian models. In a final analysis the influence of the initial conditions on avalanche runout is investigated. We conclude that the model resolves many of the shortcomings of the Voellmy–Salm model, which is traditionally used in Switzerland to predict avalanche runout. Furthermore, since the model contains the three well-calibrated parameters of the Swiss Guidelines on avalanche calculation it can be readily applied in practice. We discuss why we believe the Russian and Norwegian models are not ready for practical application. Finally, we show that many problems remain, such as the specification of the initial release conditions. We conclude that numerical models require a more detailed description of initial fracture conditions.