Modeling the influence of snowcover temperature and water content on wet snow avalanche runout
Cesar Vera Valero1, Nander Wever2, Marc Christen1, and Perry Bartelt11WSL Institute for Snow and Avalanche Research SLF, Flüelastrasse 11, 7260 Davos Dorf, Switzerland 2École Polytechnique Fédérale de Lausanne (EPFL), School of Architecture, Civil and Environmental Engineering, Lausanne, Switzerland
Received: 25 Jan 2017 – Accepted for review: 10 Feb 2017 – Discussion started: 07 Mar 2017
Abstract. Snow avalanche motion is strongly dependent on the temperature and water content of the snowcover. In this paper we use a snowcover model, driven by measured meteorological data, to set the initial and boundary conditions for wet snow avalanche calculations. The snowcover model provides estimates of snow depth, density, temperature and liquid water content. This information is used to prescribe fracture heights and erosion depths for an avalanche dynamics model. We compare simulated runout distances with observed avalanche deposition fields using a contingency table analysis. Our analysis of the simulations reveals a large variability in predicted runout for tracks with flat terraces and gradual slope transitions to the runout zone. Reliable estimates of avalanche mass (height and density) in the release and erosion zones is identified to be more important than an exact specification of temperature and water content. For wet snow avalanches, this implies that the layers where meltwater accumulates in the release zone must be identified accurately as this defines the height of the fracture slab and therefore the release mass. This is an interesting result because it indicates the critical role of fracture depth as an input parameter in avalanche simulations. Advanced thermomechanical models appear to be better suited than existing guideline procedure to simulate wet snow avalanches when accurate snowcover information is available.
Vera Valero, C., Wever, N., Christen, M., and Bartelt, P.: Modeling the influence of snowcover temperature and water content on wet snow avalanche runout, Nat. Hazards Earth Syst. Sci. Discuss., doi:10.5194/nhess-2017-36, in review, 2017.