Influence of snow cover properties on avalanche dynamics

Abstract

The destructive power of an avalanche depends, among other things, on the overall mass and the snow conditions in the avalanche path. So far, the knowledge on the effect of snow conditions on avalanche behavior is limited and largely qualitative. We investigate the effects of snow cover properties on avalanche dynamics, such as run-out distance and front velocity. Therefore, five avalanches with similar initial mass and topography but different flow dynamics were selected from the Vallée de la Sionne test site (Western Swiss Alps) database. For each of these avalanches, the snow conditions were reconstructed using the three-dimensional surface process model Alpine3D and the snow cover model SNOWPACK. For the investigated avalanches the data shows that the total mass, mainly controlled by entrained mass, defines run-out distance but does not correlate with front velocity. A direct effect of snow temperature on front velocity, development of the powder cloud and deposition structures could be observed. A snow temperature warmer than approximately −2°C was identified as critical value for changes in flow dynamics. No direct correlations of flow dynamical parameters with snow density and type of entrained snow were observed.