Item: A simple model of snow slope stability during storms
Title: A simple model of snow slope stability during storms
Proceedings: Proceedings of the 2004 International Snow Science Workshop, Jackson Hole, Wyoming
Authors: P. Hayes, C. Wilbour, R. Gibson, H.P. Marshall and H. Conway, Earth and Space Sciences, University of Washington, Washington State Department of Transportation, Institute of Arctic and Alpine Research, University of Colorado
Abstract: Snow slope stability is controlled by the geometry of the start zone and the mechanical properties of the snow pack. Here we report progress toward developing a simplified model of the evolution of snow slope stability during storms. The model (SNOSS) keeps track of the evolving gravitational stress imposed by the new snow and the strength of sub-surface layers. Avalanching is predicted when the down-slope component of the gravitational shear stress from the overburden exceeds the resisting basal strength of a buried weak layer; there is a competition between the rate of loading from new snow and the rate of strengthening of buried layers. In theory, SNOSS should provide a conservative estimate (predicting failure earlier than expected) because it does not account for influences such as longitudinal stress gradients in the slab, or non-linear or time-dependent properties of snow. Much of the appeal of SNOSS is that it is physically based (with empirical parameterizations) and its input requirements are easily measured and often readily available. The model runs on a PC and can be used operationally to track the evolving stability. The model is tested using hourly measurements of precipitation and temperature from a network of weather stations and observations of avalanche occurrence near Snoqualmie Pass in the Washington Cascades during the winter of 2003-04.
Keywords: snow slope stability, avalanches, modeling
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