Item: Snow avalanche size classification
Title: Snow avalanche size classification
Proceedings: Proceedings of the 1980 International Snow Science Workshop, Vancouver, BC, Canada
Authors: David M. McClung and Peter A. Schaerer, National Research Council of Canada, Vancouver, B.C.
Abstract: When avalanche events are reported, it is necessary to include an estimate or measure of their size. If a simple, consistent method of sizing avalanches can be found, obvious benefits can be derived. For example, data from different storm cycles, years, or areas can be compared. People such as avalanche forecasters, observers or consultants, as well as skiers, can clearly profit from the data once a good method is established. Unfortunately, in the great majority of cases there is no visual record of the avalanche as it falls. The observer is left with only a few measurable factors after the event. Some of these are: mass, runout distance, path dimension, depth, and spatial extent and water content of debris. In addition, there are other variables which may be estimated such as area swept out by the flowing ·avalanche, degree of path confinement, and damage to structures or vegetation. In this paper it is argued that a meaningful estimate of size should take into account all observables. Other measures of size proposed such as volume of snow moved, avalanche mass, and estimated kinetic or potential energy seem inadequate to describe avalanche size when taken singly. This is due to the inherent complexity of the phenomenon of avalanches in motion. In the present paper size classification systems with emphasis on the system in use in Canada are discussed. Experience with the Canadian system is described by data collected at Rogers Pass, B.C.
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Keywords: storm cycles, runout, avalanche classification
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