Item: Can stability tests help recreationists assess the local avalanche danger?
Title: Can stability tests help recreationists assess the local avalanche danger?
Proceedings: Proceedings of the 2006 International Snow Science Workshop, Telluride, Colorado
Authors: Bruce Jamieson, Jürg Schweizer, Pascal Haegeli, Cam Campbell, Department of Civil Engineering, University of Calgary, Calgary, Alberta, T2N 1N4, Canada, Department of Geology and Geophysics, University of Calgary, WSL Swiss Federal Institute
Abstract: In western Canada, various agencies issue public avalanche bulletins three to seven times per week for regions which range from less than 500 km2 to almost 30,000 km2. Sometimes avalanche danger varies substantially within the larger regions. In this study, we assessed whether the results of local rutschblock tests (including whole block releases) and compression tests (including sudden fractures) could help recreationists assess the local avalanche danger. Since “weekend” recreationists cannot reliably select areas of below average stability for their snowpack tests, especially in wind affected areas, we restricted the test sites to sheltered areas at and below treeline where our observers were likely to get the same results as recreationists. Field studies in the Coast, Columbia and Rocky Mountains yielded stability test results and local danger ratings. After a small number of data were filtered to minimize an observation bias, the results of compression tests and rutschblock tests were assessed using ratings of the local avalanche danger. Without considering the danger rating from the regional bulletin, the results of stability tests correlated weakly but significantly with the local avalanche danger. The score from the rutschblock test, with its greater area, correlated better than any of the compression test variables with the local avalanche danger. Various combinations of the regional danger rating and stability test results were assessed in terms of their performance in recognizing when the local avalanche danger was higher than the regional rating. Again the rutschblock results were more predictive than the compression test results. Some simple results of stability tests such as the observation of sudden fractures in compression tests and the release of the entire block in rutschblock tests showed promising results.
Keywords: snowpack stability tests, avalanche forecasting, avalanche danger, spatial scale
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