Item: Storm Snow Avalanches: Characteristics and Forecasting
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Title: Storm Snow Avalanches: Characteristics and Forecasting
Proceedings: Proceedings, 2012 International Snow Science Workshop, Anchorage, Alaska
Authors:
- Edward H. Bair [ US Army Corps of Engineers Cold Regions Research and Engineering Laboratory, Hanover, NH, USA ] [ Earth Research Institute, University of California, Santa Barbara, CA, USA ]
- Ron Simenhois [ Southeast Alaska Avalanche Center, Juneau, AK, USA ]
- Alec van Herwijnen [ WSL Institute for Snow and Av alanche Research SLF, Davos, Switzerland ]
- Karl Birkeland [ US Forest Service National Avalanche Center, Bozeman, MT, USA ]
- Jeff Dozier [ Bren School of Environmental Science and Management, University of California, Santa Barbara, CA, USA ]
Date: 2012
Abstract: At ski areas, a majority of avalanches fail in storm snow. We investigate these avalanches using stability tests and avalanche observations from California and Alaska. Collapse amplitudes during fracture, measured using particle tracking, were 1 mm for a failure layer of precipitation particles and 7 mm for a layer of unrimed sectored plates. Stability test results showed little dependence on slope angle, suggesting that both precipitation particles and older faceted crystals (persistent weak layers) fail as described by the anticrack model, with collapse providing energy. Using observations from avalanche control work at Mammoth Mountain, CA USA, a large coastal ski area where 9/10 avalanches fail in storm snow, we examined Extended Column Test (ECT) results and their relation to avalanche activity. ECT propagation was a powerful predictor; days with ECTs that propagated had significantly more and larger avalanches. Since other studies have shown that the ECT is an effective predictor of avalanches involving persistent weak layers, we suggest that the ECT is an effective test to predict both types of avalanches, those that fail in storm snow and those that fail on persistent weak layers.
Object ID: issw-2012-111-114.pdf
Language of Article: English
Presenter(s): unknown
Keywords: storm snow, ski area, extended column test
Page Number(s): 111-114
Subjects: Extended Column Test (ECT) persistent weak layers usa ski areas
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