International Snow Science Workshop Proceedings - Montana State University Library

Item: Potential Dry Slab Avalanche Trigger Zones on Wind-Affected Slopes

• • Title: Potential Dry Slab Avalanche Trigger Zones on Wind-Affected Slopes

    Proceedings: Proceedings, 2012 International Snow Science Workshop, Anchorage, Alaska

    Authors:

    • Markus Eckerstorfer  [ Arctic Geology Department, University Centre in Svalbard, Norway ]  [ Department of Geosciences, University of Oslo, Norway ]
    • Wesley R. Farnsworth  [ Arctic Geology Department, University Centre in Svalbard, Norway ]  [ Department of Geosciences, University of Oslo, Norway ]
    • Karl W. Birkeland  [ USDA Forest Service National Avalanche Center ]

    Date: 2012

    Abstract: Experience suggests that shallow, steep zones on slopes are likely spots for artificially triggering slab avalanches. However, a scientific understanding of this observation is not well quantified. We performed 108 point stability tests on a 30 x 30 m slope in central Svalbard. The slope has a rugged underlying topography and frequent wind influence both by top and cross loading. We found three persistent weak layers at different depths in the snowpack. Due to the rough nature of the study slope, snow surface does not resemble the ground topography. Weak layers forming early in the season follow the ground topography closely. As snow depth increases, the influence of ground topography diminishes. We further found a decrease in slab thickness with increasing slope and bed surface inclination. We therefore investigated the influence of slab thickness on slope stability. Our data shows that stability decreased significantly with decreasing slab thickness, which correlates to how deeply the weak layer is buried. Thus the weakest spots on the slope coincide with the shallowest and steepest spots, where the deeper buried weak layers are buried “less deep”. Such spots often occur around topographic heights such as large rocks, which are thus potential trigger zones.

    Object ID: issw-2012-462-466.pdf

    Language of Article: English

    Presenter(s): unknown

    Keywords: slope, release zones, weak layer

    Page Number(s): 462-466

    Subjects: dry slab avalanches triggering ct scans

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