International Snow Science Workshop Proceedings - Montana State University Library

Item: WHUMPING OF A PERSISTENT DEPTH HOAR WEAK LAYER: ANALYSIS OF A RARE COMBINATION OF MANUAL STABILITY TESTS AND AUTOMATED SNOW MEASUREMENTS

• • Title: WHUMPING OF A PERSISTENT DEPTH HOAR WEAK LAYER: ANALYSIS OF A RARE COMBINATION OF MANUAL STABILITY TESTS AND AUTOMATED SNOW MEASUREMENTS

    Proceedings: Proceedings, International Snow Science Workshop, Whistler, BC, Canada, 2026

    Authors:

    • Benjamin Walter  [ WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland ]
    • Christoph Marty  [ WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland ]
    • Fabian Wolfsperger  [ WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland ]
    • Alec van Herwijnen  [ WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland ]
    • Francesco Pellegrini  [ University of Wyoming, Laramie, Wyoming, USA ]
    • Alexandra von der Esch  [ Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zurich, Zurich, Switzerland ]  [ Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), bâtiment ALPOLE, Sion, Switzerland ]
    • Yiyao Chen  [ Department of Earth Science, University of Bergen, Bergen, Norway ]
    • Kalin Markov  [ National Institute of Geophysics, Geodesy and Geography, Bulgarian Academy of Science, Sofia, Bulgaria ]

    Date: 2026-09-28

    Abstract: Whumpf sounds indicate the collapse of a buried weak layer and are associated with fracture propagation over distances of tens of meters without avalanche formation. We investigated a whumpf event triggered on 26 February 2026 at the well instrumented Weissfluhsch test site, Switzerland, during repeated dynamic loading of a non-isolated snow column. Field observations were combined with snow stratigraphy, automated snow-height and pressure-based snow water equivalent measurements. The event produced a surface settlement of approximately 7 mm and a rapid increase in the pressure recorded by snow scales, followed by relaxation toward pre-event pressures over 2–3 hours. We interpret these observations as evidence of rapid stress redistribution within the snowpack during fracture propagation due to strain softening, followed by a slower recovery toward pre-whumpf conditions through slab hardening associated with sintering and progressive bond strengthening.

    Object ID: ISSW2026_P4.6.pdf

    DOI: https://doi.org/10.15788/1790099412

    Language of Article: English

    Presenter(s): Benjamin Walter

    Keywords: Depth Hoar, Persistent Weak Layer, Whumpf, Fracture Propagation, Snow Stability

    Page Number(s): 362 - 365

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