International Snow Science Workshop Proceedings - Montana State University Library

Item: REMOTELY SENSED AVALANCHE ACTIVITY DURING THREE EXTREME AVALANCHE PERIODS IN SWITZERLAND

• • Title: REMOTELY SENSED AVALANCHE ACTIVITY DURING THREE EXTREME AVALANCHE PERIODS IN SWITZERLAND

    Proceedings: International Snow Science Workshop 2024, Tromsø, Norway

    Authors:

    • Elisabeth D. Hafner  [ WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland ]  [ Climate Change, Extremes, and Natural Hazards in Alpine Regions Research Center CERC, Davos, Switzerland ]  [ EcoVision Lab, Photogrammetry and Remote Sensing, ETH Zurich, Zurich, Switzerland ]
    • Frank Techel  [ WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland ]
    • Holger Heisig  [ Federal Office of Topography swisstopo, Wabern, Switzerland ]
    • Jor Fergus Dal  [ WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland ]  [ Climate Change, Extremes, and Natural Hazards in Alpine Regions Research Center CERC, Davos, Switzerland ]
    • Yves Bühler  [ WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland ]  [ Climate Change, Extremes, and Natural Hazards in Alpine Regions Research Center CERC, Davos, Switzerland ]

    Date: 2024-09-23

    Abstract: Systematic mapping of avalanches using remote-sensing technologies has become a reliable and – when combined with machine-learning algorithms – also time-effective way to document avalanche activity over large areas. Making use of these technological advances, we compared the avalanche activity for three periods with widespread activity of very large and extremely large avalanches, when the highest danger level 5 (very high) was forecast for large parts of the Swiss Alps. In these three periods (in 1999, 2018, 2019), avalanches were captured with different remote-sensing instruments: in 1999, with airplane imagery, in 2018 and 2019 with multispectral satellite data. Comparing the activity of all three periods to Large Scale Hazard Indication Modelling (LSHIM) of avalanches with a 100-year return period allowed to compare how much of the potential avalanche terrain was active and to quantitatively compare activity between these periods. We found that 19% of the avalanche release areas showed activity in 1999 compared to 16% in 2018 and 8% in 2019. Considering the avalanche area delimited using the 100-year return period, 17% were active in 1999, 11% in 2018 and 6% in 2019. By comparing the three avalanche periods, we contribute to better understand the extent and return periods of very large and extremely large avalanches (size 4 and 5) and demonstrate, how avalanche mapping from remotely sensed data can make avalanche databases more complete.

    Object ID: ISSW2024_O9.1.pdf

    Language of Article: English

    Presenter(s): Elisabeth D. Hafner

    Keywords: avalanche mapping, potentially active area, danger level 5 (very high)

    Page Number(s): 1222 - 1229

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