Item: Forest Damage by Wet and Powder Snow Avalanches
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Title: Forest Damage by Wet and Powder Snow Avalanches
Proceedings: International Snow Science Workshop 2014 Proceedings, Banff, Canada
Authors:
- Thomas Feistl [ WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland ] [ Technical University Munich, Munich, Germany ]
- Peter Bebi [ WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland ]
- Stefan Margreth [ WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland ]
- Perry Bartelt [ WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland ]
Date: 2014-09-29
Abstract: Wet and powder snow avalanches can break, uproot and overturn trees, causing widespread damage to forests. Mapping the extent of forest damage is a useful method to estimate and delineate the avalanche pressure field and therefore a valuable tool in mitigation studies. The impact forces of avalanches on trees, however, depend strongly on the avalanche flow regime. In this paper, we analyzed the flow dynamics of two characteristic avalanche types with the goal of relating avalanche flow regime to forest damage. Powder avalanches are characterized by a high velocity but low density suspension cloud. Evergreen trees oppose a large area to the powder blast and are prone to overturning. The destructive force of powder clouds is governed primarily by their expansion velocity, height and density. In comparison, wet snow avalanches have lower velocity and higher density. Plug-like wet snow avalanches exert large quasi-static forces at lower stem heights. Using an avalanche dynamics model that simulates both powder and wet snow avalanches, we studied two well-documented case studies. A critical impact force could be found for specific tree types independent of the avalanche flow regime. We also found that the forces exerted by wet snow avalanches cannot be calculated with velocity dependent drag laws. We propose a method to determine wet snow avalanche pressures on trees by calculating the quasi-static forces which depend on the avalanche volume and terrain features. Our work contributes to the general understanding of tree-avalanche interaction and enables the prediction of forest damage in avalanche modeling.
Language of Article: English
Presenters:
Keywords: avalanche dynamics, forest damage, modeling.
Page Number(s): 700-707
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Digital Abstract Not Available
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