Item: Linking Snow Cover Properties and Avalanche Dynamics
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Title: Linking Snow Cover Properties and Avalanche Dynamics
Proceedings: International Snow Science Workshop 2014 Proceedings, Banff, Canada
Authors:
- Walter Steinkogler [ WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland ] [ CRYOS, School of Architecture, Civil and Environmental Engineering, EPFL, Lausanne, Switzerland ]
- Betty Sovilla [ WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland ]
- Michael Lehning [ WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland ] [ CRYOS, School of Architecture, Civil and Environmental Engineering, EPFL, Lausanne, Switzerland ]
Date: 2014-09-29
Abstract: Avalanches exhibit many different flow regimes from powder clouds to slush flows with fundamentally different flow dynamical characteristics, such as velocities and run-out distances. To explain these varying flow dynamics the snow cover properties must be taken into account. Recent investigations showed that the temperature of the flowing snow to be one of the most important factors controlling the avalanche typology and thus the flow dynamics. Our investigations allowed for the first time to quantify the relative contribution of the temperature in the released and entrained snow versus the temperature increase from frictional processes. Additionally, it was found in laboratory experiments that below a temperate threshold of -1ËšC a significant densification could be observed, yet the moving particles remained individual and cohesionless at the crystal scale. Such cold and dry snow is typically found in dry-dense flowing and powder avalanches. As soon as the snow was warmer than -1ËšC, distinct granules of varying sizes and properties formed and resulted in much more cohesive and larger particles, as found in moist and wet avalanches. These variations and transitions in granule structures as a function of temperature are at the basis for different flow regimes in avalanches. The results of this study are of significant interest for engineering problems, enhancements of avalanche dynamics models and forecasting. For example, snow safety personnel should be aware of snow cover property variations, e.g. altitude of 0ËšC line, since unexpected and atypical avalanche flow behavior, such as variations in expected run-out distance and flow direction, can occur.
Language of Article: English
Presenters:
Keywords: Snow avalanche, snow temperature, mobility, flow dynamics.
Page Number(s): 164-169
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Digital Abstract Not Available
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