Item: SCENARIO-BASED AVALANCHE SIMULATIONS INCLUDING SNOW ENTRAINMENT, SNOW TEMPERATURE AND DENSITY
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Title: SCENARIO-BASED AVALANCHE SIMULATIONS INCLUDING SNOW ENTRAINMENT, SNOW TEMPERATURE AND DENSITY
Proceedings: International Snow Science Workshop 2024, Tromsø, Norway
Authors:
- Lukas Stoffel [ WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland ]
- Perry Bartelt [ WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland ]
- Stefan Margreth [ WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland ]
Date: 2024-09-23
Abstract: Avalanche engineers use scenario-based simulations to predict avalanche runout and quantify impact pressures. An important input parameter for such simulations is the avalanche return period. In Switzerland, 10-, 30-, 100-, 300- and > 300-year avalanche return periods are taken into account for hazard assessment. Another important input parameter is the fracture depth which is determined with a procedure developed by SLF in 1990. Presently, the procedure provides no methodology to include snow entrainment, snow temperatures or snow density. This limitation hampers the application of advanced models that incorporate snow entrainment. The fracture depth is based on the determination of measured 3-day snow height increase using extreme value statistical approaches. The statistical values are modified to include the effects of altitude, snow drift accumulations and terrain (slope angle). The procedure provides fracture depths d0 for e.g. 10-, 30-, 100- and 300-year avalanche return periods. In this paper, we modify this well-known SLF procedure to determine snow entrainment depths d0* (erodible snow) which are associated with measured 3-day snow height increase. The erodible snow along the track is modified including altitude gradients and the slope angle. Within the framework of the proposed methodology, we demonstrate how to specify snow temperatures that are suitable for typical winter storms in the Alps, depending also on the altitude of the release area. These recommendations are based on snow profiles recorded during storm periods with heavy snow fall of February 1999 and January 2018, 2019 and 2021. The final component of the procedure is to provide a realistic snow density for the fracture slab. The procedure is straightforward, easily integrated into existing workflows, and benefits from relying on measurement data, ensuring realistic predictions of entrainment and deposition heights. Crucially, this method enables the examination of avalanche runout in a shifting climate marked by rising temperatures.
Object ID: ISSW2024_P2.11.pdf
Language of Article: English
Presenter(s): Lukas Stoffel
Keywords: Avalanche dynamics; snow entrainment, snow temperature, snow density, hazard evaluation, climate change
Page Number(s): 374 - 380
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