Item: The Effects of Different Methods of Compaction on Snowpack Stability
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Title: The Effects of Different Methods of Compaction on Snowpack Stability
Proceedings: International Snow Science Workshop 2016 Proceedings, Breckenridge, CO, USA
Authors:
- Diana Saly [ Snow and Avalanche Lab, Montana State University, Bozeman, MT, USA ]
- Jordy Hendrikx [ Snow and Avalanche Lab, Montana State University, Bozeman, MT, USA ]
- Karl Birkeland [ USDA Forest Service National Avalanche Center, Bozeman, MT, USA ]
- Stuart Challender [ Snow and Avalanche Lab, Montana State University, Bozeman, MT, USA ]
- Tom Leonard [ Yellowstone Club Ski Patrol, Big Sky, MT, USA ]
Date: 2016-10-02
Abstract: The interaction between snowpack layers determines the snowpack stability. It follows that disrupting layers may improve stability. Ski patrols and guiding operations employ mechanical compaction methods such as boot packing, ski compaction, and explosives aiming to increase snowpack stability. High-usage backcountry areas (but still uncontrolled avalanche terrain) may become compacted, developing a snowpack with different characteristics than in lower usage adjacent terrain. A challenge in avalanche forecasting is determining how this compaction alters snowpack stability, if at all. Our results show that snow pack stability increases if compaction penetrates and impacts a weak layer, disrupts the failure plan, or affects slab cohesion. This is likely due to an increased probability of fracture arrest in a compacted snowpack from either slab or weak layer heterogeneity. While several compaction methods exist, specific research addressing different compaction techniques is lacking. This study compares the effects of different compaction methods on a snowpack. The snowpack for our case study consisted of an approx. 30 cm 1F wind slab over approx. 30 cm depth hoar. After applying mechanical compaction methods to nine slopes, we conducted ECTs and PSTs over six weeks to assess stability. We found ECTXs more common in compaction-dense areas (boot packed) than in compaction-light (skied and compaction free) areas. This research quantifies some of the effects of different compaction strategies, and provides preliminary guidance for avalanche practitioners on the most useful techniques for mitigating avalanche hazard.
Object ID: ISSW16_P2.02.pdf
Language of Article: English
Presenter(s):
Keywords: compaction, snowpack stability, stability test, boot-packing, ski compaction
Page Number(s): 716-720
Subjects: stability test boot packing snow compaction
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