Item: Design and Construction of Snow Supporting Structures for the Milepost 151 Avalanche, Jackson, Wyoming
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Title: Design and Construction of Snow Supporting Structures for the Milepost 151 Avalanche, Jackson, Wyoming
Proceedings: International Snow Science Workshop Grenoble – Chamonix Mont-Blanc - October 07-11, 2013
Authors:
- Joshua T. Hewes [ Northern Arizona University, Flagstaff, AZ, U.S.A. ]
- Rand Decker [ Northern Arizona University, Flagstaff, AZ, U.S.A. ]
- Scott M. Merry [ University of the Pacific, Stockton, CA, U.S.A. ]
Date: 2013-10-07
Abstract: Reduction and management of avalanche threats to motorists on roads and highways threatened by avalanches can be accomplished by use of constructed defence structures (snow bridges or rakes) in the avalanches’ starting zones. The United States (US) has, as a general practice, relied on forecasting and artificial avalanche release to manage risk. Due to increased traffic volumes on rural, mountainous roads, including interstate highways, the probability of interaction of avalanches with motorists increased. Consequently, US engineers and transportation officials have now begun to consider “other options†for avalanche hazard reduction, and these include constructed, or “passive†protective measures in the avalanche starting zones and run-out paths. The Wyoming Department of Transportation (WYDOT) has evaluated options for constructed defence for the Milepost 151 Avalanche which threatens US Hwy 89/191 south of the community of Jackson. In 2006 a project was initiated to develop designs that reflect US domestic design methodologies and materials specifications for snow supporting structures (SSS) to be constructed in the 151 Avalanche starting zone. A US domestic design capacity, building on decades of European experience, has been established for the design and implementation of snow supporting structures (SSS) for the reduction of avalanche hazards in transportation applications. The absences of SSS technology in the US is not due to a lack of avalanches. This absence can be attributed to two factors; the success of US avalanche forecasting and active control methodologies, and the unsightly appearance of SSS in alpine settings with high quality scenic attributes. The value of scenic attributes to be found on Federal or public lands is subject to the decision analysis process of the National Environmental Policy Act (NEPA) i.e. Environmental Impact Statements (EIS) and Environmental Assessments (EA). The NEPA decision criteria with respect to scenic visual attributes is known as “visual retention†and requires the visual attributes of the construction site and resulting facility be the same after construction as it was before. Collaboration between stakeholders on the 151 Avalanche lead to a SSS deployment configuration in the 151 Avalanche starting zone that mimics visual elements of the natural landscape. This organic configuration of SSS, coupled with botanical restoration, has successfully addressed NEPA visual retention requirements for the 151 Avalanche.
Object ID: ISSW13_paper_O1-15.pdf
Language of Article: English
Presenter(s): Unknown
Keywords: avalanche, hazard, transportation, snow structure, nepa, visual retention
Page Number(s): 783-787
Subjects: avalanche hazard avalanche hazard forecasting avalanche control
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