Designing a Living Snow Fence for Snow Drift Control

摘要

Blowing and drifting snow continues to be a transportation and safety hazard with significant economic costs. Critical design criteria for the construction of a living (vegetated) snow fence are reviewed and presented using the most currently available design equations. Coupled with an analysis of climate and topographical data, the design criteria are applied to an area in Rocky Mountain National Park historically prone to snow drifting. The long-term average snow accumulation season (period beginning with the first blowing snow and ending with maximum drift density) was calculated from air temperature as between 4 November and 10 April, and these dates compared well with those based on nearby snow observations. Over the snow accumulation season, the potential for snow transport based on wind characteristics was 21.4 tonnes m(-1) (all wind directions), of which 21.0 tonnes m(-1) occurred along a mean drifting direction of 259 degrees (nearly perpendicular to the road at the study site). The potential for snow transport based on snow characteristics (754 tonnes m(-1)) exceeded the potential for snow transport based on wind characteristics, thus indicating that wind was the primary factor controlling drift formation. Using a snow transport of 23.9 tonnes m(-1), determined using the long-term average snow water equivalent plus one standard deviation (occurred in three out of 25 years of observations), the required snow fence height needs to be 1.61 m tall, set back 56.4 m from the road. The fence will have a trapping efficiency of 79% when an effective porosity of 50% is achieved. Comparisons of these design parameters to snow drift conditions created behind a structural fence indicated that living snow fence design parameters are likely appropriate and realistic.