A snow fence is a barrier deployed to manage the movement of wind-blown snow. Unlike a solid wall, this structure is designed to influence the aerodynamics of the wind stream. Its primary function is to capture snow particles and force their deposition into a designated area, preventing the formation of deep snowdrifts where they could cause disruption. These fences are a low-cost tool for winter weather management in areas prone to high winds and heavy snowfall.
The Science of Snow Deposition
Snow fences operate by aerodynamic principles rather than acting as a solid obstruction. As wind approaches the fence, the structure slows the air speed directly behind it, reducing the wind’s capacity to carry suspended snow particles. This velocity reduction causes the airborne snow to fall out of the airstream and settle on the ground.
The design of the fence, which incorporates deliberate gaps, creates turbulence on the downwind side, leading to a localized drop in pressure and wind energy. This effect establishes a predictable “deposition zone” where the snow accumulates in a large, elongated drift. This controlled accumulation stores the snow away from the area the fence is intended to protect.
Most snow accumulation (sometimes 85% or more) occurs on the downwind side of the barrier due to turbulence and deposition. Trapping efficiency is directly related to the fence’s ability to manipulate the airflow and precipitate the snow load.
Protecting Transportation Corridors
The most widespread application for snow fences is protecting transportation networks, including highways, local roads, and railway lines. Blowing snow quickly deposits massive drifts onto travel surfaces, leading to sudden blockages and dangerous driving conditions. Fences are installed on the upwind side of these corridors to capture snow before it reaches the pavement.
By intercepting the snow, these barriers significantly improve visibility for drivers, especially during high-wind events when blowing snow can cause whiteout conditions. Reducing the frequency and size of drifts directly lowers the risk of accidents associated with reduced sightlines and unexpected snow buildup.
For transportation agencies, this pre-emptive snow management translates into substantial operational savings. Studies indicate that trapping snow with fences can be up to 100 times more economical than the repeated mechanical plowing and removal of drifts from roadways. This cost-effectiveness is a major factor in their deployment across northern climates.
Minimizing the need for heavy plowing and the application of de-icing chemicals reduces wear on the road surface and lessens the environmental impact of road salts on local waterways. The goal is maintaining safe, continuous access by keeping the travel surface clear of accumulation throughout the winter season.
Infrastructure and Environmental Uses
Beyond maintaining clear roads, snow fences serve important environmental and infrastructure protection roles. In agricultural settings, they conserve soil by acting as a windbreak against erosion during the winter months. The fence slows the surface wind, preventing the loss of topsoil that would otherwise be carried away from open fields.
Fences are tools for water conservation, particularly in arid or semi-arid regions. By creating large snowdrifts, they store water in a controlled location. When this snow melts slowly in the spring, it increases the soil moisture content, benefiting crops and vegetation during the subsequent growing season.
These structures also shield specific infrastructure from damaging snow loads. Buildings, communication towers, or utility pipelines can be protected from deep, heavy drifts that might otherwise accumulate against them. This application is useful for isolated or unattended facilities where mechanical snow removal is impractical.
In recreational areas, such as mountain resorts, snow fences can be used to manage snow distribution for practical purposes. They help increase the snow depth on ski slopes or in designated recreational zones, and in some high-altitude areas, they are part of a broader strategy for avalanche control.
Essential Design and Installation Factors
The effectiveness of a snow fence is determined by precise engineering and placement factors. One important design element is the fence’s porosity, which refers to the ratio of open space to solid material. Optimal snow-trapping performance is achieved when the fence has a porosity between 40% and 50%.
This specific porosity ensures that enough wind passes through the barrier to create the necessary turbulence and eddy currents for maximum snow deposition. Taller fences store significantly more snow, making a single tall fence more economical and effective than multiple shorter rows.
A second performance factor is the required setback distance, which is the space needed between the fence and the object being protected. For a typical porous fence, the barrier must be placed upwind at a distance of at least 35 times its height (35H) to allow the full snowdrift to form completely away from the protected area.
Additionally, a small gap, typically 10% of the fence height, must be maintained between the bottom of the fence and the ground. This prevents the fence from being completely buried by initial snow accumulation, which would render the aerodynamic effect useless for the remainder of the season.