by: Bruce Clevenger, Defiance County
Posted by Glen Arnold, Putnam County
Snow fences can be an effective and economical way of improving snow management. They keep snow and ice off driveways and roads while increasing driver visibility by reducing the force of the wind on the snow. A 2006 report by Tabler & Associates revealed that snow fences helped reduce accidents caused by poor visibility by up to 70% along I-80 in southeastern Wyoming.
Snow fences may also reduce time and energy of traditional snow removal. However, on private property, a poorly placed fence can be ineffective or do more harm than good. Traditionally, property owners are installing snow fence in late fall or early winter. Once the ground freezes and receives snow, it may be too late to install.
Snow fence is generally not a solid fence. Fence openings should be 2 to 2 1/2 inches wide (openings wider than 6 inches are ineffective) and may run vertically or horizontally. Wind speeds up as it passes through the restricted openings, thus preventing snow from plugging the immediate area around the fence. The wind slows down after passing through the fence and drops much of its load of snow.
Generally, a snow fence should be installed at a distance of 20-35 times its height from the edge of the protection area (ie. driveway). That is, if you were installing a four-foot-high fence, it would need to be at least 80-140 feet from the protection area to be effective. This distance will set the fence far enough away to allow snow to accumulate before the fence and between the fence and the driveway, rather than over and on the driveway itself.
Wind velocity and fence height determine the size of the protected area. For instance, when the wind is blowing at 10 mph, a 6-foot-high porous fence will reduce that velocity to a minimum 10 feet downwind from the fence. When the wind is 20 mph, the minimum velocity point will be 65 feet from the fence; and at 30 mph, the area protected is about 90 feet downwind.
A gap of approximately 10% of the fence’s height should be left underneath the snow fence. If you were installing a fence with a height of four feet, you would want to install the fence with 4–5 inches between the bottom of the fence and the ground. This gap will prevent snow from accumulating near and on the fence. This will reduce extra weight and damage from snow accumulation and increase the effectiveness of your fence.
A common pitfall in snow fence installation is placing a fence too close to or too far from the protection area. A fence too close to the protection area can actually increase the amount of snow deposited. A fence too far from the area will allow the wind to pick snow back up and deposit it on the road. It is best to properly measure the distance and, if needed, to install multiple fences.
A snow fence should also extend approximately 20 feet or 30 degrees past the length of the area intended for protection. This will reduce the effect of wind wrapping around the edge of the fence, increasing the area of coverage. Extending the fence also helps protect against a larger variation of wind directions. The orientation of the snow fence should be parallel to the driveway and perpendicular to prevailing winds. However, the makeup of the terrain may alter fence placement. An adjustment in a fence’s angle up to 25 degrees will not significantly detract from the fence’s effectiveness.
An effective snow fence is both science and an art. Trial and error will increase success of using a snow fence. Winter weather may provide a variety of wind directions and precipitations. Snow fences can help reduce dangers and reduce the costs of snow removal to provide better snow management.