Snow Fence

As the snow melted this week, it became clear how much snow piled up on the downwind side of my snow fence instead of on my driveway.

A well-placed, well-built snow fence can do a lot to make life easier, but before you begin, there are some things you need to know. If it isn’t done right, it can backfire on you and actually make things worse.

There is nothing you can do, short of cloud seeding, to add to or reduce the total amount of snow that falls on your property. But you can do things that have an impact on where that snow gathers, or drifts, under the influence of the wind. Whether it’s a snow fence, a line of trees, a wall, or a berm, the purpose of a windbreak is not to block snow from drifting but to cause drifting where you want it, leaving less to pile up where you don’t.

A good 4-foot snow fence will have a surprising effect on the snow depths downwind, but you have to understand what the outcome will be before you place it. Remember, the fence does not block drifting snow; it creates a drift by slowing down the wind, making it drop some of its snow. This creates a small drift on the upwind side of the fence but a larger one downwind. If you place your snow fence too close to your walkway or whatever you want to keep clear, that larger drift will make the snow deeper there, not exactly what the result you wanted.

Place your fence farther upwind from the place you want to protect than you think you should. A rule of thumb is that the snow fence should be 34 or 35 times the fence’s height away from the protected spot. That means a 4-foot snow fence should be placed no less than 136 feet from your driveway. (Good luck if that’s in your neighbor’s front yard.) Rules of thumb don’t always fit all, though. Factors like the strength of the prevailing wind, how heavy the snow is, and the porosity of your snow fence make a difference. But the point is that if you place your fence right next to, say, your driveway, it will drop more snow on your driveway, not less. Farther is better.

Since your snow fence will create drifting near it, try to plan it so that those drifts help you. Snow is water, so creating the drift on a field you plan to plant instead of your front step is a win/win situation.

Some other factors to consider when building a snow fence include the material you use, the strength and distance between the poles, and leaving a gap between the ground and the fence. Four-foot plastic snow fencing on a roll with about 50% porosity work well and doesn’t cost much, but in the wind and cold we have, it might not last through a good Teton Valley winter. Wooden slat fences may last longer but will cost more. Sturdy posts anchored deeply and solidly are a must; they are going to take a beating. And, of course, place the fence as closely as possible at a right angle to the prevailing winter wind, which is generally from the south around here.

As for that gap between the ground and the bottom of your fence, it is to let some wind blow under the fence too and reduce the snow build-up against it, which would shorten it and make it less effective. The rule of thumb for the gap is that it should be 10% of the fence’s height, so 5 inches for a 4 foot fence.

If you are interested in learning much more about the science behind snow fences and how best to build and place them, have I got a resource for you! Just look for anything written by the late Dr. Ronald D. Tabler, AKA The Wizard of Blizzard. His masterpiece, “Controlling Blowing and Drifting Snow with Snow Fences and Road Design”, is a great 300+ page read on a long winter’s day, or better yet, a beach read before the next snow season begins. Read fast.