The Weather Notebook: Snow Fences

Snow Fences
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Hi, I'm Dave Thurlow for the Mount Washington Observatory and this is The Weather Notebook. Blowing and drifting snow is sure common up here on the mountain, and out on the open western plains. In the East we don't do anything about it but:

Snow fence along side of Highway 37 in Idaho.
"Out west, they use large snow fences to prevent drifting on the interstate highways."

That's Jim Lever, a snow researcher at the Cold Regions Research and Engineering Lab, in Hanover, NH. On the day I visited, he was doing a series of wind tunnel tests on model snow fences, which look kind of like old split rail fences. Jim explains how they work:

JL: "The wind goes through the fence because it's porous and it loses a lot of energy in doing so, so the particles of snow that go through with the wind fall into this dead zone of air behind the fence.

DT: So, it's allowing the snow to go over it and through it, but it's just kind of influencing it to stay in place.

JL: It causes the air speed to slow down so much that the snow drops out. Stops right there."

And because the snow stops right there, snowplows don't have to keep clearing the same road, making snowfences very cost effective:

"It's cheaper to build several miles of snow fences than it is to plow that same several mile stretch by a factor of 10. It's much, much cheaper."

Snow fences are placed surprisingly far from the road to be most effective, a fact that with out wind tunnel research would have been discovered by much trial and error.

For pictures of snow fences, be sure to visit our website at weathernotebook.org. The Weather Notebook is produced by Bryan Sejvar and engineered by Sean Doucette. The music you hear playing in the background was composed and performed by Georg Brandl. The Weather Notebook is underwritten by Subaru and the National Science Foundation.