wpostServer: http://css.washingtonpost.com/wpost

The Post Most: Local

Posted at 03:00 PM ET, 01/10/2013

Snow fences: Do they still serve a purpose?

Last summer, while driving through the vast open spaces surrounding Denver International Airport (DIA), I was impressed by the equally vast array of snow fences, which seemed to stretch for miles. (Later, after driving up 14,200 foot Pike’s Peak — believe it or not — I caught a shot of an isolated snow shower during late summer).

After seeing so many miles of snow fences, I began to wonder whether these decidedly low-tech, old-fashioned structures were as valuable today, in this age of technology, as they were in the past. Although I knew the answer would be “yes” — otherwise they wouldn’t still be built — I wanted to investigate the cost-benefit ratio of the fences in serious “snow country.” But before expanding on the present-day utility of snow fences, it might be worthwhile to provide a brief history of how snow-clearing efforts evolved in the U.S.


( University of Wyoming Cooperative Extension Service - A typical snow fence.)
Snow fences are actually an ancient technology. Archaeologists have discovered what they believe is a 20-foot section of “snow fencing” near Stonehenge (circa 3000 B.C.) on England’s Salisbury Plain, an indication of what the English climate might have been like at that time.

Geologist/geophysicist Dr. Garry Denke believes the fence was used to channel drifting snow in predictable ways, possibly for water storage.

On the other hand, there’s also a theory that the fence may have been constructed to prevent prying peasant eyes from viewing ceremonial Stonehenge activities.

During the colonial era, deep snows often crippled mail service and overall commerce for days—and even weeks—at a time. Although snow-clearing ordinances weren’t yet in widespread use, cities and towns generally took matters into their own hands, clearing drifts so the sleighs could get through.

Ranchers learned that by erecting “snow fences” near the windward side of roadways and other areas they wanted to shield, significant savings in time and money could be achieved by minimizing snow-clearing operations.

Later, despite technological advances such as the Barber-Green Snowloader (introduced in Chicago in 1920), which plowed, scooped and dumped the snow into haulers, snow fences still maintained their popularity. At small airports, for example, runway-clearing costs could be greatly reduced by minimizing snow depth in critical areas. Overall, the sheer simplicity of snow fences struck a chord with farmers, ranchers, highway workers and the general public.

Today, in conjunction with many new and ingenious snow-clearing devices, such as the Next Generation Snow Plow, the Single-Lane-Obstructing Rotary Snow Plow, etc., snow fences have retained their popularity. In fact, they’ve even been improved upon, as the Japanese have developed a “blower snow fence,” which “increases air flow in the area of the fence, resulting in even less blowing snow on the roadway.”


( University of Wyoming Cooperative Extension Service - A September snow shower from near the top of Pike’s Peak in Colorado.)
So what exactly is a snow fence and how does it accomplish its task?

Although there are many kinds (living, wooden, plastic, etc.) the device is basically a porous barrier situated on the windward side of an area needing maximum snow protection, such as a highway. Upon meeting the barrier, snow-laden winds pass through with greatly diminished velocity, releasing most of the snow on the leeward side. For the fencing to be effective, designers obviously need to know and take into account the prevailing wind speed and direction as well as average snowfall rates during storms.

For every foot in length of a 4-foot tall snow fence, 4.2 tons of snow are held back

But possibly the most striking property of snow fences is revealed in a 2005 article in “Government Engineering,” a State of Wyoming publication. In the article, (the late) Ronald D. Tabler, of Tabler & Associates, calculated that mechanical snow removal costs about $3.00 for every 2.2 tons of snow. By comparison, for every foot in length of a 4-foot tall snow fence, 4.2 tons of snow, on average, are held back.

Thus, for a 20-foot section of snow fence, almost 85 tons of snow are stored, saving about $116.00, less installation and maintenance costs of the fencing! Tabler concluded that when the reduced number of highway injuries, deaths, and property damage claims were considered, the cost-benefit ratio of the fences was even more favorable.

And before you think that snow fences have only a solitary purpose, think again. They’ve also been found useful in avalanche control, water conservation, debris collection and, of course, beach erosion control, where blowing sand sometimes behaves as snow.

See any snow fences in your vicinity? I think there are some in rural Maryland and Virginia—and certainly some in Western Maryland. Let us know how effective they are and send in some pictures the next time we have some bona fide blowing and drifting snow in our area—when there is a next time!

By  |  03:00 PM ET, 01/10/2013

Categories:  Latest, Latest, Winter Storms

 
Read what others are saying
     

    © 2011 The Washington Post Company