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A snow fence, similar to a sand fence, is a type of fence that forces windblown, drifting snow to accumulate in a desired place. They are primarily employed to minimize the amount of snowdrift on roadways and railways. Farmers and ranchers use snow fences to create drifts in basins for a ready supply of water in the spring. Ski resorts also use snow fences in order to increase snow depth in specified areas, or for avalanche control. Temporary snow fences are usually one of two varieties: perforated orange plastic sheeting attached to stakes at regular intervals (the type usually used for construction site fencing or temporary sports field fencing), or a cedar or other lightweight wood strip and wire fence, also attached to metal stakes. A permanent snow fence usually consists of poles with horizontal planks running across them so that they cover just over one-half of the total fence area. The bottom 10% to 15% of the fence should be left open so that snow does not settle directly under the fence, which would reduce its effective height. Taller fences trap more snow. Taking the height of the fence as one unit, it should be placed thirty-five units or more to windward of the road or building that it is meant to protect. Permanent snow fences can also consist of lines of closely spaced shrubs, conifer trees or maize stalks. Snow fences work by causing turbulence in the wind, such that it drops much of its snow load on the lee side of the fence. Thus, snow fences actually cause snow drifts, rather than preventing them. The fences are placed so as to cause a snow drift where it is beneficial, or not harmful so that the snow does not drift onto undesired areas such as roads or among buildings. ==See also== * Snow shed, which is designed so that snow collects on top * Snow guard, a device attached to roofs to prevent snow from falling on people below 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「snow fence」の詳細全文を読む スポンサード リンク
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