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%140� N R C S Rock <br />Natural Resources <br />Conservation Service Check <br />USDA NRCS 2012 Fact Sheet <br />NOTE <br />A small rock dam constructed across a drainage way, swale or road ditch. <br />Rock Check Dams are used where runoff is concentrated in a drainage way, swale, or <br />road ditch that has lost all its natural protection due to the fire, or will receive increased <br />flow rates as a result of fire in the contributing drainage area. The rock dams will reduce <br />erosion and trap sediment generated from adjacent areas or the ditch itself. Rock Check <br />Dams should be limited to use in open channels that drain 50 acres or less. <br />'I he maximum height of the rock check nam shouts not exceed S.0 teet. 1ne top or <br />the dam should be at least 1 foot below the top of the channel or Swale. The top width <br />should be a minimum of 3 feet. The maximum spacing between the dams should be as <br />follows: <br />Channel Slope <br />o <br />�0 <br />Rock Check <br />Dam Spacing <br />(feet) <br />Dam Height, H <br />1 ft 2ft <br />3ft <br />< 2 <br />100 <br />200 <br />200 <br />2 - 5 <br />40 <br />80 <br />120 <br />5-10 <br />20 <br />40 <br />60 <br />10-15 <br />13 <br />25 <br />40 <br />15-20 <br />10 <br />20 <br />30 <br />> 20 <br />not recommended <br />The center of the dam shall be at least 1.5 feet lower than the sides. The base of the <br />dam should be keyed into the channel bottom to a depth of 2 feet. The ends of the dam <br />should be keyed into the channel sides a minimum of 4 feet. The rock should be of suf- <br />ficient size and quality to meet Colorado Department of Transportation specifications for <br />9 inch D50 Rock Riprap. <br />Helping People Help the Land <br />USDA is an equal opportunity provider and employer <br />