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<br />The approximate flooding on Crow Creek was determined from normal- <br />depth calculations and weir calculations at a county road. The <br />approximate flooding on [daho Creek was based upon engineering <br />judgment and field inspection. <br /> <br />All elevations are referenced to the National Geodetic Vertical <br />Datum (NGVD) of 1929. Elevation reference marks used in this study <br />and the descriptions of those marks, are shown on the maps. <br /> <br />4.0 FLOODPLAIN MANAGEMENT APPLICATION <br /> <br />The National Flood Insurance Program (NFIP) encourages State and local <br />governments to adopt sound floodplain management programs. Therefore, <br />each Flood Insurance Study provides 100-year flood elevations and <br />delineations of the 100- and 500-year floodplain boundaries and 100-year <br />flaodway to assist communities in developing floodplain management <br />measures. <br /> <br />4.1 Floodplain Boundaries <br /> <br />In order to provide a national standard without regional <br />discrimination, the 100-year flood has been adopted by FEMA as the <br />base flood for floodplain management purposes. The 500-year flood <br />is employed to indicate additional areas of flood risk in the <br />community. For each stream studied in detail, the boundaries of <br />the 100- and 500-year floods have been delineated using the flood <br />elevations determined at each cross section; between cross <br />sections, the boundaries were interpolated using topographic and <br />photogrammetric maps at the scale .and contour interval as follows <br />for each stream: <br /> <br />South Platte River (detailed study from City of Evans to <br />confluence with Cache La Poudre River), scale 1:24,000, <br />enlarged to a scale of 1:7,200, with a contour interval of 10 <br />feet (Reference 21) <br /> <br />Cache La Poudre River, scale 1: 12,000 enlarged to a scale of <br />1:7,200, with a contour interval of 4 feet (References 4 and <br />22) <br /> <br />Sheep Draw, scale 1:2,400, with a contour interval of 2 feet <br />(Reference 17) <br /> <br />Ashcroft Draw, scale 1:24,000, enlarged to a scale of 1:7,200, <br />with a contour interval of 10 feet (References 7 and 10) <br /> <br />Eaton Draw, scale 1:24,000, enlarged to a scale of 1:7,200, <br />with a contour interval of 10 feet (Reference 11) <br /> <br />Tri -Area Drainageway, scale 1: 24,000, enlarged to a scale of <br />1:7,200, with a contour interval of 1 foot (Reference 16) <br /> <br />15 <br />