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<br />All elevations are referenced to the National Geodetic Vertical <br />Datum of 1929 (NGVD). Elevation reference marks in the vicinity <br />of Estes Park are shown on the maps; other elevation mark data can <br />be obtained from the Larimer County Planning Commission. <br /> <br />. <br /> <br />4.0 <br /> <br />FLOOD PLAIN MANAGEMENT APPLICATIONS <br /> <br />. <br /> <br />The National Flood Insurance Program (NFIP) encourages State and local <br />governments to adopt sound flood plain management programs. Therefore, <br />each Flood Insurance Study produces maps designed to assist communities <br />in developing flood plain management measures. <br /> <br />4.1 FlOOd Boundaries <br /> <br />To provide a national standard without regional discrimination, <br />the 1 percent annual chance (lOO-year) flood has been adopted by <br />FEMA as the base flood for flood plain management purposes. The <br />0.2 percent annual chance (SOO-year) flood is employed to indicate <br />additional areas of flood risk in the community. For each stream <br />studied in detail, the 100- and SOO-year flood plain boundaries <br />have been delineated using the flood elevations determined at each <br />cross section. Between cross sections, the boundaries were inter- <br />polated using topographic maps at scales of 1:2,400, 1:1,200, and <br />1:6,000, with contour intervals of 2 and 4 feet (References 19, <br />20, 21, 23,' 24, 2S, 26, and 29). <br /> <br />On the Little Thompson River, approximate flood boundaries were <br />delineated using aerial photographs at a scale of 1:12,000 (Refer- <br />ence 27). Approximate flood boundaries for the Cache La Poudre <br />River were delineated from two COE Flood Plain Information reports <br />(References 6 and 28). <br /> <br />Approximate flood boundaries for Boxelder Creek and Cooper Slough <br />in the vicinity east of the City of Fort Collins were delineated <br />using topographic maps at a ,scale of 1:1,200 with a contour interval <br />of 2 feet (Reference 30). <br /> <br />," <br /> <br />The 100- and SOO-year flood plain boundaries are shown on the Flood <br />BOundary and Floodway Map (Exhibit 2). In cases where the 100- <br />and SOO-year flood plain boundaries are close together, only the <br />100-year flood plain boundary has been shown. Small areas within <br />the flood plain boundaries may lie above the flood elevations but <br />cannot be shown due to limitations of the map scale and/or lack of <br />detailed topographic data. <br /> <br />8 <br /> <br />For the streams studied by approximate methods, only the lOO-year <br />flood plain boundary is shown. <br /> <br />Approximate lOO-year flood plain boundaries in some portions of <br />the study area were taken directly from the Flood Hazard Boundary <br />Map (Reference 31). <br /> <br />19 <br /> <br />- <br />