FLOOD10728 - Laserfiche WebLink

Home Browse Search

Approximate elevations were determined by applying the regional discharge-drainage area information to the Animas River and Cunningham Creek in the areas selected for approximate study. Elevations were determined using this discharge and a typical valley cross section as determined from a u.s. Geological Survey topographic map (Refer- ence 13). All elevations are referenced to the National Geodetic Vertical Datum of 1929 (NGVD). Elevation reference marks used in the study are shown on the maps. 4.0 FLOOD PLAIN MANAGEMENT APPLICATIONS A prime purpose of the National Flood Insurance Program is to encourage State and local governments to adopt sound flood plain management pro- grams. Each Flood Insurance Study, therefore, includes a flood boundary map designed to assist communities in developing sound flood plain manage- ment measures. 4.1 Flood Boundaries In order to provide a national standard without regional discrimina- tion, the lOO-year flood has been adopted by the Federal Insurance Administration as the base flood for purposes of flood plain manage- ment measures. The SOO-year flood is employed to indicate additional areas of flood risk in the community. For each stream studied in detail, the boundaries of the 100- and SOQ-year floods have been delineated using the flood elevations determined at each cross section; between cross sections, the boundaries were interpolated using topographic maps at scale of 1:2400, with a contour interval of 2 feet (Reference 14). The shallow flooding on Mineral Creek west of the Denver and Rio Grande Western Railroad was delineated using topographic maps at a scale of 1:2400, with a contour interval of 2 feet (Reference 14). On Cement Creek, shallow flooding occurs on the adjacent properties. The lOa-year flood boundaries were delineated using the flood eleva- tions computed with the flow staying in the creek only. The boun- daries of shallow flooding due to the IOO-year flood are not shown because they are confined within the SOQ-year flood boundaries. The SOQ-year flood boundaries upstream from the u.s. Highway 110 bridge were determined using the computed flood elevations. Downstream from the bridge, where shallow flooding occurs, the boundaries were delineated by considering possible spread of floodwaters. On Mineral Creek downstream from u.s. Highway 550, where overflow occurs, the SOQ-year flood boundaries were determined, with considera- tions of possible flood route. 11