FLOOD01637 - Laserfiche WebLink

Home Browse Search

Creek was determi ned by means of the slope-area method. In the overflow areas of Cottonwood Creek, were shallow flooding exists, wa ter surface e levat i on s conta i ned in Reference 1 were determi ned utilizing the WSPZ Computer Program (Reference 3). Cross-sections were obtained from topographic mapping (Reference 5), along each of the overflow areas delineated. A field check of the Arkansas River at Buena Vista was performed in May of 1980. The banks of the river ranged from 30' to 50' in height. It was determined that a 100-year flood would not overflow the banks inundating the Town of Buena Vista. USGS 7 1/2-minute quadrangle maps were used to delineate the approximate 100-year flood boundary for this reach of the Arkansas River in Buena Vista (Reference 6). Horizontal control is based on Colorado State Plane Coordinate System South Zone 1929 USC & GS Sea Level Datum. Elevation reference marks used in this study are shown on the maps. 4.0 FLOOD PLAIN MANAGEMENT APPLICATIONS The National Flood Insurance Program encourages state and local govern- ments to adopt sound flood p 1 a in management programs. Therefore, each Flood Insurance Study includes a flood boundary map designed to assist communities in developing sound flood plain management measures. 4.1 Flood Boundaries In order to provide a national standard without regional discrimina- tion, the 100-year flood has been adopted by FEMA as the base flood for purposes of flood plain management measures. The 500-year flood is employed to indicate additional areas of flood risk in the com- munity. For each stream studied in detail, the boundaries for the 100- and 500-year floods have been delineated using the flood eleva- tions determined at each cross section; between cross sections, the boundar ies were i nterpo 1 ated using topographi c maps at sca le of 1:2400, with a contour interval of 2 feet (Reference 5). In cases where the 100- and 500-year fl ood boundari es are close together, only the 100-year flood boundary has been shown. Flood boundaries for the 100- and 500-year floods are shown on the Flood Boundary and Floodway Map. Small areas within the flood bound- aries may not lie above the flood elevations and, therefore, may not be subject to flooding. Owing to limitations of the map scale, such areas are not shown. 4.2 Floodways Encroachment on flood plains, such as artificial fill, reduces the flood-carrying capacity and increases flood heights, thus increasing flood hazards in areas beyond the encroachment itself. One aspect of 8