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<br />4.0 FLOOD PLAIN MANAGEMENT APPLICATIONS <br /> <br />A prime purpose of the National Flood Insurance Program is to <br />encourage State and local governments to adopt sound flood <br />plain management programs. Each Flood Insurance Study, there- <br />fore, includes a flood boundary map designed.to assist commu- <br />nities in developing sound flood plain management measures. <br /> <br />4.1 Flood Boundaries <br /> <br />In order to provide a national .standard without regional <br />discrimination, the lOa-year flood has been adopted by <br />the Federal Insurance Administration as the base flood <br />for purposes of flood plain management measures. The <br />50 a-year flood is employed to indicate additional areas <br />~ of flood risk in the community. For each stream <br />studied in detail, the boundaries of the lOa-year and <br />the SaG-year flood have been delineated using the flood <br />elevations determined at each cross section; between <br />cross sections, the boundaries were interpolated using <br />the topographic maps ata scale of 1:24,000 (Reference 14). <br /> <br />In cases where the lOa-and 500-year flood boundaries <br />are close together, only the lOa-year flood boundary <br />has been shown. <br /> <br />On Slaughterhouse Gulch, the flood plain has been delin- <br />eated to Fox Street and Powers Avenue. Above this <br />location, floodwaters will drain along streets and <br />through existing storm sewer systems. An indefinable, <br />relatively shallow flood profile will exist along the <br />many streets which drain the basin above this point. <br />Therefore, the flood outline has not been mapped for <br />the South Tributary to Slaughterhouse Gulch for the <br />reaches above Datura Street. In this area, the streets <br />serve as an adequate storm water drain. <br /> <br />Flood boundaries are indicated on the Flood Insurance <br />Rate Map. On this map, the lOa-year flood boundary <br />corresponds to the boundary of the areas of special <br />flood hazards (Zones AO, AI, A2, A3, A4, A5, A7, and <br />A15); and the 500-year flood boundary corresponds to <br />the boundary of the areas of moderate flood hazards <br />(Zone B). <br /> <br />Small areas within the flood boundaries may lie above <br />the flood elevations and, therefore, not be subject to <br />flooding; owing to limitations of the map scale, such <br />areas are not shown. <br /> <br />16 <br />