Laserfiche WebLink
<br />Calculation of normal depth from field cross section and the <br />estimation of top width was used to plot flooding for approximate <br />study areas. <br /> <br />4.0 FLOODPLAIN MANAGEMENT APPLICATIONS <br /> <br />The NFIP encourages State and local governments to adopt sound <br />floodplain management programs. Therefore, each Flood Insurance Study <br />provides 100-year flood elevations and delineations of the 100- and SOO- <br />year floodplain boundaries and 100-year floodway to assist communities <br />in developing floodplain management measures. <br /> <br />4.1 Floodplain Boundaries <br /> <br />To provide a national standard without regional discrimination, the <br />I-percent annual chance (lOO-year) flood has been adopted by FEMA <br />as the base flood for floodplain management purposes. The 0.2- <br />percent annual chance (SOO-year) flood is employed to indicate <br />additional areas of flood risk in the community. For Sulphur and <br />Tallman Gulches, the 100- and SOO-year floodplain boundaries have <br />been delineated using the flood elevations determined at each cross <br />section. Between cross sections, the boundaries were interpolated <br />using topographic maps at a scale of 1:24,000, with a contour <br />interval of 10 feet (Reference 20). <br /> <br />Floodplain boundaries for Cherry Creek were taken from the <br />previously referenced COE Floodplain Information report for Cherry <br />Creek-Cherry Creek Lake through Franktown, Colorado, (Reference <br />12). That study was also used to determine the boundaries at the <br />confluences with the Cherry Creek tributaries included 1n this <br />study. <br /> <br />The 100- and SOO-year floodplain boundaries are shown on the FIRM <br />(Exhibit 2). On this map, the laO-year floodplain boundary <br />corresponds to the boundary of the areas of special flood hazards <br />(Zone(s) A and AE), and the SOO-year floodplain boundary <br />corresponds to the boundary of areas of moderate flood hazards. In <br />cases where the 100- and SOO-year floodplain boundaries are close <br />together, only the lOa-year floodplain boundary has been shown. <br />Small areas within the floodplain boundaries may lie above the <br />flood elevations but cannot be shown due to limitations of the map <br />scale and/or lack of detailed topographic data. <br /> <br />Approximate lOa-year floodplain boundaries were delineated on the <br />previously referenced topographic maps (Reference 20). <br /> <br />For the streams studied by approximate methods, only the lOa-year <br />floodplain boundary is shown on the FIRM (Exhibit 2.) <br /> <br />4.2 Floodways <br /> <br />Encroachment on floodplains, such as structures and fill, reduces <br />flood-carrying capacity, increases flood heights and velocities, <br /> <br />10 <br />