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<br />4.0 FLOOD PLAIN }~NAGEMENT APPLICATIONS <br /> <br />A prime purpose of the Natonal Flood Insurance Program is to encourage <br />State and Local governments to adopt sound flood plain management pro- <br />grams. Each Flood Insurance Study, therefore, includes a flood boundary <br />map designed to assist communities in developing sound flood plain manage- <br />ment measures. <br /> <br />4.1 Flood Boundaries <br /> <br />In order to provide a national standard without regional discrimina- <br />tion, the 100-year flood has been adopted by the Federal Lmergency <br />}lanagement Agency as the base flood for purposes of flood plain <br />management measures. The SOD-year flood is employed to indicate <br />additional areas of flood risk in the community. For each stream <br />studied in detail, the boundaries of the 100- and SOO-year floods <br />have been delineated using the flood elevations determined at each <br />cross section; between cross sections, the boundaries were interpolated <br />using topographic maps at scale of 1:1200, with a contour interval <br />of 1 foot (Reference 9). <br /> <br />In cases where the 100- and SOO-year flood boundaries are close <br />together, only the 100-year flood boundary has been shown. <br /> <br />Flood boundaries are indicated on the Flood Insurance Rate 11ap <br />On this map, the 100-year flood boundary corresponds to the boundary <br />of the areas of special flood hazards (Zones Al and A3); and the <br />SOO-year flood boundary corresponds to the boundary of the areas <br />of moderate flood hazards (Zone B). <br /> <br />Small areas within the flood boundaries may lie above the flood <br />elevations and, therefore, not be subject to flooding; owing to <br />limitations of the map scale, such areas are not shown. <br /> <br />4.2 Floodways <br /> <br />The floodway is the channel of a stream, plus any adjacent flood <br />plain areas, that must be kept free of encroachment in order that <br />the lOO-year flood be carried without substantial increases in <br />flood heights. <br /> <br />In the Town of Frederick, the floodway concept does not apply <br />because the present development within the flood plain has caused <br />the elimination of a defined channel and flow path through town. <br /> <br />7 <br />