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<br />All elevations are referenced to the National Geodetic Vertical <br />D"l:um of 1929 (NGVD). Elevation reference marks used in this <br />study are shown on the maps. <br /> <br />4.0 FLOODPLAIN MANAGEMENT APPLICATIONS <br /> <br />The NFIP encourages State and local governments to adopt sound flood- <br />plain management programs. Therefore, each Flood Insurance Study <br />includes a floodplain boundary map designed to assist communities in <br />developing sound floodplain management measures. <br /> <br />4.1 rloooplain Boundaries <br /> <br />To provide a nat ional standard wi thout regional di scrimination, <br />the l percent annual chance (lOO-year) flood has been adopted by <br />FEMA as the base flood for floodplain management purposes. For <br />each stream studied by detailed methods, the 100-year floodplain <br />boundaries have been delineated using the flood elevations <br />determined at each cross section. <br /> <br />Between cross sections, the boundaries were interpolated using <br />topographic maps at a scale of 1:400, with contour intervals of 2 <br />feet and 10 feet NGVD (Reference 1). <br /> <br />The 100-year floodplain boundaries are shown on the Flood <br />Insurance Rate Map (FIRM) (Exhibit 2). On this FIRM, the 100- <br />year floodplain boundary corresponds to the boundary of the areas <br />of special flood hazards (Zone AE and AO). Small areas within <br />the floodplain boundaries may lie above the flood elevations but <br />cannot be shown due to limitations of the map scale and/or lack <br />of detailed topographic data. <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 />and increases flood hazards in areas beyond the encroachment. <br />One aspect of floodplain management involves balancing the <br />economic gain from floodplain development with the resulting <br />potential increase in flood hazard. For purposes of the NFIP, a <br />floodway is used as a tool to assist local communities in this <br />aspect of floodplain management. Under this concept, the area of <br />the 100-year floodplain is divided into a floodway and a floodway <br />fringe. The floodway is the channel of a stream, plus any <br />adjacent floodplain areas that must be kept free of encroachment <br />so that the 100-year flood can be carried without any substantial <br />increase in flood height. Minimum federal standards limit such <br />increases to 1.0 foot, provided that hazardous velocities are not <br />produced. <br /> <br />Floodways were not determined for this Flood Insurance Study. <br /> <br />7 <br />