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<br />. <br /> <br />. <br /> <br />,. <br /> <br />. <br /> <br />boundaries have been delineated using the flood elevations <br />determined at each cross section. Between cross sections, the <br />boundaries were interpolated using topographic maps at a scale of <br />1:1,200, with contour intervals of 4 and 20 feet (Reference 12). <br />For Beckers Lane Tributary, the 100- and 500-year floodplain <br />boundaries were delineated using topographic maps at a scale of <br />1:240, with a contour interval of 2 feet (Reference 14). <br /> <br />The approximate 100-year boundaries for the flows along Sutherland <br />Creek downstream of cross section A were delineated using <br />topographic maps as referenced above (Reference 12). <br /> <br />The approximate flood boundaries for Sutherland Creek upstream of <br />cross section M were taken from the E1 Paso County Flood Hazard <br />Boundary Map (Reference 13). <br /> <br />The 100-year flood boundaries for the remaining streams studied by <br />approximate methods were delineated using topographic maps enlarged <br />to a scale of 1:4,800, with a contour interval of 40 feet <br />(Reference 15). <br /> <br />The 100- and 500-year floodplain boundaries are shown on the Flood <br />Insurance Rate Map (Exhibit 2). On this map, the 100-year <br />floodplain boundary corresponds to the boundary of the areas of <br />special flood hazards (Zones A and AE); and the 500-year floodplain <br />boundary corresponds to the boundary of areas of moderate flood <br />hazards. In cases where the 100- and 500-year floodplain <br />boundaries are close together, only the 100-year floodplain <br />boundary has been shown. Small areas within the floodplain <br />boundaries may lie above the flood elevations but cannot be shown <br />due to limitations of the map scale and/or lack of detailed <br />topographic data. <br /> <br />For the streams studied <br />floodplain boundary is <br />(Exhibit 2.) <br /> <br />by approximate methods, only the 100-year <br />shown on the Flood Insurance Rate Map <br /> <br />4.2 <br /> <br />F100dways <br /> <br />Encr08.chment 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 />itself. One aspect of floodplain management involves balancing the <br />economic gain from floodplain development against the resulting <br />increase in flood hazard. For purposes of the NFIP, a ft'oodway is <br />used as a tool to assist local communities in this aspect of <br />floodplain management. Under this concept, the area of the 100- <br />year floodplain is divided into a floodway and a floodway fringe. <br />The f100dway is the channel of a stream, plus any adjacent <br />floodplain areas, that must be kept free of encroachment so that <br />the lOO-year flood can be carried without substantial increases in <br />flood heights. Minimum Federal standards limit such increases to <br />1.0 foot, provided that hazardous velocities are not produced. The <br />floodways in this study are presented to local agencies as minimum <br /> <br />13 <br />