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<br />Between cross sections, the boundaries for Beaver Creek were <br />interpolated using simple survey methods from the established <br />markers or by scaling from physical features shown on the map. <br /> <br />The floodplain boundaries for the South Platte River were also <br />interpolated by survey methods. USGS 7.S Minute Quadrangle Maps <br />were also used in this interpolation. <br /> <br />Appropriate areas were plotted <br />Maps (FHBMs) (Reference 9) <br />(Reference 10). <br /> <br />using existing Flood Hazard Boundary <br />and Flood Prone Quadrangle Maps <br /> <br />The 100- and SOO- year floodplain boundaries are shown on the Flood <br />Insurance Rate Map (Exhibit 2). On this map, the lOO-year <br />floodplain boundary corresponds to the boundary of the areas of <br />special flood hazards (Zones A and AE), and the SOO-year floodplain <br />boundary corresponds to the boundary of areas of moderate flood <br />hazards. In cases where the 100- and SOO-year floodplain <br />boundaries are close-together, only the lOO-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 lOO-year <br />shown on the Flood Insurance Rate Map <br /> <br />4.2 Floodways <br /> <br />Encroachment on floodplains, such as structures and fill, reduces <br />flOOd-carrying capacity, ir.creases flood heights and velocities, <br />and increases flood hazards in areas beyond the encroachment. One <br />aspect of floodplain management involves balancing the economic <br />gain from floodplain development against the resulting increases in <br />flood hazard. For purposes of the NFIP, a floodway is used as a <br />tool to assist local communities in this aspect of floodplain <br />management. Under thi s concept, the area of the 100-year <br />floodplain is divided into a floodway and a floodway fringe. The <br />floodway is the channel of a stream, plus any adjacent floodplain <br />areas that must be kept free of encroachment so that the 100-year <br />flood can be carried without the substantial increases in flood <br />heights. Minimum federal standards limit such increases to 1.0 <br />feet, provided that hazardous velocities are not produced. <br /> <br />For this Flood Insurance Study, floodways were not computed. <br /> <br />l2 <br />