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<br />.. <br /> <br />itself. One aspect of flood plain management involves balancing <br />the economic gain from flood plain development against the result- <br />ing increase in flood hazard. For purposes of the National Flood <br />Insurance Program, the concept of a floodway is used as a tool <br />to assist local communities in this aspect of flood plain manage- <br />ment. Under this concept, the area of the 100-year flood is <br />divided into a floodway and a floodway fringe. The floodway <br />is the channel of a stream plus any adjacent flood plain areas <br />that must be kept free of encroachment in order that the 100-year <br />flood may be carried without substantial increases in flood heights. <br />Minimum standards of the Federal Emergency Management Agency <br />limit such increases in flood heights to 1.0 foot, provided that <br />hazardous velocities are not produced, The floodways in this <br />report are presented to local agencies as minimum standards that <br />can be adopted or that can be used as a basis for additional <br />studies. <br /> <br />, <br /> <br />. <br /> <br />\ <br /> <br />Due to high velocities, the floodway is equal to the 100-year <br />floodplain, except for small areas of non-conveyance. <br /> <br />The results of these computations were tabulated at selected <br />cross sections for each stream segment for which a floodway was <br />computed (Table 2). <br /> <br />AS shown on the Flood Boundary and Floodway Map (Exhibit 2). <br />the floodway widths were determined at cross sections; between <br />cross sections, the boundaries were interpolated. In cases where <br />the boundaries of the floodway and the 100-year flood are either <br />close together or collinear, only the floodway boundary has been <br />shown. <br /> <br />c <br /> <br />The area between the floodway and the boundary of the 100-year <br />flood is termed the floodway fringe. The floodway fringe thus <br />encompasses the portion of the flood plain that could be completely <br />obstructed without increasing the water-surface elevation of <br />the 100-year flood more than 1.0 foot at any point. Typical <br />relationships between the floodway and the floodway fringe and <br />their significance to flood plain development are shown in Figure 6. <br /> <br />> <br /> <br />, <br /> <br />, <br /> <br />w <br /> <br />11 <br />