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<br />area of the 100-year flood is divided into a floodway and a floodway <br />fringe. The floodway is the channel of a stream, plus any adjacent <br />flood plain areas, that must be kept free of encroachment in order <br />that the lOO-year flood be carried without substantial increases in <br />flood heights. As minimum standards, the Federal Insurance Admini- <br />stration limits such increases in flood heights to 1.0 foot, provided <br />that hazardous velocities are not produced. <br /> <br />The floodways for this study were computed on the basis of equal <br />conveyance reduction from each side of the flood plain or encroach- <br />ment to the streambanks. The results of these computations are <br />tabulated at selected cross sections for each stream segment for <br />which a flood way is computed (Table 2). <br /> <br />As shown on the Flood Boundary and Floodway Map (Exhibit 2), the <br />floodway boundaries were determined at cross sections; between <br />cross sections, the boundaries were interpolated. In cases where <br />the floodway and 100-year flood boundaries are close together, only <br />the floodway boundary has been shown. <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 the <br />IOO-year flood more than 1.0 foot at any point. Typical relation- <br />ships between the floodway and the floodway fringe and their signifi- <br />cance to flood plain development are shown in Figure 2. <br /> <br />10 <br />