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<br />aspect of flood plain management. Under this concept, the area of <br />the 100-year flood is divided into a floodway and a floodway fringe. <br />The floodway is the channel of a stream, plus any adjacent flood <br />plain areas that: must be kept free of encroachment in order that the <br />100-year flood be carried without substantial increases in flood <br />heights. As minimum standards, the Federal Insurance Administration <br />limits such increases in flood heights to l.0 foot, provided that <br />hazardous velocities are not produced. <br /> <br />A floodway is generally not appropriate in areas such as those that <br />may be inundated by floodwaters from rivers located in extremely <br />flat terrain. A floodway is not applicable for Dragon Wash since <br />the 100-year flood is confined to the stream channel. <br /> <br />The floodway designated for this study was computed on the basis of <br />equal conveyance reduction from each side of the White River flood <br />plain, except where such equal reduction would be prevented by high <br />bluffs. Under no circumstance was the floodway encroached into the <br />stream channel. Floodway boundaries were determined at cross sec- <br />tions used in the analysis; between cross sections, the boundaries <br />were interpolated. The results of floodway computations are contained <br />in Table 1. <br /> <br />The floodway determined for the White River is located outside the <br />corporate limits, except in the northeastern corner of Rangely. <br />However, all of the cross sections are located outside the corporate <br />limits; therefore, no cross sections are shown on the Flood Boundary <br />Map (Exhibit 2) and the Floodway Map (Exhibit 3). <br /> <br />The area between the floodway and the boundary of the 100-year flood <br />is termed the floodway fringe. The floodway fringe thus encompasses <br />the portion of the flood plain that could be completely obstructed. <br />without increasing the water-surface elevation of the 100-year flood <br />more than 1.0 foot at any point. Typical relationships between the <br />floodway and the floodway fringe and their significance to flood <br />plain development are shown in Figure 3. <br /> <br />. <br /> <br />" <br /> <br />13 <br />