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The floodways presented in this study were computed on the basis of equal conveyance reduction from each side of the flood plain. The results of these computations were tabul ated at sel ected cross sections for each stream segment for which a floodway was computed (Table 2). As shown on the Flood Boundary and Floodway Map, the fl oodway boundaries were determined at cross sections; between cross sections the boundaries were interpolated, In cases where the floodway and IOO-year flood boundaries are close together or col inear, only the fl oodway boundary has been shown. The area between the floodway and the boundary of the 100-year fl ood is termed the fl oodway fri nge. The fl oodway fri nge thus encanpasses the portion of the flood plain that could be cOOlpletely obstructed without increasing the water-surface elevation of the 100-year flood more than 1.0 feet at any point, Typical rel ationships between the fl oOdway and the fl oodway fringe and their significance to flood plain development are shown in Figure 2. I- 1 OO"YEAA FLOOD PLAIN -, FLOODWAY FRINGE FLOODWAY FLOOOWAY FRINGE STREAM CHANNEL FLOOD ELEVATION WHEN CONFINED WITHIN FLQOOWAY AREA OF FLOOD PLAIN THAT COULD BE USED FOR DEVELOPMENT BY RAISING GROUND FLOOD ELEVATION BEFOAEENCAOACHMENT ON FLOOD PLAIN LINE AB IS THE FLOOD ELEVATION BEFORE ENCROACHMENT. LINE CD IS THE FLOOD ELEVATION AFTER ENCROACHMENT. 'SURCHARGE IS NOT TO ExceeD 1.0 FOOT (FIA REQUIREMENT) OR LESSER AMOUNT IF SPECIFIED BY STATE. Fi gure 2 FLOOOWAY SCHEMATIC 5.0 INSURANCE APPLICATION In order to establish actuarial insurance rates, FIA has developed a process to transform the data frOOl the engineering study into flood insurance criteria. This process includes the determination of reaches, 10