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<br />\ <br /> <br />"' <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 />100-year flood more than 1.0 foot at any point. Typical relation- <br />ships between the flood\vay and the floodway fringe and their signif- <br />icance to flood plain development are shown in Figure 3. <br /> <br />J <br /> <br />I" <br /> <br />100-YEAR FLOOD PLAIN <br /> <br />.1 <br /> <br /> <br />FLOODWAY <br />FRINGE <br /> <br /> <br />FLOODWAY <br /> <br />FLOODWAY <br />FRINGE <br /> <br />STREAM <br />CHANNEL <br /> <br /> <br />FLOOD ELEVATION WHEN <br />CONFINED WITHIN FLOODWAY <br /> <br />'NCR~M'NT ~~ <br /> <br /> <br />f-~- <br /> <br /> <br />..-L <br />AREA OF FLOOD PLAIN THAT COULD <br />BE USED FOR DEVELOPMENT BY <br />RAISING GROUND <br /> <br />ENCROACHMENT <br />r- <br /> <br /> <br />rI <br /> <br /> <br />, <br />FLOOD ELEVATION <br />BEFORE ENCROACHMENT <br />ON FLOOD PLAIN <br /> <br />LINE AB IS THE FLOOD ELEVATION BEFORE ENCf~OACHMENT. <br />LINE CD IS THE FLOOD ELEVATION AFTER ENCROACHMENT, <br />'SURCHARGE IS NOT TO EXCEED 1.0 FOOT (FIA REQUIREMENT) OR LESSER AMOUNT IF SPECIFIED BY STATE. <br /> <br />Figure 3. Floodway Schematic <br /> <br />5.0 INSURANCE APPLICATION <br /> <br />In order to establish actuarial insurance raies, the Federal Insurance <br />Administration has developed a process to transform the data from the <br />engineering study into flood insurance criteria. This process includes <br />the determination of reaches, Flood Hazard Factors, and flood insurance <br />zone designations for each flooding source studied in detail affecting <br />the unincorporated areas of Garfield County. <br /> <br />-; <br /> <br />S.l Reach Determinations <br /> <br />Reaches are defined as lengths of watercourses having relatively <br />the same flood hazard, based on the average weighted difference in <br />water-surface elevations between the lO- and lOQ-year floods. This <br />difference does not have a variation greater than that indicated in <br />the following table for more than 20 percent of the reach. <br /> <br />18 <br />