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<br />The area between the floodway and the boundary of the lOa-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 />lOa-year flood more than 1.0 foot at any point. Typical relation- <br />ships between the floodway and the floodway fringe and their signif- <br />icance to flood plain development are shown in Figure 7. <br /> <br />I ( <br /> <br />100-VEAR FLOOD PLAIN <br /> <br />-, <br /> <br />FLOODWAY <br />FRINGE <br /> <br /> <br />FLOODWAY <br /> <br />FLOOOWAY <br />FRINGE <br /> <br />STAEAM <br />CHANNEL <br /> <br />FLOOD ELEVATiON WHEN <br />CONFINED WITHIN FlOODWAY <br /> <br /> <br />AREA OF FLOOD PLAIN THAT COULD <br />BE USED FOR DEVELOPMENT BY <br />RAISING GROUND <br /> <br />FLOOD ELEVATION <br />BEFOAEENCROACHMENT <br />ON FLOOD PLAIN <br /> <br />LINE AS IS THE FLOOD ELEVATION BEFORE ENCROACHMENT. <br />LINE CD IS THE FLOOD ELEVATION AFTER ENCROACHMENT. <br />.SURCHARGE IS NOTTO EXCEED 1.0 FOOT (FEMA REQUIREMENT) OR LESSER AMOUNT IF SPECIFIED BY STATE. <br /> <br />, <br /> <br />Figure 7. Floodway Schematic <br /> <br />5.0 INSURANCE APPLICATION <br /> <br />In order to establish actuarial insurance rates, the Federal Emergency <br />Management Agency has developed a process to transform the data from <br />the engineering study into flood insurance criteria. This process includes <br />the determination of reaches, Flood Hazard Factors (FHFs), and flood <br />insurance zone designations for each flooding source studied in detail <br />affecting Grand Junction. <br /> <br />5.1 Reach Determinations <br /> <br />Reaches are defined as lengths of watercourses having relatively <br />the same flood hazard, based on the average weighted difference <br />in water-surface elevations between the 10- and lOa-year floods. <br /> <br />22 <br />