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<br />encomoasses the oortion of the floo~ plain that could he comoletelv <br />obstructed without increasing the water-surface elevation of the <br />100-year flood more than 1.0 foot at anv point. Tyoical relation- <br />ships between the floodway and the floodway fringe and their signi- <br />ficance to flood plain development are shown in Figure 3. <br /> <br />I~ <br /> <br />1 aD-YEAR FLOOD PLAIN <br /> <br />-, <br /> <br />F LOODWA Y <br />FRINGE <br /> <br /> <br />FLQODWAY <br /> <br />FLQODWAY <br />FRINGE <br /> <br />STREAM <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 />BEFORE ENCROACHMENT <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 NOT TO EXCEeD 1.0 FOOT (FIA AEQUIREMENT) OR LESSER AMOUNT I F SPECIFIED BY STATE, <br /> <br />Figure 3. Floodway Schematic <br /> <br />5.0 INSURANCE APPLICATION <br /> <br />In order to establish actuarial insurance rates, the Federal Insurance <br />Administration has developed a process to transform the data from the <br />engineering study into floo~ 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 />Naturita. <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- o.nd 100-vear floods. <br />This difference does not have a variation greater than that indi- <br />cated in the following tahle for more than 20 percent of the reach: <br /> <br />11 <br />