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<br />\- <br /> <br />'100.YEAR FLO'OD PLAIN <br /> <br />)1 <br /> <br />FLOODWAV <br />FRINGE <br /> <br /> <br />FLOODWAY <br /> <br />FLOODWAV <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 /> <br />o <br /> <br />SURCHARGE. <br />--- <br /> <br />FLOOD ELEVATION <br />BEFOREENCAOACHMENT <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 ISNOTTOEXCEED 1.0 FOOT (FEMA REQUIREMENT) OR LESSER AMOUNT IF SPECIFIED BY STATE. <br /> <br />Figure 10. Floodway Schematic <br /> <br />5.0 INSURANCE APPLICATION <br /> <br />To establish actuarial insurance rates, data from the engineering study <br />must be transformed 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 PMA of the City of Longmont. <br /> <br />5.1 Reach Determinations <br /> <br />Reaches are defined as section~ of flood plain that have relatively <br />the same flood hazard. In riverine areas, reaches are based on <br />the average weighted difference in water-surface elevations between <br />the 10- and 100-year floods. This difference may not have a varia- <br />tion greater than that indicated in the following table for more <br />than 20 percent of the reach: <br /> <br />Average Difference Between <br />10- and 100-Year Floods <br /> <br />variation <br /> <br />Less than 2 feet <br />2 to 7 feet <br />7.1 to 12 feet <br />More than 12 feet <br /> <br />0.5 foot <br />1. 0 foot <br />2.0 feet <br />3.0 feet <br /> <br />20 <br />