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<br />Between cross sections, <br />U. S. Geological Survey <br />1: 24,000 with a contour <br />graphs at an approximate <br /> <br />the boundaries were interpolated using <br />(USGS) topographic maps at a scale of <br />interval of 10 feet, and aerial photo- <br />scale of 1:24,000 (References 2 and 3). <br /> <br />The 100-year floodplain boundary is shown on the FIRM (Exhi hi t <br />2). On the FIRM, the 100-year floodplain boundary corresponds to <br />the boundary of the areas of special flood hazards (Zones A and <br />AE). Small areas within the floodplain boundaries may lie above <br />the flood elevations but cannot be shown due to limitations of <br />the map scale and/or lack of detailed topographic data. <br /> <br />4.2 Floodways <br /> <br />Encroachment on floodplains, such as structures and fill, reduces <br />flood-carrying capacity, increases flood heights and velocities, <br />and increases flood hazards in areas beyond the encroachment. <br />One aspect of floodplain management involves balancing the <br />economic gain from floodplain development against the resulting <br />increase in flood hazard. For purposes of the NFIP, a f100dway <br />is used as a tool to assist local communities in this aspect of <br />floodplain management. Under this concept, the area of the 100- <br />year floodplain is divided into a floodway and a floodway fringe. <br />The floodway is the channel of a stream, plus any adjacent <br />floodplain areas that must be kept free of encroachment so that <br />the IOO-year flood can be carried wi thout substant ial increases <br />in flood heights. Minimum federal standards limit such increases <br />to 1.0 foot, provided that hazardous velocities are not produced. <br />For this Flood Insurance Study, floodways were not computed. <br /> <br />5.0 INSURANCE APPLICATION <br /> <br />For flood insurance rating purposes, flood insurance zone designations <br />are assigned to a communi ty based on the resul ts of the engineering <br />analyses. These zones are as follows: <br /> <br />Zone A <br /> <br />Zone A is the flood insurance rate zone that corresponds to the <br />100-year floodplains that are determined in the Flood Insurance <br />Study by approximate methods. Because detailed hydraulic <br />analyses are not performed for such areas, no base flood <br />elevations (BFEs) or depths are shown within this zone. <br /> <br />Zone AE <br /> <br />Zone AE is the flood insurance rate zone that corresponds to the <br />100-year floodplains that are determined in the Flood Insurance <br />Study by detailed methods. In most instances, whole-foot BFEs <br />derived from the detailed hydraulic analyses are shown at <br />selected intervals within this zone. <br /> <br />6 <br />