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<br />4.1 Floodplain Boundaries <br /> <br />To provide a national standard without regional discrimination, the <br />I percent annual chance (lOa-year) flood has been adopted by FEMA <br />as the base flood for floodplain management purposes. The 0.2 <br />percent annual chance (SOO-year) flood is employed to indicate <br />additional areas of flood dsk in the community. For each stream <br />studied by detailed methods, the 100- and SOO-year floodplain <br />boundaries have been delineated using the flood elevations <br />determined at each cross section. Between cross sections, the <br />boundaries were interpolated using topographic maps at a scale of <br />1:2,400, with a contour interval of 2 feet (References 12 and 13). <br /> <br />The 100- and SOO-year floodplain boundaries are shown on the Flood <br />Insurance Rate Map. On this map, the lOa-year floodplain boundary <br />corresponds to the boundary of the areas of special flood hazards <br />(Zones A and AE); and the SOO-year floodplain boundary corresponds <br />to the boundary of areas of moderate flood hazards. In cases where <br />the 100- and SOO-year floodplain boundaries are close together, <br />only the lOa-year floodplain boundary has been shown. Small areas <br />within the floodplain boundaries may lie above the flood elevations <br />but cannot be shown due to limitations of the map scale and/or lack <br />of detailed topographic data. <br /> <br />4.2 Floodways <br /> <br />Encroachment on floodplains, such as structures and fi 11, reduces <br />flood-carrying capacity, increases flood heights and velocities, <br />and increases flood hazards in areas beyond the encroachment <br />itself. For purposes of the NFIP, a floodway is used as a tool to <br />assist local communities in this aspect of floodplain managemen~. <br />Under this concept, the area of the lOa-year floodplain is divided <br />into a floodway and a floodway fringe. The floodway is the channel <br />of a stream, plus any adjacent floodplain areas, that must be kept <br />free of encroachment so that the lOO-year flood can be carried <br />without substantial increases in flood heights. <br /> <br />No floodways were computed for flooding SOurceS studied by detailed <br />methods in the Town of Wellington due to nonexistence of a defined <br />channel along portions of the study reaches. <br /> <br />5.0 INSURANCE APPLICATION <br /> <br />For flood insurance rating purposes, flood <br />are assigned to a community based on the <br />analyses. These zones are as follows: <br /> <br />insurance zone designations <br />results of the engineering <br /> <br />Zone A <br /> <br />Zone A is the flood <br />IOO-year floodplains <br />Study by approximate <br /> <br />insurance <br />that are <br />methods. <br /> <br />rate zone that corresponds to the <br />determined in the Flood Insurance <br />Because detailed hydraulic analyses <br /> <br />8 <br />