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Starting water-surface elevations for Gore Creek were taken from a Flood Plain Information report (Reference 4). Using this report, the SO- and SOO-year flood elevations were extrapolated from the lO- and lOO-year flood elevations. The starting water-surf_c~ elevations for all the other creeks were taken from their confluences with Gore Creek. Shallow flooding areas were analyzed using normal- depth calculations and topographic maps at a scale of l:2400, with contour intervals of 2, lO, and 20 feet (Reference 6). All elevations are referenced to the National Geodetic Vertical Datum of 1929 (NGVD). Elevation reference marks used in the study are shown on the maps. The hydraulic analyses for this study were based on unobstructed flow. The flood elevations shown on the profiles are, thus, considered valid only if hydraulic structures remain unobstructed, operate properly, and do not fail. 4.0 FLOOD PLAIN MANAGEMENT APPLICATIONS The National Flood Insurance Program encourages State and local governments to adopt sound flood plain management programs. Therefore, each Flood Insurance Study includes a flood boundary map designed to assist com- munities in developing sound flood plain management measures. 4.l Flood Boundaries In order to provide a national standard without regional discrimina- tion, the lOO-year flood has been adopted by the Federal Emergency Management Agency as the base flood for purposes of flood plain management measures. The SOO-year flood is employed to indicate additional areas of flood risk in the community. For each stream studied in detail, the boundaries of the lOO- and SOO-year floods have been delineated using the flood elevations determined at each cross section; between cross sections, the boundaries were interpolated using topographic maps at a scale of l:2400, with contour intervals of 2, lO, and 20 feet (Reference 6). Boundaries of the shallow flooding areas were delineated, using field inspection and engineering judgment, on topographic maps at a scale of l:2400, with contour intervals of 2, lO, and 20 feet (Reference 6). Flood boundaries for the 100- and SOO-year floods are shown on the Flood Boundary and Floodway Map (Exhibit 2). In cases where the lOO- and 500-year flood boundaries are close together, only the lOO-year flood boundary has been shown. Small areas within the flood boundaries may lie above the flood elevations and, there- fore, not be subject to flOOding; owing to limitations of the map scale and/or lack of detailed topographic data, such areas are not shown. II