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Water-surface elevations of the .10- and 100-year floods were computed using the U,S, Army Corps of Engineers HEC-2 step-backwater computer program (Reference 9), The starting water-surface elevation was derived from hand computations for the peak flow at Pecos Street, The computation derived rating curves for pressure and weir flow at Pecos Street crossing. The culverts at Holiday Glen and Holiday Circle were included in the HEC-2 models, However, three long culverts that have limited capacity to fully contain the 10- and 100-year peak flows were not included, These culverts extend from the east branch of Holiday Circle to 100 feet downstream of Holiday Vale; from the east branch of Holiday Terrace downstream 200 feet; and from Holiday Parkway downstream 200 feet, The culvert under Holiday Parkway is submerged due to backwater from Pecos Street for the 10- and 100-year floods, An approximate flood plain analysis was carried out for Niver Creek and Tributary L of Niver Creek using assumed depths based on a review of the Tributary M profile and available hydrologic information, extensive field reQonnaissance, and engineering judgment, All elevations are referenced to the National Geodetic Vertical Datum of 1929 (NGVD). Elevation reference marks used in this study are shown on the maps, 4,0 FLOOD PLAIN J1,M~f\G~N!..gP~~.~TIONS The NFIP encourages State and local governments to adopt sound flood plain management programs, Therefore, each Flood Insurance Study prOduces maps designed to assist communities in developing flood plain management measures, 4,1 Flood Boundaries To provide a national standard without regional discrimination, the 1 percent annual chance (lOp-year) flood has been adopted by FEMA as the base flood for flood plain management purposes. For each stream studied in detail, ~he 100-year flood plain boundaries have been delineated using the tlood elevations determined at each cross section, Between cross s~ctions, the boundaries were inter- polated using topographic maps at a scale of 1:1,200, with a contour interval of 2 feet (Reference 8), As a result of the scope of work for this study, no SOO-year flood boundaries were delineated, Small areas within the flood plain boundaries may lie above the flood elevations, but cannot be: shown due to limitations of the map scale and/or lack of detail~d toj?ographic data., 8