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The hydrologic analysis for Bear Creek was performed by the COE, Omaha District (Reference 2). ~he Bear Creek Dam and Reservoir intercepts flows from 239 square miles of the total 261 square mile drainage basin. The remai~ing square mile drainage area below Bear Creek Dam still has the potential of generating damaging runoff flows during a cloudburst event over the lower basin. No applicable runoff records are available through this reach because of the recent construction of the dam. Therefore, discharges for the 22 square mile drainage' area below the dam were developed by using the U.S. Environmentall Protection Agency Storm Water Management Model (Reference 4) with modifications by the Missouri River Division of the COE. The$e discharges were computed assuming full basin development. ' , Peak discharge-drainage area relationships for Bear Creek are shown in Table 1. 3.2 Hydraulic Analyses Analyses of the hydraulic charapteristics of flooding from the sources studied were carried out to provide estimates of the eleva- tions of floods of the selected! recurrence intervals. Water-surface elevation~ of flopds,of the selected recurrence intervals were computed through: the use of the COE HEC-2 step- backwater computer program (Reference 5). CrolOs section data, Manning's Or" values, and starting water-surface elevations were developed for use in the 1979 Urban Drainage and Flood Control District Flood Area Delineation report for Bear Creek (Reference 6). Cross section data were obtained photogram- metrically by digitizing cross 'sections marked on aerial photographs of the stream channel and flood' plain (Reference 7). The digitized , , , cross section data were supplemented with cross sections taken from topographic mapping (Reference 8) developed from the aerial photography. All bridge cross ~ections were obtained from actual field measurements. Roughnessboefficients for the channel and overbank areas were elOtimated b,Y field inspection of the study area. Manning's On" values wer~ 0.035 in the channel and from 0.025 to 0.090 in the overbank areas. , I Additional cross sections were ,included from channel improvement plans due to recent grading and channel improvements in the vicinity of South Lowell Boulevard. Shallow flooding along the soutp bank of Bear Creek is the result of side spill from the main cha~nel. This side spill occurs from the east edge of, South Fede,ral ~oulevard downstream to South Clay Street. Approximately 2,000 q~s of the 100-year discharge of 8,150 cfs spills into this sha1low flow area and attains a water- surface elevation below that o~ the main channel. These flows 6