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Weir Gulch Cross-section data for Weir Gulch were obtained from construction drawings (References 26-30), field surveys, and topographic mapping (Reference 57). The starting WSELs were obtained assuming a simultaneous 10-percent-annual-chance runoff event on the South Platte River. Roughness coefficients were determined by field inspection on the channel and overbank areas, and ranged from 0.013 to 0.050... and from 0.013 to 0.055, respectively. For the channel improvements along Weir Gulch which extend from West Alameda Avenue to Sheridan Boulevard, cross-sectional data for the hydraulic analysis were taken from information prepared for the Weir Gulch project (Reference 31). Supplemental field observations and design information were used where needed. The starting WSELs were taken from the Preliminary FIS for the City and County of Denver, dated September 27,1988. All of the bridges and box culverts within this reach were modeled using the HEC-2 special bridge routine in order to check for pressure flow at these structures. All of these structures convey the I-percent-annual-chance discharge under pressure flow. Manning's "n" values ranged from 0.014 to 0.035 for this reach (Reference 31). First Avenue Tributary and Dakota Avenue Tributary Cross-section data, Manning's "n" values, and starting water- surface elevations were obtained from the 1977 UDFCD Flood hazard Area Delineation report for the Weir Gulch tributaries (Reference 20). Cross-section data were compiled from topographic maps (Reference 58). Starting WSELs were determined by the Weir Gulch water-surface profiles. The Manning's "n" values were 0.080 for the channel and overbanks on Dakota Avenue Tributary and ranged from 0.025 to 0.080 for the channel and overbanks on First Avenue Tributary. For the drainage improvements along the Dakota Avenue Tributary, cross sectional data for the hydraulic analysis were taken from information prepared for the Weir Gulch Dakota Avenue Tributary project. Supplemental field observations and design information were used where needed. Improvements included a concrete culvert system which was designed taking into account manhole, bend, and exit losses. It was determined that the hydraulic grade line remains within the system and that the 1-percent-annual-chance flood is conveyed by the system. The Manning's "n" value used was 0.014 for this study reach (Reference 32). Sand Creek Cross-section data, Manning's "n" values, and starting water- surface elevations were obtained from the 1977 UDFCD Flood Hazard Area Delineation report for Sand Creek (Reference 42). Cross-section data were compiled from topographic maps (Reference 59). Manning's "n" values ranged from 0.036 to 0.044 in the channel and from 0.035 to 0.100 in the overbank areas. Backwater computations for 23