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At Lipan Street along Sanderson Gulch, flows escape along the left overbank and extend to the South Platte River as shallow flooding. These shallow flooding areas were determined using normal-depth calculations. A portion of flooding on Sanderson Gulch from South Sheridan Boulevard (State Highway 95) downstream to cross section BQ has been labeled with a Profile, Base Line. Flooding backs up at the culvert under South Sheridan Boulevard and flows over the road at a low spot just.north of the culvert. Weir Gulch Cross section data for Weir Gulch were obtained from construction drawings (References 26-30), field surveys, and topographic mapping (Reference 56). The starting water-surface elevations were obtained assuming a simultaneous 10-year 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 water- surface elevations were taken from the Preliminary Flood Insurance Study 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 100-year discharge under pressure flow. :-lanning's "n" values ranged from 0.014 to 0.035 for this reach (Reference 31). First Avenue Tributarv and Dakota Avenue Tributary Cross section data, ~anning I s "n" values, and stat"ting ",.;atec- surface elevations were obtained from the 1977 UDFeD ?locd ::aza:-ci ALea Delineation report for the ~eir Gulch tribucari2s (Reference 20). Cross section data were compiled :~om "":opcg:'aFhir.; ~aps (Reference 58). Starting water-surface elev8cions ~ere determined ':Jy the Weir Gulch water-surface profiles. The ~anning l::i "n" val'J.es were 0.080 :01" :::.e -::-.anne~ and o'....eroanks on Jakot.:1 Avenue Tributary and ranged from 0.025 ~o 0.080 :or :he cha~nel 3P-C 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 lieir 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 24