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1 1 1 1 1 1 1 1 1 1 I 1 I 1 1 1 1 1 'I The discharge hydrograph for Kelly Road Dam provided by the USCOE represented flow from the service spillway and flows over the west embankment. Flows from the west end and the associated floodplain were provided by the Urban Drainage and Flood Control District. This overflow was generally in a northeasterly HYDRAULIC INFORMATION GENERAL The hydraulic analysis of the Westerly Creek channel between Kelly Road Dam and Stapleton International Airport was performed using the U.S. Army Corps of direction and was entirely in the main channel at Colfax Avenue. The flood discharges at several locations within the study area are tabulated in the following table. They reflect total flow at each street (main channel and flow from west end not yet in main channel) and the flow in the main channel area. Engineers HEC-2 Water Surface Profiles computer program. The analysis was performed to determine the water surface profiles for the 100-year and 10-year storm events. The cross sections were derived from the CDM FHAD study with constructed or TABLE 2 FLOOD DISCHARGE proposed improvements inserted. Additional sections, where required, were developed from 1"=100' scale, 2-foot contour interval topographic mapping provided. ToW Main Channel Location 100- Year-Flow 100-Year-Flow (cfs) (cfs) Kelly Rood Dam at 11th 2769 1200 13th Avenue 280S 227S Colfax Avenue 2787 2787 17th Avenue 3559 3559 19th Avenue 3542 3542 Montview Boulevard 5441 5441 23rd Avenue 5648 5648 Stapleton International Airport 5796 5796 Field investigations were conducted to supplement previously determined channel conditions. CHANNEL DESCRIPTION The historic drainage channel in this study reach was described by CDM as follows: The natural Westerly Creek channel between 11th Avenue and Stapleton International Airport has been almost completely obliterated by develop- ment and encroachment so that there is little or no floodplain remaining. The main channel of Westerly Creek is a combination of open channel and drainage structures of mixed construction, with little or no capacity to receive even local tributary flows. In addition, many reaches of the creek have not been maintained, and the open channel sections are covered with brushes and lowland vegetations. Westerly Creek within this reach has capacity for less than a I-year frequency storm event. 6