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I I I I I I I I I I I I I I I I I I I Shallow flooding or sheet flow areas along Cressmans Gulch are designated to illustrate the following conditions and problem areas. 1. Overtopping of Pine Ridge Roads causes floodwaters to become hydraul- ically disconnected from channel flows. The shallow flooding area represents an approximate area of inundation through which flood waters will return to the channel (Sheets 2 and 3). 2. The existing Highway #93 crossing of Cressmans Gulch has a maximum capacity of about 90 cfs before road grade overtopping occurs. One- hundred year flows will overtop the low point in the road grade weir by 1 to 1.5 feet. Some flows escaping the main channel will be carried down the west ditch of Highway #93 to Tucker Gulch. Flows crossing Highway #93 will be carried by the existing channel and will sheet flow across the open area east of Highway #93, and west of North Ford Street. Low lying properties in the northeast corner of the existing residential area will be subject to flood damages as a result of the limited capacity of the highway culvert (Sheet 4). 3. The existing capacity of the relocated channel is about 100 cfs before overtopping of the abandoned railroad grade occurs, causing excess flows to return to the historic channel. Overflow areas along the railroad grade are shown on Sheets 4 and 6. This condition does not present any major problem at this time since no development exists in thi s area. Kenneys Run: The study reach for the main stem of Kenneys Run begins at its confluence with Clear Creek (Cross section No. 100) and ends where the East Fork and West Fork join near 20th Street. Cross section No. 109 is located immediately downstream of the twin fork confluence. Floodplain limits and water surface profiles for this reach are shown on Sheets 8 and 9. Subdivision, located west of Ford Street, and industrial development upstream (west) of Highway #93. The drainageway alignment traverses the Adolph Coors property west of the main brewery buildings and facilities. The majority of the study reach is storm sewered with Jackson and Ford Streets being the major overflow areas. The storm sewer includes a 96-inch pipe adjacent to Jackson Street and a combined elliptical pipe and 8-foot x ll-foot concrete fl ume through the Coors property. A short reach of open channel exists for a distance of 100 feet immediately downstream of 15th Street. Development along Kenneys Run consists of Coors offices, school property, banks, churches, gas stations, Safeway Store, office buildings and other commercial establishments, and residential structures. A significant flood damage potential exists for this study reach. Separate water surface profiles were calculated for the relocated and historic channels of Cressmans Gulch. Flow splitting assumptions were based on the hydraulic condition of the Highway #93 crossing and the estimated capacity of the relocated channel east of the abandoned railroad grade. Data regarding the split flow analysis is presented in Table V, "Floodplain and Floodway Reference Data". The following is a description of flooding characteristics of certain problem areas along the main stem of Kenneys Run. 1. Flood elevations and corresponding flood protection levels at the Clear Creek confluence vary across the width of the floodplain. For the floodplain area north of 12th Street, including Ford Street and the adjacent areas between Cross Section Nos. 100 and 101, the minimum flood protection levels will be controlled by flood elevations along Clear Creek. This area includes the Mitchell School property and the area between Ford Street and the Coors Wellness Center. Flood levels east of the Wellness Center will be controlled by Kenneys Run flooding. For the floodplain area between 12th and 13th Streets, minimum flood protection levels should be based on the Kenneys Run flood profile (Sheet 8). 19