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. . . . . . . I I I . . . . I '. . I 'I deliver water to the Moffat Treatment Plant and have the capability of forcing the natural inflow back into Ralston Creek. Although Ralston Reservoir is not oper- ated for flood control purposes, there is approximately 2,400 acre-feet of storage available between the pri- mary spillway crest at e18vation 6046.0 feet m.s.l. and the top of the dam at elevation 6060.0 feet m.s.l. which provides incidental flood control. Flood fighting and emergency evacuation plans are also factors which can reduce the flood hazard. No formal plans for flood fight- ing or emergency evacuation of people and personal property from floodplain areas are known to have been prepared for Clear Creek. However, during times of flooding, agencies such as the local police, the sheriff's office, the State Highway Patrol, and road maintenance crews assist in flood fighting and evacuating people from flooded areas. The most effective means to reduce flood hazards is to be aware of such hazards and to avoid them. Implementing floodplain regulation practices will keep improvements out of the floodplain and out of danger. Flood proofing will tend to reduce damage to the existing buildings and structures within the floodplain. 2. Maple Grove Reservoir. Maple Grove Reservoir is located on Lena Gulch at West 27th Avenue, Lakewood, Colorado. It is owned by Consolidated Mutual Water Company and is used for municipal water supply storage. The reservoir provides some attenuation of flood peaks. Approximately 452 acre-feet of storage are available between the crest of the inlet at elevation 5520.0 feet m.s.l. and the top of the fabridam at elevation 5531.0 feet m.s.l. - FLOOD RELATED STUDIES - 3. Leyden Lake. Leyden Lake is an irrigation water storage reservoir on Leyden Creek upstream from Indiana Street. There are approximately 550 acre-feet of uncontrolled storage between the spillway crest at 5612.0 feet m.s.l. and the crest of the dam at elevation 5620.0 feet m.s.l. There have been two previous floodplain studies of Clear Creek. In 1966, the U.S. Army Corps of Engineers published a Flood Plain Information Report for Clear Creek (Reference 3). In 1976, Gingery Associates, Inc., produced the Adams County Flood Insurance Study for the Federal Insurance Administration (Reference 2). The flood profiles presented in this study differ from those previously published due to revised flood discharges and the availability of more detailed topographic mapping. Along portions of the length of Clear Creek, levees have been constructed as a flood protection measure. Hydraulic analyses indicate that the levees will be effective in containing the 100- year flood on the south side of Clear Creek east of Sheridan and on both sides of Clear Creek between Youngfield Street and the Coors Complex. The National Oceanic and Atmospheric Administration (NOAA) maintains year-round surveillance of weather and flood conditions in the study area. Although intense cloudburst activity in the general region can be forecast, such storms and resultant flooding in specific small drainage areas cannot be predicted accurately, and in any event, forecasts would provide very little advance warning. - HYDROLOGIC AND HYDRAULIC DETERMINATIONS - Hydrologic Analysis The flood discharges used in this report were computed and supplied by the Omaha District of the Corps of Engineers. Peak diSCharge-frequency relationships were established for floods of 10-, 50-, 100-, and 500-year recurrence intervals and are based upon future development conditions projected for the basin. Discharge records for the Clear Creek stream gages at Golden and Derby were analyzed using methods presented in Bulletin No. 17 published by the Water Resources Council (Reference 5). The results of these analyses were used to calibrate the MITCAT (Reference 6) -4-