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<br />long bridge spanning Fountain Creek was washed out in a flood in 1902 and was replaced by <br />one 70 feet long. Succeeding floods have widened the channel even more, so that the bridge <br />span now exceeds 200 feet. Due to the changing channel capacities, an estimate of the <br />recurrence intervals of past floods would not be valid (Reference 11). Photographs of <br />potential flooding at Manitou Springs are shown in Figures I and 2. <br /> <br />Severe flooding in the Town of Palmer Lake occurs during the summer months as a result <br />of convective-type cloudburst storms. Snowmelt flooding is minor compared to rainfall- <br />produced floods. Steep slopes and soils with low permeability cause rapid storm runoff with <br />minimal warning time for evacuation of the floodplain. The only documented flood damage <br />occurred during the June 17, 1965, cloudburst-produced flood. Shallow depth flooding <br />occurs in Butler Canyon due to overland flow on an alluvial fan. <br /> <br />The water-surface elevations for the 100- and 5oo-year floods at selected locations in the <br />study area of Palmer Lake are shown in Figures 3 through 6. The flood elevation for the <br />June 17, 1%5, flood is also shown in Figure 2, but was not available for the other locations. <br /> <br />2.4 Flood Protection Measures <br /> <br />Two significant water-regulating facilities in the area are Kettle Creek Diversion Dam and <br />Big Johnson Reservoir. The latter is also called Fountain Valley Reservoir Dam No.2 and <br />is located east of the Security-Widefield community. Big Johnson Reservoir is privately <br />owned by the Fountain Mutual Irrigation Company for the primary purpose of irrigation. The <br />drainage area is approximately 3.1 square miles and the maximum storage is 7,000 acre-feet. <br />The dam was modeled as having no effect on the 100- and 5oo-year water-surface elevations. <br /> <br />Kettle Creek Diversion Dam, owned by the U.S. Air Force, is iocated on U.S. Air Force <br />Academy grounds. The earthen dam was constructed for flood control and the reservoir <br />receives water from a drainage area of 16.3 square miles and has a maximum storage of <br />2,900 acre-feet. The dam was designed to detain flows associated with the Standard Project <br />Flood (SPF) for the Kettle Creek basin and limit the discharge to approximately the 10-year <br />recurrence intervaL <br /> <br />The Peterson Field Drainage is controlled by stream-water detention ponds sited at the <br />Peterson Airfield. These ponds substantially reduce the peak flows from the upper 3.5 square <br />miles of drainageway. <br /> <br />The Templeton Gap Floodway (Reference 14) consists of a 10,590-foot-long trapezoidal <br />channel extending from Templeton Gap in a southwesterly direction to Mile 5 on Monument <br />Creek. The floodway has a capacity of 14,000 cfs (approximately a 1oo-year frequency <br />flood). <br /> <br />There are several small earthen dams, stock ponds, canals, and diversion ditches in the study <br />area, but they have no regulatory significance. Generally, the structures divert low flows for <br />irrigation and have little or no effect on major flows. <br /> <br />Portions of several streams in the Colorado Springs area have been channelized in concrete <br />drainageways with sufficient capacity to contain loo-year peak discharges. Streams where <br />this has occurred are Bear Creek, Camp Creek, Douglas Creek (North and South), Sand <br />Creek, Spring Creek, Peterson Field Drainage, Rockrimmon Basin, and South Shooks Run, <br /> <br />14 <br />