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<br />runoff and sediment production. <br />Indian Wash. <br /> <br />Snowmelt flooding is negligible on <br /> <br />Information from local residents indicat(s that before construction <br />of the U.S. Soil Conservation Service IW-l flood retention <br />structure, damaging floods occurred on an average of every 6 years. <br />Precipitation records indicate that large storms occurred in <br />September 1896, May 1906, October 1908, August 1921, August 1938, <br />September 1941, June 1954, May 1955, and June 1958. The 1908 storm <br />produced the largest 24-hour total precipitation of 2.50 inches. <br />The 1938, 1954, 1955, and 1959 storms were storms over the upper <br />portion of the watershed with little precipitation being recorded <br />in Grand Junction. The 1958 flood is the only flood with <br />documentation on flood heights and damages. The storm caused <br />sediment and water damage to residences, business establishments, <br />and streets. The total damages were estimated at <br />$25,000.Considerable overland flow resulted, but depths were not <br />excessive (Reference 6). The 1958 flood has been estimated to be <br />greater than the 100-year flood. <br /> <br />Figures 3 and 4 show photographs taken during and after the <br />June 6, 1958, flood. <br /> <br />Sheet flooding from the Horizon Drive Channel would occur in the <br />Mesa Mall area when a conduit located near the entrance to the mall <br />is overtopped by high floods. This conduit can carry only flows of <br />less than 10-year recurrence interval. It runs from 24t Road, <br />under the parking lot, to its confluence with Leach Creek. <br /> <br />2.4 Flood Protection Measures <br /> <br />Levees along the southern bank of the Colorado River downstream <br />from its confluence with the Gunnison River were constructed by <br />local interests to protect residents in the Connecticut Lakes area. <br />Low dikes were also constructed along the northern bank of the <br />Colorado River upstream from the Grand Avenue bridge to provide <br />protection to residents of the Riverside Park area. Both the <br />levees and the dikes are overtopped by the 100- and 500-year <br />floods. <br /> <br />Major reservoirs controlling the Colorado and Gunnison Rivers above <br />Grand Junction are Granby, Green Mountain, Dillon, Williams Fork, <br />Reudi, Taylor Park, Vega, Paonia, Morrow Point and Blue Mesa. The <br />reservoir storage capabi 1 i ties are shown in Table 1. The Granby, <br />Green Mountain, Dillon, Williams Fork, and Reudi Reservoirs are <br />fill and spill type structures with only incidental flood control <br />storage. <br /> <br />In the Gunnison River drainage basin, regulations for JOInt <br />conservation-flood control operation of Pannia Reservoir have been <br />prepared by the COE and the U.S. Bureau of Reclamation. The <br />conservation operation of Blue Mesa Reservoir provides substantial <br />flood control benefits, but formal operating regulations for flood <br />control have not been prepared. Inflow to Blue Mesa was routed <br /> <br />7 <br />