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<br />The flood plain of Uncompahgre River at the Town of Olathe is <br />primarily agricultural with light residential development. <br /> <br />2.3 Principal Flood Problems <br /> <br />Floods in the study area generally result from rapid melting of <br />the mountain snowpack from the middle of May through early July <br />and from general rainstorms that normally occur from July through <br />October. Snowmelt flooding is characterized by moderate peak <br />flows, large volume, long duration, and marked diurnal fluctuation <br />of flow. Snowmelt runoff may occasionally be augmented by rain. <br />Rainfloods are characterized by high peak flows of moderate volume <br />and duration. Flooding is more seVere when antecedent rainfall <br />has resulted in saturated ground conditions or when the ground <br />is frozen and infiltration is minimal. Convective-type cloudburst <br />storms, sometimes lasting for several hours, can be expected to <br />occur in the Olathe region during the summer. Runoff from these <br />storms is characterized by high peak discharge, short duration, <br />and small volume. Due to the small areal extent of cloudburst <br />storms, they would have little effect in the study area unlesS <br />they occurred concurrently with rapid snowmelt or runoff from <br />general rain. <br /> <br />The earliest reference to a flood on the main Uncompahgre River <br />comes from the settlers who founded Delta, Colorado, in the early <br />1880s. At that time, an Indian squaw, Chipeta, wife of the famous <br />Ute Chief Ouray, stated that within her lifetime of (then) approxi- <br />mately 50 years, she had seen the Uncompahgre River valley at <br />Delta "flooded from bluff to bluff" (Reference 4). <br /> <br />Records show that, since the turn of the century, notable high <br />flows occurred on Uncompahgre River in 1921, 1927, 1938, 1941, <br />1944, 1947, 1957, 1973, and 1975. The largest known flood, with <br />an estimated peak flow of 5140 cubic feet per second as recorded <br />at the Colona stream gage (approximately 20 miles upstream), occurred <br />in approximately mid-June 1921, as a result of snowmelt. Based <br />on the results of this study, the 1921 flood is estimated to have <br />been slightly larger than the 100-year frequency flood. The only <br />notable cloudburst flood of record occurred in July 1923. Peak <br />flows of the larger historic floods on Uncompahgre River are as <br />follows: <br /> <br />5 <br />