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<br />mainly of subalpine <br />pine trees. Alpine <br />timberline. <br /> <br />fir, aspen, Engelmann spruce, and <br />willow, grasses, and sedges exist <br /> <br />lodgepole <br />above the <br /> <br />2.3 Principal Flood Problems <br /> <br />The principal cause of flooding on Little Salt Wash in the Fruita <br />study area is intense rainfall from cloudburst storms. The <br />convection-type cloudburst storm, generally of small aerial extent, <br />accounts for approximately one-half of the normal annual <br />precipitation in the Fruita area. Cloudburst storms can be <br />expected anytime during late summer and early fall. Cloudburst <br />floods characteristically have high peak flows, high velocities, a <br />short duration, and a small volume of runoff. <br /> <br />The principal cause of flooding on the order of a 100-year <br />recurrence interval along the Colorado River in the study area is <br />rapidly melting snow during May, June, and July. Snowmelt <br />augmented by rain causes flooding on the order of a 500-year <br />recurrence interval. Snowmelt flooding is characterized by <br />moderate peak flows, large volume, and long duration, and is marked <br />by daily fluctuations in flow. Rainfall on melting snow may hasten <br />the melting process and increase floodflow. General rain floods <br />are caused by prolonged heavy rainfall over large areas and are <br />characterized by high peak flows of moderate duration. Flooding is <br />more severe when antecedent rainfall causes saturated ground <br />conditions or when the ground 15 frozen and infiltration is <br />minimal. <br /> <br />Fruita has experienced a number of floods in the past as indicated <br />from historical records, limited newspaper coverage, and interviews <br />with local residents and officials (Reference 4). Cloudburst <br />storms frequently cause flooding on Little Salt Wash. An example <br />of such a flood is the large flood which occurred around 1902. No <br />estimate of the recurrence interval of this flood is available <br />because there are no photographs of the flooding, no st ream gage <br />records, and high-water marks have not been identified. <br /> <br />The Colorado River has caused numerous large floods in the Frul ta <br />area. The earliest such flood known occurred in June and July <br />1884. This is generally considered to be the most severe flood in <br />Fruita. It resulted from the rapid melting of a deep snowpack <br />accompanied by heavy rains. Other floods attributed to the <br />Colorado River were recorded in 1917, 1920, 1921, 1935, 1952, 1957, <br />1970, 1983 and 1984, Peak flows on the Colorado River at the state <br />line were approximately 61,000 cubic feet per second (cfs> and <br />70,000 cfs in 1983 and 1984 respectively. <br /> <br />All major streams in the Fruita area were overflowing in May~ June~ <br />and July 1884. The maximum peak discharge on the Colorado River at <br />Fruita occurred on July 4 with an estimated discharge of 125,000 <br />cfs. The 1921 flood had an estimated discharge of 81,000 cfs. <br />Based on the results of this study, the recurrence interval for the <br /> <br />6 <br />