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<br />The main-stem South Platte River stations from Littleton to Henderson <br />experienced peak discharges ranging in magnitude from that of a 50-year flood <br />to 1.4 times the 50-year flood. A multiple of the 50-year flood is used <br />because Matthai's flood-frequency relations are defined only to 50 years and <br />extension beyond that point is considered unreliable. <br /> <br />The implication of the recurrence interval values shown in tables 3 and 4 <br />is that the May 5-6, 1973, storm runoff was generally not statistically signi- <br />ficant in the Denver metropolitan area. In other words, county and municipal <br />planners and residents of the area should be prepared to face--on an all too <br />frequent basis--runoff events of this magnitude on tributaries to the South <br />Platte River. <br /> <br />Detailed runoff records were collected at 5-minute intervals during the <br />stQrm at 19 rainfall-runoff data collection stations throughout the Denver <br />area. Table 5 provides a sample format of the computer printout available <br />for each of the 19 stations; these data may be obtained by contacting the <br />Executive Director, Urban Drainage and Flood Control District, 181 E. 56th Ave., <br />Denver, Colorado 80216. The cost is $5.00 per set, which includes all avail- <br />able precipitation and runoff data as collected by the operational rainfall- <br />runoff data collection stations. <br /> <br />A computer program developed by the U.S. Geological Survey provides a <br />printout of gage height and discharge versus time at these urban area runoff <br />gages. A gage height of 10.00 feet represents the condition of the float <br />resting on the bottom of the well. In most cases, discharges below a gage <br />height of 10.00 feet must be estimated because the intakes to the gage well <br />are above the bottom of the channel. Occasionally, because of silt in the <br />gage well, a stage greater than 10.00 feet will be recorded for a period of <br />time. The discharge hydrograph must be estimated for these periods because <br />the recorded stage does not represent the stage in the stream. <br /> <br />All runoff data included in this report are preliminary and subject to <br />revision. <br /> <br />17 <br />