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<br /> <br />Table 5. Flood Peaks for the 10-, 50-, and tOO-Year Events at Selected Design Points <br />Including Storage Effects of Detention Along Chase and Eureka/Gregory Gulches. <br /> <br /> <br /> <br />Note; See Figure 4 for design points. <br /> <br />Table 5 indicates the reservoirs slightly reduce flood peaks along North Clear Creek. At <br />design point Nl at the City limits, for example, the reservoirs reduce 100-year flood . <br />peaks from 2702 to 2520 cfs, <br /> <br />Table 5 indicates the time of concentration for North Clear Creek is less than the time of <br />concentration for Gregory and Chase Gulch, which is counter-intuitive given the relative <br />size of the watershed areas. The time of concentration difference is partly due to the <br />different precipitation distributions used for the model. The "Type IA" distribution is <br />less peaked and, as a result, causes a later peak than the "Type II" distribution. Flood <br />peak attenuation by Chase Gulch Reservoir also increases the time of concentration for <br />Chase Gulch. <br /> <br /> <br />In the 1979 study, the 500-year flood peak for North Clear Creek equals 3800 cfs <br />upstream of Chase Gulch and 4950 cfs at the wastewater treatment facility, and the 500- <br />year flood peak for Gregory Gulch and Chase Gulch equals 1790 cfs and 2100 cfs, <br />respectively, at their confluence with North Clear Creek. These flood peak estimates <br />were identified using frequency analysis. Since the reservoirs are assumed ineffective <br />during the 500-year event, the 500-year flood estimates are not modified by the TRZO <br />model study. <br /> <br />-13- <br /> <br />