Laserfiche WebLink
<br />, <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />The Log Pearson Type III method is widely used as a uniform distribution tec- <br /> <br /> <br />nique, especially by the U. S. Government agencies. <br /> <br />It was possible to obtain from Soil Conservation Service, tables for K values <br />used in the Log Pearson Type III method, covering return periods greater than 200 years. <br />This data afforded us ,-he oppoli"unity <br />TO compare the computed values for the 500-year flood with that obtained from <br />using linear based on flood discharges computed for discharges <br />up to 200-year frequency. <br /> <br />Peak flows obtained from these frequency distributions for the 10-, 50-, 100-, <br />and 500-years for 18 different locations are shown in Table 11. The values for the 500- <br />years frequency include both the values obtained from the Log Pearson Type III method <br />and linear extrapolation beyond i"he 200-years frequency. <br /> <br />Peak flows recorded at Gunnison River near Gunnison were compared with the <br />combined peak flows recorded for Taylor River, East River and Ohio Creek for the same <br />period. Recorded flows used for these three rivers were at streamflow measuring stations <br />for Taylor River at Almont, East River at Almont and Ohio Creek near Baldwin. The <br />period of record used in this comparison included 1961 - 1971. The results of this analy- <br />sis showed that the average daily peak flow for the 11 years period was 3,079 cfs for <br />Gunnison River at Gunnison and 3,028 for the combined peak flows of the three rivers. <br />This variation represents about 1.7% deviation, which could be attributed to the flows <br />from area lying between the three upstream tributary stations and Gunnison River station near <br />Gunnison. This area is approximately 125 square miles in size and represents about 14% <br />or the area upstream from Gunnison station near Gunnison. This indicates that the run- <br />off yield during periods of peak flow from these low lying areas is very low, further sup- <br />porting the conclusion that precipita1"ion from upper elevations is j"he major contributor to <br />peak flows. <br /> <br />-7- <br />