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<br />I <br />I <br />I <br />I <br />I <br />1 <br />I <br />1 <br />I <br />1 <br />1 <br />I <br />I <br />1 <br />1'-' <br />1 <br />I <br />I <br />I <br /> <br />HYDROLOGIC AND HYDRAULIC DETERMINATIONS <br /> <br />Hydrologic Analysis <br /> <br />A hydrologic analysis was performed to determine the peak discharge- <br /> <br /> <br />frequency relationships for floods of the 10-. 50-. 100-. and 500-year recur- <br /> <br /> <br />rence intervals for the White River. Sulphur Creek and Sanderson Heights at ' <br /> <br />Meeker. <br /> <br />Peak flood flows on the White River are based on sixty-six years of <br /> <br /> <br />stream-gaging records at a station operated by the U.S. Geological Survey <br /> <br /> <br />(Reference 1 & 2) 2t miles east of Meeker. Annual peaks were plotted on <br /> <br /> <br />probability paper using Hazen plotting positions. Annual flood peaks on the <br /> <br />White River occur in the late spring and early summer months and are usually <br /> <br />caused by melting snow. However. the occurrence of flood peaks in late June <br /> <br />and July indicate snow melt is augmented by rainfall. To determine the effect <br /> <br />of rain floods on the disCharge-frequency curve. the Bureau of Reclamation I s <br /> <br />procedure for determining inflow design floods for small dams (Reference 3) <br /> <br />was used to establish an upper limit and a trend for lower frequency floods. <br /> <br />The Probable Maximum Flood and flood based on "Assumption B" were computed <br /> <br />and plotted on the discharge-frequency curve for this purpose. The curve was <br /> <br />then adjusted in the lower frequency range to reflect the possibilities of rain <br /> <br />floods on the White River. see Figure 1. This adjustment of the curve was <br /> <br />made at the request of the Colorado Water Conservation Board to make the <br />11 <br />