Laserfiche WebLink
<br />the subregion and subdivision of the basin, as defined in HMR 55, the PMP <br /> <br />estimates were adjusted by the appropriate areal reduction factors to obtain the <br /> <br />1-, 6-, 24-, and 72- hour PMP estimates. Depth-duration curves were plotted so <br /> <br />that intermediate values could be interpolated and the incremental depths <br /> <br /> <br />computed. <br /> <br />Losses of 0.5 inch per hour over the entire basin were applied to the <br /> <br />rainfall values to evaluate the "existing conditions" PMF runoff. The resulting <br /> <br />16.25 inches of runoff, when applied to the unit hydrograph, produced a PMF <br /> <br />hydro graph with a peak discharge of 635,800 c.f.s. and a total volume of 333,700 <br /> <br />acre-feet. These runoff values were utilized in the existing threshold flood <br /> <br /> <br />determination, <br /> <br />Losses of 0.5 inch per hour over the basin above the Castlewood Dam site and <br /> <br />0.3 inch per hour between the Castlewood Dam site and Cherry Creek Dam were used <br /> <br />to evaluate the "fully developed. conditions" PMF runoff. The "fully developed <br /> <br />conditions" PMF hydrograph has a peak discharge of 662,700 c.f.s. and a total <br /> <br /> <br />volume of 359.200 acre-feet from 16.25 inches of runoff above the Castlewood Dam <br /> <br />site and 18.53 inches of runoff from the area between the Castlewood Dam site and <br /> <br />Cherry Creek Dam for a basin average of 17.50 inches of runoff. The determina- <br /> <br />tion of the Base Safety Condition (BSC) and the array of dam safety modification <br /> <br /> <br />alternatives were made using the "fully developed conditions" runoff values. The <br /> <br /> <br />PMF rainfall and runoff for the "existing conditions" and the runoff from the <br /> <br /> <br />portion of the basin between the Castlewood Dam site and Cherry Creek Dam for the <br /> <br /> <br />"fully developed conditions" are shown in table 3. <br /> <br />18 <br />