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<br />failure II condi cions. The brea~h par8metE~rs d.escribed in the previous section <br /> <br />were used in this analysis. By defitliticlD, the threshold flood has a maximum <br /> <br />pool elevation equal to the top of dam elevati.oll minus the required freeboard; <br /> <br />therefore, the failure elevation was set at I~his level, elevation 5639.5 feet <br /> <br /> <br />m.s.l. <br /> <br />The threshold flood, with a peak inflow of 400,600 c. f. s. and a total volume <br /> <br />of 210.400 acre- feet, has a peak pool elevation of 5639.5 feet m, s. 1. and a peak <br /> <br />spillway discharge into Toll Gate Creek of 34,500 c.f.s. <br /> <br />With dam failure during the threshold flood, the pe,ak pool elevation and <br /> <br />peak spillway discharge are approximately t:he Same as without dam failure but the <br /> <br />discharge dmrn Cherry Creek, which is limited to t:he discharge through the outlet <br /> <br />works in the "without: failure'! condit:ton, is increased tremendously. The peak <br /> <br /> <br />discharge as determined by DAMBRK, would be approximately 1. 7 million c, f. s. The <br /> <br />breach outflow hydrograph and the spillway outflo>l hydrol>raph for the "with" and <br /> <br />'!"Tithout failure" conditions were ro1-lted using the Harders routing program. <br /> <br />Table 6 swnmarizes the routings at several locations .along the creeks. The <br /> <br />"arrival timell shown in the table is defined as t:he number of hours between the <br /> <br />time when the reservoir reaches the top of t:he flood control pool (elevation 5596 <br /> <br /> <br />feet m. s.1.) and the time when the flood wave arrives at the particular location, <br /> <br /> <br />Likewise, the peaking time is defined as the number of hours between when the <br /> <br /> <br />reservoir reaches the top of the flood conl:rol pool and when the peak di.scharge <br /> <br />occurs at a given location. These definitions depart from the definitions <br /> <br /> <br />proposed in the "Guidelines'! but are more representative of the ,'3.ctual amount of <br /> <br />time available to issue warnings and evacuate residents from the threatened <br /> <br /> <br />areas. The table also provides a method to determine the arrival time and <br /> <br />peaking time based on the time when tne b)~each formation begins for the Ilwith <br /> <br />failure" condition. The extent of flooding on Toll Gate and Sand Creeks for the <br /> <br /> <br />"with" and llwithout failure" conditions I and on Cherry Cr€!ek and the South Platte <br /> <br />25 <br />