Laserfiche WebLink
<br />, <br /> <br />Fzle: PMPtopics799S1lmmary.doc <br /> <br />D124r=-r <br /> <br />July 21, 1999 <br /> <br />This referred to items done inliydro 45 that were not needed for the antecedent <br />study. The time constraints did not affect the quality of the study. Group agreed <br />this was satisfactory answer. .. ' <br /> <br />e <br /> <br />15. The region within which storms should have meteorologically honwgeneous <br />characteristics with storms that could occur over the Cherry Creek drainage basin is <br />defined on p2 of the study. The eastern most boundary of the region is 105.9 degrees <br />West longitude. In comparing this eastern limit with the 29 storms in deriving the <br />withinlwithout storm curves in ~/R.52, there is no overlap. This appears to be stating <br />that any storms east of 105.9deg,.ees West are not to be considered to have <br />meteorologically homogeneous characteristics with the Cherry Creek drainage basin <br />location., The only Colorado stonn used in withinlwithout curves derivation in ~/R <br />52 (Hale, 1935) does not fall within this region. This indicates an inconsistency <br />between this study and the site-specific PMP study. (Tomlinson) <br /> <br />Correct that the boundary is 104.3 degrees longitude. No consensus is reached by V <br />the group. The NWS will examine a way to verify this assumption <br /> <br />16. NWS HYDRO 45, dated January 1995, states on page 75, Fimling 15 that "By <br />logical deduction and extension, the conclusion is that a reasonable and prudent <br />antecedent precipitation associated with a 3- to 5-day PMP event in the region of study <br />would be 10-20 percent of the PMP within a 31-day period centered on the doy of <br />maximum precipitation in the PMP storm for the region of study." Explicitly what <br />caused the difference between this 10-2.0% and 32% provided in the Cherry Creek <br />antecedent precipitation study ? (Tomlinson) <br /> <br />e <br /> <br />We (USACE) will investigate the possiblity of and impacts from revising the <br />antecedent study. . <br /> <br />17. Often dam regulators us!! the 100-year event, e.g. rainfall or snawmelt, as the <br />antecedent condition. What is the retum frequency of the 32% PMP event for the <br />Cherry Creek drainage basin? If the PMP is seven times the 100-year rainfaD, that <br />should nwke the antecedent rainfall 32% of seven or 2.24 times the 100-year rainfaD <br />values. Haw does this compare to the antecedent rainfall used for other Corp Projects, <br />in particular Cochise and Elephant Butte in New Mexico? (Tomlinson) <br /> <br />The USACE guidelines state an antecedent flood of 50% of the PMF with a 5-day <br />drawdown or a half full flood control pool (which ever is more appropriate) is e <br /> <br />~t;'h~ '-~::,'_- ..:'~::.-;:~~:J"":::': .:.:-~ .,' .::" '~':--::-', ~ ".~,' . i <br />--~-_.-,--- .--n"'..TDJ1&C$to 21 JIIIy 1m T<<:Iurictd M<<ti1Ig <br />~~~~t~~~~~~~.~'~?-'::;'\--'-'~~':;;'::~~\:':: :-,:". <br /> <br />4 <br /> <br />~5~;'~;f1~i;~::,-~. <br />