|
<br />, ,
<br />
<br />.
<br />
<br />.
<br />
<br />1965 HOLLY (June 16 - 18)
<br />1981 FRIJOLE CK
<br />1997 FT COLLlNS
<br />1997 PAWNEECK
<br />
<br />.
<br />
<br />1935 "A" (May 30,31, 1935)
<br />1935 HALE
<br />1965 PLUM CK (June 16)
<br />1965 FALCON (June 17)
<br />. 1965 PLUM CK+ FALCON
<br />Next, the area-weighted average rainfall is determined, Then, a flood hydrograph is created using HEC,I and the flood j
<br />routed into the reservoir,
<br />RFIRO Modeling: Using HEC-1, the same USACE UG and input parameters were utilized and a duplicate effective
<br />model was developed that was calibrated to the USACE 1995 PMF model. All storm mass curves in this project are
<br />storm specific, in keeping with the site-specific nature of the overaIl PMP project.
<br />Routing: For this procedure, the Same USACE HEC-I data file was utilized, The antecedent flood pool for the Cherry
<br />Creek Reservoir was the only parameter that varied from the original study,
<br />
<br />.
<br />
<br />.
<br />
<br />.
<br />
<br />.
<br />
<br />.
<br />
<br />.
<br />
<br />.
<br />
<br />At this time, Mr, Trieste displayed the results of his study, showing the various resulting flood reservoir levels as compared
<br />to the Corps PMP PMF overtopping level, as weIl as comparisons to the other storms analyzed as part of this preliminary
<br />PMF study,
<br />
<br />Mr, Urbonas stated that studies have shown that the HEC,l model can produce consistently high flood levels that were not
<br />observed in nature, Mr, Trieste replied that while one of the May 1935 A-Zone centers does not produce a flood that
<br />matched the observed discharge in Kiowa Creek, the A-2 center does indeed come very close to the observed discharge, thm
<br />pointing out a possible discrepancy in the original storm pattern,
<br />
<br />Mr, Miller stated that the storm that drove the PMP value of 24 inches in the original 1995 study is actually around 16 inche:
<br />due to the fact that the storm occurred over an eight,hour duration, in the middle of the storm event.
<br />
<br />Mr, Urbonas mentioned that infiltration rates at Y, inch an hour will result in complete saturation in about 3 hours in this
<br />basin and that any more rainfall wi!! runoff rather than infiltrate, so this is something that should be taken into consideration,
<br />
<br />Mr. Lang then added that these preliminary PMF values are only a sensitivity analysis of the original PMP and should not be
<br />taken for face value and should not leave this meeting, Mr, Urbonas added that infiltration tests should be conducted in the
<br />basin before the PMF study is completed,
<br />
<br />Dr. Tomlinson stated that this Same preliminary PMF study would be completed for the Fort Collins and Pawnee Creek
<br />- storms of 1997, as well as for the 1935 Hale Center, the 1965 Holly Center, and the 1981 Frijole Creek storm,
<br />At this point, Mr, Lang concluded the meeting by reminding everyone in attendance of the final meeting date of July :td,
<br />2002,
<br />
<br />Summary overview.
<br />A W A agrees with the NWS computations for their PMP study fmdings, BasicaIly, the calculations are corrected, The AWl
<br />study is a regional PMP and does consider only region large storms of which 16 were used, The A W A technical review
<br />recommendations for the input parameters for the NWS PMP procedures, The Interim Report # 2 wiIl present A W A's
<br />recommendations for a Cherry creek basin PMP study, The draft report is due May 17'h The fmal project meeting and draf
<br />final report is scheduled for July 2, 2002,
<br />
<br />Flood Protection. Water Supply Planning and Finance. Stream and Lake Protection
<br />Water Supply Protection. Conservation and Drought Planning
<br />
|