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<br /> <br />As stated in the main text, subarea flood discharges into the South <br /> <br />Platte River from Chatfield Dam to Narrows damsite were stream routed <br /> <br />and combined by the ADP program MODWIL, which does the computations <br /> <br />for the Modified Wilson Method. The routing criteria selected for <br /> <br />each reach of the South Platte River are listed in attached Table A-], <br /> <br />Moderate frequency flood nrrp) for Nanows damsite, - There are some <br /> <br />instances in which. a moderate frequency flood hydrograph can be <br /> <br />obtained by a direct adjustment of an IIlf hydro graph. This approach <br /> <br />was not considered applicable in this study because of the large <br /> <br />drainage area. It seemed unreasonable to assume that each subarea <br /> <br />wo~ld contribute proportionally less runoff during MFF conditions as <br /> <br />compared with IDF conditions. Therefore, the approach of computing a <br /> <br />MFF flood hydro graph by the unitgraph procedure was adopted. However, <br /> <br />it was possible to simplify the computations as described in the main <br /> <br /> <br />text by utilizing results of the detailed IDF computations;. <br /> <br />The retention loss criteria for computing excesses for the MFF were <br /> <br />. adopted after investigations showed that antecedent moisture condi- <br /> <br />tion for the Cherry Creek and Plum Creek drainage basins preceding <br /> <br />the heavy rain of June 16. 1965, fitted the definition of AMC'I. It <br /> <br />was also noted that runoff curve numbers indicated for each basin by <br /> <br /> <br />the runoff from the June 16, 1965 storm, when converted to AMC II <br /> <br />curve numbers, agree closely with the curve number selected for use <br /> <br />for each basin in the Narrows IDF contribution computations. <br /> <br />22 <br /> <br />'......."'-.... <br /> <br />-.........: <br /> <br />.\,.....,. <br /> <br />',~~~- <br /> <br />.,.(' <br />..: . ii ,_. ,~k-... ~","::l!Jfh" . <br /> <br />...:;. <br /> <br />,. <br />." . <br /> <br />, ..... <br /> <br />~ <br />