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<br />adjusting the fit for partial duration series and expected <br />probability. The resulting curve (Appendix 3) was based on a <br />mean discharge of 3,444 cfs, and a standard deviation of <br />0.232. The resulting 1% (lOO-year) discharge was calculated <br />by the Corps to be 17,400 cfs. <br /> <br />In the 1981 study, analytical methods outlined in the Water <br />Resources Council Technical Bulletin #17 (ref 4), were used <br />by the Corps to analyze the gage l:ecord. In their study of <br />the effect of storage structures upon flood routing through <br />the basin, the Halligan Reservoir appeared to have an <br />attenuating effect on the discharge of the river. <br />Consequently, the period from 1910 to 1976 was selected as <br />being the most representative of the available data. <br />Rainfall and runoff from the storm which caused the flood of <br />1904, however, apparently occurred downstream of Halligan, <br />and was largely unaffected by storage in the reservoir, <br />Based on the previously estimated discharge of 25,000 cfs, <br />the record was synthetically extended to include this flood. <br />The adjusted data set was tl1en analyzed to provided station <br />statistics (mean, standard deviation, and station skew). The <br />resulting station skew coefficient of +1.3 was weighted with <br />a generalized skew of +1.0, obtained from a Corps study of <br />regional streams. The resulting skew of +1.2 was then used <br />by the Corps to shape the log-Pearson curve (Appendix 4). <br />Upon adjustment for expected probability and length of <br />record, the peak discharge of 17,400 cfs computed in the <br />1973 study was found to be represE~ntative of this gage and <br />was published in Table 7 (Appendix 4) of the 1981 Corps <br />study. <br /> <br />In addition to the above mentioned analytical methods, an <br />extensive study of the mountainous area of the basin was <br />performed by the Corps in their 1981 study in order to <br />calibrate and run the Massachusetts Institute of Technology <br />Catchment Model (MITCAT) computer program. The reSUlting <br />discharge probability curve was displayed along with the <br />analytical curve in the corps' final report (Appendix 4), <br />and appeared to confirm the analytical procedure used. <br /> <br />Near Greeley <br /> <br />The 1973 Corps study evaluated the diSCharge data using <br />Beard's analytical method (log-Pearson Type III), and <br />concluded that the relationship was normally distributed, <br />adopting a skew coefficient of 0.0. The fit was adjusted for <br />expected prObability and partial duration series. Based on <br />51 years of record with a mean discharge of 813 cfs, and a <br />standard deviation of 0.457, the resulting 1% (IOO-year) <br />discharge was calculated as 9,400 cEs (Appendix 3), <br /> <br />Page 4 <br />