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<br />In re-analyzing the data now available for the gage at the <br />bluffline, two sets of data were used. The guidelines in <br />Bulletin #17B using a regional skew of +1.0 were followed <br />closely for each set of data. <br /> <br />Station statistics were calculated using all of the <br />available data from 1882 through 1984, including an <br />estimated event of 21,000 cfs for the 1891 flood, and 25,000 <br />cfs for the 1904 flood. Using 103 da1:a points with a mean of <br />3424 cfs, standard deviation of 0.225, the station skew was <br />calculated to be 1.04. The station skew was 'weighted with a <br />regional skew of 1.0 to produce a weighted skew of 1,03. <br />This was used by our firm to calculate a 100-.year peak <br />discharge of 16,579 cfs. <br /> <br />Assuming that the Halligan Reservoir does affect the post <br />1910 records, the gaging data from 1910 to 1984 was <br />analyzed. The data was historically adjusted to include the <br />1891 and the 1904 events and the station statistics were re- <br />calculated. Note that a sensitivity analysis of the record <br />indicated inclusion of the 1891 event as part of the <br />historic extension. The calculated skew of 1.10 was weighted <br />with the regional skew of +1.0, and the calculated 100-year <br />peak disCharge was found to be 16,391 cfs. <br /> <br />Note that the original value calculated by the Corps in 1973 <br />lies within the fifty percent confidence interval of both of <br />these values. <br /> <br />Near Greeley <br /> <br />As stated previously, the peak 100-year discharge calculated <br />in the 1973 Corps report for the gage near Greeley was 9,400 <br />cfs. In our analysis of the data available at that time, the <br />station statistics calculated by our firm deviated from <br />those reported by the Corps by an amount consistent with <br />those calculated for the gage at the bluffline. Again, this <br />is assumed to be roundoff error. By assuming a normal <br />distribution (a skew of O.Ol, and using our station <br />statistics, a value of 9,678 cfs was calculated for the peak <br />100-year discharge. <br /> <br />The 1981 Corps study reported a slightly lower discharge <br />using gaging records through 1976. This was confirmed in our <br />analysis using an adopted skew 0.0. The laO-year peak <br />discharge was calculated by our firm to be 9,550 cfs, which <br />is indeed lower than our value for the 1973 data set. <br /> <br />By adjusting the data set to reflect the flood of 18,000 cfs <br />in 1904 as the largest event since 1864, the Corps report <br />indicated that the peak disCharge of 9,440 cfs should be <br /> <br />Page 9 <br />