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I 76-1(35) PE A preliminary study for the Federal Insurance Administration by Gingery Associates Inc. predicts Q100 = 25,000 cfs below Sheridan Boulevard, which is below the Ralston Creek confluence. The Water Resources Division of the USGS is preparing a study of Clear Creek in Jefferson County. No published values are presently available. Discussion of Analyses A range of discharges are available from the various described analyses. The range is too large to select the mean as a reliable value. Gages on Clear Creek with their many years of record should provide good confidence. However, we concur with the U. S. Corps of Engineers that the true flood potential through this study reach probably has not been realized. The retention effects of the sand and gravel pits, irrigation diversion and channel storage have lowered the peak flow at Gage 6-7200. Thus it is felt that this gage gives too low a prediction. Consideration of stream gages with similar characteristics should indicate the potential range of floods. Rather than an average of all these gages, the higher values of Q100 were weighted more heavily. Certainly the gage on Bear Creek at Morrison, No. 6-7105, with 62 years of record, is a good indicator. The Bear Creek and Clear Creek at Golden gages are similar when adjusted for drainage area below 7500 feet. These gages with their high confidence limits should represent the upper limits of the predicted discharge. Technical Manual No.1 is a result of extensive study. This method gives quite high peak predictions for Clear Creek unless weighted by the gages. Weighted values using 50 years of equivalent record are assigned good confidence. The U. S. Corps of Engineers have discounted their earlier prediction by suggesting a range for the lOa-year flood from 15,000 to 25,000 cfs at the mouth. They are not prepared to make a final prediction at this time. 10 -