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<br />Hydroloqic Analysis <br /> <br />. <br /> <br />~e 100-year discharge was selected as suitable for <br />planning purposes, since this frequency is widely accepted by <br />most federal agencies and has been adopted by the state legis- <br />lature. <br /> <br />~e 100-year flood was then estimated by four separate <br />methods, which are generally classified as "stochastic," since <br />they are dependent upon a statistical analysis of stream gaging <br />data. A synthetic, or parametric, analysis was not used in this <br />study, due to the various complexities in evaluating the many <br />geologic, geographic, climatic, and meterologic aspects and the <br />dubious reliability of this method in the high-mou~tain environ- <br />ment. <br /> <br />" <br /> <br />~e 100-year frequency flood discharge was selected at <br />2,500 cfs. based on a comparison of the peak discharges estimated <br />by the four methods. These estimates ranged from 1,408 cfs to <br />2,890 cfs, as summarized below. <br /> <br />The remaining paragraphs of this section describe in <br />detail each of the methods used to arrive at the selected <br />. discharge. <br /> <br />. <br /> <br />Summary of Calculated Discharges <br />Anthracite Creek Near Erickson Springs <br /> <br />Method <br /> <br />Source <br /> <br />100-Year <br />Discharge <br />CFS <br /> <br />Regional extrapolation <br /> <br />WSP 1683 <br /> <br />2,243 <br /> <br />Comparison to log Pearson <br />distribution for station <br />on East Muddy Creek near <br />Bardine <br /> <br />CWCB TM-l <br /> <br />1,870 <br /> <br />Regression Equations <br /> <br />CWCB TM-l <br /> <br />1,408 <br /> <br />Comparison to peak dis- <br />charge ratios for <br />similar watersheds <br /> <br />Reference 4 <br /> <br />2,890 <br /> <br />Synthetic Analysis <br /> <br />SCS <br /> <br />Not computed <br /> <br />Selected Discharge <br />. <br /> <br />Conserative <br />Judgement <br /> <br />2,500 <br /> <br />II <br />