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<br />gage is located. The second choice is to use published relationships <br />[e.g., (g)]. <br />Except for the preceding discussion of the the partial-duration <br />series, the procedures described in this guide apply to the annual flood <br />series. <br /> <br />B. Statistical Treatment <br />1. The Distribut10n--Flood events are a succession of natural <br />events which, as far as can be determined, do not fit anyone specific <br />known statistical distribution. To make the problem of defining flood <br />probabilities tractable it is necessary, however, to assign a distribution. <br />Therefore, a study was sponsored to find which of many possible distribu- <br />tions and alternative fitting methods would best meet the pw:poses of this <br />guide. This study is summarized in Appendix 14. The Work Group concluded <br />from this and other studies that the Pearson Type III distribution with <br />log transformation of the data (log-Pearson Type III distribution) <br />should be the base method for analysis of annual series data using a <br />generalized skew coefficient as described in the following section. <br />2. Fitting the Distribution~-The recommended technique for fitting <br />a log-Pearson Type III distribution to observed annual peaks is to <br />compute the base 10 logarithms of the discharge, Q, at selected exceedance <br />probability, P, by the equation: <br />Log Q=X"+KS (1) <br />where X" and S are as defined below and K is a factor that is a function <br />of the skew coefficient and selected exceedance probability. Values of <br />K can be obtained from Appendix 3. <br />The mean, standard deviation and skew coefficient of station data <br />may be computed using the following equations: <br /> <br />9 <br />