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<br />compute annual peak discharges at 14 stations. Data for the storms for <br />which the flood peaks were computed are given in table 7. Table 8 sum- <br />marizes the peak discharges computed from the model and gives the rank of <br />each annual peak at each site. <br /> <br />Flood-frequency characteristics for streams in Dallas were defined <br />by fitting the log-Pearson Type III probability distribution to the 57- <br />year (1914-70) simulated annual-peak discharges for each of the 14 gaging <br />stations. In the log-Pearson method, peak discharges for selected recur- <br />rence intervals are computed by the equation <br /> <br />log QT = M + KS <br /> <br />where <br /> <br />QT the peak discharge for a selected recurrence interval (T) in years; <br /> <br />M the mean of the logarithms of the annual peaks; <br /> <br />K a Pearson Type III frequency factor expressed in number of standard <br />deviations from the mean; and <br /> <br />S = the standard deviation of the logarithms of the annual peaks. <br /> <br />Table 9 gives 7 T-year (recurrence interval) discharges and statis- <br />tics obtained from fitting the log-Pearson Type III distribution to simu- <br />lated annual peak-discharge data for each of the 14 gaging stations. Fig- <br />ures 6 and 7 show the flood-frequency curves plotted by using logarithmic- <br />probability scales. <br /> <br />To ensure that the derived log-Pearson Type III frequency curves fit <br />the observed short-term data, each observed annual peak discharge was <br />plotted at its T-year value, computed from <br /> <br /> T = n+l <br /> m <br />where <br />n = the number of years of record; and <br />m = the numerical rank of the peak discharge. <br /> <br />-32- <br />