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<br />3. Probability calculations are modified for incomplete records and <br />ze ro-flow yea rs. <br /> <br />4. The existence of low outliers is statistically judged and is cor- <br />rected for inprobability calculations. <br /> <br />Analysis of Recorded Floods <br /> <br />Seasonal flood data for the 17 study sites were recorded during 8 to 10 con- <br />secutive years as shown in table 1. The average record length was about 9 <br />years. The range in annual maximum discharges recorded at each site is shown <br />in figure 2. The maximum peak discharge recorded during the study was <br />7,880 ft3/s at the Wolf Creek near Carlton station (07134300) on August 23, 1969. <br />In terms of runoff per unit area, a maximum of 866 (ft3/s)/mj2 was recorded at <br />the Muddy Creek tributary near Ninaview station (07129200) on May 20, 1977. <br />No flow occurred at 13 sites during at least one water year of the study. <br /> <br />Peak-discharge Frequency <br /> <br />Results of the frequency analysis of the recorded annual peak discharges for <br />each site are shown in table 2. These analyses indicate probable 100-year peak <br />discharges ranging from 270 to 14,400 ft3/s. A comparison between the range in <br />flood frequency (10- to 100-year peak discharges) from this analysis and the <br />range in recorded annual peak discharges is shown for each site in figure 2. <br />The frequency analysis of the recorded floods indicates 15 sites experienced one <br />or more floods greater than the expected 10-year peak discharge (the total years <br />of station record for the study was 155). <br /> <br />Flood Volume <br /> <br />In addition to information on expected peak discharges, designers of bridges <br />and culverts may require estimates of flood volumes when planning for embank- <br />ment storage or flood detention. Although empirical methods are frequently used <br />to make these volume estimates, the large number of recorded flood hydrographs <br />obtained during this study provided sufficient data from which more accurate <br />prediction techniques were developed. This section describes only the analysis of <br />recorded flood volumes; analysis of synthetic flood volumes will be discussed in <br />subsequent sections. <br /> <br />6 <br />