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<br />For each basin, the synthesis phase resulted in the simulated peak discharge <br />and flood volume for a total of over 10,000 floods derived from the long-term <br />rainfall data for Denver, Pueblo, and Amarillo. These data were included in both <br />a frequency analysis of the annual-flood series and a regression analysis of flood <br />volume. <br /> <br />Peak-Discharge Frequency <br /> <br />The flood-frequency analysis of each annual-flood series provided three <br />separate estimates of the flood-frequency relation for each station. Because the <br />frequency results of the "Denver synthesis" was within 20 percent of the "Pueblo <br />synthesis," it was not considered in determining a single "best-estimate" of the <br />synthetic flood-frequency relation for each station. The two remaining synthetic <br />relations, those created using the Pueblo and Amarillo long-term precipitation, <br />were combined by weighting the 1-hour, 100-year precipitation at each station <br />relative to that for Pueblo (2.7 in.) and Amarillo (3.5 in.). The 1-hour, <br />100-year storm was selected for this procedure because storms recorded in the <br />Arkansas basin averaged about 45 minutes in length (fig. 3) and because primary <br />emphasis in the study was on the less frequent storms. The weighting equation <br />used was: <br /> <br />3.5-I1,lOO <br />Q Synthetia =QPueblo 0.8 +Q A marUlo <br /> <br />I1,lOo2.7 <br />0.8 <br /> <br />(3) <br /> <br />where: I1,lOO=1-hour 100-year precipitation intensity. (See section on Independ- <br />ent Variables and table 8.) <br /> <br />For precipitation intensities less than 2.7 inches, full weight was given to the <br />"Pueblo synthesis." <br /> <br />The final synthetic peak-discharge frequency results using this procedure <br />are summarized in table 2. As shown in figure 2 and table 2, the values for <br />synthetic flood-frequency relations were generally larger than the values for <br />recorded flood-frequency relations. In terms of runoff per square mile of con- <br />tributing drainage area, the average (15 stations) 100-year flood discharge was <br />found to be 1,140 (ft3/s)/mP from the synthetic data and 959 (ft3/s)/mP from <br />the recorded data. For the 15 stations modeled, the comparisons shown in figure <br />2 indicate that four sites experienced a flood greater than the synthetic 10-year <br />peak discharge (155 years of station record), and that only 2 stations (07099250 <br />and 07124700) had a calibration event with a frequency of occurrence greater than <br />once in about 10 years. <br /> <br />16 <br />