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<br />1~' ......... <br /> <br />the 72-hour duration period since no storm rainfall analysis data provided rainfall values beyond <br />the 24-hour duration period, <br /> <br />A W A had no way, based on rainfall data, to determine appropriate increases in rainfall values <br />beyond the 24-hour duration period, The application of the 10% factor was an attempt to <br />provide rainfall values out to the 72-hour duration in a way that was somewhat consistent with <br />NWS analysis results, A W A had no information on how the NWS determined rainfall values <br />for the 48-hour and 72-hour duration periods, The determination of the 10% increase factor was <br />based on information provided in Tables 1 and 6 of the NWSSSS for the 10-square mile area size <br />and point area size. Using the 24-hour and 72-hour values from Table 1, an increase of <br />approximately 9% is determined. Using the HMR 55A lO-square mile values from Table 6, an <br />increase of approximately 15% is determined, Using the point rainfall values from Table 6 for <br />the NWSSSS, an increase of approximately 12% is determined. Based on these increases, A W A <br />applied a 10% increase from the 24-hour rainfall value to get 48-hour and 72-hour rainfall <br />values, <br /> <br />22, Page 122. How as the 11.82 inches for the combined June 16 & 17 1965 storm computed? <br />Note: adding the storms together would result in a value of 12.17 inches, <br /> <br />A W A response to Question 22. <br /> <br />The value of 12.17 is the correct value. Fortunately use of the incorrect value of 11.82, although <br />providing a lower total adjusted value for the combined storms, did not influence the final PMP <br />values. <br /> <br />23. Page 123. Where is the backup data for the Depth Duration envelopment curve? <br /> <br />A W A response to Question 23. <br /> <br />Figure 10,3 was developed using the results of the information provided in Section 5.1 that <br />discusses historic storm rainfall temporal and intensity distributions. PowerPoint slides from the <br />Final Report meeting provides additional curves used in the development of the Depth Duration <br />envelopment curve (see A W A response to Question 30.). <br /> <br />24. Page 124. Why is there an inflection point on the Depth Area envelopment curve at <br />approximately the drainage area ofthe Cherry Creek basin? <br /> <br />A W A response to Question 24, <br /> <br />Envelopment curves are drawn either through the data points with the maximum values or drawn <br />to create a smooth curve that produces larger values than the maximum values (see Envelopment <br />in the Final Report Glossary, page xviii). The maximum plotted values in Figure 10.3 are <br />provided by data values from the 1921 storm for large area sizes and by the 1935 A-center values <br />for smaller area sizes. The envelopment curve was drawn to provide a smooth transition from <br />the values at large area sizes to the values at smaller area sizes. This curve could be drawn as an <br />