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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />HYDROLOGIC ANALYSIS <br /> <br />Hydrologic analysis of the study area was performed to determine flood hydrographs <br />for the 2-, 5-, 10-, 25-, 50-, and 100-year recurrent storms for all study reaches. All <br />runoff hydrographs are based on future basin development, assuming fully developed <br />conditions. <br /> <br />Rainfall Data <br />Flood hydrographs have been derived by routing runoff from design rainfall through <br />the channel system of Little Dry Creek. Design rainfall values for the 2-, 5-, 10-, 25-, 50- <br />and 100-year return period have been derived from the "Precipitation-Frequency Atlas of <br />the Western United States, Vol. III, Colorado" published by the National Weather Service <br />and areally reduced according to Weather Service Procedures described in the Atlas. <br />Rainfall values adjusted for the Little Dry Creek Basin are listed in Table 1. A two-hour <br />design storm was used in the development of flood hydrographs for this study. The <br />hyetograph for the 100-year storm is shown in Figure 5. <br /> <br /> TABLE 1 <br /> RAINFALL VALUES <br /> (total inches) <br />Duration (hours) 1 2 3 6 24 <br />Recurrence Interval <br />2 year 0.93 1.14 1.29 1.52 2.10 <br />5 year 1.28 1.54 1. 72 2.00 2.77 <br />10 year 1.55 1.84 2.05 2.37 3.27 <br />25 year 1.90 2.23 2.49 2.86 3.93 <br />50 year 2.17 2.54 2.82 3.23 4.44 <br />100 year 2.44 2.84 3.15 3.60 4.94 <br /> <br />- 6-. <br />