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The Rational Method of storm runff calculation was used ~ <br /> throughout. In calculating peak runoffs for the individual ~~ <br />,~ <br />~ <br /> areas the rainfall intensity for a storm duration equal to <br /> the time of concentration for that area and having a storm <br /> occurance frequerncy of ten (10) years was used. All <br /> formulas and coefficients for calculating surface runoff <br /> came from Haan and Barfield. Open channel flows were <br /> calculated with Mannings Equation. All culverts were <br /> designed to run open so no additional structures would be <br /> necessary to provide head to the pipes. Total volume of <br /> runoff was calculated using the rainfall intensity of a 10- <br /> year-24-hour storm event predicted for this area. The <br /> intensity for ;all areas near and around Stonewall, and <br /> Weston, Colorado, Ss 3.0 inches of rainfall for the 10-year- , <br />C 24-hour event. Weather Bureau Technical Paper No. 40, <br /> Rainfall Frequency Atlas of the United States was the source <br /> of climatalogical data for rainfall intensities for the <br /> Weston, Colorado, area. Its guidelines were used in <br /> estimating storm intensities for storm durations not <br /> specifically det:ailed in the publication. As runoff from <br /> different areas reports to a given channel, the total of the <br /> peak runoff ,flows is used as the design flow for the <br /> channel. Rather than recalculating a new, longer, <br /> saturation period and lesser flow, this calculation yields a <br /> simpler and more conservative design. <br /> <br />8 <br /> <br />