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<br />. <br /> <br />. <br /> <br />. <br /> <br />DRAINAGE CRITERIA MANUAL <br /> <br />RUNOFF <br /> <br />B = KC = (.2 x .71) = 0.142 <br /> <br />C = 1 - (1-C1) ~t/B = 1 - (1_.71).083/.142 = 0.52 <br /> <br />Step 11. Set up Equation 4-7 and enter coefficients in Table 4-c <br />for Reach B-C. <br /> <br />O2 = (1-.52)01 + (.52)11 = (0.48)01 + (.52)11 <br /> <br />Step 12. Repeat Step 5 for Reach B-c. Use Outflow from Reach A-B as <br />Inflow into Reach B-C. <br /> <br />The routed outflow is the hydrograph at point C on the water- <br />course. <br /> <br />4.13.5 Comparison of Routing Examples <br />Examining Tables 4-4 and 4-6 reveal the following at point C: <br /> <br />Method Peak Flow Time to Peak Volume <br /> (cfs) (minutes) (ac ft) <br />Di rect 272 75 28.2 <br />Convex 285 60 28.2 <br /> <br />For the drainageways and hydrographs used in Examples 2 and 3 the Direct <br />Trans 1 ati on Routi ng gave a 5% 1 esser peakfl ow at poi nt C than the Convex <br />Routing Method. The time to peak was greater for the Direct Translation <br />Routing example. The volumes were identical for both methods and indicate <br />that the law of mass conservation applies to both. Although the peaks are not <br />identical, they are within the accuracy of these type of calculations. <br />However, under a different set of hydrographs and channel conditions, these <br />two routing methods may have given different relative results and the <br />resultant peaks may have been more than 5% apart. <br /> <br />Routing calculations involve considerable judgement and are sensitive to <br />hydrograph shapes and waterway conditions. It is important to recognize that <br />different routing methods will not give identical results, even when using <br /> <br />5-1-84 <br />