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<br />(7) Determine thunderstorm runoff curve <br />numbe.r and minimum retention loss rate. <br /> <br />From Step 3, thunderstormCN from Table <br />A-9, Appendix A, Page 544: CN = 75 <br /> <br />From Table A-lO, Appendix A, Page 544: Hydrologic <br />Soil Group "B", miniinum 15-.minute retention loss <br />rate - 0.06 inch/15 minutes, <br /> <br />(8) Direct runoff increments for computing <br />maximum probable flood (values in inches) <br /> <br />Time, <br />Ending Hr. <br /> <br />. ..' .,~-'i <br />,.,' j <br /><:-,:'>-.1 <br />.:'.1 <br /> <br />0.25 <br />0.50 <br />0.75 <br />1.00 <br />1.25 <br />1. 50 <br />1. 75 <br />2.00 <br />2.25 <br />2.50 <br />2.75 <br />3.00 <br /> <br />Incremental <br />Design <br />Rainfall <br /> <br />Accumulative <br />Design <br />Rainfall <br /> <br />Direct Runoff <br />Accumulative 1 Incremental <br /> <br />Incremental <br />Loss <br /> <br />1. 34 <br />1.90 <br />2.56 <br />5.36 <br />1.12 <br />0.78 <br />0.56 <br />0.44 <br />0.34 <br />0.28 <br />0.16 <br />O.ll <br /> <br />0.12 <br />1.00 <br />2.00 <br />4.88 <br />1.06 <br />0.72 <br />0.50 <br />0.38 <br />0.28 <br />0.20 <br />0.10 <br />0.05 <br /> <br />1.22 <br />0.90 <br />0.56 <br />0.48 <br />0.062 <br />0.06 <br />0.06 <br />0.06 <br />0.06 <br />0.08 <br />0.06 <br />0.06 <br /> <br />1.34 <br />3.24 <br />5.80 <br />11.16 <br />12.28 <br />13.06 <br />13.62 <br />14.06 <br />14.40 <br />14.68 <br />14.84 <br />14.95 <br /> <br />0.12 <br />1. 12 <br />3.12 <br />8.00 <br />9.10 <br />9.90 <br />10.40 <br />10.85 <br />ll.20 <br />11.40 <br />11.55 <br />11.65 <br /> <br />1 Using CN = 75, AMC 11 Fig. A-4, Appendix A, Page 541 & 542 <br />2 Computation by CN 7S gives 0.02 inch per IS-minutes. Abandon curve and <br />use 0.06 inch per IS-minutes for IS-minute storm increments. <br /> <br />- 10 - <br />