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-t- <br />r~ <br />APPENDIX III <br />DESIGN COtSPUTATIONS FOR UPPER EASIN DIVERSION CHANNEL <br />Reference• <br />V. T. Chow <br />1959. Open Channel Hydraulics. McGraw-Hill Book Co., Inc. <br />New .York, N. Y. <br />INTRODUCTION <br />Design of the L'pper Basin diversion channel is based on the <br />"retardance coefficient" concept for grassed channels. The retardance <br />coefficient (n) maintains a unique relationship with the product of the <br />mean flow velocity (v) and the hydraulic radius (R). The relationship <br />• is characteristic of the vegetation and is essentially independent of <br />charnel slope and shape. The n - vR curves developed by the U.S. Soil <br />Conservation Service and presented in Chow (1959), are the basis for the <br />calculations below. The design is also based on the concept of "permissible <br />velocity", which is the velocity that will prevent excessive erosion for <br />long periods of time. The specific design procedure is given on pages <br />1S6 and 187 of Chow (1959). It should be noted that because the basis <br />for design of the channel cross-section is a Probable Maximum Flood, a <br />permissible velocity perhaps 15 percent greater than that reco~::rended eras <br />assumed. The low-flow channel shown in Figure 5 (text) is provided in <br />addition to the required cross-section for the PMF. <br /> <br />