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<br />In general practice, one n value is selected for the entire range <br /> <br />of depth of flow. If the ratio of the depth of flow to the size of the <br /> <br />roughness element (relative smoothness) is low, roughness is not con- <br /> <br />stant. Most relations betweeen roughness and depth of flow are too <br /> <br />technical for general use and often involve parameters that are not <br /> <br />usually measured onsite. On steep-gradient streams (for the purpose of <br /> <br />00 <br />this study, slope greater than 0.2 ~eree~t), channel roughness can vary <br />A <br /> <br />markedly with depth of flow. <br /> <br />Because of the lack of a satisfactory quantitative procedure, the <br /> <br />ability to evaluate roughness characteristics for the different condi- <br /> <br />tions in urban and agricultural channels and flood plains must be <br /> <br />developed through experience and an appl ication of the above method for <br /> <br />natural channels. Amore detailed description of practical techniques <br /> <br />I <br /> <br /> <br />to evaluate the roughness coefficient of agricultural and urban channels <br /> <br />and flood plains can be found in Chow (1959), Arcement (in press), Hejl <br />(1977), Reeand Palmer (1949), and Jarrett and Stanton (in press). <br /> <br />/3 <br />