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<br />Studies have shown that many factors influence flow resistance. <br /> <br />Chow (1959), Fasken (1963), Aldridge and Garrett (1973), and Jarrett and <br /> <br />Stanton (in press) expanded on a practical technique developed by Cowan <br /> <br />(1956) to aid in evaluating the total flow resistance in a channel <br /> <br />reach. By th i s procedure, the va I ue of to ta I f I ow res i stance is com- <br /> <br />puted for a selected depth of flow by: <br /> <br />where: <br /> <br />nT = (n+n,+n2+n3+n4)m <br /> <br />nT is the total flow resistance in a channel reach; <br />n is a base value for a straight, uniform. smooth channel and <br /> <br />depends only On the particle size of the bed material; <br /> <br /> <br />n, is a value added to n to correctr~~ for cross-section <br />\I <br /> <br />irregularities; <br /> <br />^ <br />n2 is a correc~ion <br /> <br />(size and shape); <br />. 1". <br />n3 I s a correc\) on <br /> <br />. ". <br />n4 I s a correctvlon <br /> <br />and. <br /> <br />factor for the effect of channel variations <br /> <br />factor for the effect of obstructions; <br /> <br />/ <br />factor for the effect of channel vegetation; <br /> <br />m is a correction factor for a meandering channel. See Chow ('959. <br /> <br />(5) <br /> <br />table 5-5. p. '09) for the adjustment values to be applied to equation 5. <br /> <br />/f <br /> <br />.--- <br /> <br />r? <br />'=' <br />~ <br /> <br />~ <br /> <br />.~ <br /> <br />...-:-- <br /> <br />~ <br /> <br /><e- <br />