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<br />values for lower- and transitional-regime flows generally are much larger <br />than the values given in table 1 for upper regime flow. Simons, lee, and <br />Associates (1982), gave a range of n values commonly found for different <br />bed forms. <br /> <br />The values given in table 1 for sand channels are for upper-regime <br />flows and are based on extensive laboratory and field data obtained by <br />the U.S. Geological Survey. In using these values, a check must be made <br />(in the manner previously described) to ensure that the stream power is <br />large enough to produce upper-regime flow (fig. 1). Although the base n <br />values given in table 1 for stable channels are from verification studies, <br />the values have a wide range because the effects of bed roughness are <br />extremely difficult to separate from the effects of other roughness <br />factors. 'Ihe n values selected from table 1 will be influenced by <br />personal judgment and experience. <br /> <br /> 3 <br />ff) <br />0 <br />z <br />~ 2 <br />0 l- <br />n.. <br />, 0 <br />I- 0 <br />0 lL. <br />0 W <br />lL. a: <br />z <( <br /> ~ <br />~ 0 <br />> ff) <br />0. 0.8 <br />ff) a: <br />a: w <br />N n.. <br /><0 0 0.6 <br />~ <br /> z <br />a: 0 <br />w () <br />3: w <br />0 ff) 0.4 <br />n.. a: <br />:::;: w <br /><( n.. <br />w <br />a: <br />l- <br />ff) <br /> <br /> / ,/ <br /> / <br /> Upper regime / <br /> / Transition <br /> /' <br /> / - <br /> / ~ - <br /> ---- <br /> / .- ......... <br /> V ./ <br />~ V Lower regime <br /> <br />0.2 <br />o <br /> <br />0.6 <br /> <br />0.8 <br /> <br />1.2 <br /> <br />0.2 <br /> <br />0.4 <br /> <br />MEDIAN GRAIN SIZE, IN MilLIMETERS <br /> <br />Figure l.--Relation of stream power and median grain size to flow regime. <br /> <br />6 <br />