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<br />Table 4.--Qutline and example of procedures for determining n values <br />for a hypothetical channel and flood plain--Gontinued <br /> <br />SEX::TION 2--Gontinued <br /> <br />Channel Houghness (steps 3-13)--Continued <br /> <br />Step <br /> <br />Item to be determined or <br />operation to be performed <br /> <br />Factors on which decisions are <br />based and the results <br /> <br />8 <br /> <br />Adjustment factors <br />for segments <br /> <br />None. <br /> <br />9 <br /> <br />Basis for weighting n <br /> <br />Use wetted perimeter for basis of <br />weighting n for the channel <br />segments. <br /> <br />10 <br /> <br />Weighting factors and <br />weighted n <br /> <br />About 10 ft of the wetted peri- <br />meter is bounded by bedrock, about <br />30 ft by sand, and about 60 ft is <br />bounded by gravel and cobbles. <br />The unadjusted n value is (0.1 X <br />0.040 + 0.3 X 0.025 + 0.6 X <br />0.030)/1.0 = 0.030. <br /> <br />11 <br /> <br />Add adjustments for entire <br />channel <br /> <br />(1) Boulders at head of reach are <br />slight obstructions, add 0.002 <br />(table 2). <br /> <br />(2) The bend near the lower end of <br />reach A (fig. 23) causes slight <br />irregularity; add 0.002 (table 2). <br />n = (nb + nl + n2 + n3 + n4)m <br />n = (0.030+0.002+0+0.002+0)1.0 <br />n = 0.034. <br /> <br />12 Compare with other streams <br /> <br />None. <br /> <br />13 Check flow regime <br /> <br />Sufficient sand was not present to <br />warrant a check. <br /> <br />SEX::TION 3 <br /> <br />1 Extent of reach <br /> <br />From midway between sections 2 and <br />3 to one section width below <br />section 3. Designated as reach C <br />(fig. 23). <br /> <br />55 <br />