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0,. At' ~.,...,,, i.l tv ,_ 32.5--1 WATER INFORMATION MANAGEMENT SYSTEM HANDBOOK C. ~~-3. Measure bankfull width at the representative gage station and all suitable gage stations. Procedures for measuring bankfull width are presented in section 36.3. It is imperative that these guidelines be followed in field determina- tions. Avoid areas such as beaver dams, road encroachments, bedrock or braided reaches, meander benches, debris jams and other channel modifications or features which limit the channel's ability to adjust. The value used is an average of at least three measurements along uniform stream reaches. D. Step 4. Calculate or measure bankfull discharges for all suitable gage stations. Using channel width vs. discharge, water stage vs. discharge, or field measurement of discharge, calculate or measure bankfull discharge for all suitable gage s ta t ion s. E. Stec ~. Develop general relation. Using the data from the representative station and all suitable stations regress the measured active channel bankfull width (Step 3) against bankfull discharge (Steps 2 and 4). The resulting equation is of the form: b QB = aW B where, QB = WQ ~ b = bankfull discharge width in feet, coefficient, and exponent. . in'cfs, F. Stec 6. Measure bankfull width (W ) at each point of quantification using the procedures de~cribed in Section 36.3. Using the relation developed in Step 5 calculate bankfull discharge (QB)' G. Stec 7. Proceed to Section 32.8, A. Common Step 1. ~. - Method C. Use this method in those situations where the points of quantification cannot be visited to measure either cross-sectional area and slope or bankfull width. While drainage area and area-weighted mean elevation are described as the required variables, other choices such as precipitation may' be appropriate in some areas. Such other variables may either replace or supplement the two described. *-FSH 4/89 AMEND 3-*