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<br />001u71 <br /> <br />32.5--1 <br /> <br />WATER INFORMATION MANAGEMENT SYSTEM HANDBOOK <br /> <br />followed in field determinations. Avoid areas such as beaver dams, road <br />encroachments, bedrock or braided reaches, meander benches, debris jams and <br />other channel modifications or features which limit the channel's ability <br />to adjust. The value used is an average of at least three measurements <br />along uniform stream reaches. <br /> <br />Step 4 - Calculate or measure bankfull discharges for all suitable gage <br />stations. Using channel width vs. discharge, water stage vs. discharge, or <br />field measurement of discharge, calculate or measure bankfull discharge for <br />all suitable gage stations. <br /> <br />Step 5 - Develop general relation. Using the data from the representative <br />station and all suitable stations regress the measured active channel <br />bankfull width (Step 3) against bankfull discharge (Steps 2 and 4). The <br />resulting equation is of the form: <br /> <br />QB . aWR <br /> <br />t'. <br />\ <br /> <br />where: <br />QB . bankfull discharge in cfs <br />WB . width in feet <br />a and b - coefficient and exponent. <br /> <br />Step 6 - Measure bankfull width (Ws) at each point of quantification <br />using the procedures described in Appendix C. Using the relation developed <br />in Step 5 calculate bankfull discharge (Qs). <br /> <br />Step 7 - Proceed to Sec. 32.8, Common Step 1. <br /> <br />32.5 - Method C. Use this method in those situations where the points of <br />quantification cannot be visited to measure either cross-sectional area and <br />slope or bankfull width. While drainage area and area-weighted mean <br />elevation are described as the required variables, other choices such as <br />precipitation may be appropriate in some areas. Such other variables may <br />either replace or supplement the two described. <br /> <br />S~~p 1 - Secure the following data from the representative gage station and <br />a suitable gage station records: <br />a. Channel width vs. discharge or stage vs. discharge relations. <br />b. Drainage area of watershed above gage. <br />c. Area-weighted mean elevation of watershed above gage. <br /> <br />Secure for the representative gage station the following: <br />d. Duration table of daily values summary for period of record. <br />e. Mean annual discharge. <br />f. Daily meaQ hydro graph data for the period of record. <br /> <br />10 No. 1 <br />9/10/85 <br />