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<br />32.8--1 <br /> <br />WATER INFORMATION MANAGEMENT SYSTEM HANDBOOK <br /> <br />B. ~Y-2. Using either field measurements of discharge or <br />hydraulic geometry relations (or cross-sectional area data) with <br />the stage-discharge curve from the representative gage station, <br />determine the discharge at the bankfull (OB) stage for the <br />representative gage station. <br /> <br />C. ~-1. Calculate or measure bankfull discharge for all <br />suitable gage stations using channel width vs. discharge, water <br />stage vs. discharge, or field measurements. <br /> <br />D. Step 4. Calculate drainage area, area-weighted mean <br />elevation or other appropriate variables for regression with <br />bankfull discharge (0 ) for the points of quantification. <br />Other variables such ~s precipitation may be more appropriate in <br />some areas. If such is the case, measure those variables for <br />both the gage station watersheds and for the watersheds above <br />the points of quantification. <br /> <br />E. Stee 5. Develop general relationship. Regress the bankfull <br />discharge values (0 ) from Steps 2 and 3 against the drainage <br />areas (or other app~opriate variables) of representative and all <br />suitable gage stations using watersheds in similar area-weighted <br />mean elevation zones to develop a relationship of the following <br />form. <br /> <br />where, <br /> <br />OB = f(DA) <br /> <br />o = bankfull discharge and <br />f(DA' = some functional relationship of drainage area. <br /> <br />Note: Develop this relationship for as many elevation zones as <br />chosen. Alternatively, if the data are not stratified by <br />elevation zones, develop a relationship of the form OB = <br />f(DA,E), where E = elevation. <br /> <br />F. Stee 6. Calculate bankfull discharge (OB) for points of <br />quantification using the relation developed ~n Step 5. <br /> <br />G. Stee 7. Proceed to Section 32.8. Do Common Steps 1, 2 <br />(part 1), 8, 9, 10 (OB only), and 11 (OB only). <br /> <br />3Z~ - Common Stees. The following steps (exhibit 1) are common <br />to all the methods described. These must be completed after the <br />results of the selected method are in hand. <br /> <br />A. Common Stee-1. Normalize and plot the representative gage <br />station flow-duration curve (exhibit 2). <br /> <br />*-FSH 4/89 AMEND 3-* <br />