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<br />I <br />- -----~: <br />I <br />1 <br />~ <br />----' <br />~ <br /> <br />, <br />I.. <br /> <br />will pennit a rating curve to be developed. <br />If the required location for the rating curve is in a long <br />straight reach of the river, a procedure known as the slope-area <br />method will give satisfactory results. The key to successful ap- <br />pl ication of the slope area method is to supply the proper slope <br />data. Before accepting the calculated rating curve, use it to cal- <br />culate water surface profiles for a range of discharges and plot <br />these profiles along with channel bed. top bank. etc. They should <br />all be about parallel to the average slope of the channel in this <br />location. If this test fails, the calculations and data used in <br />slope-area method should be re-evaluated or, perhaps. a better site <br />should be selected for establishing the curve. <br /> <br />Section 5.04. Geometric Properties and Conveyance <br /> <br />': <br /> <br />Geometric properties required for profile calculation are cross <br />sectional area. wetted perimeter and hydraulic radius. These properties <br />can be determined directly from the cross section once the water surface <br />elevation has been specified. In some cases these data are calculated <br />for a range of elevations and tabulated or plotted in graphical form <br />before the water surface profile calculations begin. In all cases <br />a horizontal water surface elevation is assumed. The procedure is <br />illustrated in figure 5.03 for one water surface elevation. Equations <br /> <br />, <br />, <br />, <br />, <br />, <br />" <br /> <br />for area. wetted perimeter and hydraulic radius are shown on the figure. <br />Calculations are made for each subsection in the cross section in a <br />similar manner. Subsection values are saved for use in calculating total <br /> <br />area and conveyance for the cross section. <br /> <br />5.01 <br />