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<br />I <br />II <br /> <br />I~I <br />Iii <br />------ <br />A. <br />I <br />:1 <br />,I <br />II <br />I <br />il <br />il <br />II <br />I <br />, <br />" <br />I <br />, <br />I <br />IJ <br /> <br />~ <br /> <br />PART IV <br /> <br />DESIGN CRITERIA <br /> <br />nppn Channels <br />----- <br /> <br />The basic equation to--be used for the analysis of open <br />channel flow is the Manning Formula: <br /> <br />Q = ~486 <br />n <br /> <br />AR2/3 S 1/2 <br />o <br /> <br />where: <br /> <br />Q = discharge, cubic feet per second (cfs) <br /> <br />n = roughness coefficient <br /> <br />A = cross-sectional area of flow, square feet <br /> <br />R = hydraulic radius, A/P, feet <br /> <br />P = wetted perimeter, feet <br /> <br />50= energy gradeline slope, feet/foot; parallel to <br />channel bottom slope for uniform flow conditions <br /> <br />For a given flow, Q, and cross-sectional area, A, the <br />velocity in the section is defined as: <br /> <br />V = 2 <br />A <br /> <br />where: <br /> <br />V = velocity, feet per second <br /> <br />Values of the roughness coefficient, <br />design are listed in Table IV-I. <br /> <br />On", to be used for <br /> <br />The Froude number is a dimensionless parameter which <br />defines the ratio of inertial forces to gravity forces for <br />flow in open channels. This value may be calculated for channels <br />with small slope angles with the equation: <br /> <br />F = <br /> <br />V <br /> <br />where: <br /> <br />f9D <br /> <br />33 <br />