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supercritical velocities are not recommended. Curve <br />radii should be sufficiently great to limit supereleva- <br />tion of the water surface to one foot above computed <br />depth of flow or 107a of water surface width, which- <br />ever is the least. The amount of superelevation for <br />simple curves may be determined as follows: <br />1. Trapezoidal Channels: <br />Subcritical velocity: <br />e =V2b +2zd) <br />(g R -2zV 2) <br />2. Rectangular Channel: <br />Subcritical velocity: <br />e =V26 <br />gR <br />Supercritical velocity: <br />e = 2V2 <br />gR <br />Supercritical velocity — compound curve: <br />e c Y b <br />gR <br />The compound curve is a simple curve of <br />radius R preceeded and followed by a section <br />of simple curve with radius of 2R, and length <br />of b , where sin B = �m <br />ton B V <br />Where: e = maximum difference in elevation <br />of water surface between channel <br />sides (ft) <br />z = Co- tangent of bank slope <br />d = normal depth (ft) <br />b = channel bottom width (ft) <br />R = radius of curve to centerline (ft) <br />g = acceleration due to gravity (fps2) <br />V = normal velocity (fps) <br />dm =mean depth <br />11 <br />P <br />.i <br />l <br />WS <br />i .. <br />' b <br />Water: Surface Superelevation <br />Showing, "e <br />A. <br />11 <br />P <br />.i <br />l <br />