Uniform Open Channel Water Flow Rate Calculation with the Manning Equation

Water flow rate calculations for uniform open channel flow are typically made with the Manning equation. The Manning equation gives an empirical relationship among the open channel water flow rate; the channel slope, hydraulic radius and Manning roughness coefficient; and the cross-sectional area of flow. The Manning equation is given for U.S. units and for S.I. units. The parameters in the Manning equation must be in the specific units given, depending upon whether the calculations will be in U.S. or in S.I. units.