Manning Equation for Open-Channel Flow: Formula and Worked Examples

Plant drainage ditch and partially full gravity pipe with highlighted wetted perimeters

Manning’s equation estimates average velocity and discharge in steady, uniform open-channel flow. The calculation requires the flow area, wetted perimeter, hydraulic radius, energy slope, and Manning roughness coefficient. The equation is useful for preliminary hydraulic checks, but its assumptions must be verified before the result is used for design. This article was technically reviewed on … Read more