# Chézy formula

{{ safesubst:#invoke:Unsubst||$N=Refimprove |date=__DATE__ |$B= {{#invoke:Message box|ambox}} }} In fluid dynamics, the Chézy formula describes the mean flow velocity of steady, turbulent open channel flow:

${\displaystyle v=C{\sqrt {R\,i}},\,}$

where

The formula is named after Antoine de Chézy, the French hydraulics engineer who devised it in 1775.

## Usage with Manning coefficient

This formula can also be used with Manning's Roughness Coefficient, instead of Chézy's coefficient. Manning derived[1] the following relation to C based upon experiments:

${\displaystyle C={\frac {1}{n}}R^{1/6}}$

where

Unlike the Manning equation, which is empirical, the Chézy equation is derived from hydrodynamics theory.[2]