In fluid dynamics, the Chézy formula describes the mean flow velocity of steady, turbulent open channel flow :
where
The formula is named after Antoine de Chézy, the French hydraulics engineer who devised it in 1775.
This formula can also be used with Manning's Roughness Coefficient, instead of Chézy's coefficient. Manning derived the following relation to C based upon experiments:
where
Both formulae are empirical, but the Manning formula is widely accepted as more accurate and is the base formula still in current use for all open channel flow analysis.