Chézy formula

The Chézy formula estimates mean flow velocity in an open channel as the Chézy coefficient times the square root of hydraulic radius multiplied by channel slope.

Chézy coefficient: A resistance coefficient in the Chézy formula that relates mean flow velocity to hydraulic radius and slope. It sets how strongly channel conditions translate the formula’s geometric and slope terms into velocity.
Wetted perimeter: The length of a channel boundary in contact with flowing water. It combines with cross-sectional area to determine the formula’s hydraulic radius.
Antoine Chézy: An eighteenth-century French engineer who developed an equation for open-channel flow velocity. His name is attached to the formula and its early engineering use.
Channel roughness: The resistance to flow caused by irregularities on a channel’s boundary. Boundary roughness strongly influences the coefficient needed for useful velocity estimates.
Hydraulic radius: The cross-sectional area of flowing water divided by the wetted perimeter of the channel. This geometry term represents the channel’s flow area relative to its contact with boundaries.
Cross-sectional area: The area of a plane figure formed by cutting across a three-dimensional object. For a channel, this area measures the water section used in hydraulic radius.
Canal de l’Yvette: An eighteenth-century French waterway project associated with Antoine Chézy’s hydraulic investigations. The formula arose from Chézy’s work estimating flow in a planned canal.
Uniform open-channel flow: Open-channel flow with constant depth and velocity along a reach. This is the standard setting in which the formula is applied.
Channel slope: The rate of elevation change along a channel’s length. The formula’s slope term represents the gravitational driving force along the channel.
Manning formula: An empirical open-channel equation that estimates mean velocity from hydraulic radius, slope, and roughness. It offers a widely used alternative with roughness represented by Manning’s coefficient.

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