Manning formula


The Manning formula is also known as the Gauckler–Manning formula, or Gauckler–Manning–Strickler formula in Europe. In the United States, in practice, it is very frequently called simply Manning’s Equation. The Manning formula is an empirical formula estimating the average velocity of a liquid flowing in a conduit that does not completely enclose the liquid, i.e., open channel flow. All flow in so-called open channels is driven by gravity.

Related formulas


VCross-sectional average velocity (in m/s) (dimensionless)
kConversion factor (1 for SI units system , k=1.49 for English units) (dimensionless)
SThe linear hydraulic head loss ( the same as the channel bed slope when the water depth is constant) (dimensionless)
ACross sectional area of flow (in m^2) (dimensionless)
PWetted perimeter of cross-sectional flow area (in m) (dimensionless)
nGauckler–Manning coefficient (in s/m^1/3) (dimensionless)