text: The Gauckler–Manning formula states:
  where:
  *  is the cross-sectional average velocity (L/T; ft/s, m/s);
  *  is the Gauckler–Manning coefficient. Units of  are often omitted, however  is not dimensionless, having units of: (T/[L]; s/[m]). 
  *  is the hydraulic radius (L; ft, m);
  *  is the stream slope or hydraulic gradient, the linear hydraulic head loss loss (L/L); it is the same as the channel bed slope when the water depth is constant. ().
  *  is a conversion factor between SI and English units. It can be left off, as long as you make sure to note and correct the units in the  term. If you leave  in the traditional SI units,  is just the dimensional analysis to convert to English.  for SI units, and  for English units. (Note: (1 m)/s = (3.2808399 ft)/s = 1.4859 ft/s)
  NOTE:  strickler = 1/ manning.  The coefficient  strickler varies from 20 (rough stone and rough surface) to 80 m/s (smooth concrete and cast iron).
  The discharge formula, , can be used to rewrite Gauckler–Manning's equation by substitution for .  Solving for  then allows an estimate of the volumetric flow rate (discharge) without knowing the limiting or actual flow velocity.
  The formula can be obtained by use of dimensional analysis. In the 2000s this formula was derived theoretically using the phenomenological theory of turbulence.