Kutter's formula

A formula for evaluating the coefficient, C, in the following Chezy formula for the mean velocity of the current in a stream.

$v=C{\sqrt {rs}}$

where

$v$ = velocity in feet per second

$C$ = a coefficient

$C={\frac {41.6+{\frac {1.811}{n}}+{\frac {0.00281}{s}}}{1+(41.6+{\frac {0.00281}{s}}){\frac {n}{\sqrt {r}}})}}$

$r$ = hydraulic radius

$s$ = sine of slope

and $n$ = coefficient of roughness