Determination of Manning's N from vertical‐velocity curves

Professor M. P. O'Brien [see 1, 2 of “References” at end of paper] has recently shown that data on the vertical distribution of velocity through the theory of turbulent flow as developed by Prandtl, Von Karman, and others may be applied to the determination of friction‐coefficients in open channels. Hydrographers in making measurements of river‐flow have often noticed that in streams having rough bottoms appreciable difference is generally found between the measured velocity at 0.2‐ and 0.8‐depth. It is satisfying to note that Professor O'Brien's calculations are in accord with these general observations.