General Introduction: Since Chezy first proposed his well known equation for uniform flow in open channels, many other formulae have been suggested, either to replace the Chezy expression or form determining the value of the coefficient C.
Perhaps the major objection to the use of these formulae is that no account is taken of the variation of the boundary effects with Reynolds number — although in some cases this is done indirectly by relating Chezy’s C to the hydraulic mean radius.
Following more recent work, notably by Prandtl, there have been attempts to produce relationships between Chezy’s C, Reynolds number and a roughness parameter, (similar to those which exist for pipe flow) but these habe not been generally applied as the effects of the free surface and unsymmetrical flow conditions have not yet been fully evaluated.