In 1897, when considering flow in open channels, H. E. Bazin (1829–1917) proposed that the Chezy discharge coefficient (C) could be related to the hydraulic radius (r) and a channel roughness coefficient (k1) by the formula: C = 157.6/[1 + (k1/r1/2)]. Other more complex formulae have also been proposed. See chezy’s formula.