A canal with rectangular cross-section of width b is carrying a uniform flow of depth h. For this fcanal, if Chezy’s coefficient is C and Manning’s roughness coefficient is n, the product ‘Cn’ is given by
1
(2b + h)2/3
2
(b + 2h)2/3
3
\({\left( {\frac{{{\rm{bh}}}}{{{\rm{b}} + 2{\rm{h}}}}} \right)^{1/6}}\)
4
\({\left( {\frac{{{\rm{bh}}}}{{{2\rm{b}} + {\rm{h}}}}} \right)^{1/3}}\)