where /i = flow depth; u — flow velocity in the x-direction; u = flow ve-it»iiy iii iiio -direction; 9 = acceleration due to gravity; ,3 = channel bot-tom slope in the x-direction; St = channel bottom slope in the y-direction; and Sk, and St are the slopes of the energy grade lines in the x- and y-di- rections, respectively, computed using the steady state friction formulas