How is critical depth calculated for different channel sections?

Critical depth occurs when specific energy is minimum for given discharge, or Fr = 1. For rectangular section: yc = (Q^2/(gB^2))^(1/3) = (q^2/g)^(1/3), where q = unit discharge. For triangular: yc = (2Q^2/(gm^2))^(1/5), m = side slope. For general sections, solve: Q^2*T/(g*A^3) = 1, where T = top width. Critical slope maintains critical depth as normal depth. Critical depth is control point for flow calculations, occurring at free overfall, channel transitions, and minimum energy state.