Proper sizing of a channel, whatever its shape depends on the knowledge and mastering of the varied flow that occurs in it. This is, in particular, the case of the triangular channel on which the present study is focused. In the field of gradually varying flow, previous studies have mainly focused on rectangular channels. Very few studies have been carried out on other profiles, in particular the triangular profile. The differential equation that governs the gradually varied flow is transformed into a dimensionless generalized equation using a rigorous theoretical approach. Carefully applied to the triangular channel, it was possible to plot dimensionless backwater and drawdown curves for the special cases corresponding to zero and critical slopes