The purpose of this study is to compare the existing methods of calculating the backwater due to, or discharge through, a constriction in an open channel, and to show how these methods are but particular expressions of a more general submerged flow equation. An extensive literature review has been made describing the analyses leading to the current methods of computation. The application of these methods of computation has been described. The derivation and application of the submerged flow equation to these methods has also been described. Application of the submerged flow equation, as presented in this work, is considerably simpler than previous methods. Also, more accurate results were obtained when the equation was applied to data collected from model studies. However, the submerged flow analysis has not been proven in prototype application.