Based on the results of a first study, the present investigation considers discharge characteristics of a local, discontinuous contraction in a rectangular channel for submerged flow conditions. The theoretical approach analyses the separation zone as well as the local head-loss along the contraction by accounting for the contraction ratio, the inlet angle and the relative contraction length. General solutions are obtained by a matching procedure, and design relations are established. The results are compared with observations, and a good agreement is found.