Control Point in a Lateral Spillway Channel

To calculate the water surface profile in a lateral spillway channel, it is necessary to determine a control point. The control may be located downstream, with subcritical flow everywhere in the channel; however, for conditions in which supercritical flow occurs, the determination of the control point presents some difficulties. A method for determining the location of a critical depth control point was proposed by Julian Hinds in 1926, using an equivalent critical depth channel. The method outlined in this paper is quicker than Hinds' method and more flexible in dealing with a number of different rates of discharge. The transitional profile technique of Escoffier has been extended to include an additional term, dependent on the rate of lateral inflow into the channel. The method is applicable to channels of uniform or nonuniform cross section. In the case of uniform channels the solution is rapid.