Estimating Discharge from Superelevation in Bends

A method is presented for estimating open channel discharge from the maximum superelevation measured in the bends. It was based on data assembled from a dozen sources, representing about 70 separate experiments in the subcritical flow regime, and including information on channels of different cross-sectional shapes, included angles, and curvature ratios. The resulting predictive equation includes the effects of curvature ratio, included angle, and superelevation on discharge. The method was applied to a single flow event on Buffalo Creek, N.Y. It was found that only curves in which the flow remained in-bank could be used to predict discharge and that superelevations of less than 0.25 ft (7.6 cm) had to be excluded. The probable error of the Buffalo Creek analysis was 8% with respect to the mean of the discharges predicted from individual curves, while the data upon which the method was based had a probable error of 12%.