Impact of Mean Velocity Accuracy on the Estimation of Rating Curves in Compound Channels

Abstract

The stage-discharge relationship in open channels plays a significant role in analyzing and designing the channels and hydraulic structures. Recently a new stage-discharge relationship is introduced (Maghrebi et al., 2017). The proposed relationship can be used in arbitrary shaped channels including compound channels, where the traditional formulations are not able to accurately estimate the discharge. In this study, the stage-discharge curves in 6 laboratory prismatic compound cross sections are calculated based on the proposed stage-discharge relationship. The mean velocity parameter appearing in this relationship can be substituted with any equivalent value. As an alternative, the mean extracted velocity using the SKM is used in the proposed relationship in order to produce the stage-discharge curves for the above mentioned cross sections. Then, the obtained results are compared with the ones of the proposed relationship. The accuracy of the two models is tested successfully against available experimental results, which are taken from the Flood Channel Facility (FCF) laboratory. Finally, the normalized root mean square error (NRMSE) and the mean absolute percentage error (MAPE) calculated based on the SKM method produced by the CES are within 0.61 and 10%, respectively. However, the corresponding calculated values based on application of mean velocity U extracted from the depth-averaged velocity Ud of the SKM do not exceed 0.23 and 4%, respectively, which shows a better agreement.