Stage-Discharge Prediction in Compound Channels

The failure of conventional methods for discharge prediction in compound channels results from their ignorance of the loss in conveyance arising from the complicated flow interaction between the main channel and its associated floodplains. In this paper, a new method is presented for assessing the stage-discharge relationship and the discharge distribution in compound channels by considering both the momentum transfer between the upper and lower main channel flows and that between the upper main channel and its adjoining floodplain flows. A calibration using data from the laboratory channels and three natural rivers demonstrates that the presented method can give predictions that agree better with the experimental and field data. The computed results also show that the method not only is well capable of predicting the discharge distributions of the floodplain and the whole main channel, but also of predicting the discharge distribution in the lower main channel. In addition, the momentum transfer coefficient introduced in the presented method is also further discussed.