Stage-Discharge Prediction for Converging Compound Channels with Narrow Floodplains

Momentum transfer between a main channel and side floodplains tends to increase the floodplain shear and decrease the main channel shear. The increase and decrease in shear are greatly influenced when a compound channel has nonprismatic floodplains. In converging compound channels, water flow on the floodplain crosses over water flow in the main channel, resulting in increased interactions and momentum exchanges. An experimental analysis concerning the distribution of shear stress in the main channel and the floodplain for both prismatic and nonprismatic compound channels under different overbank flow conditions are performed. New equations are developed for predicting boundary shear stress distribution for a compound channel with the nonprismatic flood plain. Using these expressions the stage-discharge relationships for both prismatic and nonprismatic compound channels of lower width ratios are successfully estimated. The efficiency of the models is verified by applying natural river data sets.