Apparent shear stress and boundary shear distribution in a compound channel flow

Abstract

The flow structure in any compound channel is a complicated process due to the transfer of momentum between the deep main channel section and the adjoining shallow floodplains. The boundary shear stress distribution in the main channel and floodplain greatly affects the momentum transfer. In the present work, the shear stress distributions across an assumed interface plane originating from the junction between the main channel and flood plain using the Divided Channel Method (DCM) are analyzed and tested for different compound channels and their flow conditions using global data. An improved equation to predict the boundary shear distribution in compound channels for different width ratios is derived that gives better results than other proposed models. Analyses are also done to suitably choose an appropriate interface plane for evaluation of stagedischarge relationship for compound channels having equal roughness in the channel beds and walls. The effectiveness of predicting the stage-discharge relationship using the apparent shear stress equation and boundary shear distribution models are discussed.