Boundary shear distribution in a compound channel with differential roughness

Abstract

This paper demonstrates the influence of differential roughness on the boundary shear distribution for compound open channels. A mathematical relationship is derived between the percentage shear force carried by floodplains and five non-dimensional parameters (width ratio, relative flow depth, relative roughness, Reynolds number and Froude number). A procedure for assessing the flow distribution in terms of zonal boundary shear distribution and momentum transfer coefficients at the junction of a compound channel is presented. The efficiency of the model was tested by comparisons with published datasets and large experimental flood channel facility datasets. Compared with other standard approaches, the proposed method provided the least error in the predictions of both boundary shear and flow. The approach was also verified using actual river data and was found to provide good predictions in real-world applications.