Author(s)

K. K. Khatua, K. C. Patra, S. Behera & P. K. Mohanty

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. Keywords: apparent shear, main channel, floodplain, compound channel, discharge estimation, interface planes. 1 Introduction During floods, a part of the river discharge is carried by the main channel and the rest is carried by the floodplains. Momentum transfer between the flow of deep main channel and shallow floodplain takes place making the discharge prediction in compound channel more difficult. In the laboratory the mechanism of momentum transfer between the channel section and floodplain was first investigated and demonstrated by Zheleznyakov [30] and Sellin [24].

Keywords

apparent shear, main channel, floodplain, compound channel, discharge estimation, interface planes