Validation of discharge prediction approaches in a straight compound channel

Abstract

The flow pattern of a compound channel becomes complicated due to the transfer of momentum between the main channel and the adjoining floodplains. Experiments are carried out to compute the velocity as well as boundary shear along the wetted perimeter of a straight compound channel to quantify the momentum transfer along the expected interfaces originating at the junction region between main channel and flood plain. This is helpful to evaluate the stage-discharge relationship for a compound channel accurately. Discharge calculation can be done by using various hydraulic models. But the traditional discharge prediction models such as SCM, DCM fail to give accurate discharge as they don’t consider the effect of momentum transfer. Therefore some new models are being developed which makes discharge prediction more accurate than the traditional method by considering the effect of momentum transfer. In this study the experimental data reported by other investigators as well as data from the present series of experiments are used through the hydraulic models such as DCM, IDCM, MDCM,CES to evaluate the discharge estimation and the results are compared with the experimental observations by keeping Manning’s n value constant with respect to the surface roughness. But apart from surface roughness Manning’s n is dependent upon many other factors such as depth of flow, shape of the channel, alignment of the channel etc.. So by varying the value of manning’s n with respect to depth of flow the discharge is being computed through MDCM and the percentage of error is found out. Modification to MDCM is applied for the variation of n values.