Numerical Simulation of River Bed Deformation due to Unsteady Flow of Large Sand-Bed Braided River : Brahmaputra-Jamuna

Abstract

Numerous bars and channels are an essential large scale topographic feature of the braided river morphology. During the monsoon season, due to the unsteady change in hydrograph, these bars and channels experience simultaneous reworking which is quite uncertain. Through this study, we reproduced the river bed deformation due to unsteady flow which generally happens during the monsoon season using numerical simulation. Along with this, we tried to investigate some individual bar scale property as well as their interaction with the braided plain of a highly sediment-laden reach of Brahmaputra-Jamuna River. Our study indicates that the frequency of deposition on the river bed or braided plain was higher compared to the erosion due to the response of unsteady discharge and water level change in the study reach. Nevertheless, the development process of the braided bars is quite different from the bars of straight and meandering channels. The spatial growth of the bar seems to be dependent on the width-depth ratio up to a certain limit and finally, the migration rate of the bar recedes with the growth of the bar.