Flow Structure and Transport of Sand‐Grade Suspended Sediment around an Evolving Braid Bar, Jamuna River, Bangladesh

Detailed vertical profiles of time-averaged flow velocities and sediment concentration were taken during three periods of mid-channel bar development in the Jamuna River, Bangladesh. Bar growth was initiated downstream from a major flow convergence and generated a bar 4 km long and 1 km wide in a channel up to 15 m deep. Flow velocities and the concentrations of sand-grade suspended sediment were quantified using an acoustic Doppler current profiler (ADCP). Bed morphology was measured using echo-sounding and all positions were located using a differential global positioning system (DGPS). These data reveal no evidence for channel-scale, coherent helical flow cells in either distributary around the braid bar. Instead, the structure of flow is dominated by a simpler flow divergence over…