Laboratory experimental study on applicability of bed load transport rate formula in Yangtze River estuary

At present, there are many formulas for calculating the bed load transport rate in the Yangtze River estuary, but research on the applicability of these formulas remains limited.In this paper, undisturbed sediment samples with a median particle size of 0.161 mm were selected in the south channel of the Yangtze River estuary, and the bed sediment transport experiments under the action of steady and unsteady flow were carried out, as well as the applicability of different bed sediment transport rate formulas was analyzed.The experimental results showed that the Shields number θ of the simulated water flow intensity was between 0.04 and 0.54, and the bed sediment transport rate was between 0.000 03 and 0.1 kg/(m·s), which was equivalent to the measured bed sediment transport rate in the south channel of Yangtze River estuary.With the linear increasing or decreasing of the flow force in the flume, the measured bed sediment transport showed an obvious exponential variation process.The calculation results of different bed sediment transport rate formulas were compared with the results of laboratory experiments and field observations, and it was preliminarily confirmed that SHEN Qi formula and MENG Zhen formula had good applicability in calculating the bed sediment transport rate.It was suggested that the steady sediment transport method with a step time step of no more than 200 s should be used to invert the change of bed sediment transport under unsteady flow in estuaries.These findings provide valuable insights for bedload transport modeling and sediment dynamics research in the Yangtze River Estuary.