Observational study on bedload transport at the South Passage of Yangtze Estuary

In order to address the issue of lacking measured data on bedload transport at the Yangtze Estuary and study the features of bedload transport at the South Passage, a sediment observation system based on the pit-measuring method was developed for the Yangtze Estuary hydrodynamic environment, which has obtained reliable data on the bedload transport process at the mouth bar of South Passage under low disturbance. The results showed that the bedload transport rate was closely related to the flow velocity. The measured average bedload transport rate during the tide (3.3-meter average tidal range) was 0.007 kg/(m∙s), while the maximum bedload transport rate generally occurred at the time of maximum flood, which was 0.045 kg/(m∙s), and the maximum bedload transport rate at maximum ebb was 0.020 kg/(m∙s). On the same flow velocity conditions, there were some differences in bedload transport rate, that is, the bedload transport rate during flood tide was generally greater than that during ebb tide. The single-width bedload transport rate calculated according to Dou's formula was basically consistent with the measured value, but there were some differences in magnitude. The calculated average bedload transport rate during the tide was 0.004 kg/(m∙s), which was smaller than the measured value. The calculated maximum bedload transport rate at maximum flood was 0.031 kg/(m∙s), while that at maximum ebb was 0.028 kg/(m∙s), which means the measured value during flood tide was greater than the calculated value and vice versa during ebb tide. Therefore, the applicability of the comprehensive coefficient recommended by the formula at the Yangtze Estuary requires further exploration.