Observational study on sediment transport at the southern channel bed of the Yangtze River Estuary

To address the issue of lack of measured data on sediment transport at the bed of the Yangtze River estuary and to study the characteristics of sediment mobility in the southern channel, a sediment observation system suitable for the hydro-sedimentary environment of the Yangtze Estuary was developed based on the principles of the pit-measurement method, yielding reliable data on sediment transport processes in the lower disturbance regime at the Nantong sandy section of the southern channel. Observational results indicate that during tidal cycles (average tidal range of 3.3 m), the sediment transport rate is closely related to flow velocity, with an observed average tidal sediment transport rate of 0.007 kg/(m∙s), peaking during the flood tide at 0.045 kg/(m∙s) and at 0.020 kg/(m∙s) during ebb tide. Throughout the tidal cycle, under identical flow velocity conditions, sediment transport rates exhibited disparities, with higher transport rates during the flood tide than during the ebb tide. The variation trends of the unit-width suspended sediment transport rate calculated using Dou Guoren's formula are generally consistent with the observed values, albeit with differences in magnitude. The calculated average tidal sediment transport rate was 0.004 kg/(m∙s), less than the observed values, with a maximum calculated value of 0.031 kg/(m∙s) during the flood tide and 0.028 kg/(m∙s) during ebb tide; observed values during the flood tide were higher than calculated values, and the reverse was true during the ebb tide. The composite coefficient recommended for sediment transport in the formula requires further exploration.