Suspended transportation and flux mechanism of sediment in the Jiaojiang Estuary in spring

A detailed study on hydrodynamic characteristics and transportation mechanisms of suspended sediment at two specific sites of the Jiaojiang Estuary were conducted in March, 2017.The data resulted from the observation at anchor stations show that the Jiaojiang Estuary is characterized by a bidirectional field of currents, and the tidal currents at the stations within the river mouth are obviously stronger than that at the sites located outside the river mouth. The depth-mean SSCs at the two stations are 0.3~5.8 kg/m³, and 0.3~1.0 kg/m³, respectively. The results of mechanism decomposition of sediment transport indicate that at the upstream site, the dominant mechanism of transporting suspended sediment is the seaward tidal pumping, which contributes 49.3% of the total absolute sediment flux, followed by the landward advection and the vertical net circulation. As the result, the net suspended sediment transport is 0.39 kg/(m·s) landward. However, the sediments fluxes at the downstream station are dominated by the seaward advection, with 72.6% of contribution, and the net suspended sediment transport is 0.10 kg/(m·s) seaward. The three-layers wavelet analysis and spectral analysis suggest that there are somewhat coupling response relations between the SSC and the sediment transport rate and flow velocity. The sediment transport rate is dominated by the flow velocity at the outer site of the estuary, and SSCs at the site inside.