Dredging of the Shenzhen-Zhongshan Link in the Pearl River Estuary, China: Short-Term Siltation Mechanism for a Trial Trench

Abstract

Han, Z.; Li, H.; Xie, H.; Yang, H.; Ouyang, Q., and Gong, S., 2022. Dredging of the Shenzhen-Zhongshan Link in the Pearl River Estuary, China: Short-term siltation mechanism for a trial trench. Journal of Coastal Research, 38(5), 988–998. Coconut Creek (Florida), ISSN 0749-0208. Understanding the short-term, particularly daily, siltation mechanism of a dredged trench is critical for immersed tunnel construction, as well as for offshore engineering and coastal management. This study explored the short-term siltation mechanism of the trial trench dredged for the Shenzhen-Zhongshan Link in the Pearl River Estuary, China. Monthly silting characteristics over a period of ∼11 months indicate that the silting intensity during the flood season was much larger than during the dry season. Local suspended sediment concentrations (SSCs) also varied on a flood–dry seasonal cycle, which were impacted by the suspended load from the Pearl River. Daily silting characteristics indicate that the silting intensity during spring tides were higher than during neap and moderate tides and that the local SSCs and flow velocities also varied on a spring–neap tidal cycle, which was dominated by periodic variations in the astronomical tide. The flow velocity deceased substantially from the surface to the bottom of the trench, and flow circulation occurred at the bottom of the trench, which aided the silting process. Seasonal changes in the sediment load from the Pearl River were the dominant cause of the changes in suspended sediment around the trench, which produced seasonal siltation changes in the trench. Daily changes in trench siltation were directly caused by the amount of sediment that entered the trench, which was affected by changes in the flow velocity and bottom SSC around the trench during the neap–spring tidal cycle. Although the high-siltation intensity during the flood season was unhelpful, the low-siltation intensity during neap and moderate tides was helpful for the construction of immersed tunnel during the flood season.