The tidal dock called Deurganckdok (Port of Antwer p) is situated in the macro tidal estuary of the Sc heldt River and is directly connected to the river withou t the shielding properties of a lock. Due to its po siti n in the estuary near the Estuarine Turbidity Maximum (ETM) of the estuary, large amounts of silt and clay are available for sedimentation. The dock effectively acts as a sedim nt trap, with a trapping efficiency as high as 0.4 3. During the first five years after its commissioning, the sedim entation of the dock has been closely followed by m eans of intensive monitoring of both long-term point measur ements and through tide campaigns with high spatial resolution. The mass balance of the dock’s sediment bed has bee n monitored using density profiling. It was shown t hat the average rate of sedimentation of the dock is as hig h as 1 cm/day. A semi-empirical model of the siltation of the dock has been developed to gain insights in the contrib ution of the different mechanisms of sediment exchange with the Scheldt River. Long term siltation calculations sho wn the model is capable of reproducing the sediment balanc e of the dock. After numerical and physical modeling it was shown that a Current Deflecting Wall (CDW) has the potent ial o reduce the sedimentation in the dock (Roose et al, 2013). The construction of this structure has now b een executed and the first monitoring results are available of t he post-construction period. Due to the natural var iability of the estuarine sediment concentration levels, the statis tical trend change cannot be proven yet, but measur ments of the flow pattern near the dock entrance reveal changes that can be incorporated in a semi-empirical model of the sedimentation, bringing forward first estimates of the sedimentation reduction in the dock.

Monitoring the siltation rate at Deurganckdok, Port of Antwerp, and its reduction by a current deflecting wall

Sedimentation processes in the navigation channel of Patos Lagoon Estuary, southern Brazil

Port silting is a common and natural process which often causes serious inconveniences for safe navigation and requires expensive dredging operations to keep the port operative. Sediment deposition is closely related to the exchange water between the basin and the surrounding environment; one way to limit deposits is by reducing the flow entering the port. However, this may be in contrast with the need for adequate sediment quality, which in turn is closely related to an appropriate water current. This seems to be particularly important in lagoon environments, where sediments are often polluted, making its disposal more complicated and costly. The present paper investigates the situation of the port of Marano Lagunare (Italy) by means of a bidimensional morphological-hydrodynamic and spectral coupled model. To reduce the sediment input into the port, the closure of a secondary port entrance is usually suggested. However, this work demonstrates that a complete dredging of the secondary port inlet allows for an increase in water circulation or efficiency renewal, which ensures a better oxygenation at the bottom of the canals.

Improvement in the Sediment Management of a Lagoon Harbor: The Case of Marano Lagunare, Italy

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.

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

Coastal zones provide about 70% of world’s ecosystems services. However, more than 25% of these habitats have been modified by human activity at both land and sea. At the intertidal ecotonal zone, habitat modification is equally severe, as almost 20% of world’s shoreline is now artificial. Coastal defense structures are more abundant in areas where the ecosystem richness, diversity and productivity are higher, such as coastal lagoons, estuaries and bays. As these degraded areas are under high human pressure, their protection should be prioritized. Coastal infrastructure, particularly those enclosing highly modified water bodies, such as ports and marinas, are hubs for pollution and human activities, such as trade and leisure. These have become a serious threat to marine coastal communities, due to habitat degradation and disease spread, and ecological-engineering interventions are now an imperative to integrate urban with nature and improve life and ecosystem quality for coastal settlements. 

Vincent Hamani

Papers

Dynamics and management of siltation in a macro-tidal marina: The case of La rochelle marina, France

The forgotten ones of ports: The filter feeders at the heart of siltation processes.