Presence of Connecting Channels in the Western Scheldt Estuary

Abstract

To predict the effects of dredging operations in the Western Scheldt estuary, insight into the morphological behaviour of its channels is needed. The estuary features two large main channels that meander alongside each other and that are linked by smaller connecting channels. These connecting channels originate from water level differences between the two main channels. Three hydrodynamic mechanisms are investigated that are responsible for generating such water level differences: (1) differences in tidal wave propagation along two neighbouring main channels, (2) centrifugal forces, and (3) Coriolis forces. The magnitude of the three mechanisms is analytically assessed based on channel geometry, which is derived from historical depth charts. The analysis demonstrates a large temporal variability of the water level differences due to tidal wave propagation, mainly as a function of changes in the depth ratio between the two main channels. Conversely, both the centrifugal effect and the Coriolis effect are relatively constant over time. The temporal evolution of the connecting channels can therefore primarily be attributed to the wave propagation mechanism. A correlation analysis reveals a linear relationship between connecting channel dimensions and the net water level differences produced by the three processes. The relationship suggests that dredging operations may significantly influence the evolution of connecting channels by changing the depth ratio between the two main channels. The proposed future deepening of the navigation channel is therefore expected to induce a decline in the size, or even a total disappearance, of connecting channels in some parts of the estuary.

Growing Forced Bars Determine Nonideal Estuary Planform

“…Our experimental results suggest that without any human interference (e.g., dredging or bank protection), the morphodynamics of macrocells remain active: the roles and locations of ebb and flood tidal channels may reverse within approximately 1,000 tidal cycles and intertidal bars between these channels are continuously reworked. This is in contrast with natural systems under human interferences, in which dredging may cause degeneration of the affected cell and subsequently evolve into a single‐channel system (Jeuken & Wang, ; Wang et al, ; Wang & Winterwerp, ) and for which smaller connecting channels are disappearing by marsh formation on top of the shoals (Swinkels et al, ). Open questions include what the effect of dredging and dumping will be on the morphodynamics of estuaries and how an engineered estuary compares to a reference case with exactly the same initial and boundary conditions but without any human interference.…”

A fully implicit wetting–drying method for DG-FEM shallow water models, with an application to the Scheldt Estuary

“…The flow circulates smoothly around the sand banks and no spurious noise is visible. Asymmetric flow patterns between ebb and flood channels are clearly observed [41].…”

“…The estuary is generally very shallow (mean depth is roughly 10 m) but features deep flood and ebb channels (see Fig. 11) that can reach the depth of 60 m [41]. The main estuary also features large tidal flats (mainly Saeftinge and Ballatsplaat) and sand banks between the two main channels, both of which are submerged during high water.…”

The Importance of Combined Tidal and Meteorological Forces for the Flow and Sediment Transport on Intertidal Shoals

“…Although tidal creeks are no full cross‐connecting channels, they have similarities. Just as cross‐connecting channels (Swinkels et al., ), tidal creeks can be affected by flows induced by water level gradients between the surrounding channels (Van den Berg, ).…”