Abstract
The fringes of estuaries are often characterized by the presence of side embayments (secondary basins), with dimensions in the order of hundreds of meters to tens of kilometers. The presence of secondary basins significantly alters the hydrodynamic and sediment characteristics in the main estuary, implying that loss of secondary basin area due to human interventions might affect the estuarine morphodynamics. Analysis of historical bathymetric data of the Western Scheldt Estuary (Netherlands) suggests that closure of its secondary basins has triggered the observed lateral displacement of the nearby channels. This analysis motivated investigation of the impact of secondary basins on decadal evolution of estuarine channels, using the numerical model Delft3D. Model results show that channels that form near a secondary basin are located farther away from the bank of the estuary with respect to their positions in the case without a basin. Overall, results in cases with two or three basins are similar to those in case with one single basin. The wider the basin, the farther away the nearby channel forms. Removing a secondary basin causes a lateral displacement of the nearby channel toward the bank, indicating that the observed lateral displacement of channels in the Western Scheldt is triggered by closure of its secondary basins. The physical explanation is that tidal currents in the main estuary are weaker and more rotary near secondary basins, favoring sediment deposition and shoal development at these locations. Model results are particularly relevant for estuaries with moderate to high friction and converging width.
| Original language | English |
|---|---|
| Pages (from-to) | 167-186 |
| Number of pages | 20 |
| Journal | Journal of Geophysical Research: Earth Surface |
| Volume | 123 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - 1 Jan 2018 |
Funding
We would like to express our sincere gratitude to Huib de Swart (IMAU, Utrecht University, The Netherlands) who provided insight and expertise that greatly assisted this research. Also, we are grateful for his detailed and constructive feedback that greatly improved the manuscript. Rijkswaterstaat (Ministry of Infrastructure and the Environment, The Netherlands) is acknowledged for providing historical bathymetric data of the Western Scheldt Estuary and making their water levels and velocities data publicly accessible. Finally, we would like to thank Gerard Dam (Svasek Hydraulics, The Netherlands) for providing other historical bathymetric data of the Western Scheldt Estuary. This research is part of project “Agenda voor de Toekomst,” 14_094, which is funded by the Flemish-Dutch Scheldt Commission (Vlaams-Nederlandse Scheldecommissie, VNSC). Historical bathymetric data of study area and model output data can be accessed on https://figshare.com/s/ 20c06b2d0e2b94717ab3.
Keywords
- seconary basins
- morphodynamic
- evolution
- estuaries
- channels
- lateral displacement
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