Study of density currents in the framework of the LTV for the Scheldt estuary: executive summary
Bijlsma, A.C. (2004). Study of density currents in the framework of the LTV for the Scheldt estuary: executive summary. Waterbouwkundig Laboratorium en Hydrologisch Onderzoek: Antwerp. 31 pp.
One of the key issues of the Long-Term Vision (LTV) for the Scheldt estuary is the sediment dynamics in the Scheldt estuary and the approach channels to the locks. The fate of fine-grained cohesive sediments forms a crucial role in many of the managerial questions and the availability of a predictive tool in these matters is urgently requested.
As a first step the study of the density currents in the maritime access to the Port of Antwerp in the Lower Sea Scheldt was carried out. The study consisted of five tasks: (i) the field investigation, (ii) the physical model study, (iii) the numerical model investigation, (iv) the outline of a cohesive sediment transport model and (v) the delivery of software. This Executive Summary presents the main considerations and results of the full study.
In 2002, IMDC conducted an extensive measurement campaign in the Lower Sea Scheldt, which included through-tide measurements at neap and spring tide. A coherent set of data was gathered for the calibration and verification of numerical flow models, and to improve the knowledge on density currents e.g. near the Kallo lock and the future Deurganckdok.
The physical scale model investigation focussed on the exchange flow between the Deurganckdok and the Scheldt estuary, and on the influence of a Current Deflecting Wall (CDW) on this exchange flow. Although the total volume of the exchange flow was not significantly reduced by the final CDW configuration, siltation may still be reduced as observations showed less near-bed inflow. Furthermore, the CDW reduced the eddies in the harbour mouth, which is favourable for navigation.
In the numerical investigation a numerical scale model, based on the Delft3D-FLOW with sigma-coordinates provided a reasonable reproduction of the exchange now between dock and river. However, more work. will be needed before a CDW design can be investigated reliably by numerical modelling.
Finally, the follow-up steps have been described that must result in an operational numerical model for cohesive sediment transport, which can be utilized to assess sillation rates and sediment distribution in access channels, and to address the effects of mitigating measures.
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