|Cohesive sediment transport model for the Lower Sea Scheldt: steps for set-up and further development|
Kuijper, C.; Winterwerp, J.C. (2004). Cohesive sediment transport model for the Lower Sea Scheldt: steps for set-up and further development. Ministerie van de Vlaamse Gemeenschap. Departement Leefmilieu en Infrastructuur: Brussel. 53 pp.
Cohesive sediments; Numerical models; Belgium, Lower Sea Scheldt [Marine Regions]; Marine; Brackish water
The managing authorities of the Lower Sea Scheldt in Belgium have to decide on various measures to guarantee standards on safety, transport and water quality issues in the area. 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. In this report the necessary steps have been described to arrive at an operational numerical model, which can be utilized to assess siltation rates and sediment distribution in access channels. Furthermore, the model should be capable to address the effects of mitigating measures, like passive devices. in reducing siltation rates.
The Lower Sea Scheldt is located in the mixing zone of the Sheldt estuary, which implies that the hydrodynamics are governed by the interaction of (fresh) river and (salt) sea water, resulting in density-induced gravity currents. Along with the complicated geometry and the tidal effects, this results in a three-dimensional now pattern, which should be modelled according to a three-dimensional approach for the area of interest. Boundary conditions at the upper boundary (at Schelle) and the lower boundary (near Waarde) will be derived from an overall model.
The modelling of the dynamics of cohesive sediments requires an adequate description of the transport cycle, such as: horizontal transport, flocculation, settling and deposition, consolidation and erosion. Many of these aspects are still subject to research and as such a phased approach for the set-up of a cohesive sediment transport model is proposed. During Phase 1, already implemented formulations will be used and the DELFT3D SED ON-LINE model, equipped with state-of-the-art process formulations, will be set up for the Lower Sea Scheldt in conjunction with the WAQUA SCALWEST2000 model, as part of the SIMONA environment, coupled with WAQ. For both models grid schematisations of the areas already exist Following calibration and validation of the Delft3D model and the application of the model in answering managerial questions new process formulations, as described in this report, will be implemented as part of Phase 2 of the project. The overall model, covering the Western Scheldt incl. Voordelta, Lower Sea Scheldt and upper reaches of the Scheldt river, will be based on WAQUA/TRIWAQ + WAQ, or alternatively WAQUA/TRIWAQ + SLIB3D.