Abstract
The main objective of this paper is to develop a method to simulate long-term morphodynamics of estuaries dominated by fine sediments, which are subject to both tidal flow and meteorologically induced variations in freshwater run-off and wave conditions. The method is tested on the Vilaine Estuary located in South Brittany, France. The estuary is subject to a meso–macrotidal regime. The semi-diurnal tidal range varies from around 2.5 to 5 m at neap and spring, respectively. The freshwater input is controlled by a dam located approximately 8 km from the mouth of the estuary. Sediments are characterised as mostly fines, but more sandy areas are also found. The morphology of the estuary is highly influenced by the dam. It is very dynamic and changes in a complicated manner with the run-off from the dam, the tide and the wave forcing at the mouth of the estuary. Extensive hydrodynamic and sediment field data have been collected in the past and provide a solid scientific basis for studying the estuary. Based on a conceptual understanding of the morphodynamics, a numerical morphological model with coupled hydrodynamic, surface wave and sediment transport models is formulated. The numerical models are calibrated to reproduce sediment concentrations, tidal flat altimetry and overall sediment fluxes. Scaling factors are applied to a reference year to form quasi-realistic hydrodynamic forcing and river run-off, which allow for the simulations to be extended to other years. The simulation results are compared with observed bathymetric changes in the estuary during the period 1998–2005. The models and scaling factors are applied to predict the morphological development over a time scale of up to 10 years. The influence of the initial conditions and the sequence of external hydrodynamic forcing, with respect to the morphodynamic response of the estuary, are discussed.
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Acknowledgments
The authors acknowledge the support by IAV and their special advisor Bernard Latteux. The study has benefitted from his inspiring input and review of reports. The authors also appreciate discussions with Pierre le Hir. The work required changes to standard DHI software. Bed masses, for each fraction in each layer from the previous simulation year, can now be applied as initial conditions for the next year. The settling velocity formulation was modified to have one fraction with, and one fraction without flocculation. These changes were implemented with the help of Ole Petersen, DHI. The paper has greatly benefitted from comments by the two anonymous reviewers and the editor Han Winterwerp. This work has been partly supported by the Danish Council for Strategic Research (DSF) under the project: Danish Coasts and Climate Adaptation – Flooding risk and coastal protection (COADAPT), project no. 09-066869.
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Responsible Editor: Han Winterwerp
This article is part of the Topical Collection on the 11th International Conference on Cohesive Sediment Transport
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Vested, H.J., Tessier, C., Christensen, B.B. et al. Numerical modelling of morphodynamics—Vilaine Estuary. Ocean Dynamics 63, 423–446 (2013). https://doi.org/10.1007/s10236-013-0603-7
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DOI: https://doi.org/10.1007/s10236-013-0603-7