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Ocean Science An interactive open-access journal of the European Geosciences Union
Ocean Sci., 13, 673-690, 2017
https://doi.org/10.5194/os-13-673-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
07 Sep 2017
Modelling of sediment transport and morphological evolution under the combined action of waves and currents
Guilherme Franz1, Matthias T. Delpey2, David Brito3, Lígia Pinto1, Paulo Leitão4, and Ramiro Neves1 1MARETEC, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisboa, Portugal
2Centre Rivages Pro Tech, SUEZ, 2 allée Théodore Monod, Bidart, France
3ACTION MODULERS, Estrada Principal, no. 29, Paz, 2640-583 Mafra, Portugal
4HIDROMOD, Rua Rui Teles Palhinha, no. 4, Leião, 2740-278 Porto Salvo, Portugal
Abstract. Coastal defence structures are often constructed to prevent beach erosion. However, poorly designed structures may cause serious erosion problems in the downdrift direction. Morphological models are useful tools to predict such impacts and assess the efficiency of defence structures for different scenarios. Nevertheless, morphological modelling is still a topic under intense research effort. The processes simulated by a morphological model depend on model complexity. For instance, undertow currents are neglected in coastal area models (2DH), which is a limitation for simulating the evolution of beach profiles for long periods. Model limitations are generally overcome by predefining invariant equilibrium profiles that are allowed to shift offshore or onshore. A more flexible approach is described in this paper, which can be generalised to 3-D models. The present work is based on the coupling of the MOHID modelling system and the SWAN wave model. The impacts of different designs of detached breakwaters and groynes were simulated in a schematic beach configuration following a 2DH approach. The results of bathymetry evolution are in agreement with the patterns found in the literature for several existing structures. The model was also tested in a 3-D test case to simulate the formation of sandbars by undertow currents. The findings of this work confirmed the applicability of the MOHID modelling system to study sediment transport and morphological changes in coastal zones under the combined action of waves and currents. The same modelling methodology was applied to a coastal zone (Costa da Caparica) located at the mouth of a mesotidal estuary (Tagus Estuary, Portugal) to evaluate the hydrodynamics and sediment transport both in calm water conditions and during events of highly energetic waves. The MOHID code is available in the GitHub repository.

Citation: Franz, G., Delpey, M. T., Brito, D., Pinto, L., Leitão, P., and Neves, R.: Modelling of sediment transport and morphological evolution under the combined action of waves and currents, Ocean Sci., 13, 673-690, https://doi.org/10.5194/os-13-673-2017, 2017.
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Short summary
The paper describes a numerical modelling methodology capable of reproducing the hydrodynamics, sediment transport, and morphological evolution of coastal zones under the combined action of waves and currents. The long-term beach response to different designs of coastal defence structures was assessed, as well as the formation of multiple sandbars on the beach slope. The methodology can be applied in engineering studies in order to evaluate the best solution to protect the coast against erosion.
The paper describes a numerical modelling methodology capable of reproducing the hydrodynamics,...
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