The concept of “representative tides” in morphodynamic numerical modelling
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Process-based numerical modelling of coastal morphodynamics involves model and data reduction schemes in order to cope with computational limitations. Model reduction, on the one hand, may involve the discretisation of an interactive multidimensional, diverse natural system into a reduced set of coupled process-simulation modules. Data reduction schemes, on the other hand, are used to parameterise processes. The use of schematised open-boundary conditions, which are considered as representative in terms of their cumulative morphological effect, is based on the concept of “morphological” or “representative” boundary conditions. Recent model applications show realistic tendencies in terms of depositional and erosional areas. By contrast, the reproduction of characteristic changes in morphology such as the migration of bars, banks and channels is only occasionally achieved. Using field data on observed morphological impact of a single storm event and numerical model data, it is demonstrated that the concept of representative tides may lead to simulations of morphological development lacking natural dynamics. It is proposed that rather than being based on “representative” single tides, morphodynamic models should be applied with open-boundary conditions which take variations in longer-term tidal and meteorological forcing into account.
KeywordsTidal Inlet Tidal Ellipse Data Reduction Scheme Storm Flood Morphodynamic Model
The authors thank the following German authorities for providing field data: annual bathymetric data were obtained from the Federal Shipping and Hydrographic Office (BSH), Hamburg, and water-level data from the Waterways and Shipping Office (WSA), Cuxhaven. We are grateful to the captain and crew of the RV Ludwig Prandtl for their technical support and Martina Heineke for the processing of multibeam data. This study was funded by the Deutsche Forschungsgemeinschaft as part of the DFG Research Center Ocean Margins (RCOM) at the University of Bremen, Germany.
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