Coastal defence systems are implemented in many countries for the stability of coastlines
and prevention of erosion and flooding. The maintenance of such schemes includes the use of
'soft' engineering techniques, which require accurate predictions of sediment transport and profile
change. This thesis describes the development of a numerical model for coarse-grained crossshore
transport for use in such schemes. The model combines a hydrodynamic model based on
weakly non-linear Boussinesq equations, coupled to a sediment transport module and a
morphology change module. Studies have been performed on the hydrodynamic and sediment
models to assess the performance of the components for this purpose.
The 1-D Boussinesq model has been validated with physical wave flume data. The model
is shown to provide good predictions for shoaling and breaking waves near the coastline, and is
also shown to provide good predictions for the properties of a reflected wave field. The model is
then used to perfonn a study on the nature of wave shoaling and reflection with regard to the
velocity field, and the development of the velocity skewness pattern is discussed. Recent sediment
transport formulae have been reviewed, and a bed-load sediment transport model has been
developed. A model for differential transport of different grain sized niaterial has also been
introduced. Developed from a river sediment model, this is able to predict sorting of grain sizes
over the cross-shore profile. Results of the combined model are shown for natural plane beaches,
and for beaches coupled with sea walls. The model predicts reduced erosion patterns for irregular
wave fields compared to regular waves, and for mixed sediment composition sea beds compared
to homogeneous sea beds. These findings show agreement with features found in previous
physical studies. A series of sensitivity studjes has also been performed with respect to
hydrodynamic and sediment properties. The model shows a high degree of sensitivity for the profile
changes to these parameters. The ability of the model to show predictions for an evolving beach
profile subject to tidal water depth variation is also introduced.
Date of Award | 2005 |
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Original language | English |
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Awarding Institution | |
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Cross-shore morphodynamics of coarse grained beaches and beach/structure interaction: Numerical modelling and large scale measurements
Lawrence, J. (Author). 2005
Student thesis: PhD