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This thesis presents the development and validation of a novel three-dimensional sediment transport and morphological numerical model suitable for coastal regions. The thesis discusses the modelling of both suspended and bed-load transport of non-cohesive sediment, important aspects of the morphological updating scheme, and approaches used to model the three-dimensional effects of waves on coastal hydrodynamics. Results of several validation studies are presented and the model is shown to perform well in several theoretical, laboratory, and full scale test cases. Application of the model and acceleration techniques to the complex and dynamic entrance to Willapa Bay, WA, USA is also critically analysed and discussed. A new method to select a representative morphological tide for coastal environments containing significant diurnal tidal energy is presented.

This dissertation qualitatively investigates the morphodynamic response of a large inlet system to IPCC projected relative sea level rise (RSLR). Adopted numerical approach (Delft3D) used a highly schematised model domain analogous to the Ameland inlet in the Dutch Wadden Sea. Predicted inlet evolution indicated the typical channel/shoal pattern of the Ameland inlet and an agreement with the empirical-equilibrium relations. RSLR enhances the existing flood-dominance of the system leading to erosion on the ebb-tidal delta and accretion in the basin. Tidal flat evolution was quite stable applying low RSLR whereas the system indicated turning into a lagoon under high RSLR. Nourishment application hardly enabled the RSLR induced sediment demand of tidal flat evolution.

This thesis presents the development a generic morphological model for both structured and unstructured grid and the extension to a biogeomorphological model. For the morphological model, numerical algorithms are adjusted to adapt unstructured grid and are validated against analytical solutions and flume experiments. For the bio-geomorphological extension, relevant ecological processes are coupled with morphodynamic processes at various scales and are validated against the field data in Lake Veluwe. Capability of the model has been explored for applications of two salt marsh restoration cases in United States and the large scale morphodynamics of shoreface connected radial sand ridges located in South-east China Sea. Validations and applications show that this modelling platform is capable to be a multidiscipline research tool for morphologists and ecologists / biologists.

The morphology of tidal basins includes a wide range of features developing along different spatial and temporal scales. Examples are shoals, channels, banks, dunes and ripples. Coastal engineers use their engineering tools to answer questions on the processes governing the short term (< decades) development of these morphological features. Geologists apply their conceptual models and reconstruction methods to answer questions related to a much longer time scale (> centuries). This two-sided approach has left us with limited understanding of processes occurring on intermediate scales (> decades and < centuries), whereas the morphodynamics of these intermediate scales are of special concern to sustainable coastal zone management. This study is part of a collective effort to bridge the aforementioned gap by extending the use of coastal engineering tools (process-based models) to geological time scales to provide more understanding of the physical processes governing the long-term morphodynamic behavior of tidal basins. A fundamental question addressed is whether or not process-based models can reproduce trustworthy long-term developments. To answer this question the Dutch Waddenzee is chosen as a reference case. This study suggests that the question has a positive answer. By comparing model results with measured developments in the Waddenzee, this study shows that a process-based model can reproduce channel-shoal patterns and their long-term development qualitatively well. Modeled parameters such as area, volume and height of the inter-tidal flats obey the databased equilibrium equations. This study also demonstrates the models' ability to qualitatively assess the impact of large scale human intervention in a tidal basin. For example, the model is able to reproduce the change in tidal transport regime and the ensuing morphodynamic changes due to an extreme impact such as the closure of the Zuiderzee. Although the highly schematized simulations produced qualitatively good results, they also revealed the need for a better process description. As the first step to improve model performance a methodology was developed to account for sediment composition and distribution in the bed. In the next step different methodologies to schematize wave action for long-term morphological simulations were investigated. investigated the wave climate. Model results show that the chronology of wave conditions and the wave schematization approach have a limited effect. The outcome of long-term morphodynamic simulations with different wave and tidal conditions are in good agreement with conceptual models. For the reference case, model results revealed that the morphological impact of wind waves is not only important outside the inlet and at the ebb-tidal delta, but also within the tidal basin. A final conclusion is that adding methodologies for bed composition and wave schematization to the model of the Waddenzee area improved the hindcasting simulations qualitatively.