Threatened by rising sea levels and other climate change induced hazards, there is an increased need for coastal flood protection, such as storm surge barriers. However, the construction of such barriers may lead to unwanted coastal changes. This thesis examines the effect of the Eastern Scheldt storm surge barrier on sediment pathways and the implications for coastal erosion. In addition, possible sediment-based interventions to redirect the current with the aim of reducing coastal erosion were investigated. First, a literature study was performed to provide historical context on the natural and human induced development of the ebb tidal delta. A data analysis on the sediment budget of the ebb tidal delta was performed, which showed that from 1960 to 1987 the ebb tidal delta gained sediment, from 1987 to 2010 it lost sediment, and from 2010 to 2019 it gained sediment again. A numerical model in Delft3D FM was used to produce sediment transport vector fields over a morphologically representative tidal cycle, which were then visualized using SedTRAILS. The research found that the barrier decreased the strength of the ebb current on the entire ebb tidal delta. The Roompot Zuid has a predominantly ebb-dominant character before the barrier in 1976 but changes to a flood-dominant character due to the construction of the barrier, which weakened the ebb-current. In 2019, part of the Roompot Zuid regained an ebb-dominant character. The Schaar van Onrust also became flood-dominant due to the barrier, eliminating the sediment-retaining effect the ebb dominated current in this channel. This shift indicates that sediments that previously stayed in front of the coast of Noord-Beveland are now redistributed further along the coast in south western direction, which led to a sediment deficit and erosion at the coast. The tested interventions seem to induce little structural changes in the tidal currents. The removal of sediment causes the sediment transport patterns to converge into the dredged area, suggesting deposition. Therefore the tested interventions do not seem effective from a coastal management perspective. The approach used here may also be useful for the assessment of sediment transport impacts at other sites where the construction of similar barriers is being considered. ... Read more

The Wadden Sea serves multiple roles: it acts as a protective barrier against severe wave conditions, is a natural habitat for diverse flora and fauna and has recreational purposes. This research provides a comprehensive analysis of the intricate morphological dynamics of the Wadden Sea. By implementing various model schematizations, the study aims to enhance understanding of complex interactions between tidal inlets and basins, sediment transport dynamics, the influence of forcing actors and the importance of grid resolution. The ultimate goal is to improve the process-based models that are used to perform morphological forecasts, serving as a valuable tool for efficient coastal management and ensuring the preservation of this unique tidal ecosystem.

The study incorporates several schematizations, including the spatial extent of the modelling grid (domain schematization), grid resolution and various forcing components applied to the model boundaries and grid. Analysing water and sediment exchange between basins and through the Ameland tidal inlet has revealed distinct differences in hydrodynamics and morphodynamics across the model schematizations.

The single-inlet domain schematization encompassed only the Ameland tidal inlet region, while the more expansive multi-inlet schematization captured the entire Wadden Sea area. The single-inlet schematization does not account for hydrodynamic interactions between the Ameland basin and neighboring basins. This impacts sediment transport and morphological development in the Ameland inlet. A multi-inlet approach, encompassing the entire Wadden Sea, grants a more comprehensive model. The model with Wadden Sea domain schematization is essential for obtaining accurate results, as it showed significant differences in sediment transport compared to the single-inlet model. Modeling practices that exclude transport dynamics between tidal basins risk misrepresenting the natural processes in play.

Around the Ameland inlet, ebb dominance is observed in most regions, but there are exceptions in the marginal flood channel and at the outer side of the ebb-tidal delta. The Ameland model shows more ebb-dominance than the Wadden Sea model. Sediment transport during ebb periods exceed than during flood periods and differences in sediment transport between model schematizations are more pronounced during ebb than during flood.

Regarding the drivers of change, the spring-neap tidal cycle is particularly indicative of periods with meaningful residual sediment transport. Wind, especially from southwesterly directions, has a significant impact on water transport dynamics and a limited impact on sediment transport through the inlet.

Two grid schematizations are used, one with a base resolution of 60 by 60 meter and another with a high-resolution grid of 30 by 30 meter near the inlet. An enhanced grid resolution results in marginal changes in simulation outcomes, offering limited advantages for the conducted short-term morphological forecasts.

Overall, enhanced model schematizations can significantly improve short-term morphological forecasts of the Ameland tidal inlet, providing a more accurate and comprehensive representation of the complex hydrodynamic and sediment transport processes. Leveraging high-performance computing (HPC) for executing Delft3D-FM models has been central in this research, offering possibilities to enhance model resolution and reduce computational time.

The benefits of HPC come with the added challenge of mastering new software, handling larger models and interpreting more extensive data sets. A deep understanding of the physical processes and careful cost-benefit consideration is crucial, as increased computational power does not automatically resolve all modeling limitations. As such, the effective use of HPC in coastal modeling requires a balance between its sophisticated capabilities and the complexity it introduces. ... Read more

The Wadden Sea is a large system of tidal flats and barrier islands. Its individual features have been heavily researched, but sufficient knowledge on the sediment transport patterns on the scale of the Wadden Sea is not yet available. This thesis aims to indicate the dominant sediment transport patterns in the Dutch Wadden Sea and the hydrodynamic forcing mechanism the patterns can be attributed to. The Delft3D-FM model used to indicate these patterns is first adapted by implementing an improved Manning’s roughness field. To assess the patterns for each contributing hydrodynamic forcing mechanism, the tide, wind and waves are added to the model one by one. The results show that the Dutch Wadden Sea is a highly interconnected system, with the influence of each hydrodynamic forcing mechanism depending on the feature and inlet system. ... Read more

A large part of the Dutch coast, the barrier islands in the Wadden Sea included, would be eroding if the deficit in the total sediment budget was not compensated for through nourishments. Ebb-tidal deltas have an important function within the coastal system that make them of interest for coastal defence as a source and transport path for sand to the back-barrier basins and the island coastlines. As part of the Kustgenese 2.0 project, a pilot nourishment of 5.5 million m3 has been placed on the Ameland ebb-tidal delta. Improved understanding of sediment bypassing processes and the interaction with a nourishment is needed for strategic placement of nourishments in the future. In this thesis we analyse the high-frequency bathymetric dataset available at Ameland inlet between 2005 and 2020 and model the tide- and wave-driven transport pathways using to SedTRAILS to determine how sediment bypassing works under natural circumstances and under the influence of a nourishment. A new series of conceptual models has been proposed. These show that the formation and growth of a series of ebb-shields on the western side of the ebb-tidal delta plays an important role in sediment bypassing. Their development gradually results in transport pathways connecting the western side of the ebb-tidal delta to the major transport pathway along the ebb-delta front, which forms a direct connection to the Ameland coast in 2017. The influence of the pilot nourishment on sediment bypassing processes is limited, adding volume to the system but not altering the existing transport pathways. Transport pathways show that sediment from the nourishment eventually reaches the Ameland coast and is unlikely to feed the Terschelling coast or the tidal basin. This is valuable knowledge for the future sustainable coastal management of Ameland inlet, which can also be extended to other inlets. ... Read more

Burrard Inlet (Vancouver, Canada) has been the home of the Tsleil-Waututh Nation (TWN) for thousands of years. Over the past decades, ongoing erosion has been observed along the shores of Burrard Inlet and the TWN reserve specifically. This leads to loss of land for the TWN community, damage to infrastructure, and exposure of historic sites with cultural value. Currently, there is insufficient knowledge concerning both the governing processes for sediment transport and transport pathways into, within, and out of Burrard Inlet. This knowledge is needed to propose and evaluate effective measures to prevent further erosion. This study aims to investigate the transport pathways in Burrard Inlet and give more insight into the mechanisms governing sediment transport in this inlet.

For this purpose, a Delft3D FM model of the area is set up and calibrated. This model is used to analyze sediment transport in the inlet under various forcing conditions. Transport pathways are visualized using SedTRAILS.

The model shows that flows and sediment transport in Burrard Inlet are tide-dominated and governed by the topography. Flows are strongly accelerated in constricted areas (First Narrows and Second Narrows), which leads to large velocity differences. Following the velocity field, sediment transport patterns are correspondingly dominated by these topographical restrictions. In the wider basins, flows slow down and form eddies. The model results suggest that these eddies act as sediment sinks. Additionally, sediment is lost into Indian Arm, a deep fjord with low flow velocities at the eastern end of Burrard Inlet. The possible pathways for sediment originating from the eroding shorelines at the TWN reserve are visualized. As soon as sediment from these banks is mobilized, it tends to move away from the shore with a final destination either in one of the eddies or in Indian Arm. The impact of wind and waves on the sediment transport patterns is limited.

Since first European contact in 1792, the shoreline of Burrard Inlet has changed significantly due to dredging activities, land developments, and industrial development as the city of Vancouver was built. Reconstructed historic shorelines are implemented in the model to assess the consequences of these shoreline changes on the sediment transport. Model results show that the tidal prism and the velocities in the Narrows have decreased since 1792, while the tidal range has increased. Moreover, sediment mobilized along the eroding shorelines showed greater potential for deposition along these same shores in 1792, compared to the present-day situation.
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