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This thesis presents the results of a series of studies on sedimentation mechanisms in a stratified tidally energetic estuarine system of the Port of Rotterdam. An understanding of the dominant sedimentation processes is essential to develop appropriate siltation countermeasures, reduce costs of maintenance dredging and to assess their effect on the water system as a whole. The processes that result in the formation of turbidity maxima in the Rotterdam Waterway and the relationship to harbour siltation was studied by a combination of dedicated field campaigns and three-dimensional model simulations. The gradient of the tidal water level generally dominates the water motion. However, the trapping of suspended sediments and siltation are mainly determined by the baroclinic pressure gradient and stratification caused by salinity. The salinity structure generates currents and damps turbulent mixing processes. The exchange of suspended sediment with harbours is mainly determined by the sediment supply at the salt wedge because of trapping of suspended sediment near its head. Therefore, baroclinic currents dominate the transport of sediment in the harbour mouths and basins. The saltwater intrusion length varies continuously as a result of water level gradients due to periodicities of the tide, wind, and variations of the freshwater discharge. This length determines the location at which significant siltation occurs and it determines the trapping efficiency of suspended sediment in the system. Uncertainties in the prediction of the salinity structure determine the quality of the prediction of the distribution of suspended sediment in the system.
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