The port of Rotterdam was full and new mooring locations were required to host the largest ships in the world. And if there’s no space to expand on land, why not create land in the sea? That is exactly what The Netherlands did by creating Maasvlakte 2. The construction of Maasvlakte 2 started in 2008 and was officially completed on May 22nd , 2013. This research focused on the morphodynamics in the domain between the cube reef and cobble beach at the hard flood defence, which is named "the lagoon". Over the past 5 years a large sand volume propagated into the lagoon. The current sand volume (after 5 years) in the given domain is about four times larger than the predicted value by PUMA. The processes behind the sand layer formation were not fully understood.
This research started by creating a conceptual model with all processes that could contribute to the formation of the sand layer. All processes are divided into hydrodynamic or aeolian transport, whereby hydrodynamic transport is divided into overtopping over the cube reef and transport through the cube reef due to tidal currents. We performed field experiments at Maasvlakte 2 to measure the flow velocity in the lagoon and to measure the aeolian transport capacity. From a sediment budget analysis we observed a sand layer increase during winter periods. This increase is justified with the fact that sand transport towards the lagoon depends on extreme events, which happen mostly during winter periods. Based on the estimated transport volumes we concluded that the main mechanisms that contribute in the formation of the sand layer are overtopping over the cube reef and aeolian transport, whereby overtopping is the largest mechanism. Our estimates indicate a total maximum sand layer volume of 51,000m3 (whereby transport by overtopping = 25,000m3, tidal currents = 8,700m3 and aeolian transport = 17,300m3). Which leaves 20,000m3 of sand unaccounted for compared with our estimated 71,000 m3 volume of sand in the lagoon. The accuracy of each calculation is analysed in order to explain the missing volume compared with the total sand layer volume. Based on this analysis we concluded that only the uncertainty in the overtopping calculation can explain the missing volume of 20,000m3. High wind speeds and high waves will cause for sand transport towards the lagoon. Aeolian transport will always happen if there is a supply of granular material and atmospheric winds of sufficient strength. Moreover, the source for aeolian and hydrodynamic transport is the, southern located, soft protection. Since nourishments are necessary to secure the safety of the soft protection, the supply of sediment will remain. Sand is transported in northern direction along the hard protection by longshore transport. Currently, the water depth northwards of KP2700 is too deep to stir the sediment up and transport it into the lagoon by overtopping. Depending on the foreshore migration in the northern direction, the sand layer will also increase in northern direction.

Coastal dunes serve as a first line of protection against flooding by the sea. In the recent past, the interest in secondary services provided by coastal dunes has increased. These services include ecological values and recreation. In order to manage and maintain the coast as an attractive area that combines coastal protection and ecological values, the natural dynamics have to be understood. In view of this, numerical models with quantitative predictive capabilities on the development of coastal dunes can give a lot of insight. A model is developed with the aim to improve the current aeolian modeling by implementing biological and physical processes adapted from different existing models, developing a modular aeolian transport model with quantitative predictive capabilities for dune development. The current version of the model is capable of simulating barchan dunes and the initial stage of coastal dune formation: Embryo dunes. Potentially the model can be used to determine the influence of tidal ranges, storm frequencies, armoring, salinity and precipitation on dune building processes. This will result in a greater insight in the general behavior of coastal systems, including the evolution of embryonal dune fields as well as foredune characteristics like maximum height and autocyclic formation of transverse dunes. On the other hand the model can also be used during more practical situations such as computing recovery times of coastal dunes after extreme events or for the creation of artificial blowouts.

This thesis explores the nature of coastal dune behavior and the role of sediment supply in the aeolian system. The first part of the thesis conducts a data analysis based on the Dutch JARKUS dataset, which provides yearly measured profiles along the Dutch coast. A series of parameters derived from the profile measurements have been used to represent the dune behavior quantitatively. Two locations with different coastal orientations, the Rijnland and Ameland coasts, have been studied. The theoretical wind transport capacity calculated for the two coasts showed very different results, where the transport capacity in cross shore direction for Ameland was found offshore dominant with very small onshore component while the one for Rijnland was found onshore dominant with much larger onshore component. The calculated actual dune growth rates along the two coasts had much less values than the transport capacity but demonstrated similar trend: Rijnland experienced more dune accretion than Ameland. The spatial variations in coastal morphology derived from the measurements have been correlated to the alongshore varying dune behavior, showing that a larger dune accretion is usually linked to a wider active dune but no obvious relationship can be identified between beach width and dune growth rate. The second part of the thesis discusses a modeling study using the AeoLiS model. The inconsistency between the actual dune accretion and the theoretical onshore wind transport capacity was probably because the sediment availability dominated the aeolian sediment transport, which inspired an attempt to analyze the role of sediment supply in the aeolian system through a modeling study. Therefore AeoLiS has been used to simulate aeolian sediment transport, dune volume changes and the combined effect of erosion and accretion processes in the coastal systems. In the modeling study, 11 scenarios have been simulated. By comparing the simulation results of the different scenarios, the influences of several different processes on the aeolian sediment transport have been analyzed. Dune vegetation was found to be necessary to acquire dune accretion. Sediment sorting and beach armoring were found to be able to significantly reduce the aeolian sediment transport, indicating the important role of sediment supply in the aeolian system. And the more the nonerodible roughness elements existed on the bed, the more the aeolian transport could be reduced. In the onshore wind dominant system, the existence of the offshore wind reduced the onshore aeolian transport in the model. In the offshore wind dominant system, the offshore wind needed to be filtered out to enable the model to reproduce the pattern of onshore aeolian transport and dune accretion. For Rijnland which experienced mainly onshore winds, the modeled dune accretion volume was relatively larger than the measured dune accretion based on the data analysis. For Ameland where the present winds were mainly offshore, the simulated and measured dune accretion volumes were quite close. Similar to the trends in the wind transport capacity and the dune growth rate, the modeled dune accretion volume for Rijnland was also larger than the one for Ameland.