Wind energy from the North Sea is one of the solutions to achieve the climate goals of the Paris agreement. The Dogger Bank, a North Sea sandbank, has a lot of potential for wind energy due to the relatively shallow location and good wind conditions. An artificial island creates even more opportunities, because alternating energy can be converted here into direct current. An island will also make the construction and maintenance of the windmills cost-effective. The Dogger Bank, however, is part of Natura2000 area, for which strict legislation applies. To design a stable island coastal defence, which contributes to the North Sea ecology, it is researched how natural value could be added to make the island licensable. The flat oyster (Ostrea edulis) has been chosen as an umbrella species, a species that creates an environment in which a large group of other species can benefit. The disappearance of the present ecology by building an island can be counteracted by restoring an oyster habitat. To obtain the boundary conditions for a successful oyster bed, research was done into the relationship between the bed shear stress and the historic presence of oyster beds. The shear stress boundary condition for the highest significant waves was 119.8 N/m2 while the shear stress due to the average significant wave climate must stay between 2.5 and 10.3 N/m2. The orientation of the coastal protection, the depth, the profiles (as the presence of a reef or foreshore) and the chosen material are decisive factors for success of oyster beds. Concluded is that opportunities are available in the coastal defence. In typical cross-section are only few areas suitable. For the most exposed side (330-360ºN), it is opportune for oyster beds to grow around the toe and foreshore when located in water deeper than -25.0 m MSL. At the least exposed side (120-150ºN) this is -18.0 m MSL. Reefs and prolonged foreshores are expected to be efficient for creating larger nature enhancing surfaces. The design and three-dimensional consequences of the suggested measures are recommended to study into detail. In addition, the biotic factors and the method of initiation of oyster beds will have to be further investigated to obtain more information about successfully creating oyster beds around an island on the Dogger Bank.

The use of rivers for navigation and the increased human activity along their banks generally requires river control and improvement measures. Most rivers have a natural tendency for continuous change of alignment, e.g. meandering and braiding rivers. Construction of bridges, towns, berths, etc. have required fixation of the river alignment at many places, changing the natural morphology of the rivers. This might lead to bank erosion, erosion around bridge pillars, sedimentation of navigation channels, etc. Adequate measures against this requires a reliable prediction of the morphological changes. For simulating the morphological effects in bends there are two different major factors involved that have been described by several scientists: bed slope effects and spiral flow. For modelling morphological development of a river bend several tests have been done on two different cases that have been researched in a laboratory flume (Delft Hydraulics Laboratory (DHL) and Laboratory of Fluid Mechanics (LFM)) in the 80s. In this research the effects of the major characteristics on the bed development of the bend are examined. This has been done by varying the different input parameters that have influence on the secondary flow and the bed slope effects. Subsequently the varied input files are used to model the same bend with Delft3D 4 Suite, D-Flow FM with an unstructured grid and D-Flow FM with a structured grid. In this way the differences are shown between the different kinds of modelling of the same input parameters. The parameters that have been tuned are Ash, Bsh and Csh for the bedload transport factor that is influencing the bed slope effect. The other parameter is Espir that influence the amount of spiral flow in a bend. The last is αcal that is a multiplication factor in the sediment transport formula from Engelund-Hansen in Delft3D 4 Suite. After optimising these parameters it was not possible to reproduce the flume experiments. Reason for this is probably a simplification in the numerical calculation because with similar parameters of Struiksmas modulation [6] in 1985, which reproduce the flume well, it was still not possible. To improve the reliability of the model it is recommended to study the following aspects: • Improvement of the inflow boundary conditions, to improve the way in which water and sediment flows into the system. • Improvement of the numerical modelling, to create a model that can simulate the characteristics of the river bed in a better way. • Look for test cases which are close to reality to see if the updates in the model are truly simulating the reality. By improving these points, the morphological changes might be predicted in a better way than it is in the current situation. Also it will be possible to have less crashes during the run of simulations.