Nature enhancing opportunities for an artificial North Sea island

Abstract

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.