Over the recent years, the Dutch Continental Shelf has seen the erection of various wind farms in an effort to counter climate change by replacing fossil-based power plants. Since the majority of these sites use scour protections which have a substantial impact on the surrounding
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Over the recent years, the Dutch Continental Shelf has seen the erection of various wind farms in an effort to counter climate change by replacing fossil-based power plants. Since the majority of these sites use scour protections which have a substantial impact on the surroundings, the Dutch government increasingly stimulates and requires ecological enhancement of such structures in order to restore the natural habitat and maintain the marine ecosystem of the North Sea. Oyster enhancement has been one of the methods used for the ecological enhancement of offshore wind farm scour protections. However, studies report that a successful structure for the harbouring of an oyster population is yet to be developed. Existing structures were found to be unstable or unable to provide a suitable habitat for the oysters (Bouma, Belze, et al., 2013; Stokes et al., 2012). The study at hand aims to develop a successful design for oyster broodstock structures for nature enhancement in offshore wind farms. It was conducted for Van Oord as part of project Ecoscour. To establish design criteria for the oyster broodstock structures, oyster habitats and the Borssele V site were analysed and a brainstorm session with partners from project Ecoscour was set up. The final criteria concerned: ecology; structural integrity; commissioning & construction; and monitoring. The design criteria were used to develop several viable structure designs. In order to rapidly assess the strength and stability of potential designs, a Python-based open source tool was built named Econstruct. With this tool, geometries can easily be evaluated under various influences, accounting for the effect of marine fouling. This could be used for quick investigations of loads, stability and structural integrity. The Econstruct tool was validated and analysed for sensitivity for the input parameters, of which the input radius and current velocity had the highest influence on stability. Using the environmental input parameters that hold for the Borssele V wind farm, a terraced design was proposed. After consultation with the manufacturer of the structure, D & M engineers, this proposal was altered to account for manufacturing limitations. The definitive design was evaluated using the Econstruct tool and found to be stable. It was then manufactured, and ultimately placed in Borssele V in October 2020. Several recommendations are made for future research and the design of ecological enhancement structures for offshore wind farms. Most importantly, the Econstruct open source tool can be used in the future for the design of structures for other ecological enhancement projects such as coral reef restorations.
