In the southern North Sea, a relatively shallow shelf sea, offshore wind farms are being constructed and planned on an extensive scale, upscaling from 20GW in 2020 to 220 GW in 2050.  The wind turbines could alter local hydrodynamics and suspended matter dynamics such that the ecosystem becomes affected. In this study, we present the results of a field campaign aiming at quantifying these changes in hydrodynamics and suspended matter dynamics, allowing the assessment of their ecological impact. The campaign was undertaken in June 2022 in the Belgian Coastal Zone. We measured a set of hydrodynamic parameters at various locations around a single turbine, supplemented with water and sediment samples. The data show how the turbine enhances the local hydrodynamics. In the turbine wake, we observed an increase in turbulent kinetic energy. This led to a more well-mixed water column. At the water surface, this resulted in colder and more saline water, while the water near the seabed became warmer and less saline. These effects were closely linked to the direction of the tidal current, as the turbine-induced wake is only several turbine diameters wide. The wake length is much longer, extending for several hundreds of meters behind the turbine. This presentation discusses the study setup and the steps required to quantify the impact of turbines on local hydrodynamics. Furthermore, we will discuss how this knowledge is implemented in large-scale models, as this step is crucial for assessing the ecosystem impact of upscaled offshore wind installations.

Primary Presenter: Erik Hendriks, Deltares (erik.hendriks@deltares.nl)

Authors:

Kobus Langedock, Flanders Marine Institute - Marine Robotics Centre  (kobus.langedock@vliz.be)

Jan Vanaverbeke, Royal Belgian Institute of Natural Sciences  (jvanaverbeke@naturalsciences.be)

Ulrike Braeckman, Marine Biology Research Group, Ghent University  (ulrike.braeckman@ugent.be)

Luca van Duren, Deltares - Department of Data Science and Water Quality  (luca.vanduren@deltares.nl)

Peter Herman, Deltares - Department of Ecosystem and Sediment Dynamics  (peter.herman@deltares.nl)