The purpose of a new nationwide mapping of the seabed is to create a better overview of the geology of the seabed, so that future offshore wind farms can be built on a solid foundation. Offshore wind turbines are large structures that need to be stable for many years, and this requires foundations that can withstand both wind and waves.
The new mapping gives authorities and companies an important tool to assess where the seabed is best suited to support wind turbines, and where further studies or adjustments may be needed.
“The mapping gives us an unprecedented comprehensive understanding of the geological conditions beneath the seabed. This means that decision-makers will know what reservations to have at an early stage. This knowledge can save both time and money in the years to come3,” says project manager from GEUS’ Department of Near-Surface Land and Marine Geology, Chief Consultant Thomas Vangkilde-Pedersen.
First fully comprehensive mapping of the seabed
The mapping covers the entire Danish sea area and shows how thick and widespread the uppermost geological layers are. These layers are typically made up of sand, silt and clay, which were deposited after the Ice Age – the so-called late glacial and Holocene deposits, which are of great importance for how wind turbines can be founded.
The results provide a clear picture of where larger thicknesses of soft sediments occur, and to what extent the geology in an area can be expected to be more uniform or more complex. This means that the report and the webGIS portal can be used as an initial tool for planners, researchers and decision-makers before more detailed studies are initiated.
Previous mapping has often targeted studies of raw material deposits such as sand and gravel and has therefore not given a comprehensive picture of the softer layers that can be problematic in relation to the foundations of offshore wind turbines. The new mapping provides precisely this broad overview and thus provides a solid basis for assessing where new offshore wind turbines can best be located.
A joint project with a focus on smarter planning
The geological screening is part of the overall offshore wind screening that the Danish Energy Agency initiated in 2022 in collaboration with NIRAS, DCE (Aarhus University), DTU Wind and GEUS. The goal is to create a robust data base that can support the political ambition for more offshore wind turbines while at the same time making it possible to consider nature and the environment amongst other things.
Where the environmental and natural science part of the screening points to areas that may be particularly vulnerable, the geological mapping provides a picture of the structure of the seabed. The two parts complement each other and overall provide a stronger basis for identifying suitable offshore wind turbine areas.
Perspectives for the future
The geological mapping also marks an important step towards developing a digital 3D model of the Danish sea areas. Such a model could function as a dynamic digital twin, where geological properties, sediment dynamics and geotechnical parameters can be continuously incorporated and updated.
“With this project, we have come a big step closer to being able to deliver precise digital models of the seabed, which can support both the green transition and future needs for risk assessment and planning,” says Thomas Vangkilde-Pedersen.
Read the report ‘Better geological data for the development of offshore wind – Overall geological mapping of the Danish sea area for the Danish Energy Agency’ (in Danish).
View the map portal.
Read more about the project on the Danish Energy Agency’s website (in Danish).