Crescent-shape ridges of sands slowly shifting their way across the seabed – known as ‘marine barchan dunes’ – are being studied to explore the potential damage they may cause by their ‘scouring’ of the steel foundations of offshore wind turbines.
This rare type of dune, which on land achieved notoriety for engulfing a Star Wars Movie set in the Sahara, had been spotted during site survey work for a UK offshore wind farm in 2004, but never tracked – partly because the process happens “too quickly to be observed”, according to researchers at HR Wallingford, who used advanced 3D numerical modelling to explore the phenomenon.
The time-lapse visualisation of the site did reveal “some surprising scour pits”, said HR Wallingford senior scientist Kerry Marten, who has led the team researching barchan dunes for the past eleven years. “But luckily for the planning, installation and maintenance of windfarms, [we] did not find that the barchan dune increased erosion.
“And because the scour happened so quickly, there was never any additional sand up against the monopile, keeping the stiffness and the integrity of the foundation fairly constant.”
The research, published in the journal Earth Surface Processes and Landforms, is said to be the most extensive study of its kind and will help advance thinking by offshore wind developers on project lay-out.