Monopile-induced turbulence and sediment redistribution form visible wakes in offshore wind farms

Bailey, Lewis P.; Dorrell, Robert M.; Kostakis, Ina; McKee, David; Parsons, Dan; Rees, Jon; Strong, James ORCID: https://orcid.org/0000-0001-8603-097X; Simmons, Stephen; Forster, Rodney. 2024 Monopile-induced turbulence and sediment redistribution form visible wakes in offshore wind farms. Frontiers in Earth Science, 12. 10.3389/feart.2024.1383726

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Text © 2024 Bailey, Dorrell, Kostakis, McKee, Parsons, Rees, Strong, Simmons and Forster. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. feart-12-1383726.pdf - Published Version Available under License Creative Commons Attribution 4.0. Download (82MB) | Preview

Abstract/Summary

Offshore wind farms are becoming an increasingly common feature in the marine environment as a renewable energy source. There is a growing body of evidence on the effects of wind farms on the seabed and its organisms. However, an important and understudied aspect of site development is the interaction of turbine foundations on the surrounding marine environment. Structures exert significant disturbance on tides, waves and currents; these are visible as optically-distinct, elongate wakes at the sea surface with elevated suspended particulate matter. Despite this, there is uncertainty on the mechanisms that lead to the visible manifestation of wakes at turbine foundations, primarily due to a lack of direct measurements. Here, in situ measurements along with a 15-year time series of satellite images of the Thanet offshore wind farm, located within the Thames Estuary, were used to investigate the formation of visible monopile wakes, and the effects these have on the surrounding water column. We show the optically distinct wakes are near-constant at Thanet; visible in >90% of all satellite images, yet no regional change in sea surface turbidity could be attributed to wind farm construction or operation. Monopile wake in situ water samples and acoustic Doppler current profiler (ADCP) backscatter measurements demonstrated colour change related to elevated sea surface sediment concentration. However, averaged water column measurements of suspended sediment within wakes, and upstream of monopiles, remained consistent. These measurements demonstrate that sediment was redistributed towards surface waters, rather than additional sediment becoming suspended in the wake. ADCP velocity measurements supported a mechanism of sediment lofting towards the surface, with enhanced vertically upwards flow recorded in wakes.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.3389/feart.2024.1383726
ISSN:	2296-6463
Additional Keywords:	offshore wind farms, hydrodynamics, turbid wakes, suspended particulate matter, in situ measurements
Date made live:	03 Sep 2024 17:40 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/537955

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