Ireland has committed to developing a minimum of 3.5GW of offshore wind energy by 2030, which will likely be constructed in the Irish Sea to take advantage of relatively shallow waters in close proximity of the main load centre (Dublin). This study examined the potential for scour susceptibility in the Western Irish Sean Mud Belt (WISMB) which is likely to be relevant to such offshore wind developments. Sediments in the WIMSB are generally fine-grained and geotechnically weak. Existing shipwreck data was used as a proxy for turbine foundations to investigate the scour potential (direction and magnitude) in this area. Previously, it was suggested that the current speeds in the WISMB were insufficient to mobilise sediment and initiate scour. However, this study suggests that wave induced bed stress are sufficient to generate sediment mobility without the necessity of relatively strong tidal currents. The presence of shipwrecks on the seabed in the WISMB can also generate significant amounts of scour with scour signatures revealing variations in localised seabed hydrodynamics which, very often, are at odds with generalised regionalised modelled output. This suggests that local phenomena could have a strong effect on hydrodynamics and, hence, sediment mobility and scour. In this instance, the development of a seasonal gyre in the WISMB could create significant variations in WISMB seabed hydrodynamics. Analysis suggests that the presence of wind turbine foundations would have a significant effect on lowering the sediment mobility thresholds and will likely result in localised scour. The primary conclusion of this study is that there is significant scope for utilising shipwreck scour signatures in verifying future metocean and scour modelling efforts.
P. Doherty, M. Coughlan and S. Creane
Keywords: None provided
Publisher: DFI