Scour Potential Evaluation of the Western Irish Sea Mud Belt (Scope)-Paper

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The study assesses seabed scour potential in the Western Irish Sea Mud Belt (WISMB), an area of interest for Ireland’s planned offshore wind development. It combines geological, geophysical and geotechnical survey data with wave observations and multibeam bathymetry of 14 shipwreck sites. Wrecks serve as seabed obstacles analogous to turbine foundations, allowing existing scour patterns to indicate local flow and erosion.<br /><br />The seabed is generally covered by fine-grained, weak marine sediments over glacial deposits. Although tidal currents are often relatively weak and natural scour features are scarce, the shipwrecks show that obstacles can trigger localized erosion. Scour directions at several sites differ from regional tidal-model predictions, suggesting that local hydrodynamics—including a seasonal gyre—can create important variations.<br /><br />Calculations indicate that wave-generated bed shear can exceed the sediment-mobility threshold, particularly from October to March, often without strong currents. In warmer months, currents may also be needed. Introducing a foundation would amplify bed stresses and lower the mobility threshold, making localized scour likely.<br /><br />The authors conclude that scour is a relevant design consideration for offshore wind foundations in the WISMB and that wreck scour signatures could help validate future hydrodynamic and scour models. However, results are preliminary because site-specific wave and current data and sediment samples are limited. They recommend a dedicated metocean survey, repeat bathymetric surveys of selected wrecks, improved local hydrodynamic modelling, and broader sediment sampling before detailed project assessments.

Keywords

seabed scour

Western Irish Sea Mud Belt

offshore wind

shipwrecks

multibeam bathymetry

sediment mobility

hydrodynamics

wave shear

turbine foundations

marine sediments