Geological and geotechnical constraints in the Irish Sea for offshore renewable energy

Figures & data

Figure 1. Extent of INFOMAR MBES bathymetry data used in this study (A) and same data gradated to 0–40 m (shallow), 40–60 m (transitional) and >60 (deep) representing preferred ranges for technology types (B).

Figure 2. Parameters derived from bathymetric data: (A) rugosity and (B) slope greater than significant gradient threshold (i.e. > 5°).

Figure 3. Parameters derived from bathymetry using ArcGIS Benthic Terrain Modeler: (A) broad-scale BPI and (B) fine-scale BPI.

Figure 4. Backscatter (A) and sediment classification (B) data available from INFOMAR used in this study.

Figure 5. Profile A-A’-B in Figure 8 with annotated features.

Figure 6. Seabed sediment distribution in the Irish Sea (modified Folk (1954) classification) with superimposed morphological features (according to Dove et al., 2016), sediment wave direction (Van Landeghem et al., 2009), bedload parting zones (Van Landeghem et al., 2009) and indicative, average bedform migration rates (Van Landeghem et al., 2012).

Table 1. Geological features creating possible geotechnical constraints in the Irish Sea (after Mellet et al., 2015)

Geological Feature	Potential Constraint
Soft sediments	Low shear strengths affecting bearing capacity Implications for differential settlement Prone to scour
Coarse-lag deposits	High levels of lateral heterogeneity with coarse, hard substrates that are difficult to penetrate.
Mobile sediment	Can bury structures Can erode sediment at the base of structures causing instability (e.g. scour) Affects seabed levels
Shallow gas	Affects seabed instability (e.g. pockmark formations) and long-term behaviour of sediments (e.g. differential settlement) Can create hard substrates at surface (i.e. MDAC)
Over-consolidated sediments	Hard substrate restrictive to some foundation types
Bedrock	Hard substrate restrictive to some foundation types

Figure 7. Geological and geotechnical constraints mapped in the Irish Sea superimposed on OREDP assessment areas.

Figure 8. Geomorphological classification of the Irish Sea INFOMAR data using the classification scheme of Dove et al. (2016).

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