Publication - Publication

Offshore wind energy - draft sectoral marine plan: strategic environmental assessment

Published: 18 Dec 2019
Directorate:
Marine Scotland Directorate
Part of:
Energy, Marine and fisheries
ISBN:
9781839603761

Strategic environmental assessment (SEA) identifies the likely significant environmental impacts of plans and policies and proposed reasonable alternatives to them.

305 page PDF

12.4 MB

305 page PDF

12.4 MB

Contents
Offshore wind energy - draft sectoral marine plan: strategic environmental assessment
5 Results of SEA

305 page PDF

12.4 MB

5 Results of SEA

5.1 Stage 1: Wind Energy Technologies

5.1.1 A review of the currently operational and future technologies, including the offshore transmission infrastructure, has been undertaken, and potential environmental effects associated with the construction, operation, maintenance and decommissioning phases identified.

5.1.2 The reviewed technologies are:

  • Wind technologies with gravity-base foundation devices (bottom fixed);
  • Wind technologies with monopile or multi-pile foundation devices (bottom fixed);
  • Wind technologies with tripod of steel jacket foundation devices (bottom fixed);
  • Wind technologies with mono or multi-caisson foundation devices (bottom fixed); and
  • Floating wind turbines, including turbines with both gravity and piled anchors.

5.1.3 The reviewed transmission technologies are:

  • Offshore transmission infrastructure components;
  • Subsea transmission cables; and
  • Landfall and transition pit.

5.1.4 The full results are presented in Appendix B. A summary of the key effects of both conventional bottom fixed technologies and floating technologies is presented below against each topic. The key effects are generally similar between all technologies, with the largest differences between fixed bottom and floating wind regarding effects on benthic habitat, and potential reductions in the amount or size of piling required during construction.

Biodiversity, Flora and Fauna

5.1.5 The pathways discussed below were informed by Halcrow [186], Talisman Energy [187], EMU [188], Aberdeen Wind Offshore Wind Farm Limited [189] and E-on [190] [191] [192] and could potentially alter biodiversity, flora and fauna.

Benthic habitats and species

5.1.6 There is the potential for habitat loss or disturbance to benthic communities during installation, decommissioning and continued disturbance during operation due to maintenance and repair activities. This could be especially detrimental to sensitive/designated habitats such as reefs and their associated species which may take time to recover. Seabed habitat would be lost from the placement of devices and support structures on the seabed required by any of the turbine technologies. Gravity-base foundations would potentially have the greatest negative effect by directly placing large blocks on/into the seabed. There is also the potential for adverse effects from sourcing of fill or dredged material for use in the gravity-based foundation. This could potentially affect marine fauna from dredging activities, turbidity and habitat disturbance. Floating technologies would have the smallest effect, with the loss of small, discreet areas of benthic habitat associated with the placement of gravity anchors significantly smaller than that associated with fixed bottom technology. However, chains attaching the floating structures to the seafloor should also be considered because they may have an effect over a much wider area and would be a continual disturbance during operation. There are also potential effects on benthic invertebrates from noise and induced electromagnetic fields associated with operational cables.,

5.1.7 Seabed disturbances from cable installation activities are considered temporary and have a relatively limited effect through resuspension of sediments, loss of habitat, trenching in intertidal environments and potential damage to stony or rocky reef in areas of hard substrate. where cables are buried, it is generally anticipated that the seabed will return to its original state, however impacts from cable installation should nonetheless be mitigated so far as is reasonably practicable through careful route selection and appropriate installation techniques.

5.1.8 Indirect adverse effects to benthic habitats may also occur. Particularly sensitive habitats such as shellfish growing waters or fish spawning grounds could be damaged from sediment dispersion and deposition in the construction and decommissioning phases of work.

5.1.9 It is anticipated that many of the construction and decommissioning effects may be temporary and reversible (i.e. removal of the gravity base structure, support structures, caissons or gravity anchors and rehabilitation of the seabed).

5.1.10 Wind turbines, of any technological design, have the potential for creating artificial habitats for marine organisms resulting from the presence of new structures. These may provide benefits which could last for the life of the project, or potentially longer depending on the decommissioning scheme. This impact pathway may lead to fish aggregation effects around turbine foundations and structures which in turn may lead to possible impacts on trophic food webs for fish species, marine mammals and birds. These impacts have the potential to be both beneficial or adverse[193].

5.1.11 There could also be a positive change from the reduction in commercial fishing (e.g. trawling) in areas where wind farms are sited, which may enhance biodiversity.

Marine mammals and fish

5.1.12 The underwater noise and vibration created during surveys, clearance of unexploded ordnance, installation and decommissioning for any of the offshore wind technologies, has the potential to affect marine fauna such as seals, otters, cetaceans, fish and basking sharks, potentially including fish associated with aquaculture installations. There will be a difference in magnitude between the different technologies as the technologies which involve piling will have a greater noise and vibration effect. There is also the possibility for cumulative effects from multiple noise sources audible to marine mammals and fish during installation and increased vessel disturbance.

5.1.13 Relating to all the technologies, there is the possibility of habitat loss, exclusion, displacement or disturbance of marine mammals and fish during device installation, operation and decommissioning. This would occur through a combination of factors including noise (and multiple noise sources), vibration, visual and light intensity changes, water quality changes, habitat disturbance or the increased presence of structures and vessels. This could be particularly detrimental to bottom dwelling species such as sandeel, which are important prey species for birds, marine mammals and fish.

5.1.14 Spawning and nursery grounds could also be affected by habitat loss and disturbance during installation, maintenance and decommissioning phases of development. Anthropogenic noises, vibrations from pile driving, water quality changes and light intensity changes all pose a threat to spawning and juvenile fish.

5.1.15 There is also the possibility of increased suspended sediment during construction and decommissioning causing sediment deposition affecting bottom dwelling and spawning species such as sandeel or fish associated with aquaculture installations.

5.1.16 Similarly, with regard to all offshore wind technologies, there is a potential risk of injury to marine mammals through collisions with submerged structures and associated cabling or effects during the installation, maintenance and decommissioning periods (i.e. risk of injury to seals and cetaceans during placement of foundations).

5.1.17 There is the potential for induced electromagnetic fields (EMF) associated with cabling and grid connection infrastructure to affect the behaviour and migratory patterns of some fish and mammal species. The noise during the construction and decommissioning phases could cause behavioural responses, displacement from natural habitats and feeding areas, physical injuries to hearing organs and potentially lethal effects.

5.1.18 Cumulative effects may also occur, particularly affecting mammals and migratory fish, which have the potential to be present throughout Scottish waters, from an increased number of barriers affecting movement such as device arrays, construction vessels and equipment.

5.1.19 Positively, artificial rocky habitats could potentially be created due to the presence of submerged infrastructure[194].

Birds

5.1.20 A number of studies have investigated the collision risks to birds from offshore wind turbines [195] [196] [197] [198] [199] [200] [201]. Many of these studies agree that collision risk is influenced by various factors but is largely driven by the proportion of birds flying at collision risk height [202].

5.1.21 Some bird species are considered to be at a lower risk of collision as they typically fly at low altitudes (above the sea surface and below the swept area of the turbines)[203]. However, other bird species (such as large gulls and Gannets) have a higher potential collision risk, as they typically fly at higher altitudes and travel large distances between breeding and wintering grounds. For example, 35% of Herring Gull flights have been recorded at blade height[204].

5.1.22 Other research suggests that birds adapt their flight paths to avoid collision with turbines[205] with generally very high avoidance of turbines exhibited by seabirds [206]. WWT [207] has indicated that most seabirds are not expected to be at risk because of these avoidance rates, while work by Cook et al.[208] suggested that birds rarely pass close to the rotor blades. The ORJIP Bird Collision Avoidance Study compiled an extensive dataset of observations of bird behaviour in and around an operational offshore wind farm, concluding that the target species (Northern Gannet, Lesser Black-backed Gull, Herring Gull, Great Black-backed Gull and Black-legged Kittiwake) "exhibit behaviour that significantly reduces risk of those seabird species colliding with rotating turbine blades than would otherwise be the case if there was no change in behaviour"[209].

5.1.23 Diving birds could potentially collide with support devices (i.e. mooring cables or anchors if used for floating technologies). However, this is likely to be site and device-specific, and the likelihood of occurrence is not currently known.

5.1.24 Furthermore, there is the potential to disturb diving birds foraging areas during installation, operation and decommissioning due to underwater noise, surface noise, visual and light intensity changes, water quality changes, habitat disturbance or the presence of structures and vessels.

5.1.25 Seabirds could also be affected by offshore transmission infrastructure components. Installation, maintenance and decommissioning activities could potentially cause a loss of prey species in offshore feeding grounds leading to increased foraging distances or reducing foraging success. There is also the potential for displacement of bird species from offshore foraging areas to other areas due to disturbance during the construction, maintenance and decommissioning phases.

Population and Human Health

5.1.26 The pathways discussed below were informed by Halcrow [210], Talisman Energy [211], EMU [212], Aberdeen Wind Offshore Wind Farm Limited [213] and E-on [214] [215] [216] and could potentially alter population and human health.

5.1.27 All the offshore wind turbine technologies would provide a new renewable energy supply for the life of the development. Therefore, the potential effects on energy supply are the same across the different technologies.

5.1.28 There is the possibility of shadow flicker and noise effects, particularly if the array is located near-shore.

5.1.29 Other marine users (i.e. fishing, recreational, shipping, aquaculture) could be affected by the development of a wind farm. This could include the potential displacement of these activities, the risk of collision with turbine structures, and visual effects associated with the presence of the turbines. Upon decommissioning, these effects are likely to be reversible.

5.1.30 There is the potential for issues with navigation, although it is noted that this may be managed through the selection of appropriate sites and consultation with the Maritime and Coastguard Agency (MCA) to ensure that there are no unacceptable risks to commercial or recreational shipping.

5.1.31 Recreational and commercial activities could be affected by the installation of new transmission infrastructure to connect the devices to the grid (i.e. cables on the seabed, terrestrial infrastructure). Potential effects are likely to be site and development specific.

5.1.32 Construction vessels, cable excavation vessels, maintenance activities and helicopter flights may affect other marine user's transit routes (e.g. dredging, oil and gas operations and freight), increasing navigational risk, particularly during the installation, maintenance and construction phases.

5.1.33 There is also the potential for interference with communications due to EMF.

Soil (Marine Geology and Coastal Processes)

5.1.34 The pathways discussed below were informed by OSPAR [217], Halcrow [218], Talisman Energy [219], EMU [220], Aberdeen Wind Offshore Wind Farm Limited [221] and E-on [222] [223] [224] and could potentially alter marine geology and coastal processes.

5.1.35 There is the potential that any of the technologies could have a direct adverse effect to the seabed from the installation, operation or decommissioning processes. There will be a difference in magnitude between the technologies depending on their location. Gravity-base and mono or multi-caisson foundations involve preparation of the seabed (dredging) and then the placement of heavy foundations and associated scour protection, technologies with monopile or multi-pile and tripod or steel jacket foundations require piling operations and floating technologies need anchors and moorings placed directly on the seabed, or could involve the use of piles.

5.1.36 All the technologies could potentially alter the sediment dynamics, tidal flows/fluxes and waves due to the presence of devices in the water column.

5.1.37 Effects such as deposition and abrasion may also occur due to the installation and decommissioning processes. The effects of scouring will primarily happen during the operational phase. However, there is the possibility of using scour protection for gravity-base and mono or multi-caisson foundation structures to alleviate risks. Scour protection creates an additional footprint, so it would only be used where it is considered necessary. Deeper water locations would be less likely to need scour protection.

5.1.38 Effects from construction and decommissioning works, for all the technologies, are likely to be temporary. Also, the effects from seabed preparation works for gravity-base foundations and mono or multi-caisson foundations are likely to be temporary because they are usually required in geomorphologically active areas.

5.1.39 Gravity-base foundations have additional effects due to the sourcing of fill or dredged material to fill their base. If marine fill or dredged material is used, potential effects at the source may include: loss of substrata or habitat if taken from suitable undisturbed areas; and potential effects on hydrodynamics and water flows at the source location from the removal of sediments. If material is sourced from the terrestrial environment it will have effects associated with the removal of material and its transportation.

Water Quality

5.1.40 The pathways discussed below were informed by Halcrow [225], Talisman Energy[226], EMU [227], Aberdeen Wind Offshore Wind Farm Limited [228] and E on[229] [230] [231] and could potentially alter water quality.

5.1.41 There is a potential effect on water quality during the installation, operation and decommissioning processes, from all of the technologies, due to increased turbidity, seabed disturbance and contamination from installation, maintenance and decommissioning equipment and vessels. It is likely the magnitude of the effects will differ between the technologies. The placement of gravity-based supports and concrete foundations for the placement of caissons will have different effects on water quality compared to piling activities. The associated effect on marine biodiversity, particularly those dependent on existing water conditions such as benthic species (e.g. filter feeders) is likely to be site specific. Cable installation will also alter the water quality by re-suspending seabed sediments into the water column, increasing turbidity levels. The level of disturbance largely depends on the equipment being used, but the majority of sediment deposition would occur in a relatively restricted area. There is also the possibility of remobilising contaminants, especially if the cable route passes through areas of muddy sediment with high levels of anthropogenic activity.

5.1.42 There is potential for the requirement of dredged material for gravity base foundations, which may affect water quality through increased turbidity from sediment disturbance during dredging operations.

5.1.43 The construction and decommissioning effects are temporary and may be reversible, and this is true for all technologies.

5.1.44 The development of offshore transmission infrastructure, subsea transmission cables and landfall and transition pits all have the potential to impact similarly on water quality. This includes having the potential to cause the re-suspension of sediments and their associated hazardous substances due to excavation during installation and major repair activities, and the potential to cause accidental spillages from construction vessels and structures during operation. During construction, maintenance and decommissioning activities there is potential for water contamination from oil or other harmful substances. This would have associated risks to humans and riparian ecology. There is the potential for sedimentation and increased turbidity of watercourses in areas where vegetation has been cleared.

Climatic Factors

5.1.45 The pathways discussed below were informed by Halcrow [232] and could potentially alter climatic factors.

5.1.46 All the technologies would bring benefits due to their contribution to renewable electricity generation. The extent of the benefits would depend on the scale and duration of developments. However, it is also important to note the possible effect on blue carbon. Habitats such as sea grass meadows, salt marshes and maerl beds are valuable carbon sinks and if they are degraded or damaged by offshore wind developments and their carbon sink reduced, the resulting increase in CO2 emissions will contribute to further climate change.

5.1.47 Construction vessel and vehicle emissions used to complete the transmission infrastructure have the potential to affect air quality, and subsequently human health, and contribute to greenhouse emissions.

Cultural Heritage

5.1.48 The pathways discussed below were informed by Fjordr Marine and Historic Environmental Consulting[233], Halcrow[234], Talisman Energy[235], EMU[236] and E-on[237] [238] [239] [240] and could potentially alter cultural heritage.

5.1.49 There is the potential for installation, operation and decommissioning to affect known historic sites and their exclusion zones, including World Heritage Sites, coastal listed buildings such as lighthouses, scheduled monuments and other unknown, submerged or non-designated archaeological assets features or paleo-landscapes. Development has the potential to directly disturb, damage or destroy submarine and coastal archaeological remains during device installation and cable trenching. There is also potential for scouring, siltation and deposition to occur around culturally important sites located in the vicinity of developments.

5.1.50 However, adverse effects are can be avoided through careful siting of individual device foundations, piles, anchors and arrays.

5.1.51 There is the potential for the offshore transmission infrastructure to cause loss of or damage to known or unknown buried heritage from construction and maintenance/repair activities.

Landscape, Seascape and Visual Amenity

5.1.52 The pathways discussed below were informed by OSPAR [241], Halcrow [242], Talisman Energy [243], EMU [244], Aberdeen Wind Offshore Wind Farm Limited [245] and E-on [246] [247] [248] and could potentially alter the landscape, seascape and visual amenity.

5.1.53 There is the potential for turbines and their supporting infrastructure (i.e. additional platforms, construction, maintenance or decommissioning vessels and equipment) associated with any of the offshore wind technologies, to adversely affect sensitive landscape and visual receptors such as designated or valued landscapes/seascapes. In general, greater effects are likely for near-shore devices than those located further offshore and for larger turbines (with greater height and thus greater visibility).

5.1.54 Field observations of offshore wind facilities in the United Kingdom revealed that the turbines may be visible at distances of 26 mi (42 km) in daytime and 24 mi (39 km) in night-time. They may be a focus of visual attention at distances of up to 10 mi (16 km)[249]. These distances will be influenced by the turbine height, with smaller turbines less visible / intrusive to landscape or seascape receptors. The shape of arrays relative to the coastline also influences visual impact. Similarly assessments undertaken for the Natural Resources Wales[250] have concluded that the 15 km is the maximum distance of medium effect for the smallest offshore wind turbines likely to be constructed.

5.1.55 Within 15 km it has therefore been assumed that there is less potential for avoidance of significant effects with a correspondingly higher assessment of effect, whereas beyond this distance there is potential for mitigation through spatial planning, array design and turbine selection, with post-mitigation assessments reduced based on this assumption.

5.1.56 Onshore and offshore transmission infrastructure components also have the potential to alter the landscape and seascape respectively. Construction activities, including temporary lighting and construction plants may temporarily affect visual receptors.

5.2 Potential Environmental Effects of Development within the DPOs

5.2.1 An assessment of the potentially significant environmental effects of development within each DPO has been undertaken, based on the indicative realistic maximum scales of development. The full results of this assessment are presented in Appendix C and summarised against each topic below and in Table 8.

5.2.2 The assessment is technology neutral, in that no distinction has been made at individual sites to prejudge the likely technology. Therefore, for the purposes of the assessment, the worst-case scenario has been determined, noting where there are differences between technologies or array design that have the potential to reduce the severity of effects. Where this is the case, and the level of mitigation likely to be applied at a certain site is uncertain, a range of effect classification (e.g. negligible to minor negative) has been used to highlight this uncertainty.

5.2.3 It is recognised that this assessment is therefore likely to be precautionary, and that in some cases project level design and mitigation strategies have the potential to further reduce effects below those identified in Appendix C.

5.2.4 Table 8, presents the overarching results of the assessment against the identified pathways:

1. Loss of and/or damage to marine and coastal habitats, including benthic and intertidal habitats (for example, due to smothering of benthic habitats and substratum loss).

2. Effects on key mobile receptors and prey species, including disturbance, noise effects, EMF exposure, collision risk, habitat exclusion, and barriers to wildlife movement.

3. Effects arising from habitat modification, such as the creation of artificial reefs, new roosting structures and exclusion of habitat damaging activity.

4. Effects of pollution releases on species and habitats.

5. Effects from introduction and spread of Invasive Non-Native Species (INNS).

6. Effects arising from noise, vibration, light, dust and shadow flicker effects from all phases of development.

7. Effects on residential amenity stemming from construction/installation/operational activities.

8. Issues of navigational safety, aviation and collision risk.

9. Effects on marine and coastal recreation and access

10. Development of a secure energy supply.

11. Effects on subsea geology, sediments, and coastal processes arising from changes in hydrodynamics and the existing wave regime.

12. Effects on ecological status.

13. Effects on water quality (for example, due to increases in suspended sediment loads and turbidity as well as an increase in pollution incidents).

14. Effects of the presence of structures on local currents, wave regimes, and water column mixing, as well as secondary effects on sedimentation and erosion beyond the sites.

15. Contribution to supporting a diverse and decarbonised energy sector.

16. Coastal facilities may be at risk from climate change.

17. Loss of and/or damage to historic environment features and their settings, including coastal and marine archaeology and historic MPAs.

18. Both temporary and longer-term effects on landscape and coastal character and visual receptors arising from the presence of structures including any ancillary infrastructure.

5.2.5 It is recognised that some effects against the identified pathways will be generic across sites, as the effects relate to the introduction of structures, irrelevant of technology or environmental receptors present. Where these pathways present the highest risk in a specific DPO and are hence included in the summary against that site, the text below recognises that these effects are generic and will be present against all sites.

Table 8 Summary of the results of the assessment against DPOs (see key table below for explanation of symbology)

Topic Biodiversity, Flora and Fauna Population and Human Health Soil Water Climatic Factors Cultural Heritage Landscape, Seascape and Visual Amenity
Pathway 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
SW1 -/-- -/-- ~ ~ - N/E N/A -/--- N/A ++/+++ -/-- ~/- - -/-- ++/+++ N/E ~/- --/---
W1 -/-- -/-- ~ ~ - - N/A - N/A ++/+++ ~/- ~/- - ~/- ++/+++ N/E ~/- ~/---
N1 - -/-- ~ ~ - N/E N/A -/--- N/A ++/+++ ~/- ~/- - ~/- ++/+++ N/E ~/- ~/-
N2 ~/- ~/- ~ ~ - N/E N/A ~/- N/A ++/+++ ~/- ~/- - ~/- ++/+++ N/E ~/- ~/-
N3 ~/- ~/-- ~ ~ - N/E N/A ~/- N/A ++/+++ ~/- ~/- - ~/- ++/+++ N/E ~/- ~/-
N4 - ~/- ~ ~ - -/--- N/A -/-- N/A ++/+++ ~/-- ~/- - ~/-- ++/+++ N/E ~/- --/---
NE1 -- -/-- ~ ~ - N/E N/A ~/- N/A ++/+++ ~/-- ~/- - ~/-- ++/+++ N/E ~/-- ~/-
NE2 ~/- -/--- ~ ~ - N/E N/A ~/- N/A ++/+++ ~/- ~/- - ~/- ++/+++ N/E ~/- ~/-
NE3 ~/- -/--- ~ ~ - N/E N/A -/-- N/A ++/+++ ~/- ~/- - ~/- ++/+++ N/E ~/- ~/-
NE4 ~/- -/--- ~ ~ - N/E N/A --/--- N/A ++/+++ ~/- ~/- - ~/- ++/+++ N/E ~/- ~/-
NE5 ~/- -/--- ~ ~ - N/E N/A -/-- N/A ++/+++ ~/- ~/- - ~/- ++/+++ N/E ~/- -/--
NE6 - -/--- ~ ~ - N/E N/A --/--- N/A ++/+++ ~/- ~/- - ~/- ++/+++ N/E ~/- ~
NE7 - -/-- ~ ~ - N/E N/A ~/- N/A ++/+++ ~/- ~/- - ~/- ++/+++ N/E ~/- N/E
NE8 - -/-- ~ ~ - N/E N/A ~/- N/A ++/+++ ~/- ~/- - ~/- ++/+++ N/E ~/- N/E
E1 - -/-- ~ ~ - N/E N/A ~/- N/A ++/+++ ~/- ~/- - ~/- ++/+++ N/E ~/- N/E
E2 - -/-- ~ ~ - N/E N/A -/-- N/A ++/+++ ~/- ~/- - ~/- ++/+++ N/E ~/- N/E
E3 - --/--- ~ ~ - N/E N/A -/--- N/A ++/+++ ~/- ~/- - ~/- ++/+++ N/E ~/- ~/-

Term Description

+++ Major Positive
++ Moderate Positive
+ Minor Positive
~ Negligible Effect
- Minor Negative
-- Moderate Negative
--- Major Negative
N/E No Effect – There is no effect pathway from source to receptor
N/A Not Assessed – Effect pathway cannot be assessed due to uncertainties regarding cable landfalls or is assessed in the SEIA and / or within another pathway, for further details see Appendix C.

Key impacts considered against each DPO

South West

SW1

5.2.6 Within SW1, the key pathways which may constrain development are:

  • Biodiversity, flora and fauna, particularly potential effects on Whooper Swan migration pathways and potential impacts on harbour porpoise from the North channel SAC;
  • Navigational safety, both for commercial shipping and recreational boating;
  • Sediment transport and coastal processes; and
  • Visual effects on landscape / seascape.

5.2.7 There is potential to mitigate most of the effects of the above pathways, principally through spatial planning and array design at a project level. Further research, including development of the baseline through survey, and consideration of specific mitigation, such as selection of specific turbine heights may be required to reduce effects on Whooper Swan or other species' migration pathways.

5.2.8 The proximity of the DPO to land does, however, limit the degree that spatial planning can be used to mitigate against effects on landscape or seascape.

5.2.9 There is considerable uncertainty regarding the potential cable routes from SW1, therefore no meaningful assessment can be made. Export cable planning will be required to take into consideration sensitive areas at a project level. Inshore of SW1 there are a number of sensitive habitats including SAC directly landwards of SW1 in Luce Bay and Solway Firth and SPA in the Solway Firth.

West

W1

5.2.10 Within W1, the key pathways which may constrain development are:

  • Biodiversity, flora and fauna, particularly potential effects on benthic habitat and displacement or barrier effects on marine mammals, birds and fish;
  • Sediment transport and coastal processes; and
  • Visual effects on landscape / seascape.

5.2.11 It is recognised that development in the east and south east of the DPO is likely to have more significant effects on biodiversity than in the west and north west, due to higher usage of the area by grey seal and bird species which may be displaced or be at risk of collision or noise effects. Additionally, the south east of the site is closest to land, and hence will have higher visual effects. Potential impacts on basking shark have the potential to be distributed throughout the DPO, but are likely to be greatest during July and August.

5.2.12 There is potential to mitigate all the effects of the above pathways, and further lower impact pathways, through spatial planning, temporal planning, and array design at project level.

5.2.13 There is therefore potential to mitigate biodiversity and community effects at a plan level by excluding development from the east and south-east; and to mitigate navigational risk by excluding development from the western boundary.

5.2.14 There is considerable uncertainty regarding the potential cable routes from W1, therefore no meaningful assessment can be made. Export cable planning will be required to take into consideration sensitive areas at a project level. Inshore of W1 there are a number of sensitive habitats including SAC to the north and east of the DPO, and SPA to the south and east.

North

N1

5.2.15 Within N1, the key pathways which may constrain development are:

  • Biodiversity, flora and fauna, particularly potential effects on bird populations including foraging in the west of the DPO from the Sule Kerry and Sule Stack SPA and Kittiwake from Orkney; and
  • Navigational safety, both for commercial shipping and recreational boating.

5.2.16 Bird usage of the site is concentrated to the western and eastern sectors of the DPO, and as such additional research and subsequent spatial planning at a project level may be required to avoid areas of key usage for bird species, particularly those associated with the SPA. In addition, specific mitigation, such as selection of specific turbine heights, may be required to reduce effects on bird species' migration pathways where they are identified in pre-consent surveys.

5.2.17 Spatial planning can also be used to avoid key commercial shipping and recreational boating routes within the site to allow safe transit, and further mitigate other pathways at a project level.

5.2.18 There is considerable uncertainty regarding the potential cable routes from N1, therefore no meaningful assessment can be made. Export cable planning will be required to take into consideration sensitive areas at a project level. Inshore of N1 there are a number of sensitive habitats, however the distance of the DPO from land should allow cable planning to avoid areas of particularly sensitive habitats based on surveys of potential cable routes.

N2

5.2.19 N2 is generally an area of lower constraint, with the most significant pathways (assessed as minor effects after mitigation) associated with risks of spread of invasive species and effects on water quality from sediment disturbance during construction or pollution events associated with increases in shipping to service developments within the DPO.

5.2.20 These risks are applicable to all developments and are not specific to N2. They can be managed through the licencing process at a project level, including requirements to produce biosecurity management plans, pollution management plans and sediment contamination testing where significant disturbance is anticipated.

5.2.21 In addition, there is potential for minor effects on biodiversity, navigational safety, soil, water, visual receptors and cultural heritage receptors in N2, however these are considered to have the potential to be mitigated to a negligible level through project level assessment and planning.

5.2.22 Similarly, there are potential effects from export cable pathways, therefore no meaningful assessment can be made. Export cable planning will be required to take into consideration sensitive areas at a project level. Directly to the east of the DPO is the Solan bank reef SAC which should be avoided in project level cable planning and survey of potential cable routes should identify any sensitive areas which should be avoided.

N3

5.2.23 Within N3, the key pathway which may constrain development is:

  • Biodiversity, flora and fauna, particularly potential effects on bird species foraging in the northeast section of the DPO from the North Rona and Sula Sgeir SPA and migrating species whose pathways intersect N3;

5.2.24 There is potential to mitigate the effects of the above pathway and other lower impact pathways through spatial planning and array design at a project level. Further research and consideration of specific mitigation may be required to reduce effects on bird species' foraging areas and migration pathways.

5.2.25 There is considerable uncertainty regarding the potential cable routes from N3, therefore no meaningful assessment can be made. Export cable planning will be required to take into consideration sensitive areas at a project level. Inshore of N3 there are few designated sensitive habitats, however survey of potential cable routes should identify any sensitive areas which should be avoided.

N4

5.2.26 Within N4, the key pathways which may constrain development are:

  • Effects on population from noise during construction;
  • Navigational safety, both for commercial shipping and recreational boating; and
  • Visual effects on landscape / seascape.

5.2.27 There is potential to mitigate the effects of the above pathways, principally through array design and technology selection at a project level. The most significant effects are to population receptors and are associated with the proximity of the DPO to land. Airborne noise effects could be mitigated through choice of foundation design. Visual effects could be mitigated in part through choice of turbine size. However, given the proximity to land and the presence of a National Scenic Area (NSA) approximately 10 km to the south, turbines of any size will be visible, and therefore affect landscape / seascape character. The extent of the constraint to development regarding this receptor will likely be significantly influenced by the opinions of local stakeholders.

5.2.28 There is considerable uncertainty regarding the potential cable routes from N4, therefore no meaningful assessment can be made. Export cable planning will be required to take into consideration sensitive areas at a project level. Inshore of N4 there are few designated sensitive habitats, however survey of potential cable routes should identify any sensitive areas which should be avoided.

North East

NE1

5.2.29 Within NE1, the key pathways which may constrain development are:

  • Biodiversity, flora and fauna, particularly potential effects on benthic habitat, spawning fish, including herring, cod and whiting, and displacement of marine mammals, birds and fish; and
  • Sediment transport and coastal processes.

5.2.30 It is recognised that the development in the east of the DPO is likely to have more potential for significant effects on biodiversity, flora and fauna, due to proximity to the Pobie Bank SAC which adjoins the DPO, designated for benthic habitats including encrusting bryozoans and deep sea sponge aggregations. Although the features within the site are non-mobile, there is potential for some examples of the features to be present within the DPO and therefore have potential to be impacted directly by the footprint of the turbines or the cable route. In addition, there is potential for sediment transport to directly affect features within the SAC, through smothering or increased scour associated with the turbines. There are also large populations of bird species on Shetland, some of which may forage further offshore into areas overlapping the DPO.

5.2.31 There will be a requirement to determine the effects of any development on the SAC features through sediment and hydrodynamic modelling at a project level and there is potential to mitigate all the effects of the above pathways, and further lower impact pathways, through spatial planning and turbine or array design at project level.

5.2.32 Risks to spawning fish can be mitigated through temporal restrictions on piling activity to avoid key spawning times.

NE2

5.2.33 Within NE2, the key pathway which may constrain development is:

  • Biodiversity, flora and fauna, particularly potential effects on bird species through displacement or physical injury, effects on bird migration pathways and effects on spawning herring from underwater noise.

5.2.34 There is potential to mitigate the effects of the above pathway and other lower impact pathways through spatial planning and array design at a project level. RSPB distribution data suggests that a number of bird species, including Kittiwake foraging from the breeding colony at Copinsay SPA, are likely to utilise the waters within and around the DPO and may thus be affected during all phases of wind farm development.

5.2.35 Recent wind farm project assessments (e.g. Moray West) have raised particular concerns from statutory stakeholders with regard to the potential effects from collision and displacement on several seabird species' populations. These concerns, discussed further under cumulative effects below in Section 0, have the potential to constrain development within NE2. This level of constraint is likely to remain until such a time that further evidence, research and knowledge around mitigation is available to support development in the region.

5.2.36 Risks to spawning fish can be mitigated through temporal restrictions on piling activity to avoid key spawning times.

5.2.37 There is considerable uncertainty regarding the potential cable routes from NE2, therefore no meaningful assessment can be made. Export cable planning will be required to take into consideration sensitive areas at a project level. Inshore of NE6 there are a number of sensitive habitats including numerous SPA around the Orkney Islands.

NE3

5.2.38 Within NE3, the key pathways which may constrain development are:

  • Biodiversity, flora and fauna, particularly potential effects on bird species through displacement or physical injury, effects on bird migration pathways and effects on spawning herring and sandeel from underwater noise; and
  • Navigational safety, due to close proximity to major commercial shipping routes from Aberdeen and Peterhead regions to Orkney and towards Iceland.

5.2.39 There is potential to mitigate the effects in relation to commercial shipping and other lower impact pathways through spatial planning and array design at a project level.

5.2.40 As for NE2, concerns regarding effects on seabird populations, discussed further under cumulative effects below in Section 0, have the potential to constrain development within NE3. This level of constraint is likely to remain until such a time that further evidence, research and knowledge around mitigation is available to support development in the region.

5.2.41 Risks to spawning fish can be mitigated through temporal restrictions on piling activity to avoid key spawning times.

5.2.42 There is considerable uncertainty regarding the potential cable routes from NE3, therefore no meaningful assessment can be made. Export cable planning will be required to take into consideration sensitive areas at a project level. Inshore of NE3 there are a number of sensitive habitats including numerous SPA around the Orkney Islands, in Pentland Firth and on the east coast of mainland Scotland.

NE4

5.2.43 Within NE4, the key pathways which may constrain development are:

  • Biodiversity, flora and fauna, particularly potential effects on bird species through displacement or physical injury, effects on bird migration pathways and effects on spawning herring and sandeel from underwater noise; and
  • Navigational safety, due to overlap with the key commercial shipping route around Scotland.

5.2.44 There is limited potential to mitigate the significant adverse effects on navigational safety within NE4 at a project level through spatial planning, as there is high density commercial shipping traffic throughout the DPO and it overlaps with the main navigation route around Scotland.

5.2.45 As for NE2, concerns regarding effects on seabird populations discussed further under cumulative effects below in Section 0, have the potential to constrain development within NE4. This level of constraint is likely to remain until such a time that further evidence, research and knowledge around mitigation is available to support development in the region.

5.2.46 There is considerable uncertainty regarding the potential cable routes from NE4, therefore no meaningful assessment can be made. Export cable planning will be required to take into consideration sensitive areas at a project level. Inshore of NE4 there are a number of sensitive habitats including numerous SPA in the Moray Firth and on the east coast of mainland Scotland. However, it is recognised that given the co-location of the DPO with current projects and NE5 there may be potential to share export cable infrastructure with current developments.

NE5

5.2.47 Within NE5, the key pathways which may constrain development are:

  • Biodiversity, flora and fauna, particularly potential effects on bird species through displacement or physical injury, effects on bird migration pathways and effects on spawning herring and sandeel from underwater noise;
  • Navigational safety, due to overlap with areas of high shipping density; and
  • Visual effects on landscape / seascape.

5.2.48 There is potential to mitigate the effects on visual receptors through spatial planning and turbine design. Similarly, effects on navigational safety within NE5 may be mitigated at a project level through spatial planning, as there are areas of higher and lower density shipping within the DPO.

5.2.49 As for NE2, concerns regarding effects on seabird populations, discussed further under cumulative effects below in Section 0, have the potential to constrain development within NE5. This level of constraint is likely to remain until such a time that further evidence, research and knowledge around mitigation is available to support development in the region.

5.2.50 There is considerable uncertainty regarding the potential cable routes from NE5, therefore no meaningful assessment can be made. Export cable planning will be required to take into consideration sensitive areas at a project level. Inshore of NE5 there are a number of sensitive habitats including numerous SPA and SAC in the Moray Firth. However, it is recognised that given the co-location of the DPO with current projects and NE4 there may be potential to share export cable infrastructure with current developments.

NE6

5.2.51 Within NE6, the key pathways which may constrain development are:

  • Biodiversity, flora and fauna, particularly potential effects on bird species through displacement or physical injury, effects on bird migration pathways and effects on fish nursery areas from underwater noise; and
  • navigational safety, due to overlap with key commercial shipping routes, including lifeline ferry services to Shetland and recommended routes heading to the north of the Orkney Islands.

5.2.52 There is very limited potential to mitigate the significant adverse effects on navigational safety within NE6 at a project level through spatial planning, as there is high density commercial shipping traffic throughout the DPO and it overlaps with key routes, including lifeline ferry services.

5.2.53 As for NE2 concerns regarding effects on seabird populations, discussed further under cumulative effects below in Section 0, have the potential to constrain development within NE6. This level of constraint is likely to remain until such a time that further evidence, research and knowledge around mitigation is available to support development in the region.

5.2.54 There is considerable uncertainty regarding the potential cable routes from NE6, therefore no meaningful assessment can be made. Export cable planning will be required to take into consideration sensitive areas at a project level. Inshore of NE6 there are a number of sensitive habitats including numerous SPA on the east coast of mainland Scotland and the proposed Nature Conservation MPA at Southern Trench.

NE7

5.2.55 Within NE7, the key pathway which may constrain development is:

  • Biodiversity, flora and fauna, particularly potential effects on bird species through displacement or physical injury and effects on bird migration pathways.

5.2.56 There is potential to mitigate the effects of the above pathway and other lower impact pathways through spatial planning and array design at a project level. Further research and consideration of specific mitigation may be required to reduce effects on bird species' foraging areas and migration pathways.

5.2.57 Given the significant distance from shore, there is considerable uncertainty regarding the potential cable routes from NE7, therefore no meaningful assessment can be made. Export cable planning will be required to take into consideration sensitive areas at a project level. Inshore of NE7 there are a number of sensitive habitats including SPA and the proposed Nature Conservation MPA at Southern Trench.

NE8

5.2.58 Within NE8, the key pathway which may constrain development is:

  • Biodiversity, flora and fauna, particularly potential effects on bird species through displacement or physical injury and effects on bird migration pathways.

5.2.59 There is potential to mitigate the effects of the above pathway and other lower impact pathways through spatial planning and array design at a project level. Further research and consideration of specific mitigation may be required to reduce effects on bird species' foraging areas and migration pathways.

5.2.60 Given the significant distance from shore, there is considerable uncertainty regarding the potential cable routes from NE8, therefore no meaningful assessment can be made. Export cable planning will be required to take into consideration sensitive areas at a project level. Inshore of NE8 there are a number of sensitive habitats including SPA and the proposed Nature Conservation MPA at Southern Trench.

East

E1

5.2.61 Within E1, the key pathway which may constrain development is:

  • Biodiversity, flora and fauna, particularly potential effects on bird species through displacement or physical injury, effects on bird migration pathways and effects on spawning herring, cod, whiting, plaice and sandeel.

5.2.62 There is some potential to mitigate the effects on bird species at a project level. RSPB distribution data suggests that a number of bird species, including Kittiwake, which is a designated feature of the Fowlsheugh SPA, may utilise the waters within and around the DPO and may thus be affected during all phases of wind farm development.

5.2.63 Recent wind farm project assessments (e.g. Neart na Gaoithe) have raised particular concerns from statutory stakeholders with regards to the potential effects from collision and displacement on several seabird species' populations in the East region. These concerns, discussed further under cumulative effects below in Section 0, have the potential to constrain development within E1, albeit that the level or constraint is reduced by the distance of E1 offshore. A degree of constraint is likely to remain until such a time that further evidence, research and knowledge around mitigation is available to support development in the region.

5.2.64 Risks to spawning fish can be mitigated through temporal restrictions on piling activity to avoid key spawning times.

5.2.65 There is considerable uncertainty regarding the potential cable routes from E1, therefore no meaningful assessment can be made. Export cable planning will be required to take into consideration sensitive areas at a project level. Inshore of E1 there are a number of sensitive habitats including SPA on the east coast of mainland Scotland and the Firth of Forth Banks Complex Nature Conservation MPA.

E2

5.2.66 Within E2, the key pathways which may constrain development are:

  • Biodiversity, flora and fauna, particularly potential effects on bird species through displacement or physical injury, effects on bird migration pathways and effects on spawning herring, cod, whiting, plaice and sandeel.
  • Navigational safety, due to overlap with areas of high shipping density.

5.2.67 There is potential to mitigate the effects on navigational safety within E2 at a project level through spatial planning, as there are areas of higher and lower density shipping within the DPO.

5.2.68 As for E1 concerns regarding effects on seabird populations, discussed further under cumulative effects below in Section 0, have the potential to constrain development within E2, albeit that the level or constraint is reduced by the distance of E2 offshore. A degree of constraint is likely to remain until such a time that further evidence, research and knowledge around mitigation is available to support development in the region.

5.2.69 Risks to spawning fish can be mitigated through temporal restrictions on piling activity to avoid key spawning times. In addition, potential impacts on sandeel populations - a designated feature of the Turbot Bank NCMPA - may require assessment and mitigation, such as through spatial planning to avoid the protected area at a project level.

5.2.70 There is considerable uncertainty regarding the potential cable routes from E2, therefore no meaningful assessment can be made. Export cable planning will be required to take into consideration sensitive areas at a project level. Inshore of E2 there are a number of sensitive habitats including SPA on the east coast of mainland Scotland and the Turbot Bank Nature Conservation MPA.

E3

5.2.71 Within E3, the key pathways which may constrain development are:

  • Biodiversity, flora and fauna, particularly potential effects on bird species through displacement or physical injury, effects on bird migration pathways, effects on spawning herring, cod, whiting, plaice and sandeel and effects on grey seal.
  • Navigational safety, due to overlap with areas of high shipping density.

5.2.72 There is potential to mitigate the effects on navigational safety within E3 at a project level through spatial planning, as there are areas of higher and lower density shipping within the DPO.

5.2.73 Concerns regarding effects on seabird populations, particularly species foraging from east coast SPA sites discussed further under cumulative effects below in Section 0, have the potential to constrain development within E3. This level of constraint is likely to remain until such a time that further evidence, research and knowledge around mitigation is available to support development in the region.

5.2.74 Risks to spawning fish can be mitigated through temporal restrictions on piling activity to avoid key spawning times.

5.2.75 There is considerable uncertainty regarding the potential cable routes from E3, therefore no meaningful assessment can be made. Export cable planning will be required to take into consideration sensitive areas at a project level. Inshore of E3 there are a number of sensitive habitats including SPA on the east coast of mainland Scotland and the Firth of Forth Banks Complex Nature Conservation MPA.

5.3 Cumulative Effects

Cumulative effects of the DPOs

5.3.1 The cumulative effects assessment provided below reviews the potentially significant environmental effects of possible development under the Plan at a regional and national level.

5.3.2 For the regional assessment, indicative scales of regional development have been used having regard to the scenarios for overall anticipated scale of development under the plan as a whole. These potential regional scales of development are significantly less than the sum of indicative realistic maximum development scenarios for each DPO. The development of these scenarios is based on the likely available capacity in the respective regions, scales of development under a maximum 10 GW national plan, known constraints on development, early indications as to likely developer interest, and established infrastructure to support development during the plan timescale.

5.3.3 The national assessment has been based on the scenarios for the overall anticipated scale of development under the plan as a whole. These potential scales of development are less than the sum of the indicative scales of regional development used in the regional assessment and significantly less than the sum of indicative realistic maximum development scenarios for each DPO. The justification for the national scenarios is discussed in the Draft Plan.

5.3.4 The assumptions on the scale of development are contained in Table 9 below.

Table 9 Assumptions on scale of development at national and regional scales

  Lower Medium High
National 3 GW (4% of total
capacity in DPOs)
5 GW (7% of total
capacity in DPOs)
10 GW (13% of total capacity in DPOs)
SW 0.3 GW (21% of total capacity in DPOs) 0.6 GW (41% of total capacity in DPOs) 1 GW (68% of total capacity in DPOs)
W 0.5 GW (7% of total capacity in DPOs) 1 GW (14% of total capacity in DPOs) 2 GW (28% of total capacity in DPOs)
N 1 GW (7% of total
capacity in DPOs)
2 GW (13% of total
capacity in DPOs)
3 GW (20% of total capacity in DPOs)
NE 1.5 GW (6% of total
capacity in DPOs)
3 GW (13% of total capacity in DPOs) 4.5 GW (19% of total capacity in DPOs)
E 1 GW (4% of total
capacity in DPOs)
2 GW (7% of total
capacity in DPOs)
3 GW (11% of total capacity in DPOs)

Regional Assessment

South West:

5.3.5 There is only one DPO within the South West region, therefore there is no potential for cumulative effects on a regional scale with other DPOs within this plan.

5.3.6 The application of the three scenarios on a regional scale gives additional potential for mitigating effects within the South West region by limiting the scale of development within the region.

West

5.3.7 There is only one DPO within the West region, therefore there is no potential for cumulative effects on a regional scale with other DPOs within this plan.

5.3.8 The application of the three scenarios on a regional scale gives additional potential for mitigating effects within the West region by limiting the scale of development within the region.

North

5.3.9 There are four sites within the North region, most of which are individually recognised as having potentially moderate to major effects for some pathways. The majority of effects are site specific, and are not additive, primarily due to the spatial separation of the DPOs.

5.3.10 There are four potential effects where the cumulative effects may be additive or potentially synergistic (greater than the sum of the effects associated with the four sites).

5.3.11 There is potential for significant cumulative effects on mobile species, including birds and cetaceans. Migratory bird species, transiting from the UK towards the Faroe Islands and Iceland have migration pathways which intersect DPOs within the North region. Development of areas across all four DPOs therefore has the potential to cause a greater barrier effect to the migration routes, leading to increased collision risk or increased energetic requirements for bird species to divert around developments.

5.3.12 There is additionally potential for cumulative effects on birds from breeding colonies in the North, however the majority of breeding colonies are spatially distinct and foraging areas do not overlap multiple DPOs. Where foraging areas have the potential to overlap this is predominantly related to Gannet, which have large foraging ranges. Therefore development across multiple DPOs would still only impact a small proportion of the total foraging area. Similarly there is limited potential for significant impact on birds from N2 (and hence limited potential for cumulative impacts), as significant water depths in the DPO will limit the potential for foraging activities of bird species.

5.3.13 Potentially significant effects on marine mammals could occur during construction activities, therefore concurrent construction within the DPOs in the North region, focused on those with higher marine mammal usage (N2 and N3) has the potential to either cause physical injury or more likely displace species from these areas, which could cause a barrier effect preventing movement of cetaceans transiting into or out of The Minches. It is recognised that uncertainties regarding marine mammal densities and distributions in the North region has the potential to lead to under or overestimates of the relative impact on marine mammals in the region. There is therefore a requirement for additional survey to support establishment of the marine mammal baseline prior to assessment of potential risks at the project level.

5.3.14 There is significant potential for cumulative effects on visual, seascape and landscape receptors, particularly regarding development within N3 and N4, both of which may be visible from land around North East Lewis.

5.3.15 At a regional scale effects can be mitigated through spatial planning, particularly when considering that anticipated development under all three regionally scaled scenarios, may only develop 5%, 9% and 14% respectively of the area within the DPOs (see Table 6). In addition, when considering visual effects there is potential for the effects to be mitigated through selection of smaller turbines at a project level or to locate turbines within offshore areas of the DPOs. Where there are potential effects during construction the temporal separation of development within the DPOs would avoid additive cumulative effects from occurring. However, there is potential for this to result in a longer period of disruption, for example noise disturbance to receptors over a longer timeframe.

North East

5.3.16 There are eight sites within the North East region, all of which are individually recognised as having potentially moderate to major adverse effects for some pathways. The majority of effects are site specific, and are not additive, partially due to the spatial separation of the DPOs (with the exception of NE4 and NE5), particularly regarding NE1 whose pathways will not combine with any other sites.

5.3.17 There are six potential effects where the cumulative effects may be additive or potentially synergistic (greater than the sum of the effects associated with the eight sites).

5.3.18 Within the North East region a key pathway of concern relates to effects on bird populations, specifically Kittiwake and Guillemot, through collision risk and displacement from foraging areas. These effects have been raised previously by statutory consultees on currently planned projects within the region (e.g. Moray west). This consultation has suggested that there is limited capacity for further development in the region. Development in DPOs in the North East region, particularly those overlapping with areas of high Kittiwake density (NE2, NE3, NE4, NE5 and NE6), has the potential to cause significant cumulative effects to bird populations foraging in the region. Development within DPOs overlapping areas of high expected Kittiwake density is considered to have the potential to cause a significant cumulative effect on Kittiwake populations both within the plan and with current and future developments identified within the North Sea. This is likely to constrain development within these DPOs until such time that further evidence, research and knowledge around mitigation is available to support development in the region.

5.3.19 Migratory bird species, transiting from the UK towards Scandinavia have migration pathways which intersect DPOs within the North East region. Development of areas across multiple DPOs therefore has the potential to form a significant barrier to species movement, leading to increased collision risk or increased energetic requirements for bird species to divert around developments. This will be dependent on the bird species, as flight heights vary, and therefore the turbine size should be considered when assessing risk to species at a project level.

5.3.20 Potentially significant effects on marine mammals and spawning fish could occur during construction activities, therefore concurrent construction within the DPOs in the North East region, such as within NE4 and NE5, has the potential to either cause physical injury or more likely displace species from these areas. It is recognised that uncertainties regarding marine mammal densities and distributions in the North East region has the potential to lead to under or overestimates of the relative impact on marine mammals in the region. There is therefore a requirement for additional survey to support establishment of the marine mammal baseline prior to assessment of potential risks at the project level.

5.3.21 There is potential for cumulative effects on benthic receptors through a number of different pathways. Development within both NE4 and NE5 has the potential to cause a cumulative effect on sediment transport, given their proximity to each other. Hydrodynamic and sediment transport modelling may be required at a project level to confirm and validate potential effects from these cumulative effects. In addition, there is sensitive burrowed mud habitat present throughout a number of the sites in the North East region, specifically NE6, NE7 and NE8, supporting populations of ocean quahog, a priority marine feature (PMF) in Scottish waters. The National Marine Plan places a requirement that development of the marine environment must not result in a significant impact on the national status of PMFs. Development within these sites has the potential for cumulative effects on these sensitive features and therefore assessment would be required at a project level in order to determine the degree of effect. It is possible, however, that development at a regional scale could be constrained based on potential for effects on these benthic receptors.

5.3.22 There are a number of key navigational routes throughout the North East region. The development of large areas of the DPOs has the potential to require traffic to divert or concentrate traffic into smaller areas, thereby increasing navigational risk. Specifically, effects on navigational risk due to development within NE6 have the potential to be cumulative with those in NE4 and NE8.

5.3.23 At a regional scale effects can be mitigated through spatial planning, particularly when considering development under all three regionally scaled scenarios, which will only develop 6%, 13% and 19% respectively of the area within the DPOs (see Table 6). It is recommended that spatial planning at a plan level is considered when reviewing the cumulative risk on navigational risk from NE6 to NE8.

5.3.24 There is a potential cumulative effect on visual receptors from development in the North East, although individually each site has been assessed as having at most a minor impact. This will require consideration at a project level, as the degree of impact is likely to be turbine specific.

5.3.25 Where there are potential temporary effects during construction, the temporal separation of development within the DPOs would avoid additive cumulative effects from occurring. However, there is potential for this to result in a longer period of disruption, through noise disturbance to receptors over a longer timeframe.

East

5.3.26 There are three sites within the East region, all of which are individually recognised as having potentially moderate to major adverse effects for some pathways. The majority of effects are site specific, and are not additive, principally due to the spatial separation of the DPOs.

5.3.27 There are three potential effects where the cumulative effects may be additive or potentially synergistic (greater than the sum of the effects associated with the three sites).

5.3.28 There is potential for cumulative effects on mobile species, principally on bird species. Within the East region the pathway of greatest concern is regarding effects on bird populations, specifically Kittiwake and Guillemot, through collision risk and displacement from foraging areas. These effects have been raised previously by statutory consultees on projects within the region (e.g. Neart na Gaoithe). This consultation has suggested that there is limited capacity for further development in the region due to cumulative effects with current or future offshore wind developments. Development across multiple DPOs in the East region, particularly E3 which overlaps with areas of high Kittiwake density, therefore have the potential to cause significant cumulative effects to Kittiwake populations. Therefore, these DPOs overlapping areas of Kittiwake foraging are considered to have the potential to cause a significant cumulative effect on Kittiwake populations both within the plan and with current and future developments identified within the North Sea. This is likely to constrain development within the DPOs until such a time that further evidence, research and knowledge around mitigation is available to support development in the region.

5.3.29 Migratory bird species, transiting from the UK towards Scandinavia have migration pathways which intersect DPOs within the East region. Development of areas across multiple DPOs therefore has the potential to form a barrier to species movement, leading to increased collision risk or increased energetic requirements for bird species to divert around developments. This will be dependent on the bird species, as flight heights vary, and therefore the turbine size should be considered when assessing risk to species at a project level.

5.3.30 Furthermore, it is recognised that uncertainties regarding marine mammal densities and distributions in the East region has the potential to lead to under or overestimates of the relative impact on marine mammals in the region. There is therefore a requirement for additional survey to support establishment of the marine mammal baseline prior to assessment of potential risks at the project level.

5.3.31 There are a number of key navigational routes throughout the East region. The development of areas in both E1 and E3 may require traffic to divert or concentrate traffic into smaller areas, increasing navigational risk.

5.3.32 At a regional scale effects can be mitigated through spatial planning, particularly when considering development under all three regionally scaled scenarios, which will only develop 4%, 7% and 11% respectively of the area within the DPOs (see Table 6).

Table 10 Summary of cumulative effects by region

Region Key Potential Cumulative Effects
SW There is only one DPO within the South West region, therefore there is no potential for cumulative effects on a regional scale with other DPOs within this plan.
W There is only one DPO within the West region, therefore there is no potential for cumulative effects on a regional scale with other DPOs within this plan.
N There are four key cumulative effects in the North region. Firstly, there is potential for significant cumulative effects on mobile species, including birds and cetaceans. Migratory bird species have migration pathways which intersect DPOs within the North region. Development of areas across all DPOs therefore has the potential to cause a greater barrier effect to the migration routes, leading to increased collision risk or increased energetic requirements for bird species to divert around developments. Furthermore, there is the potential for significant effects on marine mammals. Cetaceans are primarily affected during construction activities, therefore concurrent construction within the DPOs in the North region has the potential to either cause physical injury or more likely displace species from these areas, which could cause a barrier effect preventing movement of cetaceans. There is also significant potential for cumulative effects on visual, seascape and landscape receptors, particularly regarding development within N3 and N4, both of which may be visible from land around North East Lewis.
NE There are six key cumulative effects in the North East region. Firstly, there is potential for cumulative effects on mobile species, principally on bird species. Within the North East region one pathway of concern is regarding effects on bird populations, specifically Kittiwake and Guillemot, through collision risk and displacement from foraging areas. Furthermore, development of areas across multiple DPOs has the potential to form a barrier to species movement, leading to increased collision risk or increased energetic requirements for bird species to divert around developments. Concurrent construction within the DPO's could cause physical damage or displace marine mammals and spawning fish from the area. There is also potential for cumulative effects on benthic receptors from sediment transport. There are many key navigational routes throughout the region and cumulative effects could cause traffic to divert or concentrate traffic into smaller areas, increasing navigational risk. Finally, there is potential for cumulative visual impacts, although the impact will be dependent on turbine size and spatial planning.
E There are three key cumulative effects in the East region. Firstly, there is potential for cumulative effects on mobile species, principally on bird species. Within the East region the pathway of greatest concern is regarding effects on bird populations, specifically Kittiwake and Guillemot, through collision risk and displacement from foraging areas. Furthermore, development of areas across multiple DPOs has the potential to form a barrier to species movement, leading to increased collision risk or increased energetic requirements for bird species to divert around developments. There are also many key navigational routes throughout the region and cumulative effects could cause traffic to divert or concentrate traffic into smaller areas, increasing navigational risk.

National Assessment

5.3.33 At a national scale there are a total of 17 DPOs, most of which are individually recognised as having potentially moderate to major adverse effects. The majority of the effects are site or region specific, and are therefore not additive on a national scale, with little connectivity between sites in separate regions. The majority of effects will not, therefore, have a cumulative effect at a national scale beyond that identified in the individual DPO or regional assessments presented above.

5.3.34 The exception to this is the potential for effects on both resident and migratory bird populations. The cumulative effects are generally split by either east coast or west coast as the populations tend to be distinct and migration pathways follow the coasts before heading either towards Faroe Islands and Iceland in the case of the west coast or Scandinavia in the case of the east coast.

5.3.35 On the west coast the species of highest concern are migratory and have the potential to transit through multiple regions (SW, W and N) and DPOs as part of their migratory pathways. As a result, there is potential for the increases in collision risk, identified at a DPO and regional level, to be further additive at a national level across all west coast DPOs. The level of collision or displacement risk to individual species may vary depending on flight height and avoidance probabilities, however species whose migration pathways may transect the DPOs on the west coast include[251]:

  • Whooper Swan;
  • Goose species;
  • Duck species;
  • Wigeon;
  • Teal;
  • Pintail;
  • Scaup;
  • Common Scoter;
  • Oystercatcher;
  • Golden Plover;
  • Sanderling;
  • Dunlin;
  • Snipe;
  • Black-tailed Godwit;
  • Whimbrel;
  • Redshank; and
  • Turnstone.

5.3.36 Potential cumulative effects on birds on the east coast, encompassing DPOs from the E and NE regions, include both effects to migratory and resident species. Impacts to resident species have been highlighted by statutory consultees on current projects in both the E and NE regions (e.g. Moray west and Neart na Gaoithe), particularly with regard to Kittiwake and Guillemot populations. The conclusions of these consultation responses are that there is very limited capacity within resident bird populations, focusing on Kittiwake for further development in the E and NE regions.

5.3.37 On the east coast there are similar concerns regarding migratory species. Several species transit through the east coast regions (E and NE) and therefore may potential transit multiple DPOs. The level of collision or displacement risk to individual species may vary depending on flight height and avoidance probabilities, however species whose migration pathways may transect the DPOs on the east coast include:

  • Goose species;
  • Duck species;
  • Wigeon;
  • Teal;
  • Pintail;
  • Pochard;
  • Scaup;
  • Common Scoter;
  • Velvet Scoter;
  • Hen Harrier;
  • Kestrel;
  • Oystercatcher;
  • Dotterel;
  • Golden Plover;
  • Grey Plover;
  • Sanderling;
  • Dunlin;
  • Ruff;
  • Snipe;
  • Woodcock;
  • Black-tailed Godwit;
  • Bar-tailed Godwit;
  • Whimbrel;
  • Curlew;
  • Greenshank;
  • Redshank; and
  • Turnstone.

5.3.38 On both coasts the potential for collision risk may be cumulative with effects from development in multiple DPOs affecting the same bird species or populations at a national level. These effects have the potential to permanently reduce bird numbers, particularly where populations are already in decline.

5.3.39 In addition to the potential for negative cumulative effects above, the development of the DPOs in line with this plan has the potential to have significant positive cumulative effects, regarding supporting a diverse and decarbonised energy sector, and the development of a secure energy supply for the UK market. The magnitude of this benefit will be based on the extent of development under the plan, but under the high scenario has the potential to provide a significant contribution to the energy sector in Scotland and more widely within the UK.

Cumulative effects of the plan with other projects

5.3.40 Development of offshore wind within the DPOs, and installation of export cables and cable landfall infrastructure, identified within this plan has the potential to combine with projects currently being undertaken or being considered for future development. This includes other offshore wind developments, particularly in the North East and East regions, offshore wave draft plan option areas, tidal stream energy developments, marine and coastal construction projects, and oil and gas exploration, operation and decommissioning.

5.3.41 There is considerable uncertainty regarding the likelihood of development against many of the projects with potential for cumulative effects. It is therefore not possible to undertake a detailed assessment. However, as discussed above in Section 5.3.28, the potential cumulative impact on east coast bird colonies within the plan and with other projects is currently likely to impose a constraint on development inshore on the east coast (incorporating development in both the East and North East regions).

5.3.42 A summary of the potential pathways which may require assessment for cumulative effects of marine developments in Scottish waters with development of the DPOs is provided in Table 11 below. Project level cumulative assessment will need to also consider the potential for cumulative impacts with other developments outwith Scottish waters, including in the wider North Sea region.

5.3.43 There is potential for cumulative effects on visual receptors from onshore wind developments, alongside those associated with offshore wind. The majority of onshore wind developments in Scotland are inshore and where they are visible from the coast are unlikely to be present within the same view as the offshore wind developments. Further review for specific developments will be required as a part of project level assessment.

Table 11 Cumulative effect pathways with other marine developments

Development Type Current Developments DPOs with Potential for Cumulative Effects Key Pathways Which are Likely to Require Consideration
Offshore Wind Robin Rigg SW1, W1, N2, N3, N4 Construction Effects on key mobile receptors and prey species through displacement or physical injury, including:
  • marine mammals;
  • fish species, including basking shark, spawning fish and migratory fish including diadromous fish;
  • bird species.
Operation
  • Effects on key mobile receptors and prey species, including:
  • migratory birds, for example Whooper Swan migration pathways;
  • resident bird populations (particularly Kittiwake on the east coast).
Issues of navigational safety, aviation and collision risk. Effects on subsea geology, sediments, and coastal processes. Both temporary and longer-term effects on landscape and coastal character and visual receptors It is also recognised that there may be some potential for shared infrastructure between existing sites and new developments where capacity is available, therefore reducing effects from export cable installation.
Levenmouth Turbine E1, E2, E3
Hywind E1, E2, E3
Aberdeen Bay (EOWDC) E1, E2, E3
Beatrice NE2, NE3, NE4, NE5, NE6
Neart na Gaoithe E1, E2, E3
Firth of Forth 1 E1, E2, E3
Moray East NE2, NE3, NE4, NE5, NE6
Inch Cape E1, E2, E3
Kincardine E1, E2, E3
Dounreay Tri Demonstration Project N1
Firth of Forth 2 E1, E2, E3
Firth of Forth 3 E1, E2, E3
Moray West NE2, NE3, NE4, NE5, NE6
Forthwind OWF, Methil E1, E2, E3
Tidal Stream North Yell, Bluemull Sound, Shetland NE1 Construction Effects on key mobile receptors and prey species through displacement or physical injury, including:
  • marine mammals;
  • fish species, including basking shark, spawning fish and migratory fish including diadromous fish;
  • bird species.
Operation Issues of navigational safety, aviation and collision risk. Effects on subsea geology, sediments, and coastal processes. Both temporary and longer-term effects on landscape and coastal character and visual receptors.
Sound of Islay W1
Ness of Duncansby, Pentland Firth N1, NE2, NE3
Westray South, Pentland Firth N1, NE2, NE3
Brough Ness, Pentland Firth N1, NE2, NE3
Inner Sound, Pentland Firth N1, NE2, NE3
Mull of Kintyre, Argyll W1
Isle of Islay, Islay W1
Lashy Sound N1, NE2, NE3
Brims Tidal Array (formerly Cantick Head) N1, NE2, NE3
Mull of Galloway SW1
Fall of Warness N1, NE2, NE3
Shapinsay Sound N1, NE2, NE3
Islay Demonstration Zone W1
Stronsay Firth N1, NE2, NE3
Wave Billia Croo N1, NE2, NE3 Construction Effects on key mobile receptors and prey species through displacement or physical injury, including:
  • marine mammals;
  • fish species, including basking shark, spawning fish and migratory fish including diadromous fish;
  • bird species.
Operation Issues of navigational safety, aviation and collision risk. Effects on subsea geology, sediments, and coastal processes. Both temporary and longer-term effects on landscape and coastal character and visual receptors.
Scapa Flow N1, NE2, NE3
Scottish Sea Farms (MANTA) - Teisti Geo NE1
WaveNet Mingary No DPOs affected
Harris Demonstration Zone N3, N4
Hybrid Katanes Floating Energy Park N1
Oil and Gas North Sea All NE and E DPOs Construction Effects on key mobile receptors and prey species through displacement or physical injury, including:
  • marine mammals;
  • fish species, including basking shark, spawning fish and migratory fish including diadromous fish;
  • bird species.
Operation Issues of navigational safety, aviation and collision risk. Effects on subsea geology, sediments, and coastal processes.
West of Shetland No DPOs affected
Marine and coastal construction projects There is potential for development around the Scottish coastline All DPOs may interact with areas of coastline where there is potential for construction projects. Construction Effects on key mobile receptors and prey species through displacement or physical injury, including:
  • marine mammals;
  • fish species, including basking shark, spawning fish and migratory fish including diadromous fish;
  • bird species.
Operation Issues of navigational safety, aviation and collision risk. Effects on subsea geology, sediments, and coastal processes. Both temporary and longer-term effects on landscape and coastal character and visual receptors.

5.4 Summary of Overarching Plan Effects

5.4.1 At the scales of potential development under the plan as a whole (Section 3.5) a very small proportion of the total DPOs will be developed in either the low, medium or high scenarios. The effects of this level of development vary significantly depending on the DPOs and regions in which development might occur.

5.4.2 Areas of key concern, and the topics most likely to constrain development from an environmental viewpoint are bird collision and displacement risk, and navigational risk. Bird collision risk is particularly likely to constrain development in the East and North East regions, where concerns over bird populations, specifically Kittiwake, Gannet and Guillemot, have been raised against current development projects. Significant effects are also likely on landscapes and seascapes for developments located inshore.

5.4.3 It is recognised that there remains uncertainty in the baseline for bird and marine mammal distributions foraging within or migrating through Scottish waters and therefore, whilst this assessment considers currently available data, it is expected that project level survey will be required to establish a robust baseline against which an assessment can be made.

5.4.4 Against all of the pathways there is potential for mitigation through spatial planning at a national level, with areas of lower risk in the North region, and in areas of the West region DPO. In addition, DPOs located further offshore in the North East and East regions are likely to be constrained to a lesser degree than those further inshore in areas of higher bird density.

5.4.5 It is recognised that the implementation of the plan will have a significant environmental benefit in supporting the decarbonisation of the energy sector and the establishment of a secure energy supply in the UK.

5.4.6 A review of the plan has been undertaken against the SEA objectives, the results of which are contained within Table 12 below.

Table 12 Review of the plan against SEA objectives

Topic SEA Objective Assessment of the Plan Against SEA Objective
Biodiversity, Flora, and Fauna To safeguard marine and coastal ecosystems, including species, habitats, and their interactions Development within the DPOs and along the export cable routes will have some direct and indirect effects on species and habitats. These effects can be minimised through careful site and route selection and implementation of appropriate mitigation. The increase in renewable energy capacity will, in the long-term, contribute to reducing greenhouse gas emissions associated with energy generation and thus help to limit the effects of climate change on marine ecosystems.
To avoid adverse effects on both designated and non-designated habitats and species (note links with HRA) None of the DPOs overlap with designated sites, however the HRA identifies potential for interaction between offshore wind development in the DPOs and the foraging ranges of bird species from SPA. The proposed plan-level mitigation measures will help to avoid/minimise impacts to designated features. Where potential cable routes might intersect designated sites, adverse effects can be avoided or minimised through careful route selection and installation methods. Risks to non-designated habitats and species can be avoided or minimised through careful project design and adoption of appropriate mitigation measures.
To avoid the introduction and spread of INNS. Risks associated with vessels can be minimised through the implementation of biosecurity plans for construction operation and decommissioning of offshore wind farms. The presence of offshore wind farms will provide new substrate which could be colonized by INNS. However, experience to date does not indicate that this is a significant risk pathway for the spread of INNS.
Population and Human Health To maintain the accessibility of natural areas for recreation Within the DPOs themselves, recreational activity is limited to yachting activity and angling. There is potential for displacement of this activity, however spatial planning within the DPOs can be used to avoid areas of key effect and mitigate any deterioration against this objective. There are some areas inshore of the DPOs where recreational activity may be affected by export cable installation. However, effects from cable installation are considered to be temporary, and planning of the cable route to avoid key areas can mitigate deterioration against the objective.
To minimise or prevent the discharge of pollutants into the natural environment The implementation of the plan will not directly support achievement of this objective; however, it is not considered likely that implementation of the plan will lead to a deterioration against this objective. At a project level, pollution management plans will be produced to mitigate against the effects.
To avoid adverse effects on human health and safety The implementation of the plan has the potential to cause deterioration of the environment against this objective due to negative effects on navigational safety. There is potential for effects on navigational safety, particularly in NE4 and NE6. In addition, where DPOs overlap at a lesser scale with navigational routes, spatial planning can be used at a project level to allow for safe transit through the DPOs, in part through the application of MCA guidance in MGN 543. At a plan level, it is considered that there will be a residual deterioration against this objective.
Soil (Marine Geology and Coastal Processes) To avoid exacerbating coastal erosion and maintain the integrity of coastal processes There are several areas where the development of a DPO and associated export cable installation has the potential to affect coastal processes. At the plan level it is not possible to determine the extent of these effects, therefore at a project level it is possible that hydrodynamic and sediment modelling may be required to determine if a development will affect coastal processes.
To maintain and protect the character and integrity of the seabed, including avoiding the pollution of seabed strata/bottom sediments The installation of turbines and subsea cables will affect the seabed within their physical footprint, and immediate vicinity. The development of offshore wind within the DPOs and associated export cable installation will therefore cause deterioration against this objective. The degree of effect will, however, vary significantly dependent on the technology employed, the level of scour protection required, and the seabed type.
To avoid significant adverse physical damage to coastal geodiversity sites from coastal infrastructure There is considerable uncertainty regarding potential cable landfall locations, therefore the effect on coastal geodiversity sites cannot be assessed at a plan level. Assessment against this pathway will be undertaken at a project level, however it is expected that cable routes will be planned to avoid geodiversity sites.
Water Quality To avoid pollution of the coastal and marine water environment The implementation of the plan will not directly support achievement of this objective; however, it is not considered likely that implementation of the plan will lead to a deterioration against this objective. At a project level, pollution management plans will be produced to mitigate against the effects.
To maintain or work towards achieving good ecological status The implementation of the plan has the potential to cause deterioration of the environment against this objective. Where potential for effects on the ecological baseline are identified above, recommendations have been raised to mitigate this at a plan level. At a project level, spatial planning can generally be used to avoid areas of high effect within an individual DPO and associated cable routes, and the WFD regulations place requirements on developers to avoid significant effects on the ecological status of coastal or transitional water bodies.
Climatic Factors To contribute to a diverse and decarbonised energy sector The development of offshore wind in line with the plan has the potential to significantly contribute to the achievement of this objective.
To ensure that adaptation to predicted climate change impacts are taken into account (for example, through consideration of resilience and changing environmental sensitivity) The plan cannot be assessed against this objective, however individual developments will be required to take account of and ensure that designs incorporate resilience against potential climate change effects. In addition, any changes to the baseline as a result of climate change will be incorporated into the plan as part of the iterative plan review process.
To preserve marine carbon stocks and carbon sequestration potential (note: this objective is closely linked to the SEA topic of 'Biodiversity, Flora, and Fauna') There is potential for marine carbon stocks to be present within DPOs or within export cable corridors, and to be affected by development of offshore wind. At a project level spatial planning will be required to avoid areas of sensitive marine carbon, however there is potential for disturbance of seabed sediments, which form a significant carbon sink. The disturbance of seabed sediments is dependent on the technology selected, however it is considered unlikely that effects will cause deterioration against this objective at a national level.
Cultural Heritage To protect and, where appropriate, enhance, the historic marine environment There are no designated historic areas within the DPOs. However, there are known shipwrecks within the DPOs and at a project level surveys will be required to identify areas of potential historic significance, effects on which can subsequently be avoided. At a project level this will be managed through the application of a Marine Archaeology Reporting Plan (MARP). The process of developing within the DPOs therefore has the potential to identify additional heritage assets and therefore support the achievement of this objective.
To avoid damage to known and unknown coastal and marine archaeology There are no designated historic areas within the DPOs. However, there are known shipwrecks within the DPOs and at a project level surveys will be required to identify areas of potential historic significance, effects on which can subsequently be avoided. The process of developing within the DPOs therefore has the potential to identify additional heritage assets and therefore support the achievement of this objective. There is considerable uncertainty regarding potential cable routes and landfall locations, therefore the effect on coastal heritage sites cannot be assessed at a plan level. Assessment against this pathway will be undertaken at a project level through the application of a MARP, and any sensitive heritage assets avoided through appropriate route selection.
To avoid adverse effects on the character and setting of historic sites and buildings There is considerable uncertainty regarding potential cable routes and landfall locations, therefore the effect on coastal or inland heritage sites cannot be assessed at a plan level. Assessment against this pathway will be undertaken at a project level, associated with the terrestrial planning process.
Landscape/ Seascape To avoid or minimise adverse effects on landscape, seascape, and visual amenity, including designated sites; There are significant areas identified within the DPOs within which developments will affect the landscape, seascape and visual amenity of the coastal region in high and low light conditions. Potential mitigations have been identified for consideration at a project level, specifically the spatial planning to avoid areas closest to land or, where this is not possible, selection of smaller turbines in areas closer to land, to minimise adverse effects. This assessment can therefore support the implementation of the plan whilst achieving against this objective.
To promote the protection of seascape and coastal landscapes; Assessment within the plan has identified potential risks to seascape and coastal landscapes, and proposed mitigation measures to reduce or remove effects. The plan therefore may support achievement of the objectives by identifying areas of lower risk for development.
To avoid or minimise adverse visual effects. There are significant areas identified within the DPOs within which developments will affect the landscape, seascape and visual amenity of the coastal region. Potential mitigations have been identified for consideration at a project level, specifically the spatial planning to avoid areas closest to land or, where this is not possible, selection of smaller turbines in areas closer to land, in order to reduce the visual effects. This assessment can therefore support the implementation of the plan whilst achieving against this objective.

Contact

Email: drew.milne@gov.scot