Publication - Progress report

Draft Sectoral Marine Plans for Offshore Renewable Energy in Scottish Waters - Environmental Report Appendix C: Assessment of Technologies

Published: 25 Jul 2013
Part of:
Marine and fisheries
ISBN:
9781782567462

Appendix C to the SEA Environmental Report of the Draft Sectoral Marine Plans for Offshore Renewable Energy in Scottish Waters.

This appendix contains an assessment of technologies.

50 page PDF

1.3 MB

50 page PDF

1.3 MB

Contents
Draft Sectoral Marine Plans for Offshore Renewable Energy in Scottish Waters - Environmental Report Appendix C: Assessment of Technologies
2 Wave technology

50 page PDF

1.3 MB

2 Wave technology

SEA Topic Areas

Point Absorbers and Rotating Mass Devices

Attenuators and Bulge Wave Devices

Oscillating Wave Surge Converters

Submerged Pressure Differential

Oscillating Water Column (Offshore and Shoreline)

Overtopping Device (Offshore and Shoreline)

Device Information [9]

  • Consist of floating structures that absorb energy in all directions through their movements at the water surface, or by device rotation created by wave movements.
  • Are located at the water surface with above water or near surface components ( i.e. the spar and float that houses generation equipment).
  • Are likely to be anchored and moored to the seabed ( i.e. embedded, gravity/deadweight or rock anchors) with mooring lines spanning the full depth of the water column.
  • Marker buoys and lighting are likely to be used for offshore awareness and navigation.
  • Consists of elongated devices floating on the water surface with associated support structures or moorings.
  • Consist of large elongated structures made up of several floating parts with moving joints ( e.g. Attenuators such as Pelamis) or flexible devices floating on the water surface ( e.g. Bulge wave devices).
  • The device(s) floating on the surface, typically staggered in rows, and likely have a shallow draft.
  • Likely to be moored by anchors on the seabed ( i.e. embedded, gravity/ deadweight or rock) and have associated mooring lines spanning the full depth of the water column. Support structures may also be present.
  • Marker buoys and lighting are likely to be used for offshore awareness and navigation.
  • Consists of a surface or near-surface paddle device, mounted on a fixed base on the seabed, oscillating with passing waves ( e.g. Oyster devices).
  • Is likely to be fixed to seabed with a gravity base ( i.e. rock anchors/pins).
  • Energy generation equipment ( i.e. pistons and joints) are located within the water column.
  • There is the possibility that the device will also involve pipelines to shore for pumping water.
  • Marker buoys and lighting are likely to be used for offshore awareness and navigation.
  • Consists of near-surface but submerged device located offshore and fixed to the seabed.
  • The device floats within the water column, moving up and down with wave systems.
  • Is likely to be mounted on a fixed gravity base on the seabed attached by gravity or other means ( i.e. rock anchors/pins, etc.)
  • Marker buoys are likely to be used for offshore awareness and navigation.
  • Consists of a partially submerged hollow structure located offshore, or as a shoreline-based structure.
  • Offshore devices are likely to be moored by anchors (gravity, deadweight or embedded) with associated mooring lines present in the full depth of the water column.
  • Energy generation equipment is housed above the water surface in the floating component (offshore) or housed within an onshore structure (shoreline).
  • Marker buoys and lighting are likely to be used for offshore awareness and navigation.
  • Consists of a floating structure with large catchment area (offshore) or located onshore at the shoreline, typically with a breakwater (shoreline).
  • Offshore devices are positively buoyant and are likely to be moored by anchors with mooring lines.
  • Energy generation equipment is housed above the water surface in the floating component of the device (offshore) or housed within an onshore structure (shoreline).
  • Marker buoys and lighting is likely to be used for offshore awareness and navigation.

Biodiversity/ flora/fauna [10]

Summary of key potential effects:

  • Physical disturbance during device installation.
  • Noise during construction (particularly piling) and from device operation.
  • Risk of bird collision with operating devices ( e.g. migration).
  • Accidental contamination from device failures, vessel collisions and storm damage.
  • Habitat exclusion and species displacement due to device presence and operation.
  • Barriers to movement - due to avoidance reactions to noise and risk of collision.
  • Increased suspended sediment/turbidity from seabed disturbance during device installation and cable trenching.
  • Smothering from seabed disturbance during device installation and cable trenching.
  • Changes in tidal flow and wave regime due to device presence and operation.
  • Substratum loss, caused by attaching devices to the seabed.
  • Habitat and species loss/disturbance during installation of cables and overhead lines and substation construction from onshore grid connections

Key measures to prevent adverse effects may include: avoidance of sensitive sites; avoidance of sensitive seasons ( e.g. breeding) during installation; use of devices with attachments that cause smaller seabed disturbance such as anchors and clump weights; protocols (such as use of Marine Mammal Observers) to ensure noisy construction activities do not occur when marine mammals are in close proximity; effective device design; and project-specific studies to help design appropriate mitigation; carry out detailed routeing studies at project level in accordance with 'Holford Rules' best practice guidance on routeing overhead transmission lines.

Fauna:

Attraction of Fauna

Bird aggregation utilising above water infrastructure may occur, particularly during calm water periods (if any) and if located in foraging waters.

Noise

Potential for underwater noise impacts on marine fauna, from drilling/installation works ( i.e. anchoring works, etc.) or from machinery housing in floating or subsurface structures. As such, there is the potential for behavioural impacts to seals and otters (typically near shoreline), and cetaceans and basking sharks (offshore) possibly avoiding these locations during installation and operation. But there are significant unknowns on disturbance effects as they are likely to be site-specific, and also regarding actual noise levels generated by this technology. In summary, acute effects to these receptors are considered unlikely, with impacts likely to be most significant during piling and drilling activities (if undertaken).

The potential for disturbance impacts to marine fauna ( i.e. seals, otters) from above surface noise has been identified, particularly during installation works ( i.e. machinery, vessels) and where floating device structures house noise-generating equipment (expected to be most devices of these types). This disturbance may be greater for those devices near to the shoreline, however, this will likely be site specific given the significant unknowns on the specific effects of such disturbance and likely receptors.

Shock Waves

There is the potential for shock or pressure waves from large waves hitting the side of surface-piercing structures with high profiles above the water surface. The magnitude of any impacts and their effects on these species is not yet known, although the potential for impacts to seals, cetaceans, otter and basking shark has been identified.

EMF

While no EMF impacts have been identified from the devices, there is the potential for EMF impacts from underwater cabling and grid connections. Further information is required to determine the potential susceptibility of marine fauna and likely effects associated with this issue.

Physical Barrier

The physical presence of new structures in the water column may disrupt movements or migration of marine fauna, particularly for groups of devices. Given the mobility of these species, any impacts are likely to be site specific. There are unknowns over movements and migration routes ( i.e. basking sharks), patterns of movement of other species ( i.e. seals, otters), and also over whether these devices and their moorings will be perceived by fauna, and if they will simply alter their movement accordingly. It is noted that near-shore devices may restrict movement more than offshore ( e.g. potentially greater alternatives for movement around devices offshore).

The potential for collisions between marine fauna and these devices and their moorings has been identified, particularly for those with moving parts. However, this will be largely dependent on the size and design of the device, the location of the device ( i.e. proximity to seal haul out zones, etc.) and the response of the marine fauna involved. Avoidance is likely for many species ( i.e. fish), but impact could also be fatal in some instances if it were to occur ( i.e. seals, otters, cetaceans, basking shark).

Collision with or entanglement in mooring lines associated with offshore devices is considered possible, particularly for larger species ( i.e. minke whales which are more prone to entanglement than other ondontocetes/toothed whales) with a particular focus on complex arrays of devices and their multiple mooring lines ( e.g. likely 3-point mooring systems). However, whether this is significant is not presently known, although it is noted that if it did occur, it may result in serious injury or fatality.

Displacement

In general terms, the potential displacement of species from the presence of devices or associated structures, disturbance during installation, operation or decommissioning ( i.e. noise, turbulence, vibration, displacement of prey, etc.) is likely to be site-specific and would likely depend on a range of other factors (suitable alternative sites, importance of habitat, etc.).

Any impacts would also likely depend on what activities are being displaced and their importance ( e.g. Basking sharks avoiding of structures or installation/servicing vessel activities may lead to the displacement of foraging activities or courtship behaviour).

Fauna:

Attraction of Fauna

Bird aggregation utilising above water infrastructure may occur, particularly during calm water periods (if any) and if located in foraging waters.

Noise

Potential for underwater noise impacts on marine fauna, from drilling/installation works ( i.e. rock anchors and mooring lines, etc.), from machinery housing in floating structures, structures on the seabed, and from anchors and mooring lines. As such, there is the potential for behavioural impacts to seals and otters (typically near shoreline), and cetaceans and basking sharks (offshore) possibly avoiding these locations during installation and operation. But there are significant unknowns on disturbance effects as they are likely to be site-specific, and also regarding actual noise levels generated by this technology. In summary, acute effects to these receptors are considered unlikely, with impacts likely to be most significant during piling and drilling activities (if undertaken).

The potential for disturbance impacts to marine fauna ( i.e. seals, otters) from above surface noise has been identified, particularly during installation works ( i.e. machinery, vessels) and where floating device structures house noise-generating equipment (expected to be most devices of this type). This disturbance may be greater for those devices near to the shoreline, however, this will likely be site specific given the significant unknowns on the specific effects of such disturbance and likely receptors.

EMF

While no EMF impacts have been identified from the devices, there is the potential for EMF impacts from underwater cabling and grid connections. Further information is required to determine the potential susceptibility of marine fauna and likely effects associated with this issue.

Physical Barrier

The physical presence of new structures in the water column may disrupt movements or migration of marine fauna, particularly for groups of devices. Given the mobility of these species, any impacts are likely to be site specific. There are unknowns over movements and migration routes ( i.e. basking sharks), patterns of movement of other species ( i.e. seals, otters), and also over whether these devices and their supporting infrastructure ( i.e. structures, moorings) will be perceived by fauna, and if they will simply alter their movement accordingly. It is noted that near-shore devices may restrict movement more than offshore ( e.g. potentially greater alternatives for movement around devices offshore).

The potential for collisions between marine fauna and these devices and their moorings has been identified, particularly for those with moving parts, and those with large footprints ( i.e. Pelamis, Bulge wave devices). However, this will be largely dependent on the actual size and design of the device, the location of the device ( i.e. proximity to seal haul out zones, etc.) and the response of the marine fauna involved. Avoidance is likely for many species ( i.e. fish), but impact could also be fatal in some instances if it were to occur ( i.e. seals, otters, cetaceans, basking shark).

Collision with or entanglement in mooring lines associated with offshore devices is considered possible, particularly for larger species ( i.e. minke whales which are more prone to entanglement than other ondontocetes/toothed whales) with a particular focus on complex arrays of devices and their multiple mooring lines ( e.g. likely multiple point mooring systems). However, whether this is significant is not presently known, although it is noted that if it did occur, it may result in serious injury or fatality.

Displacement

In general terms, the potential displacement of species from the presence of devices or associated structures, disturbance during installation, operation or decommissioning ( i.e. noise, turbulence, vibration, displacement of prey, etc.) is likely to be site-specific and would likely depend on a range of other factors (suitable alternative sites, importance of habitat, etc.).

Any impacts would also likely depend on what activities are being displaced and their importance ( e.g. Basking sharks avoiding of structures or installation/servicing vessel activities may lead to the displacement of foraging activities or courtship behaviour).

Fauna:

Noise

Potential for underwater noise and vibration impacts on marine fauna, from drilling/installation works ( i.e. anchoring works, etc.) or from machinery housing in subsurface structures. The potential for behavioural impacts to seals and otters (typically near shoreline), and cetaceans and basking sharks (offshore) with the likelihood of small-scale avoidance during operation. But there are significant unknowns on disturbance effects (likely site-specific), and noise levels that are actually generated. Acute effects are considered unlikely. Impacts are likely to be most significant during piling and drilling activities.

While no surface noise is likely, the potential for impacts from above surface noise was identified during installation works ( i.e. installation machinery, vessels). However, this is likely to be temporary and there are significant unknowns on disturbance effects of this nature as they are likely to be site-specific.

EMF

While no EMF impacts have been identified from the devices, there is the potential for EMF impacts from underwater cabling and grid connections. Further information is required to determine the potential susceptibility of marine fauna and likely effects associated with this issue.

Physical Barrier

The physical presence of these devices in the water column and mounted on the seabed may disrupt movements or migration of marine fauna. There are unknowns over known movements and migration routes ( i.e. basking sharks), patterns of movement of other species ( i.e. seals, otters), whether the devices will be perceived or if they will simply alter their movement accordingly. Near-shore devices may restrict movement more than offshore ( e.g. potentially greater alternatives for movement around devices offshore).

Potential for collisions for marine fauna with devices and support structures, although this will be largely dependent on the size and design of the device, the location of the device ( i.e. proximity to seal haul out zones, etc.) and the response of the animal. Avoidance is likely for many species ( i.e. fish), but impact could be fatal in some instances if it were to occur ( i.e. seals, otters, cetaceans, basking shark). Collision with or entrapment in device arrays may be possible, particularly for larger species ( i.e. cetaceans and basking sharks) with particular focus on complex arrays or groups of devices. However, whether this could occur is uncertain and while it may result in injury or fatality, it is considered unlikely.

Displacement

In general terms, the potential displacement of species from the presence of these devices and support structures, disturbance during installation, operation or decommissioning ( i.e. noise, turbulence, vibration, displacement of prey, etc.) is likely to be site-specific and would depend on a range of other factors (suitable alternative sites, importance of habitat, etc.).

It will also depend on what activities are being displaced and their importance ( e.g. Basking sharks avoiding of structures or installation/servicing vessel activities may lead to the displacement of foraging activities or courtship behaviour).

In placement of these devices on the seabed, or on supports placed on the seabed, some loss of benthic habitat will occur.

Fauna:

Noise

Potential for underwater noise impacts on marine fauna, from drilling/installation works ( i.e. anchoring works, etc.) or from machinery housing in subsurface devices. The potential for behavioural impacts to seals and otters (typically near shoreline), and cetaceans and basking sharks (offshore) with small-scale avoidance during operation. But there are significant unknowns on disturbance effects (likely site-specific), and noise levels that are actually generated. Acute effects are considered unlikely. Impacts are likely to be most significant during piling and drilling activities.

The potential for impacts from above surface noise was identified during installation works ( i.e. installation machinery, vessels). There are significant unknowns on disturbance effects of this nature as they are likely to be site-specific.

EMF

While no EMF impacts have been identified from the devices, there is the potential for EMF impacts from underwater cabling and grid connections. Further information is required to determine the potential susceptibility of marine fauna and likely effects associated with this issue.

Physical Barrier

The physical presence of device components in the water column and connection to seabed-based support structures may disrupt movements or migration of marine fauna. However, there are unknowns over known movements and migration routes ( i.e. basking sharks), patterns of movement of other species ( i.e. seals, otters), whether moorings and devices will be perceived or if they will simply alter their movement accordingly. Near-shore devices (if used) may restrict movement more than offshore ( e.g. potentially greater alternatives for movement around devices offshore).

Potential for collisions for marine fauna with devices, particularly as they will move within the water column, although this will be largely dependent on the size and design of the device, the location of the device ( i.e. proximity to seal haul out zones, etc.) and the response of the animal. Avoidance is likely for many species ( i.e. fish), but impact could be fatal in some instances if it were to occur ( i.e. seals, otters, cetaceans, basking shark). Collision with or entanglement in mooring lines associated with these devices is considered possible, particularly for larger species ( i.e. cetaceans and basking sharks) with particular focus on complex arrays with groups of devices each with several mooring lines. However, whether this could occur is unknown, and while it may result in injury or fatality, it is considered unlikely.

Displacement

In general terms, the potential displacement of species from the presence of devices or associated structures, disturbance during installation, operation or decommissioning ( i.e. noise, turbulence, vibration, displacement of prey, etc.) is likely to be site-specific and would depend on a range of other factors (suitable alternative sites, importance of habitat, etc.).

Will also depend on what activities are being displaced and their importance ( e.g. Basking sharks avoiding of structures or installation/servicing vessel activities may lead to the displacement of foraging activities or courtship behaviour).

In placement of support structures for these devices on the seabed, some loss of benthic habitat will occur.

Fauna:

Attraction of Fauna

Bird aggregation utilising above water infrastructure may occur, particularly during calm water periods (if any) and if located in foraging waters.

Noise

There is the potential for underwater noise impacts on marine fauna, from drilling/installation works ( i.e. anchoring works, etc.) and from machinery housing in floating or subsurface structures (for offshore devices only). This may also be a potential issue with installation works and the housing of noise generating equipment at shoreline devices as well. This could result in behavioural impacts to seals and otters (typically near shoreline), and cetaceans and basking sharks (offshore) with the likelihood of avoidance during installation and operation. But there are significant unknowns on disturbance effects (likely site-specific), and noise levels that are actually generated by these devices. Acute effects to fauna are considered unlikely, and impacts are considered likely to be most significant during piling and drilling activities.

The potential for disturbance impacts to marine fauna ( i.e. seals, otters) from above surface noise has been identified during maintenance and installation works ( i.e. machinery, vessels).

Shock Waves

Potential for shock or pressure waves from large waves hitting the side of surface-piercing structures with high profiles above the water surface (offshore devices only). The magnitude of any impacts and their effects on these species is not currently known, although the potential for adverse impacts to seals, cetaceans, otter and basking shark has been identified.

EMF

While no EMF impacts have been identified from the devices, there is the potential for EMF impacts from underwater cabling and grid connections. Further information is required to determine the potential susceptibility of marine fauna and likely effects associated with this issue.

Physical Barrier

Introduction of new structures at, or close to, the shoreline could disrupt routes to/from feeding grounds. Similarly, the physical presence of new structures in the upper water column may disrupt movements or migration of marine fauna. Unknowns over movements and migration routes ( i.e. basking sharks), patterns of movement of other species ( i.e. seals, otters), whether any moorings or device components will be perceived or if fauna will simply alter their movement accordingly around them. Shoreline devices may restrict movement for seals, otters and other land-based fauna more than offshore ( e.g. potentially greater alternatives for movement around devices offshore, placement of devices in shoreline habitats, etc.).

The potential for collisions for marine fauna with devices and their moorings may exist, although this will be largely dependent on the size and design of the device ( i.e. perceptibility), the location of the device ( i.e. proximity to seal haul out zones, etc.) and the response of the animal. Avoidance is likely for some species, but any impact could be fatal in some instances if it were to occur ( i.e. seals, otters, cetaceans, basking shark).

Collision with or entanglement in mooring lines associated with offshore devices is considered possible, particularly for larger species ( i.e. minke whales which are more prone to entanglement than other ondontocetes/toothed whales) and larger devices with several mooring lines. The potential for entrapment of marine fauna within the chamber/reservoir of devices such as the water column device (likely offshore for larger fauna, shoreline for smaller marine fauna) may also exist. However, whether either could actually occur and its significance is unknown. It is noted that while it may result in injury or fatality, such occurrences are considered unlikely.

Displacement

The potential displacement of shoreline habitats with the installation of shoreline devices ( i.e. device footprint and infrastructure) will likely lead to displacement of fauna, particularly seals, otters, birds, etc. In most cases, the impact of this is likely to be site-specific and dependant on the availability of alternative habitats, siting options, activities displaced ( i.e. haul out, breeding areas), etc.

In general terms, the potential displacement of species due to the presence of offshore devices or associated structures, disturbance during installation, operation or decommissioning ( i.e. noise, turbulence, vibration, displacement of prey, etc.) is likely to be site-specific and would depend on a range of other factors (suitable alternative sites, importance of habitat, etc.). This will also likely depend on what activities are being displaced and their importance ( e.g. Basking sharks avoiding of structures or installation/servicing vessel activities may lead to the displacement of foraging activities or courtship behaviour).

Fauna:

Attraction of Fauna

Bird aggregation utilising above water infrastructure may occur, particularly during calm water periods (if any) and if located in foraging waters.

Noise

Potential for underwater noise impacts on marine fauna, from drilling/installation works ( i.e. anchoring works, etc.) or from machinery housing in floating or subsurface structures associated with offshore devices. This may also occur with installation works at the shoreline as well, although noise from equipment housed onshore is unlikely as these devices are likely to be located in areas with high background noise ( i.e. the shoreline, waves breaking, etc.).

There is the potential for behavioural impacts to seals and otters (typically in near-shore areas), and cetaceans and basking sharks (offshore) with the potential for some small-scale avoidance during installation and/or operation (offshore). However, there are significant unknowns on disturbance effects (likely to be site-specific), and on the noise levels that are actually generated. Acute effects are considered unlikely. Impacts are likely to be most significant during piling and drilling activities.

The potential for disturbance impacts to marine fauna ( i.e. seals, otters) from above surface noise has been identified, particularly during installation works ( i.e. machinery, vessels) and where floating device structures house noise-generating equipment. This disturbance may be greater for those devices at or near the shoreline, however, there are also significant unknowns on the specific effects of this disturbance given that they are likely to be site-specific.

EMF

While no EMF impacts have been identified from the devices, there is the potential for EMF impacts from underwater cabling and grid connections. Further information is required to determine the potential susceptibility of marine fauna and likely effects associated with this issue.

Physical Barrier

The introduction of new structures at, or close to, the shoreline could disrupt routes to/from feeding grounds. Similarly, the physical presence of new structures in the upper water column may disrupt movements or migration of marine fauna. Unknowns over movements and migration routes ( i.e. basking sharks), patterns of movement of other species ( i.e. seals, otters), whether moorings and devices will be perceived or if they will simply alter their movement accordingly around offshore devices. Near-shore or shoreline devices may restrict movement for seals, otters and other land-based fauna more than offshore ( e.g. potentially greater alternatives for movement around devices offshore, shoreline habitats).

The potential for collisions for marine fauna with devices and moorings may exist, although this will be largely dependent on the size and design of the device ( i.e. perceptibility), the location of the device ( i.e. proximity to seal haul out zones, etc.) and the response of the animal. The potential for injury to species "captured" within the device basin has been identified, and any such impacts from machinery within the device ( i.e. turbines, etc.) could be fatal if it were to occur ( i.e. seals, otters, cetaceans, basking shark).

Collision with or entanglement in mooring lines associated with offshore devices is considered possible, particularly for larger species ( i.e. minke whales which are more prone to entanglement than other ondontocetes/toothed whales) and larger devices equipped with several mooring lines. The potential for entrapment of marine fauna within the chamber reservoir of these devices (likely offshore for larger fauna, shoreline for smaller marine fauna) has also been identified and may also exist and could potentially be fatal if it did occur. However, whether either could actually occur is unknown, and such occurrences are considered unlikely.

Displacement

The potential displacement of shoreline habitats with the installation of shoreline devices ( i.e. device footprint and infrastructure) may lead to displacement of fauna, particularly seals, otters, birds, etc. In most cases, the impact of this is likely to be site-specific and dependant on the availability of alternative habitats, siting options, activities displaced ( i.e. haul out, breeding areas), etc.

In general terms, the potential displacement of species from the presence of devices or associated structures, disturbance during installation, operation or decommissioning ( i.e. noise, turbulence, vibration, displacement of prey, etc.) is likely to be site-specific and would depend on a range of other factors (suitable alternative sites, importance of habitat, etc.). This is also likely to depend on what activities are being displaced and their importance ( e.g. Basking sharks avoiding of structures or installation/servicing vessel activities may lead to the displacement of foraging activities or courtship behaviour).

Birds:

Collision

No collision risk identified in relation to wave devices for diving birds. The potential may exist for the aggregation of some seabirds on the top of surface-piercing devices ( e.g. Penguin), particularly during calmer conditions.

Noise

Potential risk of underwater noise during installation, operation and decommissioning works of offshore devices has been identified. Increased noise levels are likely in drilling activities and installation of rock anchors if used. However, there are significant unknowns around the magnitude the impacts from installation and operation of these devices on diving bird populations, although it could potentially be damaging and create sufficient disturbance for displacement.

Potential for noise impacts from generators and machinery located above the water surface. While high energy environments are likely to have high levels of background noise, this could create disturbances if located near coastal breeding sites. Noise within devices is likely to be low and constant and the effects are unknown, as effects of increased/altered noise levels are not known for birds at present (displacement/avoidance, impacts to foraging success, etc.).

It is noted that the levels of underwater noise from the presence and operation of this device in offshore areas, is not currently known. Further the importance of hearing underwater for birds, threshold levels and the likelihood of any impacts are also unknown. Potential impacts may include displacement, avoidance, reduction in foraging success, no effect, etc.

Disturbance and Displacement

Potential for displacement of birds during installation and operation, but this is likely to be dependent on other factors ( i.e. sensitivity of habitats, availability of suitable alternative habitats) and may only be temporary ( e.g. birds may become accustomed to devices). Likely dependent on site-specific conditions, including the sensitivity of species and the activities displaced ( i.e. breeding, foraging, moulting, etc.).

Potential for visual disturbance if surface-piercing components are present, with potential for greater impacts if located near-shore and close to coastal breeding and moulting sites, or offshore near foraging areas. However, the likelihood of impacts is presently unknown.

In such instances, birds in flight may operate in a broadly similar way and use similar avoidance tactics to those employed when encountering other natural and man-made obstructions ( i.e. by taking alternative flight routes, avoiding obstructions to a greater degree at night, etc.).

Predation

The 2007 Marine Renewables SEA raised the potential risk of increased mink colonisation of offshore islands due to the creation of islet chains between Scotland's western isles from the placement of devices with surface structures. Impacts such as increased predation on ground-nesting birds were identified. However, it is noted that there is no documented evidence indicating the likelihood of this occurring.

Birds:

Collision

As a water surface type device, no collision risk identified in relation to wave devices for diving birds. The potential may exist for the aggregation of some seabirds on the top of surface-piercing devices, particularly during calmer conditions.

Noise

Potential risk of underwater noise during installation, operation and decommissioning works of offshore devices has been identified. Increased noise levels are likely in drilling activities and installation of rock anchors if used. However, there are significant unknowns around the magnitude the impacts from installation and operation of these devices on diving bird populations, although it could potentially be damaging and create sufficient disturbance for displacement.

There is the potential for noise impacts from generators and machinery located above the water surface. While high energy environments are likely to have high levels of background noise, this could create disturbances if located near coastal breeding sites or in foraging sites located offshore. Noise within devices is likely to be low and constant and the specific effects are unknown at present, particularly the effects of increased/altered noise levels are not known for birds at present (displacement/avoidance, impacts to foraging success, etc.).

It is noted that the levels of underwater noise from the presence and operation of this device in offshore areas, is not currently known. Further the importance of hearing underwater for birds, threshold levels and the likelihood of any impacts are also unknown. Potential impacts may include displacement, avoidance, reduction in foraging success, no effect, etc.

Disturbance and Displacement

Potential for displacement during installation and operation, but dependant on other factors ( i.e. sensitivity of habitats, availability of suitable alternative habitats) and may only be temporary as fauna become accustomed to the devices. They are likely to be dependent on site-specific including the sensitivity of species and the activities displaced ( i.e. breeding, foraging, moulting, etc.).

Potential for visual disturbance if surface-piercing components are present, with potential for greater impacts if close to coastal breeding and moulting sites, or offshore near foraging areas. The likelihood of impacts is unknown. In such instances, birds may operate in a broadly similar way and use similar avoidance tactics to those employed when encountering other natural and man-made obstructions ( i.e. by taking alternative flight routes, avoiding obstructions to a greater degree at night).

Predation

The 2007 Marine Renewables SEA raised the potential risk of increased mink colonisation of offshore islands due to the creation of islet chains between Scotland's western isles from the placement of devices with surface structures. Impacts such as increased predation on ground-nesting birds were identified. However, it is noted that there is no documented evidence indicating the likelihood of this occurring.

Birds:

Collision

No collision risk identified in relation to wave devices for diving birds. The potential may exist for the aggregation of some seabirds on the top of surface-piercing devices, particularly during calmer conditions.

Turbulence and impacts on foraging

Localised changes in turbulence in the water column from the presence and operation of groups of these devices may have the potential to affect the foraging success of marine birds. However, the extent and nature of any potential effects is not currently known and may be difficult to identify a causal link between the two.

Noise

Potential risk of underwater noise during installation, operation and decommissioning works of offshore devices has been identified. Increased noise levels are likely in drilling activities and installation of rock anchors if used for the support structures. However, there are significant unknowns around the magnitude the impacts from installation and operation of these devices on diving bird populations, although it could potentially be damaging and create sufficient disturbance for displacement.

There is the potential for noise impacts from generators and machinery located above the water surface. While high energy environments are likely to have high levels of background noise, this could create disturbances if located near coastal breeding sites. However, any noise within devices is likely to be low and constant and the effects are unknown, as effects of increased/altered noise levels are not known for birds at present (displacement/avoidance, impacts to foraging success, etc.).

It is noted that the levels of underwater noise from the presence and operation of this device in offshore areas, is not currently known. Further the importance of hearing underwater for birds, threshold levels and the likelihood of any impacts are also unknown. Potential impacts may include displacement, avoidance, reduction in foraging success, no effect, etc.

Disturbance and Displacement

There is the potential for displacement during installation and operation, but this will likely be dependent on other factors ( i.e. sensitivity of habitats, type of bird species, availability of suitable alternative habitats and foraging areas) and may only be temporary as fauna become accustomed to the devices. It is also likely to be dependent on site-specific factors including the sensitivity of species and the activities displaced ( i.e. breeding, foraging, moulting, etc.).

There may be the potential for visual disturbance, if surface-piercing components are present on the device. Any such impacts are likely to be greater for near-shore devices ( i.e. close to coastal breeding and moulting sites, or offshore near foraging areas). However, the likelihood of impacts is currently unknown. In such instances, birds may operate in a broadly similar way and use similar avoidance tactics to those employed when encountering other natural and man-made obstructions ( i.e. by taking alternative flight routes, avoiding obstructions to a greater degree at night).

Predation

The 2007 Marine Renewables SEA raised the potential risk of increased mink colonisation of offshore islands due to the creation of islet chains between Scotland's western isles from the placement of devices with surface structures. Impacts such as increased predation on ground-nesting birds were identified. However, it is noted that there is no documented evidence indicating the likelihood of this occurring.

Birds:

Collision

No collision risk identified in relation to wave devices for diving birds. The potential may exist for the aggregation of some seabirds on the top of surface-piercing devices, particularly during calmer conditions.

Turbulence and impacts on foraging

Localised changes in turbulence in the water column from the presence and movement of these devices, and presence of any support structure, may have the potential to affect the foraging success of marine birds. However, the extent and nature of any potential effects is not currently known and may be difficult to identify a causal link between the two.

Noise

Potential risk of underwater noise during installation, operation and decommissioning works of offshore devices has been identified. Increased noise levels are likely in drilling activities and installation of rock anchors if used. It is noted that there are significant unknowns around the magnitude the impacts from installation and operation of these devices on diving bird populations, although it could potentially be damaging and create sufficient disturbance for displacement.

The presence of noise-generating components in the device itself may also present the potential for disturbance. However, it is also noted that the levels of underwater noise from the presence and operation of this device in offshore areas, is not currently known. Further the importance of hearing underwater for birds, threshold levels and the likelihood of any impacts are also unknown. Potential impacts may include displacement, avoidance, reduction in foraging success, no effect, etc.

Disturbance and Displacement

Potential for displacement during installation and operation, but dependant on other factors ( i.e. sensitivity of habitats, availability of suitable alternative habitats) and may only be temporary as fauna become accustomed to the devices. This is likely dependant on site-specific including the sensitivity of species and the activities displaced ( i.e. breeding, foraging, moulting, etc.).

No surface-piercing components are identified, and hence no visual disturbance impacts are considered likely.

Birds:

Collision

As the device is largely located on the water surface, no collision risk identified in relation to wave devices for diving birds. The potential may exist for the aggregation of some seabirds on the top of surface-piercing devices, particularly during calmer conditions.

Noise

Potential risk of underwater noise during installation, operation and decommissioning works of offshore devices has been identified. Increased noise levels are likely in drilling activities and installation of rock anchors (if used). However, there are significant unknowns around the magnitude the impacts from installation and operation of these devices on diving bird populations. It is noted that this could potentially be damaging and create sufficient disturbance for displacement.

The potential for above water noise impacts from generators housed within shoreline devices and above the water surface in near-shore devices, may occur for a wide range of bird species and coastal breeding sites. However, the noise generated within these devices is likely to be low level and constant and the high energy environments that are likely to host these wave devices are also likely to have high levels of background noise. In general, the likely effects of increased/altered noise levels are not known for birds at present (displacement/avoidance, impacts to foraging success, etc.).

It is noted that the actual levels of underwater noise from the presence and operation of this device in offshore areas, is not currently known. Furthermore, the importance of hearing underwater for birds, threshold levels and the likelihood of any impacts are also unknown. Potential impacts may include displacement, avoidance, reduction in foraging success, no effect, etc.

Disturbance and Displacement

The potential for displacement of bird populations during installation and operation, particularly the construction of large units and associated infrastructure in shoreline areas ( i.e. construction disturbance and displacement of areas used by birds) has been identified. Any impacts from shoreline and offshore devices are likely dependent on other factors including the sensitivity of species and habitats, availability of suitable alternative habitats, activities displaced ( i.e. breeding, foraging, moulting, etc.). In some instances, disturbance may only be temporary until fauna become accustomed to the devices.

Potential for visual disturbance from above surface components in both onshore and offshore areas, with potential for significant impacts if close to coastal breeding and moulting sites, or offshore near foraging areas. The likelihood of impacts is currently not known. In such instances, birds may operate in a broadly similar way and use similar avoidance tactics to those employed when encountering other natural and man-made obstructions ( i.e. by taking alternative flight routes, avoiding obstructions to a greater degree at night).

Predation

The 2007 Marine Renewables SEA raised the potential risk of increased mink colonisation of offshore islands due to the creation of islet chains between Scotland's western isles from the placement of devices with surface structures (offshore only). Impacts such as increased predation on ground-nesting birds were identified. However, it is noted that there is no documented evidence indicating the likelihood of this occurring.

Birds:

Collision

As the device is largely located on the water surface, no collision risk identified in relation to wave devices for diving birds. The potential may exist for the aggregation of some seabirds on the top of surface-piercing devices, particularly during calmer conditions and if fish are captured in the overtopping basin portion of the device.

Noise

Potential risk of underwater noise during installation, operation and decommissioning works of offshore devices has been identified. Increased noise levels are likely in drilling activities and installation of rock anchors for offshore devices (if used). However, there are significant unknowns around the magnitude of the impacts from installation and operation of these devices on diving bird populations. It is noted that this could potentially be damaging and create sufficient disturbance for displacement.

The potential for above water noise impacts from generators within shoreline devices and in near-shore devices, may impact on a wide range of bird species and coastal breeding sites if located nearby. However, noise within devices is likely to be low level and constant, and the high energy environments that are likely to host these wave devices are also likely to have high levels of background noise. The likely effects of increased/altered noise levels are not known for birds at present (displacement/avoidance, impacts to foraging success, etc.).

It is noted that the levels of underwater noise from the presence and operation of this device in offshore areas, is not currently known. Furthermore, the importance of hearing underwater for birds, threshold levels and the likelihood of any impacts are also unknown. Potential impacts may include displacement, avoidance, reduction in foraging success, no effect, etc.

Disturbance and Displacement

The potential for displacement of bird populations during installation and operation, particularly the construction of large units and associated infrastructure in shoreline areas ( i.e. construction disturbance and displacement of areas used by birds) has been identified. Any impacts onshore and offshore are likely dependant on other factors including the sensitivity of species and habitats, availability of suitable alternative habitats, activities displaced ( i.e. breeding, foraging, moulting, etc.). In some instances, disturbance may only be temporary until fauna become accustomed to the devices.

Potential for visual disturbance from above surface components in both onshore and offshore areas, with potential for greater impacts if close to coastal breeding sites and moulting sites. The likelihood of impacts is unknown. In such instances, birds may operate in a broadly similar way and use similar avoidance tactics to those employed when encountering other natural and man-made obstructions ( i.e. by taking alternative flight routes, avoiding obstructions to a greater degree at night).

Predation

The 2007 Marine Renewables SEA raised the potential risk of increased mink colonisation of offshore islands due to the creation of islet chains between Scotland's western isles from the placement of devices with surface structures (offshore only). Impacts such as increased predation on ground-nesting birds were identified. However, it is noted that there is no documented evidence indicating the likelihood of this occurring.

Benthic Habitats and Water Column:

Habitat Changes

The presence of these devices in the water column and their seabed moorings have the potential to contribute to habitat changes in a number of ways. In general, impacts on seabed habitats from the devices themselves are likely limited to wave energy dissipation, tidal flows and flux changes and deposition due in large to the presence of structures in the water column. These potential impacts can create adverse impacts to both benthic habitats and their species.

Other impacts, such as scouring, deposition, abrasion, smothering and the potential for loss of habitat from placement of anchors on the seabed and mooring lines in the water column have also been identified. These may also occur due to wave and coastal process changes.

Direct seabed impacts such as scouring and deposition/siltation have the potential to affect benthic habitats in a range of ways including the introduction of variations and shifts in grain size of sediments affecting habitat character and species distribution; shading or smothering of benthic areas changes in species distribution via interference with filter feeders, inhibiting respiration and reproduction, and reducing food sources for other species supported by these habitats; and leading to wider changes in ecosystem composition. In some instances, this may also result in changes to the shoreline and coastline.

Sediment Dynamics and Wave Dissipation

Changes in sediment dynamics due to the presence of moorings for these devices (gravity anchors and mooring lines) may occur, with the potential for associated changes to coastal processes via the dissipation of wave energy, and impacts such as scouring, deposition/siltation and smothering. While likely site specific, the potential for impacts in a range of UK Biodiversity Action Plan ( BAP) habitats has been identified:

  • Changes in sediment dynamics in high energy littoral rock (including BAP habitat Tidal Swept Channels) due to moorings. Impacts unlikely but may have potential impacts for F. distichus. Wave dissipation effects may adversely impact filter feeders ( i.e. M. edulis, S. allantoides) due to food dissipation and smothering, and create suitable conditions for other fucoid species to outcompete F. distichus.
  • Changes in sediment dynamics in Moderate energy littoral rock (including BAP habitat under boulder communities) due to moorings. Impacts unlikely but may have potential impacts on under-boulder communities ( BAP).
  • Changes in sediment dynamics in Littoral biogenic reefs (including BAP habitat blue mussel beds) due to moorings. Decreases in wave action may adversely impact filter feeders ( i.e. M. edulis) and reduced availability of sediment available for others ( i.e. S. alveolata). Impacts are unlikely as many of these species are common, but there may be the potential for impacts for blue mussel beds if present.
  • Changes in sediment dynamics in Features of littoral sediment (including BAP habitat blue mussel beds) due to moorings. Decreases in wave action may adversely impact filter feeders ( i.e. M. edulis). Impacts unlikely as many of these species are common, but there may be the potential for impacts for blue mussel beds if present.
  • Changes in sediment dynamics in sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, horse mussel beds) due to moorings. Impacts may influence scouring, deposition and smothering, whilst affecting sediment grain sizes and impacting on the habitat and species in these areas ( i.e. E. timida). Decreases in wave action may adversely impact filter feeders ( i.e. A. fragilis). Impacts are unlikely and these species are common, but there may be the potential for impacts for A. fragilis, C. cruoriaeformis, D. Montagnei, E. timida or horse mussel beds if present.
  • Changes in sediment dynamics in Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds) due to moorings. Impacts may influence scouring, deposition and smothering, whilst affecting sediment grain sizes and impacting on the habitat and species in these areas ( i.e. E. timida). Decreases in wave action may adversely impact filter feeders ( i.e. A. fragilis) through reduced food supplies and siltation. While impacts are unlikely, there may be the potential for impacts for A. fragilis, E. timida or A. sarsi or blue mussel beds if present.
  • Changes in sediment dynamics in Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds) due to moorings. Impacts may influence scouring, deposition and smothering, whilst affecting sediment grain sizes and impacting on the habitat and species in these areas ( i.e. E. timida). Decreases in wave action or tidal flows may adversely impact filter feeders ( i.e. A. fragilis) through reduced food supplies and siltation. While impacts are considered unlikely, there may be the potential for impacts for A. fragilis, D. Montagnei, E. timida or A. sarsi, horse mussel beds or file shell beds if present.
  • Changes in sediment dynamics in Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds) due to moorings. Impacts may influence scouring, deposition and smothering. Wave dissipation may also affect species competition ( i.e. seaweeds and filter feeders with reductions in exposure and food supplies) and changes in sediment dynamics. While impacts are unlikely, there may be the potential for impacts for A. fragilis, C. cruoriaeformis, D. Montagnei, P. calcareum, L. corallioides, horse mussel beds or blue mussel beds or maerl beds present.
  • Changes in sediment dynamics in Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds) due to moorings. This may influence scouring, deposition and smothering. Wave dissipation also has the potential to impact of filter feeders ( i.e. reduced food supplies, siltation, migration of some species to shallow water depths) thus potentially affecting the overall habitat. While impacts are unlikely, there may be the potential to affect horse mussel beds, cold coral reefs or blue mussel beds if present.
  • Changes in sediment dynamics in Atlantic and Mediterranean high energy circalittoral rock (including BAP habitat Tidal Swept Channels) due to moorings. Potential impacts for habitat and S. pallida as it is nationally scarce.
  • Changes in sediment dynamics in Atlantic and Mediterranean moderate energy circalittoral rock due to moorings. Potential impacts for S. spinulosa, A dohrnii and S. pallida.
  • Changes in sediment dynamics in circalittoral rock features due to moorings. Impacts are not considered likely, but included due to potential as this habitat is seldom recorded.

Change in Tidal Flows and Fluxes

Changes, predominantly decreases in tidal flows may have adverse effects on benthic areas, although these are expected to be site and habitat specific:

  • Changes in tidal flows and fluxes in Sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, horse mussel beds) due to moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if C. cruoriaeformis, D. Montagnei, E. timida, A. sarsi or horse mussel beds are present.
  • Changes in tidal flows and fluxes in Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds) due to moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if A. fragilis, E. timida, A. sarsi or blue mussel beds are present.
  • Changes in tidal flows and fluxes in Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds) due to moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if A. fragilis, E. timida, A. sarsi, horse mussel beds or file shell beds are present.
  • Changes in tidal flows and fluxes in Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds) due to moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if A. fragilis, C. cruoriaeformis, D. Montagnei, P. calcareum, L. corallioides, horse mussel beds or blue mussel beds or maerl beds present.
  • Changes in tidal flows and fluxes in Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds) due to moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur and increase competition between kelp species ( i.e. A. esculenta) associated with changing flow rates. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if horse mussel beds, cold coral reefs or blue mussel beds if present.

Scouring and Deposition

While likely site specific, this may present a potential risk to BAP species such as mussel beds, M. edulis, and filter feeders, with secondary impacts up the food chain ( i.e. affecting predatory species that feed on them). The potential for scouring in a range of BAP habitats has been identified for offshore devices:

  • Increased scour and potential for deposition of sediment ( i.e. smothering, inhibiting respiration, feeding and growth) in sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, blue mussel beds) if A. fragilis, C. cruoriaeformis, D. Montagnei, E. timida or horse mussel beds are present.
  • Increased scour and deposition of sediment ( i.e. smothering, inhibiting respiration, feeding and growth) in Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds) if A. fragilis, E. timida, A sarsi or blue mussel beds are present.
  • Increased scour and deposition of sediment ( i.e. smothering, inhibiting respiration, feeding and growth) in Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds). Considered unlikely but has potential for impacts if A. fragilis, D. Montagnei, E. timida, A sarsi, horse mussel beds or file shell beds are present.
  • Increased scour and deposition of sediment ( i.e. smothering, inhibiting respiration, feeding and growth) in Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds). Considered unlikely, but noted as a potential impact particularly if C. cruoriaeformis, D. Montagnei, P. calcareum, L. corallioides, horse mussel beds, blue mussel beds or maerl beds are present
  • Scouring in Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds) if horse mussel beds, cold water coral reefs or blue mussel beds are present.
  • Potential for deposition of sediments in littoral biogenic reefs (including BAP habitat blue mussel beds) if blue mussel beds are present. While deposition unlikely in high-energy environments, raised as potential issue due to presence of BAP habitats.
  • Potential for deposition of sediment in features of littoral sediment (including BAP habitat blue mussel beds) if blue mussel beds are present. May impact on habitat character.
  • Potential for deposition of sediment on filter feeders in circalittoral rock features. Included due to potential; for impacts ( i.e. smothering) although this is considered unlikely for arrays up to 10 MW).

Loss of Habitat/Abrasion

The direct placement of offshore or near-shore devices, and/or their moorings on the seabed can result in damage to benthic habitats, or their loss in extreme instances ( e.g. seabed structures, piling, drilling and anchoring, subsea cable placement).

This could also include additional damage such as the abrasion of benthic areas by mooring lines in the placement process. The potential for abrasion of marine habitats and sessile/sedentary species ( i.e. BAP species such as mussel and file shell beds) from the installation of infrastructure and subsea cabling ( i.e. cables dragging during installation) has been identified at in the following habitats:

  • Atlantic and Mediterranean moderate energy infralittoral rock (including BAP habitat Tidal Swept Channels and Sabellaria spinulosa reefs).
  • Atlantic and Mediterranean high energy circalittoral rock (including BAP habitat Tidal Swept Channels).
  • Atlantic and Mediterranean moderate energy circalittoral rock.
  • Sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, horse mussel beds).
  • Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds).
  • Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds).
  • Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds).
  • Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds).

Benthic Habitats and Water Column:

Habitat Changes

The presence of these devices at the water surface is and their seabed moorings or structures have the potential to contribute to habitat changes in a number of ways. In general, impacts on seabed habitats from the devices themselves are likely limited given their presence at the water surface only. As such, wave energy dissipation and potential impacts if placed in or near a mixing zone are the likely impacts. The main impacts to benthic habitats are likely to be from the presence of mooring cables and structures on the seabed.

The potential for impacts will likely depend on the type of mooring ( i.e. gravity/deadweight anchor, gravity base structure, rock anchors, etc.) and may involve effects such as scouring, deposition, abrasion, smothering, loss of habitat from placement of mooring anchors on the seabed, and mooring lines in the water column have also been identified. These may also occur due to wave and coastal process changes.

Direct seabed impacts such as scouring and deposition/siltation have the potential to affect benthic habitats in a range of ways including the introduction of variations and shifts in grain size of sediments affecting habitat character and species distribution; shading or smothering of benthic areas changes in species distribution via interference with filter feeders, inhibiting respiration and reproduction, and reducing food sources for other species supported by these habitats; and leading to wider changes in ecosystem composition. In some instances, this may also result in changes to the shoreline and coastline.

Sediment Dynamics and Wave Dissipation

Changes in sediment dynamics due to the presence of moorings for these devices (gravity anchors and mooring lines) may occur. In offshore areas, there may be the potential for associated changes to coastal processes via the dissipation of wave energy, and impacts such as scouring, deposition/siltation and smothering. While likely site specific, the potential for impacts in a range of BAP habitats has been identified:

  • Changes in sediment dynamics in high energy littoral rock (including BAP habitat Tidal Swept Channels) due to moorings. Impacts unlikely but may have potential impacts for F. distichus. Wave dissipation effects may adversely impact filter feeders ( i.e. M. edulis, S. allantoides) due to food dissipation and smothering, and create suitable conditions for other fucoid species to outcompete F. distichus.
  • Changes in sediment dynamics in Moderate energy littoral rock (including BAP habitat Under boulder communities) due to moorings. Impacts unlikely but may have potential impacts on under-boulder communities ( BAP).
  • Changes in sediment dynamics in Littoral biogenic reefs (including BAP habitat blue mussel beds) due to moorings. Decreases in wave action may adversely impact filter feeders ( i.e. M. edulis) and reduced availability of sediment available for others ( i.e. S. alveolata). Impacts unlikely and these species are common, but there may be the potential for impacts for blue mussel beds if present.
  • Changes in sediment dynamics in Features of littoral sediment (including BAP habitat blue mussel beds) due to moorings. Decreases in wave action may adversely impact filter feeders ( i.e. M. edulis). Impacts unlikely and these species are common, but there may be the potential for impacts for blue mussel beds if present.
  • Changes in sediment dynamics in Sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, horse mussel beds) due to moorings. Impacts may influence scouring, deposition and smothering, whilst affecting sediment grain sizes and impacting on the habitat and species in these areas ( i.e. E. timida). Decreases in wave action may adversely impact filter feeders ( i.e. A. fragilis), and while impacts are unlikely and these species are common, but there may be the potential for impacts for A. fragilis, C. cruoriaeformis, D. Montagnei, E. timida or horse mussel beds if present.
  • Changes in sediment dynamics in Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds) due to moorings. Impacts may influence scouring, deposition and smothering, whilst affecting sediment grain sizes and impacting on the habitat and species in these areas ( i.e. E. timida). Decreases in wave action may adversely impact filter feeders ( i.e. A. fragilis) through reduced food supplies and siltation, and while impacts are unlikely, there may be the potential for impacts for A. fragilis, E. timida or A. sarsi or blue mussel beds if present.
  • Changes in sediment dynamics in Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds) due to moorings. Impacts may influence scouring, deposition and smothering, whilst affecting sediment grain sizes and impacting on the habitat and species in these areas ( i.e. E. timida). Decreases in wave action or tidal flows may adversely impact filter feeders ( i.e. A. fragilis) through reduced food supplies and siltation, and while impacts are considered unlikely, there may be the potential for impacts for A. fragilis, D. Montagnei, E. timida or A. sarsi, horse mussel beds or file shell beds if present.
  • Changes in sediment dynamics in Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds) due to moorings. Impacts may influence scouring, deposition and smothering. Wave dissipation may also affect species competition ( i.e. seaweeds and filter feeders with reductions in exposure and food supplies) and changes in sediment dynamics, and while impacts are unlikely, there may be the potential for impacts for A. fragilis, C. cruoriaeformis, D. Montagnei, P. calcareum, L. corallioides, horse mussel beds or blue mussel beds or maerl beds present.
  • Changes in sediment dynamics in Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds) due to moorings. This may influence scouring, deposition and smothering. Wave dissipation also has the potential to impact of filter feeders ( i.e. reduced food supplies, siltation, migration of some species to shallow water depths) thus potentially affecting the overall habitat. While impacts from wave dissipation are unlikely, there may be the potential to affect horse mussel beds, cold coral reefs or blue mussel beds if present.
  • Changes in sediment dynamics in Atlantic and Mediterranean high energy circalittoral rock (including BAP habitat Tidal Swept Channels) due to moorings. Potential impacts for habitat and S. pallida as it is nationally scarce.
  • Changes in sediment dynamics in Atlantic and Mediterranean moderate energy circalittoral rock due to moorings. Potential impacts for S. spinulosa, A dohrnii and S. pallida.
  • Changes in sediment dynamics in circalittoral rock features due to moorings. Impacts are not considered likely, but included due to potential as this habitat is seldom recorded.

Change in Tidal Flows and Fluxes

There are likely to be limited tidal flows and fluxes within suitable development areas for this device, and any impacts from device moorings are expected to be site and habitat specific. However, the potential for impacts via decreases in tidal flows may have adverse effects:

  • Changes in tidal flows and fluxes in Sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, horse mussel beds) due to moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if C. cruoriaeformis, D. Montagnei, E. timida, A. sarsi or horse mussel beds are present.
  • Changes in tidal flows and fluxes in Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds) due to moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if A. fragilis, E. timida, A. sarsi or blue mussel beds are present.
  • Changes in tidal flows and fluxes in Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds) due to moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if A. fragilis, E. timida, A. sarsi, horse mussel beds or file shell beds are present.
  • Changes in tidal flows and fluxes in Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds) due to moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if A. fragilis, C. cruoriaeformis, D. Montagnei, P. calcareum, L. corallioides, horse mussel beds or blue mussel beds or maerl beds present.
  • Changes in tidal flows and fluxes in Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds) due to moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur and increase competition between kelp species ( i.e. A. esculenta) associated with changing flow rates. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if horse mussel beds, cold coral reefs or blue mussel beds if present.

Scouring and Deposition

While likely site specific, the presence of mooring systems associated with these devices may present a potential risk to BAP species such as mussel beds, M. edulis, and filter feeders, with secondary impacts up the food chain ( i.e. affecting predatory species that feed on them). The potential for scouring in a range of BAP habitats has been identified:

  • Increased scour in sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, blue mussel beds) if A. fragilis, C. cruoriaeformis, D. Montagnei, E. timida or horse mussel beds are present. Also potential for deposition of sediment due to moorings was raised due to the potential presence of these species.
  • Scouring in Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds) if A. fragilis, E. timida, A sarsi or blue mussel beds are present. Also potential for deposition of sediment due to moorings was raised due to the potential presence of these species.
  • Scouring in Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds) if A. fragilis, D. Montagnei, E. timida, A sarsi, horse mussel beds or file shell beds are present. Also potential for deposition of sediment due to moorings was raised due to the potential presence of these species.
  • Scouring in Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds) if C. cruoriaeformis, D. Montagnei, P. calcareum, L. corallioides, horse mussel beds, blue mussel beds or maerl beds are present. Also potential for deposition of sediment due to moorings was raised due to the potential presence of these species.
  • Scouring in Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds) if horse mussel beds, cold water coral reefs or blue mussel beds are present. Also potential for deposition of sediment due to moorings was raised due to the potential presence of these species.
  • Potential for deposition of sediments at moorings in littoral biogenic reefs (including BAP habitat blue mussel beds) if blue mussel beds are present. While deposition unlikely in high-energy environments, raised as potential issue due to presence of BAP habitats.
  • Potential for deposition of sediments due to moorings in littoral biogenic reefs (including BAP habitat blue mussel beds) if blue mussel beds are present. While deposition unlikely in high-energy environments, raised as potential issue due to presence of BAP habitats.
  • Potential for deposition of sediment due to moorings in features of littoral sediment (including BAP habitat blue mussel beds) if blue mussel beds are present. May impact on habitat character.

Loss of Habitat/Abrasion

The placement of moorings on the seabed can result in damage to benthic habitats, and in some instances, their loss ( e.g. seabed structures, piling, drilling and anchoring, subsea cable placement). This can also include additional damage such as the abrasion of benthic areas by mooring lines in the placement process.

The potential for abrasion of marine habitats and sessile/sedentary species ( i.e. BAP species such as mussel and file shell beds) from the installation of infrastructure ( i.e. mooring cables dragging during installation) and subsea cabling ( i.e. placement and dragging during installation and operation) has been identified at:

  • Atlantic and Mediterranean high energy circalittoral rock (including BAP habitat Tidal Swept Channels).
  • Atlantic and Mediterranean moderate energy circalittoral rock.
  • Sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, horse mussel beds).
  • Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds).
  • Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds).
  • Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds).
  • Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds).

Benthic Habitats and Water Column:

Habitat Changes

The presence of these devices near the water surface, and support structure mounted on the seabed has the potential to contribute to habitat changes in a number of ways. In general, impacts on seabed habitats from the devices and their supports may include changes in sediment dynamics, scouring, deposition/siltation and vibration. Additional impacts such as wave energy dissipation, potential effects of placement in or near a mixing zone, changes in tidal flows and fluxes, and changes in turbulence due to installation and operation may also occur.

Direct seabed impacts such as scouring and deposition/siltation, and in-direct impacts from wave and tidal changes, have the potential to cause a range of adverse benthic impacts. These may include the introduction of variations and shifts in grain size of sediments, which can alter habitat character and species distribution; shading or smothering of benthic areas with sediments and the presence of the device itself; changes in species distribution via interference with filter feeders, inhibiting their respiration and reproduction; and secondary impacts such as reducing food sources for other species supported by these habitats. These may collectively lead to wider changes in ecosystem composition. In some instances, this may also result in changes to the shoreline and coastline.

Sediment Dynamics and Wave Dissipation

Changes in sediment dynamics due to the offshore presence and operation of these devices and their benthic support structures may occur during both the installation and operation phases. The operation of these devices may create the potential for associated changes to coastal processes via the dissipation of wave energy, and impacts such as scouring, deposition/siltation and smothering. While likely site specific, the potential for impacts in a range of BAP habitats has been identified:

  • Changes in sediment dynamics in high energy littoral rock (including BAP habitat Tidal Swept Channels) due to device and support structures (offshore). Impacts unlikely but may have potential impacts for F. distichus. Wave dissipation effects may adversely impact filter feeders ( i.e. M. edulis, S. allantoides) due to food dissipation and smothering, and create suitable conditions for other fucoid species to outcompete F. distichus.
  • Changes in sediment dynamics in Moderate energy littoral (including BAP habitat Under boulder communities) due to device and support structures (offshore). Impacts unlikely but may have potential impacts on under-boulder communities ( BAP).
  • Changes in sediment dynamics in Littoral biogenic reefs (including BAP habitat blue mussel beds) due to device and support structures (offshore). Decreases in wave action may adversely impact filter feeders ( i.e. M. edulis) and reduced availability of sediment available for others ( i.e. S. alveolata). Impacts unlikely and these species are common, but there may be the potential for impacts for blue mussel beds if present.
  • Changes in sediment dynamics in Features of littoral sediment (including BAP habitat blue mussel beds) due to device and support structures (offshore). Decreases in wave action may adversely impact filter feeders ( i.e. M. edulis) and while impacts are unlikely as these species are common, but there may be the potential for impacts for blue mussel beds if present.
  • Changes in sediment dynamics in Sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, horse mussel beds) due to device and support structures (offshore). Impacts may affect sediment grain size, and affect the habitat and species in these areas ( i.e. E. timida). Decreases in wave action may adversely impact filter feeders ( i.e. A. fragilis), and while impacts are unlikely and these species are common, but there may be the potential for impacts for A. fragilis, C. cruoriaeformis, D. Montagnei, E. timida or horse mussel beds if present.
  • Changes in sediment dynamics in Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds) due to device and support structures (offshore). Impacts may affect sediment grain size, and affect the habitat and species in these areas ( i.e. E. timida) and decreases in wave action may adversely impact filter feeders ( i.e. A. fragilis) through reduced food supplies and siltation, and while impacts are unlikely, there may be the potential for impacts for A. fragilis, E. timida or A. sarsi or blue mussel beds if present.
  • Changes in sediment dynamics in Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds) due to device and support structures (offshore). Impacts may affect sediment grain size, and affect the habitat and species in these areas ( i.e. E. timida) and decreases in wave action or tidal flows may adversely impact filter feeders ( i.e. A. fragilis) through reduced food supplies and siltation, and while impacts are considered unlikely, there may be the potential for impacts for A. fragilis, D. Montagnei, E. timida or A. sarsi, horse mussel beds or file shell beds if present.
  • Changes in sediment dynamics in Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds) due to device and support structures (offshore). Wave dissipation may also affect species competition ( i.e. seaweeds and filter feeders with reductions in exposure and food supplies) and changes in sediment dynamics, and while impacts are unlikely, there may be the potential for impacts for A. fragilis, C. cruoriaeformis, D. Montagnei, P. calcareum, L. corallioides, horse mussel beds or blue mussel beds or maerl beds present.
  • Changes in sediment dynamics in Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds) due to device and support structures (offshore). Wave dissipation also has the potential to impact of filter feeders ( i.e. reduced food supplies, siltation, migration of some species to shallow water depths) thus potentially affecting the overall habitat. While impacts from wave dissipation are unlikely, there may be the potential to affect horse mussel beds, cold coral reefs or blue mussel beds if present.
  • Changes in sediment dynamics in Atlantic and Mediterranean high energy infralittoral rock (including BAP habitat Tidal Swept Channels) due to device and support structures (offshore). Potential for impacts for S. pallida, given it is nationally scarce.
  • Changes in sediment dynamics in Atlantic and Mediterranean moderate energy infralittoral rock (including BAP habitat Tidal Swept Channels and S. spinulosa reefs) due to device and support structures (offshore). Impacts unlikely for small arrays (10 MW) but potential impacts may exist for S. pallida and S. spinulosa.
  • Changes in sediment dynamics in Atlantic and Mediterranean high energy circalittoral rock (including BAP habitat Tidal Swept Channels) due to device and support structures (offshore). Potential impacts for habitat and S. pallida as it is nationally scarce.
  • Changes in sediment dynamics in Atlantic and Mediterranean moderate energy circalittoral rock due to device and support structures (offshore). Potential impacts for S. spinulosa, A dohrnii and S. pallida.
  • Changes in sediment dynamics in circalittoral rock features due to device and supports (offshore). Impacts are not considered likely, but included due to potential as this habitat is seldom recorded.

Change in Tidal Flows and Fluxes

Decreases in tidal flows and fluxes associated with these devices or their seabed-based support structures may have adverse effects, although these are expected to be site and habitat specific:

  • Changes in tidal flows and fluxes in Sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, horse mussel beds) due to device and support structures (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if C. cruoriaeformis, D. Montagnei, E. timida, A. sarsi or horse mussel beds are present.
  • Changes in tidal flows and fluxes in Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds) due to device and support structures (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if A. fragilis, E. timida, A. sarsi or blue mussel beds are present.
  • Changes in tidal flows and fluxes in Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds) due to device and support structures (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if A. fragilis, E. timida, A. sarsi, horse mussel beds or file shell beds are present.
  • Changes in tidal flows and fluxes in Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds) due to device and support structures (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if A. fragilis, C. cruoriaeformis, D. Montagnei, P. calcareum, L. corallioides, horse mussel beds or blue mussel beds or maerl beds present.
  • Changes in tidal flows and fluxes in Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds) due to device and support structures (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur and increase competition between kelp species ( i.e. A. esculenta) associated with changing flow rates. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if horse mussel beds, cold coral reefs or blue mussel beds if present.

Scouring and Deposition

While likely site specific, this may present a potential risk to BAP species such as mussel beds, M. edulis, and filter feeders, with secondary impacts up the food chain ( i.e. affecting predatory species that feed on them). The potential for scouring in a range of BAP habitats has been identified for these devices:

  • Increased scour at high tide, and deposition of sediment on algal frond surfaces in high energy littoral rock (including BAP habitat Tidal Swept Channels) if F. Distichus is present. May impact on light availability ( i.e. photosynthesis).
  • Increased scour at high tide, and deposition of sediment on algal frond surfaces in moderate energy littoral (including BAP habitat Under boulder communities) if under-boulder communities ( BAP) are present. May impact on light availability ( i.e. photosynthesis) and change character of habitat.
  • Increased scour at high tide, and potential deposition of sediment from device and support structures in littoral biogenic reefs (including BAP habitat blue mussel beds) if blue mussel beds are present. While deposition unlikely in high-energy environments, raised as potential issue due to presence of BAP habitats.
  • Increased scour at high tide, and deposition of sediment in features of littoral sediment (including BAP habitat blue mussel beds) if blue mussel beds are present. May impact on habitat character.
  • Increased scour and deposition of sediment ( i.e. smothering, inhibiting respiration, feeding and growth) in sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, blue mussel beds) if A. fragilis, C. cruoriaeformis, D. Montagnei, E. timida or horse mussel beds are present.
  • Increased scouring and deposition of sediment ( i.e. smothering, inhibiting respiration, feeding and growth) in Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds) if A. fragilis, E. timida, A sarsi or blue mussel beds are present.
  • Increased scouring and deposition of sediment ( i.e. smothering, inhibiting respiration, feeding and growth) in Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds). Considered unlikely but has potential for impacts if A. fragilis, D. Montagnei, E. timida, A sarsi, horse mussel beds or file shell beds are present.
  • Increased scouring and deposition of sediment ( i.e. smothering, inhibiting respiration, feeding and growth) in Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds). Considered unlikely, but noted as a potential impact particularly if C. cruoriaeformis, D. Montagnei, P. calcareum, L. corallioides, horse mussel beds, blue mussel beds or maerl beds are present
  • Increased scouring and deposition of sediments in Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds) if horse mussel beds, cold water coral reefs or blue mussel beds are present. May impact by smothering, hindering respiration, feeding and growth of filter feeders.
  • Potential for deposition of sediment on filter feeders in circalittoral rock features. Included due to potential; for impacts ( i.e. smothering) although this is considered unlikely for arrays up to 10 MW).

Loss of Habitat/Abrasion

The placement of these devices, and their support structures on the seabed can result in damage to benthic habitats, and loss of habitat in extreme instances ( e.g. seabed structures, piling, drilling and anchoring, subsea cable placement). This could also include additional damage such as the abrasion of benthic areas, particularly from support structure lines in the installation/placement process.

The potential for abrasion of marine habitats and sessile/sedentary species ( i.e. BAP species such as mussel and file shell beds) from the installation of infrastructure ( i.e. support structure cables dragging during installation) and subsea cabling ( i.e. placement and dragging during installation and operation) has been identified at:

  • Atlantic and Mediterranean high energy infralittoral rock (including BAP habitat Tidal Swept Channels).
  • Atlantic and Mediterranean moderate energy infralittoral rock (including BAP habitat Tidal Swept Channels and S. spinulosa reefs).
  • Atlantic and Mediterranean high energy circalittoral rock (including BAP habitat Tidal Swept Channels).
  • Atlantic and Mediterranean moderate energy circalittoral rock.
  • Sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, horse mussel beds).
  • Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds).
  • Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds).
  • Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds).
  • Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds).

Benthic Habitats and Water Column:

Habitat Changes

The presence of these devices in the water column and their moorings to the seabed, has the potential to contribute to habitat changes in a number of ways. In general, impacts on seabed habitats from the devices and their supports may include changes in sediment dynamics (creation of a shadow and turbulence), deposition/siltation and vibration (if positioned directly on the seabed). Additional impacts such as changes in tidal flows and fluxes, and changes in turbulence due to installation and operation may also occur. The impacts on wave energy and potential for dissipation from sub-surface devices are unclear at present.

In general, these changes to sediment dynamics and coastal processes can create adverse impacts to benthic habitats and their species. This may include direct impacts such as the introduction of variations and shifts in grain size of sediments, which can alter habitat character and species distribution; shading or smothering of benthic areas with sediments and the presence of the device itself; changes in species distribution via interference with filter feeders, inhibiting their respiration and reproduction; and secondary impacts such as reducing food sources for other species supported by these habitats. These may collectively lead to wider changes in ecosystem composition. In some instances, this may also result in changes to the shoreline and coastline.

Sediment Dynamics

Changes in sediment dynamics due to the offshore presence and operation of these devices and their seabed-based support structures may occur during both the installation and operation phases. In offshore areas, there may be the potential for changes to sediment dynamics and wave shadow effects, leading to deposition/siltation and smothering. The potential for scouring associated with gravity based support structures/mooring systems may also exist.

No specific impacts from wave dissipation were identified.

While likely site specific, the potential for impacts in a range of BAP habitats has been identified:

  • Changes in sediment dynamics in high energy littoral rock (including BAP habitat Tidal Swept Channels) due to device and moorings (offshore). Impacts unlikely but may have potential impacts for F. distichus.
  • Changes in sediment dynamics in Moderate energy littoral (including BAP habitat Under boulder communities) due to device and moorings (offshore). Impacts unlikely but may have potential impacts on under-boulder communities ( BAP).
  • Changes in sediment dynamics in Littoral biogenic reefs (including BAP habitat blue mussel beds) due to device and moorings (offshore). Impacts unlikely and these species are common, but there may be the potential for impacts for blue mussel beds if present.
  • Changes in sediment dynamics in features of littoral sediment (including BAP habitat blue mussel beds) due to device and moorings (offshore). Impacts are unlikely as these species are common, but there may be the potential for impacts for blue mussel beds if present.
  • Changes in sediment dynamics in Sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, horse mussel beds) due to device and moorings (offshore). Impacts may affect sediment grain size, and affect the habitat and species in these areas ( i.e. E. timida).
  • Changes in sediment dynamics in Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds) due to device and moorings (offshore). Impacts may affect sediment grain size, and affect the habitat and species in these areas ( i.e. E. timida)
  • Changes in sediment dynamics in Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds) due to device and moorings (offshore). Impacts may affect sediment grain size, and affect the habitat and species in these areas ( i.e. E. timida).
  • Changes in sediment dynamics in Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds) due to device and moorings (offshore). While impacts are unlikely, there may be the potential for impacts for A. fragilis, C. cruoriaeformis, D. Montagnei, P. calcareum, L. corallioides, horse mussel beds or blue mussel beds or maerl beds present.
  • Changes in sediment dynamics in Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds) due to device and moorings (offshore). While impacts are unlikely, there may be the potential to affect horse mussel beds, cold coral reefs or blue mussel beds if present.
  • Changes in sediment dynamics in Atlantic and Mediterranean high energy circalittoral rock (including BAP habitat Tidal Swept Channels) due to device and moorings (offshore). Potential impacts for habitat and S. pallida as it is nationally scarce.
  • Changes in sediment dynamics in Atlantic and Mediterranean moderate energy circalittoral rock due to device and moorings (offshore). Potential impacts for S. spinulosa, A dohrnii and S. pallida.
  • Changes in sediment dynamics in circalittoral rock features due to device and moorings (offshore). Impacts are not considered likely, but included due to potential as this habitat is seldom recorded.

Changes in Tidal Flows and Fluxes

Decreases in tidal flows associated with these devices or support moorings may have adverse effects, particularly given the varying position of these devices in the water column. Any such impacts are expected to be site and habitat specific:

  • Changes in tidal flows and fluxes in Sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, horse mussel beds) due to device and moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if C. cruoriaeformis, D. Montagnei, E. timida, A. sarsi or horse mussel beds are present.
  • Changes in tidal flows and fluxes in Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds) due to device and moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if A. fragilis, E. timida, A. sarsi or blue mussel beds are present.
  • Changes in tidal flows and fluxes in Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds) due to device and moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if A. fragilis, E. timida, A. sarsi, horse mussel beds or file shell beds are present.
  • Changes in tidal flows and fluxes in Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds) due to device and moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if A. fragilis, C. cruoriaeformis, D. Montagnei, P. calcareum, L. corallioides, horse mussel beds or blue mussel beds or maerl beds present.
  • Changes in tidal flows and fluxes in Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds) due to device and moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur and increase competition between kelp species ( i.e. A. esculenta) associated with changing flow rates. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if horse mussel beds, cold coral reefs or blue mussel beds if present.

Scouring and Deposition

While likely site specific, this may present a potential risk to BAP species such as mussel beds, M. edulis, and filter feeders, with secondary impacts up the food chain ( i.e. affecting predatory species that feed on them). The potential for scouring in a range of BAP habitats has been identified for offshore devices:

  • Potential deposition of sediment from device and moorings in littoral biogenic reefs (including BAP habitat blue mussel beds) if blue mussel beds are present. While deposition unlikely in high-energy environments, raised as potential issue due to presence of BAP habitats.
  • Potential for deposition of sediment in features of littoral sediment (including BAP habitat blue mussel beds) if blue mussel beds are present. May impact on habitat character.
  • Deposition of sediment ( i.e. smothering, inhibiting respiration, feeding and growth) in sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, blue mussel beds) if A. fragilis, C. cruoriaeformis, D. Montagnei, E. timida or horse mussel beds are present.
  • Potential for increased scouring and deposition of sediment ( i.e. smothering, inhibiting respiration, feeding and growth) in Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds) if A. fragilis, E. timida, A sarsi or blue mussel beds are present.
  • Potential for increased scouring and deposition of sediment ( i.e. smothering, inhibiting respiration, feeding and growth) in Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds). Considered unlikely but has potential for impacts if A. fragilis, D. Montagnei, E. timida, A sarsi, horse mussel beds or file shell beds are present.
  • Potential for increased scouring and deposition of sediment ( i.e. smothering, inhibiting respiration, feeding and growth) in Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds). Considered unlikely, but noted as a potential impact particularly if C. cruoriaeformis, D. Montagnei, P. calcareum, L. corallioides, horse mussel beds, blue mussel beds or maerl beds are present.
  • Potential for increased scouring and potential deposition of sediments in Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds) if horse mussel beds, cold water coral reefs or blue mussel beds are present.
  • Potential for deposition of sediment on filter feeders in circalittoral rock features. Included due to potential; for impacts ( i.e. smothering) although this is considered unlikely for arrays up to 10 MW).
  • Potential for deposition of sediment in high energy littoral rock (including BAP habitat Tidal Swept Channels) if F. Distichus is present.

Loss of Habitat/Abrasion

The placement of offshore or near-shore devices, and/or their moorings on the seabed can result in damage to benthic habitats, or their loss in extreme instances ( e.g. seabed structures, piling, drilling and anchoring, subsea cable placement). This could also include additional damage such as the abrasion of benthic areas by support structures and associated cabling in the placement process.

The potential for abrasion of marine habitats and sessile/sedentary species ( i.e. BAP species such as mussel and file shell beds) from the installation of infrastructure ( i.e. mooring cables dragging during installation) and subsea cabling ( i.e. placement and dragging during installation and operation) has been identified at:

  • Atlantic and Mediterranean high energy circalittoral rock (including BAP habitat Tidal Swept Channels).
  • Atlantic and Mediterranean moderate energy circalittoral rock.
  • Sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, horse mussel beds).
  • Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds).
  • Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds).
  • Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds).
  • Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds).

Benthic Habitats and Water Column:

Habitat Changes

The presence of these devices and their moorings has the potential to contribute to habitat changes in a number of ways. In summary, changes to sediment dynamics (shoreline), vibration (shoreline), wave energy dissipation (offshore) and changes to coastal processes (shoreline) can create adverse impacts to benthic and shoreline habitats and species. This may have direct impacts in altered sediment movement and changes in coastal character and profile which have the potential for a range of adverse impacts to these habitats ( i.e. smothering, coastal profile, etc.). Secondary impacts may include changes to species distribution, and potentially reducing food sources for other species supported by these habitats.

Loss of habitat due to the placement of shoreline devices is likely. In such instances sessile or sedentary species would be affected. Even small amounts of lost habitat may diminish species populations, particularly rare or vulnerable populations. However, the nature and extent of impacts would be site-specific.

Sediment Dynamics and Wave Dissipation

Changes in sediment dynamics due to the presence and operation of these devices at the shoreline or offshore, and from their moorings (gravity anchors and moorings) may occur during both the installation and operation phases. In offshore areas, there may be the potential for changes to coastal processes via the dissipation of wave energy and creation of wave shadow effects. Shoreline devices have the potential for changes in the coastal profile, largely due to the potential for changes in flows/turbulence, and impacts such as erosion, deposition/siltation and smothering. of habitats.

While likely site specific, the potential for impacts in a range of BAP habitats has been identified:

  • Changes in sediment dynamics in high energy littoral rock (including BAP habitat Tidal Swept Channels) due to device (onshore) and moorings (offshore). Impacts unlikely but may have potential impacts for F. distichus. Wave dissipation effects may adversely impact filter feeders ( i.e. M. edulis, S. allantoides) due to food dissipation and smothering, and create suitable conditions for other fucoid species to outcompete F. distichus.
  • Changes in sediment dynamics in Moderate energy littoral (including BAP habitat Under boulder communities) due to device (onshore) and moorings (offshore). Impacts unlikely but may have potential impacts on under-boulder communities ( BAP).
  • Changes in sediment dynamics in Littoral biogenic reefs (including BAP habitat blue mussel beds) due to device (onshore) and moorings (offshore). Decreases in wave action may adversely impact filter feeders ( i.e. M. edulis) and reduced availability of sediment available for others ( i.e. S. alveolata). Impacts unlikely and these species are common, but there may be the potential for impacts for blue mussel beds if present.
  • Changes in sediment dynamics in Features of littoral sediment (including BAP habitat blue mussel beds) due to device (onshore) and moorings (offshore). Decreases in wave action may adversely impact filter feeders ( i.e. M. edulis). Impacts unlikely and these species are common, but there may be the potential for impacts for blue mussel beds if present.
  • Changes in sediment dynamics in Sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, horse mussel beds) due to device (onshore) and moorings (offshore). Impacts may affect sediment grain size, and affect the habitat and species in these areas ( i.e. E. timida). Decreases in wave action may adversely impact filter feeders ( i.e. A. fragilis). Impacts are unlikely and these species are common, but there may be the potential for impacts for A. fragilis, C. cruoriaeformis, D. Montagnei, E. timida or horse mussel beds if present.
  • Changes in sediment dynamics in Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds) due to device (onshore) and moorings (offshore). Impacts may affect sediment grain size, and affect the habitat and species in these areas ( i.e. E. timida) and decreases in wave action may adversely impact filter feeders ( i.e. A. fragilis) through reduced food supplies and siltation. While impacts are unlikely, there may be the potential for impacts for A. fragilis, E. timida or A. sarsi or blue mussel beds if present.
  • Changes in sediment dynamics in Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds) due to device (onshore) and moorings (offshore). Impacts may affect sediment grain size, and affect the habitat and species in these areas ( i.e. E. timida) and decreases in wave action or tidal flows may adversely impact filter feeders ( i.e. A. fragilis) through reduced food supplies and siltation. While impacts are considered unlikely, there may be the potential for impacts for A. fragilis, D. Montagnei, E. timida or A. sarsi, horse mussel beds or file shell beds if present.
  • Changes in sediment dynamics in Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds) due to device (onshore) and moorings (offshore). Wave dissipation may also affect species competition ( i.e. seaweeds and filter feeders with reductions in exposure and food supplies) and changes in sediment dynamics. While impacts are unlikely, there may be the potential for impacts for A. fragilis, C. cruoriaeformis, D. Montagnei, P. calcareum, L. corallioides, horse mussel beds or blue mussel beds or maerl beds present.
  • Changes in sediment dynamics in Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds) due to device (onshore) and moorings (offshore). Wave dissipation also has the potential to impact of filter feeders ( i.e. reduced food supplies, siltation, migration of some species to shallow water depths) thus potentially affecting the overall habitat. While impacts are unlikely, there may be the potential to affect horse mussel beds, cold coral reefs or blue mussel beds if present.
  • Changes in sediment dynamics in Atlantic and Mediterranean high energy infralittoral rock (including BAP habitat Tidal Swept Channels) due to device (shoreline). Potential impacts for S. pallida as it is nationally scarce.
  • Changes in sediment dynamics in Atlantic and Mediterranean moderate energy infralittoral rock (including BAP habitat Tidal Swept Channels and S. spinulosa reefs) due to device (shoreline). Impacts unlikely for small arrays (10 MW) but potential impacts may exist for S. pallida and S. spinulosa.
  • Changes in sediment dynamics in Atlantic and Mediterranean high energy circalittoral rock (including BAP habitat Tidal Swept Channels) due to device (onshore) or moorings (offshore). Potential impacts for habitat and S. pallida as it is nationally scarce.
  • Changes in sediment dynamics in Atlantic and Mediterranean moderate energy circalittoral rock due to device (onshore) and moorings (offshore). Potential impacts for S. spinulosa, A dohrnii and S. pallida.
  • Changes in sediment dynamics in circalittoral rock features due to device (onshore) and moorings (offshore). Impacts are not considered likely, but included due to potential as this habitat is seldom recorded.

Change in Tidal Flows and Fluxes

Decreases in tidal flows and fluxes due to the presence of offshore and shoreline devices may have adverse effects on nearby the benthic habitats, although these are expected to be largely site-specific:

  • Changes in tidal flows and fluxes in Sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, horse mussel beds) due to moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if C. cruoriaeformis, D. Montagnei, E. timida, A. sarsi or horse mussel beds are present.
  • Changes in tidal flows and fluxes in Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds) due to moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if A. fragilis, E. timida, A. sarsi or blue mussel beds are present.
  • Changes in tidal flows and fluxes in Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds) due to moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if A. fragilis, E. timida, A. sarsi, horse mussel beds or file shell beds are present.
  • Changes in tidal flows and fluxes in Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds) due to moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if A. fragilis, C. cruoriaeformis, D. Montagnei, P. calcareum, L. corallioides, horse mussel beds or blue mussel beds or maerl beds present.
  • Changes in tidal flows and fluxes in Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds) due to moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur and increase competition between kelp species ( i.e. A. esculenta) associated with changing flow rates. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if horse mussel beds, cold coral reefs or blue mussel beds if present.

Scouring and Deposition

While likely site specific, this may present a potential risk to BAP species such as mussel beds, M. edulis, and filter feeders, with secondary impacts up the food chain ( i.e. affecting predatory species that feed on them). The potential for scouring due to the presence of offshore mooring systems in a range of BAP habitats has been identified:

  • Potential deposition of sediment associated with moorings in littoral biogenic reefs (including BAP habitat blue mussel beds) if blue mussel beds are present. While deposition unlikely in high-energy environments, raised as potential issue due to presence of BAP habitats.
  • Potential for deposition of sediment associated with moorings in features of littoral sediment (including BAP habitat blue mussel beds) if blue mussel beds are present. May impact on habitat character.
  • Increased scour, and deposition of sediment from moorings ( i.e. smothering, inhibiting respiration, feeding and growth) in sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, blue mussel beds) if A. fragilis, C. cruoriaeformis, D. Montagnei, E. timida or horse mussel beds are present.
  • Increased scouring and deposition of sediment from moorings ( i.e. smothering, inhibiting respiration, feeding and growth) in Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds) if A. fragilis, E. timida, A sarsi or blue mussel beds are present.
  • Increased scouring, and deposition of sediment from moorings ( i.e. smothering, inhibiting respiration, feeding and growth) in Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds). Considered unlikely but has potential for impacts if A. fragilis, D. Montagnei, E. timida, A sarsi, horse mussel beds or file shell beds are present.
  • Increased scouring, and deposition of sediment from moorings ( i.e. smothering, inhibiting respiration, feeding and growth) in Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds). Considered unlikely, but noted as a potential impact particularly if C. cruoriaeformis, D. Montagnei, P. calcareum, L. corallioides, horse mussel beds, blue mussel beds or maerl beds are present
  • Scouring and potential deposition of sediments from moorings in Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds) if horse mussel beds, cold water coral reefs or blue mussel beds are present.
  • Potential for deposition of sediment associated with moorings on filter feeders in circalittoral rock features. Included due to potential; for impacts ( i.e. smothering) although this is considered unlikely for arrays up to 10 MW).

Loss of Habitat/Abrasion

The placement of shoreline devices, and seabed moorings for offshore devices, can result in damage to benthic habitats, and in some instances lead to the loss of habitat ( e.g. the placement of shoreline devices, seabed structures including gravity base structures, piling, drilling and anchoring, subsea cable placement). In such instances sessile or sedentary species would be affected, and even small amounts of lost habitat may diminish species populations, particularly rare or vulnerable populations. However, the extent of impacts would likely be site-specific.

The potential for abrasion of marine habitats and sessile/sedentary species ( i.e. BAP species such as mussel and file shell beds) from the installation of infrastructure ( i.e. mooring cables dragging during installation) and subsea cabling ( i.e. placement and dragging during installation and operation) has been identified at:

  • Atlantic and Mediterranean high energy circalittoral rock (including BAP habitat Tidal Swept Channels).
  • Atlantic and Mediterranean moderate energy circalittoral rock.
  • Sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, horse mussel beds).
  • Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds).
  • Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds).
  • Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds).
  • Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds).

Benthic Habitats and Water Column:

Habitat Changes

The presence of these devices and their moorings has the potential to contribute to habitat changes in a number of ways. In summary, changes to sediment dynamics (shoreline), vibration (shoreline), wave energy dissipation (offshore) and changes to coastal processes (shoreline) can create adverse impacts to benthic and shoreline habitats and species. These may have direct impacts in scouring ( i.e. sediment accumulated in shoreline devices may be entrained in the outflow) and deposition/siltation from support structures which have the potential for a range of adverse impacts to these habitats ( i.e. introduction of variations and shifts in grain size of sediments, shading or smothering of benthic areas, changes to ecosystem composition and coastline profiles, etc.). Secondary impacts may include changes to species distribution, interference with filter feeders, inhibiting respiration and reproduction, and reducing food sources for other species supported by these habitats.

Loss of habitat due to the placement of shoreline devices is likely. In such instances sessile or sedentary species would be affected, and even small amounts of lost habitat may diminish species populations, particularly rare or vulnerable populations. However, the extent of impacts would likely be site-specific.

Sediment Dynamics and Wave Dissipation

Changes in sediment dynamics due to the presence and operation of these devices at the shoreline or near-shore, and from their moorings (gravity anchors and moorings) may occur during both the installation and operation phases. In offshore areas, there may be the potential for changes to coastal processes via the dissipation of wave energy and creation of wave shadow effects, particularly for large offshore devices. Shoreline devices have the potential for changes in the coastal profile, largely due to the potential for changes in flows/turbulence ( i.e. alteration of backflows released from the device chamber), and impacts such as localised scouring and water turbidity.

While likely site specific, the potential for impacts in a range of BAP habitats has been identified:

  • Changes in sediment dynamics in high energy littoral rock (including BAP habitat Tidal Swept Channels) due to device (onshore) and moorings (offshore). Impacts unlikely but may have potential impacts for F. distichus. Wave dissipation effects may adversely impact filter feeders ( i.e. M. edulis, S. allantoides) due to food dissipation and smothering, and create suitable conditions for other fucoid species to outcompete F. distichus.
  • Changes in sediment dynamics in Moderate energy littoral rock (including BAP habitat Under boulder communities) due to device (onshore) and moorings (offshore). Impacts unlikely but may have potential impacts on under-boulder communities ( BAP).
  • Changes in sediment dynamics in Littoral biogenic reefs (including BAP habitat blue mussel beds) due to device (onshore) and moorings (offshore). Decreases in wave action may adversely impact filter feeders ( i.e. M. edulis) and reduced availability of sediment available for others ( i.e. S. alveolata). Impacts unlikely and these species are common, but there may be the potential for impacts for blue mussel beds if present.
  • Changes in sediment dynamics in Features of littoral sediment (including BAP habitat blue mussel beds) due to device (onshore) and moorings (offshore). Decreases in wave action may adversely impact filter feeders ( i.e. M. edulis). Impacts unlikely and these species are common, but there may be the potential for impacts for blue mussel beds if present.
  • Changes in sediment dynamics in Sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, horse mussel beds) due to device (onshore) and moorings (offshore). Impacts may affect sediment grain size, and affect the habitat and species in these areas ( i.e. E. timida). Decreases in wave action may adversely impact filter feeders ( i.e. A. fragilis). Impacts are unlikely and these species are common, but there may be the potential for impacts for A. fragilis, C. cruoriaeformis, D. Montagnei, E. timida or horse mussel beds if present.
  • Changes in sediment dynamics in Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds) due to device (onshore) and moorings (offshore). Impacts may affect sediment grain size, and affect the habitat and species in these areas ( i.e. E. timida) and decreases in wave action may adversely impact filter feeders ( i.e. A. fragilis) through reduced food supplies and siltation. While impacts are unlikely, there may be the potential for impacts for A. fragilis, E. timida or A. sarsi or blue mussel beds if present.
  • Changes in sediment dynamics in Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds) due to device (onshore) and moorings (offshore). Impacts may affect sediment grain size, and affect the habitat and species in these areas ( i.e. E. timida) and decreases in wave action or tidal flows may adversely impact filter feeders ( i.e. A. fragilis) through reduced food supplies and siltation. While impacts are considered unlikely, there may be the potential for impacts for A. fragilis, D. Montagnei, E. timida, A. sarsi, horse mussel beds or file shell beds if present.
  • Changes in sediment dynamics in Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds) due to device (onshore) and moorings (offshore). Wave dissipation may also affect species competition ( i.e. seaweeds and filter feeders with reductions in exposure and food supplies) and changes in sediment dynamics. While impacts are unlikely, there may be the potential for impacts for A. fragilis, C. cruoriaeformis, D. Montagnei, P. calcareum, L. corallioides, horse mussel beds or blue mussel beds or maerl beds present.
  • Changes in sediment dynamics in Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds) due to device (onshore) and moorings (offshore). Wave dissipation also has the potential to impact of filter feeders ( i.e. reduced food supplies, siltation, migration of some species to shallow water depths) thus potentially affecting the overall habitat. While impacts are unlikely, there may be the potential to affect horse mussel beds, cold coral reefs or blue mussel beds if present.
  • Changes in sediment dynamics in Atlantic and Mediterranean high energy infralittoral rock (including BAP habitat Tidal Swept Channels) due to device (shoreline). Potential impacts for S. pallida as it is nationally scarce.
  • Changes in sediment dynamics in Atlantic and Mediterranean moderate energy infralittoral rock (including BAP habitat Tidal Swept Channels and S. spinulosa reefs) due to device (shoreline). Impacts unlikely for small arrays (10 MW) but potential impacts may exist for S. pallida and S. spinulosa.
  • Changes in sediment dynamics in Atlantic and Mediterranean high energy circalittoral rock (including BAP habitat Tidal Swept Channels) due to device (onshore) or moorings (offshore). Potential impacts for habitat and S. pallida as it is nationally scarce.
  • Changes in sediment dynamics in Atlantic and Mediterranean moderate energy circalittoral rock due to device (onshore) and moorings (offshore). Potential impacts for S. spinulosa, A dohrnii and S. pallida.
  • Changes in sediment dynamics in circalittoral rock features due to device (onshore) and moorings (offshore). Impacts are not considered likely, but included due to potential as this habitat is seldom recorded.

Change in Tidal Flows and Fluxes

Decreases in tidal flows from the installation and placement of support structures and moorings (for offshore devices) may potentially have adverse effects, although these are expected to be site and habitat specific:

  • Changes in tidal flows and fluxes in Sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, horse mussel beds) due to moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if C. cruoriaeformis, D. Montagnei, E. timida, A. sarsi or horse mussel beds are present.
  • Changes in tidal flows and fluxes in Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds) due to moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if A. fragilis, E. timida, A. sarsi or blue mussel beds are present.
  • Changes in tidal flows and fluxes in Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds) due to moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if A. fragilis, E. timida, A. sarsi, horse mussel beds or file shell beds are present.
  • Changes in tidal flows and fluxes in Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds) due to moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if A. fragilis, C. cruoriaeformis, D. Montagnei, P. calcareum, L. corallioides, horse mussel beds or blue mussel beds or maerl beds present.
  • Changes in tidal flows and fluxes in Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds) due to moorings (offshore). on filter feeders ( i.e. M. modiolus, A. digitatum and A. fragilis) from reduced food supplies and siltation. Strong flows may detach weakly attached organisms. Changes in the overall habitat, through changing grain size in sediments may also occur and increase competition between kelp species ( i.e. A. esculenta) associated with changing flow rates. While many species are present in a variety of tidal flow conditions, impacts are unlikely. However, the potential may exist for impacts if horse mussel beds, cold coral reefs or blue mussel beds if present.

Scouring and Deposition

While likely site specific, this may present a potential risk to BAP species such as mussel beds, M. edulis, and filter feeders, with secondary impacts up the food chain ( i.e. affecting predatory species that feed on them). The potential for scouring due to the presence of offshore mooring systems in a range of BAP habitats has been identified:

  • Increased scour at high tide in high energy littoral rock (including BAP habitat Tidal Swept Channels) if F. Distichus is present.
  • Increased scour at high tide in moderate energy littoral (including BAP habitat Under boulder communities) if under-boulder communities ( BAP) are present.
  • Increased scour at high tide and deposition of sediment in littoral biogenic reefs (including BAP habitat blue mussel beds) if blue mussel beds are present.
  • Increased scour and deposition of sediment at high tide in features of littoral sediment (including BAP habitat blue mussel beds) if blue mussel beds are present ( i.e. by filling in interstices between mussels forming beds).
  • Increased scour and deposition of sediment ( i.e. smothering, inhibiting respiration, feeding and growth) in sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, blue mussel beds) if A. fragilis, C. cruoriaeformis, D. Montagnei, E. timida or horse mussel beds are present.
  • Increased scouring and deposition of sediment ( i.e. smothering, inhibiting respiration, feeding and growth) in Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds) if A. fragilis, E. timida, A sarsi or blue mussel beds are present.
  • Increased scouring and deposition of sediment ( i.e. smothering, inhibiting respiration, feeding and growth) in Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds). Considered unlikely but has potential for impacts if A. fragilis, D. Montagnei, E. timida, A sarsi, horse mussel beds or file shell beds are present.
  • Increased scouring and deposition of sediment ( i.e. smothering, inhibiting respiration, feeding and growth) in Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds). Considered unlikely, but noted as a potential impact particularly if C. cruoriaeformis, D. Montagnei, P. calcareum, L. corallioides, horse mussel beds, blue mussel beds or maerl beds are present
  • Potential for increased scouring in Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds) if horse mussel beds, cold water coral reefs or blue mussel beds are present.
  • Potential for deposition of sediment on filter feeders in circalittoral rock features. Included due to potential; for impacts ( i.e. smothering) although this is considered unlikely for arrays up to 10 MW).

Loss of Habitat/Abrasion

The placement of offshore, near-shore or shoreline devices, and/or their moorings on the seabed, can result in damage to benthic habitats, or in some instances lead to the loss of habitat ( e.g. the placement of shoreline devices, seabed structures including gravity base structures, piling, drilling and anchoring, subsea cable placement). In such instances sessile or sedentary species would be affected, and even small amounts of lost habitat may diminish or displace species populations, particularly those that are rare or vulnerable. The extent of impacts would likely be site-specific.

The potential for abrasion of marine habitats and sessile/sedentary species ( i.e. BAP species such as mussel and file shell beds) from the installation of infrastructure ( i.e. mooring cables dragging during installation) and subsea cabling ( i.e. placement and dragging during installation and operation) has been identified at:

  • Atlantic and Mediterranean high energy circalittoral rock (including BAP habitat Tidal Swept Channels).
  • Atlantic and Mediterranean moderate energy circalittoral rock.
  • Sublittoral coarse sediment (including BAP habitats subtidal sands and gravel, horse mussel beds).
  • Sublittoral sand (including BAP habitat sub-tidal sands and gravel, blue mussel beds).
  • Sublittoral mixed sediments (including BAP habitat Horse mussel beds, file shell beds).
  • Sublittoral macrophyte-dominated sediment (including BAP habitats maerl beds, tidal swept channels, horse mussel beds, blue mussel beds).
  • Sublittoral biogenic reefs (including BAP habitats horse mussel beds, cold-water coral reefs and blue mussel beds).

Population and human health [11]

Summary of key potential effects on population and human health:

  • Displaced/increased shipping density.
  • Reductions in the safety of navigation.
  • Risk of collision of recreational or commercial shipping with installation vessels and operational devices, particularly for devices and vessels that are low in the water and in high waves.
  • Access restrictions - the presence of devices in the water may restrict or reduce access to key recreational sailing areas or other water sports.

Key measures to prevent adverse effects may include: siting devices away from spatially constrained areas and areas with high vessel densities; siting devices in open water; making use of industry guidance on assessment of effects and use of aids to navigation; use of notifications such as 'Notices to Mariners', publicising information at marina, and Sailing Directions; and adhering to appropriate safety regulations. Consideration of device types that are fully submerged and allow shipping to pass over the top of them could reduce effects, but guidance would need to be sought on a case-by-case basis on the level of clearance required.

The potential for vessel collisions with above water components, or components at shallow depths in the water column, has been identified and may have the potential for serious injury.

However, navigational warnings ( i.e. marker buoys, navigational aids, lighting) are likely to be required on such devices for navigational purposes.

The potential for vessel collisions with above water components has been identified, and may have the potential for serious injury.

However, navigational warnings ( i.e. marker buoys, navigational aids, lighting) are likely to be required on such devices for navigational purposes.

The potential for vessel collisions with device components at shallow depths in the water column has been identified and may have the potential for serious injury.

However, navigational warnings ( i.e. marker buoys, navigational aids, lighting) are likely to be required on such devices for navigational purposes.

The potential for vessel collisions with device components at shallow depths in the water column has been identified and may have the potential for serious injury.

However, navigational warnings ( i.e. marker buoys, navigational aids, lighting) are likely to be required on such devices for navigational purposes.

While above water components are likely to be clearly visible, the potential for vessel collisions with above water components or components at shallow depths in the water column, has been identified and has the potential for serious injury, particularly in periods of low light.

However, lighting is likely to be required for navigational purposes on such devices.

While above water components are likely to be clearly visible, the potential for vessel collisions with above water components or components at shallow depths in the water column, has been identified and has the potential for serious injury, particularly in periods of low light.

However, lighting is likely to be required for navigational purposes on such devices.

Water and marine environment [12]

Summary of key potential effects on water quality include:

  • Disturbance of contaminated sediments during device installation, e.g. disposal sites (silt, sand, rock and gravel sites, fish wastes and sludge); munitions dumps, and weapons ranges.

Potential for impacts from local changes in wave energy dissipation and deposition due to the presence of these devices in the water column, and for changes to sediment dynamics, scouring, deposition, tidal flows and fluxes and water turbulence associated with the presence of mooring cables and structures on the seabed.

Potential for installation impacts such as water turbidity and contamination risks associated with installation and operation ( e.g. leakage from vessels or equipment).

Potential for impacts from local changes in wave energy dissipation due to the presence of these devices at the top of the water column, and for changes to sediment dynamics, scouring, deposition, tidal flows and fluxes and water turbulence associated with the presence of mooring cables and structures on the seabed.

Potential for installation impacts such as water turbidity and contamination risks associated with installation and operation ( e.g. leakage from vessels or equipment).

Potential for impacts from local changes in wave energy dissipation, changes to sediment dynamics, scouring, deposition, tidal flows and fluxes, water turbidity and water turbulence associated with the presence of these devices and their support structures mounted on the seabed.

Potential for installation impacts such as water turbidity and contamination risks associated with installation and operation ( e.g. leakage from vessels or equipment).

Potential for impacts from local changes in water turbulence due to the presence of these devices and their moorings. The potential may also exist for changes to sediment dynamics, scouring (associated with gravity based structures, if used), vibration, deposition, tidal flows and fluxes, water turbidity and water turbulence associated with the presence of these devices in the water column and their support structures mounted on the seabed.

Potential for installation impacts such as water turbidity and contamination risks associated with installation and operation ( e.g. leakage from vessels or equipment).

Potential for impacts from local changes in water turbulence due to the presence of offshore devices and their moorings. The potential may also exist for changes to sediment dynamics (shoreline), scouring (offshore associated with moorings, i.e. gravity based structures, etc.), vibration, dissipation of wave energy (offshore), water turbidity and water turbulence (both shoreline) associated with the presence of these devices and their support structures.

The potential for installation impacts such as water turbidity and contamination risks associated with installation and operation ( e.g. leakage from vessels or equipment) was also identified.

Potential for impacts from local changes in water turbulence due to the presence of offshore devices and their moorings. The potential may also exist for changes to sediment dynamics (shoreline), scouring (shoreline associated with outflows, and offshore associated with moorings, i.e. gravity based structures, etc.), dissipation of wave energy (offshore), changes in coastal processes and profile (both shoreline and offshore), water turbidity and water turbulence (both shoreline) associated with the presence of these devices and their support structures.

The potential for installation impacts such as water turbidity and contamination risks associated with installation and operation ( e.g. leakage from vessels or equipment) was also identified.

Climatic factors [13]

Potential for wave energy dissipation and, in some instances, may contribute to the protection of coastlines susceptible to erosion ( i.e. Firth of Clyde).

Likely contribution to renewable energy generation and reduction in GHG emissions ( i.e. displacement of energy generated from non-renewable sources).

Potential for wave energy dissipation and, in some instances, may contribute to the protection of coastlines susceptible to erosion ( i.e. Firth of Clyde).

Likely contribution to renewable energy generation and reduction in GHG emissions ( i.e. displacement of energy generated from non-renewable sources).

Potential for wave energy dissipation and, in some instances, may contribute to the protection of coastlines susceptible to erosion ( i.e. Firth of Clyde).

Likely contribution to renewable energy generation and reduction in GHG emissions ( i.e. displacement of energy generated from non-renewable sources).

Likely contribution to renewable energy generation and reduction in GHG emissions ( i.e. displacement of energy generated from non-renewable sources).

Potential for wave energy dissipation (offshore) and changes to coastal profile and character. The placement of shoreline devices may contribute to the protection of coastlines susceptible to erosion ( i.e. Firth of Clyde).

Likely contribution to renewable energy generation and reduction in GHG emissions ( i.e. displacement of energy generated from non-renewable sources).

Potential for wave energy dissipation (offshore), changes to coastal processes and character/profile. The placement of these devices, in some instances, may contribute to the protection of coastlines susceptible to erosion ( i.e. Firth of Clyde).

Likely contribution to renewable energy generation and reduction in GHG emissions ( i.e. displacement of energy generated from non-renewable sources).

Marine geology and coastal processes [14]

Summary of key potential effects on geology:

  • Disturbance or damage to coastal Geological SSSIs and Geological Conservation Review sites ( GCRs)
  • Changes in coastal processes due to energy extraction, seabed contamination and water quality (including disposal areas)

Potential for impacts from local changes in wave energy dissipation and deposition due to the presence of these devices in the water column, and for changes to sediment dynamics, scouring, deposition, tidal flows and fluxes, water turbulence and direct abrasion on the seabed associated with the presence of moorings cables and structures.

Potential for impacts from local changes in wave energy ( i.e. dissipation) due to the presence of these devices, and for changes to sediment dynamics, scouring, deposition, water turbulence and direct abrasion on the seabed associated with the presence of moorings cables and structures.

Potential for impacts from local changes in wave energy ( i.e. dissipation), changes to sediment dynamics, scouring, vibration, deposition, tidal flows and fluxes, water turbidity and water turbulence associated with the presence of these devices and their support structures mounted on the seabed.

Potential for impacts from local changes in water turbulence due to the presence of these devices and their moorings. The potential may also exist for changes to sediment dynamics, scouring (associated with gravity based structures, if used), vibration, deposition, tidal flows and fluxes, water turbidity and water turbulence associated with the presence of these devices in the water column and their support structures mounted on the seabed.

Potential local changes in water turbulence due to the presence of group of these devices, and the presence of support structures (likely gravity-based) in offshore and near-shore areas. The potential may also exist for increased scouring and from changes to coastal processes and profiles (shoreline devices), and for seabed or coastal habitat disturbance/loss during installation, and abrasion of marine geology in installation of mooring systems and subsea cabling.

Potential local changes in water turbulence due to the presence of these devices at the shoreline, and in presence of support structures (likely gravity-based) in offshore and near-shore areas. The potential may also exist for scouring and changes to coastal processes ( i.e. sediment dynamics, wave dissipation and tidal fluxes) during operation, and for seabed disturbance during installation ( i.e. loss of habitat) and abrasion of marine geology in installation of mooring systems and subsea cabling.

Historic Environment [15]

Summary of key potential effects on marine and coastal historic environment include:

  • Direct disturbance, damage, or destruction of submarine archaeological remains and wrecks during device installation and cable trenching ,
  • Direct disturbance, damage or destruction of coastal archaeological remains during cable trenching (effects of grid connections are considered separately below)
  • Disturbance, damage or loss of archaeological remains and sites during installation of cables and overhead lines and substation construction from onshore grid connections

Key measures to prevent adverse effects may include: avoid sites of interest and exclusion zones for protected sites; follow Crown Estates 2007 JNAPC Code of Practice for seabed developers; carry out seabed surveys and walkover surveys prior to installation; carry out detailed routeing studies at project level in accordance with 'Holford Rules' best practice guidance on routeing overhead transmission lines.

There is the potential for placement of device moorings ( i.e. gravity-base, anchors, etc.) on known and designated historic sites, and on unknown sites ( i.e. wrecks). The potential may also exist for adverse effects on historic sites located nearby or downstream during operation ( i.e. scouring, deposition/siltation or abrasion from moorings; deposition/siltation from the presence of devices).

Adverse effects are likely to be avoided through careful siting of individual device moorings, although this may be more difficult for larger gravity bases or arrays of bases.

Pre-construction impacts can result from intrusive site investigation.

Construction effects as a result device installation, in particular from moorings, chains and cables. In particular as a result of piling and preparation of the seabed disturbing historic features.

Secondary effects from construction might arise from vessels anchoring and from temporary visual impacts on the setting of historic features

Associated cables and grid could directly impact on archaeological features on the seabed.

Operational effects are more limited Mooring requires lengthy chains and cables that rest on the sea bed and these can cause damage to heritage assets.

Changes to sediment processes and associated coastal erosion might cause impacts on some resources but may also help to reduce energy reaching shore and some erosion related heritage impacts.

Visual impacts for the setting of historic features during operation, construction and decommissioning.

There is the potential for placement of device moorings or structures ( i.e. gravity-base, anchors, etc.) on known and designated historic sites, and on unknown sites ( i.e. wrecks). The potential may also exist for adverse effects on historic sites located nearby or downstream during operation ( i.e. scouring, deposition/siltation or abrasion from moorings).

Adverse effects are likely to be avoided through careful siting of individual device moorings, although this may be more difficult for larger gravity bases or arrays of bases.

Pre-construction impacts can result from intrusive site investigation.

Construction effects as a result device installation, in particular from moorings, chains and cables. In particular as a result of piling and preparation of the seabed disturbing historic features.

Secondary effects from construction might arise from vessels anchoring and from temporary visual impacts on the setting of historic features

Associated cables and grid could directly impact on archaeological features on the seabed.

Operational effects are more limited Mooring requires lengthy chains and cables that rest on the sea bed and these can cause damage to heritage assets.

Changes to sediment processes and associated coastal erosion might cause impacts on some resources but may also help to reduce energy reaching shore and some erosion related heritage impacts.

Visual impacts for the setting of historic features during operation, construction and decommissioning.

There is the potential for placement of device support structures on known and designated historic sites, and on unknown sites ( i.e. wrecks). The potential may also exist for adverse effects on historic sites located nearby or downstream during operation ( i.e. scouring, deposition/siltation or abrasion from support structures).

Adverse effects are likely to be avoided through careful siting of individual device support structures, although this may be more difficult for larger seabed-mounted structures or groups of structures.

Pre-construction impacts can result from intrusive site investigation.

Construction effects as a result device installation, in particular from moorings, chains and cables. In particular as a result of piling and preparation of the seabed disturbing historic features.

Secondary effects from construction might arise from vessels anchoring and from temporary visual impacts on the setting of historic features

Associated cables and grid could directly impact on archaeological features on the seabed.

Operational effects are more limited Mooring requires lengthy chains and cables that rest on the sea bed and these can cause damage to heritage assets.

Changes to sediment processes and associated coastal erosion might cause impacts on some resources but may also help to reduce energy reaching shore and some erosion related heritage impacts.

Visual impacts for the setting of historic features during operation, construction and decommissioning.

There is the potential for placement of device support structures on known and designated historic sites, and on unknown sites ( i.e. wrecks). The potential may also exist for adverse effects on historic sites located nearby or downstream during operation ( i.e. scouring, deposition/siltation or abrasion from support structures).

Adverse effects are likely to be avoided through careful siting of individual device support structures, although this may be more difficult for larger seabed-mounted structures or groups of structures.

Pre-construction impacts can result from intrusive site investigation.

Construction effects as a result device installation, in particular from moorings, chains and cables. In particular as a result of piling and preparation of the seabed disturbing historic features.

Secondary effects from construction might arise from vessels anchoring and from temporary visual impacts on the setting of historic features

Associated cables and grid could directly impact on archaeological features on the seabed.

Operational effects are more limited Mooring requires lengthy chains and cables that rest on the sea bed and these can cause damage to heritage assets.

Changes to sediment processes and associated coastal erosion might cause impacts on some resources but may also help to reduce energy reaching shore and some erosion related heritage impacts.

Visual impacts for the setting of historic features during operation, construction and decommissioning.

There is the potential for placement of moorings ( i.e. gravity-base, anchors, etc.) on known and designated historic sites, and on unknown sites ( i.e. wrecks). The potential may also exist for adverse effects on historic sites located nearby or downstream during operation ( i.e. scouring, deposition/siltation or abrasion from offshore support structures; scouring, changes in sediment dynamics and changes in the coastal profile/character from shoreline devices).

Adverse effects are likely to be avoided through careful siting of individual device supports and moorings, although this may be more difficult for larger gravity bases or arrays of bases.

Pre-construction impacts can result from intrusive site investigation.

Construction effects as a result device installation, in particular from moorings, chains and cables. In particular as a result of piling and preparation of the seabed disturbing historic features.

Secondary effects from construction might arise from vessels anchoring and from temporary visual impacts on the setting of historic features

Associated cables and grid could directly impact on archaeological features on the seabed.

Operational effects are more limited Mooring requires lengthy chains and cables that rest on the sea bed and these can cause damage to heritage assets.

Changes to sediment processes and associated coastal erosion might cause impacts on some resources but may also help to reduce energy reaching shore and some erosion related heritage impacts.

Visual impacts for the setting of historic features during operation, construction and decommissioning.

There is the potential for placement of offshore mooring structures or shoreline devices on known and designated historic sites, and on unknown sites ( i.e. wrecks). The potential may also exist for adverse effects on historic sites located nearby or downstream of offshore devices during operation ( i.e. scouring, deposition/siltation or abrasion from offshore support structures; scouring, changes in sediment dynamics and changes in the coastal profile/character from shoreline devices).

Adverse effects are likely to be avoided through careful siting of individual devices and their supports or moorings, although this may be more difficult for shoreline structures, large gravity bases or arrays of bases.

Pre-construction impacts can result from intrusive site investigation.

Construction effects as a result device installation, in particular from moorings, chains and cables. In particular as a result of piling and preparation of the seabed disturbing historic features.

Secondary effects from construction might arise from vessels anchoring and from temporary visual impacts on the setting of historic features

Associated cables and grid could directly impact on archaeological features on the seabed.

Operational effects are more limited Mooring requires lengthy chains and cables that rest on the sea bed and these can cause damage to heritage assets.

Changes to sediment processes and associated coastal erosion might cause impacts on some resources but may also help to reduce energy reaching shore and some erosion related heritage impacts.

Visual impacts for the setting of historic features during operation, construction and decommissioning.

Landscape and Seascape [16]

Summary of key potential effects on land/seascape include:

  • For linear structures, with devices at 0-5km from the coastline, effects may occur for all seascape types. The further from the coast, the less the effect becomes, and beyond 10km the effects are typically minor.
  • For point structures, 8 out of the 10 seascape types are of high sensitivity to these types of device, with potential effects occurring at 0-10km from coastline. Moderate effects may also occur at distances over 10km.
  • Submerged structures are likely to have negligible effects on seascape (although marker buoys and lighting may be required)
  • Fixed coastal structures may have moderate effects depending on their design and location.
  • Landscape and visual intrusion from substations and overhead lines as onshore grid connections.

Key measures to prevent adverse effects may include: maximising the distance of devices from shore; reducing the height of devices above the surface; reducing the area of sea occupied by the devices; and modifying the position and layout of devices to suit characteristics of the local seascape; carry out detailed routeing studies at project level in accordance with 'Holford Rules' best practice guidance on routeing overhead transmission lines; avoid sensitive sites and areas; provide screening (substations).

The presence of surface-piercing devices, structures and marker buoys ( e.g. lights for navigation) may have the potential to alter the aesthetic character of the coastline, particularly if located near-shore and in large numbers.

In general terms, 8 out of the 10 seascape types are of high sensitivity to point structures such the surface-piercing structures on this device, with the potential for effects occurring at 0-10km from coastline. Moderate effects may also occur at distances over 10km.

Despite having a low profile comprising units on or above the water surface ( i.e. Pelamis, bulge wave devices), these devices may have the potential to alter the aesthetic character of the coastline if placed in near-shore areas, particularly if surface-piercing support structures are also present.

In general terms, effects may occur for all seascape types with the presence of linear surface-piercing structures on devices less than 5km from the coastline. The further from the coast, the less the effect becomes, and beyond 10km the effects are typically minor.

The low profile of surface-piercing structures above the water surface may have the potential to alter the aesthetic character of the coastline, particularly if navigational lighting is used ( i.e. noise and visual impacts).

No surface-piercing components, therefore no impacts identified during operation.

There may potentially be temporary impacts during installation or decommissioning.

The profile of surface-piercing structures above the water surface (offshore) or on the shoreline (shoreline) may have the potential to alter the aesthetic character of the coastline ( i.e. noise and visual impacts).

The profile of surface-piercing structures above the water surface (offshore) or on the shoreline (shoreline) may have the potential to alter the aesthetic character of the coastline ( i.e. noise and visual impacts).


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