Scottish Marine and Freshwater Science Report Volume 2 Number 13

This report describes the process employed by Marine Scotland to identify strategic search areas for future commercial scale offshore wind developments in Scottish Territorial Waters (STW). It also presents the first discussion of the development potential outside STW out to 200 nm

Structures of the Models Used

As described in the documentation supporting The Draft Plan and associated Strategic Environmental Assessment (Scottish Government, 2010a, b), and as is normal in the use of MaRS, the data layers had been classified as either exclusion layers ( i.e. indicating areas where development was not appropriate), or constraint layers ( i.e. indicating the distribution of factors that acted as partial constraints on development). The constraint layers were each allocated a weighting. Within each constraint layer, the data had been assessed through a scoring scheme. The constraint layers were allocated either to a Technical Model or to a Constraints Models. The Constraints model was comprised of the outputs from three thematic Restriction models, covering constraints arising from industrial activity, environmental factors, and heritage interests. The heritage layer is broad in its scope, covering visual and recreational factors as well as historical heritage and archaeological potential. The outputs of these models had been normalised against the Exclusion model.

The data layers which were included in the various models were as follows:

3.1 Heritage Restriction Model

Data layer Weight Maximum score Potential relative influence
National scenic areas 900 90 81000
Royal Yachting Association cruising routes 300 30 9000
Royal Yachting Association racing areas 300 30 9000
Royal Yachting Association sailing areas 300 30 9000
Scheduled Ancient Monuments 800 80 64000
Bathing beaches 500 50 25000
World Heritage sites 1000 100 100000
Wrecks 700 70 49000
Protected wrecks 700 70 49000
Potential for marine archaeological remains 700 70 49000

3.2 Environmental Restriction Model

Data layer Weight Maximum score Potential relative influence
Bird reserves 800 80 64000
Important Bird Areas 500 50 25000
Local nature reserves 800 80 64000
Special Areas of Conservation 1000 100 100000
Special Protection Areas 1000 100 100000
Sites of Special Scientific Interest 1000 100 100000
Offshore candidate SACs and SPAs 1000 100 100000
Offshore draft SACs and SPAs 1000 100 100000
Offshore possible SACs and SPAs 1000 100 100000
RAMSAR sites 1000 100 100000
Nursery areas for commercial fish species 400 73 29200
Spawning areas for commercial fish species 400 73 29200
Areas of search for potential Marine Protected areas 400 40 16000
Areas of seabird aggregation 400 80 32000
Areas of importance to vulnerable sea birds 1000 182 182000
Areas of importance to marine mammals 900 164 147600

3.3 Industry Restriction Model

Data layer Weight Maximum score Potential relative influence
Offshore cables in UK waters (not active 500 100 50000
Pipelines in UK waters (not active) 500 100 50000
Potential gas and CO 2 storage sites 800 80 64000
Carbon capture and gas storage infrastructure 800 80 64000
Civil Aviation Aerodrome Buffers 800 80 64000
Civil Radar Interference (at 140 m above mean sea level) 600 100 60000
Royal Air Force Airfields and Stations Buffer (24 km 800 80 64000
Current Licensed Areas for Hydrocarbons 700 70 49000
Oil fields 400 40 16000
Closed waste disposal sites 700 70 49000
Helicopter main routes 600 100 60000
Military low flying areas 700 70 49000
Military Practice and Exercise Areas 1000 180 180000
Shipping density 1000 182 182000
Areas identified with potential for tidal power development 800 80 64000
Areas identified with potential for wave power development 800 80 64000
Commercial fisheries landings from mobile gear in inshore waters 1000 182 182000
Commercial fisheries landings from static gear in inshore waters 600 109 65400
Commercial landings from fishing vessels >15m using mobile gears 1000 182 182000
Commercial landings from fishing vessels >15m using static gears 600 109 65400

3.4 Exclusion Model

The following features were treated as incompatible with wind farm development, i.e. areas covered were used to create an overall special model of areas from which wind farms should be excluded at this time.

All Offshore Cable inside UK Waters
All Pipeline in UK Waters
Anchorage Areas
Aquaculture Leases - Current
Aquaculture Leases - Pending
Waste disposal sites (open)
IMO Routeing - excluding ABTAs
Munitions Dumps
Offshore Shipping Zones
Offshore Wind Farm Demonstration Sites
Operational Anemometers in UK Waters
Protected Wreck Exclusion Buffers
Round 1 Offshore Wind Farm Sites
Areas identified under Saltire Prize process as having high potential for tidal power
Areas identified under Saltire Prize process as having high potential for wave power
Shipping Density - Exclusion Areas
Tidal Leases - Live
UK Deal oil and gas Safety Zones
UK Deal oil and gas Surface features
UK Deal oil and gas Subsurface features
UKCS Exclusion Buffer - 500 m
Wave Leases - Live
UK Detailed Coastline - not including Isle of Man (Polygon)

3.5 Technical Model

Data layer Weight Maximum score Potential relative influence
Available wind resource 1000 182 182000 (positive)
Distance from the coast 300 100 30000 (negative)
Mean wave height 400 100 40000 (negative)

The outputs from the restriction models, after normalisation against the exclusion model, should be viewed in the context of technical opportunities and constraints of the areas under consideration. A simple Technical model, as above, was developed that combined the benefits of increased mean wind speed with the increasing difficulties in construction and operation with distance offshore and mean wave height. A further significant technical constraint is the depth of water. This is taken into account in section 5.6 of the report, primarily in relation to areas outside STW.

3.6 Improvements to the Previous Spatial Modelling

The Sensitivity Study noted various areas in which improvements could be made to the data layers available for use in MaRS. The main improvements made during the current exercise were:

  1. Landscape and visual issues: Develop a buffering system around national scenic areas ( NSA) to reflect the decreasing visibility of wind turbines with distance from the NSA boundaries.
  2. Commercial fishing: To separate landings from >15m vessels ( i.e. those covered by the Vessel Monitoring System) using mobile gears from those using static gears. The latter may be less vulnerable to the development of wind farms than the former.
  3. Commercial fishing: To identify landings from smaller vessel operating within STW, and to partition these between internal waters, 0 - 6 miles, 6 - 12 miles, and landings from greater distances within ICES statistical rectangles that also include areas within STW. Areas. To separately identify landings from mobile and static gears.
  4. Potential for archaeological heritage remains on the seabed: Maps indicating areas of the current seabed which had been exposed as land at some time since the Ice Age (and had high potential and theoretically high potential for marine archaeology) were combined with maps of seabed sediment type and structure to identify areas of seabed where potential for archaeological remains coincided with favourable seabed conditions.
  5. Sensitivity of areas to seabirds: An initial approach was made to developing an index of the relative sensitivity of sea areas for vulnerable seabirds. Attention was paid to collision risk during the breeding season. Mapped data on the distribution of 17 species of sea birds at sea during the breeding season (European Seabirds at Sea survey, JNCC) were expressed in terms of the total Scottish population of each species. These distributions were scaled according to the typical proportion of birds flying at typical turbine heights, and then combined to give an overall expression of the relative sensitivity of sea areas.
  6. Sensitivity of areas to marine mammals: Data from the JNCC cetacean atlas of the distribution of marine mammals at sea were scaled to the Scottish populations of each species and then summed to express the overall importance of sea areas to marine mammals.
  7. Spawning and nursery areas: Maps derived from Coull et al, 1999 showing areas of spawning and nursery grounds for 14 commercial fish and shellfish species were gridded and combined to show counts of spawning species or nursery ground species within each grid cell. The resulting layers were scored and weighted.
  8. Designated areas for the protection of birds: There are a number of different designations for marine or coastal areas for the protection of birds, including RAMSAR sites, SPAs, SSSIs, RSPB reserves, local reserves, IBAs etc. In many cases, areas hold more than one designation, and treating each form of designation independently (as has been done previously) resulted in potentially multiple counts of the same area for the same environmental sensitivity (birds). The data were therefore processed such that only the most important designation of any particular area was included in the final data layers, for example an area designated at European, national and local levels would be considered as designated at European level, whereas an area designated at local level only would be scored as a local designation.

Of the suggestions made in the Sensitivity Analysis report for improvements to underlying data, almost all were achieved. Exceptions were:

a) that SACs were not filtered for sensitivity to wind farm developments. This will have little impact on the outputs, as most designated SACs are coastal, and the models took into account the current search areas for offshore SACs.
b) the distribution of SNH Priority Marine Features was not taken into account. A significant amount of work will be necessary to convert the available information on the distributions of PMFs into a form suitable for inclusion in spatial modelling.

All the suggestions for alterations to the scoring and weighting systems were implemented.

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