Scottish Marine and Freshwater Science Volume 3 Number 1: Scoping study for tidal stream energy development in Scottish waters

3 Structures of the Models Used

As described in the documentation supporting The Strategic Environmental Assessment for Offshore Wind (Scottish Government, 2010a), 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 technical resource assessment or to a non-Technical Model. The non-Technical Constraints Model was comprised of the outputs from three thematic Restriction models, covering constraints arising from industrial activity, environmental factors, and socio-cultural interests. The socio-cultural 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 Socio-cultural Restriction Model ( MaRS ref. 2758)

Data layer	Weight	Maximum score	Potential relative influence
National scenic areas	600	60	36000
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
Surfing beaches	400	40	16000
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 ( MaRS ref. 2751)

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	900	100	90000
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
Possible sea haul out sites	900	90	81000
Areas of importance to basking sharks	700	70	49000
Nursery areas for commercial fish species	300	55	16500
Spawning areas for commercial fish species	300	55	16500
Areas of search for potential Marine Protected areas	600	60	36000
Areas of search for seabird aggregations	400	40	16000
Areas of importance to breeding sea birds	800	145	116000
Areas of importance to sea birds in winter	500	50	25000
Areas of importance to marine mammals	800	145	116000

3.3 Industry Restriction Model ( MaRS ref. 2565)

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
Current Licensed Areas for Hydrocarbons	700	70	49000
Closed waste disposal sites	700	70	49000
Military Practice and Exercise Areas	1000	180	180000
Shipping density	800	145	116000
Commercial fisheries landings	1000	182	182000
Dredging	1000	100	100000

The commercial fishing layer in the Industry restriction model was created in a separate

fishing model using data layers and scores as shown below:

Commercial Fishing Model ( MaRS ref. 2565)

Commercial fisheries landings from mobile gear in inshore waters	700	127	88900
Commercial fisheries landings from static gear in inshore waters	700	127	88900
Commercial landings from fishing vessels >15m using mobile gears	700	127	88900
Commercial landings from fishing vessels >15m using static gears	700	127	88900

3.4 Non-technical Exclusion Model ( MaRS ref. 2568)

The following features were treated as incompatible with tidal stream farm development, i.e. areas covered were used to create an overall special model of areas from which tidal stream 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
Operational Anemometers in UK Waters
Protected Wreck Exclusion Buffers
UK offshore wind activity
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 Tidal Stream Resource Assessment

Tidal stream resource was assessed in terms of the mean spring peak tidal flow, and the mean annual power density. The former provides a screen to ensure that the necessary speed of current is available at a potential development site, while the power density provides an indication of the persistence of suitable currents and therefore the period within tidal cycles that devices may operate satisfactorily.

The outputs from the restriction models, after normalisation against the exclusion model, should be viewed in the context of technical (resource) opportunities of the areas under consideration.

3.6 Improvements to the Previous Spatial Modelling

The use of MaRS to develop Scoping Studies for marine renewable energy has been characterised by progressive improvements in the available data, and the data handling. Some significant differences from, and additions to, previous models have been implemented in the current exercise. The main improvements made were:

1 Surfing beaches. There may be some potential for tidal energy devices close to the coast to affect the wave spectrum reaching the coast, and this in turn may affect the suitability of coastal areas for surfing. The locations of surfing beaches were taken from the data in National Marine Plan interactive ( NMPi), the data underlying the development of Scotland's Marine Atlas (Scottish Government, 2011a).

2 Commercial fishing: The landings from commercial fishing activities were separated to represent mobile and static gears, and VMS and non- VMS (<15m, mostly inshore) vessels. In inshore waters, landings were partitioned between internal waters, 0 - 6 miles, 6 - 12 miles, and landings from greater distances within ICES statistical rectangles that also include areas within STW were identified. Based on current tidal stream project design plans, is likely to be difficult to operate commercial fishing activities, using either mobile or static gear, within the footprint of tidal stream farms. The four combinations of inshore and offshore vessels, mobile and static gear, were therefore given equal weight.

3 The offshore wind Scoping Study gave considerable weight to factors related to aviation. These factors are omitted from the current study, as interactions between tidal steam farms and aviation are likely to be insignificant.

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. This layer had initially been used in the Wind Scoping Study (Davies and Watret, 2011), and was carried forward into the current study.

5 Sensitivity of areas to seabirds: An initial approach was made to developing indices of the relative sensitivity of sea areas for vulnerable seabirds. Collision of diving seabirds with tidal turbines particularly needs to be taken into account . Mapped data on the distribution of 7 SPA species of sea birds at sea during the breeding and winter seasons (European Seabirds at Sea survey, JNCC) were expressed in terms of the total Scottish population of each species. The distributions of species known to dive to depths where they might encounter tidal turbines were combined to give an overall expression of the relative sensitivity of sea areas in the winter and in the breeding season. The seabird species were chosen using information on diving behaviour ( RPS 2011), and were Atlantic puffin, common guillemot, European shag, great cormorant, Manx shearwater, northern gannet, and razorbill.

6 Disturbance of seals at sensitive periods in their life cycle may arise from the construction and operation of wave farms in coastal waters. Following from the Marine (Scotland) Act 2010, preliminary work has been carried out to identify important seal haul out and breeding sites around Scotland. A data layer was created showing haul out sites for both grey and harbour seals, and buffers created out to 30 km.

7 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.

8 Fish spawning and nursery areas: Maps derived from Coull et al, 1998 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.

9 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 was done in the Saltire Prize Scoping Study) 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 previous reports, for improvements to underlying data, almost all were achieved and further additions made. Exceptions were:

a) that SACs were not filtered for sensitivity to tidal stream energy developments.

b) the distribution of SNH Priority Marine Features ( PMF) 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.