Scottish Marine and Freshwater Science Report Volume 2 Number 13

Results of the MaRS Modelling

4.1 Technical Constraints Model

The output from the Technical constraints model ( Figure 1) clearly demonstrate the increasing difficulty of development towards the middle of the North Sea and in areas to the north of Shetland. Areas with annual mean significant wave height of 3m or more were treated as excluded in the technical model and this, combined with lack of some data, has limited the output from the model at about 8 degrees west, but is may be assumed that these areas also are progressively more constrained further west. The apparent lack of constraint in some grid cells at the western edge of the modelled area is a spurious edge effect and is of no significance.

The least technically constrained areas are found generally within Scottish Territorial Waters to the west and north of Scotland and around the Orkney and Shetland islands, and in a strip of around 15 - 30 miles width round the eastern side of Scotland. Wind speeds immediately adjacent to the coast are generally less than those a few miles offshore, making these slightly offshore areas less technically constrained. In addition to the factors covered in this model, the depth of water acts as an important constraint through its influence on the types of foundations for turbines that are appropriate. The influence of depth on development potential is considered in more detail in section 5.6.

Figure 1 Output from the technical constraints model for offshore wind development in Scottish waters.

4.2 Industry Restriction Model

The output from the Industry restriction model ( Figure 2) is dominated by the predominance of current "industrial" activity in the coastal zone. For example, aquaculture is currently entirely limited to waters within a short distance of the shoreline, as is much of the shipping activity (ferries, vessels on passage around Scotland). Some of our most valuable fishing grounds are in the sheltered waters of the Minch and aviation routes to oil and gas installations in the North Sea are a clear feature of the east coast off the Grampian region.

4.3 Environmental Restriction Model

The output from the Environment restriction model ( Figure 3) again indicates greater levels of constraint in inshore waters. Relatively high levels of constraint in the North and South Minches will be influenced by their importance to seabirds and marine mammals. The designated areas around Rhum and St Kilda, and in the inner Moray Firth are prominent, as is the general importance of waters off the east coast between Peterhead and Berwick to seabirds.

4.4 Heritage Restriction Model

The output from the Heritage restriction model ( Figure 4) generally indicates low levels of constraint in most areas of Scottish waters. The areas where constraint is encountered are dominated by areas in and adjacent to National Scenic Areas, where particular sensitivity to offshore wind farms may be anticipated. It may be noted that the model does not capture seascape and visual impact issues in areas that are not designated, and it may be anticipated that such matters will be significant aspects of consenting in many other areas not presently designated. Further contributions to heritage restrictions arise from yachting and sailing activity and the potential for sub-sea archaeological remains.

Figure 2 Output from the industry restriction model for offshore wind development in Scottish waters.

Figure 3 Output from the environmental restriction model for offshore wind development in Scottish waters.

Figure 4 Output from the heritage restriction model for offshore wind development in Scottish waters.

4.5 Combined Models

An expression of the overall level of constraint on wind farm developments in Scottish waters needs to take account of environmental, industry and heritage restrictions. The Sensitivity Analysis noted that the presentation of the information by theme reduced the difficulties inherent in developing relative weightings for very diverse types of data ( e.g. the relative weighting of seabird colonies, wrecks, fish landings, and basking shark sightings). The current Scoping Study has been carried out with the minimisation of consenting risk in mind. Having grouped the data and developed thematic restriction models, it is now possible to combine the models within MaRS and assess the sensitivity of the outputs to variation in the overall weighting between themes. This approach had previously been used successfully in the Scoping Study for the Saltire Prize

Four Combined models were created, in which the relative weightings of the themes were changed. In an Equal Weighting model, the three themes were weighted equally. Three further models were developed, in which each of the themes was assigned a weighting equal to the sum of the weightings for the other two themes, as in Table 1.

Table 1

	Environmental theme	Industry theme	Heritage theme	Figure
Equal weighting constraints model	100	100	100	Figure 5
Environmental focused constraints model	200	100	100	Figure 6
Industry focused constraints model	100	200	100	Figure 7
Heritage focused constraints model	100	100	200	Figure 8

The resultant models are shown in Figures 5, 6, 7 and 8.

There are some broad similarities between the outputs, i.e. features that are not very sensitive to the relative weightings of the three themes:

1. Constraint is generally a coastal phenomenon. Most of the activities in the sea, from all three themes, are concentrated in coastal waters. The degree of constraint decreases with distance from the coast. This is particularly clear in the North Minch area, where waters east of the Western isles are generally highly constrained, while those to the west of the Western Isles show much lower levels of constraint.
2. On the east coast, the most constrained areas are in the inner parts of the major firths, the Moray Firth and the Firths of Forth and Tay. The degree of constraint decreases seawards.
3. The North and South Minch are generally strongly constrained. However, there are areas on the west coast further south, west and south west of the Inner Hebrides, where the degree of constraint is much less. The level of constraint in inshore waters between the Inner Hebrides and the mainland is generally similar to that in the Minch.
4. The degree of constraint off the east coast of Scotland is less than in the Minch, but constraint if present over much of the Moray Forth persists for 30 miles or more offshore of most of the east coast. This feature is less prominent in the model which emphasises heritage interests, possibly because of the greater importance of designated scenic areas on the west coast.
5. The degree of constraint in Scottish waters in the Solway Firth is generally intermediate between that in the Minches and off the east coast. However, there is a narrow strip of water with lesser constraint along the boundary with Isle of Man waters.
6. In all areas, the levels of constraint outside STW is much less than that within STW. It is also decreases with distance offshore outside STW, such that at 30-40 miles offshore the levels of constraint are generally very low. There will be some sensitive areas, such at those associated with the oil and gas industry, where development may not be appropriate.
7. Relatively large areas within STW where the level of constraint is low occur off the west of Scotland between Barra and Islay, west/northwest of Cape Wrath, north and north west of Orkney. Smaller areas can be noted south of Islay, south of the Mull of Kintyre, and on the southern edge of Scottish waters in the Solway.

Figure 5 Combined restriction model, giving equal weight to the environmental, industry and heritage themes.

Figure 6 Combined restriction model, emphasising the environmental theme.

Figure 7 Combined restriction model, emphasising the industry theme.

Figure 8 Combined restriction model, emphasising the heritage theme.