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Case Study: Assessing the potential visual impact of onshore wind energy projects in relation to a World Heritage property in the United Kingdom

United Kingdom of Great Britain and Northern Ireland

In the period between 2004 to 2008, Historic England was dealing with an increased number of renewable energy applications that could be seen from the Hadrian’s Wall World Heritage site. In response, Historic England (under its earlier name of English Heritage) focused on developing an approach to the assessment of potential impact of this kind of development which placed the significance of the World Heritage site at its centre. The aim was to have a robust methodology for understanding impact and allowing informed and transparent decisions under England’s spatial planning system.

© Ko Hon Chiu Vincent

State Party:
United Kingdom of Great Britain and Northern Ireland

World Heritage property:
Frontiers of the Roman Empire (transnational property)

Component part:
Hadrian’s Wall


Year of inscription:

2005, 2008

Brief description:

The ‘Roman Limes’ represents the border line of the Roman Empire at its greatest extent in the 2nd century AD. It stretched over 5,000 km from the Atlantic coast of northern Britain, through Europe to the Black Sea, and from there to the Red Sea and across North Africa to the Atlantic coast. The remains of the Limes today consist of vestiges of built walls, ditches, forts, fortresses, watchtowers and civilian settlements. Certain elements of the line have been excavated, some reconstructed and a few destroyed. The two sections of the Limes in Germany cover a length of 550 km from the north-west of the country to the Danube in the south-east. The 118-km-long Hadrian’s Wall (UK) was built on the orders of the Emperor Hadrian c. AD 122 at the northernmost limits of the Roman province of Britannia. It is a striking example of the organization of a military zone and illustrates the defensive techniques and geopolitical strategies of ancient Rome. The Antonine Wall, a 60-km long fortification in Scotland was started by Emperor Antonius Pius in 142 AD as a defense against the “barbarians” of the north. It constitutes the northwestern-most portion of the Roman Limes.

See further details at: https://whc.unesco.org/en/list/430

The approach developed from 2004 to 2008 is still applied to assess projects proposed to be installed at the site of Hadrian’s Wall and its setting. The approach was based on Historic England’s guidance: The Setting of Heritage Assets (revised in 2017). The document places the emphasis on understanding the significance of a site and the role that setting plays in this, to then allow an understanding of the way that a particular development impacts on that asset. This approach is fully supported by the (National Planning Policy Framework (NPPF), which integrates the protection of World Heritage properties and their setting (paragraphs 189 and 194) alongside provisions on the importance of understanding the impact of proposals on the significance of heritage assets (paragraph 194).

The projects in question

One of the key wind energy developments at this time was the proposed installation of a group of three separate windfarms on hills around 15 km to the north of the central sector of Hadrian’s Wall. Here, the setting of the property is characterized by an upland landscape, with long views over very sparsely populated terrain divided by deep river valleys. The turbines proposed were 100 m in height and, despite the distance from the Wall, would have been a highly visible feature within a predominantly rural landscape. There was then no doubt that the wind turbines proposed would be a new and conspicuous element in the Wall landscape – but the question was whether it would cause harm to the World Heritage site.

Impact assessment related measures

The assessment of possible impacts derived from the proposed project was based on the Statement of OUV, as well as the nomination and acceptance documents. These clearly show that the area around Hadrian’s Wall plays a role in its significance, where it allows an understanding and appreciation of Roman military planning and land use.

In the central sector, the Wall was positioned on high ground not only because it was more defensible, but also to allow Roman troops to have a general view of their surroundings. However, the terrain to both north and south includes a series of valleys with several areas that cannot be seen from the Wall, suggesting that in this sector, Roman troops did not only rely on direct observation for their protection, but were more likely to have controlled the northern approaches to the Wall via military patrols. The views north, across the hills and hidden ground in the valleys, did not then play such a crucial role in the planning and operation of the Wall frontier.

Summary of impact assessment result

Following this approach, the ability to see turbines on distant hills did not harm the OUV of the property as the Romans didn’t design their frontier and base their control of this landscape in a way that was reliant on views of these distant hills. Therefore, although the turbines on the hills would be visible, they wouldn’t interrupt or harm any views crucial in understanding and appreciating the Hadrian’s Wall frontier.

The approach of an impact assessment focused on OUV brought different results when assessing a proposal for another wind energy project on the Cumbrian coast. Here the coastline was the defended frontier line, with a series of towers and fortlets located every 600 m to look for enemy incursions from across the sea, which were also sited to communicate visually with each other.

The impact assessment highlighted that, due to the curved orientation of the coast in this area, the turbines would sit visually just behind the line of the frontier. Because of this, they would distract the eye and harm the ability to understand and appreciate the Roman military planning and operation of the frontier. In this case, Historic England’s assessment focused on the ability to appreciate and understand the presence of the frontier around and along this the coast, and the impact on the intervisibility of the locations of these Roman military installations. The proposed wind energy project was assessed as having potential negative impact on the property’s OUV because of the distraction that it would cause.

The wind farms in the central sector were given permission, were developed and became operational in 2012. The advice of Historic England that, despite the visibility, the turbines would not cause harm to the OUV was considered an important factor in this decision. At the time of the decision, some public concerns were expressed about the impact on the landscape beauty of the Wall area, and how this might affect the experience of visitors to the Wall, even if these strictly lie outside of the OUV of the World Heritage site. However, once the wind farms were constructed, there has been very little criticism of the decision to allow them, or concern expressed about impact on OUV. (See Image 1).

Image 1 – Turbines visible from Hadrian’s Wall at Limestone Corner, Northumberland.

On the Cumbrian coast, the decision was taken to refuse permission for the turbines, and a key reason for this was their impact on the World Heritage site. The same part of Cumbria has seen a significant number of other wind farms given permission, but in each case a focused assessment of impact on OUV was undertaken. It was concluded that such impacts would not occur even if the turbines were visible from the World Heritage site. (See Image 2)

Image 2 - Roman defences of the Cumbrian Coast. The photograph is taken from the Roman fort at Maryport. The arrow shows the site of Milefortlet 21 which is thought to have been in direct visual communication with the fort. The proposed wind turbines would have appeared immediately behind the Milefortlet site, distracting the eye and harming understanding of the Roman landscape.

Important lessons learned from the project

The assessment of the potential impacts of the proposed wind energy projects on Hadrian’s Wall was facilitated by technical and historical information included in the property’s Statement of OUV. This not only comprised the individual Roman sites along on the frontier, but also the landscape around it which made it clear that this landscape had a role in the significance of the site as it enhanced the understanding and appreciation of Roman military planning and land use. This understanding of where significance lies allowed Historic England to move away from assessing whether wind turbines and other wind energy facilities were visible from Hadrian’s Wall and focus on assessing whether each proposed project was harmful to the protection of the property’s OUV.

This explicit focus on impact on OUV, rather than simple questions of visibility or impact on landscape more generally allows decision-makers to be much clearer about whether harm to significance of the World Heritage site is going to occur. In the context of the climate emergency, this transparency is vital so that heritage can be appropriately protected. However, where harm will not occur then renewable energy development is allowed.

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