Note 5

Visual Impact Assessment

About

Purpose and Scope Context Notes Case Studies Resources

The objective of the Guidance is to provide easy-to-understand and user-friendly information on wind energy projects and World Heritage protection and management, and to highlight processes and tools for overcoming potential challenges that may arise. The Guidance aims to assist in the planning of wind energy projects while providing insights to explore options for proactive conservation for World Heritage site managers and and heritage protection authorities.The core of the Guidance includes four main parts

About the Guidance
World Heritage Essentials

History and purpose of the Convention How does the Convention work? Decision-making and governing The World Heritage List Spatial boundaries of World Heritage properties and their importance for protection and management

This part of the guidance is designed to introduce basic World Heritage concepts to a non-specialist audience. The implementation of the World Heritage Convention on the national level can be challenging for States Parties.

The following text explains the basics of the Convention to better understand its spirit and underlying principles. It further outlines good practices that assist complying with recommended international conservation standards to fully deploy the effectiveness of the Convention and to achieve its ultimate goals. The described indications aim to help readers understand the purpose of requirements described in the Operational Guidelines for the Implementation of the World Heritage Convention, and to act accordingly constructively and proactively.

Word Heritage Essentials
Wind Energy Essentials

What is renewable energy? What is wind energy? How is energy generated by the wind? Components of wind energy infrastructure Potential impacts of wind energy projects on World Heritage Siting and design of wind energy farms Wind energy life cycle

This part of the Guidance offers an overview of wind energy related information primarily for heritage practitioners and decision-makers not familiar with this field.

A brief overview of the main technical features and processes behind wind energy planning will allow a more effective understanding of their potential impacts on World Heritage and catalyse more efficient dialogue between stakeholders to seek solutions. In addition, this section approaches this field with a focus on World Heritage matters, highlighting sensitive conservation issues.

Wind Energy Essentials
Protecting World Heritage

Understanding World Heritage properties and sharing information Strengthening World Heritage protection in policies and legal frameworks Decision-making and governing Engaging in early planning for wind energy infrastructures Proactive conservation actions – enhancing management in view of the energy transition

National strategies and policies for the transition to renewable energy and initiatives for decarbonization are often based on the strategic principles and guidelines set in international agreements and directives. This is, for example, the case in the European Union policies, which have direct influence on national planning. However, the implementation of international agreements or directives, such as those of the EU, relating to renewable energy is often not cross-checked and aligned with national policies and regulations protecting natural and cultural heritage, including World Heritage properties. It is similarly important that national policies, programmes, and plans, as well as the accompanying national legal frameworks, give due consideration to heritage protection and ensure full protection of World Heritage properties. In addition to the establishment of an appropriate legal framework, a proactive approach to site management could effectively supplement national legal tools and support and strengthen protection measures ensuring the preservation of World Heritage properties for future generations.

Protecting World Heritage during the Energy Transition
Impacts of Wind Energy Projects

Why is it important to assess the impacts of wind energy projects in a World Heritage context? Elements of impact assessment Participation of rights-holders and other stakeholders in an impact assessment process Types of impact assessments Strategic Environmental Assessments (SEA) Environmental and Social Impact Assessments (ESIA) Step-by-step Potential impacts of wind energy projects What should be considered before beginning an ESIA? Checklists

This part of the Guidance provides heritage and impact assessment practitioners, site managers and heritage institutions an overview of the process for assessing the impacts of wind energy projects associated with World Heritage properties. The information is intended to assist actors responsible for commissioning and preparation such impact assessments and to support decision-makers.

Impacts of wind energy projects and their assessment

A Visual Impact Assessment (VIA) is a specific study that focuses on assessing the visual and aesthetic impacts of a proposed project. This type of assessment is not a stand-alone study but should be part of the study that assesses impacts on the OUV of a World Heritage property (Environmental and Social Impact Assessment, or Heritage Impact Assessment study) – in the most likely case when it is relevant for its values. VIAs are largely used for assessing the impacts of proposed infrastructure projects in relation to cultural World Heritage properties inscribed for their architectural and landscape values. It is to be noted that visual qualities are primarily related to the integrity of a World Heritage property. World Heritage properties that are inscribed on the World Heritage List under the category of cultural landscapes might be especially vulnerable to wind energy developments.

➔ See World Heritage essentials

What should be considered in relation to the World Heritage property/properties?

The visual and aesthetic impacts of wind energy facilities on the landscape are one of the main challenges faced by the wind energy development. The perception of these facilities in a landscape depends on several factors: typology of the site, morphology of the landscape, social factors, the extension of infrastructural development in the area and the level of acceptance by local communities.

Wind energy projects not only need to consider the possible compatibility or incompatibility of wind turbines and ancillary facilities with the attributes that convey the OUV of a World Heritage property, but also need the willingness and support of the people and local communities to live with and adapt to the proposed changes of their environment. Visual aspects, in this respect, play an important role in the acceptance of these projects.

The assessment of the visual impacts of a wind energy project relates directly to the visual qualities of the OUV of properties within their aspect of integrity. From the point of view of World Heritage protection and management, the project should not compromise or marginalize the visual characteristics and attributes of a World Heritage property.

For a VIA in the World Heritage context, consideration should be given to:

the overall sensitivity of a World Heritage property and its setting to changes in general;
the sensitivity of the property to wind energy facilities that includes measuring qualitative and quantitative visual changes, considering particularly the installation of tall facilities like wind turbines or industrial set ups like sub-stations and power grids (for potential dimensions of the parts of a wind farm and ancillary facilities ➔ see Wind energy essentials);
the extent to which a property and its setting can adapt and support change while ensuring the protection of its OUV.

Information related to visual sensitivity of a World Heritage property and its attributes can be collected through the process of vulnerability studies/sensitivity mapping (➔ see Note 2). This process looks at the connection between the property’s OUV and its key panoramas and vistas, as well as intangible connections and ways in which people and communities perceive the property and its surrounding.

Further information on how the visual sensitivity of a World Heritage property could be identified

A visual impact assessment needs to include a detailed map showing the location of all attributes conveying OUV, all relevant vistas and panoramas, the physical location of the proposed development and any ancillary or annexed facility as well as other existing developments that might need to be considered to assess possible impacts and cumulative impacts. Nevertheless, depending on the characteristics of the property and its OUV, some attributes may be difficult to trace and map, and should therefore be considered beyond their physical location on a map.

➔ See Note 6

The information related to the World Heritage property and the planned wind energy development need to be combined for assessing the potential impacts:

Design and siting of the wind energy development project	Factors potentially creating the impact	Elements that need consideration during the assessment and evaluation of impacts
visibility of wind turbines	number of wind turbines design and colour of the turbines rotor diameter hub height and total height of wind turbines lighting of wind turbines at night	extent of visibility the surrounding landscape of the installation (natural or man-influenced surroundings with their visual sensitivity) the significance of view sheds
position of wind turbines and their ancillary facilities	distribution of wind turbines within the landscape and their position in relation to the World Heritage property and its buffer zone/setting	topographical characteristics of the property and its setting distance from important identified view sheds, vistas and panoramas of the property the significance of view sheds, panoramas, or vistas visual relationships between visually important attributes of the property dominance within the topography relationship/ interference with the significant topographic features scale contrast between the wind energy infrastructure and significant features and elements in the landscape conditions of geography, weather, etc. presence of neighbouring artificial structures presence of other artificial structures and existing wind turbines (accumulated impacts)
extent of the development	the area covered by the wind energy infrastructure

Visualization of impacts

The digital visualization of wind energy projects to support assessing their impact is at the core of VIAs. The production of a digital visualization requires adequate data, technical material and software. Good simulations or models are:

spatially accurate and realistic, simulating the expected appearance of the proposed project and the actual appearance of the property and its setting;
representing different views, including different viewpoints, day time/night time differences, weather conditions, lighting conditions, seasons and others;
visually clear and accurate including all necessary details of the proposed project and the property;
defendable and able to withstand scientific scrutiny.

Importance of visual simulations in engagement with rights-holders and other stakeholders

Accurate and realistic simulations are key during the consultation process in general but are especially important during the engagement with rights-holders and other stakeholders as they allow for people and communities to better understand and contextualize the project in relation to their environment and the World Heritage property.

Tools for visualizing and assessing the impact of proposed and planned wind energy infrastructures in relation to a World Heritage property and its setting could include:

digital terrain models (DGM) and digital surface models (DOM) which allow showing precise distances and heights between the property, the viewpoints and the potential placement of the wind turbines, including the topography in-between;
Photo simulation and photomontage: photographic-based assessments, like photomontage and modelling, should provide clear technical information concerning the position of the camera and the focal length used for the images used in the montage. This information is vital to prove the reliability of the recommendations derived from the visual impact study;
Viewpoint photography;
3D modelling and digital simulations;
Colour and light-based methods;
Zone of visual influence maps;
Line of sight technique which is a digital and GIS-based assessment that applies an accurate representation of the shape of wind energy facilities to better understand the visual perception of these facilities by the human eye. It considers the distortion of the perceived shape and size of facilities caused by the location of the observer and calculates the possible obscuring of facilities caused by terrain morphology. This also allows including information of other existing facilities to represent the landscape more accurately;
Landscape sensitivity assessments;
Landscape quality assessments;
Viewshed analysis in a GIS (or visual envelop) map: a digital evaluation model based on GIS data which is used to determine which parts of a landscape are visible or not visible from a particular vantage point.

Visualization tools	Data requirement	Comments
Digital terrain model and digital surface model	Both for DGM and DOM: identification of visually sensitive areas; views to buildings of cultural or historical significance; vantage points and locations frequented by a large number of visitors (walking trails, etc.); views in the direction towards the property (showing silhouettes from outside);	Viewpoints need to be chosen in agreement with all bodies involved. Advantage: allows immediate depiction and consideration of forests, buildings and obstructing views, etc.

Visualization tools	Data requirement	Technical requirements	Comments
photo simulation and photo montage	digital terrain and surface models selected viewpoints (vantage points/ observer points) exact location of the wind turbines exact type of the wind turbines adequate software tool for executing the simulation technically adequate photographic material for the simulation viewpoints from inside the property with views away from it to the outside also need to be considered	for the photographic material: precise geographic coordinates (including altitude) of the camera’s position and viewpoint date and time of the photograph type of camera lighting conditions (front lit, backlit, side lit) type and model of camera and lenses focal distance/ length (35 mm format in digital SRL cameras) width of lens angle (to provide realistic proportions between the landscape and the planned wind energy facilities) record of different weather conditions (including optimal visibility conditions) distance from the proposed development (i.e., wind turbine or other ancillary facilities) dynamic effect of the rotating blades coloured markings of towers and rotor blades and flashing lights on the nacelles and towers	the description of each photo simulation is very important including information on the viewpoint (taken where and what do we see?), its orientation (with directions and degrees), focal length, etc. and the number of viewpoints

Assessing visual impacts

Potential visual impacts should be evaluated by considering the visual sensitivity of the property combined with the potential magnitude and significance of the impact on the property’s OUV.

The assessment should be based on two key sets of information concerning:

1. Characteristics of the World Heritage property related to identified key visual aspects, scenic views and panoramas, including information on:

the topography of the property and the connections within the property, and between the property and its setting;
attributes conveying the OUV of the property and values that are not part of the OUV but have a role to support it;
key observation points (KOPs) including sensitive areas, panoramas and viewsheds that can support the protection of the OUV.

2. visual characteristics of the proposed wind energy installation, including information on the wind turbines and, if applicable, the ancillary facilities:

scale of the wind energy project;
location of the wind energy facilities;
form of the wind turbines and other facilities;
height (hub and with blades) of the wind turbines and other facilities;
rotor diameter of the wind turbines;
colour, including possible colour contrast of the wind turbines with the surrounding land- or seascape;
texture/material of the wind turbines and other facilities;
glare of the wind turbines;
lighting of the wind turbines;
motion of wind turbines;
number and distribution of the wind turbines within an area;
visual lines and axes of the facilities (paths followed by the eye when perceiving obstructions and abruptions in a landscape).

There are multiple methodologies for the identification of possible visual impacts and many more for the evaluation of these impacts. There is no standard nor a universally or unilaterally agreed methodology to assess the visual impacts of wind energy facilities on a World Heritage property. Therefore, the decision in favour of a specific VIA methodology should be justified by technical considerations about the OUV of the World Heritage property and the proposed wind energy project. Nevertheless, as already mentioned, visual impacts of wind energy projects should never be assessed in isolation but be considered within the scope of a fully fledged World Heritage focused impact assessment and together with other impacts, including environmental, cultural heritage, social and economic impacts.

The methodology applied in the assessment should be described clearly and with specific reference to the evaluation criteria considered during the process. There are various possible typologies of assessments with consolidated scientific and technical requirements, and should all consider with quantitative and qualitative methodologies:

the extent of the visibility of a wind energy facility (like maximum vertical angle of visibility, horizontal angle of visibility);
the distance of the project and its element that are visible (and wind turbines, other features of the project) from identified key observation points and viewpoints;
the number of visible wind turbines and other features of the project (at a given vertical angle and above);
the significance of the viewshed;
the character of the landscape or seascape, and the surroundings of the installation (natural or man-influenced surroundings with their visual sensitivity relevant for the OUV of the property).

The degree of impacts will need to consider the level of visual intrusion and obstruction in relation to identified sensitive areas or key panoramas and vistas.

Assessing the level of impacts

Degree of impact	Description
Large	A wind energy project is intrusive, dominant and/or extensive with direct impact on the attributes of the OUV and the wider setting of the property. The project would considerably transform the characteristic of the property. (The proposed wind energy project would completely change the character of the setting of the property resulting in negative impacts that cannot be mitigated as they will have major negative effects on the OUV of the property).
Medium	A wind energy project is noticeable and with potential impact on the property or part of its OUV. Wind turbines and ancillary facilities are an uncharacteristic element in the property and its landscape. (This could result in the wind energy installation being out of scale with regards to attributes of a property’s OUV or they might be located somewhat visibly inside a key view or panorama).
Small	The visual changes introduced by the wind energy project are limited and do not completely alter the characteristics of the property and its setting. (Mitigation measures could be considered to avoid any negative visual impact).
Negligible	The proposed wind energy project consists of a visual change, which is not perceptible. (The proposed project has no visible negative impact on the property and its OUV. This could be the case of projects complementing or maintaining the scale and quality of the surrounding landscape).

Table: Magnitude of impact, adapted from Apostol et al. (2016).

Examples of potential visual impacts of wind turbines on the OUV of World Heritage properties are listed as below

Potential type of impact	Description	Examples
Technology overload effect	The technology overload effect arises when the number of technological items in an area increases to a point that their visual presence overweighs the character of the embedding or juxtaposed cultural landscape with its natural and cultural historical structures and elements.	Natural landscapes and elements of natural beauty and aesthetic importance in a landscape may be considerably altered, cultural and historical buildings may lose their importance on the horizon, and views may be disrupted.
Visual dominance	The visual dominance is a consequence of the size and the high visibility of wind turbines; the observer recognizes primarily the huge wind turbines instead of the cultural or natural heritage elements or the natural phenomena in a landscape.	The wind turbines alter the existing harmonious relationships between the different characteristics and elements of natural beauty and aesthetic importance in a landscape. The movement of the rotors create a ‘disquieting’ effect in the landscape and disturb the natural tranquillity.
Loss of scale	The effect of a loss of scale means that, beside the new technical installations of wind turbines, well-known big natural elements like trees or cultural elements, such as towers or castles, visually shrink and become dwarfish. The new scale is out of proportion.	The scale of visual influence and of impairment is such that the turbines and related facilities let the surrounding buildings, natural features and elements of natural beauty and aesthetic importance in a landscape shrink and affect their values.
‘Barrier effect’	This is generally caused by the alignment of wind turbines creating a visually present barrier between different landscape elements.	The wind turbines may cut through a landscape and interrupt key views and the interrelationships between different landscape features or interrupt key views that are part of the OUV, or furthermore, separate the World Heritage property from its embedding landscape. The continuity of a landscape with view axes from short and long distances may get lost.

Case Study

See case studies in World Heritage and Wind Energy Planning (2021)
In 2013, the Landscape Institute for Environmental Management and Assessment (IEMA) published a Guidelines for Landscape and Visual Impact Assessment (GLVIA3).This is a key resource for those involved in assessing visual impacts or reviewing an impact assessment report including specific references to the assessment of visual and landscape impacts. Although the guidance is not a World Heritage specific document and does not focus on the OUV of World Heritage properties, it nevertheless could serve as key guidance for the assessment of a property’s visual sensibility and for the identification and evaluation of possible visual impacts.

A useful document prepared by the NGO Kompetenzzentrum Naturschutz und Energiewende facilitate wind energy project planning in Germany (available in German).
A study on visual integrity has been prepared for the Dutch Water Defence Lines World Heritage property (the Netherlands) on assessing visual impacts.