Engineering in the eye of the beholder

Engineering in the eye of the beholder

From a wind farm on the Cape west coast to a mine next to a Mozambican village – any development that affects an area’s sense of place could have an unacceptable visual impact; no wonder that assessing and mitigating these impacts is becoming a specialised task.

Long involved with investigating and advising on environmental, social and economic impacts of industrial projects and mines, SRK Consulting’s Cape Town office now has a dedicated visual impact assessment (VIA) team comprising landscape architects Scott Masson and Larissa Heyns.

“It’s a particularly useful skill set that we bring for VIAs,” said Masson, “as we need expertise in fields like environmental planning, landscape analysis and geographical information system (GIS,) and mapping tools to create 3D models for clients.”

Their architectural training and experience also allows them to understand the implications of clients’ designs, said Heyns. “It’s important for us to be able to visualise what a project is going to look like before it is built, as this is vital for assessing and mitigating its visual impact,” she said.

Like other specialist studies, the work starts with a baseline study to identify and investigate the visual landscape and the key components of the project that could visually impact the landscape.

“We visit sites to identify the main view corridors and viewpoints from which the project will be visible,” said Masson. “Images from these points are overlayed using other mapping techniques to derive information about the visual character, visual quality and sense of place of the area.”

After the affected environment is described in this way, information about the project and its dimensions is analysed, and the two aspects are superimposed to create a ‘viewshed’ – which refers to the project’s zone of visual influence.

“Taking the example of a wind farm, the turbine is a certain height and we’ll know its proposed location,” he said. “We can then use GIS techniques –to place that point on the landscape and establish points from where it will be visible, creating a map or viewshed of the area that predicts where most visual impacts will occur.

“We can then take it a step further by using a colour gradient on the map to indicate how many turbines will be visible from any one point.”

A VIA has to consider the notion of visibility in various ways, including the viewing distance. If there are two farmsteads, the impact on the nearer farm is clearly going to be higher, since impacts attenuate over distance. “But we also have to consider the visual absorption capacity of the landscape – how effectively the landscape can screen or accommodate the project,” he said. “For instance, a project may be close to surrounding farmsteads but the topography or vegetation may hide the project altogether. In an urban environment, a building may be screened by other buildings, reducing its visual impact.”

Another important aspect to consider is landscape integrity and sense of place: this refers to the compatibility of the development within the landscape. If a new building is proposed in an urban environment, the impact on the viewer or receiver is minimal – as the building is congruent with the existing landscape.

“However, this is not the case if a mine is constructed in a pristine natural environment,” said Heyns, “or an intrusive development is being considered in scenic winelands.”

Fully assessing visual impact is not a purely objective task, she said, as different viewers (or ‘receptors’) will experience the same landscape in different ways. While farmland, for example, may be seen by some as simply a place to grow crops, others may value the aesthetic sense of place and be less predisposed to a new development.

Understanding the sensitivity of the receptors is therefore vital to every VIA, especially as South Africa strives to attract more tourists. “Tourists are often more sensitive to the visual landscape, so we need to take this into account especially in provinces that are reliant on their tourism sectors,” she said.

Once sensitive receptors – which may include motorists on scenic roads, visitors to national parks and inhabitants of rural settlements – have been identified, 3D modeling and photo simulation are used to predict visibility of the development from key viewpoints and receptors in the project zone of influence.

Most new developments require night-time illumination, which in rural areas particularly creates an unwanted impact. “Light pollution can be significant in remote places, especially where no lighting is present prior to development,” said Heyns.

Once the main impacts are identified, the focus shifts to impact mitigation. “In the case of light pollution, for instance, down-lighting can be considered instead of more diffuse methods,” she said. “Service tracks and pathways in a rural setting can be directly lit with well-focused and covered luminaires, for instance, instead of lighting the whole area.”

As with most efforts to reduce environmental impacts, appointing visual consultants early in the project life-cycle is advantageous. SRK’s recent co-operation with architects designing a desalination plant on the Cape west coast was a good example.   “The plant – a fairly large-scale industrial complex – conflicted substantially with the area’s sense of place,” said Heyns, “but the architects were keen to keep visual impact to a minimum, so approached us for architectural guidelines to achieve this.”

This included ways to reduce the scale of the building, and fragmenting its design in keeping with the topography to make it less visible. Appropriate colours were recommended to blend in with the surroundings, as well as using a flat ‘green’ (planted) roof instead of a pitched structure.

“This early interaction is really beneficial, allowing early-stage consideration of a variety of innovative options,” she said. “Trying to mitigate the impacts of existing designs at a later stage is not nearly as effective.”

While there are currently no legal ‘triggers’ for VIA studies, there is no doubt that increased  stakeholder interest indevelopment is moving visual impact higher up the developer’s agenda and they are now routinely done for EIA studies.

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