A clear picture of visual impact

Atmos Consulting is developing a computer model which attempts to makes sense of the complexity of understanding and predicting the cumulative visual impact of wind turbines. The aim is to attempt to model and display the intensity of visual impact arising from wind turbines in a format which can be more readily understood by planning authorities, statutory consultees and the general public.

The recent SNH guidance on ‘Assessing the Cumulative Impacts of Onshore Wind Energy Development’ recognises the expensive, time consuming nature of  assessing cumulative visual impact  and advises that the assessment should focus on the likely significant effects and, in particular, those which are likely to influence the outcome of the consenting process.

Not straightforward

However, identifying when a project is actually likely to have a significant cumulative impact is not straightforward. Atmos uses GIS (geographical information system) modelling techniques to map the intensity of cumulative wind farm visibility against built, consented or proposed turbines. The Atmos mapping methodology takes relative distance, size and perspective into account and the model produces colour coded illustrations highlighting the additional impact of a proposed new development. 

It is a welcome alternative to the present method of representing cumulative impact by a laborious series of illustrations of overlapping Zones of Theoretical Impact (ZTV) for each existing or proposed development. The result of the current process is often a mass of data and a considerable number of figures which can be very difficult to interpret. 

The Atmos model attempts to replace the simplistic approach, of showing the number of wind farms visible, with an analysis of the number of turbines, as it makes little sense to treat a single turbine as having the same visual impact as a large wind farm. The GIS programmers have also allowed for distance decay effects, relating visual intensity to distance using the latest thinking on fuzzy viewsheds.

“This is an exciting project that attempts to address a problem that developers, their advisors, planning authorities and statutory agencies have been grappling with for years,” said Atmos Consulting Director Fraser Mackenzie. “Our GIS team is continually at the forefront in developing new, innovative models that create cost and time efficiencies for our clients.”

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