Visual Impact Analysis
The Visual Impact Assessment (VIA) describes the appearance of changes in the landscape caused by proposed wind farm development. Unlike with noise or shadow flicker, there are no formulas to determine the impact or set limits. Instead, the study addresses the potential viewers that could be affected demonstrating if they would be affected, and if so what it would mean.Viewers may include commuters who see the wind park from a road, local residents, but also tourists that may be concerned with their treasured views. In addition, the VIA is assessing how the wind park develoment blends into the overall landscape.
Visual impact studies may provide
- observations on the tubine layout,
- maps of zones of visual influence (ZVI),
- photo montages, and
- 2D or 3D animations
To demonstrate the various parts, we have conjured up a ficticious power plant development with 2 rows of 6 wind turbines. One row consists of 3MW turbines, the other of 1MW turbines with smaller rotors. Hub heights are roughly the same. As can seen on the map, the 3MW turbines are spaced 450m from each other. The others only 250m.
In a photo montage a picture is taken from a certain view point, which could be a house or a road or any other visually sensitive point. We can then show the status quo as well as the photo with the turbines superimposed.
Here, the turbines from both rows are clearly visible. Due to the distance of the smaller turbines from the view point, that row adds an entirely separate visual impact.
Zones of Visual Influence
In a "Zones of Visual Influence" - map, we can show how many turbines would be visible from which point.
In this instance, up to 12 turbines could be theoretically visible. This is theoretical, as vegetation or buildings were not taken into account.
In most instances, either no turbine or all of them are visible. However, especially in the high-impact zone (within a 4km radius), some turbines will be hidden from views.
This is a typcial result of a wind farm built in mountainous regions where hills and mountain ranges obstruct the views further away.
Although a ZVI can show whether the wind farm or parts thereof would be visible, it can not show how tall the wind generators will appear in people's views. It is generally accepted that the impact of wind parks that are further away than 30km will be negligible, as the human eye will not register them in the field of view from that distance. The perceptibility of a wind farm is not just affected by distance, but also by the angle of the light, the contrast, visibility and the movement of the blades.