Introducing Visual Impact Assessment (VIA) - A recent Case Study....
We were recently approached to undertake an emergency Visual Impact Assessment (VIA) for the construction of a power line leading to the new Mbombela Stadium in Nelspruit. The reason for this being an emergency was that the construction of the line was already underway and vegetation clearing had already taken place! The alignment taken was as per the record of decision issued by the environmental authority... however there had been a critical oversight....
The alignment discussed with Interested and Affected Parties by the EIA consultant had indicated that the line would run behind the viewshed and not impact on them visually. This had been acceptable to all parties and this was supposedly captured in the Environmental Authorisation. To cut a long story – the final map indicating the alignment of the power line did not show contours and had the power line placed in the incorrect position – in front of the viewshed. It was an honest error, but unfortunately it remained unnoticed. This same map was then presented to the engineers to design and manufacture the structures.
Over a year later the structures had been manufactured and were taken to site. Simultaneously bush clearing commenced. Everything had to happen quickly as power needed to be delivered to the stadium within 2 weeks of the commencement of construction as there were matches and events scheduled. It was at this point that Interested and Affected parties noticed that something was badly amiss!
Their view of pristine bushveld hillside was suddenly about to be altered by a series of large 20m high pylons! What was going on – Surely this was in contradiction to the findings and conclusion of the EIA process?!
The original consultants responsible for the EIA were called in to deal with the matter. The possibility of rerouting the power line to the position behind the viewshed was discussed.
- How much difference would this make?
- Would it still be visible?
- In fact, what was the visual impact of the current alignment likely to be? Would it really be an unacceptable eye-sore?
It is not really possible to adequately answer these questions with words...
V&L were appointed to conduct a Visual Impact Assessment (VIA) for the proposed structures. Using GIS software we developed a detailed terrain model and imported the proposed power line and structures into the model. We were then able to perform accurate line of site queries to determine exactly what could be seen from any given point. 3D photographic representations were also undertaken to provide a clear visual representation.
This allowed us to quite clearly define the Visual Impact of the power line and the proposed alternative. It also provided us with detailed information on the height and placement of screening barriers that would be required should the client need to utilise the existing alignment.
Based on the fact that the structures had already been built and that it would not be possible to supply power to the stadium in time if new structures first had to be built, it was decided that best option would be to continue with the project and mitigate for the impacts created.
Building on the findings of the VIA we were able to develop a proposal for the planting of specific trees at given locations to screen the visual impact. Indigenous trees with a fast growth rate were preferred.
Photo modelling was again utilised to present a 1, 5, 10 year representation of the proposed mitigation.
VIA proved to be the critical tool required for decision making in this instance.
Given the critical need for the power line and the lack of time available to remanufacture structures for an alternative alignment, it was agreed that the power line should follow the proposed route and that impacts should be mitigated at substantial cost to the client according to the proposed visual plan.
Key Lessons learnt:- Visual representation and modelling of proposed development should not be underestimated during the EIA process.
- 2D mapping of 3d structures is misleading and can lead to later conflicts.
- VIA as a planning tool during the design stages could significantly reduce misunderstanding and risks later in the project.
- VIA is a valuable tool in conflict resolution when discussing visual intrusions.
The use of computer modelling and GIS allows VIA to be tailored to suit the application and the available budget. V&L has undertaken high budget projects where comprehensive 3D modelling is required. While often more attractive, it is not always cost effective to create a full 3D model of all structures. For more simplistic projects, with small budgets VIA work can be undertaken purely using a derived terrain model and by making informed assumptions regarding vegetation height and surrounding structures.
