Visual Impact Assessment
A Visual Impact Assessment does more than identify where visual effects may occur. Where potentially adverse effects are identified, the findings can help inform changes to the location, form, appearance or treatment of a proposal to reduce its visual impact.
In Brief
Visual impact can sometimes be reduced by avoiding the effect in the first place, refining the location or design of a proposal, reducing its visual prominence or introducing appropriate screening and other mitigation measures. The most suitable response depends on the project, the visual effect identified and the applicable planning or assessment requirements. After mitigation is considered, the visual effects that remain may be described as residual visual impacts.
Visual impact mitigation refers to measures used to avoid, reduce or manage potentially adverse visual effects associated with a proposed development.
The appropriate response depends on what the assessment identifies. A proposal that appears particularly prominent from a relevant viewpoint may require a different response from one where the primary issue is contrast with the surrounding visual environment.
Mitigation is therefore not a standard list of treatments applied at the end of every assessment. It should respond to the nature of the project, the receptors and viewpoints affected, the characteristics of the visual change and the applicable assessment framework.
Within a Visual Impact Assessment, mitigation can provide a connection between understanding a visual effect and considering how the proposal might respond to it.
Avoidance and mitigation are closely related, but they are not always the same response.
Avoidance seeks to prevent or remove a visual effect before it occurs. This might involve changing the location of part of a proposal, removing an element or reconsidering a design decision that creates the effect.
Mitigation generally seeks to reduce or manage an effect that cannot be completely avoided. Depending on the project, this might involve refining scale or form, reducing contrast, introducing screening or making other changes that alter how the proposal is experienced.
Where practicable, considering visual effects early in the design process can provide more opportunity to avoid or reduce impacts before the proposal becomes fixed.
Visual mitigation is most useful when it responds to the reason an impact occurs. The objective is not simply to hide a development, but to understand how its visual effect might be avoided or reduced.
Sometimes. Siting can influence how a development relates to relevant viewpoints, receptors and the surrounding visual environment.
Moving a building or infrastructure element may change its apparent prominence, relationship with existing features, degree of screening or the amount of the proposal visible from a particular location.
For larger projects, siting decisions may occur at several scales. The overall project location may already be established, while individual structures or elements may still be capable of refinement.
Whether relocation is practical or appropriate depends on the project and the other technical, environmental and planning constraints that also influence the design.
Where the scale or form of a proposal contributes to its visual effect, design refinement may provide an opportunity to reduce that effect.
Depending on the development, this could involve reconsidering height, massing, arrangement, orientation or the relationship between different components of the proposal.
The objective is not necessarily to make a development invisible. Instead, changes to form and scale may alter its apparent size, prominence or contrast within relevant views.
These design responses should be developed alongside the relevant architectural, engineering, urban design or landscape disciplines rather than treating the VIA as a substitute for those design processes.
Materials, colours and finishes can influence how strongly a development contrasts with its visual surroundings.
Depending on the project, matters such as colour, reflectivity, surface treatment and material variation may affect the prominence of built elements within a view. These characteristics can be particularly relevant where large surfaces or infrastructure elements are visible over distance.
There is no universal colour or material palette that minimises visual impact in every setting. A treatment that reduces contrast in one visual environment may be inappropriate in another.
Material and colour recommendations should therefore respond to the design, viewing conditions and surrounding context rather than being applied as a generic visual treatment.
Vegetation can sometimes provide effective visual screening, but it is not an automatic solution to visual impact.
Its effectiveness depends on matters such as location, species, height, density, maturity, seasonal characteristics, establishment time and the relationship between the vegetation, viewer and development.
Screening can also create its own effects. Vegetation introduced to obscure a development may alter an existing view, block valued outlooks or take considerable time to reach an effective size. These consequences should be considered rather than assuming that additional planting always improves the visual outcome.
Where landscape treatment forms part of the mitigation strategy, its detailed design and long-term performance may require input from an appropriately qualified landscape professional.
For some projects, mitigation may be considered closer to an affected receptor rather than solely at the development site.
Depending on the project and applicable requirements, this might include vegetation, landscape treatment or another screening measure intended to alter the view of the development from a particular location.
At-receiver measures require particular care because they can change the receptor's existing visual environment as well as screen the development. They may also depend on landowner agreement, available space, maintenance and the long-term effectiveness of the proposed treatment.
For that reason, screening should be assessed as a visual intervention in its own right rather than assumed to remove an impact simply because it blocks a line of sight.
No. Visibility and visual impact are not the same thing.
A development may remain visible after mitigation while its visual effect is reduced through changes to siting, apparent scale, form, contrast, screening or its relationship with the existing environment.
Conversely, attempting to conceal every part of a proposal can sometimes introduce additional visual change, particularly where extensive screening alters an existing outlook or landscape condition.
The distinction between the two concepts is explained further in Visibility vs Visual Impact: Why Being Visible Does Not Automatically Mean High Visual Impact.
Visual assessment can be particularly useful while a proposal still has capacity to change.
Assessment findings may identify the viewpoints, receptors or parts of a proposal that contribute most strongly to a visual effect. This can give the project team more specific information to consider when testing design responses.
Where alternative design options are available, visual evidence can also help compare how those options may change the visual outcome. Depending on the project, updated drawings, 3D information or photomontages may then be used to review a revised proposal.
The VIA informs this process by identifying and evaluating visual effects. The architectural, urban design, landscape or engineering response remains part of the wider project design process.
Mitigation does not necessarily remove every visual effect. The effect that remains after relevant mitigation measures have been taken into account may be described as the residual visual impact or residual visual effect.
For example, a design change might reduce the apparent scale or prominence of a proposal without removing it from the view entirely. The remaining visual change can then be considered within the applicable assessment methodology.
The way residual effects are described, rated or reported varies between assessment frameworks. It should not be assumed that every VIA uses the term in exactly the same way or follows the same sequence of assessment.
What matters is that the assessment distinguishes, where relevant, between the visual effects of the proposal and the effects that remain after the mitigation relied upon by the assessment is considered.
Potentially. Where mitigation changes the apparent scale, visible extent, prominence, contrast or other characteristics of the proposal, it may also change the nature or magnitude of the visual change being assessed.
The relationship is methodology-dependent. A VIA should therefore follow the applicable assessment framework rather than assume that a particular mitigation measure produces a predetermined change in magnitude or impact rating.
This is also why the effectiveness of mitigation should be considered in relation to the actual visual effect it is intended to address.
For more on this assessment concept, see What Is Magnitude of Visual Change in a Visual Impact Assessment?
Where appropriate, photomontages or other visualisations can help illustrate how a proposed design or mitigation measure may alter a view.
For example, visual material may allow an assessment to compare an existing view, the proposed development and a revised or mitigated design from the same location.
Where vegetation screening is relied upon, the visualisation should also avoid creating unrealistic expectations about its effectiveness, particularly where planting requires time to establish.
The role of visualisations is explained in When Are Photomontages Used in a Visual Impact Assessment?
For the reliability of that evidence, see What Makes a Photomontage Reliable for Visual Impact Assessment?
No. Visual mitigation needs to respond to the development and the visual effects identified for that project.
A measure used for large-scale infrastructure may have little relevance to an urban development. Similarly, a landscape treatment appropriate for one site may be ineffective or undesirable at another.
Some project types also have specific visual assessment guidance that establishes particular avoidance or mitigation expectations. Those requirements should not automatically be transferred to unrelated projects.
The appropriate strategy should therefore be based on the project, its planning context, the applicable methodology and the visual evidence produced through the assessment.
Mitigation is most meaningful when it follows from the visual evidence and assessment findings rather than being treated as a generic final step.
Understanding which receptors and viewpoints are affected, how the proposal changes the view and what contributes to that change can help identify where a design response may be effective.
The resulting response may involve avoidance, design refinement, screening or another project-specific measure. Where visual effects remain, those residual effects can then be considered within the relevant assessment framework.
In this way, a Visual Impact Assessment can contribute to design development as well as documenting the visual effects of the final proposal.
Continue Reading
Understanding the nature and extent of visual change helps explain why particular design or mitigation responses may be relevant to a proposal.
Understand magnitude of visual change →Visual Impact Assessment
Where visual effects are identified early enough, assessment findings can help the project team understand which parts of a proposal may benefit from further design consideration.
Send us your plans and available project information. We can review the proposal and help identify the appropriate visual assessment pathway.
Start Your Project