Visual Impact

visual impact

Visual impact is the extent to which a project changes the appearance or view of landscapes and urban areas. The concept is a central issue in the environmental impact assessment (EIA) process. For example, in Europe, the EIA Directive stipulates that the aesthetic impact of a project should be considered during its design phase. In the United States, Federal regulations require that all projects involving Federal funds be subject to a visual impact analysis (VIA) in accordance with NEPA.

VIAs are often controversial, particularly for highway projects affecting scenic and natural resources. Highway agencies can help to resolve controversy by assessing and mitigating visual impacts, as well as engaging in public involvement to identify local values that could be affected.

Although the term “visual effects” (VFX) is often used to refer to special in-camera filming, this is a broad category that includes both live action and generated imagery. For example, the use of CG characters in a movie is a form of VFX that would typically be performed during post-production with the aid of animation and compositing software. Creating and incorporating such characters into the movie usually involves extensive planning and coordination between the director, producers, and the CG artists.

In NEPA, a visual impact analysis (VIA) is an important tool for evaluating the effect of a highway project on the surrounding landscape and community. The VIA must be conducted in accordance with the requirements of NEPA and other applicable laws, including a review of relevant State, regional, and local plans and policies, and consideration of Section 6(f) of the Land and Water Conservation Fund Act.

A VIA must also be conducted if the highway project is on or crosses public lands with cultural, historic, ecological, scenic, and wildlife resources. In addition, the VIA should consider other Federal laws that may impose restrictions on road construction or reconstruction in sensitive resource areas.

To determine the visual impact magnitude of a landscape change, a standard metric has been developed based on the perception of alterations inserted into largely natural landscapes devoid of conspicuous anthropic elements. The resulting index, Lvi (level of visual impact) has been shown to accurately reflect the degree of a landscape change in terms of its impact on surrounding natural scenes.

The chromatic color contrast between the existing and proposed visual conditions should be evaluated in the context of the aforementioned criteria. This comparison is often difficult, since digital images of a landscape are commonly represented in RGB format, which is not perceptually uniform. The use of a more perceptually uniform reference space, such as CIELAB, can improve the accuracy of this comparison by approximately a factor of 10 (Lucchese and Mitra 2001).

Before beginning a VIA, it is important to understand what laws, ordinances, or regulations may apply in the project area. Search local planning and policy documents for references to beauty, character, cultural or historic resources, glare, light, preserving the “dark skies,” parks and recreation, views, and vegetation. The results of this research should be included in the context section of the VIA document.