Wind Turbine Visibility and Visual Impact Threshold Distances in ...

trails. It is reasonable and appropriate to analyze and describe potential visual impacts that
might be encountered routinely, even if they are small impacts.
3) Limit of casual visibility: This distance threshold determines the distance at which a
facility would likely be noticed by anyone looking briefly in the general direction of the
facility, without foreknowledge or active looking. In this study, the corresponding average
visibility rating is “3,” summarized as describing a facility that would be noticeable to a
casual observer. At this level of visibility, impacts may rise to a moderate level, depending
on circumstances and landscape context.
4) Limit of visual preeminence: This distance threshold determines the distance at which a
facility becomes a major focus of visual attention, tending to attract and hold visual
attention because of strong contrast in form, line, texture, color, or motion. In this study, the
corresponding average visibility rating is “5.” At this level of visibility, impacts are
generally at a high level, although the wind facility may not be visually dominant over
major landforms such as mountains, hence avoidance of the term “dominance” in the
threshold descriptor. In the authors’ opinion, despite the size of wind turbines and wind
facilities, the open nature of the turbine layout may make it difficult for a wind facility to
dominate views with prominent landforms, such as mountain ridges, because the wind
turbines lack “visual weight”; however, the strong line, color, and motion contrasts of wind
facilities may cause them to be major sources of visual contrast nonetheless, especially at
short distances.
These proposed thresholds are shown in Figure 12.
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