78 Boffa Miskell Ltd | Waihi North Project| Landscape and Visual Effects | When assessing the level of landscape effects, it is important to be clear about what factors have been considered when making professional judgements. This can include consideration of any benefits which result from a proposed development. Table 1 below helps to explain this process. The tabulating of effects is only intended to inform overall judgements. Contributing Factors Higher Lower Landscape (sensitivity) Susceptibility to change The landscape context has limited existing landscape detractors which make it highly vulnerable to the type of change resulting from the proposed development. The landscape context has many detractors and can easily accommodate the proposed development without undue consequences to landscape character. The value of the landscape The landscape includes important biophysical, sensory and shared and recognised attributes. The landscape requires protection as a matter of national importance (ONF/L). The landscape lacks any important biophysical, sensory or shared and recognised attributes. The landscape is of low or local importance. Magnitude of Change Size or scale Total loss or addition of key features or elements. Major changes in the key characteristics of the landscape, including significant aesthetic or perceptual elements. The majority of key features or elements are retained. Key characteristics of the landscape remain intact with limited aesthetic or perceptual change apparent. Geographical extent Wider landscape scale. Site scale, immediate setting. Duration and reversibility Permanent. Long term (over 10 years). Reversible. Short Term (0-5 years). Table 1: Determining the level of landscape effects Visual Effects To assess the visual effects of a proposed development on a landscape, a visual baseline must first be defined. The visual ‘baseline’ forms a technical exercise which identifies the area where the development may be visible, the potential viewing audience, and the key representative public viewpoints from which visual effects are assessed. Zone of Theoretical Visibility As an initial step in the visual analysis, a Zone of Theoretical Visibility (ZTV) mapping exercise was undertaken of the site in its context to determine the likely extent of visibility in the wider landscape. ZTV mapping represents the area that a development may theoretically be seen - that is, it may not actually be visible in reality due to localised screening from intervening vegetation, buildings or other structures. In addition, TV mapping does not convey the natureor magnitude of visual impacts, for example whether visibility will result in positive or negative effects and whether these will be significant ‘Zone of Theoretical Visibility’ (ZTV) is based on a Digital Terrain Model (DTM) overlaid on a map base. It is also known as a Zone of Visual Influence (ZVI), Visual Envelope Map (VEM) or Viewshed Map. The term ZTV is preferred for its emphasis of two key factors that are often misunderstood: Visibility maps represent where a development may be seen theoretically – that is, itmay not actually be visible in reality, for example due to localised screening from intervening vegetation, buildings or other structures which is not represented by the DTM; and the maps indicate potential visibility only – that is, the areas within which there may be a line of sight. They do not convey the nature or magnitude of visual impacts, forexample whether visibility will result in positive or negative effects and whether thesewill be significant or not. ZTVs are calculated by computer, using any one of a number of available software packages and based upon a DTM that represents topography. The resulting ZTV is usually produced as an overlay upon a base map, representing theoretical visibility within a definedstudy area. As the ZTV mapping is based entirely on ‘bare ground’ topographic data, it does not take into account the screening, unless LIDAR based vegetation data is used to generate the DTM. In addition, the level of reliability of the contour information will influence the accuracyof the mapping. ZTV mapping does however take into account factors relating to the curvature of the earth and light refraction. ZTV is helpful where to focus field work but it should be remembered that while ZTV is a useful assessment tool, is important to recognise itslimitations.
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