Measuring magnitude of change by high-rise buildings in visual amenity conflicts in Brisbane

Abstract

Development conflicts signal underlying forces, challenges and processes in the evolution of urban environments. The review of 13 years of Planning and Environment Court cases in Brisbane revealed a high occurrence of visual amenity issues related to bulk, height and scale of high-rise buildings in medium and high-density areas. In these conflicts, justification of building height, bulk and visual relationships are mixed with expert witness personal judgments due to inefficiencies of conventional photomontage simulations and lack of scientific and measurable methods to assess visual impacts. A quantitative approach offers a new method for the evaluation of new building heights in the existing context. Using this method, the extent of visibility of a public vantage viewpoint is modelled in 3D and projected in a 2D graph by calculating sightline vertical and horizontal angles and distances. The projected 2D graph provides a basis to quantify visual impacts that can be experienced in a 360-degree context and 124-degree field of views. The extent of change is calculated based on the area of visible built form in an unwrapped plot of the surrounding skyline. The proposed method provides a measurable tool to increase the certainty and reliability of expert judgments in assessing visual impacts resulting from planned high-rise buildings.