资源环境科技发展态势分析平台

This study introduces scientifically rigorous methods to visual impact assessment. Images of the existing condition are edited to simulate two alternatives at 22 key observation points (KOPs) along a proposed transmission line. Scenic value and visual contrast are assessed from the images by six independent evaluators. Photo validity and rating reliability are evaluated, and found acceptable. Procedures to measure cumulative and incremental visual impacts in a view are demonstrated. Both mean ratings and effect size are used to interpret the severity of visual impacts. The cumulative impact measured by contrast ratings is unreasonably adverse at many KOPs. The incremental visual impact measured by contrast ratings is less severe than the existing transmission line's visual impact, but still unreasonable at many KOPs. The incremental impact determined by the change in scenic value is less severe than indicated by visual contrast, but still identifies many unreasonable impacts. Burial of 84 km of the transmission line results in an improvement at the affected KOPs but unreasonable impacts remain at other locations. The exigencies of professional practice limit the number of evaluators however, scientific rigor requires a greater number of evaluators to establish mean ratings with reasonable levels of confidence. It is proposed that this may be an opportunity to involve the public. This is the first-time effect size has been used to interpret contrast ratings, and additional reports on its effectiveness are needed. It is hoped that professionals conducting visual impact assessments will employ these procedures and report them publicly.