Visual preference for treatment of bare land on hillside

Bare land is common on hillsides and may occur due to landslides, cultivated lands, or engineering construction sites. The purpose of this study is to analyze the visual preference of treatment of bare land on hillside. The treatment methods for bare land are classified into ecological engineering, non-ecological engineering, and natural recovery or vegetation. For this study, first, several images of areas in North Taiwan that experienced landslides or engineering construction were collected, including Daan and Shilin districts in Taipei city, Wugu, Shiding and Tamsui districts in New Taipei city, and Fuxing district in Taoyuan city. Then, Photoshop software was used for image processing and for calculation of percentage of vegetation cover on the bare land, i.e., the green looking ratio (GR). Furthermore, a questionnaire survey was conducted to investigate the visual preference (P) and the cognitive factor of an image associated with the GR. Three cognitive factors, consistency (C), vividness (V), and naturalness (N), were used for the survey. A total of 131 effective questionnaires were received from survey respondents and the Likert scale was used to rate the degree of visual preference and cognition. The rating values ranged from 1 to 5. The results show that a higher N, V, and C was preferred by viewers when the bare land was covered with vegetation or high GR. The factors C, V, N, and P for treatment of bare land using ecological engineering method are higher than those using non-ecological engineering. The adopted natural or flexible methods to treat bare land prompt visual preferences from viewers and can provide important references for landscape engineering design.