Capturing open space fragmentation in high-density cities: Towards sustainable open space planning

Urban studies attempt to assess open space fragmentation and develop sustainable policies in high-density cities. However, the complex characteristics of open space fragmentation and the multiple scenarios comprising various fragmentation forms have not been adequately documented, potentially leading to irrelevant control strategies and controversial results. Therefore, this study aims to propose a systematic procedure for elaborating the patterns, forms and scenarios of open space fragmentation in Hong Kong's built-up area. The series of metrics proposed to capture the complex relationships among various fragmentation forms has been validated by principal components analysis for its wide application in open space fragmentation research. The results reveal that open space fragmentation takes the form of morphological (use, internal, extensive and shape) and connectional (location) fragmentation, which covers nine scenarios. Open space fragmentation shows spatial heterogeneity, as evidenced by the highest fragmentation index of 0.259 in the Kowloon region, followed by the Hong Kong Island and the New Territories regions with fragmentation indexes of 0.237 and 0.187. The average value of open space fragmentation in the old towns is 0.250, which is considerably higher than that of 0.187 in the new towns. Old towns manifest numerously more and complicated scenarios than new towns. The findings inform refined open space management in high-density cities.