Categorization of Green and Grey Infrastructure Complexity in the Rural-Urban Interface of Bengaluru, India; an unsupervised volumetric approach with relevance for urban quality

Abstract Trees are key elements of urban green infrastructure and provide multiple ecosystem services that are essential for the quality of life of people in an urban environment. Grey infrastructure is made up of buildings or built-up area, generally characterized by imperviousness of the surface. The complexity of urban green and grey infrastructure and their interactions co-define the quality of urban life and the ecological value. Using conventional dichotomies by separation into „urban“ and „rural“ contexts does hardly allow to comprehensively assess the situation in rapidly and often chaotically urbanizing environments of the Global South. We present an unsupervised remote sensing-based approach integrating 3D information as an approach to objectively categorize the complexity of green and grey infrastructure. For our study area in Bengaluru, India, we distinguished five categories describing composition and configuration of the green and grey infrastructure, where three variables served as indicators for categorization into five cluster. We argue that such integrated 3D assessment of green and grey infrastructure is particularly useful for understanding and classifying “rurban” environments, where a distinction between urban and rural is often no longer possible The final map allows to quantitatively characterize rurban configurations.