Spatio-temporal patterns of urbanization in the Kolkata Urban Agglomeration: A dynamic spatial territory-based approach

Abstract This study analyzes the spatio-temporal patterns of urban growth for the Kolkata Urban Agglomeration (KUA) in eastern India using dynamic spatial territorial extents and compares the results with existing popular hypotheses of urbanization patterns (diffusion-coalescence and three-growth-mode). Time series neighborhood-level built-up densities were extracted and overlain to identify two broad urban spatial extents, inner and outer, which were further categorized into sub-territorial units. Landscape metrics and mode-wise urban growth statistics were computed for the above spatial extents. Results reveal a marked increase in the urban land share, from 20 % in 2000 to nearly 50 % in 2018, when about 75 % of the built-up spaces comprised the high-density urban core. Urban growth patterns in KUA show clear intra-urban variations between inner and outer spatial extents. The inner city zone underwent coalescence with nearly 90 % of the built-up growth within inner city extents occurring through infilling, whereas the outer extents showed complex growth patterns with outlying growth dropping by almost 27 % points, with related increase in both infilling (11 % points) and edge-expansion (16 % points). Diffusion and coalescence occurred simultaneously, but at varying intensities within the different sub-territorial units. Examining such complex spatiality of urbanization is crucial to reduce its adverse environmental effects and promote sustainable urban growth.