Remote sensing and geospatial technologies have emerged as essential tools for monitoring such changes due to their ability to provide consistent, multi-temporal, and large-scale observations. This study investigates the spatiotemporal dynamics of urban expansion in Kolkata Municipal Corporation (KMC) from 1990 to 2025 using multi-temporal Landsat data within a cloud-based geospatial framework. We extracted built-up areas using the Normalised Difference Built-up Index (NDBI) and analysed their temporal evolution through statistical methods, including linear regression, the Mann–Kendall trend test, and Sen’s slope estimator. The NDBI-based results indicate a substantial increase in built-up extent, with a clear transition from fragmented urban patches in 1990 to a more contiguous and intensified urban fabric by 2025. Quantitatively, built-up area increased from approximately 4,153 ha in 1990 to over 6,198 ha in 2025, reflecting sustained urban growth. Trend analysis confirms a statistically significant upward trend (Z = 3.75, P < 0.001), with Sen’s slope indicating an average annual expansion rate of ~47.65 ha/year, closely supported by regression results (~52 ha/year; R² = 0.48). Future projections based on Sen’s slope suggest continued expansion, potentially reaching ~9,772 ha by 2100 under a monotonic growth assumption. The integration of spatial (NDBI) and statistical (trend and regression) analyses demonstrates a consistent and robust pattern of urbanisation driven by long-term structural factors. However, the projected growth highlights potential challenges related to land resource pressure and environmental sustainability. The study provides a reliable methodological framework for assessing urban dynamics and offers critical insights for sustainable urban planning and policy formulation in rapidly expanding metropolitan regions.
Patra et al. (2026) studied this question.