Urban expansion and wetland shrinkage estimation using QGIS- tool: A Kolkata Case-Study

¹ Department of Mechanical Engineering, Institute of Engineering and Management (IEM)
² Center of Excellence – Climate Change Research University of Engineering and Management, Kolkata, West Bengal, India

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Published online: 29 May 2026

Abstract

Urban wetlands are important natural reservoirs that help to regulate water cycles, weather and the environment at large in rapidly growing cities. Unfortunately, the fast pace of urban growth has led to the loss of many of these natural habitats. The paper explores spatial and temporal changes in the wetland areas of Kolkata through a GIS-NDWI method combined with forecast analysis. Different year satellite images were used in QGIS software to track water bodies in four different type so fur ban areas of Burrabazar (Urban Core), Salt Lake (planned city), Newtown (expansion zone), and the overall metropolitan area of Kolkata. The findings show that all the spatial levels there has been a slowly and continuously decrease in wetland areas. Overall, in the city, the water bodies have decreased from 2854.01km² or 7.82% in the year 2014 to 1834.02km² or 5.03% in 2023. A close-up focus shows that the water bodies in the urban core have practically disappeared, the planned urban areas (Saltlake) show a moderate level of water bodies 1.74% compared to urban core (Burrabazar) 0.98%, the expansion areas (Newtown) are being swiftly deprived of water bodies 1.93%. The projected data shows with that the current pace of urbanization, the remaining water bodies will become separated and would fail to function hydro logically. Findings indicate a severe imbalance between the growth urban areas and ecological sustainability, and point out that wetland-sensitive urban planning, continuously geospatial monitoring and policy-oriented conservation strategies are very necessary to prevent permanent environmental loss. The research was verified by linear regression and polynomial regression (degree = 2) which estimated that in 2030 only 3.25% of wetland will be left in Kolkata and by 2040 it would have reached a saturation level.