ANALYZING THE SPATIO-TEMPORAL DYNAMICS OF SURFACE WATER BODIES IN DHAKA CITY FROM 1988-2024

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Authors: Md. Marufur Rahman Tanzim Hayat Rabiul Awal B. M. Rabby Hossain

Keywords: Surface water bodies, Urbanization, Urban wetland, Dhaka, Bangladesh.

Journal: Journal of the Asiatic Society of Bangladesh (Science) - 52(1) - June 2026

Page Numbers: 61-79

Published At: June 2026

DOI: 10.64298/jasbsci.v52i.005

Abstract:

Rapid and largely unplanned urban growth has significantly altered the hydrological system of Dhaka, resulting in a substantial decline in surface water bodies. This study examines the spatio-temporal dynamics of surface water extent in the Dhaka Metropolitan Area (DMA) from 1988 to 2024, with the objectives of quantifying seasonal and long-term changes and identifying the key drivers of water body loss. Multi-temporal Landsat imagery was processed in Google Earth Engine using the Modified Normalized Difference Water Index (MNDWI) to extract surface water extent. Subsequent spatial analyses were conducted in ArcGIS. Land use and land cover (LULC) classification was performed using a supervised approach, while rainfall data were analyzed using Microsoft Excel and Python to assess hydro-climatic context. The results reveal a pronounced decline in surface water bodies over the study period. In the post-monsoon season, water extent decreased sharply from 121.89 km² in 1988 to 17.70 km² in 2024. LULC analysis further indicates a substantial reduction in water bodies (from 25.6% to 9.3%) and vegetation cover (from 51.6% to 25.8%), alongside a marked increase in built-up areas (from 22.7% to 64.9%). Visual analysis shows that the eastern and northwestern parts of the city have experienced the most significant loss of surface water. Although seasonal rainfall and flooding patterns contribute to short-term variability in water extent, the long-term trend demonstrates a decline that may be associated with rapid urban expansion, wetland encroachment, and landfilling. The loss of surface water bodies has critical environmental implications, including increased urban flooding and waterlogging, altered microclimatic conditions, intensified urban heat island effects, reduced groundwater recharge, and loss of biodiversity and ecosystem services. This study highlights the urgent need for integrated urban planning strategies that prioritize wetland conservation, regulate land use change, and promote sustainable water management to enhance urban resilience in Dhaka.