Urban Growth and Landscape Change in Three Bangladesh Cities: Dhaka, Chattogram, and Sylhet

Abstract

Abstract Bangladesh is one of the fastest-growing developing countries in the world, experiencing rapid unplanned and haphazard urbanization. This unplanned development leads to environmental degradation, threatening ecosystems and human well-being. Planned urbanization is vital in reducing ecosystem stress and ensuring sustainable urban development. An intensive study of the urbanization patterns over the last 20 years will aid in future development planning to ensure a better living environment. Our study examines the urbanization trend over the last two decades in Bangladesh's three main cities: Dhaka, Chattogram (previously called Chittagong), and Sylhet. The study compares each city's growth within its present municipal boundary and surrounding periphery buffer area. The municipal authority designates this buffer area as the future city expansion area. These three cities' land surfaces were classified using Landsat 5 and Landsat 8 satellite data (spatial resolution: 30m) on the Google Earth Engine (GEE) cloud computing platform. Using a three-year composite image, a pixel-based Random Forest (RF) supervised classification was used for land use classification, achieving an overall accuracy of over 94%. In 2021, the core city area of Dhaka was 47% built-up, Chattogram was 37%, and Sylhet was 49%. Comparatively, the cities' proposed future expansion area is less built-up, with impervious areas covering only 18% in Dhaka, 13% in Chattogram, and 19% in Sylhet. Over the last two decades, Dhaka experienced the most significant change (65%) across all the land use types, with Sylhet second at 52% change and Chattogram at 48%. Following this trend, municipal authorities can preplan for accommodating the increased urban population in a sustainable manner, parallelly reducing the adverse impacts of unplanned city growth.