Trend of heat waves in Dhaka Metropolitan City and its impact on livelihood and health of exposed people

Abstract

The exponential growth in population and physical infrastructure since 1980 has imposed immense pressure on Dhaka Metropolitan City (DMC), triggering extensive urbanization and a surge in built-up areas. This urban expansion has intensified the urban heat island (UHI) effect (the phenomenon where urban areas experience significantly higher temperatures compared to surrounding areas), resulting in adverse global urban climate changes such as temperature spikes, erratic rainfall, and compromised air quality. This study aims to discern the heat wave trends in DMC from 1972 to 2020 and elucidate their impact on public health and livelihoods. Employing a blend of quantitative and qualitative methodologies, the research analysis of land surface temperatures (LST) and land cover indices reveals a significant increase in built-up areas, particularly in western and central parts of the city, correlating with higher LST. Satellite imagery (Landsat 5 and 8) with 30-m resolution and meteorological data indicate a rise in surface temperatures. Analysis reveals April, May, and June as the peak months for heat wave occurrences, with DMC enduring a total of 328 heat wave days according to heat index (a measurement of perceived temperature in human body indicating how hot it feels when relative temperature is added to the actual air temperature) classifications. Notably, the density of built-up areas, particularly in central and western regions, exacerbates the UHI effect, evident in rising surface temperatures reaching 40.1 °C in 2014. The study underscores the dire health hazards posed by heat waves, with vulnerable populations, such as slum dwellers and outdoor laborers, facing heightened risks. Despite widespread impacts, public awareness about heat waves remains deficient, as evidenced by respondents’ limited understanding of the term. These outcomes and prepared maps of the current research will be supportive for the local inhabitant, urban planner, and environmental resources management manager, national and international policy advisor, government and non-movement stakeholder, and researcher to observe the urban climate, trend of heat wave, and its impact on exposed people.