Heatwave vulnerability of large metropolitans in Bangladesh: An evaluation

Heatwaves pose a significant risk to human society, and assessing vulnerability at the local scale is challenging due to the multifaceted nature of contributing factors. This study focuses on evaluating the heatwave vulnerability of five major cities in Bangladesh: Chittagong, Dhaka, Khulna, Rajshahi, and Sylhet. Heatwave vulnerability index (HVI) was estimated, integrating exposure, sensitivity, and adaptive capacity components. Time-series data from the Moderate Resolution Imaging Spectroradiometer (MODIS) for land surface temperature (LST) spanning 2000–2019 served as the primary dataset. The HVI calculation employed a principal component analysis method. The spatial distribution of the resulting HVI across five metropolitan areas were evaluated by estimating spatial autocorrelation and identifying clusters and hot spots in vulnerable areas. The findings revealed that urban centers characterized by extensive built-up areas exhibited higher exposure to urban heat compared to their surroundings. Dhaka, the capital, recorded the highest mean annual LST, while Sylhet registered the lowest. Rajshahi and Sylhet stood out for having the largest percentage of heat-exposed and sensitive areas, respectively. Sylhet also had the highest percentage of heat-vulnerable areas, reaching 63 %, whereas Dhaka had the highest number of vulnerable individuals, totaling 12.5 million. The findings also suggested that augmenting urban green and blue infrastructures holds potential for mitigating the adverse impacts of heatwaves. The methodology and outcomes of this study provide a valuable foundation for devising heatwave adaptation strategies not only in Bangladesh but also in other regions facing similar challenges.