Geospatial analysis of urban heat Islands and heat vulnerability in Chattogram, Bangladesh: implications for public health risks

Rapid urbanization and land use change are intensifying the Urban Heat Island (UHI) effect and its associated health risks. It is the most common problem in the cities across the Global South. Chattogram the second-largest city in Bangladesh that has highly urbanized and experiencing transformation of croplands and vegetation into impervious surfaces. The changes contribute to the increase in the surface temperature and vulnerability of urban residents. This study aims to determine spatiotemporal patterns of UHI between 2011 and 2024 and the Heat Vulnerability Index (HVI) for 2024 and its associated health risk of Chattogram District. The HVI was developed using eighteen geospatial, demographic, and socioeconomic indicators grouped under exposure, sensitivity, and adaptive capacity. For weighting and normalizing variables, Principal Component Analysis (PCA) was used, and for spatial statistics Global Moran’s I, Local Moran’s I, and Getis-Ord Gi were used to detect clustering patterns of heat risk. Results indicate that the average Land Surface Temperature (LST) rose by 1.8° C during the study period, and hotspots were concentrated in middle Thanas of Sadarghat, Kotwali, and Double Mooring. The HVI map shows that the vulnerability is very low at 94.4% although very high vulnerability is only 0.8% and is concentrated in the urban core. These findings highlight differential exposure to heat stress in Chattogram and need to incorporate vulnerability assessment into urban planning to inform climate adaptation and reduce possible public health effects in fast-growing cities.