Urban heat typologies: impact of heatwaves on urban built environment and heat stress risk to the elderly in Darmstadt, Germany

Climate change has made heatwaves common during German summers. The phenomenon of urban heat islands (UHIs) only worsens the adverse effects of heatwaves, especially for the elderly, defined as population aged 65+ for this study. These issues need immediate attention and redress to avoid catastrophic consequences. For this research investigation, the city of Darmstadt in Germany has been mapped for heatwaves and UHIs. An assessment has been done to derive interrelationships between them and characteristics of the built environment. Rather than applying a generic Local Climate Zones classification, the built environment has been assessed by clustering the city of Darmstadt based on the UrbanReNet catalogue—a more contextual and nuanced urban typologies-based classification developed specifically for German cities. The findings of this study show that certain urban typologies are more prone to overheating, and can also significantly influence the thermal conditions of their surroundings. The latter is established by a novel multivariate regression that employs the H3 hierarchical geospatial indexing system. Further, mapping of the elderly in Darmstadt revealed that about half of them reside in settings that are at risk of overheating during a heatwave. This study provides a novel methodology to delineate areas at maximum risk of overheating. This can help prioritize heatproofing efforts to minimize the risk of excessive heat stress by focusing on the most vulnerable.