An integrated analytical framework linking green and blue infrastructure spatial patterns with human thermal stress using UTCI

Abstract Urban heat stress poses an increasingly critical challenge in the context of climate change and rapid urbanization, prompting the adoption of Green-Blue Infrastructure (GBI) as a key mitigation strategy. Despite its recognized potential, previous studies have reported inconsistent findings regarding the relationship between GBI spatial configuration and urban thermal environments, primarily due to methodological variations and urban structural diversity. To address these limitations, this study proposes a quantitative analytical framework grounded in the Universal Thermal Climate Index (UTCI), which captures human-perceived thermal stress more effectively than traditional land surface temperature (LST)-based approaches. Employing data from the Seoul metropolitan area, the study identified 1,800 meters as the optimal spatial scale for capturing GBI-thermal relationships. Through correlation and multicollinearity analyses, seven landscape metrics were selected to characterize GBI morphology, including vegetation condition, spatial composition, configuration, and connectivity. These metrics included NDVI_mean (vegetation vitality), C_G_PLAND (proportional dominance of green infrastructure), C_G_SHAPE_AM and C_GB_SHAPE_AM (area-weighted shape complexity of green and green–blue patches), C_G_SPLIT and L_GB_PD (fragmentation intensity at class and landscape levels), and L_GB_COHESION (spatial connectivity and continuity of GBI). Subsequent application of a Random Forest Regression model revealed that C_G_PLAND, L_GB_COHESION, and NDVI_mean exert the greatest influence on UTCI variation. These findings suggest that the cooling capacity of urban GBI is determined not only by its extent but also by vegetation quality and spatial connectivity. The proposed framework enables consistent time-series analysis and provides a transferable approach for evaluating and optimizing climate-responsive GBI strategies across different urban contexts.