River Cooling Distances of the Xiang River in Hengyang: Spatiotemporal Evolution and Associated Factors Based on LCZ

Abstract

Rapid urbanization has intensified the urban heat island (UHI) effect, yet the river cooling distance and its associated influencing factors remain poorly understood. We retrieved Land Surface Temperature (LST) from Landsat imagery and mapped Local Climate Zones (LCZs) using the Random Forest algorithm. By integrating multi-ring buffer analysis with the Geodetector model, we quantified the river cooling distance across different LCZ types along the urban reach of the Xiang River in Hengyang City. Our results indicated that: (1) surface thermal conditions exhibited marked cross-LCZ thermal contrasts among the three summer acquisitions, with the most prominent warming anomalies found in LCZ 3, 7, 8, and 10; (2) the river cooling distances of built-up LCZs were 820 m (2011), 970 m (2018), and 780 m (2025), all falling within the 750–1000 m range; (3) the primary spatially influencing factors shifted from built-up intensity (NDBI) to nighttime light (NTL) and population density (POP). The distance factor alone showed weak explanatory power (q < 0.05) but exhibited strong synergistic interactions when combined with other factors. These findings suggest that future waterfront planning should maintain a core cooling protection zone while reducing anthropogenic heat sources in built-up areas, thereby enhancing the overall cooling benefits of river cold sources.