Spatiotemporal heterogeneity of temperature change and its dynamic response to river network system evolution in the South China

Rapid urbanization can lead to increased temperatures in urban areas and result in the compression and even encroachment of urban river network system. It is crucial to monitor the evolution of temperature and river networks under urbanization, identify existing risks, and implement preventive measures to mitigate potential disasters. This study investigated the temperature changes and the evolution of river network system in the Xiangjiang River Basin from 1986 to 2020 using meteorological station data and high-resolution remote sensing images. We aimed to analyze the spatiotemporal heterogeneity relationship between these factors and discuss their impacts on urban heat and flood risks. The results indicate that over the past 35 years, temperatures have shown an overall increasing trend, with the mean temperature, max temperature, and min temperature increasing at rates of 0.37 °C/10a, 0.38 °C/10a, and 0.43 °C/10a, respectively. The warming rate in major prefecture-level cities has been significantly faster than that in suburban areas. Human activities have significantly disrupted the river system, resulting in a 13.02% decrease in river density and a 14.21% reduction in the tributary development coefficient, simplifying the river network structure, the river network has changed from a longitudinal shortening of the length to a transverse compression of the width. The correlation between river network system indicators and temperature exhibits significant spatial heterogeneity. Rising temperatures raise heatwave risks, endangering urban health, while river degradation increases flood risks by reducing connectivity. These factors collectively undermine urban sustainability and resilience, and should therefore be a key focus in future urban planning. Study can provide support for research on urban green sustainable development and urban hydrological effects. It also offers new insights into controlling the increase in heat island intensity (HII) and improving urban resilience to climate change.