Spatiotemporal Distribution of Ancient Stone Bridges in Wuxi, China and Their Relationship with the Natural Environment

As a significant component of hydraulic cultural heritage within the Grand Canal Cultural Belt, ancient stone bridges serve as vital physical evidence reflecting the evolutionary patterns of water conservancy and settlement spaces in Wuxi. Consequently, understanding their distribution holds critical significance for the holistic protection and revitalized utilization of the heritage. This study investigates 118 ancient stone bridges in Wuxi, China, employing ArcGIS spatial analysis methods, specifically average nearest neighbor, kernel density estimation, and standard deviational ellipse, to examine spatiotemporal characteristics. Additionally, a random forest (RF) model is utilized to quantify the importance of natural environmental factors influencing their distribution. The results reveal the following: (1) Temporally, the distribution transitioned from a random pattern in the Song Dynasty to a highly clustered pattern during the Ming, Qing, and Republic of China periods. (2) Spatially, the distribution centroid exhibited a distinct southwestward trend, evolving from a dispersed structure into a multi nuclei aggregation model centered on Yixing and Wuxi City. (3) Environmentally, bridges are predominantly located in low-elevation plains, gentle slopes (2° to 5°), and stable zones far from geological hazards. They exhibit a preference for northeast and northwest aspects, with the highest concentration within 100 m of rivers and in paddy or yellow–brown soil regions. (4) The RF model identifies rivers as the absolute dominant factor, followed by aspect, geological hazards, slope, and elevation, while soil factors have the lowest importance. These findings enrich the conservation theory for hydraulic cultural heritage and provide a scientific basis for the risk assessment, hierarchical protection, and integrated tourism planning of ancient stone bridges.