Coordinated Spatial and Temporal Response of River Network Structure to Urbanization and Buffering Effects in Megacities: A Case Study of Chengdu City, China

With the rapid economic development and urbanization, the structure of urban river networks is undergoing profound changes. Therefore, there is an urgent need to study the changing law of river network structure in megacities and its coordination mechanism with urbanization. In this paper, three types of five indicators are selected to describe the temporal and spatial change characteristics of the river network structure, and the buffer coordination relationship between the river network structure and urbanization is analyzed by using the coupled coordination model, the center of gravity migration tool, and the degree of change index. The results showed that, in terms of temporal changes, the total length of river (L), river network density (Dr), and fractal dimension (D) showed a decreasing and then increasing trend between 2000 and 2020, and the water surface ratio showed an increasing trend, while the river development coefficient (Kp) showed a decreasing trend. The degree of urbanization continued to increase between 2000 and 2020. In terms of spatial change, the more rapidly urbanized the regions, the greater the index of the degree of change of river network indicators. The river network structure experienced a time-coordinated change of decline followed by recovery and a spatially coordinated change of the center of gravity of the river network structure migrating in the same direction as the center of gravity of urbanization. The study further reveals that the impact of river network structure on urbanization exhibits spatiotemporal buffering effects, which help mitigate the adverse impacts of urbanization. These coordination and buffering characteristics can provide strategic guidance for the planning of river network structures and the protection of water systems in future megacities.