Evolution of river network due to urbanization in the Southeast Yinzhou Plain of Yongjiang River Basin, China

River networks have important environmental, hydrological, and social functions. However, they have experienced rapid degradation due to urbanization, and the disorder of their flood, water pollution, and river functions has strengthened in many parts of the world. Previous studies have mainly described river networks using traditional indicators and have neglected the spatial non-stationary relationship with urbanization. Thus, in this study, a river network's evolution was revealed not only from the traditional perspectives of quantity and structure but also from the novel perspective of multifractal analysis. Furthermore, a Geographically Weighted Regression model (GWR) was created to detect the relationship with the urbanization in the 1990s–2020s on the Southeast Yinzhou Plain (SYP), China, in order to gain a deeper understanding of the complex irregular and self-similarity spatial components of the river network and reveal the main reasons for its degradation. The results revealed that under rapid urbanization, the river network quantity indicators, such as the drainage density and water surface ratio, decreased dramatically, especially for the low-order rivers. The indicators of the river network's structure, such as the connectivity, circularity, curvature, and box dimension, also exhibited decreasing trends. Even with all of the changes, the dense and relatively uniform spatial distribution of the river network pattern remained stable according to the capacity dimension detection. In general, the rapid urbanization had little effect on the evolution of the first-order tributaries, but as the urban land ratio growth increased, the drainage density of the second-order tributaries decreased at an accelerated rate. The spatial non-stationary relationship detection using the GWR also revealed significant correlations. The results of this study provide a solid guarantee for the recognition, protection, and restoration of the regional river network and the construction of a coordinated human-water society.