River system changes under urban expansion: Insights from the Suzhou-Wuxi-Changzhou metropolitan area, China

Study region: The Suzhou-Wuxi-Changzhou (SWC) metropolitan area, China. Study focus: Urban expansion is a natural product of growing cities at the expense of river systems. In this study, we evaluated river system changes that come with urban expansion on a grid scale. We also utilized the spatial analysis models to examine the impact of urban expansion on river system changes. New hydrological insights for the region: Our results indicate that the cities in the metropolitan area had a similar pattern of urban expansion from the 1960s to the 2010s, with Changzhou, Wuxi, and Suzhou losing 45.8%, 32.3%, and 42.2% of their rivers, respectively. A negative correlation was detected between the urban expansion area (UEA) and the river density variation (∆Rd). During the rapid urban expansion period, ∆Rd significantly decreased as UEA increased. We then identified the spatial dependence and spatial spillover effect between river system changes and urban expansion. In our analysis, the river density was degraded as a result of urban expansion both in the in-situ location and in the neighboring locations. The river system has seen significant changes due to the impervious areas and infrastructures caused by urban expansion; thus, an appropriate pattern of urban development is required to mitigate the negative effects of river loss.