Evolution of coastal river network structure and changes in connectivity during urbanisation

Study region: Yong River Basin (YRB), a representative low-gradient coastal plain river system onthe east coast of China, is characterised by dense river networks and extensive hydraulic infrastructure.
Study focus: The spatio–temporal evolution of land use, river network structure, and connectivity of the river networks in low-gradient coastal plains, with a particular focus on the combined effects of urban expansion and sluice operations. New hydrological insights for the region: Urban land increased from 5.40% to 26.95% of the basin area over the study period, largely at the expense of agricultural land, with the most rapid growth occurring between 2000 and 2010. Although total river network length and density generally increased, localised channel losses and tributary fragmentation became more pronounced after 2010. Node betweenness centrality analysis highlighted that basin-wide connectivity depends on a limited number of key nodes concentrated along the Yong, Yao, and Fenghua Rivers. Connectivity analysis indicates that individual sluice closures exert both positive and negative effects on river network connectivity, while cumulative closures lead to a substantial reduction in overall
connectivity. These findings demonstrate that urbanisation reshapes river networks through land conversion and hydraulic infrastructure development, resulting in structural change and weakening of connectivity.