Assessing the impact of river changes on flood regulation capacity using a coupled flood model in an urbanized plain river network region

Abstract

Study region: The Changzhou Plain, the Taihu Lake Basin, Eastern China. Study focus: This study introduces an event-based approach for assessing the impact of river changes on flood regulation capacity in urbanized plain river network regions for the first time. The Changzhou Plain, river length decreasing by 7.55 %, was taken as an example to assess the effects of river changes on its flood regulation capacity from the 1980s to the 2020 s. New hydrological insights for the region: Two key indices, flood storage capacity (FSC) and remaining flood storage capacity (RFSC), were developed and calculated using a coupled flood model. Both the coefficient of determination (R2) and the Nash–Sutcliffe efficiency (NSE) exceeded 0.90 during model calibration and validation. The Changzhou Plain experienced river degradation from the 1980s to the 2020 s, with 11.14 % reduction in tributary river length and 3.05 % increase in main river length, leading to decreased water surface area and enhanced connectivity among main rivers. Regional FSC and RFSC increased by 8.42 % and 1.97 %, respectively, due to improved connectivity of main rivers from the 1980s to the 2020 s. The reduction in tributary rivers had minimal effects on FSC (increase of 1.62 %) and RFSC (decrease of 1.74 %), while improved connectivity of main rivers contributed to significant increases in both FSC (6.70 %) and RFSC (3.74 %). These findings underscore the effectiveness of enhancing river connectivity as a strategy to bolster flood prevention in the Taihu Plain, offering valuable insights for flood management and river planning.

Keywords

• River system
• Flood regulation capacity
• Flood event
• Coupled flood model