Research on key technologies for graded response to exceeding-design floods of river basins

Exceeding-design floods of river basins are rare occurrences. Due to the combined influence of climate change and human activities such as water engineering operation, the evolving patterns and disaster-causing mechanisms of these floods are becoming increasingly complex. Such complexity leads to significant challenges in responding to these exceeding-design floods, such as the difficulty in monitoring catastrophic floods, low forecasting accuracy, insufficiently targeted early warnings, unclear regulation scheme for exceeding-design flood scheduling, and inadequate response capabilities of flood management systems to quick change of multi-scenarios. To address these issues, this paper, based on years of research and practical experiences, has re-defined the concepts of exceeding-design floods of river basins. A classification method for exceeding-design floods is proposed and applied in Changjiang River. Additionally, the flood warning and emergency response system, originally designed for standard floods, has been expanded to a "Four+3" leveled system specifically tailored for exceeding-design floods. Consequently, a multi-level dynamic progressive pre-warning system for exceeding-design floods based on coupling of hydrology and meteorology is established. These results contributed to research outcomes such as the "Guiding Principles for Preparing Defense Plans for Exceeding-Design Floods of River Basins". This study fills critical gaps in the full-chain of "monitoring-forecasting-warning-scheduling-responding" to deal with exceeding-design floods, bolstering the flood control safety measures in major river basins and providing technical support for the overall improvement of flood control safety in China.