长江中下游叠加型洪灾未来变化及其驱动机制模拟研究

气候变化下的潜在洪灾风险加剧是国内外关注的热点，尤其是时间上频发和空间上并发的叠加型洪灾，将成为防灾减灾的重大挑战。现有水文模型存在尺度不匹配、区域大洪灾模拟可靠性差、叠加型洪灾系统风险考虑不足等缺陷，亟需厘清叠加型洪灾的形成和演变机制。本研究以长江中下游湘鄂赣皖四省为典型研究区，首先基于多个CMIP6模型生成长时序历史和未来气候数据，分析未来区域极端降水相对历史时期的多尺度变化特征。然后构建能够模拟下游水位顶托作用的CWatM—CaMa-Flood耦合模型，结合水文观测和多源遥感数据进行多目标参数优化，重现2016、2020年两次长江中下游洪水淹没过程。在此基础上，模拟未来多情景下叠加型洪水的灾害风险变化特征，识别防洪压力较大的热点地区，预估洪灾对社会经济的影响。最后探讨极端降水变化等对叠加型洪灾变化的影响。该研究将加深对未来洪灾风险特征的认识，为防灾减灾对策的制定提供科学支撑。

The potential increase in river flood risks under climate change has been a hot topic globally. The temporally-frequent and spatially-concurrent compound river floods pose a especially grave challenge for hazard prevention and mitigation in the future. The current large-scale process-based hydrological models often do not adequately account for compound river flood risks, have poor reliability in flood inundation simulations, and the scales of their research often do not match societal needs, therefore better understanding on the changing characteristics of future compound river floods and the associated mechanisms is urgently needed. This research focuses on the four provinces in the middle and lower reaches of Yangtze River: Hunan, Hubei, Jiangxi and Anhui. Firstly, multiple CMIP6 climate models will be extended with random weather generator to produce long time series for both historical and future periods, based on which the changes in precipitation characteristics will be analyzed at different scales. Secondly, the global hydrological model CWatM will be coupled with the global flood model CaMa-Flood and optimized with observed streamflow time series and inundation interpreted from multi-satellite images. This coupled model will be used to reproduce the inundation dynamics during the 2016 and 2020 large floods in the Middle and Lower Reaches of Yangtze, and to simulate changing characteristics of future compound river flood under different scenarios. Regions facing high pressure in flood defense will be identified, and the socioeconomics impacts of future floods will be quantified. Lastly, the effect of changing extreme precipitation etc. on the changing characteristics of future compound river flood will be analyzed. This research will deepen the understanding of future flood risk characteristics, and provide scientific support for hazard prevention and mitigation strategies.