Study on flood characteristics of the middle and lower reaches of the Yangtze River under climate change

Investigating the changing patterns of floods in the middle and lower reaches of the Yangtze River under climate change is crucial for flood management in this region. Using Global Climate Models (GCMs) and the Distributed Time-Variant Gain Hydrological Model (DTVGM), this study forecasts the flood response characteristics at key stations along the Yangtze River under future climate conditions. The results reveal a rising trend in runoff in the middle and lower reaches of the Yangtze under four Shared Socioeconomic Pathway (SSP) scenarios, particularly under the high-emission scenario SSP5-8.5, where seasonal hydrological variability becomes more pronounced and persistent. Across various climate scenarios and models, annual peak flood discharge and the maximum 3-day flood volume at Datong, Hankou, Luoshan, and Yichang stations exhibit an increasing trend. The occurrence of small, medium, large, and extremely large floods follows a decreasing pattern. Compared to the SSP3-7.0 and SSP5-8.5 scenarios, the SSP1-2.6 and SSP2-4.5 scenarios show a higher frequency of small floods and a lower frequency of large and extremely large floods. Under the SSP3-7.0 and SSP5-8.5 scenarios, the likelihood of large floods increases, exhibiting more concentrated and frequent occurrences, with a tendency toward extremeness. These findings provide a scientific basis for flood management planning in the middle and lower reaches of the Yangtze River.