Observed changes in hydrological extremes and flood disaster in Yangtze River Basin: spatial-temporal variability and climate change impacts

The variation and tendency of hydrological extremes in the context of climate change have received extensive concern. However, there is still no clear understanding toward the evolution of hydrological extremes, and the impacts of climate change on flood disaster and risk have been explored very poorly. This study investigated the trends in flood-related variables of extreme precipitation, extreme river flow (1955-2012), and flood damages (1990-2014) in Yangtze River Basin. To further explore the impacts of climate change, the relations of changes in extreme river flow and precipitation were evaluated using wavelet transform analysis, and the trends in normalized flood damages were re-examined with the elimination of changes in exposure. The results showed that flood damages decreased significantly in the middle and lower reaches, while extreme precipitation and river flow still had increasing trends, indicating the potential of increasing flood risk. For upper basin, extreme precipitation increased significantly in the west and northeast part, while significant decreasing trends can also be found in the central part. The wavelet analysis revealed significant covarying relations for extreme discharge and precipitation, demonstrating the substantial influence of climate variability on extreme river flow. Meanwhile, the normalized flood damages showed increasing trend in Sichuan province, indicating significant climate change impacts on flood disaster. This study suggests the need for more effective measures to mitigate flood risk and better adaptation for climate change in Yangtze River Basin, especially in the middle and lower basin and northeast of the upper basin.