Characterizing compound floods from heavy rainfall and upstream-downstream extreme flow in middle Yangtze River from 1980 to 2020

摘要

The potential damages of flood would be magnified by the compounding effect of local heavy rainfall and extreme river flow from upstream/downstream, which has brought significant challenges to traditional flood risk management. To better understand the risk of these compound extreme events, we used the latest datasets to characterize compound inland floods in the middle Yangtze River region. The frequency, intensity, duration, timing, and dependence of the compound events from heavy rainfall in Wuhan and upstream-downstream floods in the Dongting Lake and Poyang Lake Basin were investigated from 1980 to 2020. In addition, we explored the effects of different compounding scenarios and discussed the synoptic and topographic conditions for these events. The results show that the frequency, intensity, and duration of all compound events had increased significantly after 2004; the occurrence time of most compound events had become more concentrated and advanced slightly in 2004-2020. Significantly positive correlation between extreme precipitation and corresponding upstream river flow and downstream water level were found, and the correlation became stronger in 2004-2020. The favorable synoptic and topographic conditions in this area make it prone to compound floods, and the influence from the concurrence with downstream flood was more profound than the concurrence with upstream flood. Higher risk of compound floods could be expected, given the increase in the drivers and their dependence in future, highlighting the necessity of more comprehensive study toward the mechanism, dynamics and risk of compound floods and more systematic strategies for flood risk management.