Keywords: 
• middle and lower reaches of Yangtze River /
• flood control system /
• Three Gorges Project /
• relationship between rivers and lakes

Abstract: The completion of the Three Gorges Dam project would result in significant improvements in the flood control of the middle and lower reaches of the Yangtze River. However, additional flood control measures would be needed to address population and economic growth along with a more prominent role of reservoirs in attenuating floods. These measures were addressed herein by considering scenarios post dam construction, and using as input the historic and extremely large floods of 1954 and 1998. The locations of the storage areas and flows between the rivers and lakes within the basin were considered along with other key factors affecting flood control. In addition, new issues were considered, such as chemical runoff, sediment transport and subsequent river evolution, reservoir regulation, and alteration of the probability of flood storage. The results showed that the construction of the Three Gorges Dam would improve flood control for the 100-year and more frequent event. However, the results showed that flood controls would not greatly affect the flooding resulting from larger flood. It was also observed that the flood risk was transferred to the reservoirs (or lakes). Therefore, to mitigate flooding from extremely large floods, more effort needs to be put on increasing flood control measures in the reservoirs using both structural and non-structural approaches.