Why has the Three Gorges Dam's flood-control effectiveness been debated?

The effectiveness of the Three Gorges Dam as a flood-control tool has been a subject of significant debate since its inception. While a primary objective of the project was to protect millions of people from the Yangtze River’s periodic, catastrophic flooding, its actual performance remains contested.12

Arguments regarding its efficacy include:

• Support for Flood Control: Proponents and government officials have noted that the dam has successfully held back floodwaters during heavy rainy seasons, such as in 2010, thereby minimizing downstream impact.12
• Criticism and Limitations: Detractors argue that the dam’s capacity is limited. During severe events, such as the heavy floods of 2020, the reservoir neared maximum capacity, forcing officials to open floodgates. Critics assert that such events highlight the dam's inability to fully contain extreme water volumes.1
• Alternative Solutions: Some engineers have long argued that constructing smaller, less expensive, and less environmentally disruptive dams on the river's tributaries could have provided equivalent flood control and power generation without the risks associated with the massive Three Gorges structure.1
• Environmental and Structural Concerns: Critics also point to the potential for sediment buildup to raise reservoir levels, which could reduce the dam's ability to contain future floods.3