1975 Banqiao Dam failure

In August 1975, the Banqiao Dam and 61 others throughout Henan collapsed following the landfall of Typhoon Nina. The dam collapse created the third-deadliest flood in history which affected 12,000 km² (3 million acres) with a total population of 10.15 million, including around 30 cities and counties, with estimates of the death toll ranging from 26,000 to 240,000. The flood also caused the collapse of 5 million to 6.8 million houses. The dam failure took place in the context of the Cultural Revolution.

Many of the dams that collapsed were originally constructed with the help of Soviet advisors. Many were built during the Great Leap Forward. The construction of the dams focused heavily on the goal of retaining water and overlooked their capacities to prevent floods, while the quality of the dams was also compromised due to the Great Leap Forward. The Banqiao dam had been designed for a calculated one in a thousand year rainfall event of 300 mm per day; however, more than the normal yearly rainfall (1,060 mm) fell in just one day near the typhoon center. Some experts have also stated that the focus on peasant steel production during the Great Leap Forward, as well as a number of policies from the campaign to "Learn from Dazhai in agriculture", severely damaged the ecosystem and forest cover in the region, which was a major cause of the flood, and the government's mishandling of the dam failure contributed to its severity.

In the aftermath, various elements of the Chinese government concealed the details of the disaster until the 1990s, when the book The Great Floods in China's History (中国历史大洪水), prefaced by former Minister of Water Resources Qian Zhengying, revealed details of the disaster to the public for the first time. The official documents of the disaster were declassified in 2005 by the Chinese government. In May 2005, the Banqiao Dam failure was rated #1 in "The Ultimate 10 Technological Disasters" of the world by Discovery Channel, outranking the Chernobyl disaster.