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In August 1975, the Banqiao Dam and 61 others throughout Henan, China, collapsed following the landfall of Typhoon Nina.

The ensuing flood was among the deadliest floods in China, and was 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 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.

After renovations, the Banqiao dam was known as the "Iron Dam" to reflect its invincibility.

That same evening, Banqiao town, near the dam, started to flood. On August 7 at 21:30, the People's Liberation Army Unit 34450 (by name the 2nd Artillery Division in residence at Queshan county), which was deployed on the Banqiao Dam, sent the first dam failure warning via telegraph.

On August 8, at 01:00, water at Banqiao crested at 117.94 m above sea level, or 0.3 m higher than the wave protection wall on the dam, and it failed. The runoff of Banqiao Dam was 13,000 m3 per second in vs.

As the Boshan Dam, with a capacity of 400 million m3, crested and the water released from the failures of Banqiao and Shimantan was rushing downstream, air strikes were made against several other dams to protect the Suya Lake dam, already holding 1.2 billion m3 of water.

For example, while only 827 out of 6,000 people died in the evacuated community of Shahedian just below Banqiao Dam, half of a total of 36,000 people died in the unevacuated Wencheng commune of Suipin County next to Shahedian, and the Daowencheng Commune was wiped from the map, killing all 9,600 citizens. In the 1980s, several representatives of the Chinese People's Political Consultative Conference including Qiao Peixin (乔培新), Sun Yueqi (孙越崎), Lin Hua (林华), Qian Jiaju (千家驹), Wang Xingrang (王兴让), Lei Tianjue (雷天觉), Xu Chi (徐驰) and Lu Qinkan (陆钦侃) revealed that the death toll of the 1975 Banqiao Dam failure was 230,000. Interestingly, Luo ChengZheng (骆承政), one of the authors of the book, wrote "85,600 people died in the Banqiao Dam failure in 1975" in one edition of the book. In 2005, the Discovery Channel show Ultimate 10 rated the Banqiao Dam failure as the greatest technological catastrophe in the world, beating the Chernobyl nuclear disaster in the Soviet Union.

People's Daily has maintained that the dam was designed to survive a once-in-1000-years flood (300 mm of rainfall per day) but a once-in-2000-years flood occurred in August 1975, following the collision of Typhoon Nina and a cold front.

Quick Facts

• 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.
• Interestingly, Luo ChengZheng (骆承政), one of the authors of the book, wrote "85,600 people died in the Banqiao Dam failure in 1975" in one edition of the book.
• On August 7 at 21:30, the People's Liberation Army Unit 34450 (by name the 2nd Artillery Division in residence at Queshan county), which was deployed on the Banqiao Dam, sent the first dam failure warning via telegraph.
• The dam failure took place in the context of the Cultural Revolution.
• 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.

Source material: Wikipedia - "1975 Banqiao Dam failure". Adapted and summarized for DiscoverScroll. Original contributors are credited through the linked Wikipedia article. Read original on Wikipedia. CC BY-SA 4.0. Changes were made from the original.