Banqiao Dam Failure (1975): China's Typhoon Nina Dam Catastrophe

The Banqiao Dam failure took place on the night of 7–8 August 1975, when extraordinary rains from Typhoon Nina caused the Banqiao and Shimantan reservoirs in Henan Province, China, to burst. A wall of water swept down the river valleys, and dozens of smaller dams collapsed in turn. The disaster is considered one of the deadliest dam failures in history, but it was kept largely secret for two decades, and its death toll remains disputed.

Background: the dams of the Huai River basin

The Huai River basin in central China has suffered devastating floods for centuries, including the great China floods of 1931. After the Communist victory in 1949, Mao Zedong’s government launched a campaign to “harness the Huai River” by building reservoirs and embankments.

The Banqiao Dam on the Ru River, a tributary of the Huai, was built in the early 1950s with Soviet technical advice and later enlarged. The Shimantan Dam was built on the nearby Hong River. Both were earth dams, designed to control floods and store water for farming.

During the Great Leap Forward from 1958, many more small dams were built in the region, often quickly and with limited engineering review. Accounts later published in China say that the hydrologist Chen Xing had warned that some reservoirs were being built with too little capacity to release water safely, and that his advice was overruled.

Typhoon Nina

Typhoon Nina crossed Taiwan and landed in Fujian, on mainland China, in early August 1975. It weakened as it moved inland, but its remnants met a cold front and stalled over southern Henan.

From 5 to 8 August, torrential rain fell. A rain gauge at Linzhuang recorded more than 1,600 millimetres in about three days, including over 1,000 millimetres in 24 hours. That was more than the area normally received in a year. Communication lines were damaged, and the dams’ managers struggled to report conditions or receive orders.

The collapse

As reservoirs filled, operators opened the sluice gates, but they could not release water fast enough. Some gates were reported to be blocked by silt or debris. The Shimantan Dam was overtopped and failed shortly after midnight on 8 August.

About half an hour later, around 1 a.m., the Banqiao Dam collapsed. Its reservoir released several hundred million cubic metres of water, often estimated at roughly 600 to 700 million cubic metres. A flood wave several metres high rushed down the Ru River valley, sweeping away villages, farms and railway lines.

The surge overwhelmed smaller dams downstream. According to commonly cited accounts, about 62 dams failed in total. Large areas of Zhumadian prefecture and neighbouring districts became a vast lake, and some survivors were trapped on rooftops, embankments and trees for days.

Why the flood was so deadly

The Banqiao and Shimantan dams had been designed for floods that engineers expected to occur very rarely, but Typhoon Nina’s rainfall exceeded those design assumptions by a wide margin. Once the reservoirs filled, there was no safe way to release the extra water.

The failures came in the middle of the night, when most people were asleep. Rain had already flooded fields and roads, and power and telephone lines were down, so warnings could not be passed quickly to villages downstream. Some accounts say that requests to release more water or to breach embankments were delayed by poor communications.

The landscape made matters worse. The plains below the dams were flat and densely farmed, with many villages built close to rivers. Once the water escaped, it spread across a vast area and stayed for days, cutting off survivors from food and clean water. Disease and hunger in the following weeks are thought to have caused many of the deaths.

Survivors’ accounts published later describe people tying themselves to trees, floating on doors and roof beams, and waiting days for boats or air-dropped food. Some of the stranded were swept away when weakened embankments gave way, and rescuers struggled to reach scattered villages across the flooded plain.

Death toll and aftermath

The number of deaths is one of the most contested aspects of the disaster. Figures based on Chinese official sources give about 26,000 deaths directly from the flooding. Other widely cited estimates suggest around 85,000 flood deaths and a further 145,000 deaths from disease and famine in the weeks after, making a total of about 230,000. Most historians give a range rather than a single figure.

Millions of people were affected. Roads, railways and communications were cut, crops were destroyed and wells contaminated. The army and militia carried out rescues and air-dropped food, and some flood water was deliberately released by blasting embankments to protect other areas.

Secrecy

The disaster occurred during the last years of the Cultural Revolution, when news of disasters was tightly controlled. Little was reported in the Chinese press, and the outside world learned few details.

Information began to emerge in the 1990s. A chapter in the collection The River Dragon Has Come!, edited by journalist Dai Qing and published in English in 1998, described the failure in detail as part of a debate over the Three Gorges Dam. In 2005 more official material was released in China, and the disaster became more widely known.

Lessons for dam safety

Engineers have studied Banqiao as a case of what can go wrong when dams are designed for floods that are too small. Lessons included the need for larger spillways, reliable communications, better rainfall forecasting and careful review of how failures of one dam can trigger others downstream.

The Banqiao Dam was rebuilt between the mid-1980s and early 1990s with a much greater capacity to release flood water. China also invested heavily in reservoir safety inspections and repairs in later decades, though the safety of older small dams remains a concern.

Myths and facts

Accounts of Banqiao online sometimes present the highest estimates as certain fact. In reality, the true death toll is unknown, and historians give ranges. Another common claim is that the main dam was simply badly built. It was a substantial earth structure for its time; the core problem was that its spillway and gates could not cope with such extreme rain.

By the numbers

Timeline

• 1951–1952: Banqiao Dam built on the Ru River as part of the Huai River programme.
• 1958 onward: Many small reservoirs built in the region during the Great Leap Forward.
• 1975, early August: Typhoon Nina crosses Taiwan and makes landfall in Fujian.
• 1975, 5–7 August: Extreme rainfall over southern Henan.
• 1975, 8 August, after midnight: Shimantan Dam fails.
• 1975, 8 August, about 1 a.m.: Banqiao Dam collapses; dozens of other dams fail.
• 1990s: Details of the disaster are published by Chinese writers and researchers.
• 2005: Further official records are made public.

Why it matters

The Banqiao Dam failure was among the worst infrastructure disasters of the twentieth century. It showed how extreme weather, rushed engineering and political secrecy can combine to cause enormous loss of life, and it remains a key warning in debates about large dams around the world.