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Banqiao Dam Failure: The Worst Technological Disaster in History

Water has been the lifeline of human society for millennia. Not just because humans physically need it to survive, but because its existence allows people to use their ingenuity to create great things around it. From trade routes over the oceans, to aqueducts over the land, to irrigation systems near rivers – it’s incredible how many human innovations revolve around just water. But perhaps none is more impressive or diverse in its application than the dam.

Banqiao Dam Collaps
Banqiao Dam Collaps

The concept of a dam is simple enough: a wall to hold back water, usually in a river. Yet it goes further than that. Human society is built around rivers. The first large societies were formed around them, the most arable farmland is centered around them, they make trade easier, etc. And from the earliest times, humans have tried to shape rivers to better suit their needs. Dams are one of the ways in which they did this, with the earliest known dams existing in the Middle East and Mesopotamia for controlling the water levels of the Tigris and Euphrates from adverse weather.

As time has gone on, dams have become more sophisticated and have been built for increasingly specialized purposes, with the result being that dams come in more diverse shapes and sizes than perhaps any structure. There’s arch dams, gravity dams, arch-gravity dams, and so on. There are dams made of steel, dams made of stone, earth, timber, and more besides. They’re used for creating freshwater reservoirs, preventing soil erosion, controlling flooding, and since the 20th century, creating electricity. Dams are one of the most versatile human engineering projects on earth, and they are truly invaluable to human society.

With all that being said, dams have one simple, yet enormous challenge to overcome: rivers don’t like being blocked, and water is a powerful force. As such, engineering a successful dam is a complex project that requires a great deal of effort to ensure that the structure can withstand the power of a river. Unfortunately, as with all engineering, not every dam is a success story. Sometimes it’s human error, sometimes it’s an act of nature – and, as in the case of a dam in Henan province in mainland China, sometimes it’s both.

The Floodlands

Like other ancient civilizations, China exists because of its rivers. The ancient Chinese were just as innovative when it came to water engineering, creating dams, dykes, and the “Grand Canal” – the longest canal in the world, connecting Beijing to Hangzhou and the Pacific Ocean beyond. And by the way, it was built in the 6th century.

Yangtze River in Yunnan
Yangtze River in Yunnan by BrokenSphere is licensed under CC-BY-SA

But just as these rivers bring wealth, they also bring catastrophe. China, as a country, is no stranger to floods. The Yellow and Yangtze rivers are two of the mightiest rivers on earth, and they have a reputation for breaking their banks. Of the ten deadliest floods in human history, five of them were in China. In most cases, there isn’t much they could do about it. However, sometimes these floods have a human element to them. It is a surprisingly persistent trend in Chinese history that the flood-prone nature of the rivers was used for warfare. Armies would intentionally destroy the flood barriers to let the rivers wash away advancing enemy forces. This is so common a trend that it was even done during World War 2, when China was invaded by Japan. The Nationalist government, under Chiang Kai-Shek, intentionally destroyed the levees of the Yellow River to slow the advancing Japanese armies and washed asunder an area of 54,000 km2 (20,800 square miles), almost the size of Croatia, killing over half a million Chinese civilians and rendering several million more refugees. And though it did somewhat slow the Japanese advance, the civilians in this area, furious at the Nationalist government, began cooperating with the Japanese – as well as the Chinese Communist Party, under Mao Zedong.

Mao Zedong and Revolutionary Engineering

Mao Zedong

Because of this event, as well as many other factors, Mao’s Communists would eventually defeat the Nationalists to win the Chinese Civil War. In 1949, the People’s Republic of China was established, full of promise to create a society more equal, more modern, and more innovative than anything that had come before, and soon China would be a rich, industrialized country.

That was the promise, at least. As it turned out, Mao wasn’t really a man of engineering. Or anything science related, really. He pushed Chinese farmers to melt down their tools in backyard furnaces to create steel (which is not how steel is made, but don’t tell Mao). He launched a campaign to kill sparrows in China because he believed that they were hurting agricultural output by eating seeds and crops (which allowed locusts, the things they actually ate, to explode in population but again, don’t tell Mao). And he signed off on the construction of a series of dams in Henan province (Chinese workers at the time didn’t have any experience in creating reservoir dams, but again, don’t tell Mao). One of the dams in this series of constructions was the Banqiao Dam, begun in April 1951 on the Ru River with the help of experts from the Soviet Union.

Now, it must be made clear that there’s some conflicting information on what the dam was actually for, or what the intentions of the government were when it was constructed. Some sources say it was for protecting against floods, some say it was for electricity generation, some say that it was for irrigation and agriculture. We’re not entirely certain, but protection against flooding seems the most likely answer. With that being said, here’s everything we know for sure. First, the dam was built at 21.5 meters (70.5 ft) high, later raised to 24.5 meters (80.3 feet), and it was initially made out of clay. Second, the government wanted the dam to “retain water”, and the dam was built for the purpose of creating a large reservoir behind it. And third, the dam was not exactly an exemplary piece of construction engineering.

This last part wasn’t entirely China’s fault – as said before, the workers who built the dam had no experience in creating reservoirs, which was why China enlisted the help of the Soviets. However, this inescapably meant that the dam had errors. Soon after it was completed in 1952, cracks began to appear in the dam and its sluice gates. With help from the Soviet experts, the dam was reinforced and dubbed “The Iron Dam”. While there’s no specific mention of how much “iron” was used, it’s probably safe to assume that this newer, reinforced design utilized a good deal of metal in the structure.

Yet the problems with the Banqiao Dam went deeper than that, specifically with its stated purpose of “retaining water”. Chen Xing, the lead engineer of the project and a guy who actually knew what he was talking about, said that the local geography of the dam was unsuited to the task of retaining water, and indeed that retaining too much water might increase the alkalinity of the soil, thereby rendering the surrounding farmlands unusable. He also said the design of the dam was inadequate, proposing that the dam have twelve sluice gates for the purposes of releasing excess water in order to minimize the chance of the reservoir overflowing.

Unfortunately for Chen, Mao was also not a fan of criticism. Chen was denounced by CCP officials as a “Rightist”, which was not a good thing to be labeled during Mao’s leadership. He was removed from the project, sent to another city, and the officials responsible arbitrarily reduced the number of sluice gates on the dam from twelve to five. It’s unclear if this had any direct impact on the disaster that would come later, but it illustrates the attitude towards this project that the CCP had. It wasn’t about safety or even science, it was about ideology.

Beyond the inherent flaws in the design and purpose of the dam, the environment surrounding it had been adversely affected by industrial activity. Deforestation and land degradation were prevalent, which some experts have pointed to as major causes of the later floods.

So, you have flawed land, a flawed dam, and a flawed approach to the whole situation. The disaster is already there; it’s just waiting for the big push to send it rushing forward. And that push would come in August 1975.

The Perfect Storm

On July 31, 1975, a tropical depression in the Western Pacific rapidly intensified into a tropical storm, which meteorologists named “Nina”. Within 24 hours, it had become a Typhoon, known in North America as a “Hurricane”. By August 2, it had achieved Category 4 status, with sustained winds of 250km/hr (155 mph). As it developed, it began to move towards the island of Taiwan and the Chinese mainland beyond it.

Perhaps the most noteworthy thing about Typhoon Nina was how unnoteworthy it was. While yes, it had reached Category 4 status with the potential for devastating damage, the actual impact of the storm was relatively uneventful. It devolved to Category 3 status before making landfall in Taiwan, which weakened it further. When it passed over the island, it avoided the heavily populated capital city of Taipei, instead crossing across the less densely populated center. Thousands of homes were still destroyed, and dozens of people were killed, but it wasn’t absolute devastation like it could have been. The mainland had a similar experience, with the weakened storm delivering a battering to coastal cities, but with the overall impact relatively contained. As tropical cyclones travel over land, they lose access to the warm water that allows them to survive. Typhoon Nina weakened from a tropical cyclone to a tropical storm as it traveled over China, only growing weaker as it went. People breathed easy; the storm was over.

But it wasn’t. Though the destructive potential of hurricane-force winds tends to get a lot of the popular attention, tropical cyclones have a more subtle destructive power to them: rain. As the storm curved northwards into Henan province, it ran into a cold front – a wall of cold air that stopped it from moving. For three days, the remnants of Typhoon Nina dropped a torrent of water on the province. More than 400mm (16 in) of water fell across an area of 19,410 km2 (7,500 square miles). In one location, rainfall was recorded at 1,631 mm (64.2 in), with 830mm (33 in) of rain falling in just six hours. That location was the Banqiao Dam.

Even a structurally sound dam would struggle to manage the torrential rainfall it was faced with. This was not a structurally sound dam. A request was made to open the sluice gates on August 6 to release the excess water, but this was denied until August 7 due to flooding downstream. But as if that weren’t bad enough, the five sluice gates on the dam were partially blocked by sediment, and were unable to dump water quickly enough. Finally, a little after 1:00 AM on August 8, the water rose 30 cm above the crest of the dam – and that was it. The entire structure proceeded to fail, and in just six hours, 700 million cubic meters of water had flowed into the flat farmlands beyond.

A Textbook Tragedy

The Banqiao Dam was not the only dam to fail as a result of Typhoon Nina. In addition to several smaller dams, another dam upstream known as the Shimantan Dam also failed catastrophically due to the rain. These two dams were the largest of the Henan dams, and their failure would cause a domino effect as a wave of water, 10 km (6.2 mi) wide and 3-7 meters (9.8-23 ft) tall rushed outward at 50 km/hr (31 mph). 

As the flood swept away everything in its path, the authorities tried desperately to contain the disaster. There was a fear that the water from the Banqiao and Shimantan Dams would cause other larger dams in the area to fail as well. To stop this from happening, smaller dams were deliberately destroyed by air strikes in an attempt to channel the water away. Despite these efforts, three million acres of land, home to seven million people, were completely inundated with water. Temporary lakes as large as 12,000 square kilometers (4,600 square miles) were created from the flooding.

All in all, a total of 62 dams failed in the disaster, and entire villages were swept away by the waves. There was no evacuation plan, no resources in place, and essentially no preparedness whatsoever for a disaster of this magnitude. In the days following the flooding, the millions of people who survived had nothing. Homes and family members were lost. There were food shortages and sickness from villagers drinking the contaminated flood water. Food and supplies had to be air-dropped to isolated civilians. The official death toll from the Chinese government stands at 26,000, but a study by China’s Ministry for Water Resources and Electric Power in 1989 says that the breach of the Banqiao Dam caused as many as 85,000 people to “die instantly”. Some studies put the death toll at 230,000.

No media or journalists were allowed into the area because at the time, the Chinese government considered the death tolls of natural disasters a state secret. But alas, is it really that simple to call the Banqiao Dam failure a natural disaster? It is, unfortunately, undeniable that the structural flaws in the dam’s construction contributed to its failure.

Lessons of History

Though the Chinese government continues to classify the Banqiao Dam failure as a natural disaster, behind the scenes it has been spending a vast amount of resources to ensure that a disaster of this scale doesn’t happen again. China has tens of thousands of dams and reservoirs, many of which were built around the same time as the Banqiao Dam. Many of them are, thankfully, in the process of being reexamined and reinforced. Even so, the government built the Three Gorges Dam, one of the largest dams on earth, despite warnings from scientists about its structural integrity. We can only hope that it won’t be tested in the same way that Banqiao was.

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