The catastrophic dam failure in China once killed 171,000 people

The disaster of Ban Kieu dam in China in 1975 is one of the horrific dams in the world.

The sky fell, the earth cracked

In 1975, after a period of rapid dam development, a storm and other factors caused the Ban Kieu dam, Henan province, China to burst, killing about 171,000 people, International Rivers reported.

On the night of August 8, 1975, a stream of people hurriedly stacked sandbags to the top of Ban Kieu dam, Ha Nam province, amid the worst storm ever recorded to date in the region. They are racing against the rising water in the Nhu River to save Ban Kieu dam and millions of people are sleeping downstream. It was a race that they were about to lose.

Around 1am, the sky was clear, the stars peeked out from the storm clouds. There was a strange calm when someone shouted: "The water level is falling! The floods are receding".

But there are few opportunities to enjoy that tranquility. A witness who survived the Ban Kieu dam disaster recalled that just a few seconds later the sounds "sounded like the sky was falling and the earth was broken". The water in the reservoir is equivalent to 280,000 Olympic standard swimming pools overflowing the dam, engulfing entire towns below the dam.

In 2005, 30 years after the Ban Kieu dam collapse, historical records began to be reopened and scholars sought to redefine this event.

The Ban Kieu Dam, completed in 1952, is part of a campaign to exploit hydroelectricity on the Hoai River - the third largest river in China after the Yangtze and the Yellow River - along the tributaries of the Huai River after floods. seriousness of previous years.

Action is too late

Shortly after the Ban Kieu dam was completed in 1952, according to International Rivers, cracks appeared. Therefore, in the period of 1955-56, this structure was renovated, bringing Ban Kieu into an invincible "Steel Dam".

However, on August 5, 1975, a storm struck with a cold fridge (the front edge of the colder and drier air mass, which was moving and gradually replacing the hotter mass in front of it) in Ha Nam and causing heavy rain in the area less than 24 hours later. The rainfall of up to 106cm on that day exceeded the 30cm daily limit that Ban Kieu dam designers had planned. Witnesses recounted that the rainfall was so great that the bodies of the birds rained dead scattered in the area.

In an effort to minimize downstream flooding, which was already very serious, Ban Kieu dam was ordered not to open all flood gates since the storm began. The communication line was cut so that the operators did not know what the situation outside the area was going on.

By the time the flood gates were fully opened, it was too late. Water rises faster than water can discharge. Experts recommend placing 12 flood discharge gates at Ban Kieu dam when designing. However, only 5 floodgates were built and these floodgates were partially blocked by silt accumulation when the storm struck.

Also according to International Rivers, when Ban Kieu dam breaks, the water with a velocity of up to 50 km / h rushes towards the valley below, sweeping away 62 other dams like the domino effect. Within minutes, entire villages with thousands of residents were submerged.

In a 2010 documentary by Chinese television station CCTV, one survivor recalled this shocking moment: "I didn't know where I was - just floating in the water, screams and wailing sounds. suddenly, all of that sound stopped, I was drowned in deadly silence. "

Within 6 hours after the Ban Kieu dam burst, an estimated 26,000 people were killed, many of whom were sleeping. The non-smooth communication lines leave no opportunity for any large-scale evacuation.