It was built to hold back almost 500 million cubic metres of water. Unfortunately one typhoon proved too much for the ‘Iron dam.’
The Banqiao Dam was built in the early 1950s as party of a huge project to control flooding and produce electricity in central China.
Despite warnings from hydrologist Chen Xing, the dam was built with only 5 sluice gates. Xing warned that it needed at least 12, although officials disagreed.
Almost as soon as the dam was completed, tiny cracks started to show in the sides. However, these were patched up by engineers, and the structure was not only considered safe, it also earned itself a safe nickname – the ‘Iron dam.’
Although there were problems with the construction of the dam, it was never predicted that it could fail as spectacularly as it did in August 1975. It had been built to withstand flooding, and could have coped with a huge amount of rainfall.
However, typhoon Nina smashed many records, as well as the dam itself. One night in August 1975, Typhoon Nina dropped more than a year’s worth of rain in just 24 hours.
The dam collapsed in the oncoming flood, and other dams further along the river collapsed too. A 10 km wide wave devastated the surrounding areas, causing more than 25,000 deaths. Hundreds of thousands more were affected by the epidemics and famine which followed the disaster.
Although it is difficult to prepare for something unexpected, such as Typhoon Nina, the damage at the time could have been minimised.
The sluice gates, designed to vary the water flow in case of heavy rainfall, were blocked by sediment. This, coupled with the fact that there were too few of them, meant that water built up at a much faster rate than it should have done in the dam basin.
On top of this, the gates should have been opened earlier than they were, as water from dams further upstream rushed towards the Banqiao. Unfortunately the order to open the gates did not reach the Banqiao in time, and the water broke the dam before the gates could be opened.
Do you think that engineers should be held responsible for the failure of the dam, or are the circumstances so unusual that no one is to blame for the disaster? Let us know your thoughts below.
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