The Banqiao dam and Shimantan Reservoir Dam are among 62 dams in Zhumadian, China, that broke catastrophically or were intentionally destroyed on August 8th, 1975, following the collision of Typhoon Nina and a cold front.
The typhoon was blocked for two days before its direction ultimately changed from northeastward to west. The death toll of this disaster was declassified in 2005.
The accident took an estimated 171,000 lives.
According to the Hydrology Department of Henan Province, approximately 26,000 people died from flooding. However, another 145,000 died during subsequent epidemics and famine. Unofficial estimates of the number of people killed by the disaster have run as high as 230,000 people.
11 million people lost their homes. It also caused the sudden loss of 18 GW of power, the power output equivalent of roughly 9 very large modern coal-fired thermal power stations.
As a result of this near stationary thunderstorm system, more than a year’s rain fell within 24 hours (new records were set, at 189.5 mm rainfall per hour and 1060 mm per day, exceeding the average annual precipitation of about 800 mm), which weather forecasts failed to predict.
It was the worst dam collapse ever. The People’s Daily claimed the causes of the dam failure were both natural and man-made. Investigations have also reported that the dam was poorly engineered and constructed making it vulnerable.