The 1975 Banqiao Dam Failure

In early August 1975, a Pacific hurricane passed on the coast of South China through Fujian Province, all the way to the north of Henan province. The warm, humid air of the typhoon met the cooler air of the north, causing a series of storms. This was due to the change in weather patterns. Three sets of storms that ensued dropped a meter of water in just three days. On the August 5, the first storm dropped 0.448 meters; this was 40% greater than the previous record. The second storm occurred on August 6, and the downpour lasted 16 hours. Later, on August 7, the third storm lasted 13 hours. China’s Shimantan and Banqiao dams were constructed along rivers and could only handle a maximum of 0.5 meters of water over three days.

The three storms caused water to fill the 2 dam reservoirs to capacity; hence, the excess runoff exceeded the rate at which water could be expelled from the dams. To begin with, the Shimantan dam reservoir on the Hong River collapsed at midnight when water rose 40 centimeters above the crest of the dam. Within five hours, its 120 million cubic meters of water was emptied.

Shortly after 1am, the Banqiao dam on the Ru River crested. Some brave people tried working in the storm to save the embankment, but their efforts were only futile. The dam’s walls crumbled, and the 600 million cubic meters of water that was behind the 6-meter high and 12-kilometer wide walls came raging like a dragon.

A total of 62 dams broke in the process. The flood diversions and dikes could not withstand the force of the water downstream; they all broke. This caused flooding of 2.5 million acres of farm land across 29 counties and municipalities. The predicaments at Huaibin city where the waters from rivers Hong and Ru met were terrible. More than 85,000 people died. This was so unfortunate because the dams collapsed without sending any warning signs. Besides that, the walls of water was travelling at about 50 kilometers per hour and telephone communication had been affected by the floods. Those who survived the flood ordeal were trapped on trees, and they went for days without food, so they had to die. Many were affected by water-borne diseases also, and they succumbed.