At the beginning of August in 1975 an unusual weather pattern led to a typhoon (Pacific hurricane) passing through Fujian Province on the coast of South China continuing north to Henan Province, (the name means "South of the (Yellow) River.") The rain storm that occurred when the warm, humid air of the typhoon met the cooler air of the north. This led to a set of storms which dropped a meter of water in three days. The first storm, on August 5 dropped 0.448 meters. This alone was 40 percent greater than the previous record. But this record-busting storm was followed by a second downpour on August 6 that lasted 16 hours. On August 7 the third downpour lasted 13 hours. Remember the Banqiao and Shimantan Dams were designed handle a maximum of about 0.5 meters over a three day period.
By August 8 the Banqiao and Shimantan Dam reservoirs had filled to capacity because the runoff so far exceeded the rate at which water could be expelled through their sluice gates. Shortly after midnight (12:30 AM) the water in the Shimantan Dam reservoir on the Hong River rose 40 centimeters above the crest of the dam and it collapsed. The reservoir emptied its 120 million cubic meters of water within five hours.
About a half hour later, shortly after 1 AM, the Banqiao Dam on the Ru River was crested. Some brave souls worked in waist deep water amidst the thunderstorm trying to save the embankment. As the dam began to disintegrate one of these brave souls, an older woman, shouted "Chu Jiaozi" (The river dragon has come!) The crumbling of the dam created a wall of water 6 meters high and 12 kilometers wide moving. Behind this moving wall of water was 600 million cubic meters of more water.
Altogether 62 dams broke. Downstream the dikes and flood diversion projects could not resist such a deluge. They broke as well and the flood spread over more than a million hectares of farm land throughout 29 counties and municipalities. One can imagine the terrible predicament of the city of Huaibin where the waters from the Hong and Ru Rivers came together. Eleven million people Throughout the region were severely affected. Over 85 thousand died as a result of the dam failures. There was little or no time for warnings. The wall of water was traveling at about 50 kilometers per hour or about 14 meters per second. The authorities were hampered by the fact that telephone communication was knocked out almost immediately and that they did not expect any of the "iron dams" to fail.
People in the flooded areas who survived had to face an equally harrowing ordeal. They were trapped and without food for many days. Many were sick from the contaminated water.
The hydrologist Chen Xing, who had criticized the dam-building program, was rehabilitated and taken with the high Party officials on an aerial tour of the devastated area. Chen was sent to Beijing to urge the use of explosives to clear channels for the flood waters to drain.