1975 Banqiao Dam failure


The 1975 Banqiao Dam failure was the collapse of 62 dams including the largest Banqiao Dam in Henan, China due to Typhoon Nina of 1975. In August 1975, the dam failure created the third-deadliest flood in history which affected a total population of 10.15 million and inundated around 30 cities and counties of 12,000 square kilometers, with an estimated death toll ranging from 85,600 to 240,000. The flood also caused the collapse of 6.8 million houses. The dam failure took place during the Chinese Cultural Revolution when most people were busy with the "revolution"; the Communist Party of China as well as the Chinese government subsequently hid the details of the disaster until the 1990s, when The Great Floods in China's History, a book prefaced by Qian Zhengying who served as the Minister of Water Resources of China in 1970s and 1980s, revealed part of the information to the public for the first time.
Most of the dams that collapsed in this disaster were built with the help of experts from the Soviet Union or during the Chinese Great Leap Forward. The construction of the dams thus emphasized the goal of retaining water and overlooked their capacities to prevent floods, while the quality of the dams was also compromised due to the Great Leap Forward. Some experts have also pointed out that the Great Leap Forward as well as "Learn from Dazhai in agriculture" severely damaged the ecosystem and forest cover in the region, which was a major cause of the flood, and the government's mishandling of the dam failure, however, further contributed to the casualties. The official documents of the disaster were declassified in 2005 by the Chinese government. In May 2005, the Banqiao Dam failure was rated No.1 in "The Ultimate 10 Technological Disasters" of the world by Discovery Channel, outranking the Chernobyl nuclear disaster.

Historical background

Construction of the dams

Starting 1951, three major main reservoirs and dams were under construction in Zhumadian, Henan, including Banqiao Dam, Shimantan Dam and the Baisha Dam. At the time, the Chinese workers had no experience building the major reservoirs and, as a result, the design and construction was completely under the guidance of experts from the Soviet Union. The design of the dams overly focused on the purpose of water storage while overlooking the capacities of preventing floods. By 1953, the construction work at the three reservoirs was completed, but a "reinforcement" project on Banqiao and Shimantan was further carried out during 1955-1956 according to the standards of Soviet Union.

The Great Leap Forward

During the Great Leap Forward launched by Mao Zedong, over 100 dams were built in the Zhumadian region from 1957–1959. Tan Zhenlin, then Vice Premier of the People's Republic of China, generalized and then issued the guidelines of reservoir construction as "focusing on retaining water" and "building more small reservoirs". At the time, "retaining more water" meant "more revolutionary".
On the other hand, the intense activities of steel production during the Great Leap Forward as well as the "Learn from Dazhai in agriculture" program initiated by Mao Zedong severely damaged the ecosystem of the Zhumadian region. The percentage of forest cover dropped drastically and land degradation was prevalent, which, according to some experts, were the major causes of floods.

Whistle-blower

, then the Chief Engineer of the dam projects, opposed idea of prioritizing "retaining water" and provided scientific argument. He pointed out that the local geographical conditions made it unreasonable to overly emphasize the reservoir's function of water storage, for otherwise there was risk of creating serious floods and other disasters such as alkalinization of farm land. Nevertheless, Chen's warning was ignored and he was criticized for being a "Rightist" and "Opportunist"; soon, he was removed from his post and was sent to Xinyang.

The Cultural Revolution

The disaster of dam collapse occurred during the Chinese Cultural Revolution, when most people were busy with the "revolution" and had little time preventing the disaster. In fact, there were no equipments or resources at all for preventing the floods.
After the disaster, Zhang Guangyou, a journalist from the Chinese governmental Xinhua News Agency visited the area and interviewed several experts, who were afraid of speaking up their opinions in the public because otherwise they may be condemned for "questioning Cultural Revolution" and "questioning Chairman Mao". However, the experts told Zhang in private that the land degradation and the damage of ecosystem due to the Great Leap Forward launched by Mao were the major causes of the collapse of the dams.

The collapse of dams

Typhoon Nina

August 6–7

Communication with the dam was largely lost due to failures. On August 6, a request to open the dam was rejected because of the existing flooding in downstream areas.
On August 7 the request was accepted, but the telegrams failed to reach the dam. The sluice gates were not able to handle the overflow of water partially due to sedimentation blockage. On August 7 at 21:30, the People's Liberation Army Unit 34450, which was deployed on the Banqiao Dam, sent the first dam failure warning via telegraph.

August 8

On August 8, at 01:00, water at the Banqiao crested at the 117.94 m level above sea level, or 0.3 meter higher than the wave protection wall on the dam, and it failed. The same storm caused the failure of 62 dams in total. The runoff of Banqiao Dam was 13,000 m3 per second in vs. 78,800 m3 per second out, and as a result 701 million m3 of water were released in 6 hours, while 1.67 billion m3 of water were released in 5.5 hours at an upriver Shimantan Dam, and 15.738 billion m3 of water were released in total.
The resulting flood waters caused a wave wide and high in Suiping that rushed onto the plains below at nearly, almost wiping out an area long and wide, and creating temporary lakes as large as. Seven county seats, Suiping, Xiping, Ru'nan, Pingyu, Xincai, Luohe, and Linquan were inundated, as were thousands of square kilometers of countryside and countless communities. Evacuation orders had not been fully delivered due to weather conditions and poor communications. Telegraphs failed, signal flares fired by Unit 34450 were misunderstood, telephones were rare, and some messengers were caught by the flood.
To protect other dams from failure, several flood diversion areas were evacuated and inundated, and several dams were deliberately destroyed by air strikes to release water in desired directions. The Nihewa and Laowangpo flood diversion areas downstream of the dams soon exceeded their capacity and gave up part of their storage on August 8, forcing more flood diversion areas to begin to evacuate.

August 9

The dikes on the Quan River collapsed in the evening of August 9, and the entire Linquan county in Fuyang, Anhui was inundated. As the Boshan Dam, with a capacity of 400 million m3, crested and the water released from the failures of Banqiao and Shimantan was rushing downstream, air strikes were made against several other dams to protect the Suya Lake dam, already holding 1.2 billion m3 of water.

Later period

The Jingguang Railway, a major artery from Beijing to Guangzhou, was cut for 18 days, as were other crucial communications lines. Although 42,618 People's Liberation Army troops were deployed for disaster relief, all communication to and from the cities was cut. Nine days later there were still over a million people trapped by the waters, who relied on airdrops of food and were unreachable by disaster relief workers. Epidemics and famine devastated the trapped survivors. The damage of the Zhumadian area was estimated to be about . The Zhumadian government appealed to the whole nation for help, and received more than in donations.

Aftermath

Cover-up and declassification

After the disaster, the Communist Party of China and the Chinese government remained silent to the public, while no media were allowed to make reports.
In 1987, Yu Weimin, a journalist from Henan Daily wrote a book on the disaster, while in 1995 the news agency took the lead and published details about the disaster to the public. At the official level, The Great Floods in China's History revealed part of the information to the public for the first time; the book was prefaced by Qian Zhengying who served as the Minister of Water Resources of China in 1970s and 1980s.
The official documents of this disaster were considered a state secret until 2005 when they were declassified. Scientists from China, Italy and the United States subsequently attended a seminar in Beijing, discussing the details.

Casualties

It has been reported that 85,600-240,000 people were killed as a result of the dam breaking, although the official figure is 26,000. For example, while only 827 out of 6,000 people died in the evacuated community of Shahedian just below Banqiao Dam, half of a total of 36,000 people died in the unevacuated Wencheng commune of Suipin County next to Shahedian, and the Daowencheng Commune was wiped from the map, killing all 9,600 citizens.
The Chinese government deems the dam failure a natural one as opposed to man-made disaster, with government sources placing an emphasis on the amount of rainfall as opposed to poor engineering and construction. The People's Daily has maintained that the dam was designed to survive a once-in-1000-years flood but a once-in-2000-years flood occurred in August 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 westward. As a result of this near stationary thunderstorm system, more than a year's worth of rain fell within 24 hours rainfall per hour and 1060 mm per day, exceeding the average annual precipitation of about 800 mm ), which weather forecasts failed to predict. China Central Television reported that the typhoon disappeared from radar as it degraded. According to Xinhua, the forecast was for rainfall of 100 mm by the Beijing-based Central Meteorological Observatory.
After the flood, a summit of National Flood Prevention and Reservoir Security at Zhengzhou, Henan was held by the Department of Water Conservancy and Electricity, and a nationwide reservoir security examination was performed.