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Yangtze River floods
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What is the Yangtze River?
The Yangtze River, also known as Chang Jiang or "Long River" in China, is the longest river in China and Asia, and the third-longest in the world, stretching approximately 3,915 miles (6,300 km). Its basin is China’s great granary and contains nearly one-third of the national population.
Yangtze River floods have occurred periodically throughout history, causing immense destruction and loss of life. The primary flood region lies in the river's lower course, downstream of the Three Gorges Dam, where the river flows through low-lying terrain with lakes and marshes. Major floods include those of 1870, 1931, 1954, 1998, 2010, and 2020. The 1931 flood resulted in an estimated 3.7 million deaths and left 40 million homeless. The Three Gorges Dam was built to help control these floods.
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What are Yangtze River floods?
Yangtze River floods are recurring inundations along China's Yangtze River, known for causing widespread property damage and loss of life. These floods typically occur in the lower course of the river, downstream of the Three Gorges Dam, where the terrain is low-lying and dotted with lakes and streams.
Heavy monsoon rains in the middle and lower basin regions are the primary cause, typically starting in March or April and potentially happening anytime during the following eight months. The most destructive floods happened in 1870, 1931, 1954, 1998, 2010, and 2020. The 1931 flood, for example, covered over 30,000 square miles, killed an estimated 3.7 million people, and left 40 million homeless.
The Three Gorges Dam was built to help control these floods. While it proved effective in 2010, it sometimes has to open its floodgates, which can still lead to flooding and landslides.
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Why do floods happen along the Yangtze River?
Floods along the Yangtze River typically occur from March to October due to monsoon rains. The most flood-prone area lies downstream of the Three Gorges Dam, characterized by low terrain with lakes and streams.
Throughout history, silt deposits in the riverbed and deforestation have exacerbated flooding. The river's current slows as it enters the plains, causing silt to settle and raise the river bottom. Deforestation reduces the land's capacity to absorb heavy rains, increasing runoff. The Three Gorges Dam was built to help control the flooding.
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What problems do Yangtze River floods cause for people and the environment?
Yangtze River floods have historically caused immense destruction and loss of life. The 1931 flood, one of the deadliest natural disasters ever, resulted in an estimated 3.7 million deaths and left 40 million homeless. These floods inundate vast areas, including major cities like Nanjing and Wuhan, and destroy crops.
Environmental consequences include increased soil erosion and silt loads due to deforestation and overgrazing. Land reclamation reduces the surface areas of lakes and wetlands, which otherwise help to control flooding. Changes to the river's flow can also adversely affect endangered species such as the Chinese alligator and the Chinese sturgeon.
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What were some of the worst floods in the history of the Yangtze River?
The Yangtze River has a history of devastating floods due to its geography and monsoon climate. Some of the worst floods include:
- 1870 Flood A major flood event.
- 1931 Flood This catastrophic flood covered over 30,000 square miles (77,700 square km), resulting in approximately 3.7 million deaths and leaving 40 million people homeless.
- 1954 Flood Although destructive, with some 30,000 deaths, flood-control measures limited potential damage.
- 1998 Flood Resulted in 3,650 deaths.
- 2010 Flood Despite the Three Gorges Dam minimizing downstream flooding, hundreds still died from flooding and landslides in the Yangtze basin.
- 2020 Flood A major flood event.
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What is being done today to prevent or reduce flooding along the Yangtze River?
To mitigate Yangtze River floods, one major objective was the Three Gorges Dam project, which proved effective in 2010 by holding back floodwaters and minimizing downstream flooding. However, the dam had to open its floodgates to reduce the high water volume in the reservoir. Other efforts to control the river include the Great Jinjiang Levee, completed in 1548, and more-effective levees that were built after the catastrophic flood of 1931.
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Yangtze River floods, floods of the Yangtze River (Chang Jiang) in central and eastern China that have occurred periodically and often have caused considerable destruction of property and loss of life. Among the most recent major flood events are those of 1870, 1931, 1954, 1998, 2010, and 2020.
The Yangtze River, the longest river in Asia, also is one of the world’s major waterways. It originates at an elevation above 16,400 feet (5,000 metres) in the Plateau of Tibet and proceeds generally eastward along a winding course until it empties into its major delta system on the East China Sea. The primary flood region is the lower course, downstream of the Three Gorges Dam, an area in which the river flows through low-lying terrain dotted by lakes, marshes, and meandering streams. Increases in the region’s population led to efforts to control the river. The Great Jinjiang Levee, completed in 1548, was one of many barriers constructed, and by the late 19th century the Yangtze could drain through only four openings on the south side of the river. Consequently, sediment was deposited only on the river bottom or in Dongting Lake, which caused the flood level to rise and created a lowland on the north bank. In addition, many of the lakes that had once acted as flood control either were cut off from the river by levees or were converted into cropland. Deforestation further reduced the capacity of the area to handle intense rains, which created more runoff.
As a result, when the lower Yangtze basin has experienced sustained heavy rains, the consequences have been catastrophic. The flood of 1931 covered more than 30,000 square miles (77,700 square km), including the cities of Nanjing and Wuhan; it ultimately led to the deaths of an estimated 3.7 million people and left 40,000,000 more homeless. Subsequently, more-effective levees were built, but the floods of 1954 and 1998 were still highly destructive and killed some 30,000 and 3,650 people, respectively. One of the major objectives of the Three Gorges Dam project was to alleviate flooding on the lower Yangtze. The dam proved effective during the extraordinarily rainy summer of 2010 by holding back much of the resultant floodwaters and thus minimizing the impact of flooding downstream. However, the dam still had to open its floodgates to reduce the high water volume in the reservoir, and flooding and landslides in the Yangtze basin killed several hundred people and caused extensive property damage.
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