2024-04-20 02:09:12
A study has found that China’s major cities are sinking due to rapid land subsidence. It also specifies that at this rate, around a quarter of China’s territory will be below sea level over the next 100 years.
According to an article published on the 19th in the international academic journal “Science”, a research team led by Professor Sheng Li Tao of Peking University in China analyzed that “major Chinese cities are sinking by more than 10mm each year due to increased groundwater use and construction of high-rise buildings.
The study was conducted by measuring and quantifying changes in the land surface of 82 major cities, representing three-quarters of China’s urban population, using satellite radar between 2015 and 2022. It is the first time satellite data has been used to systematically analyze the number of sinking cities in China.
The results showed that almost half of China’s urban areas, which account for 29% of the population, are sinking at a rate of more than 3 mm per year. The population of this area is approximately 270 million people. In particular, 67 million people live in a territory which is sinking at a rate of more than 10 mm each year. The researchers warn: “If this trend continues, around 26% of China’s territory will fall below sea level over the next 100 years,” adding: “This might cause enormous damage and put people’s lives at risk.” hazard “.
Researchers have cited excessive groundwater extraction as one of the main causes of land subsidence. The effects of land subsidence become more serious the closer you get to the coast. Representative examples are coastal metropolitan cities such as Beijing, Tianjin, Shanghai and Guangzhou. Researchers explain that they are more easily exposed to risks like storms and floods.
In fact, in May last year, due to ground subsidence, several roads collapsed and apartments tilted in an apartment complex in Tianjin, China. At the time, a special investigation team of around 20 experts concluded that complex causes appeared to have played a role in sudden localized subsidence of such magnitude.
The proliferation of tall buildings is another cause of land subsidence. The ground naturally sags under pressure due to the weight of sediments accumulating over time, but if it is excessive it causes phenomena such as a more rapid change in the elasticity of rocks and a solidification of sediments.
It was also found that repetitive loads and vibrations from urban transportation systems might potentially affect land subsidence. The reason is that subsidence occurred more quickly in areas around subways and highways in major cities like Beijing.
However, the researchers stressed that land subsidence is not just a Chinese problem. In the United States, dozens of coastal cities, including New York, are sinking. In the Netherlands, 25% of land has sunk below sea level and Mexico City is sinking at a rate of up to 50 centimeters per year. Robert Nicholls, a civil engineer at the University of East Anglia in the United Kingdom who reviewed the document, stressed the need to prepare countermeasures, saying: “The problem of land subsidence is a very big problem and might go beyond the national level and become a major problem. international problem. »
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