Several large cities in China threatened by significant flood risks: millions of inhabitants at risk

More than half of China's major cities are sinking into the ground, according to estimates from a recent study. zhang kaiyv/Unsplash

More than half of China's major cities are sinking into the ground, a study estimates. Mainly linked to the weight of buildings and the extraction of groundwater, this land subsidence is likely to increase the risk of flooding, which represents a serious threat for the inhabitants of these areas. cities, which number in the millions.

More and more often subject to climatic events such as heatwaves or heavy rains, China is faced with an additional threat: the subsidence of the soil in its large metropolises. This is demonstrated by a study led by an international group of researchers and published in the journal Science.

Land subsidence was assessed using satellite data measured in 82 major Chinese cities between 2015 and 2022. "Of the urban land surveyed, 45% are sinking at a rate greater than 3 millimeters per year, and 16% at a rate greater than 10 millimeters per year, affecting 29% and 7% of the urban population, respectively. ;, demonstrates the research. The authors of the work note two main causes for this alarming subsidence: the pumping of groundwater and the weight of buildings.

Significant flooding

Combined with rising sea levels, this subsidence risks leading to significant flooding, putting millions of people at risk. The study estimates in particular that by 2120, 22 to 26% of China's coastal land will have a relative elevation below sea level. "Our results underline the need to strengthen protective measures to mitigate the potential damage from subsidence", warn the researchers.

China is not the only region in the world threatened by rising water levels and the weight of its skyscrapers. A study published in May 2023 showed that New York City was also particularly prone to land subsidence, estimated at around 1 to 2 mm per year on average. The issue is all the more crucial as the Big Apple, which has more than eight million inhabitants, is threatened with disappearing due to rising water levels as well as the amplification of hurricanes and storms.