Study reveals sinking crisis in Chinese cities

This Thursday (18), a study published shows that the land is giving way under the feet of millions of inhabitants of China's main cities, which increases the likelihood of flooding and rising sea levels in the country's coastal areas.

Alert in China

According to research recently published in the journal Science, almost half of China's urban regions, comprising 29% of the total population, are sinking at a rate of more than 3 millimeters per year. This means that approximately 270 million people live in areas affected by this phenomenon. At the same time, around 67 million individuals live in places where sinking is even more accelerated, exceeding 10 millimeters annually. The researchers point out that the uncontrolled extraction of groundwater in China is one of the main drivers of this problem.

In cities, water withdrawal from underground aquifers exceeds its replacement capacity, especially due to drought conditions intensified by climate change. This excessive pumping leads to a decrease in the water table and contributes to the sinking of the land. Furthermore, urban growth puts additional pressure on the land. Soil naturally compacts over time due to the accumulation of sediment and the weight of buildings, resulting in continuous sinking of the land.

Land sinking beyond China

Soil decline is not just a concern in China. In the US, several coastal cities, including New York, face similar problems. In the Netherlands, a quarter of its land has already sunk below sea level. In Mexico City, possibly the most affected globally, the ground is giving way at an impressive rate, reaching up to 50 centimeters per year. Subsidence combined with rising sea levels along coasts amplifies the risk of devastating floods to land, people and property.

Embed from Getty Images

_{Typhoon Doksuri unleashed extreme rainfall that flooded Beijing, marking the worst storm in 140 years in the Chinese capital (Photo: reproduction/Kevin Frayer/Getty Images Embed)}

About a quarter of China's coastlines are predicted to be below sea level due to subsidence and sea level rise, posing a significant danger to life and property. Tianjin, Shanghai and areas near Guangzhou are particularly vulnerable to these problems, according to the study. Some coastal areas in China have already implemented protection measures against the growing flood risk, although the study does not take these measures into account.

Dikes against sinking

In Shanghai, impressive dike systems, several meters high, were built to mitigate risks. Shengli Tao, co-author of the study and professor at Peking University, said these coastal dike systems will greatly reduce the risk of flooding, even in the face of sinking land and rising sea levels. He also highlighted that there is no knowledge of other countries that have built dike systems as massive as those in China. Lastly, Tao stated that the Chinese government is combating the problem of land subsidence with strict laws on groundwater extraction.

In and around Shanghai, restrictions on groundwater withdrawals have helped reduce subsidence. Additionally, a project to pump water from the Yangtze River to northern China has halted subsidence in Beijing. Tao believes these efforts will address the problem, but recommends continuing to monitor groundwater withdrawals and maintain levee systems in coastal areas.

Featured photo: Flooded street after heavy rain in the Mentougou district of Beijing (Reproduction/Getty Images Embed)