Half of China's cities may be under water – what happens to them?

Many large cities on earth are gradually subsiding, as a result of which their height above sea level is decreasing every year. Moreover, in some megacities this process occurs very quickly. In particular, a recent study by scientists showed that many Chinese cities with a population of more than two million people suffer from this. Over the last hundred years, some of them have already sunk several meters, and at the same time they continue to settle rapidly. As a result, millions of people are at risk of flooding. Cities such as Beijing, Shanghai and Tianjin were particularly hard hit. In the next hundred years, some megacities may be below sea level.

Half of China's cities may be under water - what's happening to them? Many Chinese cities may be flooded. Photo.

Many cities in China may be flooded

Chinese cities are settling at a high rate

The authors of a recent study examined 82 major Chinese cities. To do this, they used radar pulses from satellites. Thanks to them, you can monitor any changes in the distance between the satellite and the ground. In this way, the authors measured how much cities sank between 2015 and 2022.

The study results showed that 45% of Chinese cities are subsiding faster than 3 millimeters per year. In addition, 16% of cities have subsidence rates of more than 10 millimeters per year. As mentioned above, the situation is worst in Beijing, Shanghai and Tianjin. For example, Shanghai has sunk 3 meters over the past 100 years, and continues to sink rapidly.

Chinese cities are subsiding at a high rate. Shanghai has settled by more than 3 meters over the past 100 years. Photo source: www.airpano.ru. Photo.

Shanghai has settled by more than 3 meters over the past 100 years. Photo source: www.airpano.ru

Why Chinese cities are falling underground

The problem of urban subsidence is not limited to China. We told you earlier that a similar situation is observed all over the world. According to one study, by 2040, 2 million square kilometers of land could be below sea level. Moreover, this problem concerns Indonesia to the greatest extent.

There are various reasons for this phenomenon. According to some scientists, water intake is a key factor. People drain the soil and pump out groundwater, resulting in voids. Accordingly, the soil gradually settles. We previously reported that faults began to appear in the United States due to groundwater pumping. Therefore, one of the ways to solve the problem, according to experts, is to control the extraction of groundwater.

In addition, the cause of subsidence is the compaction of rocks under the weight of cities. Buildings and all kinds of structures have a large mass, as a result of which the soil beneath them begins to compress. In addition, it is quite possible that the pressure exerted by megacities on the ground leads to a redistribution of groundwater, that is, it rushes to those areas where the pressure is less. This also causes cities to settle.

Why are Chinese cities falling underground? The subsidence of cities threatens the destruction of buildings and critical infrastructure. Photo.

City subsidence threatens the destruction of buildings and critical infrastructure

What is the danger of urban subsidence

The subsidence of large cities primarily affects buildings, the integrity of which is under threat. In addition, critical infrastructure is suffering. As Reuters reports, the subsidence of megacities is already costing China more than $1 billion.

However, the destruction of buildings and infrastructure is far from the only and not the most dangerous problem. The lower cities are, the higher the risk of flooding. This is especially true for coastal regions. Of course, precipitation does not occur so quickly, but changes associated with global climate change should also be taken into account, namely rising sea levels due to melting glaciers.

What is the danger of urban subsidence. Melting glaciers leads to a rapid rise in sea levels. Photo.

Melting glaciers are leading to rapid sea level rise

As a result, the risk of urban flooding increases greatly. Flood-related problems may arise in the near future. But the most dangerous situation will become in the next century. Researchers report that in 2120, 22 to 26% of China's coastal land will be below sea level. Between 9 and 11% of the country's population currently live in these territories. According to scientists, the data obtained suggests that the necessary measures need to be taken today.

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Finally, we note that scientists are often mistaken and revise their forecasts regarding climate warming and rising sea levels. In particular, glaciers are melting more rapidly than previously thought. Therefore, it is quite possible that the problem of urban flooding will arise even earlier.