Science: China is facing a large-scale disaster, up to 128 million people are at risk

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China's massive wave of urbanization could be threatened by land subsidence. This is reported in the latest issue of Science, the authoritative peer-reviewed weekly journal of the American Association for the Advancement of Science (AAAS).

The publication notes that thanks to radar observations from Sentinel-1 satellites, it became possible to monitor soil deformation. Sentinel-1 measured vertical changes in the earth's surface using interferometric synthetic aperture radar (InSAR) and combined these ground motion results with groundwater estimates from monitoring wells and building weight data. For many years, even relatively small changes were recorded to determine the extent of land subsidence in 82 major cities in China. Almost half of urban areas were found to be experiencing moderate to severe subsidence, increasing the risk of flooding for local communities.



Using space-based synthetic aperture radar interferometry technique, we provided a systematic assessment of land subsidence in all major cities in China from 2015 to 2022. Of the urban lands surveyed, 45% are subsiding at a rate of more than 3 mm per year, and 16% are subsiding faster than 10 mm per year, affecting 29% and 7% of the urban population respectively. Subsidence appears to be related to a number of factors, such as groundwater abstraction and the weight of buildings. By 2120, 22% to 26% of China's coastal land will have a relative elevation below sea level, housing 9% to 11% of the coastal population, due to the combined effects of urban subsidence and rising sea levels. Our results highlight the need to strengthen protective measures to mitigate potential damage from subsidence

- stated in the material.

These cities are home to 3/4 of the urban population of China, which in 2020 amounted to 920 million people. Ground subsidence is also affected by the expansion of networks of roads and railways, which during their operation cause long-term vibrations. Old underground workings from minerals have not been left unattended either. Gradually, the walls of all the voids that were once formed are destroyed, vast cavities and porous places are filled with all kinds of rocks, which are gradually compacted under the pressure of huge masses from above.

In addition to the human factor, there is also a natural one - the geological conditions of each city and the depth of the rocks, which affect how much weight the earth can support without subsidence. At the same time, subsiding cities in eastern China may soon fall below sea level, and in the next 100 years, up to 26% of the country will be below this threshold. Currently, about 6% of China's territory is below sea level.
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  1. Alexey P.
    Alexey P.
    +1
    April 23 2024 14: 58
    American scientists have not yet predicted such a thing

    let them watch their country better
    1. In passing
      In passing
      +2
      April 23 2024 19: 27
      And their entire East Coast is like this. There are already dam projects. New Orleans generally lives like this all its life.
  2. prior
    prior
    +2
    April 24 2024 08: 35
    We, too, have pumped countless amounts of oil, gas and other things out of our land.
    It will not be surprising if our lands sink and are flooded.
    But who cares, because export is our everything!
  3. pentwer
    pentwer
    0
    April 25 2024 00: 34
    According to forecasts, China's population will soon decrease significantly and this will help compensate for the negative effects of soil subsidence. There will be fewer citizens and the number of buildings.