Experts found that cities are sinking faster than other places due to the flooding caused by rising sea levels. The study analyzed 99 metropolitan places located in various countries to find which of them already exceeds the normal rate of effects caused by the abnormal elevation of sea waters.
Subsidence and Rise of Sea Levels
A woman cleared her flooded shop on December 8, 2020, in Venice following a high tide "Alta Acqua" event following heavy rains and strong winds, and the mobile gates of the MOSE Experimental Electromechanical Module that protects the city of Venice from floods were not lifted.
A geological process known as subsidence was utilized to screen the selected places for the investigation. In this principle, the materials below Earth change, causing the land above to undergo massive transitions.
Subsidence is one of the main reasons why most of the landmass in many cities on the planet sinks by millimeters from its original elevation. Most of the factors that enable subsidence are induced by human activities. For example, groundwater pumping pushes the water to flow out from underground, causing the soil to be disturbed and making structures above level closer to the sea.
According to a paper from PNAS titled "Climate-change-driven accelerated sea-level rise detected in the altimeter era," a total of 33 cities are sinking one centimeter per year, which is five times the rate of the normal rise in sea levels.
Because of the uncontrolled phenomenon, the affected cities developed challenging ways to adapt. In a report by The Washington Post, Indonesia plans to move its capital from Jakarta to a new place on Borneo island due to the city's current state brought by rising sea levels.
According to the Intergovernmental Panel on Climate Change (IPCC), the models focused on rising sea levels alone would be insufficient to predict the future if subsidence continues to persist. This means that the process of disturbing underground materials would add up to the estimated impacts shown in sea-level studies, leading to the present coastal areas becoming submerged unexpectedly by the waters.
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Stopping Human Activities Related to Floodings Could Slow Down Sinking of Cities
Despite the efforts exhibited by governments to make their cities floodproof, great attention is also required to establish regulations limiting human activities that sink the regions.
Alongside natural changes underground, other issues need to be addressed, such as drilling of gas and oil, pumping of groundwaters, and rapid construction of intensely grounded infrastructures.
The authors identified that groundwater pumping is the largest contributor to subsidence. In Asia, many industrial and residential buildings also tend to sink faster solely because of excessive underground water extraction. Mexico already sinks 50 centimeters per year due to the same problem, Big Think reports.
In a local region of Jakarta, local authorities already prohibited any activities related to groundwater extractions in 2022. Although the rise of sea levels is irreversible, the country proved that there is still a solution to revert the human-induced problems and slow down the subsidence to protect their citizens,
The study was published in Geophysical Research Letters, titled "Subsidence in Coastal Cities Throughout the World Observed by InSAR."
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