It’s the most populous city in Western Asia, and it’s sinking into the ground at an alarming rate.
Peter Dockrill reports for Science Alert:
Tehran, the capital of Iran and home to some 15 million people in total across its greater urban footprint, is a victim of dramatic subsidence, new research reveals, which is causing the region to sink by more than 25 centimeters (almost 10 inches) annually in some parts.
Using satellite data, researchers at the GFZ German Research Centre for Geosciences in Potsdam analyzed the extent of subsidence in the Tehran region between 2003 and 2017.
Thanks to a technique called Interferometric Synthetic Aperture Radar (InSAR), which can detect extremely subtle changes in ground deformation over time, the team identified three distinct areas where the ground is sinking by more than 25 centimeters per year.
In areas of more moderate subsidence, like the land in the immediate vicinity of Tehran international airport, the sinking is still considerable, at about 5 centimeters annually.
What’s the cause of this widespread instability? A history of accelerated influx and the attendant overuse of natural resources.
“In recent decades, rapid population growth combined with urban and industrial development has increased the need for water supplies in the Tehran Plain,” the authors explain in their paper.
“As a result of extensive groundwater depletion, the plain has been undergoing rapid land subsidence.”
This subsidence in Tehran has been the focus of much prior research, but the latest data put the sinking in greater context.
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