Sinking land, also known as subsidence, is a growing concern in urban areas globally, according to scientists from Virginia Tech and the University of East Anglia in the United Kingdom. In an invited perspective article for the journal Science, the researchers highlight the importance of recent studies analyzing how and why land is sinking, including a study focusing on Chinese cities.
Nearly Half of Chinese Cities Analyzed Are Sinking
The accompanying research study revealed that of the 82 Chinese cities analyzed, 45 percent are sinking, potentially affecting nearly 270 million urban residents. Hard-hit urban areas such as Beijing and Tianjin are sinking at a rate of 10 millimeters a year or more, increasing the risk to infrastructure like roadways, runways, building foundations, rail lines, and pipelines.
“Land is sinking almost everywhere,” said Manoochehr Shirzaei of Virginia Tech, who was not involved in the China-focused study but whose recent research using satellite-monitoring techniques shed light on the growing dangers of sinking land along the U.S. East Coast. “If we don’t account for it in adaption and resilience plans now, we may be looking at widespread destruction of infrastructure in the next few decades.”
Advances in Satellite Monitoring Reveal Extent of Land Sinking
The technique used to map consistent large-scale measurements of sinking land in China relied on space-based radar. Over the past decade, advances in satellite imaging technology have granted researchers the ability to measure millimeter-scale changes in land level over days to years.
“This is a relatively new technique,” said Shirzaei. “We didn’t have the data before. Now we have it, so we can use it — not only to see the problem, but to fix the problem.”
While consistently measuring the sinking of urban land will provide a baseline to work from, predicting future subsidence requires models that consider all drivers, including human activities and climate change and how they might change with time.
Human Activity Causes and Can Address Land Sinking
Land sinking is mainly caused by human action in cities, with groundwater withdrawal being the most important driver, combined with geology and the weight of buildings. However, recharging the aquifer and reducing pumping can immediately mitigate land sinking.
Shirzaei and Nicholls called for the research community to move from measurement to understanding implications and supporting responses to address this overlooked hazard.
