Sinking land and subsidence is overlooked as a hazard in urban areas globally, according to scientists from Virginia Tech, US, and the University of East Anglia, UK.
In an invited perspective article for the journal Science, Virginia Tech’s Manoochehr Shirzaei collaborated with Robert Nicholls of the University of East Anglia to highlight the importance of recent research analyzing how and why land is sinking — including a study published in the same issue that focused on sinking Chinese cities.
Results from the accompanying research study showed that of the 82 Chinese cities analyzed, 45 percent are sinking. Nearly 270 million urban residents may be affected with hard-hit urban areas such as Beijing and Tianjin sinking at a rate of 10 millimetres a year or more. Land sinking, or subsidence, results in increased risk to roadways, runways, building foundations, rail lines, and pipelines.
The phenomenon isn’t limited to China: “Land is sinking almost everywhere,” said Shirzaei, 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 US 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.”
Land sinking is mainly caused by human action in the cities. Groundwater withdrawal, which lowers the water table, is considered the most important driver of subsidence, combined with geology and weight of buildings. Recharging aquifers and reducing pumping can immediately mitigate land sinking.
Advances in satellite monitoring revealed the extent of land sinking for the first time, however land sinking is just an observation – more research is needed to allow the prediction of future subsidence. This requires models that consider all drivers, including human activities and climate change and how they might develop over time.
