By: Grace Xie
Everyone has heard of rising seawater, but what about sinking land? Research by Ohenhen et al. in 2025 found that in the 28 most populous US cities – including New York, Los Angeles, Houston, and Boston – 28% of the area is sinking. The sinking of land is called subsidence, and there are different causes.
Groundwater extraction causes many instances of subsidence. In regions such as Houston, Texas, the removal of water from sediment causes layers of sediment to become compact. This particular cause cannot be reversed, as water cannot be pumped back into the already packed clay. Mining is another cause of subsidence. The extraction of resources from the earth leaves the remaining ground vulnerable, particularly when mining voids collapse. However, this type of subsidence can be more relatively easily predicted. Similarly, another type of resource extraction, petroleum and natural gas, also causes subsidence. These are the three primary causes of subsidence that revolve around resource withdrawal.
Among these, groundwater extraction is one of the most prevalent. The population of large cities is growing. In 2024, Houston saw one of the largest population growths out of all US cities and has seen an expanding population for years. Fittingly, Houston is the fastest sinking city in the country. Its subsidence is exacerbated by its location near the coast and extracted oil resources. This isn’t limited to Houston, however. Cities around the country are facing population growth that strains their underground water resources.
Such subsidence has detrimental impacts. Flooding is a large risk that has only been worsened by most large cities’ lower location along the coast. As their elevation decreases, they are more susceptible to the accumulation of rainwater as water tends to flow downhill. Not only that, but they will be increasingly threatened by weaker storms. In addition, the collapse of aquifers can cause fissures in the ground. These are large fractures that can be meters deep and form when the ground can no longer withstand the stress on sediment from removing water.
Although subsidence has many negative impacts, there have also been attempts to reduce its prevalence. Restrictions on groundwater pumping can preserve aquifers and allow them to naturally replenish. While some areas may be able to have water manually returned, it does not apply to every region. Water conservation programs may also bring attention to subsidence and involve everyday citizens. Infrastructure improvements are another solution area. Soil can be injected with different materials such as concrete and resin to fill voids, preventing them from sinking. Cities can also explore methods to reduce the weight of infrastructure on soil.
However, despite these solutions, cities have not stopped sinking. It is clear that greater efforts need to be introduced to stop subsidence and ensure the safety and future resources of civilians. Long-term sustainability must be achieved, and slowing subsidence is a crucial step.
