Coastal regions, particularly those with large cities, are highly vulnerable to climate change impacts due to a combination of rising sea levels and population migration to low-elevation coastal areas. This vulnerability is further exacerbated by land subsidence, a significant but often overlooked hazard. This calamitous news was made public in the PNAS Nexus journal from Jan. 24, which highlights an incredibly astounding and looming threat.
The study notes that by quantifying the exposure to subsidence hazards for coastal communities and infrastructure, subsidence rates of 2 mm per year affects a maximum of 2.1 million people, 867,000 properties, and significant infrastructure on the East Coast of the United States. This hazard is a major threat to metropolitan cities such as New York, Baltimore, and Norfolk, whose populations and properties intersect directly with the rising seas.
Subsidence poses immediate, localized challenges to coastal communities, yet it frequently receives minimal attention in public policy and lacks urgent policy interventions. This oversight leads to increased risks for coastal residents, as subsidence amplifies the effects of sea level rise (SLR), potentially tripling the area at risk of flooding in the coming decades.
In the United States, especially along the East Coast, the situation is dire due to the high density of population and infrastructure. These areas face compounded risks from SLR and land subsidence, increasing the vulnerability of people, property, and assets. The state of infrastructure in these coastal regions is concerning, with the 2021 American Society of Civil Engineers (ASCE) report card highlighting the mediocre to poor condition of essential facilities like airports, schools, roads, bridges, dams, and levees. Railways are the only infrastructure deemed to be in good condition. An assessment of 14 coastal states from Florida to Maine reveals an overall poor state of infrastructure. The ASCE report estimates billions of dollars are needed for maintenance backlogs, emphasizing the heightened risk of infrastructure failure due to neglect in these high-hazard areas.
According to the study, coastal communities are increasingly susceptible to multiple hazards, a situation exacerbated by ongoing land subsidence. This is particularly evident along the densely populated and asset-rich US East Coast, heightening the region’s vulnerability to coastal hazards. The study’s findings reveal that an area spanning 2,000 to 74,000 km², encompassing 1.2 to 14 million inhabitants, 476,000 to 6.3 million properties, and over 50% of the infrastructure in major cities such as New York, Baltimore, and Norfolk, is subject to subsidence rates of 1 to 2 mm per year.
Additionally, the study uncovers a significant trend: as subsidence rates increase, the geographic extent of exposure to these hazards correspondingly diminishes. The implications of the analysis are significant for community and infrastructure resilience planning, underscoring the necessity for a strategic shift from reactive to proactive hazard mitigation strategies in the context of climate change.
The railway network on the US East Coast, particularly in New England (which includes Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont), is highly dense and is one of the most extensive in the country. A large portion of this network, around 81% to 99% (which is between 7,452 to 9,221 km out of a total of 9,247 km), and 42% of train stations are experiencing sinking or land subsidence. This subsidence is particularly severe in some areas, with rates of more than 3 mm per year affecting stretches of 41 to 846 km of railway. In New York City, the high number of underground railways (subways) makes the situation riskier due to this subsidence.
When looking at other types of infrastructure along the US East Coast, such as schools, universities, hospitals, airports, dams, levees, libraries, post offices, fire departments, police stations, and nursing homes, it’s found that over 70% of these are also experiencing subsidence. However, less than 10% of these infrastructure facilities are facing subsidence at a rate greater than 3 mm per year. Subsidence poses a particular risk to critical infrastructures like dams, levees, and airports, where even small changes in land elevation can have significant impacts.
What is clear from this study is that the East Coast is in trouble and there isn’t much anyone can do about it. If and when conditions worsen, the entire population living on the east coast will be required to abandon the area and move further inland.
It is unlikely that this scenario will take place within the next century but rest assured that day is coming and when it does, America’s landscape – and its people – will be changed forever.