A team of Virginia Tech scientists say parts of the East Coast, especially densely populated coastal areas in the mid-Atlantic region, are sinking faster than originally thought, putting at risk not only wetlands and agricultural areas, but also the structural integrity of the roads. , airports, dams and other types of built infrastructure.
The researchers, a team from Virginia Tech’s Earth Observation and Innovation (EOI) lab, conclude that more than half of the infrastructure in cities like New York, Baltimore and Norfolk, Va., is located in areas that they sink between 1 millimeter and 2 mm annually. . But while 70% of the infrastructure on the US East Coast is on land that is experiencing some level of subsidence, less than 10% is on land that is sinking more than 3 mm per year.
However, in some areas, such as Charleston, SC, the ground subsides by nearly 4 mm per year, where flooding is a real problem, says Leonard Ohenhen, a Virginia Tech geophysicist and one of the co-authors of the study.
“Sinking is a pernicious problem, highly localized and often overlooked in comparison to global sea level rise, but it is an important factor in why water levels are rising in many parts of the eastern United States,” he says.
The research, funded by the National Aeronautics and Space Administration (NASA), points to the need for engineers, builders and urban planners to focus more on the double conundrum posed by the sinking earth while the level of the sea is also increasing, the researchers said. .
“Our analysis has far-reaching implications for community and infrastructure resilience planning, emphasizing the need for a targeted approach in transitioning from reactive to proactive hazard mitigation strategies in the ‘era of climate change,’ the authors of the study concluded PNAS Nexusa publication of the National Academies of Science.
Satellite data statistics
Subsidence occurs when the land begins to sink as a result of aggressive groundwater extraction, as well as the construction of dams and levees that prevent sediment from replenishing the land along rivers and streams. The result may lead to increased flooding in areas already suffering from sea level rise.
The EOI Lab research team analyzed data from U.S. Geological Survey (USGS) satellites and ground-based GPS sensors to map vertical and horizontal land motion along the East Coast from Florida to New England between 2007 and 2020. They also assessed the extent to which infrastructure in those areas might be at risk.
They found that along the East Coast, between 77% and 99% of interstate highways, 81% and 99% of rail systems and more than 800,000 properties are at risk of subsidence. This is a particular challenge in low-lying areas such as Hampton Roads, Va., and Norfolk, Va., which already experience more than 2 mm of subsidence annually and deal with frequent flooding of transportation infrastructure, reported the authors of the study
Evenly sinking land poses less risk than unevenly sinking land, the authors wrote.
“Unmitigated, this subsidence can slowly but surely compromise the structural integrity of urban infrastructure and exacerbate other hazards (e.g., flooding), contributing to socioeconomic losses,” the authors wrote, adding, “Beyond the direct impacts , coastal subsidence is a major driver of current and future hazards, amplifying the impacts of climate change-driven sea level rise. Consequently, understanding the impact of continued subsidence in coastal zones is essential to move from reactive to proactive climate change mitigation strategies.”
