Virginia, East Coast cities sinking; increased risk to roads, buildings, runways, pipelines

Virginia Beach and Norfolk are sinking – increasing the risk to roads, runways, buildings, rail lines and pipelines, according to a study published today.

In addition to the two cities in Hampton Roads, other major cities including New York, Long Island and Baltimore are outpacing global sea rise level, according to research from Virginia Tech and the U.S. Geological Survey.

“Continuous unmitigated subsidence on the U.S. East Coast should cause concern,” said Leonard Ohenhen, lead author and Virginia Tech graduate student. “This is particularly in areas with a high population and property density and a historical complacency toward infrastructure maintenance.”

Associate Professor Manoochehr Shirzaei and his research team pulled together a vast collection of data points measured by space-based radar satellites and used the information to build digital terrain maps that show exactly where sinking landscapes present risks to the health of infrastructure.

Using satellite imagery, Shirzaei and Ohenhen measured millions of occurrences of land subsidence spanning multiple years. They used the imagery to create high-resolution depictions of the land subsidence.

The new maps show that a large area of the East Coast is sinking at least 2 mm per year, with several areas along the mid-Atlantic coast of up to 3,700 square kilometers, or more than 1,400 square miles, sinking more than 5 mm per year, more than the current 4 mm per year global rate of sea level rise.

“We measured subsidence rates of 2 mm per year affecting more than 2 million people and 800,000 properties on the East Coast,” Shirzaei said. “We know to some extent that the land is sinking.

“Through this study, we highlight that sinking of the land is not an intangible threat. It affects you and I and everyone, it may be gradual, but the impacts are real.”

Critical infrastructures such as roads, railways, airports and levees are affected by differing subsidence rates.

“The problem is not just that the land is sinking. The problem is that the hotspots of sinking land intersect directly with population and infrastructure hubs,” said Ohenhen.

For example, significant areas of critical infrastructure in New York, including JFK and LaGuardia airports and its runways, along with the railway systems, are affected by subsidence rates exceeding 2 mm per year.

“The effects of these right now and into the future are potential damage to infrastructure and increased flood risks,” said Ohenhen.

Virginia Tech and U.S. Geological Survey scientists measured how much the land along the East Coast has sunk and which areas, populations and critical infrastructure within 100 km of the coast are at risk of land subsidence.

Subsidence can undermine building foundations; damage roads, gas, and water lines; cause building collapse; and exacerbate coastal flooding – especially when paired with sea level rise caused by climate change.

“This information is needed. No one else is providing it,” said Patrick Barnard, a research geologist with the USGS and co-author of the study. “Shirzaei and his Virginia Tech team stepped into that niche with his technical expertise and is providing something extremely valuable.”