COASTAL CHALLENGESReducing Vulnerability to Sea-Level Rise in Virginia

Published 15 October 2024

As the climate changes and sea levels rise, there is concern that sinking coastlines could exacerbate risks to infrastructure, as well as human and environmental health in coastal communities. The Virginia Coastal Plain is one of the fastest-sinking regions on the East Coast. 

While some of the sinking, also known as subsidence, is due to deep Earth processes, much is caused by water being drawn from the confined Potomac aquifer faster than it can be replaced or recharged.

The Potomac aquifer is the source of most groundwater withdrawn in the Virginia Coastal Plain, making it key to understanding how to manage subsidence in the region. To assist partner agencies in managing sinking coastlines, sea level rise, and water resource needs, the USGS created tools to monitor the causes and extent of land subsidence more precisely in the Virginia Coastal Plain. 

The Hampton Roads Sanitation District (HRSD) partners with the USGS to measure the effectiveness of its Sustainable Water Initiative for Tomorrow (SWIFT) program. The SWIFT program cleans wastewater so that it meets drinking water standards and can be used to recharge the Potomac aquifer in an effort to replenish it with clean water and combat land subsidence. 

The recharge process involves multiple layers of advanced water treatment to produce SWIFT Water®, a clean water that meets drinking water standards and is used to recharge the Potomac aquifer through a series of recharge wells, providing a sustainable source of groundwater and potentially mitigating the land subsidence associated with overuse of the aquifer. HRSD wants to know if these efforts are having the desired effect and relies on USGS science to study this. 

Jamie Mitchell and Dan Holloway of HRSD report that the SWIFT project would not be possible without the USGS Coastal Plain models of the Potomac aquifer, which are essential for understanding how the aquifer responds to withdrawals and how it can respond to recharge. 

“There’s been a hand-in-glove relationship between USGS science and our efforts,” said Holloway.  

Holloway has been working as a hydrogeologist for more than 25 years, and he and his colleagues rely heavily on the science performed by the USGS on the aquifer system. The USGS reports have been the definitive reference on the groundwater system for decades. 

Greg Connock, a USGS Geologist, is committed to studying the precise sources of land subsidence on the Virginia Coastal Plain.  

One of the most important tools Connock and his team use to measure subsidence is an extensometer, which USGS Hydrologist Jason Pope describes as “a ruler in a pipe that measures how much land around the extensometer is moving.”