The question of whether Virginia is below sea level receives a nuanced answer: the state as a whole is not, but its coastal areas are highly vulnerable to inundation due to a combination of geography and geology. The vast majority of Virginia’s landmass sits above the ocean, with a mean elevation of about 950 feet above sea level, defining it as an elevated state. However, the eastern fringe of the Commonwealth, where millions live, lies at an elevation so low that it is acutely susceptible to the rising ocean. This vulnerability is measured against mean sea level, which is the average height of the ocean’s surface measured over a long period.
Virginia’s Variable Elevation Profile
Virginia’s topography is marked by a dramatic contrast between its mountainous west and its flat, low-lying east. The state is divided into distinct physiographic provinces that showcase a wide range of elevation. On its western edge, the Appalachian and Blue Ridge Mountains dominate the landscape, culminating in Mount Rogers, the state’s highest point, which reaches 5,729 feet above sea level.
In stark contrast, the Atlantic Coastal Plain, which includes the Tidewater region, is a nearly flat expanse that slopes gently toward the Atlantic Ocean. This coastal area is where the state’s lowest elevations are found, being at sea level along the Chesapeake Bay and the Atlantic coastline.
The Unique Geography of the Tidewater Region
The Tidewater region, corresponding to the lower part of the Coastal Plain, is the specific focus of elevation concerns in Virginia. This area is defined by the tidal flow of water up and down the coastal inlets and bays, extending about 100 miles inland. While the land surface here is technically above mean sea level, its elevation is low, often only a few feet in many places.
The region is crisscrossed by a network of major river systems, including the James, York, and Rappahannock, which form extensive estuaries that drain into the Chesapeake Bay. This intricate system of water bodies and marshlands means that vast tracts of land are barely elevated above the high-tide mark. For instance, much of the Outer Coastal Plain, which includes the Eastern Shore and the western shore of the Chesapeake Bay, does not rise above 60 feet in elevation.
Geological Processes Driving Land Subsidence
The perception of Virginia’s coast sinking is rooted in two significant, long-term geological processes collectively known as land subsidence. The first is the post-glacial isostatic adjustment (GIA), a slow response of the Earth’s crust to the melting of the massive Laurentide Ice Sheet thousands of years ago. During the Ice Age, the enormous weight of the glacier depressed the landmass beneath it, forcing the land to the south, including Virginia, to bulge upward.
Now that the ice has melted, the land to the north is slowly rising, and the Mid-Atlantic region is gradually sinking back down, or subsiding. This forebulge collapse contributes a rate of subsidence estimated to be around 0.6 to 1.8 millimeters per year.
The second major geological factor is the presence of the buried Chesapeake Bay Impact Crater, formed by a bolide strike about 35 million years ago. The impact created a deep basin filled with rubble and jumbled rock, known as breccia, which is slowly compacting under the weight of overlying sediments. This differential compaction causes the land surface directly above the crater, including the Hampton Roads area, to remain structurally lower and to sink more rapidly than surrounding areas.
The Concept of Relative Sea Level Rise
The unique vulnerability of Virginia’s coast is understood through the concept of Relative Sea Level Rise (RSLR). RSLR is the effective change in water level relative to the land surface, meaning it is the sum of two components: eustatic sea level rise (the actual volume of the ocean increasing) and local land subsidence (the land sinking). In coastal Virginia, the land is sinking at rates that combine with the globally rising ocean, compounding the effect and resulting in one of the highest RSLR rates on the U.S. East Coast.
The Mid-Atlantic region, which includes coastal Virginia, has shown RSLR trends around 4.0 millimeters per year, significantly higher than other coastal regions. This accelerated rate of relative rise has immediate practical implications, causing increased “nuisance flooding” that regularly disrupts coastal infrastructure and daily life.
A local, human-driven factor is the excessive withdrawal of groundwater from confined aquifers like the Potomac. This causes aquifer compaction, which further accelerates the rate of land subsidence in certain areas.