Sea Level Rise

Around fifteen thousand years ago rising seas flooded the Susquehanna River and began to carve out what is now the Chesapeake Bay. Today, sea level rise threatens many of the same Bay habitats it helped to create.

During the 20th century sea level rose about a foot in the Chesapeake — nearly twice the global average and about double the rate of the past several thousand years. Exacerbated by land subsidence — the lowering of land caused partly by withdrawal of groundwater for human use — rising seas forced shorelines to retreat, spurred release of sediments into the Chesapeake, and drowned many tidal wetlands and low-lying coastal lands. Several islands that once dotted the Chesapeake’s coast — including Sharps, Spry, and The Three Sisters — have now forever slipped beneath the surface.

Future Sea Level Rise & Its Effects on the Chesapeake Bay Ecosystem

In the 21st century experts predict that sea level rise in the Bay, fueled by global warming and melting sea ice, will exceed rates of the past century by two or three times. By 2030 sea level in the Bay region may be at least 6 inches higher than today. Effects will vary across Maryland’s diverse landscape, but are expected to include drowning of wetlands, saltwater intrusion in low-lying areas, and erosion — all with significant environmental implications. (Click here for a look at what might be in store for the Chesapeake Bay area.)

Losing wetlands will mean the loss of critical habitat for many Bay species. Wetlands and their vegetation also serve many ecosystem functions, including protecting the coast from storms and taking up excess nutrients. As saltwater intrudes into freshwater tributaries it will alter habitats and food web dynamics. And erosion’s release of sediments means trouble for Chesapeake water quality. Particles can smother the Bay’s underwater grasses, eliminating a natural buffer against further erosion.

Development along the coast also faces serious threats from expected increases in storm surge and coastal flooding. Small gains in wave height due to sea level rise translate into large increases in wave energy. Water surges farther inland during a storm and hits harder. Hurricane Isabel proved the point when it flooded areas unscathed by a 1933 hurricane of similar strength and direction. With more and more people living in vulnerable, coastal areas — the Chesapeake Bay watershed is the second most populated watershed in the country — the potential for substantial property losses mounts.

Response

To stabilize the land and hold rising seas at bay, coastal areas are often armored with bulkheads, sea walls, rip rap, and other methods of “shoreline hardening.” But these responses can come at at cost — both financial and environmental. While in some cases they help reduce erosion and prevent loss of public and private property, they are often blamed for degrading the nearshore environment and causing the loss of the very habitat they are meant to protect.

The Maryland Department of Natural Resources (DNR) Coastal Zone Management Division is working to address the impact of rising sea levels through programs focused on planning, research, and public outreach. In October 2000, DNR published “A Sea Level Rise Response Strategy for the State of Maryland” that addresses the primary impacts of sea level rise. It notes that “the State must recognize that a ‘do nothing approach’ will lead to unwise decisions and increased risk over time.”

With warming temperatures widely regarded as the cause of accelerated sea level rise, reducing global emissions of greenhouse gases will be a key part of the long-term response. But experts note that with the effects of climate change already set in motion, even significant reductions in global emissions will have little effect on sea level rise by 2030.

Useful Links

Visualizing Sea Level Rise in Maryland's Chesapeake Bay

A Sea Level Rise Response Strategy For the State of Maryland (DNR)

Global Warming and the Bay
Chesapeake Quarterly, Volume 5, Number 3, 2006

Vanishing Lands
Marine Notes December 1992

Erosion Control (DNR)

Climate Action Plan (pdf)
Maryland Commission on Climate Change