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Can D.C. survive 'unstoppable' ice melt?

Friday - 5/16/2014, 5:13am  ET

Jefferson12ft(Nickolay Lamm/Climate Central)
Artist's rendition of the Jefferson Memorial, if seas rose 12 feet (Photo illustration credit: Nickolay Lamm, Data: Climate Central)
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WASHINGTON -- What will become of the nation's capital?

The huge West Antarctic ice sheet is slowly collapsing, and two groups of scientists say the melting is now an unstoppable event.

Melting ice will cause sea levels to rise higher than initially projected, which is cause for concern for D.C.-area scientists and local urban planners.

The rising seas will affect local treasures, including the Chesapeake Bay and the country's iconic monuments along the National Mall.

"We've reached the point of no return," says Brenda Ekwurzel, senior climate scientist with the Union of Concerned Scientists. "We can expect by the end of the century, according to the National Climate Assessment, anywhere between one and five feet of sea-level rise."

That's only the beginning.

Scientists say the rise in sea level could reach 12 feet, which would bring water perilously close to the monuments built on the low-lying land near the Potomac River.

Both the NASA-funded University of California at Irvine and University of Washington studies had similar findings.

"We might be taking those paddle boats in the Tidal Basin right up to the base of the Jefferson Memorial, getting out, and walking up the steps," says Ekwurzel.

Currently a sea wall and large plaza area separate the river from the steps of the memorial that honors the third U.S. president.

Ekwurzel says 2003's Hurricane Isabel, which created a storm surge of 11 feet -- prompting a week of devastating flooding in D.C., Annapolis, and Baltimore -- provided a peek into how the landscape and life in the area would be affected by dramatically higher waters.

"The Martin Luther King Memorial, and the FDR Memorial, they're very close to the Tidal Basin elevations," says Ekwurzel. "They're built of stone, so they can withstand temporary floods, but (with) permanent flooding we would have to think about 'How do we have access to these memorials?'"

The U.S. Army Corps of Engineers is close to finishing an improvement to its 1939 levee that prevents flooding from the Potomac River onto the residences and businesses around the National Mall.

Stretching from the Lincoln Memorial, across 17th Street, to the Washington Monument, the current levee requires the placement of sandbags and jersey walls during a flood event.

In late summer, the long-delayed project will replace the current closure system with a more reliable post and panel system that stands about nine feet high, says Chris Augsburger, spokesperson for the Corps of Engineers' Baltimore District.

The risky future of Chesapeake Bay

Bill Boicourt, professor of oceanography at University of Maryland's Center for Environmental Science, says the effect of the rising Chesapeake Bay would be especially challenging for the Norfolk, Virginia area.

"Norfolk is the second-most vulnerable city in the United States, behind New Orleans," says Boicourt. "We all know the vulnerability the Chesapeake has."

Chesapeake Bay is approximately 200 miles long, surrounded by Maryland and Virginia.

"The relative sea level-raise is twice the global rise, simply because the land is sinking," says Boicourt.

Earlier U.S. Geological Surveys concluded the Chesapeake has the highest rates of relative sea-level rise on the East Coast, caused by the combination of rising seawater levels and "land subsidence," or sinking land.

"Chesapeake Bay is particularly vulnerable to hurricanes that happen to come on the western side of the bay," says Boicourt.

Scientists say sea levels will not rise quickly, but the rise can't be reversed. A reduction in greenhouse gas emission could slow the melt, according to scientists.

Preserving Old Town Alexandria

Old Town Alexandria has endured decades of flooding problems, based on its proximity to the Potomac River.

The city is in the midst of implementing a waterfront landscape and flood mitigation plan.

Emily Baker, director of project implementation for the City of Alexandria, says the worst flooding is along The Strand, where the Potomac currently pours into the streets during significant rain events.

"We've really identified the area between Duke and Queen Streets as the lowest areas," says Baker.

Baker says the current plan doesn't eliminate all risk of flooding, but would protect the city from 90 percent of the flooding that presently occurs.

"What we're proposing to do is raise the bulkhead along the river to about two to three feet higher than what the elevation is there," says Baker.

Baker says the project aims to stem what would be referred to as a "10-year storm."

Planners considered, then nixed, building more severe deterrents that could have provided more protection against flooding.

"We didn't want to build something that cut off the city from the water in our historic Old Town area," says Baker. "We wanted it to still function as a place for residents and visitors to go."

Clearly, the promise of considerably higher water levels limits the lifespan of the current mitigation plans.

"We'll be keeping a good eye on that, and see if there are incremental improvements that we can make to deal with the situation," says Baker.

Ekwurzel, of the Union of Concerned Scientists, says the relatively narrow area of the Potomac River gives reason for hope in preserving the Old Town and National Mall landmarks: "This is an area where we could think of temporary structures that might inflate, or engineering structures that might move and close off the storm surge."

But the collapse of the giant West Antarctica ice sheet isn't just a heavy storm.

"When you have this level of sea-level rise, what are we going to do?" asks Ekwurzel. "We don't want to necessarily decrease navigation to the ocean."

When will the ice melt affect the Washington area?

With the "if" removed from the "if it happens, when" question, local experts say there is no cause for panic, but for a more concerted effort to minimize the effects of the massive ice melt.

"The worry to our children is, not only will this continue, but it might accelerate pretty fast," says Boicourt, of the University of Maryland.

"We do have at least a century to prepare," says Ekwurzel, "and in the case of the worst-case scenario, maybe a couple centuries. We should plan on one to four feet of sea-level rise happening over the course of this century, as a conservative estimate."

While the challenges facing the Washington area are severe, other metropolitan areas are at higher risk.

"The good news is that (the D.C. area) could be protected with some kind of barrier if that was necessary, the area's not too large," says Boicourt.

"It would be very expensive, but it's not like trying to enclose New York City, which is almost unenclosable."

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