South Carolina scientists suggest raising coastline

Method offers flood protection
Scientists at Clemson and Georgia Tech say it could be possible to raise the coastline by injecting sediment-laden slurry into fractures beneath the ground.

CHARLESTON, S.C. — People along the coast have a few options in an era of global warming expected to bring more frequent, intense storms and the kind of devastation recently seen with Superstorm Sandy: They can move back from the shore, elevate buildings or build levees to keep the floods at bay.


But a pair of scientists at Georgia Tech and Clemson suggest another alternative, although it sounds a bit like science fiction. Their research shows it is possible to raise the coastline itself.

Leonid Germanovich, of Georgia Tech, and Lawrence Murdoch, of Clemson, both environmental engineers, have worked out the math and are proposing a method of flood protection they call SIRGE, or solid injection for raising ground elevation.

They envision injecting sediment-laden slurry into hydraulic fractures in the ground. If repeated in adjacent areas and over a wide area, it works to push up the surface of the earth. They suggest a series of pumps and wells to force the material underground.

The proposal, and the extensive scientific equations that accompany it, were published in 2010 in the prestigious Proceedings of the Royal Society.

The Society, dating to the 1660s, is the national academy of science in the United Kingdom and has 1,400 fellows worldwide.

After a 1900 hurricane devastated Galveston, Texas, killing an estimated 8,000 people, the city rebuilt after the ground level was raised as much as 17 feet.

“It’s been shown with the Galveston example, if you can increase elevations, that is your best bet in safeguarding areas against flood,” Murdoch said.

While you can’t elevate every building in a community, another approach might be to raise the level of the ground below it. A similar technique has been used on smaller scales.

For example, when a tunnel is drilled under a city, a technique called compensation grouting is used above it, injecting material to keep the surface above stable so it doesn’t sink. Perhaps the best-known example is the grouting done under Big Ben in London when a subway tunnel was built, Germanovich said.

Using SIRGE, the sediment likely would need to be projected 300 or more feet below the surface. The paper suggests that, in theory, at the upper end, it might be possible to raise the coast 10 meters, about 33 feet.

“From what the people who work on these issues are saying we should expect higher sea levels and larger intensity storms,” Murdoch said. “If that is the case, then the problems we saw with Sandy are going to be more frequent.”

The Southeastern Coastal Climate Network calculates that in the past 90 years, the sea level has risen a foot in Charleston. It’s worse elsewhere.

The U.S. Geological Survey reported last summer that in the 600-mile swath from Boston to Cape Hatteras, sea levels are rising much faster than in other areas around the globe. Since 1990, the sea level has risen almost 5 inches in Norfolk, Va.

Murdoch said that currently, levees are the go-to technology for dealing with sea level rise.

The problem, he said, is levees tend to fail. “In view of that, we need another technology,” he said.

Both scientists agree there is an awful lot to be worked out in attempting to raise the ground level – everything from what it might cost to how it would be carried out.



Sat, 11/25/2017 - 00:06

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