Monday, April 21, 2014

Florida communities prepare for rising seas

WASHINGTON — While the nation looks for solutions to the problem of rising sea levels, some coastal communities in Florida are taking action to save themselves from sinking into the ocean.

Hallandale Beach is preparing to pump excess groundwater into an aquifer. Fort Lauderdale has raised a coastal roadbed and is installing one-way "tidal valves" that flush water down storm drains but block seawater from rising back up.

And coastal communities farther north, from Palm Beach County to the Space Coast, are developing plans that would concentrate housing, businesses, water plants and wells on higher ground, less vulnerable to the rising sea.

"Florida is ground zero for sea-level rise," U.S. Sen. Bill Nelson told the Senate while announcing a field hearing in Miami Beach on Tuesday, which is Earth Day. "We've got quite a story to tell."

Nelson plans to highlight Florida's adaptations to its changing coastline when the Senate Subcommittee on Science and Space meets at 10 a.m. at Miami Beach City Hall.

Low-lying Florida, much of it barely above sea level, is among the first victims of global warming, which scientists say leads to rising seas. Nelson and experts on climate change see the state emerging as a model for how to deal with the inevitable consequences.

The seas already have risen 8 to 10 inches over the past hundred years, creeping closer to structures built near the ocean, said Nancy Gassman, acting assistant director of public works in Fort Lauderdale.

"It makes a difference about how we look to the future and build new infrastructure, recognizing that sea-level rise needs to be considered," she said.

The response dovetails with measures designed to deal with extreme high tides each fall and occasional storms, such as Hurricane Sandy. That storm severely eroded South Florida beaches in November 2012, crumbling 2,000 feet of one lane of State Road A1A along the beachfront.

With future storms and rising seas in mind, engineers propped up the restored roadway with sheets of metal that were driven into the ground until they hit bedrock. They raised the roadbed while sloping it to drain water.

"We're putting it back not just the way it was but in a way that enhances its resilience to future events," Gassman said.

A pilot project to install one-way tidal valves — which send groundwater down storm drains but won't let water rise back up — has proven successful, she said.

The city also is considering stormwater parks — open spaces lined with plants, about the size of a few housing lots — where groundwater can be pooled to prevent flooding on surrounding property. And it is considering "bio-swales," narrow strips along roadways that are lined with vegetation and porous material to suck water more quickly below the surface.

Flat, low-lying Hallandale Beach already faces the threat of salty seawater flowing into its freshwater supply, a problem aggravated by sea-level rise.

The city once planned to spend $10 million to move its water system away from the sea, but leaders instead decided last year to pump surface water into an underground aquifer no longer used for drinking water.

"What we realized is that this is a good strategy not only for our drainage but in light of sea-level rise," said Earl King, assistant utilities director in Hallandale Beach.

Some communities farther north are beginning to assess the impact of rising seas while considering ways to protect existing buildings and shift new development to higher ground.

"As we build for the future, we have to take sea-level rise into account and fortify existing infrastructure, such as wells and water facilities," said Palm Beach CountyCommissioner Steven Abrams. "And we might need more frequent beach re-nourishment."

Satellite Beach, sitting on a barrier island along the Space Coast, cannot protect itself behind dikes or sea walls because water would seep through the porous limestone beneath it.

The city eventually may have to abandon some homes along the oceanfront and move toward multi-family housing complexes on higher ground, said John Fergus, a member of the city's planning advisory board.

"People would still buy homes, but do it with the understanding that this place won't be here 300 or 400 years from now," he said. More