Shorelines risk floods as sea rises

Oct 20, 2008

Rising sea levels could swamp shorelines of the St. Johns and Nassau rivers within a couple of decades, according to Florida State University researchers.

By Steve Patterson
The Florida Times-Union--October 20, 2008

Their projections show that more than 1,850 acres in Duval County – a bit less than 3 square miles – could be submerged by 2030. That would mostly be marshy, undeveloped property – none at the beach – representing a modest financial loss.

But port facilities at Blount Island and Baptist Medical Center in downtown Jacksonville could be threatened between 2030 and 2080, according to the projections. So could some houses on Black Hammock Island and on western parts of the Trout River, as well as small patches elsewhere.

The value of land lost could range from $10 million to $572 million under widely diverging projections, the most aggressive showing about 29 square miles under water by 2080.

By comparison, Miami-Dade County’s losses in the same period are projected at between $1 billion and $12 billion.

The figures represent the most detailed public effort yet to measure financial impacts of rising seas. The work was done in conjunction with a report on responding to climate change that a state panel delivered Wednesday to Gov. Charlie Crist.

Higher seas also will lead to more destructive storm surges occurring more frequently, said Julie Harrington, director of FSU’s Center for Economic Forecasting and Analysis.

For example, a storm like Hurricane Frances, which roughed up Florida in 2004, would produce up to 36 percent more surge damage in Duval County once water levels rose, the report said.

Rising seas would carry other problems, including more potential for salt intrusion into aquifers that supply drinking water, said Pete Johnson, an organizer on climate change issues for Audubon of Florida.

He said higher water levels would keep drainage systems from working as they were designed, and that birds and other wildlife would lose habitat.

"The report obviously brings it home to Duval County," Johnson said. He promotes steps to reduce greenhouse gas emissions that many scientists have linked to rising temperatures and sea levels. He said Floridians would help themselves by curbing greenhouse gases but also should plan ways to adapt to higher water.

The study examined only three counties – Duval, Miami-Dade and Escambia – in enough detail to identify specific locations that could be inundated. That was done using computerized mapping programs that assigned an elevation to each parcel of property on tax rolls.

In Duval County, that forecast showed beaches holding up quite well. Huguenot Park at the mouth of the St. Johns and parts of the Talbot islands in the Timucuan Ecological and Historic Preserve were at risk, but sea-rise models didn’t reflect the beaches being swamped.

Harrington, who worked on the report with FSU’s Beaches and Shores Resource Center, said beach renourishment projects could be affecting projections for the shoreline. She noted Miami Beach’s oceanfront seemed similarly safe in the forecasts. But Biscayne Bay, which sits landward of the beach, was expected to be severely flooded.

In showing a wide spread in loss estimates, the report reflects uncertainties many scientists feel in trying to predict sea change.

Scenarios ranging from a rise of 4 inches to about 26 inches were treated as potential forecasts for 2080. Two methods for predicting were used.

Floridians should expect some increase, said James O’Brien, an FSU meteorologist who didn’t work on the project and has criticized a number of warnings as overblown.

O’Brien said ocean levels rose in the past century and will continue to do so. He argued sea-level changes will happen more gradually than forecast by many global-warming researchers, although he agreed that warming is occurring.

He said sea-level changes cannot be reined in.

"We ain’t gonna stop it. … It’ll be a foot in this century and a foot in the next century," said O’Brien, who founded the school’s Center for Ocean-Atmospheric Prediction Studies and was appointed the state’s official climatologist in 1999.