South Florida water managers weigh costly consequences of sea level rise

For millions of South Floridians, life on a peninsula means melting icecaps in Greenland aren't just something for polar bears to worry about.

South Florida's coastal flood-control structures, counted on to protect low-lying communities from getting swamped, already are at risk from sea level rise due to climate change, according to scientists for the South Florida Water Management District.

In the coming months, the district's governing board will be asked to endorse more scientific studies and potentially costly flood-control construction projects aimed at preparing for the rising sea levels expected to come.

A district proposal outlined Tuesday calls for the agency over the next five years to buy more land for flood control, design improvements for 50-year-old drainage structures and start building pumps that could keep discharging stormwater out to the ocean even as sea levels continue to rise.

While politicians and world leaders debate the causes of climate change and how to respond, district scientists are adopting a "no-regrets strategy" to get ready, even if the worst-case scenarios don't come to pass.

"This is an issue of global importance that will have regional impacts," said Jayantha Obeysekera, who is leading the district's response to climate change and sea level rise. He briefed the district board Tuesday. "All aspects of water management would be impacted."

An increase in carbon dioxide and other greenhouse gases in the Earth's atmosphere are trapping more of the sun's heat, leading to climate change — blamed for higher temperatures that are projected to increase the rate of sea level rise.

Manmade pollution produces more of those heat-trapping greenhouse gases.

Sea ice, glaciers and snow cover around the world all are shrinking as temperatures rise, Obeysekera said.

The district is anticipating sea levels to climb 5 to 20 inches during the next 50 years.

High water levels at times already are creating problems for some of the floodgates, spillways and drainage canals that protect South Florida from flooding.

South Florida now has periods of extreme high tides, when water levels rise higher than the point where stormwater from coastal drainage canals normally gets dumped into the sea.

When that happens, floodgates stay closed, increasing the flood risk if those drainage canals overflow. That would worsen if sea levels rise.

Overwhelmed coastal drainage canals would have a "domino effect" on the rest of South Florida's drainage system, according to Carol Wehle, water district executive director.

If there's insufficient room for water in drainage canals, then there's not enough room for water coming in from community drainage systems. Those community systems help keep inland neighborhoods dry.

"The capacity … of the system is going to be negatively impacted by sea level rise," Wehle said.

The district has so far identified 28 flood-control structures along the southeast coast and six along the west coast most at risk to rising sea levels.

The first three are the S27, S28 and S29 facilities in northern Miami-Dade County.

New pumps are proposed to push stormwater into the ocean while keeping floodgates closed to hold back the elevated seas.

Cost remains a hurdle to getting that done. The current proposal would begin work by 2015. Each one cost "tens of millions of dollars," Obeysekera said.

Another threat from rising sea levels is more saltwater seeping in underground and contaminating drinking water supplies. South Florida has coastal well fields that through the years have had to shut down or reduce pumping due to saltwater intrusion.

Water utilities in Lake Worth, Hallandale Beach and Lantana have been among the most at risk of saltwater intrusion.

If that continues, it means increased costs to find new drinking water supplies or to switch to more costly water treatment processes — both of which would mean higher water bills for South Florida residents.

In addition, the Everglades can expect to suffer from an influx of saltwater.

Sea level rise is expected to affect the southern end of the Everglades by increasing coastal erosion, reducing mangrove forests, pushing migrating wading birds northward, increasing peat collapse and raising salinity levels in freshwater marshes that could result in fish kills and loss of wildlife habitat.

The state and federal government are in the midst of investing billions of dollars in Everglades restoration. Some contend that those restoration projects should be reconsidered due to the expected damage from sea level rise.

Others counter that restoring more of the stormwater flows that once naturally reached the Everglades will counterbalance the effects of climate change.

"It's critical to act fast enough," said Jane Graham of Audubon of Florida. "Fight water with water."

Computer modeling is being used to try to chart which areas are most at risk of flooding from sea level rise.

During the coming year, the district plans to further identify water-management projects affected by sea level rise; complete reports on trends in sea-level rise and climate change; and finish an analysis of the saltwater-intrusion monitoring system.

The sea level rise is not really in dispute, said district board member Jerry Montgomery, pointing to melting glaciers and ice sheets from Greenland to Antarctica. The question, Montgomery said, is the rate of rise and how much it will affect South Florida.

"It is clearly melting and it is clearly melting at a faster rate," Montgomery said.

Andy Reid can be reached at abreid@SunSentinel.com or 561-228-5504.

Source: http://www.sun-sentinel.com/news/palm-beach/fl-sea-level-rise-south-florida-20101109,0,5651053,full.story

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