|May 07, 2018|
Aging flood-control systems can't protect South Florida from sea-level rise
|The way most Floridians will first feel the effects of sea-level rise probably won't be from some catastrophic wave crashing over a sea wall. More likely, it will be flooding, the water covering your shoes, your street, your doorstep.|
Flooding is already heavier in South Florida. And it will get heavier still as the sea level continues its inexorable rise --- gaining at least 2 feet by 2060 and rising faster after that, according to scientists' mid-range projections.
Our main protection is a flood-control system built 50 to 70 years ago, long before climate change was even imagined. It's clear that this aging system will need serious, and expensive, upgrades.
Congress has yet to provide the money for a much-needed study of how to do that. It's galling that lawmakers gave the Northeast $20 million for a flood-control system after just one storm, Superstorm Sandy. Yet for all the hurricanes and tropical storms we've endured, Congress has yet to fund a flood-control study for our region that it authorized in 2016.
Florida, of course, has a long familiarity with the engineering of water. An epic system of drainage canals dried out the Everglades sufficiently for South Florida to grow to be a major population center. A system of wells and underground water storage allows 6 million people to slake their thirst.
When the ocean's volume expands, as it's bound to do --- the seas having absorbed 80 percent of the heat from global warming, and with Antarctica and Greenland melting --- the water won't just lap over Florida's sea walls. Salt water will push its way up, under our feet, through the peninsula's foundation of porous limestone. The seawater will threaten underground drinking water.
The South Florida Water Management District (SFWMD) supervises some 2,000 miles of canals --- major channels carrying water from Lake Okeechobee to the ocean. It maintains gates near the coast to keep the canal water level higher than the sea level to allow water to flow out from the cities to the ocean when it floods and to keep saltwater from reaching inland.
The system won't perform as designed when seas get higher and managers are forced to close the gates more often.
If the canals can't flow outward, where's the flood water supposed to go? This is already happening in Miami-Dade County, where the canal levels and tide fluctuations are "already very close," according to a 2015 report from the Southeast Florida Regional Climate Change Compact.
It's obvious that the gates and other structures are going to need to be enlarged or otherwise re-designed. But by how much and at what cost?
When the SFWMD studied the problem in 2009, 20 flood control structures were deemed vulnerable if the sea level rises just half a foot --- which is now expected in less than 15 years. A recent Florida Atlantic University study concluded that a half-foot rise would cripple about half of South Florida's flood control capacity.
We need a deeper, more current study. And Congress has authorized one. The 2016 Water Resources Development Act orders the U.S. Army Corps of Engineers to study 10,000 miles of coastline along the south Atlantic and Gulf Coast "to identify the risks and vulnerabilities of those areas to increased hurricane and storm damage as a result of sea level rise."
Encouraging words. But the Corps is still waiting for the money. Eric Bush, the Corps' South Atlantic Division planning chief, says the delay was expected; it's just how Congress works.
Still, it's vexing. This study will be vital for understanding where flood risk is most severe. It will help the state and localities, as well as the Corps, plot strategies for making our region more resilient. This could mean fortifying sea walls, raising streets, adding pumps, upgrading sewage systems, renourishing beaches and creating mangroves, marsh and seagrass habitats.
The SFWMD, to its credit, is making regular checks of its flood-control system and runs frequent scenarios to figure out how soon it will have to do more construction or make adaptations such as re-routing water.
But it's not just the SFWMD and Corps that must act. Our region has thousands of miles of secondary canals, managed by local drainage districts --- and even smaller canals under such entities as homeowner associations. Unless improvements are made in these, your street will flood no matter how well governments improve the major canals.
The time to be thinking about this is now. As the National Research Council has said, "Every dollar spent before an event saves four to five dollars in reconstruction costs after."
Fortunately, local officials do have their eyes open. The four-county Climate Change Compact is doing an exemplary job of beginning the long, difficult, expensive task of adapting to a future of frequent flooding.
What we can't afford is a governor who denies climate change and a federal government that won't prioritize the public investments that must be made if low-lying coastal regions like ours are to survive the brunt of rising seas.
We challenge every statewide and national leader, those now serving and those seeking office, to act. A good place to start would be to shake loose the money tree, and secure for the Army Corps of Engineers the funds to assess the coastal storm and flood risks we know await us.