Geologist Harold Wanless stands in front of a salinity-control barrier near the Miami airport. Many such structures, which release floodwater without letting in saltwater, will cease to function in a few decades.
by Dan Weissmann Tuesday, February 10, 2015 – 15:22
Greater Miami is a place where the idea of not having enough water seems completely bananas. South Florida receives about 60 inches of rainfall a year, and groundwater is more than plentiful. Keeping streets and homes from getting flooded with freshwater is still a huge job here.
But rising sea levels change things in unexpected ways, and seawater threatens to turn the drinking water salty. In some places, the ocean has already made good on that threat. And the problem is going to get worse.
To illustrate, Harold Wanless takes me out behind a car-rental place by the Miami airport. He’s a University of Miami geology professor who has spent decades studying how sea levels change, from the ice ages to today.
There’s a lot to see and hear in this little spot: two highways converging, planes flying overhead, Miami Jai-Alai, the Pink Pussycat Strip Club. (“Everything you want near an airport,” says Wanless. “I guess.”)
He’s chosen this location for two reasons. First, this entire area used to be part of the Everglades. “When they drained the Everglades here, water levels dropped about 7 feet,” he says. “And voila! You have an airport.”
Second, in this particular spot, a canal comes under those highways and hits a little barrier. This structure, several miles inland, is the boundary between the salty ocean water, and South Florida’s freshwater supply.
That water supply isn’t contained underground. “It goes right up to the surface,” says Wanless. “So, yeah – this is our aquifer. This is our water.”
And this is where the goal of managing freshwater flooding meets the threat of rising seas.
One of this little barrier’s main jobs is actually to get rid of freshwater after heavy rains, to prevent flooding. The gate opens and rainwater building up behind the dam spills out to sea.
There are dams like this all over the region. But for them to work – for the freshwater to spill – the seawater has to be lower than the gate.
Global Climate Change