As a historic supermoon glows over Miami Beach this week, record-breaking king tides boosted by sea-level rise are swamping the barrier island. In what has become an October tradition, residents have to wade through pools of deep standing water on sidewalks and in parking lots to go about their daily lives.
Those rising floods are damaging cars and negatively affecting businesses, but what if that water is also a major health hazard?
The fact is, those rising tidal floodwaters have never been tested for pollutants. Some scientists say the flooded streets could be full of human waste leeched through aging sewer systems, although the City of Miami Beach strongly disputes that.
"Whatever you do, don’t come into contact with the floodwaters,” says Florida International University hydrologist Henry Briceño, who participated in a National Oceanic and Atmospheric Administration (NOAA) study on water pumped from the city's streets and back into Biscayne Bay.
Briceño's study, which was published in February, showed unacceptably high levels of human waste in the floodwaters being pumped back into the bay by a $400 million anti-flooding system that's still being installed around Miami Beach. NOAA's researchers found highly elevated levels of nutrients, hydrocarbons, and bacteria in the untreated storm water; those pollutants can lead to algae blooms and kill marine life.
Are those same pollutants swimming around in the storm water sitting on city streets this week? Briceño suspects they are.
“What happens is that the soil under Miami is very porous and the sewer system is not very good, so any kind of pollutant goes into this lens of fresh water that floats atop the salt water. When the tides rise, that dirty fresh water comes up and fills the streets,” he says.
But Miami Beach officials push back hard against that idea. Mayor Philip Levine attacked NOAA's study about wastewater flowing into the bay, calling it "sloppy science."
Roy Coley, Miami Beach's infrastructure director, says there's no way the city's sewers could be leaking human waste into the king-tide waters filling city streets this week.
“Most of the system works under negative pressure and is actually underwater at high tide anyway, so the problem we have is with liquid actually getting into the sewer system, not out of it,” he says.
Human waste or not, the city does agree with Briceño on one point: It's not a good idea to come into contact with king-tide water if you can help it. Miami Beach has issued numerous warnings to residents about the safety of floodwaters every year.
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“All storm water carries pollutants," says Margarita Wells, the city's environmental resource manager. "We try to communicate that to our residents through social media and email, but the real solution is clearing it out of the public rights of way before there’s any kind of negative health effect.”
This year's king tides are expected to peak today and tomorrow as the moon makes its closest approach to Earth since 1948. Waters have swamped sidewalks and parks, and one visitor even snapped a pic of an octopus in a parking garage:
But nuisance sunny-day flooding isn't limited to king tides. By 2030, thanks to climate change, scientists expect such floods to hit Miami Beach more than 50 times per year.