Southeast
An example of "Sunny day" (nuisance) flooding in Miami Beach. Photo credit: Miami Dade DERM.

Climate Change: More High-Tide Flooding Is On Its Way For South Florida

As surely as the seasons, the water will come, a silent surge that in 30 years could mean up to 55 days annually where South Florida streets become streams and storm grates bubble backwards, according to a new report released Wednesday.

The federal analysis of high tide flood events in 2018, which includes a forecast through 2050, is a yearly reminder that sea levels are rising so that future tidal overruns could increasingly be triggered by nothing more than an untimely shift in wind during a full moon.

Called "nuisance" or "sunny day" flooding, tidal inundations most often occur in South Florida during the fall king tide cycle -- a function of a slower Gulf Stream current, warmer waters and lunar alignment.

The National Oceanic and Atmospheric Administration changed how it measures high tide flooding last year in an attempt to assess more severe vulnerabilities nationally. That change resulted in no days meeting the flood criteria last year as measured by the official gauge at Virginia Key near Miami.

Still, 30 record high tide levels were broken at Virginia Key in 2018, according to Brian McNoldy, a senior research associate at the Rosenstiel School of Marine and Atmospheric Science.

Six days surpassed the National Weather Service's flood threshold.

And Petty Park in West Palm Beach was under brackish Intracoastal water during a November full moon that also seeped water into parking lots, over marina docks and onto streets from Boca Raton through Jupiter.

"The king tides have come on stronger here and are hopefully moving out," said West Palm Beach resident Lila Young in late November. "My neighbor's back yard and the Petty Park are full of water, and, sadly, much debris."

Why change the new measurement?

William Sweet, an oceanographer with NOAA's Center for Operational Oceanographic Products and Services, said the new measurement raises the bar on flooding to assess deeper more severe events.

"In some cases, it's more in tune or better calibrated to what folks are seeing, but in South Florida's case, it might be undercounting the current state of flooding," Sweet said. "It's trying to compare apples to apples."

Future reports might include sub thresholds that better represent specific areas, Sweet said.

According to Wednesday's report, sunny day flooding in South Florida is forecast to occur 10 to 55 days per year by 2050, and two to five days per year by 2030. The steep range in days by 2050 takes into consideration greenhouse gas emission mitigation efforts at lower and higher levels.

"The ocean is now at the brim, clogging storm water systems and routinely flooding local coastal communities with sea water with no storm in sight," Sweet said. "The impacts are here and now."

Sweet predicts a 190 percent increase in high tide flooding along the country's southeast coast, with variations that include the subtle elevation changes around South Florida.

Palm Beach County is less vulnerable to sea level rise than Broward and Miami-Dade counties with fewer canals bleeding saltwater inland and a slightly higher elevation. The mean elevation is about 15 feet above sea level but slopes up to an ancient coral ridge at the coast that puts President Donald Trump's Mar-a-Lago mansion on Palm Beach out of reach until sea level rise creeps above five feet.

"Palm Beach County is higher," said Boynton Beach sustainability coordinator Rebecca Harvey. "A few feet can make all the difference."

Boynton Beach is part of the Southeast Palm Beach County Coastal Resilience Partnership, which includes Lake Worth Beach, Lantana, Hypoluxo, Ocean Ridge, Briny Breezes, Gulf Stream, Delray Beach, Highland Beach and Boca Raton.

How high and fast will it rise in South Florida?

The partnership has received two grants -- $72,000 and $75,000 -- from the Florida Resilient Coastlines Program, which is a Florida Department of Environmental Protection initiative. The first grant was used to compile an inventory of assets based on geographic information systems (GIS). The partnership will soon put out a competitive bid to conduct a multi-city climate change vulnerability assessment using the inventory information.

"All of the cities have been thinking about resilience and sea level rise on some level," said Harvey, who was hired to her position in 2017. "We have the ability here of learning from what Miami-Dade and Broward are doing and experiencing."

Global sea level rise is about one inch every eight years, Sweet said.

But the Southeast Florida Regional Compact on Climate Change stresses that South Florida's sea-level rise could be faster than the global rate because of changes in the Gulf Stream current.

The compact is projecting 6 to 10 inches of sea-level rise by 2030 and 14 to 26 inches by 2060 (above the 1992 mean sea level).

In the long term, the compact projects 31 to 61 inches of sea-level rise by 2100.

"It hasn't come to where we are looking at retreat, but we are looking at the critical infrastructure and what we'll need to do, where roadways should go, and whether we'll need to move anything," said Poonam Kalkat, director of public utilities for the City of West Palm Beach. "We are looking ahead 20 years and more."

While Florida has long been considered ground zero for climate change, the coastal Mid-Atlantic and Northeast were the key focus in the Wednesday's high tide report with more active ocean patterns causing higher flood rates.

Boston, which experienced 19 tidal flood days last year, could see 95 by 2050. New York, as measured near Manhattan, could see up to 135 flood days during the same time period, with Norfolk, VA hitting as many as 170.

"This is not a year 2100 issue," Sweet said. "The water will come in where the water wants to come in."

Kmiller@pbpost.com

@KmillerWeather

See Insurance News Net article . . .

See also 2018 brought record breaking high tides. NOAA says 2019 will soak South Florida with more (Miami Hearald)