Tidal floods: Coming soon to an East Coast city near you

MIAMI BEACH — Many major U.S. coastal cities will face a huge surge in the number of tidal floods they experience as sea levels rise due to climate change, a new report has warned.

The study, conducted by the Union of Concerned Scientists (UCS), covered 52 cities on the Atlantic and Gulf coasts, from Portland, Maine, to Freeport, Texas, and predicts a dramatic increase in flooding linked to high tides over the next few decades.

According to the UCS report, over half of the cities surveyed in the study will see three times the number of tidal floods in the next 15 years than they do now. In three decades, when sea levels are expected to have risen by at least one foot, nine of the locations are projected to see a tenfold increase, to about 240 floods yearly.

Once considered a rare problem that was a result only of severe storms and hurricanes, tidal flooding will become commonplace in the near future, the report warns. The analysis paints a grim picture of homeowners’ “dealing with flooded basements, salt-poisoned yards and falling property values, not only because of catastrophic storms but because tides, aided by sea level rise, now cause flooding,” said co-author Melanie Fitzpatrick in a statement released by the UCS.

One vulnerable city is Miami. In 15 years, the report indicates, the South Florida metropolis will have nearly eight times its present tidal flooding: Instead of six floods a year, there will be about 45. By 2045, according to the report, the city can expect more than 40 times as many floods as today. “People find themselves splashing through downtown,” the report says, faced with the Atlantic Ocean’s wrath.

But Miami is far from alone. Other studies have identified the mid-Atlantic coast as vulnerable to problems due to sea-level rise, and the UCS report confirms that. Using a modest scenario for future tides, the report singled out cities where the land is sinking. The analysis projects that in 30 years’ time, Annapolis, Maryland; Lewisetta, Virginia; Washington, D.C.; and Wilmington, North Carolina, would each see well over 300 flooding events per year.

Overall, the report is a compilation of worst-case scenarios if nothing is done to develop comprehensive plans to mitigate outdated flood control systems. The UCS report recommends that cities, with state and federal help, prioritize floodproofing of homes and key infrastructure, halt development in areas subject to tidal flooding and consider measures such as sea walls and enhancing natural buffers.

A glimpse of what the wet future might look like is coming this week, when cyclical extra-high tides known as the king tides peak on Thursday. They occur when the moon is closest in its orbit to Earth and aligns with the sun and Earth, creating a very strong gravitational pull that makes high and low tides more pronounced.

Miami, which the World Bank listed as the second most flood-damage-prone city on the planet (behind Guangzhou, China, but ahead of New York and New Orleans), has been preparing for this event since the beginning of the year. High tides are expected to swell to over a yard above normal on Wednesday and Thursday, according to the National Weather Service.

Since most of the area’s drainage systems were installed over 50 years ago, many of the pipes are decrepit and leaking. Recently, the city has invested $15 million in storm pumps and installed over 80 valves in existing pipes throughout the city to drain excess water that the drainage system can’t hold.

In Miami Beach, on an island separated from Miami by Biscayne Bay, a seawall on the bay is supposed to protect roads and properties from flooding. But during high tides or major rains, water rises above street level, and excess water flows into the streets. So the city is relying on a temporary fix.

“We’re talking to the mayor about these areas which are in high need for repair. Those are areas we did not anticipate the leaking, and so we are putting in these plugs,” said Bruce Mowry, Miami Beach’s chief engineer.

All week, city crews have been sliding temporary rubber plugs in about 20 stormwater drainage pipes and then inflating them. Before the tides roll in, workers will inflate the plugs, sealing the pipes to keep water from flowing back up from the bay and into the streets.

Recently Miami Beach installed two very large pump stations in South Beach, and both have been running at full capacity, pumping water out in preparation for the high tides this week. In the next five years, the city plans to spend the remainder of a half-billion-dollar allotment and add 58 pumps along the beach and main corridors.

The UCS report notes that Miami and Miami Beach serve as a good examples of how cities can improve their flood-control systems, at least until there are comprehensive plans involving local and national solutions. In 2010, adjoining Miami-Dade, Broward, Palm Beach and Monroe counties formed the Southeast Florida Regional Climate Change Compact to collaborate on solutions for the effects of climate change that would extend for the next 50 years.

But the region is just one of many coping with a shift from dealing with a relative nuisance to facing potentially catastrophic floods, says the report, which calls for significantly increased federal funding.

“We just know that climate change is real, and we know that sea level rise is occurring,” said Mowry. “The city of Miami Beach is not talking hypotheticals. We are talking action plans to save our city and maintain our city as a very vibrant and thriving area of our economy for the people of the world to come and visit.”

Another of report’s co-authors, Erika Spanger-Siegfried, a senior analyst at UCS, said that taking no action would be a disaster. “These floods have the potential to be more extensive than today’s tidal floods, affecting much of the Art Deco historic district of South Beach, for example, a centerpiece of local tourism. Without serious intervention, that kind of frequent, extensive flooding would make it impossible for much of the Miami area and the Florida Keys to function the way they do today,” she said.