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.

‘… 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.’ Melanie Fitzpatrick co-author, tidal flooding report

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the report is a compilation of worst-case scenarios if nothing is done to develop comprehensive plans to mitigate outdated flood control systems.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.