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- Scientists Uncover Massive Freshwater Reservoir Beneath The Atlantic, CNN Reports - September 20, 2025
The Reality Check: America’s Coastal Cities Are Going Underwater
Picture this: you wake up on a perfectly sunny morning, check the weather app showing clear skies, grab your coffee, and step outside to find your street flooded. This isn’t some bizarre nightmare – it’s becoming a regular Tuesday in coastal cities across America. In recent years, however, coastal cities are increasingly flooding on days with less extreme tides or little wind, even on sunny days. People living in coastal cities – like Boston, Massachusetts; Charleston, South Carolina; Miami, Florida; and Galveston, Texas – all experience sunny-day flooding with some regularity. Each coastal city is different: Miami usually experiences three to seven days of sunny-day flooding annually; Boston has been known to have 22 “Waterworld”-like days each year; and Eagle Point, in Galveston Bay, Texas, just set the record for 64 days of sunny-day flooding in one year.
The numbers tell a story that would make any city planner’s head spin. At more than half of the locations shown, floods are now at least five times more common than they were in the 1950s. This isn’t just about hurricanes or major storms anymore – we’re talking about everyday life being disrupted by water showing up where it shouldn’t be.
When High Tide Becomes High Drama
Remember when high tide was just something surfers cared about? Those days are gone. Over the last decade (i.e., since 2014), Hilo, Hawai’i, has exceeded the flood threshold most often – an average of 18 days per year – followed by Galveston, Texas, and Sewells Point, Virginia. Scientists now have a fancy term for what’s happening: “nuisance flooding” or “sunny day flooding.” High tide flooding, sometimes referred to as “nuisance” or “sunny day flooding,” is increasingly common due to long-term sea level rise, driven in part by climate change. It occurs when tides reach 1 to 2 feet above the daily average high tide, depending on location.
The Mid-Atlantic region is getting hit particularly hard. Though the frequency of high tide flooding varies year to year, the Mid-Atlantic experiences an average of 8 more high tide flood days per year compared to the year 2000, an almost 250% increase. Charleston residents now face a grim reality: Charleston – High-tide flood days in 2000, 2; high-tide flood days in 2021, 7; next 12 months, 5 to 9; 2050, 70 to 90 days annually.
Miami’s Soggy Streets Tell A Bigger Story
Parts of low-lying Florida, such as Miami, are already dealing with “sunny day flooding” that happens as a result of high tide. Miami isn’t just facing occasional inconvenience – it’s staring down a future where flooding becomes as predictable as morning traffic. Miami showed the greatest share of exposure to flooding, with up to 122,000 people and up to 81,000 properties that could be at risk of flooding by 2050, according to the paper.
The city has responded with engineering solutions that sound like something from a sci-fi movie. Miami Beach, for its part, even has an official Sea Level Mitigation Plan, which includes raising streets and installing more pipes and pumps to stop – or at least limit – the flooding. But here’s the kicker: even with all these expensive fixes, the water keeps finding new ways to show up uninvited.
The Great Sinking: When Cities Literally Disappear
Here’s where things get really wild: it’s not just that sea levels are rising – the land itself is sinking. Several coastal cities around the United States are “disappearing” into the ground, according to new research, which could further exacerbate complications of sea level rise in the near future. A considerable amount of land in 32 U.S. coastal cities could be at risk of flooding by 2050 due to subsidence, the gradual caving in or sinking of an area of land, according to a paper published Wednesday in Nature.
Thanks to all of this, coastal cities have begun sinking by as much as 0.2 inch (5 mm) a year, tripling the changes to relative sea levels around affected areas. It’s like being caught between a hammer and an anvil – the water’s coming up while the ground is going down. The inundation coastal regions will experience due to rising sea levels may actually be worse than previously thought when factoring in how rapidly the land is sinking, according to the study. However, land subsidence will be the key player in elevating flooding hazards in the next three decades, Shirzaei said.
Boston’s Watery Wake-Up Call
Boston represents the perfect storm of coastal flooding challenges. Boston, MA, is predicted to experience the greatest number of high tide flood days, 12 to 19. The city’s historic charm comes with a hefty price tag when Mother Nature sends the bill. Boston has been known to have 22 “Waterworld”-like days each year, and the projections for the future paint an even soggier picture.
Rising sea levels and sinking land threaten 32 U.S. coastal cities with worsening floods, including New York, Boston, San Francisco, New Orleans and Miami. Boston’s location makes it particularly vulnerable to the compound effects of rising seas and extreme weather events, turning routine high tides into neighborhood-flooding events.
New Orleans: The Fifteen Billion Dollar Gamble
New Orleans is playing the ultimate high-stakes game with water. New Orleans is sinking – and so are its $15 billion flood defenses. In May 2022, nearly 17 years after Katrina, John Bel Edwards, then governor of Louisiana, declared all projects to repair and improve the New Orleans flood prevention system complete, at an estimated final cost of $15.6 billion. But here’s the thing about fighting water: it’s relentless, and it doesn’t care how much money you’ve spent.
The city’s $15.6 billion levee system is only rated to withstand a Category 3. Think about that for a moment – after spending enough money to fund a small country’s economy, the system still has limitations that climate change is actively testing. The city has learned that engineering solutions, while necessary, aren’t magic bullets against increasingly unpredictable weather patterns.
Charleston’s Historic Streets Meet Modern Floods
Charleston’s cobblestone streets have seen a lot of history, but they’re now witnessing something unprecedented. Along the coastal Southeast, Charleston, South Carolina, observed 17 flood days. The city has tried innovative solutions, including Charleston is making a relatively small investment, less than half a million dollars so far, to keep some streets from flooding on sunny days.
But small fixes don’t match the scale of the problem. These proposals for six- to eight-mile floodwalls are being debated in state legislatures across the country, but they have big price tags: $1.1 billion in Charleston; $2.6 billion in Norfolk, Virginia; and a whopping $119 billion in New York City (and an estimated timeframe of 25 years). The question isn’t whether these investments are expensive – it’s whether cities can afford not to make them.
The Ripple Effect: Who Gets Hit Hardest
Coastal flooding doesn’t affect everyone equally, and that’s where social justice meets rising seas. Older adults are disproportionately exposed to coastal flood risk. Nearly 540,000 people aged 65 and older live in at-risk areas. In addition, disadvantaged populations, many of which are already disproportionally struggling with the inequalities of climate change, will especially face challenges due to subsidence and sea level rise, the authors said.
This flooding is increasingly disrupting life in our nation’s coastal communities, which are home to almost 40% of the U.S. population and support 54.6 million jobs. We’re not talking about a few beachfront mansions – this affects millions of Americans who chose to live near the coast for work, family, or simply because they love the ocean breeze.
The Economics of Going Underwater
The numbers behind coastal flooding read like a financial thriller with a very unhappy ending. Losses from the billion-dollar disasters tracked by NCEI have averaged $140 billion per year over the last decade (NCEI, 2025). A Nature Communications study led by researchers from Climate Central showed that human-caused sea level rise accounted for $8.1 billion, or 13% of Hurricane Sandy’s damages in New York, New Jersey, and Connecticut.
Insurance costs are skyrocketing right alongside the water levels. But skyrocketing costs of National Flood Insurance Program (NFIP) coverage are spurring significant departure from the program, with about 70,000 policies dropped in Louisiana from 2022 to 2024. When paired with the ongoing home insurance crisis in Louisiana, this raises premium costs even more. It’s creating a vicious cycle where the people who need flood protection most can least afford it.
Looking Ahead: The Forecast Gets Wetter
The crystal ball for coastal flooding shows more water in our future, not less. As sea levels continue to change, coastal communities will experience more frequent high tide flooding, a national average of 45 to 85 days per year by 2050. By 2050, floods are expected to happen 10 times more often than they do today.
By 2050, La Jolla, California, and Honolulu, Hawaii, will catch up with Boston, scientists predict. All three cities are expected to have about 60 days of sunny-day flooding every year. That’s roughly two months out of every year when routine activities get disrupted by unwelcome water visits.
Engineering Hope: Can We Build Our Way Out?
Cities are getting creative with their defenses, and some solutions are working. Seattle says yes. Its 1.7-mile floodwall, finished in 2018, was built to withstand water of up to 38 feet. It was put to the test when Seattle experienced its second worst flooding in decades. The Skagit River crested at 36.9 feet, but the city remained dry.
Waggonner & Ball estimates that fully implementing the UWP would cost $6.2 billion with long-term projected benefits of $22 billion, whereas maintaining the pre-Katrina infrastructure model would cost New Orleans more than $10 billion over the next few decades. The math suggests that investing in flood protection now could save money in the long run, but that requires political will and public support for big upfront costs.
The Human Side of Rising Seas
With warmer temperatures and human activity causing the oceans to rise and the ground to sink, flooding is now a question of when, not if. But there are still things we can do to prepare for this “floodier future.” The people living in these cities aren’t just statistics – they’re families trying to figure out whether to stay and fight the water or pack up and move inland.
People living in coastal regions are already grasping with significant changes, Ohenhen said. Every flooded basement, every ruined car, every missed day of work because the roads are underwater – these add up to life-changing impacts for real people dealing with an increasingly unreliable relationship with the ocean they once loved living near.
Conclusion: Swimming Against The Tide
Coastal flooding has evolved from an occasional inconvenience to a daily reality reshaping American cities. The challenge ahead isn’t just about building bigger walls or better pumps – it’s about fundamentally rethinking how we live with water in an age of climate change. From Miami’s sunny-day floods to New Orleans’ billion-dollar levees, from Boston’s historic streets to Charleston’s cobblestones, American coastal cities are learning that the ocean doesn’t negotiate.
The question isn’t whether these cities will continue to flood – they will. The question is whether we’ll adapt fast enough to keep them livable. With nearly half the country’s population calling coastal areas home, this isn’t just a local problem – it’s reshaping the American landscape one high tide at a time.
