Miami’s Existence Is Threatened With As Little As 18″ Of Sea Level Rise

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While Hurricane Florence missed Miami, causing only cancelled flights, diverted cruises, and warmer-than-average weather, it’s another near miss for The 305. This is the second unusual hurricane season in a row, with Maria, Irma, and Harvey all causing deaths and destruction on US soil.

Miami is unusually vulnerable to the effects of climate change. It’s already seeing high-tide, clear sky flooding as regularly as clockwork in multiple neighborhoods. It has the United State’s third-tallest skyline, with most of the buildings close to the water. And there are multiple other factors at play. Miami may not be a major US urban center in a handful of decades.

There are several elements in the equation, but Miami’s existence could be untenable with as little as 18 inches or as much as 15 feet of sea-level rise. The operative question is how much of the city will still exist as a working urban area with citizens, but Miami will be at high risk with only 18 inches of sea-level rise.

Let’s list the elements of the problem.

Basic sea level rise. 50% of Miami’s population of 5.5 million lives beneath 6 ft of sea level. With a King tide and a hurricane, most of that real estate is vulnerable today, but with another 18 inches of sea level, that real estate is highly vulnerable. And sea level rise is accelerating.

Uneven sea level rise. Miami is closer to the equator and warmer than the average city. As ice caps melt, they stop sucking water closer to them due to their gravity and it instead does what the rest of the water does and flows toward the equator due to centripetal force. And then it gets warmer and expands. The combination means that sea level rise in Miami will be greater than average.

Subsidence. Miami, along with the rest of the eastern seaboard, is still sinking slowly after being raised a few inches by the weight of the glaciers which melted 20,000 years ago.

The hurricane problem. 2017’s hurricane season is a taste of what is coming. More severe hurricanes and more tropical storms elevated to hurricane status. They’ll be more damaging in multiple ways. They’ll drop more rain, they’ll be wider so do damage over a larger area, they’ll have higher storm surges and they’ll have higher winds. When poor people leave an area due to hurricanes destroying their homes, they don’t move back. New Orleans still has 100,000 fewer residents than before Katrina. Sadly, many of them moved to Houston and were subjected to Harvey. Miami will be hit more often by more damaging hurricanes. More evacuations will occur. Major seasons occur on average every ten years, but minor seasons will start looking like the major seasons of old.

The real estate problem. Miami-Dade County’s low-lying real estate is worth tens of billions of dollars. But it’s already lost hundreds of millions since 2000 due to sea level rise. 10% of Miami’s real estate value could be a write-off by 2045. And there’s a ripple effect, as formerly affordable areas, which tended to be places with people of color working in the service industry, are now prime real estate. Rental properties are being purchased by people who used to purchase properties by the beach. Gentrification is driving out poor people. It’s another force making it difficult for Miami’s economy and service industry to continue to thrive.

Porous rock. Many assume that sea walls will just be built. However, southern Florida is built on limestone. It’s a giant rock sponge that can’t be sealed. Everything underground is going to be soaked in seawater including little things like the sewage lines. Put a seawall up and water will well up inside of it.

The freshwater problem. Miami gets all of its fresh water from the Biscayne Aquifer. It’s a bunch of freshwater from the Everglades and rain water held in the previously mentioned giant limestone sponge. Guess what is already happening? Yup, sea water is seeping into the fresh water. They are already sticking pipes down to suck some of the brackish water out and pump it back out to sea. Reference King Canute to see how that is going to end. Based on conservative estimates of sea level rise, that aquifer could be entirely brackish, requiring expensive desalination, by 2050. That would make water about 2.5 times more expensive than it is now. It’s unlikely the federal government and state are going to be spending billions on Miami when they haven’t been able to agree on funding for the Everglades.

The freshwater problem part 2. The Biscayne Aquifer isn’t only threatened by salt water. It’s surrounded by aging septic tanks in rapidly built sprawling subdivisions, by several Superfund sites, and by limestone mining around it. The timeframe for those plus seawater requiring much more expensive water treatment is a couple of decades. This could make the poorer people in Miami out-of-luck by 2040.

The beaches problem. Florida’s economy is bound to its beaches. The single biggest industry in Florida is tourism. Beaches are the biggest draw. However, beaches are highly susceptible to sea-level rise as is beachfront property. They are already spending tens of millions annually on beach reclamation, split roughly equally between federal, state, and municipal budgets. But beach sand is becoming a rarer and more expensive commodity while sea level rise and storms are scouring more of it from beaches. Florida and the federal government are going to pick and choose which beaches they bother to save. Entire communities will likely lose their primary source of income. This will have a ripple effect on Miami, but Miami’s beaches will undoubtedly be among those preserved with increasingly frantic efforts.

The agriculture problem. Florida’s second-biggest industry after tourism is agriculture. However, with increased heat, increased hurricane severity, less fresh water and fewer workers, it’s going to be put under increasing pressure in the coming decades. Another pillar in Florida’s economy will start to fail.

That’s a lot of problems. It’s unsurprising given that southern Florida was an inhospitable swamp before air-conditioning made it possible to enjoy the beaches and live there. But all of this means that Miami is facing more basic challenges than any other city in the United States.

All of this means that the cost of maintaining Miami as a modern, well-serviced city with great beaches will skyrocket while the economy of the state and the city will be massively challenged and possibly collapsing. More major hurricanes of greater severity will likely hit it, causing damage that owners and insurers decide not to repair. More people, mostly poorer, will leave never to return.

It will look very different by 2050. Many existing low-lying properties will have been abandoned. Some will have been torn down and built again on pedestals of some sort. Others will be rotting. Some areas will have lost basic services such as fresh water and sanitation as triage occurs.

But it’s very likely Miami will continue to exist in some form for a century or more. There will always be rich people who want to be served Cuba Libres on white sandy beaches. It will be more and more expensive to maintain those beaches and there will be fewer and fewer poorer people to do all of the work, so more places, like Mar a Lago, will import foreign workers to keep the beaches swept.

Miami and Key West will become even more artificially maintained rich party places. It’s hard to say when they would become completely non-viable because past 2100 there hasn’t been much research done, but we are on track for much more sea level rise post-2100 than pre-2100. And Miami’s vulnerabilities won’t be disappearing. Hurricanes won’t be getting weaker. There will come a point when it’s just not worth rebuilding.


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Michael Barnard

is a climate futurist, strategist and author. He spends his time projecting scenarios for decarbonization 40-80 years into the future. He assists multi-billion dollar investment funds and firms, executives, Boards and startups to pick wisely today. He is founder and Chief Strategist of TFIE Strategy Inc and a member of the Advisory Board of electric aviation startup FLIMAX. He hosts the Redefining Energy - Tech podcast ( , a part of the award-winning Redefining Energy team.

Michael Barnard has 733 posts and counting. See all posts by Michael Barnard