Earlier this week, homeowners in coastal cities ranging from San Francisco to New Orleans awoke to a troubling assessment splashed across the headlines of local newspapers courtesy the Union of Concerned Scientists (UCS).

According to a new report from the Massachusetts-based nonprofit titled "Underwater: Rising Seas, Chronic Floods, and the Implications for Coastal US Real Estate," as many as 311,000 coastal homes spread across the lower 48 states are vulnerable to "chronic" flooding flooding that occurs as frequently as once every two weeks on average unleashed by climate change-driven sea level rise within the next 30 years. That's the same duration as the lifespan of the typical American mortgage. Collectively, these at-risk residential properties have a market value of $117 billion. Looking further ahead to the end of the century, an estimated 2.4 million homes together valued at a staggering $912 billion, could be partially or fully swallowed by rising rides. And commercial properties don't fare much better.

In its analysis, UCS combined property data pulled from online real estate powerhouse Zillow with a special peer-reviewed methodology developed specifically to identify and assess areas at risk of frequent and disruptive flooding. Three sea level rise scenarios developed by the National Oceanic and Atmospheric Association (NOAA) were used in determining exactly how many homes and businesses are at risk with the most conservative scenario used to shape the core results of the report.

The greatest takeaway from the report? Even some of the most vulnerable costal communities are either oblivious to the risk or woefully unprepared as far as local real estate markets are concerned.

"What's striking as we look along our coasts is that the significant risks of sea level rise to properties identified in our study often aren't reflected in current home values in coastal real estate markets," explains report co-author Rachel Cleetus, who serves as a policy director for the Climate and Energy Program at UCS. "Unfortunately, in the years ahead many coastal communities will face declining property values as risk perceptions catch up with reality. In contrast with previous housing market crashes, values of properties chronically inundated due to sea level rise are unlikely to recover and will only continue to go further underwater, literally and figuratively."

And as the report is quick to point out, chronic flooding can have a significant impact not just on property values but on infrastructure and essential services — schools and roads, for example — offered within these communities. As homes become inundated and, in some cases, uninhabitable, the property taxes normally collected and used to fund these services shrivel up and disappear altogether. From a larger economic standpoint, the result will be nothing short of catastrophic.

Miami skyline Currently over 5,000 homes are at-risk of chronic flooding in Miami, a major port city and economic hub and Florida's second most populous city behind Jacksonville. (Photo: Neil Wlliamson/flickr)

Sobering news for the Sunshine State

When the report was released accompanied by 16 state-specific press releases, the question on most minds obviously revolved around which states and which specific coastal communities are most at risk per USC's analysis. The answer shouldn't come as too big of a surprise.

Using 2100 projections, the USC estimates that Florida leads the pack with more than 1 million homes more than 10 percent of the state's current residential properties that face declining property values and dwindling property tax revenue caused by chronic flooding — that's 40 percent of all-risk homes in the U.S.

Currently led by Philip Levine, a progressive mayor who is keen on protecting his city and combating climate change any which way, Miami Beach leads the most-vulnerable pack with 12,095 homes nearly twice as many as the second most at-risk community representing a combined value well north of $6 billion and a total population of 15,482 people using 2045 projections. But what's perhaps most alarming about Miami Beach is the property taxes that are at risk. If these 12,000-plus homes are lost, so is a staggering $91 million in tax revenues.

Downtown West Palm Beach West Palm Beach ranks among Florida's wealthiest communities ... and also one of the most vulnerable to sea level rise. (Photo: Phillip Pessar/flickr)

Elsewhere in flood-prone Miami-Dade County, another mayor named Philip Philip Stoddard of South Miami laments that the high-cost, high-risk luxury of living on the water will slowly but surely drive residents away. "My flood insurance bill just went up by $100 this year, it went up $100 the year before," Stoddard tells the Guardian. "People on the waterfront won't be able to stay unless they are very wealthy. This isn't a risk, it's inevitable."

"Miami is a beautiful and interesting place to live," the mayor continues, "but people will face a cost to live here that will creep up and up. At some point they will have to make a rational economic decision and they may relocate. Some people will make the trade-off to live here. Some won't."

The Upper and Lower Keys, Key West, West Palm Beach and Bradenton, on the Gulf Coast, are other Floridian communities at particular risk.

Howard Beach, Queens The aftermath of Hurricane Sandy in Howard Beach, Queens. The UCS' new report only factors in flooding caused by sea level rise, not large storms. (Photo: Pamela Andrade/flickr)

Elsewhere on the East Coast ...

New Jersey (250,000 homes at risk) and New York (143,000 homes at risk) also rank highly, and could lose up to $108 billion and $100 billion in residential property values, respectively, while experiencing potentially catalytically eroded property tax revenue bases. In turn, once-thriving coastal communities on Long Island and the Jersey Shore could be transformed into broke and battered ghost towns. In New Jersey, Ocean City, Long Beach, Avalon, Toms River, Sea Isle City and Beach Haven have all been ID'd by USC as being particularly high-risk. In New York, the communities of Hempstead, tony Southampton and the entire New York City borough of Queens are considered to be the most vulnerable to real estate loses brought on by climate change.

Elsewhere in the Mid-Atlantic, communities in Delaware (24,000 at-risk properties, home to 31,000 people, by 2100) and Pennsylvania (4,000 at risk-properties, home to 10,000 people, by 2100) also are of particular concern.

Pennsylvania's inclusion is a curious one considering that it's not technically a coastal state. However, its largest city, Philadelphia, does sit on the Delaware River, a tidal river that's expected to rise alongside the sea. (Nearly 2 feet of sea level rise by 2045 per NOAA projections.) UCS notes that although Philadelphia is far from having the most at-risk properties of the communities analyzed, it does present a particular challenge in that one quarter of the City of Brotherly Love's residents are currently living below the national poverty line.

Toms River, New Jersey The historic township of Toms River in Ocean County, New Jersey, could lose upwards of $30 million in property tax revenue if 2045 sea level rise maps hold true. (Photo: Ian McKellar/flickr)

As UCS writes: "Low-income and marginalized households typically have fewer resources available for coping with challenges like flooding." (Other states where some of the most vulnerable coastal communities are either historically disadvantaged, have large minority communities or struggle with above-average poverty rates include Louisiana, Maryland, North Carolina and Texas.)

The sobering impact that East Coast sea level rise will have on real estate values isn't limited to Florida and the Mid-Atlantic. Charleston, Hilton Head Island and Kiawah Island, all in South Carolina, are among the most at-risk coastal communities in the country while Nantucket ranks as New England's most vulnerable community.

Vintage Rehoboth Beach postcard The economic impact of sea level rise on beloved Mid-Atlantic beach towns like Rehoboth Beach, Delaware, could be potentially devastating. (Photo: Boston Public Library/flickr)

Low-income communities also at high-risk

And then there's California, a state that may not be quite as profoundly impacted by sea level rise compared to Florida, New York and New Jersey but is home to plenty of pricey real estate that could potentially go underwater.

The seemingly natural disaster-prone Central Coast, which includes the city of Santa Barbara, is the most at risk with 2,652 vulnerable homes collectively worth $3.5 billion in real estate value when going by 2045 projections. The affluent Bay Area burgs of San Jose (2,574 at-risk homes) and San Mateo (3,825 at-risk homes) aren't too far behind with $2.6 billion and $2.1 billion, respectively, in potential home value loses.

Looking at these specific Californian communities along with vulnerable East Coast enclaves like Hilton Head and Nantucket, it's easy to conclude America's wealthiest costal communities — communities filled with multimillion dollar vacation homes that directly abut the sea — have the most to lose. And that's largely true.

Santa Barbara Recently ravaged by wildfires, California's scenic Central Coast stands to lose the most of anywhere in the state when it comes to chronic flooding and declining real estate values. (Photo: Damian Gadal/flickr)

But returning to the topic of at-risk communities with sizable low-income populations, the UCS notes that it's these communities that are likely to be hit hardest by the economic impact of sea level rise. Of the 175 communities where chronic flooding has the potential to impact 10 percent or more of homes by 2045, 60 of them currently have poverty levels soaring above the national average. Additionally, in the roughly 75 communities where 30 percent or more of the property tax base is at risk, about a third of them experience higher-than-average poverty rates.

"While wealthier homeowners may risk losing more of their net wealth cumulatively, less-wealthy ones are in jeopardy of losing a greater percentage of what they own," says Cleetus. "Homes often represent a larger share of total assets for elderly or low-income residents. Renters too might find themselves in a tight market or having to put up with decaying buildings and increased nuisance flooding. Hits to the property tax base in low-income communities, which already experience significant underinvestment in critical services and infrastructure, could prove especially challenging."

Flooded home in Houston Lax zoning regulations, among other things, is a reason why Houston was hit so badly by Hurricane Harvey in 2017. By 2045, $2.2 billion worth of residential property across Texas is at risk of chronic flooding. (Photo: Revolution Messaging/flickr)

A massive reason to meet and exceed climate goals

Despite painting a relatively grim picture of homes being swallowed by rising seas and communities being decimated by lost property tax revenues, UCS does offer a glimmer of hope and encouragement. The risk can be negated. But in Trump-era America where half-baked conspiracy theories are now influencing law, and climate-related initiatives have fallen to the bottom of the federal priority list, that issue is, well, complicated.

The most obvious way to alleviate the risk is to enforce existing laws and generate new, aggressive methods of limiting greenhouse gas emissions that contribute to climate change. While the U.S. continues its extended time-out from the Paris climate accord for the foreseeable future, individual cities and states need to remain committed to the agreement and, ideally, go above and beyond it. All of the above scenarios can be largely avoided if action is taken, the more immediate the better.

Elaborates Astrid Caldas, a senior climate scientist with UCS and co-author of the report:

If we manage to meet the goals of the Paris Agreement by keeping warming to between 1.5 and 2 degrees Celsius and if ice loss is limited, 85 percent of all affected residential properties — valued at $782 billion today and currently accounting for more than $10.4 billion in annual property tax revenue to municipal governments — could avoid chronic flooding this century. The longer we wait to drastically reduce emissions, the less likely it is that we will achieve this outcome.

Further risk can be mitigated by simply revisiting and altering existing zoning laws, building requirements, federal flood maps and policies that promote — and even provide incentives for — potentially precarious property decisions. As the UCS explains, these policies "reinforce the status quo or even expose more people and property to risk. The market's bias toward short-term decision-making and profits can also perpetuate risky investment choices." In other words, we need to start building stronger and smarter — and certainly don't build a 20-room mansion on a parcel of land that's forecasted to sink into the ocean within a matter of decades and pretend it will never, ever happen. Because it will.

"The risks of rising seas are profound," writes UCS. "Many of the challenges they bring are inevitable. And our time to act is running out. There is no simple solution — but we do still have opportunities to limit the harms. Whether we react to this threat by implementing science-based, coordinated, and equitable solu­tions — or walk, eyes open, toward a crisis — is up to us right now."

This all being said, if you're curious about the threat of sea level rise-associated chronic flooding and its resulting economic impact in your ZIP code as well as all of the communities mentioned in this article and others, the UCS has created an interactive mapping tool worth spending some time with. Depending on how that goes, you can start looking into property in the foothills of Boise.

Matt Hickman ( @mattyhick ) writes about design, architecture and the intersection between the natural world and the built environment.

These U.S. communities are most vulnerable to sea level rise
A report from the Union of Concerned Scientists shows how many coastal cities are vulnerable to chronic flooding — and how many will be underwater.