Americans abandoning neighborhoods due to rising flood risk, study finds

Rising risk of floods is hollowing out counties across the United States — creating abandoned pockets in the hearts of cities, a new report has found. 

These abandoned areas tend to map onto regions of historic disinvestment — and flight out of them is accelerating, according to findings published in Nature Climate Change. 

In cities across the country, but particularly concentrated in the Midwestern states such as Indiana, Ohio, Michigan and Minnesota, increasing flood risk has driven this “climate abandonment” of individual census tracts, sometimes quite rapidly.

That’s the kind of dynamic demographers fear could lead to a “doom loop” of accelerating outmigration, until only those who can’t afford to leave are left behind in areas most threatened by the changing climate. 

And it could lead to a mass migration of historic proportions, the study found. If investments aren’t made to adapt these areas to better withstand environmental dangers, “there are likely to be large migrations on a similar scale to the Great Migration in the twentieth century, during which 4 million people may have moved,” the authors wrote. 

Among the areas people are abandoning in the face of rising flood risks are particular neighborhoods in many cities — such as Houston, Miami and Washington, D.C. — that are rapidly growing overall.

But while those cities are still pulling people in faster than flood risk pushes them out, the study indicates many are heading toward a tipping point after which a process of decline will begin. 

The research into the impacts of flood risk on migration comes courtesy of First Street Foundation, a nonprofit research group that makes long-term predictions of climate risk for individual properties across the U.S. 

By focusing on the impact of risk of flood, heat, wind and fire on housing — what is “for the vast majority of Americans their most valuable asset” — First Street brings the impacts of a warming world home, founder Matthew Eby told The Hill earlier this year. 

The data shows that climate change is no longer “a thing that might impact my kids,” Eby said. “It’s changing the valuation on my property right now.” 

The success of the tools First Street created to track those risks, however, left its team with a paradox, said Jeremy Porter, First Street’s head of climate implications and a professor of at the City University of New York. 

One pervasive narrative of American response to climate change is that people “are moving toward risk,” Porter said, as they leave the Midwest and Northeast for the heat- and flood-prone Sunbelt and the fire-prone West. 

In terms of flood, Porter said First Street’s research has borne that narrative out — at least when it comes to interstate moves.

But as First Street tools were integrated into real estate sites Redfin and Zillow, it became clear that people were in fact taking climate into account in deciding where to buy, Porter said.

And those long-distance moves are only a small part of the story, because most moves are local. About four times as many Americans move within their county as move across state lines, Porter told The Hill. 

By looking at the impacts of rising flood risk on the population of about 8 million individual census blocks — slices of neighborhoods which often hold just a few dozen people — Porter’s team found that when it comes to the more prevalent short-term moves, people generally move away from flood risk, not toward it. 

These findings make up just a small part of the broader picture of climate risk. (First Street is releasing a more expansive model to track the impact of all climate risks on migration — including heat, fire, smoke and wind — early next year.)

But they show that flood risk alone is already driving outmigration from about 3 million census blocks across the country, which are home to about a third of the nation’s population. 

Over the past 20 years, those blocks have lost about 9 million people, according to the study — about 3 million of them as a result of rising risk from floods. 

This kind of declining neighborhood is what the First Street team call “climate abandonment areas” — parts of neighborhoods where more people left between 2000 and 2020 than moved in. 

In most cases, this decline is on the order of 10 percent. 

But in the most extreme cases — such as Staten Island’s Midland Beach neighborhood — the drop in population was more like a collapse.  

In that census block, First Street found that a 2000-era population of 93 people had fallen by two-thirds, to 31 people by 2020. 

This sort of dramatic collapse risks triggering a death spiral, Anne Perrault of Public Citizen told The Hill.

In many regions, the outmigration is leaving behind hollowed-out neighborhoods, which in the most extreme cases causes abandonment to cascade into more and more abandonment, she explained.

As the spiral accelerates, Perrault said, “migrations will continue to occur from climate vulnerable areas, all while these areas expand because of increased global warming.” 

That decline in population and property values in turn makes municipal lending increasingly harder for cities to acquire to fix things up — creating a self-reinforcing pattern of outmigration. 

The Financial Stability Oversight Council reiterated concerns about such patterns developing in a Thursday report, which found that planetary heating was “imposing significant costs on the public and the economy, with economic costs from climate change expected to grow.” 

That report emphasized the spreading danger of doom loops across the country, in particular as insurance companies withdraw from areas facing climate risks, leading to a cycle of declining home values, leading to fewer new loans being made to buy, build or fix up local houses.

The neighborhoods currently losing people are just one part of a developing story of loss and growth. The Nature study identified 513 counties — or nearly 20 percent of the continental U.S. — that were growing faster than the national average but contained these blocks being abandoned. 

While the population is rising in many of these flood-prone counties, people are moving in more slowly than they are to comparable areas without flood risk: Such neighborhoods are attracting about 4 million fewer people than equivalent ones that aren’t facing that risk, the study found.

These areas are scattered across the U.S., but they’re particularly concentrated in the Gulf Coast (particularly Houston and virtually all of Florida) and the mid-Atlantic between New Jersey and Washington, D.C. 

For example, metro areas including Houston, Fort Worth, El Paso and Phoenix, and the Jersey Shore, all saw growth of 20 to 40 percent between 2000 and 2040 — while 10 to 20 percent of the census tracts in those counties lost people, according to the Nature study.

The First Street model predicts that as a group, these areas of heightened growth and rising risk will hit a tipping point beginning in 2025 — after which point they will begin to decline, ultimately losing an estimated 5 million people from flood risk alone. 

Over the next 30 years, the model predicts that these new “climate abandonment areas” will continue to spread — and be joined by nearly half a million more such declining neighborhoods. 

By 2053, many of the most-populated counties in the country will see between 20 percent and more than 50 percent of their territory in decline, according to the model.

It projects that about 55 percent of the counties that make up Minneapolis, for example, will be losing people by midcentury, followed by about 45 percent of Milwaukee County, 30 percent of Providence County, R.I., and a quarter of the D.C. suburb of Alexandria, Va. 

By contrast, the model predicts that some urban counties will see increased migration due to falling risk, such as counties in the metro regions that hold Newark, N.J.; Detroit; Boulder, Colo.; San Francisco; and Chicago. 

The First Street data also revealed a troubling trend for cities as a whole. While migration to newer, less flood-prone developments lowered flood risk for individuals, the data shows it likely raises that risk for cites overall. 

Take San Antonio, Texas — a fast growing metropolis where First Street data shows 18 percent of the census blocks have been losing people to flood risk even as the county as a whole has gained 44 percent more people.

In that city, people have been trickling out of the increasingly flood-prone urban core — neighborhoods like Tobin Hill/Pearl, where 40 percent of tracts are losing population — to newer, expanding suburban developments in the hills outside town, according to the data.

In Alamo Ranch, for example — which developers bought from an order of nuns in the early 2000s — rapid development has filled in what used to be green space. 

While that may lower risk for those people in particular, every new development rising in former scrubland and cattle pasture brings higher flood risk for everyone downstream.

That’s because new developments mean vast new swaths of rain-repelling asphalt and concrete on lands that once soaked up rain, Porter told The Hill. 

The rise in new “roads, homes, and shopping centers would all significantly impact the natural environment and the natural management of precipitation and riverine flooding,” he said.

And the new land cover concentrates and funnels floodwater downhill, toward those who have remained in the central core, he explained.

Porter said the spread of counties declining under flood risk present policymakers with a paradox — but also with some of the information needed to solve it. 

On the one hand, he noted these emerging abandonment areas are good candidates for what’s often called “managed retreat” — the planned buyout of people in areas no longer defensible under climate change.

On the other, Porter said, as soon as such buyout programs begin, the death spiral in those neighborhoods will accelerate, and “home values decrease as demand decreases.” 

But the data his team found, he argues, gives policymakers the tools to make actual choices: to identify which regions can’t be saved because of overwhelming climate factors — and which are vulnerable because of the long history of often-racist decisions by banks not to invest or loan money for public infrastructure. 

Areas in the second category, Porter argued, can be saved by timely investment in public infrastructure. 

Without such intervention — and in some areas, even with it — the exodus may become unstoppable, he said. 

The end state of this process is a situation where “the people that can afford to leave, leave, and people [who] can’t afford to leave end up staying in the community,” Porter said. 

“You end up with a lot of vulnerable populations at risk.”