Scientists predict who in America will be hit hardest by floods by 2050

When Hurricane Ida unexpectedly devastated the northeastern U.S. in 2021, most of the cities it hit hardest were unprepared. Infrastructure failed and a significant number of people perished. Damage from floods like those caused by Ida will increase by 26 percent over the next three decades, new research suggests — and the U.S. will have to meet the challenge or be submerged.

What’s new — The study, published Monday in the journal Nature Climate Change, reveals the people and places in the U.S. most likely to be hit with dangerous and damaging floods in the next thirty years. Together, the data shine light on the intersections of race, geography, poverty, and the climate crisis.

“We show, for the first time, what the [flood] risks are now, what the risks might be in the future as a function of climate change and population growth, and the kinds of communities that will be impacted,” Oliver Wing, study co-author and researcher at the University of Bristol’s School of Geographical Sciences, tells Inverse.

Taken together, climate change and population growth will expose 7.16 million people annually to floods — a shocking 97.3 percent increase from the present day.

Specifically, Wing and his team used flood hazard maps to pinpoint the places most at-risk of rising water. Risk is based on how likely it is a flood will occur in that specific area and the odds of it causing damage to infrastructure and property or even humans. To craft these projections, the scientists quantified and mapped the hazard posed by increased flood risk on multiple levels. They then paired these data with census tract data to identify the most-vulnerable communities and populations.

“There’s impact across the country, but we can see hotspots of risks on the coasts and the inland Northeast through Appalachia,” Wing says.

Ning Lin is an associate professor at Princeton University who studies hurricane hazards and risk analysis and was not involved in the new study. Lin describes the findings as “impressive.”

“The study will have large impacts on flood risk modeling and risk management,” Lin tells Inverse.

Why it matters — Before this study, public officials and ordinary citizens would “rarely consider flood risk adequately” according to researchers. Much of what we currently know about flood hazards comes from data collected and analyzed by FEMA, the federal disaster agency, but these are limited and outdated.

Officials simply lack the necessary information to make informed decisions about where to develop new homes, as well as the data needed to identify the populations and communities most at risk of flooding in the future. This is costly: By 2050, the U.S. will lose $40 billion to floods.

“The lack of quality publicly available flood risk information has meant that risky developments have proliferated across the United States,” the researchers write. This should be obvious to anyone who lives in a coastal city, like New York City or Miami — new builds are not slowing down.

Where’s the flood risk?

Heavily populated counties on the coast, as well as in Appalachia and the Northeast, are most likely to see more floods over the next few decades.

“Climatic changes alone cause dramatic increases in risk along the East Coast in counties that are already high-risk,” write the researchers. Global warming exacerbates the intensity of hurricanes, and, in turn, increases flood risk, they point out.

Coastal Louisiana and rural counties of the Pacific Northwest and Northern California are also flood-risk hotspots, the researchers find in the study.

Surges caused by strong hurricanes and rising sea levels also increase flood risk in Virginia, the Carolinas, the west coast of Florida, and significant stretches of the Atlantic and Gulf coasts. Even counties further inland in Florida and the Northeast are at increased risk as a result of rising levels of rainfall due to climate change.

America’s population is also booming in the places most at risk of increased floods — creating a two-fold problem.

Right now, 3.63 million people in the U.S. — a little over one percent of the population — are likely to experience floods each year. Climate change ups that number to 4.31 million people. Population growth ups the number even more — adding 6.27 million Americans in the next three decades. Some Americans will face far more risk than others.

Lin says it’s “alarming” that “projected urban development and population change could cause flood risk increases that outweigh the impact of climate change fourfold.”

Who is most at risk of floods?

Today, the Americans most vulnerable to flood damage are likely to be white and living at or below the poverty line. Flood risk in places where most people fit that demographic is roughly ten times higher than in areas with the fewest impoverished white residents.

As we approach 2050, the researchers reveal a shift: poor Black Americans will have a much higher risk of flood exposure. Flood risk in areas with greater than 20 percent black residents will be double that of flood risk in communities with less than one percent Black residents.

Further, Black residents in the Deep South will see significant climate change-related flood risk. Predominantly Black urban and rural areas from Texas through Florida and up to Virginia will also see a 20 percent increase in flood risk over the next 30 years.

“Equity-centered” reform in U.S. disaster policies and programs could help people adapt to floods or relocate, the researchers write. But these policies tend to privilege richer, white communities over poorer Black residents.

What’s next — The researchers are adamant that officials in the U.S. must recognize and adapt to the increase in climate change-related flood risks — and they’re hoping their data may be a trigger for action.

This new research may not help us prevent imminent floods, but it can help us adapt and potentially reduce rising water’s devastating effects for millions of Americans. Wing suggests the following policy changes to address flood risk and protect Americans going forward:

• Zoning to prevent development in risky areas
• Relocating people from flood-prone areas
• Retrofitting homes to adapt to flood risks
• Expanding the federal flood insurance program

“Information is our antidote to climate change; we now have it,” Wing says.

Abstract: Current flood risk mapping, relying on historical observations, fails to account for increasing threat under climate change. Incorporating recent developments in inundation modelling, here we show a 26.4% (24.1–29.1%) increase in U.S. flood risk by 2050 due to climate change alone under RCP4.5. Our national depiction of comprehensive and high-resolution flood risk estimates in the United States indicates current average annual losses of US$32.1 billion (US$30.5–33.8 billion) in 2020’s climate, which are borne disproportionately by poorer communities with a proportionally larger White population. The future increase in risk will disproportionately impact Black communities, while remaining concentrated on the Atlantic and Gulf coasts. Furthermore, projected population change (SSP2) could cause flood risk increases that outweigh the impact of climate change fourfold. These results make clear the need for adaptation to flood and emergent climate risks in the United States, with mitigation required to prevent the acceleration of these risks.