US finally puts brakes on development in flood zones

Over the past century, the United States has built millions of homes along coasts and rivers, on land that is destined to flood. As global warming has raised sea levels and increased rainfall, damage from annual flooding has increased in recent decades, largely because more homes than ever before are located in flood zones. In coastal cities like Carolina Beach, North Carolina, most homes are in a federally designated flood zone, putting them at risk from massive floods like the one that dumped more than a foot of rain on the city this week.

Experts have portrayed this widespread risky construction as an intractable problem, claiming that “home sales in flood zones are booming,” that “more Americans are moving into flood-prone areas,” or pointing to “rapid urban growth in flood zones.” Media coverage, including this publication’s, has largely followed this trend.

But new research from some of the country’s leading experts on climate change adaptation, published last week in the academic journal Earth’s Future, suggests that academics and journalists may have learned the wrong lessons from the past few decades of coastal development. A national survey of floodplain development between 2001 and 2019 found that the United States actually built fewer structures in floodplains than would be expected if cities were building haphazardly. That means that, if you will, the average city is now active. avoid Floodplains, contrary to popular belief. Indeed, in the 21st century, most cities and towns in the United States have built little or no buildings in floodplains. The vast majority of floodplain construction—the kind that makes headlines and fuels doom and gloom—has occurred in just two states: Louisiana and Florida.

A separate study, recently published by the same researchers in the Oxford journal Open Climate Change, found that it doesn’t take a radical change in behavior for a city or municipality to effectively limit floodplain development. According to the study, which focuses on New Jersey, more than three-quarters of cities in the Garden State reduced floodplain development after the turn of the last century, and about a quarter eliminated it altogether. They did this not through major legislative reforms or climate policies, but rather through what the study calls “routine municipal practices” — things like zoning changes and permit denials.

The researchers say the findings should rethink the debate over floodplain management. While unsafe buildings remain a major cause of flood damage and disaster recovery costs, they are not the intractable problem that experts and journalists often portray them to be.

“We build a lot in floodplains, but it’s not as bad as people think,” said Miyuki Hino, a professor of urban planning at the University of North Carolina, Chapel Hill, and an author of both papers. “Avoiding development in floodplains is doable, and we can do even more.”

There are many reasons why a real estate developer might want to build near water. For one, many people enjoy living near oceans and lakes, so homes and apartments built near these bodies of water can fetch higher sales prices and rents. Coastal states like Florida also rely on beach tourism to support their economies, so it makes sense to cluster housing and businesses near the ocean. Additionally, many cities in the United States were built along rivers for navigation purposes, so a disproportionate share of urban land is likely to be in or near the floodplain.

All of these factors might suggest that a significant share of recent housing construction in the United States is in floodplains. But since the turn of the century, the opposite has been true, according to the new study: Developers have built 844,000 homes on 850,000 acres of floodplains, but if they had chosen available plots randomly, they would have built even more. This finding holds true for more than 75 percent of the jurisdictions studied, indicating that most governments are making at least some substantial effort to avoid coastlines and riverbanks.

The study also says the overall increase in flood risk is driven by a few isolated cases, many of them concentrated in Florida and Louisiana. Much of the available land in those states is in coastal or river floodplains, and the economies of both states depend heavily on proximity to water. Another report released this week by the Natural Resources Defense Council confirms the study’s claim: Of the more than 250,000 properties in the United States that have had multiple flood claims filed against them, about half are in states bordering the Gulf of Mexico.

“When we talk about how the United States builds a lot in floodplains, we forget that that’s not the case everywhere,” said AR Siders, a professor of public policy at the University of Delaware and an author of both papers. “There are places that don’t build in floodplains. And then there are places that do so poorly that they reflect poorly on the entire country.”

There are two ways to look at the problem: A county on the Florida coast could build many more homes in the floodplain than a county in the Nevada desert, but the Nevada county could build a larger share There are more new homes being built in the flood plain than in Florida County. The storm damage, insurance claims and rebuilding costs in Florida County will be much higher, but Nevada County also has a lot of work to do, putting new homeowners at risk when there is plenty of other land available.

Policymakers, academics, and environmental activists have proposed a wide variety of sweeping policy changes that could help reduce floodplain development. Some have suggested that federal housing finance agencies should stop securitizing mortgages in floodplains, or that the federally run National Flood Insurance Program should stop insuring them, or that states should ban such development altogether. Given that efforts to simply raise flood insurance rates to market levels have met with enormous backlash, these strategies are likely to create massive political controversy.

But when the researchers looked at New Jersey, which developed most of its shoreline in the 20th century, they found the solution may be simpler than that. In a survey of 500 cities, they found that more than 120 had eliminated floodplain development without any major policy changes. The zoning commission simply denied developers permits, or the mayor required them to build on higher ground, and that was that.

“There are many new and innovative ideas to address this problem, but they may not be necessary for the majority (of at-risk development cases),” Siders said.

“This shows that when you regulate what happens in high-risk areas, you see a discernible impact on exposure and risk,” added Oliver Wing, chief scientific officer at Fathom Global, a flood insurance mapping company owned by reinsurer Swiss Re. “There are very simple solutions that can be implemented locally.”

What about the small share of jurisdictions that account for the majority of floodplain development? The authors argue that these places need targeted intervention. The state or federal government could provide subsidies to encourage less risky construction, helping to offset the economic appeal of building along the water, or a state could simply impose penalties on cities that allow new construction near the water. The precise solution in each situation, Siders and Hino argue, must be tailored to the reasons why a given locality is developing in the floodplain in the first place. Some cities may develop in the floodplain because they lack the capacity to plan for a shift to higher ground, as is the case in many rural areas, and others may do so to capture tax revenues from wealthy vacation homeowners. While designing such policy solutions can be tricky, the authors argue that the local nature of the solutions should be a reason for optimism.

But Wing, who led previous research that predicted a national increase in floodplain development, cautioned that there are limits to the progress documented by the new papers. The researchers show that many governments regulate floodplain development, but most of those regulations apply only to flood zones delineated by the Federal Emergency Management Agency, which produces flood insurance maps for much of the country. However, those flood maps are old and often inaccurate, and much of the flood damage occurs outside floodplain boundaries. That was the case during Hurricane Harvey in 2017, when three-quarters of the homes damaged in the Houston area were outside the lands that FEMA considers flood-prone.

In other words, even if cities take steps to reduce their exposure to flooding, they will likely have to go even further to eliminate flood risk altogether. This would involve even more costly trade-offs between the economic benefits of development and the economic risks of building in areas vulnerable to climate change.

“We have excellent evidence here that flood mapping is effective in limiting development,” Wing said. “The regulations have worked. But what about all the places that aren’t subject to those regulations?”

Editor’s Note: The Natural Resources Defense Council is a Grist advertiser. Advertisers have no role in Grist’s editorial decisions..

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