Flooding Is a $400 Billion Problem That's Getting Worse

Editor's Note: This article appears in Governing's Winter 2025 magazine. You can subscribe here.

Zeb Smathers thought he’d seen it all. Smathers is the mayor of Canton, N.C., which in 2021 suffered devastating floods that caused six deaths and $300 million in damage. Two years later, the town’s paper mill closed after more than a century in operation, removing 1,200 jobs from a community of just 4,400 people.

Canton is still being tested. After the floods, Smathers complained it was “crazy” that the mayor of a town roughly 3,000 feet above sea level had to keep an eye on tropical storm forecasts. Such vigilance, sadly, was not in vain. In September, Canton was slammed by rain from Hurricane Helene, which caused even greater damage than the 2021 storm. “There’s only so much you can do when 28 feet of water comes to your hometown,” Smathers said. “We were told this was a once-in-a-lifetime storm in 2021. Here we are, three years later.”

It’s cold comfort for the people of Canton but their situation, while extreme, is not unique. Everywhere rain can fall, it seems, flooding has gotten worse. Helene was a regionwide disaster across western counties in North Carolina. In June, hundreds of homes were damaged in Hawarden, Iowa, as the Big Sioux River rose to a record-breaking 39 feet. Climates as different as Vermont and New Mexico have seen repeated bouts of flooding this year. In August, intense rain led to hundreds of evacuations and two deaths near New Haven, Conn. “We are talking about rainfall in some areas in the 1,000-year level,” said Brenda Bergeron, Connecticut’s deputy emergency management commissioner.

There are many other examples in every corner of the nation. Flooding is the most dangerous and costly form of natural disaster. Already, estimated costs from flooding across the U.S. range as high as $496 billion annually. If anything, the problem is getting worse. Record temperatures in oceans and surface air mean more moisture in the atmosphere to fuel storms. The federal government’s Fifth National Climate Assessment found that the amount of precipitation in the most severe rain events has increased dramatically in every part of the country over the past 50 years — as much as 60 percent in the Northeast, 45 percent in the Midwest and nearly 40 percent in the South.
The most extreme flood events will continue to grow in number and severity, says Daniel Swain, a UCLA scientist who studies the ways climate change is affecting weather. This will be the case even in places affected by drought. (While New Mexico experienced floods last June, it was simultaneously seeing wildfires.) “In a place like California, we may not ever see an increase in average precipitation, but it’s extremely likely we’ll still see a big increase in flood risk there because of increasingly extreme precipitation,” Swain says. “In the Eastern Seaboard and the Deep South, we see an increase in both average and extreme precipitation.”

Last year, the Environmental Protection Agency (EPA) reported that there’s a nationwide need of $115 billion for stormwater infrastructure investments between now and 2041. That represented a 385 percent increase over its 2012 projection, partly as a result of “an increase in the frequency and intensity of heavy precipitation events due to climate change.” The infrastructure package passed by Congress in 2021 included several grant programs specifically to fund stormwater projects, but those add up to about 1 percent of the need identified by the EPA. Another $1 billion is available through the Building Resilient Infrastructure and Communities program, but that money isn’t earmarked solely for stormwater projects.

After decades of deterioration in many cases, existing gray stormwater infrastructure — gutters, drains, stormwater channels and underground pipes — is inadequate. Almost all of it was built for a climate that no longer exists, Swain says. Engineers designing system upgrades can’t rely on past storm patterns, but what lies ahead isn’t yet in clear focus. The infrastructure law provided funding for the National Oceanic and Atmospheric Administration (NOAA) to update its atlas of community-level precipitation estimates to account for climate change, but this isn’t expected to be complete until 2027.
There’s more at stake than the immediate danger from floodwaters. There are long-term consequences when storm overflow carries pollutants into the water supply. Financing costs and insurance go up in communities where infrastructure can’t meet the test of extreme precipitation. But, while the challenges are enormous, communities across the country are adapting their stormwater systems in ways that not only address flood concerns but create amenities such as parks and preserve more water for productive use.

It remains difficult to hit a moving target. Steve Parrish, chief engineer at the Clark County, Nev., flood control district, hired scientists from the University of Illinois to run multiple rainfall scenarios that incorporated climate change effects. Some indicated less rain, others an increase of as much as 50 percent. “How do you make a decision based on such a wide swath of results?” Parrish wonders.

Lacking a solid projection, the district is linking its infrastructure planning to the demands of a 100-year storm (a storm with a 1 percent chance of happening in any given year). This is common practice, but as NOAA Climate Service Manager Victor Murphy observes, it’s certain that numbers will be higher once the agency’s revised precipitation estimates are finalized. Rain at today’s 100-year levels is likely to occur more often, and subsequent storms will be bigger. Clark County has invested $2.5 billion based on the best data available to it, Parrish says. If climate change rewrites this data, that could mean expensive retrofits or even liability. “It’s a lot of ‘what ifs,’” he says. “It’s really an issue to navigate.”

A basic fact about water is that it has to go somewhere. It might evaporate eventually, but in the meantime any rain that falls needs a place to land. That’s why rain patterns aren’t the only factor in reimagining stormwater management. The share of urban land covered by non-permeable surfaces has increased by as much as a third since 1950, rendering obsolete earlier estimates of how much rainwater land will absorb.

But reduced capacity can be restored through green stormwater infrastructure — systems that mimic the ways nature manages rainfall. This can be accomplished with rain gardens, bioswales (vegetated ditches that collect and direct stormwater), permeable pavement, retention ponds or curbside planter boxes, among other tools. Kate England, Boston’s director of green infrastructure, holds the only such job in the country. She has the authority to work directly with all the leaders of city departments where green infrastructure could be implemented, from schools and roadways to parks. More city departments are incorporating green stormwater infrastructure, or GSI, into their guidelines, requirements and design standards, England says.
The city is also working with local consultants and academics to improve modeling of precipitation and floods. Boston has a grant from the state to collect crowdsourced flood data, asking residents to submit flooding reports during or after rain events. Similar projects have been used in other metropolitan areas in recent years. They have the added benefit of engaging community members in flood control efforts.

Stormwater needs to be considered as part of the larger water picture. Runoff from city streets or farmland can pollute drinking water. Floods can overwhelm wastewater systems. Ideally, these systems can be integrated in ways that create savings rather than damage. Stormwater retention can recharge aquifers and all sorts of recycled water can be used for drinking.

In addition to thinking about water systems holistically, more localities should be thinking about how their systems ultimately are integrated with their neighbors’, suggests Andrew Sauer, an engineer who’s worked on stormwater infrastructure projects in a number of Midwestern communities. Most watersheds — areas of land where all water empties into a common outlet such as a river, lake or the ocean — cross multiple state, county and local borders, but there are few coordinated efforts to map them or understand how conditions such as damage from past floods or forest fires will affect those downstream. Sauer would like to see planning and mapping include watersheds. They are potential sites for green infrastructure projects such as wetland restoration or reforestation, but Sauer says it’s more typical to assume that it’s best to route more water downstream using a larger pipe or widening a channel and that stormwater management will be addressed downstream. “If you want to solve a problem downstream, the only tool I know is to capture control near the source of the rainfall,” says Sauer. “Once it’s in a pipe and flowing downstream, there aren’t a whole lot of solutions.”
Some systems, such as the Metropolitan Water Reclamation District (MWRD) of Greater Chicago, are thinking regionally. The district was created in 1889 as a special purpose agency responsible for both stormwater and wastewater. Twenty years ago, the Illinois General Assembly granted it regional authority over stormwater management in Cook County, a service area that encompasses nearly 900 square miles, 129 municipalities (including Chicago) and 5 million people. This enables Joe Kratzer, managing civil engineer for MWRD stormwater efforts, to look beyond city-by-city solutions. “There are projects that we do where one municipality can’t tackle a problem because it’s really multijurisdictional,” Kratzer says.

Like other big cities, Chicago has 30-foot tunnels buried deep underground as the backbone of its stormwater systems. In a slow, steady rainstorm, water will make its way to these pipes through other gray infrastructure, but during short, intense storms that are becoming more common that approach may not work. “Green infrastructure allows you to capture rain where it’s landing and prevent it from running off,” Kratzer says.

Across the country, at-risk communities face heightened flood challenges due to factors resulting from underinvestment and more properties situated in low-lying areas. In June, the MWRD announced it would devote $20 million from the American Rescue Plan Act for 26 stormwater projects, with an emphasis on projects in underserved communities. One of them is a park in Robbins Village, one of the nation’s oldest historically Black municipalities. What began a decade ago as a project to address flooding from a local creek and shipping channel has turned into a $30 million park centered around an 18-acre lake that can serve as a stormwater retention pond. At this point, plans call for an unused commuter rail stop to be put back into active service, with hopes that it will draw development to the area. Diverting water to the lake will eventually allow the village of Robbins to regain 140 acres of land now in a floodplain.
In North Carolina, another regional agency has also created a new lake. Jordan Lake, south of Durham, was created by a dam as a flood control and drinking water reservoir. The Jordan Lake One Water Coalition is a regional watershed management effort involving 10 counties and 27 municipalities. Coalition members also include water utilities, the state, universities, agriculture and private industry. “You want as much as possible for a disturbed or developed area to act like it’s a natural vegetated area, so it has less runoff, more interception, more infiltration,” says Trevor Clements, a member of the coalition’s board of directors. “But in nature, when there’s a flood, nature can’t handle it either — when the ground becomes saturated, there’s no place for water to go, so it’s going to run off.”

Many of the most “wicked problems,” Clement says, require system and behavioral changes that are not regulated. Building support for such changes involves focusing on social and environmental benefits from infrastructure upgrades, such as new greenspace, safer swimming areas or the higher eventual cost of doing nothing: “Jobs, tax base, things that the public might be more willing to support,” Clement says.

Building public enthusiasm is essential to getting funding for stormwater infrastructure up to levels sufficient to meet the moment. Temperatures will continue to rise. Extreme precipitation events will inevitably become even more frequent. “If you’re talking about building a new bridge or a new dam, those are things where failure could be catastrophic,” says Swain, the UCLA scientist. “You really do need to be thinking about the worst possible thing nature is likely to throw at a system, because it needs to be able to withstand that.”