Green infrastructure helps cities with climate change. So why isn't there more of it?
Federal agencies are beginning to hand out billions of dollars in infrastructure spending, the largest investment ever made in the country's water system. Much of it will go to improving pipes, drains and stormwater systems. But some scientists and urban planners are pushing to fund projects that are better adapted to the changing climate.
Instead of just gray infrastructure, supporters say the answer is green.
Green infrastructure, whether it's large rain gardens or plants along a street median, has the same purpose as big storm sewers: to manage large amounts of water that can build up during heavy rains. Plants and soil absorb and slow runoff from rainstorms, while a stormwater drain captures water that runs down a street gutter and diverts it underground into pipes.
On a hotter planet, storms are getting more intense, and rainfall is often heavier. Flooding is on the rise in many cities. Stormwater systems are being increasingly overwhelmed by extreme rainfall. In the Northeast, the heaviest storms produce 55% more rain today compared to 1958. Last year, dozens of people drowned there when the remnants of Hurricane Ida flooded basements, streets and cars.
Still, most cities face major backlogs in maintaining the aging gray infrastructure they already have, amounting to billions of dollars nationwide. In the rush to secure federal funding to fill that void, some worry that green infrastructure will be left by the wayside.
"What good is a pristine road that's flooded?" says Marccus Hendricks, assistant professor of urban studies and planning at the University of Maryland. "Elevating the priority of green infrastructure and stormwater systems is critical."
How rain gardens help stormwater systems in storms
Downtown Oakland, like a lot of major cities, is mostly a hardscape of concrete. Still, on one block, the sidewalk is lined with a long strip of native California plants.
"I feel so great looking at this," says Joshua Bradt, a project manager for the San Francisco Estuary Partnership. "I love that the plants are alive. They seem to be thriving."
Bradt helped bring this rain garden to life, part of a $4 million dollar project to add green infrastructure to a major thoroughfare in the east San Francisco Bay Area.
When rain storms hit, the water is funneled into the rain garden from the street and sidewalk. As it soaks into the soil, it prevents that water from rushing to the stormwater drain on the corner.
In big storms, that alleviates the pressure on the stormwater system, since those drains and pipes can only handle so much water at once based on their size. When storm drains are overwhelmed, water pools in the street and can inundate buildings.
Bradt says even small rain gardens can make a difference in slowing the runoff that causes flooding. They also have the added benefit of filtering runoff to improve water quality.
Cities struggle to get green infrastructure built
Green infrastructure can also help when it's not raining. Summer heat waves are often more dangerous in cities, because concrete absorbs and radiates heat in what's known as the "urban heat island" effect. Plants and parks can provide much needed cooling.
"If they were on every corner, it would make a tremendous difference," Bradt says. "The reality is that a lot of city departments are already overwhelmed, and this is a hard ask."
While both gray and green infrastructure require upfront funding for construction, green infrastructure also requires ongoing maintenance to keep the plants healthy and clean up litter. Even if cities can secure funds to build the projects, maintenance generally isn't included. They face adding that to their annual budget, which can turn out to be a hurdle for doing green infrastructure.
In addition, the most cost-effective time to build green infrastructure projects is when cities are already doing road or construction work. But because the projects are often managed by different departments, coordination doesn't happen.
"It's becoming more standardized and definitely more accepted," Bradt says. "However, I will say there just is not yet a mass movement towards this, because of how institutionalized and siloed infrastructure management and investment is."
Bigger storms are already overwhelming cities
Whether cities spend on gray or green infrastructure, a hotter climate is adding huge costs to their budgets.
"Our challenge with climate change is that we're seeing these big events," says Lauren McPhillips, a water engineering professor at Penn State University. "We're seeing massive amounts of water that we need to be able to control."
Across the U.S., millions of miles of pipes and stormwater infrastructure stretch below city streets. Most are decades-old, designed for the storms of last century.
Even today, cities lack updated rainfall data that reflects how storms are getting more intense. That means they're still building new projects without climate change in mind.
Federal officials with the National Atmospheric and Oceanic Administration say the agency hopes to begin the process of creating new rainfall forecasts next year. Still, that information isn't likely to be ready in time for cities to use it for the new wave of federally funded infrastructure projects.
Planning for heavier downpours means building larger stormwater systems, but replacing miles of pipes and upsizing existing infrastructure is far more expensive than cities can afford. Experts say green infrastructure can reduce the need to replace as much gray infrastructure. If rain gardens absorb some of the runoff, stormwater pipes don't need to be as large.
That makes green infrastructure potentially more cost-effective. A New York City study looked at using a combination of gray and green infrastructure in one neighborhood in Queens and found that using gray infrastructure alone would be twice as expensive.
Still, a handful of rain gardens won't be enough to prevent flooding, experts warn.
"The challenge is that we need this at scale," McPhillips says. "And especially in these older cities that have built out a lot of hard surface and have gotten rid of the ability for soils to naturally soak in rain, we have a lot to get back to correct for those issues."
Flooding is especially problematic in low-income neighborhoods and communities of color, which generally have fewer parks and where the infrastructure is often more neglected
"The fact that the majority of communities of color lack sufficient green space compared to their white majority counterparts – that is still a problem," says Fushcia-Ann Hoover, who works on green infrastructure at the University of North Carolina at Charlotte. "And so I think that green infrastructure does provide a possible solution."
As infrastructure spending begins, green projects could be just a "stepchild"
Over the next five years, the Environmental Protection Agency will give states more than $11 billion for water infrastructure projects through the Clean Water State Revolving Fund. In March, the EPA released guidance encouraging those funds be used in disadvantaged communities and that states take climate change into account.
"Most cities think about the green and the gray separately, but really the power is integrating these two things," says Radhika Fox, assistant administrator for the EPA's Office of Water.
Still, under guidance from Congress, only 10 percent of the funding must be spent on green infrastructure or water efficiency projects. The last time the government provided a big infusion of infrastructure funds in 2009 the requirement was for 20 percent of projects to be green.
The EPA also emphasized that states have discretion and flexibility to spend the funds as they see fit. The Biden Administration has already gotten pushback from Republicans about encouraging states to consider climate change in spending infrastructure dollars. In February, top Republicans sent a letter encouraging states to ignore similar guidance from the Department of Transportation.
"It does put states in the driver's seat in terms of identifying and working with communities within their borders to find infrastructure projects," Fox says.
The need to repair and upgrade gray infrastructure may take priority over green projects in many communities. In 2020, municipal utilities faced a funding shortfall of $8.5 billion, according to a study from the Water Environment Federation.
"Stormwater systems, green infrastructure and other systems that are tied to the climate crisis have been a stepchild to the types of systems we pay attention to," Hendricks says.