Infrastructure Shows Effects of Climate Change

Highway One after a portion of the road collapsed into the Pacific Ocean in Monterey County, Cali., in March 2024. (Caltrans/Getty Images/Bloomberg)

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California’s Highway One, stretching more than 650 miles along the Pacific Coast, is one of America’s most popular roadways because of its breathtaking views. Yet, since 2023, large chunks of it have been closed.

That year, a series of atmospheric rivers pummeled the state with rain, triggering landslides and rockslides that the iconic thoroughfare wasn’t built to withstand.

“When they engineered these roads, they made big assumptions that we weren’t going to have big changes in precipitation,” says Paul Chinowsky, professor emeritus of civil engineering at the University of Colorado at Boulder. Planners also didn’t anticipate severe erosion that’s become more common on a warmer planet. “We literally built the roads on the edge of land,” he says.

Global warming is upending those climate assumptions. In California’s climate, research suggests that climate change is increasing the severity of rain brought by atmospheric rivers, making washouts like those that hit Highway One more likely. Increased rainfall also washed away a large chunk of Wyoming Highway 22 last summer, cutting off a vital corridor between Jackson, Wyo., and Victor, Idaho. And road closures remain a persistent problem in Western North Carolina months after Hurricane Helene, which was supercharged by climate change.

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This photo provided by Wyoming Highway Patrol shows a damaged section of Teton Pass near Jackson, Wyo., on June 8, 2024, that officials said had “catastrophically failed.” (Wyoming Highway Patrol via AP)

Worldwide warming temperatures are hammering roads that, like Highway One, were built for a different climate, ballooning repair budgets and sometimes cutting off entire communities from essential goods and services. The 2022 Pakistan floods destroyed 8,000 miles of roads, causing average travel time to market in some places to increase from 2.6 hours during a typical monsoon season to 13 hours.

There are places across the world “where you’ve got one road that services a resort town or a coastal city, and there’s going to be a lot of rethinking because economically the lifeblood of these towns is that one road,” says Chinowsky.

Chinowsky co-authored a study that looked at the impact of climate change on U.S. road budgets if global carbon emissions keep rising until 2040. It found that the cost of maintaining roads in just the U.S. will increase by $100 billion a year by 2050 (in 2018 dollars), or roughly half of what state and local governments spent on roads in 2021.

Most roads are either made of concrete, which is costly and mainly relegated to highways, or asphalt which is lower cost and more common — and most at risk from climate change.

While on the surface all asphalt roads appear similar, their composition can vary significantly depending on the region. This is why asphalt roads in Dubai don’t melt despite desert heat, but Tour de France organizers are finding that they have to water the asphalt roads to stop them from melting during France’s increasingly hot summers.

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An aerial view of flood damage left in the aftermath of Hurricane Helene is seen Erwin, Tenn., on Sept. 28, 2024. (George Walker IV/Associated Press)

Long periods of high heat can cause roads that aren’t built for those temperatures, like those in France, to melt and buckle, causing deep ruts that can be risky for drivers. Similarly, if a road receives more rain than it was designed for then that water can infiltrate below the surface into the base layer, eroding the road. When a car or truck then drives over it, it collapses into potholes. And, since water always moves to the lowest point, it can pool, eroding the road from below causing large segments to collapse in what’s known as a washout, which is what happened to segments of Highway One.

In colder climates there’s another wrinkle: ice. When extreme rainfall is followed by frigid temperatures, the water that has seeped below the asphalt freezes and expands, creating cracks that can speed up road erosion. With climate change, winter temperatures are more variable, leading to more freeze-thaw cycles and bumpier streets in places like the Mid-Atlantic and New England.

In many coastal areas, rising sea levels also cause groundwater to rise, which in turn gets into the natural soils underneath the pavement and base material. That weakens the whole road, causing more rutting, cracking and potholes.

“Road repair and maintenance are required more frequently and it raises the cost for communities because they’re continuingly repairing the same sections of roads,” says Jayne Knott. She is the principal of JFK Environmental Services and she co-authored a study that looked at the impact of groundwater rise on roads in coastal New Hampshire.

She found that not only were all of the roads in her study sample affected, but that the impact could extend further inland than one would expect from sea level rise alone. Roads perpendicular to the coast, like Route 286 in Seabrook, N.H., are especially vulnerable.

These roads, Knott notes, are often evacuation routes and relied on by emergency services to bring aid when disasters strike.

“When they’re flooded from beneath … the roads become weaker and they can’t hold the heavy trucks and the heavy equipment that comes out to actually repair the road,” says Knott.

There are steps that designers can take to make roads more resilient, such as using different additives in the asphalt, building thicker bases, using thicker layers of asphalt and repaving more frequently. But that involves working with engineers to look at how factors like temperature, precipitation and groundwater levels are changing to figure out what materials they should be shifting towards.

Being proactive about climate change cuts costs. Chinowsky’s research found that by 2090, the price increase for annual U.S. road maintenance because of climate change would reach $182 billion. But if the country takes a pre-emptive approach, that would lead to an annual increase of just $4 billion a year. Taking a middle path where municipalities upgraded roads after a climate would lead to an annual increase of $17.8 billion a year.

But roads that were built by the coast, or on cliffs or in canyons like California’s Highway One, would require more extensive rejiggering. “When you start getting heavy erosion events, there’s nowhere else to go,” says Chinowsky. “There’s no way else to save that road unless you move it or, very, very expensively, completely re-engineer what’s been done.”