On a 95-degree day this summer, New York City’s Third Avenue Bridge, which connects the Bronx and Manhattan, remained open for hours. As heat and flooding scorched and battered the Midwest, a steel railroad bridge connecting Iowa to South Dakota collapsed under rising water. In Lewiston, Maine, a bridge closed after its deck buckled due to fluctuating temperatures.
America’s bridges, a quarter of which were built before 1960, were already in need of repair. But now extreme heat and increased flooding linked to climate change are accelerating the disintegration of the nation’s bridges, engineers say, effectively aging them prematurely.
The result is a quiet but growing threat to the safe movement of people and goods across the country, and an example of how climate change is altering daily life in ways Americans may not realize.
Sign up for the New York Times morning newsletter
“We have a bridge crisis that is specifically tied to extreme weather events,” said Paul Chinowsky, a professor of civil engineering at the University of Colorado Boulder who studies the effects of climate change on infrastructure. “These are things that would not happen under normal climate conditions. These are things that we have never seen at this rate.”
Bridges designed and built decades ago with materials that cannot withstand wide temperature fluctuations now swell and shrink rapidly, making them weaker.
“It gets so hot that the parts that hold the concrete and steel together, those bridges, can literally fall apart like Tinkertoys,” Chinowsky said.
As temperatures this year hit their highest ever, much of the country’s infrastructure, from highways to runways, has suffered. But bridges are particularly at risk.
“With bridges, you’re working with infrastructure that was planned, designed and built decades ago,” Transportation Secretary Pete Buttigieg said in an interview. “It’s one of the longest pieces of infrastructure to update or renew. And yet we see those vulnerabilities all across the country.”
A study in the journal PLOS ONE found that extreme temperatures due to climate change could cause 1 in 4 steel bridges in the United States to collapse by 2050. Collapses caused by extreme heat could require large-scale bridge repairs and closures by 2040, researchers said.
Another study found that exposure to new levels of extreme heat is causing the pavement on U.S. bridges to buckle. Meanwhile, heavy precipitation linked to climate change is increasing the phenomenon of “bridge scour,” the erosion of sediment around bridge foundations that is the leading cause of bridge failures in the United States, research shows.
Bridge problems are beginning to impact supply chains and the cost of goods. In 2022, a 30-foot stretch of bridge on the California-Arizona border of Interstate 10, along a major trucking route from Phoenix to the Port of Los Angeles, was swept away by record rainfall. That washout followed a 2015 collapse of another Interstate 10 span, the Tex Wash Bridge, during what was described at the time as a once-in-a-1,000-year flood. Each closure adds an estimated $2.5 million per day to trucking costs due to delays and extra fuel, according to the American Transportation Research Institute. Engineers predict that such bridge closures will increase significantly nationwide over the next decade.
“With many of these bridges closed, trucks are having to make much more detours than normal. That adds 15 to 100 miles per trip, when a truck trip normally costs about $91 an hour,” said Dan Murray, senior vice president of the American Transportation Research Institute. “And it becomes very inflationary. We’re buying the same goods and the unexpected costs are being passed on to the consumer.”
Bill Minor, 50, a Walmart truck driver who delivers groceries, clothing and electronics from a terminal in Beaver Dam, Wis., to stores in the surrounding area, said he crosses the Lake Butte des Morts Bridge in Oshkosh, Wis., as many as a dozen times a day. When the bridge was closed for a day in June because heat caused a crack in the approach to the bridge, Minor said the extra detour and traffic caused him to make fewer deliveries and use more fuel.
“The bridge is on a highway, but the bypass is on country roads, so you’re driving through small towns and doing 25 miles an hour,” he said.
The Biden administration has tried to address the problem. The bipartisan infrastructure bill of 2021 appropriated $110 billion for repair and construction of roads, bridges and other major transportation projects. The law included a landmark program, PROTECT, which provides $7.3 billion across states to make facilities and highways more resilient to extreme weather. Another $1.4 billion in competitive grants is also available.
In Vermont, where heavy rains and heat have damaged an estimated 100 bridges in the past two years, the state is rebuilding them higher and wider, with deeper foundations and sturdier materials. And waterways under bridges are being made deeper and wider to absorb more water.
But all that costs money and time. It costs Vermont 30% to 40% more to build a bridge that is more flood-resistant, said Jeremy Reed, chief engineer for the state transportation agency.
Scientists, engineers and government agencies are just beginning to develop standards for building climate-resilient bridges, said Jim Tymon, executive director of the American Association of State Highway and Transportation Officials. “We’re learning from the events that are coming our way and trying to adapt and build for whatever else climate change brings, but it’s a moving target,” he said.
In 2018, Colorado became one of the first states to consider the effects of climate change in road and bridge planning. After a 2013 flood damaged about 500 miles of roads and 50 bridges in the state, requiring more than $700 million in emergency repairs, the state’s transportation commission required climate resilience in bridge and road construction.
The state hired Hussam Mahmoud, a civil engineer and professor at Colorado State University, to investigate the increased deterioration and stress in the connections of the state’s steel bridges. “What we saw was dramatic,” Mahmoud said.
For decades, bridge surfaces have been connected using fork-shaped expansion joints. These are incorporated into the steel and the road surface to accommodate normal swelling and shrinkage due to heat and cold.
But extreme heat spikes linked to climate change have caused the joints to swell more frequently, Mahmoud said. The problem has been exacerbated as overheated joints expand tightly around the highway debris that typically collects between them. “When this happens, the bridge can be permanently damaged,” he said. “The steel warps and twists, the deck cracks and moisture gets through, causing corrosion.”
Swollen joints cause other problems. Steel bridges are designed to flex gently to support heavy loads, but clogged joints keep beams stiff, preventing the load of large trucks from spreading.
“This means that the beams in the bridge are carrying much more weight than they were designed for,” Mahmoud said.
Age is usually one of the best predictors of bridge vulnerability. Engineers generally prioritize bridges for repair and replacement if they are over 50 years old.
Mahmoud was therefore surprised to discover that Colorado’s bridges were in the worst condition, including an 18-year-old bridge over the Riverside Canal in Morgan County, a 29-year-old bridge on County Road 501 through Pueblo County and a 10-year-old bridge on County Road 17 over the Otero Canal in Otero County.
All of these bridges were found to be in “good” or “satisfactory” condition by the Federal Highway Administration’s National Bridge Inventory based on inspections conducted between 2020 and 2022.
Colorado transportation officials say they now take such research into account when deciding which bridges to repair, but the state doesn’t have the funding for all those improvements. Under the state’s infrastructure law, the state gets $45 million a year in federal funds for bridge repairs and $98 million a year from the PROTECT program to make all of its infrastructure more climate-resilient, both through 2026.
State officials estimate that Colorado will likely need more than five times that amount per year. “Realistically, we know that’s not going to happen,” said William Johnson, who directs climate resilience programs for the Colorado Department of Transportation. “We can’t replace everything tomorrow to be more resilient, but we are building climate change into the process.”
Mahmoud expanded his research across the country, using data from the National Bridge Inventory to model the impact of climate change on the beams, decks and girders of 80,000 steel bridges. He found that the bridges most at risk were in the Northern Rockies and Plains, the upper Midwest, the Ohio Valley and the South. He also found that smaller bridges, with smaller beams, were more vulnerable to damage because they were built to carry lighter loads.
The bridges in Mahmoud’s database include 1,357 steel bridges in Oklahoma and 575 bridges in North Dakota, including a 25-year-old bridge over the North Branch Goose River in Traill County, North Dakota, a 16-year-old bridge on a state highway through Grand Forks County, North Dakota, and an 11-year-old bridge on Highway E0220 in Grant County, Oklahoma.
“These bridges in these states are designed to code,” Mahmoud said. But because of the unplanned damage caused by climate change, he said, “we’re going to see the beams on these bridges twist, we’re going to see concrete come off, we’re going to see bridges close.”
Jason Thorenson, the North Dakota state bridge engineer, said he disagreed that the North Dakota bridges Mahmoud mentioned are at risk. The state receives about $45 million a year from the PROTECT program, he said, “but I wouldn’t say we’re using that money to address climate change, because I can’t say we’re really seeing that.”
Tim Gatz, deputy director of the Oklahoma Department of Transportation, said both cold and heat can put a strain on roads and bridges. “We’ve always had a very wide range of weather conditions,” he said. “Sometimes extreme cold and sometimes extreme heat.”
Research shows that climate change has caused more rapid shifts between extremes of heat and cold, said Royce Floyd, a professor of engineering at the University of Oklahoma. Those fluctuating temperatures can cause the pavement to press down on a span from both sides, causing the road and steel to buckle or crack, or even push steel beams out of alignment, Floyd found.
That’s what’s happened to at least three major bridges in Oklahoma in recent years, he said. The bridges have since been repaired — without regard to studies showing the current and future impacts of climate change. But if they’re not made stronger, the buckling could return, Floyd said.
“If you don’t take climate change into account, you’ll have the same problems again,” he said.
c. 2024 The New York Times Company