Thousands of dams in the US are old, damaged and unable to cope with extreme weather. How bad is it?

Satellite images have revealed that dozens of dams across the U.S. — including the biggest one in Texas — may be at risk of collapse due to the ground shifting beneath them. Inspections do not typically account for these movements, suggesting many dams in the country are in worse condition than previously understood.

The new findings raise the prospect that thousands of dams we haven't been monitoring closely due to high costs and staff shortages could be damaged and at risk of failure. But how big is the problem, and is it worth using satellite data to provide early warnings?

Satellites could provide a simple way to monitor dams, potentially revealing places where ground movements are destabilizing their structure, experts told Live Science. However, the new findings also highlight another looming problem: Changing climate conditions could push several of the aging dams in the U.S. to fail, endangering tens of thousands of lives, experts added.

"Identifying issues at dams is critical in preventing failures," John Roche, a dam regulator in Maryland and the president of the Association of State Dam Safety Officials (ASDSO), who did not participate in the new research, told Live Science in an email. "Faced with the threat of increased stress from a changing climate, the lack of timely rehabilitation of dams will lead to increased public safety risks, negative economic impacts, and environmental hazards to citizens of the country."

Shifting ground

In a presentation to the American Geophysical Union in December 2025, scientists used 10 years of radar images from the Sentinel-1 satellite to identify dams that have shifted due to sinking or elevating ground. Depending on the material of the dam, this can lead to cracks forming, especially if different parts of the structure are moving in opposite directions or at varying rates.

"This technology helps us to find potential issues, and then inform the people who are in charge," lead researcher Mohammad Khorrami, a postdoctoral geotechnical engineer at Virginia Tech and The United Nations University Institute for Water, Environment and Health, told Live Science.

The results are based on 41 high-hazard hydroelectric dams that are higher than 50 feet (15 meters), and whose condition is "poor" or "unsatisfactory" under the National Inventory of Dams' classification. These are dams with known defects that compromise the safety of operations and require repairs.

The results are preliminary and have not been peer reviewed. Nevertheless, they show previously unknown weaknesses in dams across 13 U.S. states and Puerto Rico — including Roanoke Rapids Dam in North Carolina and Livingston Dam, the biggest dam in Texas.

Some of these high-risk dams are shifting considerably. For example, the northern portion of Livingston Dam — which feeds two water purification plants supplying more than 3 million people in Houston — is sinking at a rate of about 0.3 inches (8 millimeters) per year, while the southern portion is simultaneously rising by the same amount.

"That doesn't mean that part of the dam is collapsing," Khorrami said. But such elevation differences warrant further investigation, because they might turn out to be a problem, he added. Given that these dams are decades old, potentially faulty and affect both people downstream and energy supplies, deformations in the structure could be disastrous.

A tragic incident in Libya in 2023 suggests land elevation changes are not something to overlook. On Sept. 11, two dams collapsed following extreme rainfall from Storm Daniel. The failures unleashed 1 billion cubic feet (30 million cubic meters) — or 10,000 Olympic swimming pools — of water upon the city of Derna, destroying buildings and bridges, and killing up to 24,000 people.

Deformations in the dams resulting from land elevation changes likely contributed to the collapses, a 2025 study found. "The results of satellite imagery showed a constant and persistent deformation on both these dams during the last decade," Khorrami said. "So those dams were already vulnerable."

Khorrami and his colleagues are finalizing the results of their study. The next step will be to produce an interactive map or database that policymakers can use to assess the safety of U.S. dams.

"It's not a replacement for inspections," Khorrami said. "We're providing another tool to help find early warning signs if there is any issue, or potential issue, with the dam."

Aging infrastructure, changing climate

But ground shifts are just one factor that can compromise dams. The U.S. has almost 92,600 dams — more than 16,700 of which have a "high-hazard potential," meaning that if they collapsed, they could cause loss of human life and significant property destruction, according to ASDSO. Most were designed more than 50 years ago, and around 2,500 show signs of damage that would collectively take billions to fix.

Not all of these are behemoths like the Hoover Dam; in fact, thousands are small watershed dams designed to prevent flooding, provide drinking water and preserve wildlife habitats.

When they were built in the 1960s and 1970s, these dams posed very little risk to people because few lived nearby. But several decades on, communities have mushroomed around them, meaning a failure could be devastating.

What's more, most of these dams were designed to withstand the environmental conditions that existed when they were built, but global warming and land-use changes have altered the picture.

Some rivers are dwindling due to drought, while others have higher water levels and flows than they did 50 to 60 years ago due to increases in rainfall and urbanization, which reduces the amount of water stored in the soil, Ebrahim Ahmadisharaf, an assistant professor of civil and environmental engineering at Florida State University, who was not involved in the research, told Live Science.

Weather is also becoming more extreme and unpredictable, raising the risk of sudden floods, Ahmadisharaf said. In a 2025 study, he and his colleagues found that the likelihood of dam overtopping — when water is so high, it exceeds the capacity of spillways and gushes over the dam — has increased at 33 dams over the past 50 years.

The dams with the highest overtopping probabilities in that study were big dams with relatively large populations living in cities and small towns downstream — including Whitney Dam in Texas, Milford Dam in Kansas and Whiskeytown Dam in California. The population centers that could be impacted include Waco, Texas, with a population of 150,000, and Junction City, Kansas, with 22,000 residents.

"Overtopping is a possible failure mechanism of a dam," Ahmadisharaf explained. "It can lead to catastrophic flooding downstream, and then structural failure. The larger the dam and the shorter the distance to the infrastructure and people downstream, the more dangerous [overtopping is]."

Money problems

One of the biggest hurdles in the way of making dams in the U.S. safer is funding — and the older dams get, the bigger the bill grows.

"Operation, maintenance, and rehabilitation of dams can range in cost from the low thousands to millions of dollars, and responsibility for these expenses lies with owners, many of whom cannot afford these costs," Roche said. "To rehabilitate just the most critical dams was estimated at $37.4 billion, a cost that continues to rise as maintenance, repair, and rehabilitation are delayed."

Rolling out satellite monitoring for dams would increase the financial burden — but it may be worth the cost if it helps prioritize fixes and prevent failures, Roche said. According to a forensic report about the Oroville Dam spillway incident in 2017, which caused more than 180,000 evacuations but no deaths, traditional inspections of dams do not always identify important structural issues.

With only preliminary results available so far, it is hard to tell whether using satellite data to prioritize dam repairs is useful, Roche said. But in theory, "deformation of dam structures may be indicative of a problem or worsening condition," he said.

David Bowles, a dam safety risk expert and professor emeritus of civil and environmental engineering at Utah State University, is more skeptical. "There are many ways a dam can breach," Bowles told Live Science in an email. "Foundation settlement is not a major root cause of dam breach in my experience, but it could be a factor particularly if it is not being monitored and managed."

There might also be a role for satellites in assessing dam overtopping risks, Ahmadisharaf said. Satellite radar images could provide better estimates of water levels and flooding, which in turn could help disseminate warnings earlier.

Overall, satellites could provide a broader overview than what we currently have of risks at dams, Ahmadisharaf said. "We can't monitor everywhere," he said, "but satellites provide this opportunity."