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 United States – including the largest in Texas – are at risk of collapse due to shifting soil beneath them. Inspections generally do not account for these movements, suggesting that many of the country’s dams are in worse condition than previously thought.
The new findings raise the possibility that thousands of dams that we haven’t monitored closely due to their high costs and lack of personnel 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?
Changing terrain
In a presentation At 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 land subsidence or rise. Depending on the material of the dam, this can lead to cracks forming, particularly if different parts of the structure are moving in opposite directions or at varying speeds.
“This technology helps us detect potential problems and then notify those responsible,” said the lead researcher. Mohammad Khorramipostdoctoral 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-risk hydroelectric dams measuring more than 50 feet (15 meters) and rated as “poor” or “unsatisfactory” according to the Ranking of the National Dam Inventory. 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The results are preliminary and have not been peer-reviewed. Nonetheless, they show previously unknown weaknesses in dams in 13 U.S. states and Puerto Rico, including Roanoke Rapids Dam in North Carolina and Livingston Dam, the largest dam in Texas.
Some of these high-risk dams are moving significantly. For example, the northern portion of Livingston Dam, which supplies two water purification plants providing more than 3 million people in Houston – is flowing at a rate of about 0.3 inches (8 millimeters) per year, while the southern portion is simultaneously rising by the same amount.
“It doesn’t mean that part of the dam is collapsing,” Khorrami said. But such altitude differences merit further investigation, as they could prove problematic, he added. Given that these dams are decades old, potentially defective, and affecting both downstream populations and energy supplies, structural deformations could be disastrous.
A tragic incident in Libya in 2023 suggests that land elevation changes are not something to be overlooked. On September 11, two dams collapsed following extreme rains caused by Storm Daniel. These outages released 1 billion cubic feet (30 million cubic meters) – or 10,000 Olympic-sized swimming pools – of water on the town of Derna, destroying buildings and bridges and killing people. up to 24,000 people.
Deformations of the dams resulting from changes in terrain elevation likely contributed to the collapses, a 2025 study found. “Satellite imagery results showed consistent and persistent deformation on these two dams over the past decade,” Khorrami explained. “So these 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.
“This is not a substitute for inspections,” Khorrami said. “We provide another tool to help detect warning signs if there is a problem, actual or potential, with the dam.”
Aging infrastructure, changing climate
But land displacement is only one of the factors that can compromise dams. The United States has nearly 92,600 dams — of which more than 16,700 present a “high risk potential”, i.e. their collapse could lead to significant loss of life and material destruction, according to ASDSO. Most were designed more than 50 years ago, and about 2,500 of them show signs of damage that would collectively require billions of dollars to repair.
They are not all giants like the Hoover Dam; in fact, thousands are small hydrographic 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 people lived nearby. But several decades later, communities have multiplied around them, meaning failure could be devastating.
Additionally, most of these dams were designed to withstand the environmental conditions that existed at the time of their construction, but global warming and changes in land use have altered the situation.
Some rivers are declining due to drought, while others have higher water levels and flows than 50 to 60 years ago due to increased precipitation and urbanization, which reduces the amount of water stored in the ground. Ebrahim Ahmadisharafassistant professor of civil and environmental engineering at Florida State University, who was not involved in the research, told Live Science.
Weather conditions are also becoming more extreme and unpredictable, increasing the risk of flash flooding, Ahmadisharaf said. In 2025 studyhe and his colleagues found that the likelihood of a dam overflowing — when water is so high that it exceeds the capacity of the spillways and gushes over the dam — has increased by 33 dams over the past 50 years.
The dams with the highest exceedance probabilities in this study were large dams with relatively large populations living in towns and small towns downstream, including Whitney Dam in Texas, Milford Dam in Kansas, and Whiskeytown Dam in California. Population centers that could be affected include Waco, Texas, with a population of 150,000, and Junction City, Kansas, with 22,000.
“Crossing is a possible dam failure mechanism,” Ahmadisharaf explained. “This can lead to catastrophic flooding downstream and then structural failure. The larger the dam and the shorter the distance to downstream infrastructure and people, the more dangerous it is.” [overtopping is]”.
Money problems
One of the biggest obstacles to dam safety in the United States is funding — and the older dams get, the higher the bill gets.
“Operating, maintaining and rehabilitating dams can cost anywhere from a few thousand to several million dollars, and the responsibility for these expenses falls on owners, many of whom cannot afford these costs,” Roche said. “Rehabilitating only the most critical dams was estimated to $37.4 billion, a cost that continues to rise as maintenance, repair and rehabilitation are delayed.
Deploying satellite monitoring of dams would increase the financial burden – but it could be worth the cost if it helps prioritize repairs and avoid breakdowns, Roche said. According to a forensic report Regarding the 2017 Oroville Dam spillway incident, which caused more than 180,000 evacuations but no deaths, traditional dam inspections do not always identify significant structural issues.
With only preliminary results available so far, it’s difficult to say whether using satellite data to prioritize dam repairs is helpful, Roche said. But in theory, “deformation of dam structures can be a sign of a problem or a worsening of their condition,” he said.
David Bowlesan expert on dam safety risks and professor emeritus of civil and environmental engineering at Utah State University, is more skeptical. “A dam can fail in many ways,” Bowles told Live Science in an email. “In my experience, foundation subsidence is not a major cause of dam failure, but it could be a factor, particularly if not monitored and managed.”
Satellites could also play a role in assessing the risks of dams overtopping, Ahmadisharaf said. Satellite radar images could provide better estimates of water levels and flooding, which could help issue warnings earlier.
Overall, satellites could provide a broader picture of dam risks than we currently have, Ahmadisharaf said. “We can’t monitor everywhere,” he said, “but satellites provide that opportunity.”
