Aging Dams in the US: Risks and Vulnerability
- Satellite images have revealed that dozens of dams across the U.S.
- 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...
- Satellites could provide a simple way to monitor dams, potentially revealing places where ground movements are destabilizing their structure, experts told Live Science.
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 then 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?
Shifting ground
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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
“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,
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 important 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 res
Oroville Dam Spillway Failure
The Oroville Dam spillway partially collapsed on February 12, 2017, prompting the evacuation of nearly 188,000 people in Butte County, California, due to fears of uncontrolled water release.
Background and Details
Oroville Dam, located on the Feather River, is the tallest dam in the united States at 770 feet high. It’s a crucial component of the California State Water Project, providing water for agriculture and municipal use in Southern California. The dam features a main spillway and an emergency spillway. Both were designed to handle large volumes of water during peak runoff,particularly during heavy rainfall or snowmelt.
The initial failure occurred in the main spillway, where large sections of concrete eroded. This erosion continued, and engineers feared a complete collapse, which would have necessitated the use of the emergency spillway. However, the emergency spillway, which had not been used sence the dam’s completion in 1967, also began to show signs of distress. The earthen structure of the emergency spillway started to erode, creating a large ravine.
Timeline and Evacuation
- February 9, 2017: Erosion is first noticed in the main spillway.
- February 12, 2017: A large section of the main spillway collapses.
- February 12-13, 2017: The emergency spillway begins to erode, prompting officials to order the evacuation of nearly 188,000 people downstream.
- February 13, 2017: Water releases from the dam are reduced, and the immediate threat subsides, allowing residents to return home.
Investigation and Findings
The California department of Water Resources (DWR) conducted a forensic failure analysis. The investigation determined that the primary cause of the spillway failures was a combination of factors, including design deficiencies, inadequate maintenance, and unusually high water levels due to a historically wet winter. Specifically, the original design of the spillway did not adequately account for the potential for erosion under sustained high flows.
The DWR’s final report, released in January 2018, detailed the findings and outlined a plan for complete spillway reconstruction. The report stated that the lack of regular inspections and timely repairs contributed to the severity of the damage. The total cost of the spillway reconstruction was estimated at $1.1 billion.
reconstruction and Current Status
Reconstruction of the main spillway was completed in November 2018. Work on the emergency spillway, including improvements to it’s stability and capacity, continued through 2020. As of January 30, 2026, both spillways are fully operational, and the oroville dam is operating under enhanced monitoring and maintenance protocols. The DWR has implemented a extensive spillway monitoring and maintenance program to prevent future failures.
Source: California Department of Water Resources – Oroville Dam