Exposing the most dangerous dams in the US

AGU press contact:
Liza Lester, [email protected] (UTC-5 hours)

Researchers contact:
Mohammad Khorrami, [email protected] (UTC-5 hours)

NEW ORLEANS - Dams in the United States may be in worse condition than previously understood. More than 16,700 dams across the country are classified as high hazard potential as of 2024, according to the Association of State Dam Safety Officials. Over 2,500 of these dams are in poor condition. But with newly utilized radar technology, scientists at Virginia Tech are revealing dams across the United States that may have crumbling infrastructure hidden from view of safety inspectors.

While research into the use of radar technology to reveal damaged dams is preliminary, geoscientist Mohammad Khorrami at Virginia Tech and his team hope to combine the findings with other publicly available data to build a country-wide database of dams, their flood risks, and the communities who could be impacted by them.

Khorrami will present the findings during an oral session on analytics and data for advancing sustainability at AGU's 2025 Annual Meeting in New Orleans, Louisiana, on Thursday, 18 December. From 15 to 19 December, #AGU25 brings together more than 20,000 scientists to discuss the latest in Earth and space science research.

Most current dams in the United States were built in a boom of construction during the 1950's and 1960's, making the average dam 61 years old, according to the National Inventory of Dams. As dams across the country begin crumbling, Khorrami knew he could help policymakers focus their limited funding. "It's difficult to address all of these dams," Khorrami said. "If you cannot financially take care of all of them at the same time, we can provide the priority dams."

While dams are generally monitored for damages and overall condition, tools to understand the stability of the structure underneath the dam are limited. So, the team at Virginia Tech conceived of a new way to monitor the structural integrity of large dams across the United States without going into the field. Utilizing Interferometric Synthetic Aperture Radar from the Sentinel-1 satellite, Khorrami looked at how sections of high-risk dams slowly sunk into the ground over a 10 year period.

The team focused on hydroelectric dams that are 50 feet or taller, as these dams have the most potential impact if they were to fail - not only to the communities directly downstream but to the vast amounts of infrastructure they can power.

What they found was shocking to them: Many dams that should have been stabilized were still sinking, potentially impacting the dam's structure. "I want to emphasize that this is a preliminary result," said Manoochehr Shirzaei, geoscientist at Virginia Tech and co-author of the research. "We need to do further analysis to have a concrete answer. But some of the observations may suggest that some of these infrastructures are undergoing internal degradation."

At one dam in North Carolina, the team corroborated what other inspections already suggested-the dam was slowly sinking on its northern face, cracking the concrete of the structure and threatening the safety of the town of Roanoke Rapids below it.

With their newfound ability to inspect dams remotely, Khorrami and his team combined the radar scans with structural data of the dams to understand the risk each dam posed. Overlaying these dams with U.S. Census data, FEMA's National Risk Index, and FEMA's flood inundation zones, they further discovered that many of the most damaged dams are poised to destroy many socially vulnerable communities in the country. These communities may have limited emergency preparedness, with a lack of Emergency Action Plans or resources in the event of a flood.

While the United States has yet to see a massive dam breakage in the modern era, Khorrami's team is hoping to prevent such a tragedy. If any one of these large hydropower dams were to fail, "It's a disaster," said Khorrami.

And not just for the communities inundated with flooding, Shirzaei adds, "Some of the dams actually serve as a sub-buffer for water that's used for agriculture and for electricity production. Those dams can create a ripple effect if they fail that can impact the national economy."

The aging infrastructure in the United States is compounding with a threat the engineers of the 1960's could not have anticipated: climate change. Intensive rain events have begun pushing dams to the brink, forcing them to hold more and more water in much shorter periods of time.

But communities still have a lot of power, Khorrami argues. Referencing a 2025 paper by Nasser et al., he noted that a substantial amount of dam failure is due to a lack of maintenance or poor management. Therefore, "almost 40-50% [of dam risk] is something that is in our hands."

"The next step is to create these dynamic risk models that can be updated on a regular basis using the data that we produce," said Shirzaei. The team intends to build an interactive map with current and future data on US dams at risk, available to the public and policymakers alike.

Contributed by Sierra Bouchér

Abstract information:

IN42C-06 - Exposing the Nation's Most Vulnerable Dams: A Remote Sensing and Socio-Spatial Risk Framework

Wednesday, 17 December, 11:35 - 11:45 Central Time

Room 294 (NOLA Convention Center)

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