PTAP Aerial As the Hoover Dam turns 90, this is the third in a multipart series looking at the status of dams in the U.S. Read the first installment here and the second here.
Like the Hoover Dam, which recently turned 90, thousands of dams across the United States are now aging infrastructure.
Further reading:
- Hoover Dam is iconic at 90, but rise in US dam removals signals changing mindset
- What can engineers learn from Klamath River dam removals as trend ramps up?
- Benefits flow quickly as historic dam removal restores Klamath River
The average age of the more than 92,000 dams listed in the National Inventory of Dams, maintained by the U.S. Army Corps of Engineers, is 65 years. Many are deteriorating and in need of repair, raising safety and risk concerns for dam owners and, more importantly, downstream communities.
In ASCE’s 2025 Report Card for America’s Infrastructure, the nation’s dams received a D+. The assessment reported that nearly 17,000 dams in the NID are classified as high-hazard potential, meaning their failure could result in loss of life.
Historically, dam failures have been linked to an underlying deficiency, according to the Association of State Dam Safety Officials. As of last year, 2,522 – about 15% – of the nation’s high-hazard potential dams were considered to be in poor or unsatisfactory condition.
PTAP AerialData from ASDSO indicates a concerning trend. Brian Graber, senior director of dam removal strategy at American Rivers, said dam failures and emergency interventions to prevent imminent failures have risen sharply over the past three decades. He highlighted the contrast between the 1994-2003 and 2014-2023 periods, during which such incidents climbed from an average of three per year to 76 per year.
Funding limitations
In March 2025, ASDSO released a report that estimated the cost to rehabilitate the nation’s nonfederal dams at $165.2 billion. Rehabilitating just the most critical dams was estimated at $37.4 billion. Although the 2021 Infrastructure Investment and Jobs Act allocated roughly $3 billion for dam safety, the infrastructure report card’s dams chapter noted that much of that has since been redirected.
Additionally, federal programs remain underfunded, and on average, a single state dam safety official can be responsible for overseeing 190 existing dams.
“Early intervention with dams depends on inspections, but most states cannot keep up with the inspection schedules required by dam safety laws,” Graber said. “Staffing and funding for state dam safety offices have not kept pace with demand. As a result, many offices are so overwhelmed that they lack the capacity to take enforcement actions on as many dams as may be needed.”
Additional funding is needed to bring dams that do not meet current design criteria into compliance, but rebuilding dams that are 75 years old or older is a complex undertaking, said John Moyle, P.E., M.ASCE, senior project engineer with GEI Consultants and former director of the Division of Dam Safety and Flood Control with the New Jersey Department of Environmental Protection. “The cost is quite prohibitive, and between the states and federal government, no one is investing that type of money,” he said.
PTAP Aerial John Roche, P.E., M.ASCE, ASDSO president and chief of the Dam Safety Permits Division with the Maryland Department of the Environment, said a significant number of private dam owners simply do not have the resources to either rehabilitate or decommission their dams.
“This places a lot of stress on the state regulatory programs to figure out solutions,” he said. “Some states have grant or loan programs to help assist, but they are nowhere near funded to the level needed to help every dam owner.”
With future uncertainty surrounding state funding and federal support, Roche advised that states band together. “The states need to work together, share resources, and use the tools that are available to tackle these problems, which are not going away,” he said.
Rising threats, growing vulnerabilities
Thousands of dams across the U.S. were designed to standards that are less stringent than those of today, leaving many more vulnerable as climate patterns shift and severe storms become more frequent.
“Historically, many dams that are older than 50 years were designed to withstand a 100-year storm,” Moyle said. “However, storms of that magnitude are occurring more often. Older dams that lack sufficient spillway capacity are especially vulnerable to higher-intensity rainfall events.”
Not only are 100-year storms more common, but even larger rainfall events are no longer as rare as once assumed.
As an example, Roche pointed to Ellicott City, Maryland. “In 2016 and then again in 2018, the small historic town experienced 1,000-year storms, resulting in devastating flooding consequences,” he said. “A storm that has a 1-in-1,000 chance of happening each year occurred twice in the span of three years.”
Compounding climate-related challenges are the implications of hazard creep, which refers to the gradual increase in the potential consequences of a dam failure as public or private development expands within the dam’s downstream inundation area.
“In the 30-50 years after many dams were built, the landscapes have changed dramatically,” Roche said. “What was once a rural area below a dam may now include residential development and community facilities like schools and day cares, increasing the potential consequences of a failure. As a result, the dam is reclassified as high hazard – the design of the dam no longer matches the level of risk.”
State and U.S. federal regulations require that dams classified as high hazard or significant hazard have emergency action plans in place. EAPs identify potential emergency conditions and specify actions to take should an emergency occur.
Dam owners are responsible for EAPs, which should be developed in cooperation with emergency response managers, dam safety engineers, and state dam safety officials.
“Accurate inundation maps are critical with EAPs,” Moyle said. “In the event of an incident, they inform the areas that need to be evacuated.”
Moyle, who also chairs ASDSO’s Dam Owner Outreach Committee, said Federal Emergency Management Agency funding through the National Dam Safety Program requires states to conduct public outreach to strengthen dam safety and emergency preparedness.
“This can involve helping dam owners develop EAPs or educating local emergency management coordinators responsible for evacuations,” he said. “Our committee also develops training curriculums, webinars, and other educational materials for dam owners.”
Detecting risks from space
To help identify failure risks at high-hazard U.S. dams, researchers at Virginia Tech are analyzing satellite data to detect signs of potential structural failure. Using interferometric synthetic aperture radar from the Sentinel-1 satellite, the team examined ground movement over a 10-year period, focusing on 41 dams at least 50 feet high.
The analysis detected localized subsidence signals at some of the evaluated dams, indicating possible foundation instability. The researchers combined the satellite data with structural information and publicly available datasets, including U.S. Census data, FEMA’s National Risk Index, and FEMA’s flood inundation mapping.
The results showed that many of the dams facing the greatest risks are near communities with high social vulnerability and limited emergency preparedness. According to the researchers, the findings can supplement dam safety assessments and highlight the urgent need for targeted investment, continuous monitoring, and equitable resilience planning.
As Congress works on passing the Water Resources Development Act of 2026, ASCE has weighed in on its priorities, including reauthorizing the National Dam Safety Program, which was first authorized in 1996.
The silver lining of a dam failure
In May 2020, the Edenville Dam on the Tittabawassee River in Michigan failed following a major rainstorm.
PTAP Aerial Rising reservoir levels caused the aging earthen embankment dam to breach, sending floodwaters downstream where they overtopped and severely damaged the Sanford Dam. No deaths or serious injuries were reported, but roughly 11,000 residents had to be evacuated, and flooding damaged more than 2,500 homes and structures, causing at least $200 million in losses.
While destructive, the failure led to the establishment of the Michigan Dam Safety Task Force, which implemented several policies that improved dam safety in the state, according to Graber.
“The task force helped to strengthen Michigan’s dam safety program, including developing a risk reduction fund, which disperses grants for critical dam repairs and removals,” he said. “That fund now needs to be reauthorized by the state legislature to ensure they sustain the positive changes.”
A similar scenario occurred in South Carolina when Hurricane Joaquin unleashed historic rainfall in October 2015, causing catastrophic flooding across the state and resulting in upward of 50 dam failures.
“The event ultimately led to significant dam safety reforms in the state,” Roche said. “Nobody wants a dam to fail, but the tragic reality is that failures get people’s attention. It’s what often spurs these critical reforms that are needed.”
Get ready for ASCE2027
Maybe you have big ideas about dams or other U.S. infrastructure. Maybe you are looking for the right venue to share those big ideas. Maybe you want to get your big ideas in front of leading big thinkers from across the infrastructure space.
Maybe you should share your big ideas at ASCE2027: The Infrastructure and Engineering Experience – a first-of-its-kind event bringing together big thinkers from all across the infrastructure space, March 1-5, 2027, in Philadelphia.
The call for content is open now through March 18. Don’t wait. Get started today!
