A new study from the FAMU-FSU College of Engineering has discovered a rising number of U.S. dams at risk of overtopping, emphasizing the need for urgent infrastructure upgrades to protect downstream communities.
The growing risk of overtopping in U.S. dams poses a serious threat to structural integrity and downstream communities, according to recent research from the FAMU-FSU College of Engineering.
In a comprehensive study published in Nature Communications, the research team analyzed data from 33 dams over a span of 50 years, revealing an alarming trend.
The research indicates that the number of dams with critical overtopping probabilities — categorized as low, moderate or high — has increased since 1973, while those with non-critical probabilities have decreased.
“Decades ago, dam builders used the best available technology knowledge, but things have been changing, so aging infrastructure is something that is a concern,” co-author Ebrahim Ahmadisharaf, an assistant professor in the FAMU-FSU College of Engineering, said in a news release. “In this study, we showed where hazards from overtopping are greatest, both because of risk of occurrence and possible consequences. It is a guide to where infrastructure spending could have the greatest impact.”
The Study
The United States is home to over 90,000 dams, varying significantly in size and purpose.
In the study, the researchers focused on a subset of 130 sites with at least 50 years of water level data. From this group, they analyzed 33 dams after excluding those influenced by upstream regulation or with data lacking statistical independence.
The researchers examined water level data relative to the height of the dam crest across multiple 30-year periods within the larger dataset.
Among these dams, 30 were classified as large, exceeding 15 meters in height, and 31 were deemed “high hazard” by the Federal Emergency Management Agency (FEMA), meaning their failure could result in loss of life.
Significantly, the dams with the highest probability of overtopping and proximity to downstream cities were identified in Texas, Kansas and California. These include:
- Canyon Dam: New Braunfels, Texas
- Kanopolis Dam: Marquette, Kansas
- Milford Dam: Junction, Kansas
- Somerville Dam: Somerville, Texas
- Whiskeytown Dam: Anderson, California
- Whitney Dam: Waco, Texas
“We have to plan upfront for this potential risk,” Ahmadisharaf added. “This information can help dam managers to consider whether they need to revisit their emergency action plans and strategy for operating dams.”
Significance of the Findings
Overtopping occurs when stored water surpasses the capacity of a reservoir and flows over the top of the dam. Although this doesn’t necessarily cause immediate failure, it can significantly weaken the structure over time, raising the risk of catastrophic outcomes.
According to the Association of State Dam Safety Officials, 34% of all U.S. dam failures result from overtopping.
Many dams in the U.S. were constructed nearly a century ago, which coupled with changing environmental conditions, creates an urgent need for reassessment. Reflecting this urgency, the American Society of Civil Engineers assigned U.S. dams a D+ rating in its 2025 infrastructure report card.
This particular study concentrated on water levels and dam height, excluding other crucial factors such as spillway capacity and sedimentation buildup due to data limitations. Future studies incorporating these elements would provide a more holistic view of overtopping risks.
“This study represents the first step toward a comprehensive assessment of dam overtopping probabilities in the U.S. Understanding this potential risk is crucial for protecting communities and prioritizing dam rehabilitation before catastrophic failures occur,” added co-author Eunsaem Cho, a former postdoctoral researcher at FSU and now a research associate at NASA Goddard Space Flight Center.
The findings underscore the pressing need for infrastructure investment and strategic planning, reinforcing the critical role of ongoing research in safeguarding communities and upgrading aging dam structures.
Source: Florida State University