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The quantity of dams in the United States susceptible to overtopping is growing, jeopardizing their structural stability and nearby communities, as stated in new findings from the FAMU-FSU College of Engineering.
The investigation, released in Nature Communications, analyzed data from 33 dams over half a century to ascertain changes in overtopping likelihood since 1973. The findings indicated a rising trend in the number of dams with significant overtopping probabilities (low, moderate, and high), alongside a reduction in the dams with non-critical overtopping probabilities (very low).
“Years ago, dam constructors employed the most advanced technology available, yet conditions have evolved, making aging infrastructure a significant concern,” mentioned co-author Ebrahim Ahmadisharaf, an assistant professor at the FAMU-FSU College of Engineering and the Resilient Infrastructure and Disaster Response Center. “In this research, we identified where overtopping hazards pose the highest threat, considering both the likelihood of occurrence and possible aftermaths. It serves as a roadmap for where infrastructure investment could yield the most substantial benefits.”
WHAT THEY DID
There exist over 90,000 dams of diverse sizes across the nation. The researchers concentrated their study on a limited selection of around 130 sites that had a minimum of 50 years of publicly accessible water level data. They filtered out dams affected by upstream regulation or those with statistical dependence in water level data, resulting in 33 sites for analysis.
The team evaluated water level data from the selected dams and contrasted that data with the height of the dam crest. They assessed every 30-year segment within the broader 50 years of data to approximate how the likelihood of overtopping has evolved over time.
Among the 33 dams examined, 30 were classified as large, having crest heights exceeding 15 meters, as per the criteria set by the International Commission on Large Dams. Additionally, 31 dams were deemed “high hazard” according to the Federal Emergency Management Agency (FEMA), indicating that their failure could lead to loss of life.
The six dams with the highest likelihood and the nearest downstream urban areas were situated in Texas, Kansas, and California:
- 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 must strategize in advance for this potential hazard,” Ahmadisharaf emphasized. “This data can assist dam administrators in determining whether they need to revise their emergency action plans and the approach to managing dams.”
WHY IT MATTERS AND FUTURE DIRECTIONS
Overtopping happens when the volume of water surpasses a reservoir’s capacity and spills over the edge. While this may not result in immediate damage or failure, it compromises the dam’s structure and may heighten the risk of catastrophic failure if it persists. Incidents of overtopping caused by insufficient spillway design, debris obstructing spillways, or settling of the dam crest account for roughly 34% of all U.S. dam failures, as reported by the Association of State Dam Safety Officials.
A significant quantity of U.S. dams were constructed nearly a century prior. Deteriorating structures and evolving hazards further amplify the risk for this essential infrastructure. In its 2025 infrastructure report card, the American Society of Civil Engineers rated U.S. dams with a D+ grade, highlighting the immediate need for reevaluation and modernization.
This analysis solely focused on water levels and dam height. Other elements affecting the likelihood of overtopping include spillway capacity, sediment accumulation, and inflow rate, but information regarding these components was lacking. The article concentrated on overtopping probability without estimating potential impacts and risks. Future studies incorporating these factors would enhance the rigor of the research.
“This investigation marks the initial phase toward a comprehensive evaluation of dam overtopping probabilities in the U.S. Grasping this potential risk is vital for safeguarding communities and prioritizing dam upgrades before catastrophic failures transpire,” stated co-author Eunsaem Cho, a former FSU postdoctoral researcher currently serving as a research associate at NASA Goddard Space Flight Center.
The post FAMU-FSU research identifies U.S. dams at highest risk of overtopping was first published on Florida State University News.
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