Dam Overtopping Protection Systems Part I: On-Demand

This is the first of a two-part series on overtopping protection systems for embankment and concrete dams. Many dams today have insufficient spillway capacity and may be overtopped during large floods below the regulatory requirement. In recent years, dam overtopping protection has become increasingly popular as a means to provide additional flood release capacity when more conventional methods such as increasing spillway discharge capacity or reservoir storage are cost prohibitive or impractical. This course will present many of the overtopping protection systems currently in use, describing for each their range of design applications, construction considerations, and potential limitations and risks. Using FEMA’s 2014 Technical Manual: Overtopping Protection for Dams as a guide, the two most commonly used systems today, roller-compacted concrete (RCC), and articulating concrete blocks (ACB) will first be presented, followed by various reinforced concrete, turf, and rockfill alternatives for embankment dams. The course will conclude with special applications for concrete dams. Part 2 explores the performance of various systems in hydraulic model studies. 

Key takeaways:

  1. Exposure to a wide range of potential overtopping protection systems for dams.
  2. Case histories of design applications and performance.  
  3. Limitations of use, including infrequent operation and/or low hazard conditions.  
  4. Advantages of one system relative to the others, including cost.  
  5. Current research and development of new systems or system refinements worldwide. 

Tom Hepler

Schnabel Engineering, LLC,Senior Consultant

Tom Hepler retired from the Bureau of Reclamation in 2014 with 36 years’ experience in hydraulic and structural engineering designs for concrete dams and appurtenant structures.  He served as Technical Specialist for the Waterways and Concrete Dams Group in Denver, Colorado, and as Team Leader for numerous concrete and embankment dam modifications for dam safety.  Tom is a co-author of Alternatives for Overtopping Protection of Dams, an ASCE publication released in 1994, and Technical Manual: Overtopping Protection for Dams, a FEMA document released 20 years later, in 2014.  Tom currently works for Schnabel Engineering in Greensboro, North Carolina. He is a registered Professional Engineer in four states, and has a Bachelor’s degree in Civil Engineering from Missouri S&T.  

 

Selecting Dam Overtopping Protection over Traditional Methods to Pass Design Floods 

Overview of Common Overtopping Protection Systems for Embankment Dams 

Roller-Compacted Concrete (RCC) 

Articulated Concrete Blocks (ACB) 

Grass and Reinforced Turf 

Riprap and Reinforced Rockfill 

Continuously-Reinforced Concrete (CRC) 

Other Systems – Wedgeblocks, Gabions, Fabriform, and Geomembranes 

Overview of Overtopping Protection for Concrete Dams 

Conclusions

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