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Research Project: Development of Engineering Tools for the Design and Rehabilitation of Safe, Efficient Embankment Protection Alternatives, Hydraulic Structures, and Channels

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Title: Observations on dam overtopping protection: RCC stepped spillway research

item Hunt, Sherry
item Kadavy, Kem

Submitted to: The Journal of Dam Safety
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2017
Publication Date: 5/1/2018
Citation: Hunt, S., Kadavy, K.C. 2018. Observations on dam overtopping protection: RCC stepped spillway research. The Journal of Dam Safety. 15(3):17-23.

Interpretive Summary: The USDA-Natural Resources Conservation Service (NRCS) has provided technical and financial assistance for the construction of nearly 12,000 dams across the U.S. While many of these dams were originally built to protect agricultural land, land changes have occurred, and many dams are now surrounded by residential communities and infrastructure. As embankment dams across the U.S. age, the dam safety community has stayed vigilant to address deficiencies that may arise as these dams approach the end of their planned service life. Some aging dams are at risk for overtopping as sediment encroaches upon flood storage. Design engineers work to develop innovative designs for overtopping protection. Scientists at the USDA-Agricultural Research Service, Hydraulic Engineering Research Unit have provided technical support for the development of standard design criteria for overtopping protection of embankment dams. This manuscript describes some of the observations from multi-year studies on one overtopping protection system, roller compacted concrete stepped spillways. This research is expected to extend the life and benefits for nearly 10% of the 12,000 flood control dams constructed with the assistance of USDA-NRCS.

Technical Abstract: Research conducted over the last decade has led to improved understanding on the design and hydraulic performance of stepped spillways applied to embankment dams for overtopping protection. This research has demonstrated that the free-surface air entrainment inception point (Li), step height to critical flow depth ratio (h/dc), chute slope (theta), clear water flow depth (ycw), and air concentration (C) are vital parameters in the design of stepped chutes applied to embankment dams as well as the associated stilling basin for these structures. Relationships based on data obtained from this research have led to improved designs criteria for these structures and addressed knowledge gaps on their performance. Correct and proper interpretation of the data are vital to limit the introduction of scale effects into the results.