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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: Closure to "Estimated splash and training wall height requirements for stepped chutes applied to embankment dams" by Sherry L. Hunt and Kem C. Kadavy

Author
item Hunt, Sherry
item Kadavy, Kem

Submitted to: American Society of Civil Engineers Journal of Hydraulic Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2018
Publication Date: 9/4/2018
Citation: Hunt, S.L., Kadavy, K.C. 2018. Closure to "Estimated splash and training wall height requirements for stepped chutes applied to embankment dams" by Sherry L. Hunt and Kem C. Kadavy. American Society of Civil Engineers Journal of Hydraulic Engineering. 144(11):07018019. https://doi.org/10.1061/(ASCE)HY.1943-7900.0001373.
DOI: https://doi.org/10.1061/(ASCE)HY.1943-7900.0001373

Interpretive Summary: Stepped chutes are an overtopping protection system that may be applied to existing embankment dams. These stepped chutes are often designed for the full length of the dam, so the width is considered wide in relation to the flow depth expected within the chute. Excess splash may occur in extremely narrow stepped chutes. Narrow stepped chutes may be more commonly used for grade stabilization. An engineering designer should consider the width of their design to determine if it will influence the flow behavior in the center of a chute.

Technical Abstract: Researchers from Hohai University in Nanjing, China compared stepped chute research conducted in physical models of narrow stepped chutes to research conducted by scientists at the USDA-ARS Hydraulic Engineering Research Unit (HERU) in a physical model of a wide stepped chute. Researchers from Hohai University indicate the design guidance provided by HERU scientists for stepped chute training walls may be extended to chutes with slopes ranging from 10 to 40 degrees. Hohai University researchers caution designers that rooster-tailing and shockwaves may occur as it was observed in their studies. However, HERU scientists did not observe this behavior. HERU scientists adhered to hydraulic modeling recommendations by designing the stepped chute physical model width to flow depth ratio greater than five. By doing so, the channel sides did not disrupt the velocity distribution in the central region. The researchers from Hohai University violated this recommendation in several experiments. The research conducted at the HERU is expected for use in the design of stepped chutes applied to embankment dams, which are typically wide chutes where one would not expect to observe rooster-tailing or shockwave development. HERU researchers agree with Hohai University researchers that a designer needs to consider the chute width to determine if side walls are expected to disturb the velocity distribution in the center of the channel.