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Title: Physical model study of a RCC stepped spillway for Renwick Dam, North Dakota

Author
item Hunt, Sherry
item Kadavy, Kem

Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: 6/1/2007
Publication Date: 6/17/2007
Citation: Hunt, S., Kadavy, K.C. 2007. Physical model study of a RCC stepped spillway for Renwick Dam, North Dakota. In: ASABE Annual International Meeting, June 17-20, 2007, Minneapolis, Minnesota. Paper No. 072155. 2007. CD-ROM.

Interpretive Summary: Many of the flood control structures constructed under the financial and technical support of the Natural Resources Conservation Service (NRCS) were originally designed to protect agricultural land. Through the years, land development around these structures has caused a change in hazard classification, causing some of these structures to have inadequate spillway capacity. Urbanization, land use changes, and unobtainable land rights have limited the possibilities of altering the dimensions of the existing embankment and spillways; consequently, roller compacted concrete (RCC) stepped spillways overlying the existing embankment are becoming a more popular choice for addressing the needs of these structures. The North Dakota NRCS requested a specific model study of a RCC stepped spillway proposed for the rehabilitation of Tongue River Dam M-4, also known as Renwick Dam. The USDA-ARS Hydraulic Engineering Research Unit (HERU) constructed a section of a physical model of a stepped spillway as proposed by the North Dakota NRCS. The goal of the study is to provide design recommendations for the stepped spillway chute and associated energy dissipating stilling basin. This research is expected to impact the development of design guidelines for stepped spillways and associated stilling basins planned on relatively flat slopes (theta less than or greater than 22 degrees).

Technical Abstract: Many of the flood control structures constructed under the financial and technical support of the Natural Resources Conservation Service (NRCS) were originally designed to protect agricultural land. Through the years, land development around these structures has caused a change in hazard classification, causing some of these structures to have inadequate spillway capacity. Urbanization, land use changes, and unobtainable land rights have limited the possibilities of altering the dimensions of the existing embankment and spillways; consequently, roller compacted concrete (RCC) stepped spillways overlying the existing embankment are becoming a more popular choice for addressing the needs of these structures. The North Dakota NRCS requested a specific model study of a RCC stepped spillway proposed for the rehabilitation of Tongue River Dam M-4, also known as Renwick Dam. The USDA-ARS Hydraulic Engineering Research Unit (HERU) constructed a two-dimensional, 1:8 scale physical model to evaluate the energy dissipation of a section of the structure. The proposed spillway entrance consists of a broad crested weir, with flow continuing down a 4(H):1(V) stepped chute. Prototype step heights ranging from 0.3 m (1 ft) to 0.61 m (2 ft) will be tested to compare the influence on energy dissipation. Stepped spillways provide a significant amount of energy dissipation compared to relatively smooth spillways, and larger steps are expected to create more energy dissipation than smaller steps. Additionally, stepped spillways require shorter stilling basins than smooth spillways, and the step height influences the stilling basin design. This research is expected to impact the development of design guidelines for stepped spillways planned on relatively flat slopes (theta less than or greater than 22 degrees).