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A step in the right direction: New flow depth relationships for stepped spillway design

Sherry L Hunt, Kem K Kadavy, Greg J Hanson
Dam Safety 2012. Proceedings of the Association of State Dam Safety Officials Annual Conference 2012 pp. -
air, concrete, dams (hydrology), energy, water flow, Oklahoma
A common deficiency for embankment dams changing from a low hazard to a high hazard dam is inadequate spillway capacity. Roller compacted concrete (RCC) stepped spillways are a popular method to address this issue. Stepped spillway research has gained momentum in recent years due to the need for design guidance when an RCC spillway is retrofitted to an existing embankment. Researchers at the USDA-ARS Hydraulic Engineering Research Unit (HERU) in Stillwater, OK are conducting generalized research on RCC stepped spillways to provide the design guidance necessary to determine stepped spillway design parameters including inception point, flow depth, air entrainment, and energy dissipation. The research has shown the normalized clear water flow depth downstream of the inception point is a function of chute slope and the ratio of step height to critical depth, and the normalized flow depth upstream of the inception point is a function of chute slope, the ratio of step height to critical depth, and the normalized length from the crest. The objective of this paper is to introduce two new relationships that can be used to determine the flow depth at any location upstream and downstream of the inception point for stepped spillways on embankment dams.