ARS | Publication request: ARS Rcc Spillway Research Relative to Small Watershed Dams

Submitted to: Research Coordination Meeting
Publication Type: Other
Publication Acceptance Date: April 28, 2009
Publication Date: N/A

Technical Abstract: The USDA-Natural Resources Conservation Service (NRCS) has provided both financial and technical assistance for the construction of over 11,000 flood control dams through the Small Watershed Program. Approximately 1,100 of these watershed structures are expected to use stepped spillways for increasing spillway capacity, yet generalized design guidelines for these stepped spillways has been very limited. The USDA-Agricultural Research Service (ARS) Hydraulic Engineering Research Unit (HERU) has provided research in support of the technical assistance offered by the NRCS. The research conducted by the ARS-HERU has included the study on the hydraulics of vegetated-lined channels, trash guards for closed conduit spillway entrances, hood inlet pipe spillways, box inlet drops, riprap sizing downstream of cantilever pipe outlets, and rock chutes to name a few. Additionally, ARS-HERU has worked hand in hand with the NRCS and Kansas State in the development of SITES, Water Resource Site Analysis software. More recently scientists at HERU have researched the use of roller compacted concrete (RCC) stepped spillways as an alternative for increasing spillway capacity for aging watershed structures. HERU has been engaged in both specific and generalized model studies with emphasis in converging stepped spillways and energy dissipation and air entrainment on relatively flat (less than 25 degrees) stepped spillways. Both empirical and theoretical relationships have been developed to determine training wall height for converging stepped spillways. Additionally, relationships for determining inception point location and energy dissipation in stepped spillways with slopes less than 25 degrees have been developed. This research is expected to assist engineers with the design of stepped spillways applied on relatively flat embankment dams and the associated stilling basin located at the toe of the spillway.