Submitted to: ASABE Annual International Meeting
Publication Type: Other
Publication Acceptance Date: 8/10/2011
Publication Date: N/A
Technical Abstract: Stepped spillways applied to embankment dams are becoming popular for addressing the rehabilitation of aging watershed dams, especially those situated in the urban landscape. Stepped spillways are typically placed over the existing embankment, which provides for minimal disturbance to the original embankment and the surrounding landscape. Significant energy dissipation occurs in stepped spillways; thereby, allowing for a smaller stilling basin footprint as compared to traditional smooth spillways. The original focus of stepped spillway research was on gravity-styled dams such that the slope is steeper than 2(H):1(V). Embankment dams most commonly have slopes flatter than 2(H):1(V), so in recent years, the research focus has shifted to these spillways applied to embankment dams. Design engineers have raised questions related to flow depth and energy dissipation in stepped spillways applied in these flatter sloped situations. Researchers at the USDA-ARS Hydraulic Engineering Research Unit have conducted a large-scale physical model study on a stepped spillway with a 3(H):1(V) slope. Step heights ranging from 3/4 to 12 inches were tested, and the unit discharged varied from 1.7 to 20 cfs/ft. Step height manipulation can result in a change in the inception point location, and the distance from the downstream edge of the broad-crested weir to the inception point provides a direct link for determining the energy dissipation and flow depth in the stepped spillway. The objectives of this paper are to provide preliminary stepped spillway physical model results of flow depth and energy dissipation as they relate to the inception point.