Willisburg Lake Dam Spillway Design – The Importance of a Multi-Faceted Design Approach

ABSTRACT ONLY - Dam and spillway design rely on standardized methods that provide a structured approach to hydraulic analyses. These methods, including empirical equations and numerical models, incorporate assumptions about the site conditions. However, these assumptions may not always align with real-world conditions, potentially leading to design inefficiencies or safety concerns. This presentation explores how the limitations of standardized methods were addressed in the design of Willisburg Lake Dam in Washington County, Kentucky. Willisburg Lake Dam is a high hazard structure which retains the main water supply for the City of Springfield, KY. The rehabilitation design objective included increasing spillway capacity that will minimize property acquisition, limit future Operations and Maintenance requirements for the owner, and limit impacts to the surrounding infrastructure. Surrounding infrastructure included a marina, a parking lot, private driveways, a pump station, and State Highway 555 which crosses over the dam crest. The proposed solution included a new reinforced concrete spillway through the center of the embankment as well as a flood wall which also served as a traffic barrier. The proposed spillway consists of box culverts discharging to a stair-stepped chute and concrete stilling basin. This design offered the least amount of design risk, minimized impacts to the surrounding areas, and lowered construction costs when compared to other alternatives. However, the design also included several hydraulic elements that are not included in standard design approaches. This presentation will emphasize the importance of multi-faceted design verification to ensure reliability on the auxiliary spillway design approach which evaluated 6 alternatives. The role of computational fluid dynamics (CFD) on the spillway and stilling basin design will be presented including a discussion on the capabilities of CFD modeling (when to use it and its limitations).