Abstract Description: The Spillway Raise Project at Schafer Dam, California, presented unique challenges in hydraulic design due to site constraints, geological complexities, and an accelerated timeline. This paper discusses the unconventional application of HEC-RAS 2D modeling in the design process of a curved ogee spillway, comparing its results with Computational Fluid Dynamics (CFD) and physical modeling approaches. The project aimed to increase the dam's capacity and safety by raising the spillway crest by 10 feet and introducing a curved ogee weir. Faced with strict timelines and the need for rapid decision-making, the design team adapted HEC-RAS 2D modeling to explore multiple design alternatives efficiently. This approach, while unconventional for ogee structures typically modeled in 3D, proved valuable in the initial design phases. The study implemented a fine mesh resolution to capture the complex curvature of the ogee weir and developed a comprehensive full reservoir-scale model considering Probable Maximum Flood (PMF) inflows. Results from the HEC-RAS 2D model were compared with CFD simulations and physical model experiments, revealing both the strengths and limitations of the 2D approach.
