Numerical and physical modelling for a complex stepped spillway

The process for the hydraulic design of the spillway arrangement for the 85 m-high RCC Enlarged Cotter dam (ECD) is presented. Construction began in November 2009, with detailed design scheduled to be completed in March 2010. The spillway design process involved the development of a preliminary design, using theoretical and empirical design methods and published data, analysis and optimization of the arrangement through computational fluid dynamics (CFD) modelling. Ultimately verification and refinement was done using scale physical modelling. The development of key aspects of the design is presented, together with a limited comparison of the results of the numerical and physical modelling.