In February, operators of Oroville Dam in California noticed damage to the concrete spillway. Record precipitation meant the dam was at 150% of historic holding capacity. Water was released through the compromised spillway resulting in a breach which caused erosion and mandatory flood evacuations.
Engineers at Utah State Universities’ Water Lab were asked to build a physical model in both the damaged and newly constructed forms. Faculty Researcher Mike Johnson considers physical models the gold standard for planning dam construction.
“The flow of water is very complex, and momentum is transferred at the molecular level," he said "We haven’t got enough computing power in the world to model that many molecules at once, and so we turn to physical models. Numerical models are getting better, and they are a very valuable tool, but we still turn to physical models.”
The model was built 50 times smaller than the actual dam, replicating a vertical drop of 750 feet. It is the largest model built at the water lab and it is attracting attention from hydrologists across the world.
“This is a significant dam in the United States, and it’s the tallest dam and that brings its own specific challenges," Johnson said. "We have folks across the worlds that are really looking at what’s happening at Oroville and we are helping them to understand what’s going on so dam safety can be improved across the globe.”
The model will be tested with floods of up to 270,000 cubic feet per second, the same magnitude as the largest flood at Oroville since 1995. Reconstruction includes increased aeration to reduce pressure at high flows, but overall dam design remains the same.