The largest ever recorded inflows for the dam occurred in January 2011. On 11 January 2011, Wivenhoe Dam reached its highest level ever, 191% of normal water supply storage capacity, as it held back floodwater. Because it is an embankment dam, it was not designed to spill over its crest or overtop and there is a risk that if waters spilled over the crest, this could erode the dam wall and potentially cause the dam to fail. In this scenario the water level would need to rise to 225% capacity. To prevent this, the dam was designed and built to include a second emergency spillway. During the peak of the flooding event the dam water level reached below the auxiliary spillway height.