City of Irvine
2020 Local Hazard Mitigation Plan
Figure 3-1: Dam Inundation Areas
The most recent incident that occurred in California is the Oroville Dam spillway failure that occurred in February 2017. The failure in the concrete chute caused a 60-foot-deep hole to develop in the lower third of the primary spillway as a result of normal operations undertaken to lower the reservoir in advance of a moderately large storm. A subsequent storm in the days after the initial incident and the inability to fully use the primary spillway led to the filling of the reservoir and the use of its unlined (natural) emergency spillway for the first time ever. After two days of usage causing erosion of the unlined hillside and head cutting (erosion upstream towards the earthen dam), concerns regarding the stability of the emergency spillway caused an evacuation of nearly 200,000 people downstream prompting both immediate repairs and a re-evaluation of this dam facility and many others throughout the State of California since. 34 The City of Irvine has not suffered impacts from a dam inundation event. The closest incident to Irvine involved an extensive episode of winter rains in 2005 that caused seepage along Prado Dam, causing the Army Corps of Engineers to release significant amounts of water downstream, forcing evacuations of approximately 3,000 residents. The flooding caused erosion along portions of the Green River golf course adjacent to the river. Since this event, the ACOE has made significant improvements downstream of the dam to increase capacity and reduce future flooding impacts. 35
37
Made with FlippingBook HTML5