California Dam Spurs Flood Planning & Emergency Response Funding
After the Army Corps of Engineers deemed the Whittier Narrows Dam unsafe, cities downstream must begin flood planning.
In 2008, the Army Corps of Engineers gave the Whittier Narrows Dam in California its second-worst rating, a Dam Safety Action Class II (DSAC II), after inspection revealed that the dam was at risk of failing during normal operations, foreshadowing a need for downstream flood planning and a focus on emergency response to flooding.
The assessment stated that the dam was at risk of failure due to damage from seismic activity and erosion at the foundation. Nearly eight years later, the dam was reclassified into the worst category, DSAC I, and deemed "unsafe" and "critically near failure," prompting cities downstream that were caught off guard by the upgraded assessment to prepare for a breach by kicking flood planning into high gear.
The Army Corps of Engineers cited three major reasons for its 2016 rating of the Whittier Narrows Dam:
- Premature opening of the spillway gates due to mechanical error
- "Backward erosion piping" of the foundation, originally used for dams for short-term needs
- Overtopping, which is when a dam fails catastrophically as water crests and spills over its top
For Pico Rivera City Manager Rene Bobadilla, the issue of flood planning lies with the multitude of unknowns.
If we had to evacuate what would that look like? What would be the route to travel?” she said in an interview with KPCC. “How much flooding will occur if that there was ever a major breach? And where would the shelters be?”
The city of Pico Rivera is using $200,000 in grants for emergency flood planning, including funding from Round 2 of California's flood emergency response grants program. Pico Rivera is in the process of designating shelters and solidifying traffic patterns for evacuating citizens.
Other cities in the path of flood waters from a potential dam breach have not finalized or publicized their flood plans.
The dam could fail in two different ways, either by the automatic spillway gates opening prematurely, or if erosion further damages the earthen dam foundation.
A round 3 for the statewide emergency response grants is imminent, according to the state website.