SOUTH PACIFIC DIVISION
PHOTO BY DENA O’DELL, U.S. ARMY CORPS OF ENGINEERS LOS ANGELES DISTRICT PUBLIC AFFAIRS
LOS ANGELES DISTRICT TAKES PROACTIVE APPROACH IN PRIORITIZING HIGH-RISK DAMS BY DENA O’DELL AND LUCIANO VER A , Los Angeles District
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hen most people think about extreme weather events in Southern California, earthquakes and wildfires might come to mind. Although both of these natural, and, sometimes, man-made disasters do happen frequently in the arid Southwest, another kind of disaster, often overlooked but with potentially devastating effect to the state, is from periodic flooding. Whether in the coastal areas of California, inland, or in the valley, all 58 counties in California have experienced at least one significant flood event in the past 25 years, according to the California Department of Water Resources. These floods result in loss of life and billions of dollars in damages. With a large population living near or downstream of dams, these urban sprawls – coupled with the right mixture of heavy rainfall – can equal disaster. That is one of the reasons the U.S. Army Corps of Engineers (USACE) Los Angeles District is being proactive by reassessing its inventory of dams. “Public safety is our No. 1 priority,” said Col. Aaron Barta, commander of the Los Angeles District. “The primary objective of the Corps’ Dam Safety Program is to review our dams and ensure resources are prioritized to address the highest risks.” Dams are assigned Dam Safety Action Classification, or DSAC, risk ratings of 1 to 5, with 1 being “very high urgency,” 2 being “high urgency,” 3 being “moderate urgency,” 4 being “low urgency,” and 5 being “normal.” USACE defines “high urgency” as dams where failure could begin during normal operations or be initiated as the consequence of an event. The likelihood of failure from one of these occurrences, prior to remediation, is too high to assure public safety. In the last several months, the Los Angeles District’s Dam Safety Program has reclassified two of its dams – Whittier Narrows and Prado – and is reassessing several more.
U.S. Army Corps of Engineers Los Angeles District Whittier Narrows Dam Lead Project Engineer Doug Chitwood, left, and Whittier Narrows Dam Project Manager George Sunny, right, pose for a picture near the spillway gates of Whittier Narrows Dam during an interview with a Los Angeles Times reporter in January 2019 at the dam in Pico Rivera, California.
WHITTIER NARROWS Whittier Narrows Dam, located in Pico Rivera, California, is one component of a complex Los Angeles County Drainage Area flood risk management system that consists of five dams, 33 debris basins, and 180 miles of main and tributary channels. USACE recently completed a draft for the Whittier Narrows Dam Safety Modification Study that recommends important modifications to the dam to ensure it continues to reduce flood risk for 1.2 million people living downstream from it. The dam, built nearly 60 years ago, continues to perform as it was designed; however, due to the combination of the potential loss of life with a very high likelihood of failure during a rare flood event, it was reclassified from a DSAC 2 to a DSAC 1, from high urgency to very high urgency. The study showed should this rare flood occur, the dam could fail through erosion underneath or even overtopping, putting the population downstream at risk. “The dam was designed consistent with the standards of the day and it has succeeded in reducing flood damages,” said lead project engineer Doug Chitwood. “However, floods larger than we have experienced since the dam was built will occur at some point. The proposed modification project and community preparation are key components in reducing the flood risk.” The Los Angeles District continues to seek opportunities to communicate with the public and its partners about the importance of the study and the value of the dam to Southern California. Downstream 101
