Due to its location between the Pacific Ocean and the high San Gabriel Mountains, the Los Angeles Basin is subject to flash flooding caused by heavy orographic rainfall from Pacific storms that hit the mountains. Up to 1 million people in the Los Angeles metropolitan area could be flooded by a dam failure, and water levels higher than 20 feet would affect Pico Rivera, a city of 63,000 inhabitants that lies downstream. Flooding is one of the most common hazards in the United States and certain parts of Los Angeles County. Researchers at the University of California at Los Angeles found that climate change is doubling the chances of biblical flooding in The Golden State.
In fact, UCLA scientists discovered that a month-long extreme storm like the one that drowned Sacramento and flooded modern Los Angeles in 1862 could bring several feet of rain hundreds of miles from California. In an article published in the Los Angeles Times in February, Swain said the Whittier Narrows Dam is “one of many pieces of water infrastructure that may not rise to the challenge of the brave new climate of the 21st century. As a result, a flood like the one that occurred in 1862 would leave “parts of cities such as Sacramento, Fresno and Los Angeles. Los Angeles County residents, renters and business owners, including people with disabilities and others with functional and access needs, can call 211 Los Angeles County for information on emergency preparedness and other referral services.
A sobering example of California's infrastructure vulnerability to an ArkStorm is the possible failure of the Whittier Narrows Dam on the San Gabriel River in the Los Angeles metropolitan area. According to the study, a similar flood would now displace 5 to 10 million people, cut off the state's major highways for perhaps weeks or months with massive economic damage, and submerge major cities in the Central Valley, as well as parts of Los Angeles.
