According to one expert, mega-storms L.A. could submerge a dam and flood dozens of cities

In each case, catastrophic floods could extend from Pico Rivera to Long Beach, flooding cities like Artesia, Bell Gardens, Bellflower, Carson, Cerritos, Commerce, Compton, Cypress, Downey, Hawaiian Gardens, La Palma, Lakewood Long Beach, Lynwood, Montebello, Norwalk, Paramount, Rossmoor, Santa Fe Springs, Seal Beach and Whittier. Authorities say that one million people could be affected.