Laguna Beach police also reported rockslides in canyon areas and urged residents to remain in their homes for now and avoid downtown, portions of which were under several feet of water.
Numerous Orange County roads were partially or fully closed, including Ortega Highway, the toll road California 241 and Pacific Coast Highway in Newport Beach. In Silverado Canyon, the Orange County Fire Authority was responding to reports of rock and boulder slides. Silverado has experience major flooding and rock slides in previous heavy downpours.
The incidents came as Los Angeles braced for another powerful storm. Wednesday's storm was projected to be the most intense of the week, the result of a powerful, cold storm from the Gulf of Alaska colliding with a river of subtropical moisture from the western Pacific Ocean.
"When you get the very cold air mixing in with the very warm air, it can be quite volatile," said Bill Patzert, a climatologist at the Jet Propulsion Laborator
Patzert said Wednesday was "definitely going to be the main event." Rainfall rates were expected to be as high as three-quarters of an inch to 1 1/2 inches per hour, which could cause flooding not only in foothills and mountains but also in low-lying areas, said Stuart Seto, a specialist with the National Weather Service in Oxnard.