Los Angeles County Fire Department officials said the boulder hit the side of the woman's vehicle, and she was transported to a nearby hospital with complaints of pain. The force was so strong, you could see the inside of the passenger door from the outside.
Malibu Canyon Road was closed between Civic Center Way and Piuma Road. Morning commuters that use the road should consider alternative routes, sheriff's officials said.
Only Malibu Knolls residents with identification were being allowed through the road closure at Malibu Canyon Road and Civic Center Way.
Three straight days of rain brought down rocks on Malibu Canyon on multiple spots, stranding some drivers. Ralph Maldonado with L.A. County Public Works said the boulder that hit the vehicle likely weighs two or three tons.
The slide happened just one day after another rockslide shut down a lane on Malibu Canyon Road.
Nearby Topanga Canyon Boulevard was shut down from PCH to Grand View Drive due to a mud and rock slide. The closure was expected to last through at least noon Thursday, Caltrans said.
Earlier in the day, Malibu residents were doing what they could to protect their properties from the Southern California storm. Evacuations were still underway for properties adjacent to steep hillsides, which are most at risk for mudslides and debris flows.
Schools in Malibu were closed as a precaution on Tuesday and Wednesday, and Santa Monica - Malibu Unified School District officials announced the closure will remain once again on Thursday.
The Malibu area was hit hard by the Woolsey Fire in November, leaving hillsides bare and less able to absorb the flow of water during a storm.
While there was a break in the rain on Wednesday, Caltrans crews near the Los Angeles/Ventura County line were shoring up the burned out hillside along Pacific Coast Highway. Along the stretch, only one lane in each direction was open. The work included putting in drainage pipes and using sandbags to divert any mud and debris flow away from the road. Crews were also aware of the sensitive nature there, as they were working around an ancient Indian burial site.
At Zuma Beach, locals were taking advantage of the break of the rain by loading their cars and trucks with sand bags.
The recent storms have already caused a muddy mess on major roads. Pacific Coast Highway was shut down for hours Monday following a mudslide.
Some residents said that after their homes survived the Woolsey Fire, they're hopeful they'll survive the rains. What's giving them hope, as one resident said, is the new vegetation that's popping up in patches along the burned hillsides.
A mandatory evacuation order went into effect starting Tuesday morning in these communities:
Corral Canyon / El Nido
Escondido / Old Chimney
Escondido Drive / Latigo Canyon
Malibu West / Trancas Canyon
All of Ramirez Canyon Road and adjacent streets
Paradise Cove Mobile Home Park and Restaurant
Two evacuation centers for Malibu residents opened Tuesday: the Agoura Hills/Calabasas Community Center (27040 Malibu Hills Road, Calabasas); and Santa Monica High School (601 Pico Blvd.).
The schools closed include:
Juan Cabrillo Elementary School, Point Dume Marine Science School, Webster Elementary School and Malibu Middle and High School. This includes the preschool, and the Boys & Girls Club of Malibu is also closed. (All Santa Monica Schools remain open.)