Historic Rainfall May Exacerbate Palos Verdes Landslide Area ‘In A Matter Of Weeks’

Driving down Palos Verdes Drive South can be a different experience every day. Some days the road dips, other days it’s a smoother drive. That’s because land movement in the Portuguese Bend/Abalone Cove area in the city of Rancho Palos Verdes has been accelerating, according to city geologist Michael Phipps.

That area, he said, has shifted around 7 feet of in the last 15 months, with half of that movement happening since October.

Phipps added that the large landslide in the area that's 1.5 miles wide by 1 mile long is “failing into the ocean.” The slide is over 100 feet deep and the effects of the recent historic Southern California storms will reveal themselves “in a matter of weeks.”

The real effects of the storm, he said, will be felt when the rainwater infiltrates deep underground and starts affecting the land movement.

What would impacts look like?

“If the landslide continues to accelerate the way it has been over the last 15 months, it's going to start creating more issues with roads and with infrastructure, utilities,” Phipps said.

Two homes have been red tagged in the area since early 2023. And Rancho Palos Verdes City Manager Ara Mihranian said that over the last year the city has received several reports from residents in the area regarding gas leaks and power disruptions.

He said crews have gone from repairing the Palos Verdes Drive South stretch every quarter to “every couple of weeks."

Rain season is not over

While land movement in the area has been accelerating since 2018, the effects of last year’s rainy season are being seen now.

“Last year's rainfall was about 220% of the average for that area, so they had almost 26 inches of rain on the top of the mountains there,” Phipps said.

And with six weeks of “typically the wettest portion of the winter” left this year, “we’re worried about it, we’re concerned,” he said.

To slow down and stop a landslide, the city has been taking the water out of the ground. At the landslide in Portuguese Bend, he said almost a quarter million gallons of water is being pumped out daily.

With rain expected in the coming weeks, Mihranian added that the city is taking short-term measures, such as filling fissures with soil and sand and putting tarps over areas susceptible to water entering the ground.