Geotechnical Fight Back to Mitigate the Once Thought Unstoppable Landlide in Rancho Palos Verdes

The Portuguese Bend landslide complex in Rancho Palos Verdes, California, has been a persistent geological issue, causing significant damage and disruption. Following years of above-average rainfall, the landslide's movement intensified dramatically. While the land shifted at rates of up to 12 inches per week during the summer, the introduction of a deep dewatering program has slowed it significantly to an average of 8 inches per week. Despite this improvement, the movement remains 80 times faster than in 2022, continuing to affect over 200 homes with power and gas outages. Residents in neighborhoods like Seaview and Portuguese Bend Beach Club have been forced to adapt, some by relocating and others by installing generators and solar panels.

To address the issue, city leaders have implemented temporary measures and allocated $4 million to mitigate the impact during the upcoming winter season. These measures include filling fissures in Altamira and Klondike Canyons with soil and bentonite seals to prevent water infiltration, which is a key trigger for land movement. Additionally, the deep dewatering program—featuring six wells removing 600 gallons of water per minute—has proven effective in reducing the slide's pace. Preliminary data confirms that the dewatering initiative is having a measurable impact, offering hope for long-term stability in the area.

Los Angeles County has dedicated $5 million for recovery and support efforts, with $2.8 million allocated to financial grants for affected residents. These grants, up to $10,000 per household, can be used for generators, property repairs, temporary housing, or storage costs. The remaining funds will focus on repairing and stabilizing public roads, sewer systems, and other critical infrastructure. The city is collaborating with neighborhood associations to streamline the grant application process and ensure timely support for the hardest-hit communities.

The slowdown of the landslide due to the deep dewatering program is a testament to the efficacy of geotechnical engineering and collaborative efforts. While the problem persists, proactive measures are helping residents adapt and prevent further damage.

Check out the following video depicting the ongoing land movement crisis is forcing more homes in Rancho Palos Verdes to have their power cut off.