California Landslide Homes Trap Owners in Risk
How Hurricane Hilary’s Rains Accelerated the Portuguese Bend Landslide? Why did a single storm reignite a decades‑old landslide? Hilary rainfall poured unprecedented volumes onto the Portuguese Bend peninsula in summer 2023. Water infiltrated the deep Bentonite layer, turning the clay into a slick, lubricated plane. This Bentonite lubrication reduced shear strength, allowing the ancient mass to slip rapidly. Immediate Acceleration Movement rose to one foot per week after the storm. Peak rates reached four inches per week between September 18 and October 17 2024. Some sectors advanced four feet per month, far exceeding the pre‑storm average of 1.74 inches per week. Geological Mechanism Stormwater percolated into the bentonite, adding mass and fluid pressure. The combined effect of added weight and reduced friction triggered a cascade of sliding across the five‑mile landslide complex. Infrastructure Impact Roads such as Narcissa Drive were closed, and utilities were shut off for hundreds...