"Projections show more winter rainfall, which means more flooding or slope failures,” says one expert.
Slope erosion and landslides pose a rocky risk for motorists along Southern California highways, and the Caltrans is using wire mesh to bolster freeway protections on the hilly Antelope Valley Freeway in Santa Clarita.
On Wednesday, July 17, Caltrans workers laid down a huge wire mesh blanket to cover and prevent rocks from rolling off the towering slope near State Route 14, known as the Antelope Valley Freeway, south of Golden Valley Road.
The mesh installation is part of a $16.1 million project to regrade, improve and protect slopes on the freeway. The crew is also placing sheets made of wood fibers that contain seeds and fertilizer along the top of the slope — to encourage plants to grow with deep roots that stabilize the earth.
Michael Comeaux, a public information officer at Caltrans, said slope protection is necessary in part because of the intense atmospheric rivers that pounded California in February, bringing historic amounts of rain. The rain seeped into the ground and loosened rocks creating a precarious situation along some stretches of State Route 14.
“This project is about protecting the slope, because water can have a very damaging effect on valuable transportation infrastructure,” Comeaux said. “We’ve had a series of storms that produced torrential rain that soaked many hills and slopes in Southern California. We began to see erosion, so we decided to take action to strengthen the slope.”
February 2024 was the fourth wettest February on record in Los Angeles. The city saw more than 500 mudslides caused by the tremendous rainfall, and Caltrans is gearing up for another wet winter later this year.
“We don’t want rocks tumbling down to where they would end up on the shoulder of the freeway or even in a lane,” Comeaux said. “Also, we don’t want the surface of the slope to begin to fall apart like that. We want the surface of the slope to be stable.”
According to Gary Griggs, a professor of earth and planetary sciences at the University of California, Santa Cruz, climate change has exacerbated slope erosion across California, heightening landslide risks.
“In the future, as you look at climate change, it’s not going to make any of this any better,” Griggs said. “We’re going to get longer, hotter, drier summers, which means drier brush and more fires, which could lead to instability in winter. And projections show more concentrated winter rainfall, which means more flooding or slope failures.”
Griggs said that when building highways, “there is both an engineering aspect and an economic aspect.”
When crews cut into the side of a hill or mountain to make room for a highway, it is generally cheaper to create a steeper slope than one with a gentler angle. Gentler slopes require more land, which has to be purchased and carved out.
But pricier, gentler slopes typically have a lower risk of landslides than slopes with steep angles.
“There’s always this balance,” Griggs said. “And Caltrans definitely has a tough job, maintaining the stability along these slopes.”
