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In January of 2023, amid epic storms that saturated the cliffs along Highway 1 in Big Sur, a massive landslide dumped tons of dirt and rocks onto the highway, rendering it impassable. Since then, there have been several more slides, including in late March of this year when a chunk of Highway 1 suddenly collapsed into the sea, stranding both coastal residents and tourists on this stretch of remote coastline south of Monterey. Although, repairs have partially re-opened the highway so that residents can get in and out, anyone dreaming of driving this iconic stretch of the California coastline all the way from Monterey to Morro Bay will have to wait until the last of the slides have been cleared, currently estimated for this fall.
It’s not just the Big Sur coast that’s crumbling. In Pacifica, a considerable chunk of the coastal bluffs fell into the ocean in 2016, resulting in the evacuation and condemnation of a block of apartments that were left teetering on the edge of the cliff. In Half Moon Bay, Mirada Road, already right on the edge of the bluff, was turned into a one-way road after winter storm damage in March 2024. In Southern California, a 2023 landslide pulled eight homes into a canyon, leaving others uninhabitable due to damaged sewer lines.
Pretending that our cliffs and bluffs won’t keep eroding into the ocean is pointless. The question is, what will we do about it?
Reinforcing cliffs can cause even greater damage
Historically, the most frequent response to crumbling cliffs has been to “armor” the cliff face – by lining the base of the cliff with huge boulders (“riprap”) or by constructing concrete flood walls. The problem is that these structures actually accelerate the rate of shoreline erosion, because when waves break on hard surfaces like rock or concrete, the wave energy is reflected back with greater force. (Similarly, if you throw a ball against a brick wall, it will bounce back at you faster and harder than if you throw it against a mattress.) This affects beaches and bluffs – the stronger waves carry away more beach sand, resulting in gradually disappearing beaches.
If we continue relying on coastal armoring, we will ultimately lose our beaches. On the other hand, if we allow coastal bluff erosion to proceed naturally, we will replenish our beaches, as is happening in Southern California, where a slow-motion landslide is actually creating a new beach.
It’s time to start moving inland
We can start planning for the erosion that will eventually happen by thinking about how we can re-route public infrastructure, such as roads and trails, further inland. There’s already a well-known precedent for doing this – the Tom Lantos Tunnel on Highway 1 south of Pacifica, which replaced a stretch of highway known as “Devil’s Slide” that over the decades was periodically subject to landslides that forced the closure of Highway 1 for months at a time. Although Caltrans originally designed an environmentally devastating freeway bypass cutting through a state park that would have required four miles of continuous deep cuts and fills along the steep slopes of Montara Mountain, eventually, voters overwhelmingly approved a ballot measure that mandated that Caltrans build a tunnel.
Now, Highway 1 runs safely through the 4,000-foot-long tunnel rather than dangerously along the edge of the cliffs, and the former roadway has been turned into the Devil’s Slide Trail for pedestrians and bicyclists to enjoy.
With smart planning and public investment, we can stay ahead of climate change and protect our communities. We can choose to pretend that in the fight against the ocean, we can be the victors, or we can stop sticking our heads in the sand before that sand gets washed out to sea.
