Posted on September 2, 2026
By Kenny Choi
A beach replenishment project in Half Moon Bay is bringing sand, beachgoers and changing surf conditions back to a stretch of coastline that has been battered by decades of erosion.
But a newly published study highlights how breakwaters built more than half a century ago to protect Pillar Point Harbor have also altered wave patterns and contributed to erosion farther down the coast, threatening roads, homes and utilities.
For longtime Half Moon Bay resident Brian Overfelt, the replenished beach is a welcome sight.
“It’s a free rollercoaster for these kids. We’re so stoked,” Overfelt said while watching surfers including his daughter take advantage of the waves.
Overfelt said he began petitioning local officials more than 30 years ago to address severe erosion along the coast near Highway 1. Over the years, portions of the shoreline have disappeared, along with infrastructure and a stretch of the former Mirada Road that once ran alongside it.
“There used to be a road on this side that went from here all the way to the parking lot there,” Overfelt said. “There was a road that’s now gone.”
Last year, the San Mateo County Harbor District dredged accumulated sand from nearby Pillar Point Harbor and used it to replenish the eroding shoreline.
UC Santa Cruz earth sciences professor Gary Griggs has studied the impact of the breakwaters surrounding the harbor. The U.S. Army Corps of Engineers constructed the large barriers during the mid-20th century to protect the harbor from waves.
Griggs said the structures changed how wave energy reaches the shoreline.
“When they built those two breakwaters, all the wave energy that was dissipated in that nice hook-shaped bay went to the end of the breakwater,” Griggs said.
His newly published research examines how that shift in wave energy accelerated erosion and bluff retreat south of the harbor.
“It started eroding the low bluffs, threatening Highway 1,” Griggs said. “It destroyed a local county road, Mirada Road, it destroyed the wastewater line, and now is beginning to work its way down.”
The concerns come as scientists anticipate potentially powerful winter storms along the California coast. Strong El Niño conditions can intensify wave activity and coastal erosion, putting already vulnerable areas at greater risk.
Homeowners south of the harbor are currently protected in some areas by riprap, large rocks placed along the shoreline to reduce erosion. Some residents say a more permanent solution, including seawalls, is needed.
“The homeowners and businesses along this road here are going to lose access to their properties, which will really be detrimental to the housing down here, to the neighbors and everyone who lives in this area,” said Paul McGregor.
Finding a permanent solution is complicated by the number of local, state and federal agencies involved in managing the coastline.
Griggs said the underlying problem is unlikely to disappear without significant changes to the harbor’s coastal infrastructure.
“Without a complete redesign, it’s just gonna continue,” Griggs said. “Because waves, as we know, are getting bigger and more energetic, sea levels are rising, so any coastal problem we have today is only gonna get worse incrementally in the future.”
For Overfelt, continued dredging and beach replenishment remain one practical way to reduce some of the effects of the breakwaters.
“We’ve lost so much land,” he said. “But the good thing is we can get it all back. Just gotta keep dredging.”
San Mateo County officials are closely monitoring the beach replenishment project.
Griggs said the newly placed sand will eventually erode and move away from the beach, although it is unclear how long the replenished shoreline will remain in place.
