On a recent overcast October afternoon, yet another section of West Cliff Drive, the premier seafront street in Santa Cruz, California, was roped off as workers toiled to prevent it from crumbling into the Pacific Ocean.

The erosion gnawing away at this prized road, and the famed surfing beaches it overlooks, is emblematic of the relentless threat that climate change poses to California’s coastline. As the sea level rises and storms of growing strength smash into the coast, the golden sands and beach properties that have come to define the state are at risk.

“I think with every coastal road in California, you’re going have to think about relocating it,” said Gary Griggs, an earth sciences professor at the University of California, Santa Cruz.

West Cliff Drive, which sits on an elevated bluff, hugs the coast near Santa Cruz’s 111-year-old boardwalk en route to a nature reserve thick with eucalyptus. The street’s beach houses and towering villas are regularly valued beyond $2m, with some vacant plots of land fetching $1m.

“Coastal property values are way inflated, factoring in all the risk involved,” Griggs said. “West Cliff Drive is the place to be now; lots of people who made money in Silicon Valley have moved there.”

Santa Cruz sits on the northern lip of Monterey Bay, which is losing several feet of beach a year. Sections of the cliffs beneath West Cliff Drive are abutted by piles of rocks, known as riprap, placed as a last-ditch attempt to stem erosion.

There is only one house on the ocean side of the road, and its owners moved in recently. “They didn’t have any idea what they were getting into,” said Griggs, who is doing consulting work for the owners amid a tussle with authorities over riprap earlier put in place without permission. “The seawater keeps rising. In the long run, the main beach in Santa Cruz will certainly be lost, if nothing is done.”

Santa Cruz sits on the northern lip of Monterey Bay, which is losing several feet of beach a year. Photograph: Marcio José Sánchez/AP

Similar challenges are sprouting up along the California coast, particularly in the south of the state. Up to two-thirds of southern California’s beaches will completely erode by the end of this century if there aren’t “large-scale human interventions”, according to a major report released by the state government in August. Around $48bn worth of property will be at risk should the swelling sea level increase beyond 4ft.

“If we continue the path we are on there will be significant loss of beaches,” said Madeline Cavalieri, a program manager at the California Coastal Commission. The response to morphing coastlines will have to involve a combination of “protection, accommodation and retreat”, she added.

This scenario is particularly painful for a place like Santa Cruz, which draws its cultural and economic strength from its beaches and pounding waves.

According to local lore, three visiting Hawaiian princes introduced surfing to the city in 1885, when they rode the waves in longboards milled from local redwood. Surfers from around the world now descend upon Santa Cruz to spots such as Steamer Lane, where a rip hurtles into a sandstone bluff that has been in retreat since the last ice age and is now guarded by an array of rocks. A former lighthouse, now a surfing museum, overlooks surfers scrambling over the rocks and into the foaming water.

“If you ask a surfer, it’s very apparent that climate change is real and is happening right before our eyes,” said Nick Muchas, who has lived and surfed in Santa Cruz for the past 15 years. Muchas frets about surfing spots that will suffer as the coasts recede, leading to overcrowding at the better areas, as well as the impacts on land.

“West Cliff Drive is our cherished road, it’s our treasure chest, and every winter we can see the whole cliff is becoming more unstable,” he said. “When the surf and spray comes over it, I’d say it’s treacherous.”

Erosion has shaped California’s coast since long before mass industrialization started pumping planet-warming gases into the atmosphere. A rock arch near the lighthouse collapsed in the late 19th century, with just a stump remaining now. A separate rock formation, known locally as “the old shoe”, is now more like the bottom of a heel.

But climate change is accelerating this process. According to a city climate plan, more than 70 Santa Cruz buildings are expected to be at risk from flooding within 12 years with 4in of sea level rise. By 2100, this grows to 390 residential and 65 commercial properties, along with seven miles of roads. This would come with “high rates of beach and coastal bluff retreat”, the document states.

“It’s really hard to say right now what that means, but we do know that tourism is a major driver of our economy here locally,” said Tiffany Wise-West, the sustainability and climate action manager for the city of Santa Cruz. “What if [residents] do have to move at some point? We already have an affordable housing crisis here in Santa Cruz.”

Along about a tenth of the California coast, the response to this threat has been to erect seawalls or dump protective rocks. While this may buy time for expensive low-lying infrastructure – waste water treatment plants, power stations, the airports at San Francisco and San Jose – the barriers can exacerbate the loss of beaches.

As the sea level rises, beaches would naturally migrate inland with the retreating coastline. But fixed points such as seawalls prevent this shift, trapping and in effect drowning the sand as the sea rises and storms take their toll.

Surfers from around the world descend upon Santa Cruz to spots such as Steamer Lane. Photograph: Eric Risberg/AP

Roads, sidewalks and buildings also provide a barrier, which presents a conundrum for cities such as Santa Cruz that want to avoid the opposing financial cataclysms of losing their beaches or having to relocate buildings and people en masse to safer ground inland.

The hard choices won’t be deferred for much longer. California’s coastal commission has been pushing Santa Cruz to come up with an erosion plan for West Cliff Drive and the city is turning to residents for feedback.

More defences may be erected; some areas may have to be abandoned. The state is keen on “green” solutions – seeding wetlands or other vegetation to slow the tides – but that is tough to do in Santa Cruz, with its steep cliffs and hefty waves.

The retreating coastline isn’t the only climate challenge Santa Cruz, like many coastal locations, is facing. Heatwaves threaten the sick and elderly, while lengthening wildfire seasons risk choking the city with smoke. The city, already unaffordable for many residents, could see a future influx of people seeking to escape from baking temperatures inland.

“I would say we are on the leading edge in terms of understanding our risks and being proactive and addressing them,” Wise-West said. “It’s a pretty daunting topic, though.”