NEWPORT BEACH, Calif.—Ronan Collins is used to navigating giant waves and unpredictable currents when he paddles his surfboard out near the inlet that bisects this ultrawealthy beach town. He’s still getting to know the boulders, wooden pilings and shards of rusty metal.

Southern California’s most dangerous surf spot, the Wedge, has become even sketchier in recent months. Nonstop swells combined with a “super” El Niño phenomenon have washed away truckloads of sand from Newport Beach and other parts of the California coast, exposing hazards buried a century ago. They’ve also delivered some of the best waves anyone here can remember.

“It’s been great,” Collins, 21, said as he waxed his board atop a six-foot-high sand cliff that’s edging ever closer to $20 million oceanfront homes. He tries not to think about the possibility of getting skewered on ancient rebar. “Good thoughts and good vibes,” he said.

The Wedge was created in the 1930s, when the Army Corps of Engineers extended a rock jetty some 2,000 feet out from the beach to protect the entrance to Newport Harbor. Because it protrudes at a slight angle, swells approaching from the south or southwest bounce off the jetty and mutate into triangular peaks—hence the spot’s name. Waves can double or triple in height and form cavernous barrels before detonating in shallow water just a few yards from shore, making the Wedge a tantalizing spot for adrenaline seekers who don’t mind being slammed onto the sand—often in front of hundreds of onlookers.

“This wave is notorious for broken necks—it’s so shallow and there’s so much power,” said 39-year-old Sean “Poopies” McInerney, a “Jackass Forever” cast member who drove an hour from Oceanside, Calif., to surf swells generated by Hurricane Marie on a recent Saturday. “It’s just an amazing wave.”

Signs warn of dangerous conditions, and lifeguards often talk beachgoers out of entering the water if they appear inexperienced.

Popular with bodysurfers and boogie boarders since the 1960s—surfboards back then were too long to negotiate its steep drops—the Wedge has injured more wave-riders than any break in the world outside of Hawaii, according to the Encyclopedia of Surfing. The publication estimates eight people have died there, dozens have been paralyzed and thousands have landed in the hospital with broken bones and dislocated joints. And that was before the surf zone became riddled with rocks, logs, rods, pipes and wires.

The surf zone has become riddled with rocks, logs, rods, pipes and wires as the erosion exposes remnants of the city’s unsuccessful attempts to build jetties in the early 1900s, before the Army Corps of Engineers took over, said local historian William Lobdell. The jagged wood pilings are likely from railroad trestles installed to carry boulders out to the existing jetty. “It’s like an archaeological dig,” he said.

“All that stuff is getting turned up, and it happens to be right where the wave ends, which is really dangerous for us,” said Noah Gerard, 21. Moments earlier, he’d gushed to a buddy that he was “so stoked” to paddle out. “It’s been the best summer I’ve ever seen, for sure.”

Self-declared “Wedgelord” Matt VanderMeer, 53, said recent months have surpassed even the legendary summer of 1982, also an El Niño year. “I got it every day for almost two weeks,” VanderMeer said. The water is so warm he doesn’t know where his wetsuit is. “Usually you get one or two days a month, at best.”

El Niño can create a surfing paradise in Southern California. It elevates sea-surface temperatures across the eastern Pacific, fueling hurricanes that send big swells to south-facing beaches. But the phenomenon also creates wind patterns that cause local sea levels to temporarily rise by six to 12 inches, said Brett Sanders, a University of California at Irvine professor who studies sand movement. Those conditions—and unusually consistent groundswells from storms off New Zealand—are scouring sand from many beaches. Recent weeks have seen a sea wall damaged in Long Beach, staircases destroyed in San Diego County and dozens of oceanfront mansions tagged as unsafe.

“It’s just unprecedented,” said Kevin “Mel” Thoman, 69, of the erosion and the waves. The longtime Wedge bodysurfer figures the beach has lost around two-thirds of its width this year, leaving just 50 yards or so between the water and the first row of homes. Locals have lost track of an exposed rock they dubbed the Matterhorn, he said. “Now there’s just a bunch of them.”

In early September, as surfers and bodyboarders rode 20-foot wave faces, lifeguards took an electric reciprocating saw to the exposed pilings. Beachcombers scooped up artifacts including beer cans from the early 20th century. “There’s just weird stuff sticking out,” said bodysurfer Rick Piani, 58. “I’m kinda interested in getting a mask and snorkel when this calms down and checking it out.”

Wedge regulars constantly joke about getting shish-kabobed on submerged hazards while vying for waves. Locals say the worst injury they’ve seen so far this year was a bloody face, likely from a rock. Collins said he’s kicked a few rocks after riding waves but “nothing too crazy yet.”

Politically, the erosion isn’t a wedge issue: Newport Beach City Council voted unanimously on Aug. 25 to study the problem and consider what, if anything, to do about it. The motion was proposed by council member Erik Weigand, who bodysurfs, though not at the Wedge. “I’m getting too old to get face-planted into the sand,” he said.