Driftwood destiny: Where all those beached logs come from and where they’re going

APTOS — All week long, the scene at local beaches has caused visitors to pause for a moment and stand in awe of what sits before them while their furry companions are sent into an insuppressible fit of joy.

That’s right, there’s still plenty of driftwood piled up on Santa Cruz County shores – parked there last week by heavy rainfall and a massive tidal swell.

The images aren’t so different from last January, when a powerful string of atmospheric river storms swept mountains of ocean debris and tree trunks the size of SUVs onto local shores that took officials weeks to clean up and disperse.

But as crews rung in the new year with another robust mop up effort to the dismay of countless local pups, some may wonder: where does it all come from and where does it end up?

Another pileup

Gabe McKenna, spokesperson for California State Parks which manages nine beaches across the county and several more subunit regions, said the cleanup effort in some of the hardest-hit, low-lying areas such as Seacliff, Rio Del Mar and New Brighton began Tuesday and will continue for at least a week.

Beaches in Capitola and Santa Cruz were also inundated with a mix of seaweed, tree branches and large timber during the heavy storms in late December.

According to McKenna, the pileup is likely explained by three factors: high tides coupled with pounding waves pushed water to places that hadn’t been touched since last winter, jostling debris beached in previous storms; additional sticks and rocks nestled in the sand were unearthed by that same rushing water; and rainfall created enough runoff that carried some debris from rivers and creaks into the ocean that was then brought back ashore.

“It is a natural process; it does happen every single winter,” said McKenna. “This time seems to be coupled with that last swell event … the inundation was greater at Seacliff so it got additional damage and additional debris.”

Workers are sifting through the material – separating the big and small – and early estimates are that 85% of it is organic including pebbles, rocks and driftwood, according to McKenna. He added that nearly all of the organic material on state beaches will be redistributed back onto the beach, while some of the larger logs will be removed and sent through a wood chipper and then used as ground cover in other park regions. The inorganic material such as asphalt, concrete or pressure-treated wood will be hauled to the landfill.

As of Thursday, McKenna had no estimate for how much the cleanup effort from this latest storm will cost.

McKenna said the day-use and campground area that endured extensive damage in early January of last year was shuttered Tuesday after some of the repair work was further eroded.

“Taking a little bit of a step backwards here,” he lamented.

McKenna said Thursday that pedestrian and vehicle access will be fully restored to lower Seacliff and the Rio Del Mar Platform parking lot by Saturday, but he urged pedestrians to “heed signs and barriers and stay out of damaged areas.”

Meanwhile, for the beach areas that are open, State Parks will permit the public to remove as much as 50 pounds of driftwood from the beach in a 24-hour window, but tools such as chainsaws are prohibited, McKenna said.

Context and ecology

As McKenna hinted, distinguished professor of earth and planetary sciences at UC Santa Cruz Gary Griggs confirmed that Santa Cruz County is no stranger to powerful storms and the surge of debris they churn up.

Griggs explained that wood, leftover from the logging industry or dropped into local streams through wind activity or erosion, has historically been carried to the ocean courtesy of the San Lorenzo River as well as Soquel and Aptos creeks during major storm events. After fanning out into the bay, the powerful tide then sweeps them onto local beaches.

According to Griggs, debris flows piled up at local bridges and blanketed the shoreline after major winter storms in 1955, 1982, 2013, 2016-17 and 2023, to name just a few.

“Some of the stuff that probably gets remobilized was on the back of the beach from an earlier year,” said Griggs. “To a small degree, some of the debris comes off the bluffs.”

One local official with a close eye on the county’s rivers and streams is Erin McCarthy, water resources planner with the Santa Cruz County Health Services Agency. McCarthy manages the county’s stream wood program, which enforces a policy that large wood should be left in place when it enters local streams and rivers unless it poses and imminent threat to property, infrastructure, safety or habitat.

McCarthy said last year was a banner year when it came to reports of stream wood issues, with more than a 100 total calls when somewhere between seven and 20 would be considered normal.

“I was expecting to get calls during the last couple of weeks when we were having higher flows and I didn’t,” said McCarthy. “I think a lot of the wood that was loose in the watershed that was ready to be mobilized and enter our waterways, I think a lot of that already happened last year. That’s just my guess.”

McCarthy took a moment to highlight that stable stream wood, or large woody material, in the county’s rivers and streams often helps provide critical habitat for wildlife in the area, supports channels and banks and promotes groundwater recharge.

Steelhead and coho salmon in the county – both protected by the Endangered Species Act – rely on the pools formed by stream wood as a safe haven during treacherous high flow periods and a place to lay their eggs.

“It creates habitat complexity in our watersheds,” said McCarthy, adding that it’s “always a balance” when it comes to maintaining its important role for local wildlife while avoiding pitfalls such as major blockages or flooding.

Climate projections

But for the logs and sticks that have taken the tumultuous journey downstream and settled on the beach, Griggs said the ecological benefits they provide are likely a wash and the ultimate fate of the water-logged wood is likely not too consequential.

“My overall sense is: While there’s some modest ecological benefit, I don’t think that’s a make- or break-it situation for how we deal with it,” he said.

And while crews will continue the clean up effort until the piles have dissipated, the ever-increasing threat of climate change is likely to bring them back sooner than later. Griggs said current evidence and climate models point to longer, hotter, drier summers followed by more concentrated rainfall in the winter months. This equation, he added, is likely to produce more slope instability and higher stream flows.

“These floods are going to get more common and probably bring more debris to the shoreline,” said Griggs. “That’s what climate change projections would tell us.”