City presents ReBeach physical modeling showing reef can retain sand; experts, advocates urge permitting and monitoring

Oceanside officials and consultants told the City Council on April 22 that laboratory testing of the ReBeach Oceanside pilot project produced encouraging results showing the proposed artificial reef can retain sand in the lee of the structure and reshape nearshore currents.

“ReBeach is the city’s main effort to restore beaches and build resilience using a novel artificial reef system,” said Jamie Timberlake, the city’s coastal zone administrator, describing modeling work carried out at the Hinsdale Wave Research Basin at Oregon State University. Timberlake said the Coastal Commission supplied a substantial grant to support the modeling and monitoring.

Daniel Dedina, the lead coastal engineer with GHD, said the team ran more than 1,000 numerical simulations and then nine weeks of physical experiments to test wave transmission, stable rock sizes, sediment transport, value‑engineering options and surfability. “We saw the material move in behind the reef — that pattern is what we wanted to see,” Dedina said, describing movable‑bed tests that used crushed walnut shell as a scaled surrogate for sand.

Dedina and GHD staff reported that stable rock sizes under extreme (100‑year) storm testing would be large — roughly 6‑ to 16‑ton boulders on the reef bridge crest and progressively smaller sizes on other reef sections — and that raising the reef crest yields diminishing returns in wave attenuation beyond certain elevations.

Save Oceanside Sand, a local advocacy group that has followed the project closely, praised the modeling. “The modeling of ReBeach pilot project provides that proof, and the results are both encouraging and important,” Bob Ashton, CEO of Save Oceanside Sand, told the council.

Not all speakers were unreservedly supportive. Carolyn Kramer of Citizens for the Preservation of Arts and Beaches said she heard earlier presentations that emphasized dissipation and said she worried the reef could act like a seawall in some conditions. Timberlake and Dedina responded that the design intentionally redistributes wave energy onto the reef and that the project team is developing an adaptive management plan with post‑implementation monitoring and mitigation to respond if performance differs from expectations.

City staff and consultants also described project scale and next steps. Timberlake said the pilot work will be combined with an adaptive management plan and that design reports will be available in the coming months; Dedina said value‑engineering work aims to reduce rock volumes while retaining performance. Timberlake noted the city has an approved local sand borrow site just offshore in city tidelands and that the Coastal Commission remains a partner on permitting.

Public commenters from the surf and shoreline communities emphasized the project’s potential to return sand and improve surf breaks; others pressed for clarity on environmental impacts, adjacent beaches and legal authority. City staff said the pilot includes monitoring commitments and an adaptive plan and that permitting and environmental review remain as the project advances.

The council received the presentation and filed the report; staff said a fuller written report would be posted and that further design and permitting steps would follow.

What’s next: staff and consultants will finish analysis and publish the physical‑model report in coming months, continue adaptive‑management planning, and coordinate permits with the Coastal Commission and other agencies before any construction decision.