DATE: April 22, 2026
TO: Honorable Mayor and City Councilmembers
FROM: City Manager's Office
TITLE: PHYSICAL MODELING OF THE RE:BEACH OCEANSIDE PROJECT AT THE O.H. HINSDALE WAVE RESEARCH LABORATORY
RECOMMENDATION
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Staff recommends that the City Council receive a presentation and report on the physical modeling of the RE:BEACH Oceanside Pilot Project conducted at the O.H. Hinsdale Wave Research Laboratory.
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BACKGROUND AND ANALYSIS
Many factors contribute to the current state of Oceanside beaches; however, the primary driver of long-term beach erosion is the lack of sustained natural sediment supply. Coastal development, armoring, and flood control infrastructure have significantly reduced sediment delivery from local watersheds, while alongshore transport of sediment is disrupted by the Oceanside Harbor Breakwater. This structure supports the Camp Pendleton Boat Basin and City’s Small Craft Harbor (Harbor Complex), but also impounds sand that would otherwise be transported from the Santa Margarita River to Oceanside’s coastline. Additional coastal management challenges contributing to the eroded state of the beaches include the fact that Oceanside does not have any hard structures, either natural (e.g., a natural reef or headland) or unnatural (e.g., groin) south of the Oceanside Pier that would help retain sediment. Without varied topography, Oceanside sustains a straight coastline, exposed to all swell angles and seasons, which results in erodible beach conditions and sand that leaves the shoreline more rapidly than other areas in North County San Diego.
In 2020, the City completed a beach sand replenishment Feasibility Study (Phase 1) that evaluated coastal management deficiencies and identified a suite of solutions to address long-term erosion. The study concluded that a reliable source of compatible sand is necessary to support ongoing nourishment and that retention structures are critical to improving the longevity of placed sand.
In 2022, the City initiated Phase 2 of the project through a Request for Proposals for coastal engineering services, ultimately selecting GHD Inc. to lead design, engineering, environmental review, and stakeholder engagement. As part of this effort, the City conducted the RE:BEACH Oceanside Coastal Resilience Design Competition in 2023, culminating in City Council selection of the “Living Speed Bumps” concept in January 2024. The project, now commonly referred to as the RE:BEACH Oceanside Pilot Project, includes three primary elements: an artificial offshore reef, two artificial headlands, and beach and nearshore sand nourishment. In November 2024, the City Council approved Segment 1 as the pilot project location.
As the project advanced, detailed numerical modeling was performed to evaluate a range of reef design alternatives under multiple wave and water level scenarios. Given the innovative and site-specific nature of the RE:BEACH Project, physical modeling was also undertaken to further evaluate project performance under controlled but realistic oceanographic conditions and to refine design elements prior to final engineering and permitting.
Earlier this year, the City partnered with the O.H. Hinsdale Wave Research Laboratory at Oregon State University to conduct large-scale physical modeling in a three-dimensional directional wave basin. A scaled representation (1:35 scale) of Oceanside’s shoreline, nearshore bathymetry, and proposed project features was constructed using accepted engineering scaling laws. This approach allowed the project team to evaluate wave transmission, current formation, and physical processes of Oceanside’s coastline at scale.
The physical model incorporated surveyed seafloor bathymetry off Oceanside’s coastline, the proposed artificial reef, two headlands, and representative beach sand proxies. Testing scenarios simulated a range of conditions including typical seasonal waves, high-energy winter storms, long-period south swells, extreme events, and varying tidal conditions. Waves were generated from multiple directions and water levels to reflect Oceanside’s bi-directional swell climate.
The physical modeling effort produced several important findings that support the viability of the RE:BEACH Project:
• The artificial reef reduced wave energy that directly reached the shoreline, particularly during higher-energy conditions, thereby decreasing erosion potential.
• Multiple reef geometries were tested, allowing refinement of the design. Preliminary results indicate that parameters such as crest height, width, and configuration influence wave energy transmission and alongshore effects.
• The combined system of offshore and shoreline features altered nearshore circulation patterns in a manner that encourages retention of nourished sand, forming a more stable beach system compared to existing conditions where sand rapidly disperses and currents drive sediment offshore and alongshore.
• Under a range of water levels, the project continued to provide measurable benefits, although periodic re-nourishment will be necessary as part of a long-term adaptive management strategy.
• Physical modeling informed adjustments to the configuration, elevation, and orientation of project elements to minimize localized scour, avoid wave focusing, and improve overall system performance.
• While optimizing the artificial reef for both coastal resilience and consistent, high-quality surf amenity is inherently complex and condition-dependent, the artificial reef has the potential to enhance surfability in and adjacent to the reef by modifying wave breaking patterns and improving sand bar development.
• Surf performance is inherently variable and dependent on oceanographic conditions; however, modeling results indicate that reef geometry can promote more favorable wave peeling and ride length under certain swell and tidal conditions, suggesting that recreational enhancement could be a strong co-benefit of the project.
The physical modeling represents a critical step in advancing the RE:BEACH Oceanside Project from conceptual design toward implementation. As analysis and results are compiled, they will be used in combination with numerical modeling to evaluate the overall approach of pairing sand nourishment with retention features. Together, these efforts can provide increased confidence that the system can function as intended across a range of wave and environmental conditions. The findings of this modeling exercise are being incorporated into final engineering design, environmental documentation, and future construction planning.
FISCAL IMPACT
Does not apply.
COMMISSION OR COMMITTEE REPORT
Does not apply.
CITY ATTORNEY’S ANALYSIS
Does not apply.
Prepared by: Jayme Timberlake, Coastal Zone Administrator
Submitted by: Jonathan Borrego, City Manager