HDOT LAUNCHES HYBRID REEF PROJECT TO PROTECT HAWAI‘I’S COASTAL HIGHWAYS
FOR IMMEDIATE RELEASE
Sept. 14, 2026
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HONOLULU – To help protect Hawaiʻi’s vulnerable coastal highways from erosion and rising seas, the Hawaiʻi Department of Transportation (HDOT) is launching the Kalaeloa Hybrid Reef Project. Developed by Defense Advanced Research Projects Agency (DARPA) via its Reefense Program and the University of Hawaiʻi (UH) alongside academic, community and industry partners the project is an example of nature-based coastal engineering — an emerging approach that combines engineered infrastructure with natural ecosystems to protect vulnerable coastlines. The hybrid reef system integrates engineered reef structures with living coral to reduce wave energy, strengthen shorelines and improve coastal resilience. The deployment marks the first large-scale ocean demonstration of the technology, following four years of research and development.
“Success at Kalaeloa could provide a model for protecting vulnerable coastlines throughout Hawaiʻi and beyond,” said HDOT Director Edwin Sniffen. “We’re not just defending our shorelines, we’re building a resilient, self-sustaining ecosystem. By partnering with DARPA and UH, we are helping position Hawaiʻi as a global leader in nature-based coastal engineering.”
Funded by DARPA, the hybrid reef structures were researched, developed and deployed in collaboration with UH, Makai Engineering, Kuleana Coral Restoration and other partners. Following deployment, ownership of the structures will transfer to HDOT.
The first year of monitoring and maintenance of the project is funded by the State’s Green Fee program, which supports conservation and environmental initiatives that protect and restore Hawaiʻi’s natural resources. The investment supports the first large-scale demonstration of a nature-based alternative to seawalls that aims to reduce coastal erosion, wave damage and storm surge while enhancing marine habitat.
“The Green Fee is about investing in innovative solutions that protect Hawaiʻi’s people, natural resources and economy for generations to come,” said Governor Josh Green. “The Kalaeloa Hybrid Reef Project is exactly the kind of forward-thinking partnership we envisioned, bringing together science, innovation and environmental stewardship to strengthen our coastlines while preserving the natural resources that make Hawaiʻi unique.”
“Through Reefense, DARPA is reimagining coastal defense by combining cutting-edge materials science with adaptive biology to protect vital infrastructure and personnel from wave damage, erosion, and severe storms,” said Dr. Catherine Campbell, DARPA deputy director Biological Technologies Office. “Our collaboration with the University of Hawaiʻi, state leadership, and local partners at Kalaeloa translates high-risk, high-reward defense research into a scalable, real-world solution that safeguards critical transportation corridors while strengthening the surrounding marine ecosystem.”
A ‘living’ breakwater
The Kalaeloa Hybrid Reef is a UH-developed living breakwater designed to reduce wave energy while improving the natural habitat. The system consists of 60 engineered, porous concrete reef mimicking structures manufactured in Hawaiʻi that dissipate wave energy while allowing water to flow through the reef. Coral settlement modules attached to the structures will support the recruitment and growth of native corals while specially developed biomaterials will repel competing algae and accelerate coral growth. These and other technologies being tested will allow the reef to develop into a healthy, self-sustaining ecosystem over time.
The project site is a degraded area with a hard rock bottom south of Kalaeloa Harbor. Although there is minimal live coral in the project site, work at Kalaeloa will begin with the careful removal of any coral fragments present and preservation of that coral on growing tables near the project area. Next will be installation of the reef structures, attachment of live coral fragments to the structures, and continued scientific monitoring to evaluate their performance.
The deployment is the result of four years of research and development by the Rapid Resilient Reefs for Coastal Defense (R3D) consortium. Led by the UH Applied Research Laboratory and the School of Ocean and Earth Science and Technology, the initiative brings together researchers from five UH laboratories, partner universities and local organizations, including Makai Ocean Engineering and Kuleana Coral Restoration.
“Kalaeloa will become a living laboratory where we can evaluate how nature-based coastal engineering performs under real-world ocean conditions,” said Ben Jones, R3D principal investigator and director of ocean science and technology at the UH Applied Research Laboratory. “Our goal is to demonstrate that living breakwaters can provide an effective alternative to traditional shoreline hardening and to collect the scientific data needed to guide future coastal resilience projects in Hawaiʻi and around the world.”
Community helps guide long-term stewardship
Once deployed, the Kalaeloa Hybrid Reef will serve as a living laboratory for the emerging field of nature-based coastal engineering, which integrates engineered infrastructure with natural ecosystems. Long-term monitoring will be guided by the newly established Kalaeloa Hybrid Reef Monitoring Hui, a partnership of researchers, agency representatives, community organizations and cultural practitioners that will assess the reef's environmental, engineering and cultural impacts. This local partnership includes community stakeholders such as the Makakilo-Kapolei-Honokai Hale Neighborhood Board, and the mālama kai organization Hoʻola Hāniʻo.
“This project would not be possible without the partnership of the local community,” said Sniffen. “We are grateful to the organizations and cultural practitioners who have helped shape this effort and will continue to guide its long-term stewardship. Their knowledge and commitment are essential to the project's success.”
The findings will be shared with regulators, engineers and coastal managers to help inform future shoreline protection projects in Hawaiʻi and elsewhere. If successful, the Kalaeloa Hybrid Reef could provide a scalable, nature-based approach to protecting vulnerable coastlines while advancing the growing field of nature-based coastal engineering.
Building a living reef
The Kalaeloa Hybrid Reef is an example of nature-based coastal engineering, integrating coastal engineering, marine biology and innovative deployment techniques to create a living coastal protection system. UH has partnered with University of California San Diego (UCSD) and the Scripps Institution of Oceanography (SIO), Florida Atlantic University and Ohio State University on its development.
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Engineered reef structures: The foundation relies on specifically designed concrete reef structures designed by Ocean and Resources Engineering at UH cast by Kapolei-based firms Jensen Infrastructure and GPRM Prestress, located less than two miles from the deployment site. In large-scale wave-flume tests, these model breakwaters successfully reduced incoming wave energy by more than 80% while remaining stable during extreme conditions.
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3D-printed coral habitat: To kickstart the living reef, the Hawaiʻi Institute of Marine Biology (HIMB) developed 3D-printed ceramic modules featuring small, spiral-shaped shelters called “helix recesses.” Experiments in Kāneʻohe Bay showed that these crevices yielded an 80-fold increase in baby coral settlement and up to a 50-fold increase in survival rates compared to flat surfaces.
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Biomaterials: Researchers at the UCSD have developed novel materials that reduce algae competition while allowing for coral to grow on the structures. Other materials provision the juvenile coral with nutrients needed in their early life stages.
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Acoustic Enrichment: Researchers at UCSD-SIO have recorded sounds of healthy reefs that will be broadcast near the living breakwater to encourage algae-grazing fish to the site.
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Low-impact deployment: To minimize disruption to the marine environment during deployment, Makai Ocean Engineering has developed a shallow-water catamaran, eliminating the need for heavy crane barges. Additionally, the structures will be anchored using a novel rotary micropiling system, which significantly reduces the anchoring footprint and sound pollution compared with traditional pile drivers.
Photos of the blessing event, reef-mimicking structures and ReefCat Deployment System that will transport the structures offshore and carefully lower them onto the seabed for installation (photo credit HDOT):
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Media contact:
HDOT Public Affairs Office
Phone: 808-587-2160
Email: dotpao@hawaii.gov
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