Proactive Beach Management Measures Underway In Waikiki
Civil Beat- Honolulu. November 14, 2019
Sea-level rise and coastal storms require us to develop innovative erosion control plans based on proven science.
Reading time: 5 minutes.
As a nonprofit organization comprised of coastal engineers, scientists, planners, and community representatives, the Hawaii Shore and Beach Preservation Association would like to provide some clarification to the Nov. 4 Civil Beat Community Voice titled “There’s A Better Way To Replenish Waikiki’s Sand.”
First, it is critically important to distinguish Waikiki as an urban beach with a unique history of coastal development. Due in part to this unique history, being entirely man-made and thus inherently unstable, Waikiki Beach warrants proactive planning, erosion control intervention, and beach management actions that may not be viable or appropriate in other locations.
The use of a submerged shore-parallel structure (breakwater), as suggested in the opinion piece, would not only interfere with recreational activities in Waikiki, but may negatively impact the existing sediment transport pathways.
The opinion piece mentions that six to eight years ago the state dredged offshore to provide “hundreds of thousands of cubic yards of soil to restore the vanishing beach,” and that “The first Waikiki beach restoration project cost about $7 million and had a life of only some seven years.”
In 2012, the state Department of Land and Natural Resources in partnership with Kyo-ya Hotels recovered 25,000 cubic yards of marine carbonate sand (not soil) from immediately offshore of the coastline as a form of beach maintenance. The purpose of the project was to recycle beach quality sand back to the beach where it originated.
This project cost $2.7 million (not $7 million). This project is widely considered successful since it achieved the project goals of delivering offshore, beach compatible sand back to the beach at a cost-effective price.
Recent erosion and king tide events in Waikiki have highlighted the need to develop comprehensive and proactive management plans.
Nathan Eagle/Civil Beat
The author of the opinion piece writes, “In that process, the state irreversibly damaged the ecology of the ocean.”
In fact, the project marine monitoring report from the 2012 Waikiki beach nourishment project found no conclusive evidence of environmental damage or change in the nearshore reef ecosystem that could be attributed to project impacts.
The 2012 project did result in the placement of greater than expected fine marine silt content, which created “milky” ocean conditions. This naturally occurring marine silt was flushed out and continues to be flushed during high tides and high surf conditions; however, this material has not resulted in “irreversible damage to the ecology of the ocean.”
About Geotextile Tubes
The author writes, “The use of geotextile tubes has been proven in the Yucatan Peninsula facing the Gulf of Mexico. Within only two to three years, multiple locations had natural sand deposited … and last three times longer, to 21 years.”
Geotextile tubes can be effectively employed in certain environments. Use of geotextile tubes on the beach and in the water at Waikiki has been considered, but they do not meet the rigorous environmental, oceanographic, recreational, marine biological, essential fish habitat, endangered species, or water quality requirements for use as a beach stabilization structure at this location.
Typically, these geotubes are buried as the “core” of a reconstructed coastal dune and can have lifespans that exceed 20 years when completely buried. However, there is ample evidence in engineering literature that documents significantly reduced lifespans when the materials are exposed to the marine environment, wave action, and abrasion.
The author also writes, “Besides, anyone supporting the idea of cheaper construction is quickly brought down by those wanting construction to be as expensive as possible.”
It is critically important to distinguish Waikiki as an urban beach with a unique history of coastal development.
There appears to be no basis for this statement. In the case of the Kuhio sandbag groin, the project is a public-private partnership with 50% of the costs funded by the Waikiki Beach Special Improvement District Association providing private funds as a match and which has no ties to the contractor or the state procurement process.
And the author writes, “Approximately one mile of geotextile tube will be needed offshore at Waikiki. By a rule of thumb, which is more scientific than science can prove, these tubes are usually placed such that their top is at the lowest level of the low tide visible on the beach.”
Given the importance of Waikiki Beach in all permit and environmental review contexts, a one-mile long submerged breakwater in Waikiki is highly unlikely to make it through the environmental review and permitting processes, and there is no evidence that it would result in a more stable beach. Rather, impacts to surfers, locals, businesses, and visitors alike would be tremendous, including potential public safety concerns for a shore parallel, submerged breakwater, located in the wave impact zone of the beach face.
Recent erosion and king tide events in Waikiki have highlighted the need to develop comprehensive and proactive management plans for Waikiki Beach that can account for the dynamic nature and future changes in the shoreline.
The compounding impacts of sea-level rise, coastal erosion, sediment deficiencies and coastal storms require us to think creatively and develop innovative erosion control plans based on proven science. As such, alternatives are being conceptualized and will be evaluated from engineering, financial, permitting, recreational, cultural and aesthetic perspectives.
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About the Author
Dolan Eversole serves as the president of the Hawaii Shore and Beach Preservation Association, an organization of private sector, academic, and government professionals, students and local community members. Eversole is a coastal geologist and faculty of the University of Hawaii Sea Grant Program and serves as the Waikiki Beach management coordinator for the Waikiki Beach Special Improvement District Association.
