By BRIAN PERRY
The county Department of Planning is soliciting bids from consultants to study the feasibility of using sand nourishment as a way to reduce shoreline erosion in Kahana, where seawalls stop the ocean from washing condominiums out to sea.
Known as “shoreline armoring,” seawalls or revetments protect threatened properties from the advancing ocean, but the structures also trigger a domino effect of worsening erosion at neighboring properties.
Maui County has budgeted $160,000 this fiscal year for a Kahana erosion mitigation study, although the spending authorization is tied to a matching funds requirement, which could come from area condos, vacation rentals and time-share owners for a study to explore offshore sand mining and possible structures to mitigate the coastline’s erosion.
To come up with the matching funding, Maui County is working with the nonprofit Tri-Isle Resource Conservation and Development Council to launch a Web page for secure donations to create a way for individuals and condo associations to contribute toward the project, said James Buika, lead coastal resources and shoreline planner with the Planning Department.
“We have received assurances of participation and support from most, though not all, of the nine condominiums fronting the bay, including the Royal Kahana Resort, which has already contracted for preliminary studies,” he said.
The Royal Kahana has committed to spending $145,876, which would go toward data collection and planning for a small-scale beach nourishment project. Buika said that the Royal Kahana funding has been identified as eligible matching funds for the erosion mitigation study.
The Royal Kahana project would be a complementary part of the larger county project, Buika said. “To complete this smaller project, the same data and planning is required as the larger regional project, only smaller in scale. Much of this same data collection for the larger project will now not need to be completed because this data is available and can be used as a subset of the larger data collection and planning effort.”
The county’s invitation for bids was issued Wednesday. Submissions are due Nov. 27.
“Coastal erosion in Hawaii is a continuing and worsening problem, with 85 percent of Maui shorelines experiencing long-term erosion,” the request for proposals says. “Sea-level rise is a primary factor in the changing size and shape of Hawaii’s shorelines.”
University of Hawaii research shows that Maui is losing beaches to erosion faster than Oahu and Kauai because of locally higher rates of sea-level rise, the document says, adding that the situation is particularly dire at Kahana where condominium complexes are threatened by shoreline erosion. Maui has lost more than 4 miles of sandy beachfront over the past century and continues to lose more than half a foot each year in Kahana.
A video presentation of Maui County’s proposed erosion mitigation plan for Kahana Bay can be viewed at https://youtu.be/lE-1qH–7EY.
“Existing shoreline armoring fronting four of nine condominium complexes in the Kahana Bay beach cell have contributed to beach loss and increased erosion fronting neighboring properties,” according to the request for proposals.
And, more shoreline hardening is planned at the Hololani Resort in Kahana, it points out.
The document says that the county is partnering with condominium associations and the community to assess alternative erosion mitigation strategies “that can protect threatened buildings while restoring and conserving the natural environment in an effort to discontinue the cumulative effect of armoring.”
The project aims to explore the feasibility of beach restoration at Kahana Bay by replenishing sand that has been washed offshore. The study would include a 3,000-foot beach area from Pohaku Park, also known as “S-Turns” at the south end to Kahana Stream at the north end. There are nine condominium complexes within that area.
“The components of the study include investigating location, quantity and quality of offshore sand resources; assessing shoreline restoration design alternatives involving sand and/or erosion control structures; and developing cost estimates for such alternatives,” according to the invitation for bids.
The Kahana regional erosion mitigation project would be about double the size of the 2012 beach nourishment effort at Waikiki that stretched across 1,730 feet of shoreline at the cost of $2.4 million.
Buika said that the Waikiki project has been “widely regarded as a success.”
“The Waikiki project, as well as the Iroquois Point project on Oahu, and other small-scale beach restoration projects on Maui, all provide good models for planning and designing future projects,” he said. “That said, every beach restoration project has site specific requirements related to environmental conditions, coastal processes, sand supply and project goals. The study will assess many alternative beach designs for Kahana Bay specifically, while drawing from lessons learned from other projects.”
Buika said that the amount of sand needed for the Kahana regional project and its cost will be determined as part of the study.
“The cost will depend on many factors, including the sand quantity, location of offshore sand sources . . . and whether additional structures, such as groins, are needed along the shoreline to control erosion,” he said.
The feasibility study will be used to address the problem of shoreline erosion on Maui and statewide.
Consultants should plan to complete the study within nine months, with the goal to be ready for a project kickoff by around Jan. 4.
The county Planning Department and the University of Hawaii Sea Grant coastal hazards specialist will manage the project with the selected consultant.
For more information, contact Buika at 270-6271 or firstname.lastname@example.org.
* Brian Perry can be reached at email@example.com.