University of Hawaii study offers ways Honolulu can adapt to rising ocean waters

Scientists have been warning that Hawaii could face as much as 3 feet of sea level rise over the coming decades, and Honolulu is perhaps the most vulnerable as coastal flooding threatens to force as many as 13,300 people from their homes and cause an estimated $12.9 billion in economic losses.

Now comes a new study from the University of Hawaii School of Architecture that offers suggestions for how the city can adapt to the rising tide of its future.

“When you read sea-level rise reports, it’s scary,” said Judith Stilgenbauer, principal investigator of the project and professor of landscape architecture in the School of Architecture. “But there’s a real opportunity here to get an early start on planning for the inevitable.”

The 271-page report looks at the south shore of urban Honolulu, from Diamond Head to Pearl Harbor, and is the result of a two-year, state-funded research, ana­lysis and proof-of-concept design project by the University of Hawaii Community Design Center.

It also examined the past, present and future of three coastal regions of Honolulu — the Ala Wai Canal, Keehi Lagoon and Pearl Harbor’s East Loch — and offers some detailed near- and long-term designs and plans for how they can be transformed to better adapt to the encroaching tide.

Stilgenbauer said that in New York, planning for coastal resilience began only after the storm surge of Superstorm Sandy overwhelmed the city in 2012, causing $65 billion in damage. The city was forced into post-disaster recovery planning.

Honolulu hasn’t been hit by a major hurricane or a tsunami for a long time, she said, but it could happen at any time.

“We shouldn’t have to do post-disaster recovery planning here,” the professor said. “Anticipating these things can let us better prepare now for the future.”

The report, which also promotes planning elements of “connectivity” and “placemaking,” describes the concept of a South Shore Promenade, a continuous pedestrian and bicycle waterfront path that would connect a network of existing and proposed shoreline green spaces.

At the Ala Wai, according to the report, the promenade could become an elevated boardwalk for pedestrians and bicycles along the mauka bank of the canal. The elevated structure would allow unhindered water flow and protect wetland habitat from disturbance.

Also suggested in the long term is an elevated Ala Wai Boulevard with only one shared vehicular transit lane to prioritize pedestrians. The boulevard and the makai bank of the Ala Wai Canal would gradually be converted into “a multi-purpose Waikiki super dike.”

“The generous and landscaped promenade elevated on top of this new, wide dike along Ala Wai Boulevard provides an attractive urban waterfront amenity with a separation between walkers and bicyclists, increasing safety and overall connectivity,” the report says.

Meanwhile, the Ala Wai Golf Course eventually would be converted into wetlands and areas for wetland farming.

These changes would reduce the threat of flooding of the Ala Wai Canal.

All of the study-area proposals make room for wetlands — marshy areas that naturalize and adapt over time, increasing in capacity to withstand flooding and improve overall water quality, habitat performance and biodiversity, according to the report.

Stilgenbauer calls the various proposals in the report “speculative, nature-based living shoreline design solutions” that embrace coastal flooding rather than try to prevent it.

Many of them are inspired by traditional Native Hawaiian cultural land practices and are integral parts of “a soft, layered coastal defense system” that avoids hardened solutions such as flood walls, levees and dikes, Stilgenbauer said.

“And they will do more than just keep the urban area from flooding,” she said. “They provide ecosystem services such as clean water and habitat restoration.”

Stilgenbauer said she hopes the study gains traction and gets people thinking about what needs to be done to adapt to the future.

“We want to raise awareness and shift mindsets. There are some real opportunities here,” she said.

Chip Fletcher, associate dean and professor in UH Manoa’s School of Ocean and Earth Science and Technology, praised the the report for highlighting the vast potential for adapting to sea-level rise. He called the work innovative and practicable, building on the sea-level rise modeling that he and his colleagues produced in 2018.

“It’s really good stuff,” Fletcher said. “The fact-based land-use analysis, combined with the creative design depicting flooded landscapes, frees the viewer’s imagination to consider a future for Hawaii in which our communities live with water rather than fighting it.”

READ THE REPORT

The 271-page report can be found online at bit.ly/3rPqsxo.