Report gauges rising sea level’s threat to isles

Hawaii should plan for 3.2 feet of sea level rise in the middle to latter half of this century, causing the loss or compromise of more than 6,500 structures near the shoreline, including Waikiki hotels and North Shore homes.

That’s the conclusion of the state Climate Commission’s first major report, the Hawaii Sea Level Rise Vulnerability and Adaptation Report.

The 304-page report offers a description of Hawaii’s status today plus future scenarios with recommendations.

More than 3 feet of sea rise is what Hawaii should plan for now, according to the report prepared by Tetra Tech Inc. and the state Office of Conservation and Coastal Lands, although higher levels are “physically plausible” by the end of the century.

“Communities along our shores have flourished for centuries in harmony with the ebb and flow of the tides, punctuated by the occasional devastating hurricane or tsunami event,” says the report. “However, rapid warming of the atmosphere and oceans, caused by two centuries of unabated carbon emissions, is causing increasing rates of sea level rise, unprecedented in human history, threatening natural environments and development on low- lying coasts.”

While the report serves as a framework for identifying and managing climate change threats facing the state, it paints a pretty dire picture for the Hawaiian Isles’ future.

Statewide, 3.2 feet of sea level rise over the next 30 to 70 years would not only affect hotels, malls and businesses, but also schools, community centers, apartments and homes. Due to the loss of homes, more than 19,800 residents could be displaced.

Some 38 miles of roads statewide, including residential roads and sections of major coastal highways, would be chronically flooded.

The total economic loss to the state is projected at more than $19 billion, not including losses due to chronic flooding of roads, utilities and other public infrastructure.

The impact of sea level rise on Oahu is greatest due to its population size and the extensive urbanization of vulnerable coastal areas, said the report.

At stake is the popular “7-mile miracle” on Oahu’s North Shore, which is subject to further erosion.

With 3.2 feet of sea level rise, Oahu stands to potentially face $12.9 billion in structure and land loss; the displacement of 13,300 residents; and the loss of 3,800 structures, including hotels in Waikiki, and 17.7 miles of major roads due to flooding.

The greatest potential economic loss would be along Oahu’s South Shore, home to a large concentration of high-value residential and commercial developments. The Waikiki police substation and Hauula fire station are within the sea level rise exposure area, along with nine schools and the Pearl Harbor Naval Complex.

Oahu could also benefit from a more detailed analysis of impacts on its infrastructure, including harbors, airports and sewage treatment plants.

The Northwestern Hawaiian Islands at Papahanaumokuakea Marine National Monument are particularly vulnerable and already feeling the impacts of sea level rise. Resident Hawaiian monk seals, green sea turtles and Laysan albatrosses there face loss of habitat and might seek refuge in the main Hawaiian Isles.

Recommendations include the official recognition of the sea level rise exposure area as a “state wide vulnerability zone” so that new infrastructure and development can be planned outside of it. Hard armoring, in the form of sea walls, have had an overall negative impact on shorelines and so should be made carefully. Also, the real estate industry should consider new disclosure guidelines for properties in areas vulnerable to sea level rise.

“While the Sea Level Rise report focuses on sea level rise vulnerabilities and adaptation, it should also strengthen Hawaii’s resolve to do our part in reducing greenhouse gas emissions,” said Department of Land and Natural Resources Chairwoman Suzanne Case in a release.

State Sen. J. Kalani English (D, Hana-Upcountry Maui) expressed optimism.

“The sea level report submitted to the Climate Commission provides critical data as we work to reinforce the state’s resiliency and address the impact of climate change,” said English in a statement. “How we strategize and develop legislation to strengthen our state begins with understanding the risks and recommendations. This is important information to consider as we continue to be a leader in climate change mitigation.”

Hawaii is a member of the U.S. Climate Alliance, a bipartisan coalition of states honoring the commitment made under former President Barack Obama to reduce carbon emissions based on Paris Agreement guidelines.

The report was initially mandated by Act 83 in 2014 and expanded by Act 32 in 2017. It was completed three days in advance of its Dec. 31 deadline. The full report is available at climate adaptation.hawaii.gov.