Report shows increase in flooding nationwide

LIHU‘E — Experts say sea-level rise flooding across U.S. coastlines is increasing, and if the trend continues, the water levels seen during high-tide flooding, also known as king tides, could become the new high-tide mark.

That’s included in the recently released 2019 State of the U.S. High Tide Flooding Report from the National Oceanic and Atmospheric Administration, which also includes a 2020 outlook.

And, days before the new reports were released, legislators on Capitol Hill dedicated more than $4.2 million to monitor rising sea levels in Hawai‘i, as well as extreme weather events.

Senator Brian Schatz (D-Hawai‘i), a member of the Senate Appropriations Committee, announced the funding for the University of Hawai‘i’s Pacific Island Ocean Observing System on Wednesday.

“As an island state, we’re already fighting rapid sea-level rise,” said Schatz. “By improving our ability to track sea levels and forecast extreme-weather events, we can better protect our coastal communities from these climate-change impacts.”

The money will help to deploy more ocean sensors to observe and monitor sea levels, tides, currents, waves and temperatures. The data collected will improve forecasts of severe-weather events, like king tides and hurricanes, so that families, businesses and communities can make resilience plans to stay safe and protect their livelihoods in the face of the changing climate.

The NOAA report describes high-tide flooding as occurring when “ocean waters reach 0.5 meter to 0.65 m above the daily average high tide and start spilling onto streets or bubbling up from storm drains.”

This usually happens when the highest tides of the year combine with already increased sea levels and trigger coastal flooding.

In Hawai‘i, several reports have already been created that map out vulnerabilities to sea-level rise and project sea-level rise in the future. One of these reports is the Hawai‘i Sea Level Rise Vulnerability Report, which includes the interactive Sea Level Rise Viewer, developed by the University of Hawai‘i at Manoa.

Projections show that, at the current rate, there could be as much as a 3.2-foot rise of the global mean sea level by the year 2100. That much of an increase would put highways and properties underwater in Hawai‘i, according to that interactive tool, available online, which maps out sea-level-rise exposure areas with a rise of 0.5 feet to 3.2 feet.

On Kaua‘i, experts have worked with community members to create the West Kaua‘i Community Vulnerability Assessment, which identifies low-lying areas that are vulnerable to the projected sea-level rise, as well as associated king tides.

That report states the sea level around Kaua‘i has risen 6.6 inches in the past century, and could rise up to 96 inches by the end of this century.

After checking in with the community, those researching the West Kaua‘i report distilled the area’s vulnerability to three primary coastal hazards: coastal erosion, passive flooding and annual-high-wave flooding. It contains town-specific recommendations to mediate those hazards.

The 2019 State of the U.S. High Tide Flooding Report and 2020 Outlook also contain mitigation recommendations and suggests budgeting for necessary coastal flood responses, for research — like the items included in the recent batch of federal funding — and for establishing resiliency for the future.


Jessica Else, editor-in-chief, can be reached at 245-0457 or


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