LIHUE (KHON2) — Kauai Mayor Derek Kawakami has signed a bill to keep new and substantial construction above the high water marks projected to come in the future. It’s one of the nation’s first regulations based on sea level rise estimates.

The new zoning law requires the lowest floor of all residential new builds — as well as buildings that renovate — to be elevated two feet above the highest sea level rise flood elevation. Non-residential construction and improvements must be elevated at least one foot.

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“Knowing what these flooding waters will essentially be, we need to be able to understand how our built environment should be designed around that,” Kauai County Planning Director Kaaina Hull said. “And so it essentially establishes sea level rise depths for passive flooding and highway runoff that will be caused by sea level rise and requires certain structures to be elevated to accommodate those waters when they occur.”

The University of Hawaii helped with models of potential inundation areas. UH had also assisted the state in developing a map of where sea levels would rise elsewhere in the state.

On Oahu, there are numerous stretches of highway, residential areas and commercial districts that would be under water if the Intergovernmental Panel on Climate Change’s estimate of 3.2 feet of sea level rise by 2060-2100 comes to fruition.

According to the Hawaii Sea Level Rise Vulnerability and Adaptation Report, there are 9,400 acres on Oahu within sea level rise exposure areas.

“That’s what scared me a case in point is our stormwater system and our sewer system,” Honolulu City Council Budget Chair Calvin Say said.

“You have a big shower, let’s say — or rainfall in Waikiki,” Say further explained. “It already backs up the sewer lines and the sewer system tied in with the stormwater system. And that’s why you always see that flooding that occurs.”

That’s why Say helped author the Honolulu City Council’s resolution that asked the state to invest in analyzing the predicted impacts of sea level rise on vulnerable infrastructure.

The resolution is on the city council’s agenda for their meeting Wednesday morning at 9:00 am. You can give testimony here.

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“If we’re going to spend money — spend money on our city and county public infrastructures,” Say said.