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As scientists warn of the intensifying threat of sea level rise, Kauai County planners have new rules to defend homes and businesses from a watery demise.

Owners must now hoist up new construction on stilts in areas susceptible to impacts from a projected 3.2-foot increase in sea level by 2100. The mandate also applies to rebuilds where the cost of improvements to a structure equals or exceeds 50% of the market value.

Kauai Mayor Derek Kawakami signed the legislation into law on Friday, making Kauai one of the first counties in the nation to regulate construction based on the future impacts of two menacing symptoms of sea level rise: .

The county’s  already account for many of the projected effects of coastal erosion. But no other entity in Hawaii currently regulates construction to protect buildings from the projected depths of these two other flood hazards.

For residential buildings, the lowest floor, including basements, must now be elevated at least 2 feet above the highest projected sea level rise flood elevation, as calculated by the authors of the seminal Ìý²¹²Ô»åÌý. Nonresidential structures need to be raised at least one foot above this flood water marker.

Existing buildings in these vulnerable coastal areas are not affected by the proposal, except for rebuilds.

A majority of the properties that the ordinance seeks to regulate already have to be built on stilts for insurance purposes. But insurance companies make flood risk determinants based on historical data, not the future effects of climate change. Kauai’s proposed ordinance would impose elevation requirements on some properties for the first time because it considers sea level rise projections through the year 2100.

Civil Beat’s coverage of climate change is supported by the Environmental Funders Group of the Hawaii Community Foundation, Marisla Fund of the Hawaii Community Foundation and the Frost Family Foundation.