HONOLULU (KHON2) — Oceanfront property owners across Oahu could soon have to give up the ability to build on a significant portion of their land. That’s as new setback rules are proposed to take effect due to climate change and sea level rise. Always Investigating explains what’s at stake.

The Honolulu City Council is advancing Bill 41, a setback measure that would be the island’s first significant step toward managed retreat from eroding shorelines and a rising ocean level.

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“We’re seeing it on the North Shore especially — where homes are falling into the ocean,” said Honolulu City Council Chairperson Tommy Waters. “We have to do something. Doing nothing is not acceptable.”

While many homes are at immediate risk, others are in front of wide stretches of beach, but scientists said it’s only a matter of time until many more homes are in peril.

Models show “about one foot of sea level rise by mid-century, and then somewhere between 1.3 and eight feet of sea level rise by the end of this century, with an intermediate scenario of about 3.9 feet,” explained Brad Romine, a researcher with the University of Hawaii Manoa Sea Grant College Program.

A study this summer about Greenland’s melting ice accelerates the worst-case estimates.

“The arctic regions are warming four times faster than the global average,” Romine said. “This Greenland study provides important evidence that we’re kind of trending away from the lower-end scenarios.”

The Department of Planning and Permitting proposed a 60-foot minimum setback — up from 40 — across the urban core but anywhere else it could be that plus 70 times the annual coastal erosion rate up to a maximum setback of 130 feet.

“The whole purpose is to prevent development along shoreline property that may be subject to sea level rise,” said DPP Director Dean Uchida.

Some large parcels and commercial properties might have 130 feet to spare, but KHON2 wanted to know, what about homeowners that don’t have that much to give up?

“I’m concerned about people that own that land, and their houses are going to fall apart building on sand — are they going to lose their property?” said Hauula resident Marvalyn Heery. “It’s kind of sad with the expense of buying.”

Some temporary exceptions are added in the current bill under review.

“We’re going to allow for some renovation work, repair work for existing structures,” Uchida explained. So we’re not telling that everybody got to move your house back, right? But on anything new construction on a vacant lot, you have to conform with this new ordinance.”

But there will be value limitations on even that repair work, and that could diminish property values along with loss of buildable land.

“It might be worthless,” Heery said. “It’s very sad, and they need to do something. Politicians really need to get together whatever side they’re on and find some way to balance it out.”

We asked how property owners could be compensated for lost value especially if they have to move in the long run. That’s not in this bill, but lawmakers say it needs to be considered.

“Perhaps condemnation might be the fairest thing so at least we pay fair market value for the land, but everything’s on the table and it’s still in early stages,” Waters said. “DPP floated the idea of allowing developmental rights mauka but again, to me that hasn’t been thought through enough yet.”

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We’ll follow up after Wednesday’s city council hearing on the bill.