Honolulu’s City Council has unanimously approved Bill 41, requiring coastal land owners to site newly built larger homes and buildings at least 60 feet from the shoreline outside of urban parts of Oahu.

Mayor Rick Blangiardi should sign the bill, in recognition that climate change and its accompanying sea level rise are already affecting Oahu, and there is no time to waste.

Bill 41 adds another 20 feet to the current 40-foot shoreline setback. It also requires an additional buffer zone for lots where the shoreline is already showing landward movement, based on erosion rates — calculated by multiplying annual beach erosion rate by 70, to protect the property for decades to come, with a cap of 130 feet. If signed, the rules would take effect in July 2024.

The policy has a solid base in observed data and environmental principals, using “historical erosion data to help make smarter, place-based decisions grounded in science,” as Surfrider’s Camile Cleveland testified.

A similar shoreline setback policy, based on observable erosion data, has been used on Maui and Kauai for decades. However, some beachfront property owners and companies involved in designing and building oceanfront Oahu homes have objected to the bill, pointing to the added restrictions placed on a shorefront property owner’s options for development.

The City Council compromised with property owners on this point, allowing for new construction with the existing 40-foot setback if homes have a “footprint,” or base, smaller than 1,500 square feet. This dubious compromise, however, enables and exposes new structures to threats from rising seas — and might, indeed, hobble adoption of an expanded shoreline setback, since Hawaii’s median home footprint has been estimated at under 1,200 square feet.

Continued vigilance on the part of the city will be required to avoid public burdens that could develop if structures built closer to the shoreline become threatened — and to ensure that the use of illegal, unpermitted shoreline hardening methods is not allowed to continue.

Blangiardi has until March 9 to make a decision on the bill, which was introduced by his administration.

Hawaii faces a projected 3.2-foot rise in sea level by 2060, and scientists estimate that Oahu could lose 40% of its beaches by midcentury. For that reason, the bill also eases the way for beachfront property owners to move homes mauka, away from the shoreline.

Homes built too close to the shoreline can be undermined by a receding coast, and the use of protective walls, sandbags, rocks and the like to protect structures diminishes the public beach and harms the coastal ecosystem.

Bill 41 also tackles the issue of “shoring up” structures that were built closer to the shoreline than currently allowed, before current land use laws, and rightly increases potential fines for violating setback laws, raising the limit for an initial fine to $100,000 per violation, up from the current cap of $10,000. Maximum daily fines that can be levied until a violation is corrected would be increased to $10,000 from $1,000.

Last year, the city reasonably approved a plan to build homes on “stilts” and that were well set back from the shoreline near the Velzyland surf break. A mile down the road, a house undermined by high waves and an encroaching shoreline fell into the ocean.

While a receding coastline may threaten land values, it does not justify illegal shoreline-hardening. So, as Bill 41 requires and some property owners are already modeling, the best policy is to build back from the predicted future shoreline, and to construct resilient beachfront structures that can survive changing conditions.