Congratulations to Honolulu Mayor Rick Blangiardi, City Council Vice Chair Esther Kia‘aina, and the entire City Council for approving and signing into law Bills 41 and 42.

These bills reaffirm the city’s commitment to safely adapt to sea level rise by thoughtfully planning, permitting and developing Oahu’s coastal communities while conserving public beaches. Oahu now joins Maui and Kauai counties in using place-based historic erosion data to determine shoreline setbacks.

This achievement charts a path forward on Action 29 of the “Ola O‘ahu Resilience Strategy”: Protect beaches and public safety with revised shoreline management rules.

For most of Oahu, Bill 41 increases the shoreline setback to 60 feet plus 70 times the annual erosion rate as measured from the shoreline, not to exceed 130 feet. This bill also codifies changes made at the state level under Act 16 (2020) that outlaw private shoreline hardening on sandy beaches.

Bill 42 aligns Honolulu’s Special Management Area ordinance with other changes made to the Hawaii Coastal Zone Management Act under Act 16. It also states that Honolulu shall seek to minimize future development in the sea level rise exposure area, and if that isn’t feasible, to adapt new structures to accommodate rising water.

Together, these changes strengthen coastal zone management in the face of accelerating sea level rise. Future shoreline development will now be a safer distance from the ocean, and existing development will slowly pull back through the process of renovation and repair.

In its 2023 report, the Intergovernmental Panel on Climate Change stated: “Sea level rise is unavoidable for centuries to millennia … and will remain elevated for thousands of years.”

In other words, sea-level rise is an unstoppable reality. It is not a distant problem — and Bills 41 and 42 alone will not be enough to ensure the future health, safety and welfare of our coastal communities and infrastructure.

Not every shoreline community on Oahu will be able to move away from the rising ocean. Waikiki, Kakaako, Iwilei and other heavily developed urban neighborhoods must consider new designs for roads, buildings, buried pipe and open spaces that accommodate rising groundwater, wave flooding and a lack of gravity-fed drainage.

Compound events where rain and high tide occur at the same time render existing gravity-based drainage systems ineffective, and rising coastal water tables cause flooding in basements, parking areas and below-ground spaces.

Models project that erosion hazard zones, annual wave flooding, groundwater inundation and storm drain failure are all going to rapidly accelerate. Within two decades, Oahu coastal communities, including urban Honolulu and Waikiki, will see high tide flooding over 50 days per year, and by mid-century, saltwater flooding at high tide will be a major nuisance affecting every aspect of island life.

This situation has the potential to amplify existing inequities in community services. For instance, coastal communities on Oahu’s Windward, North Shore and Leeward sides are all served by only one access road, a road already threatened by sea level rise. When high tide and high waves close this road, even temporarily, it also closes off emergency services, public transportation, access to schools and to jobs.

Decisive action entails steadfast leadership that recognizes the enduring public rights to natural resources, such as beaches and clean coastal waters, and the need for equitable solutions available to all communities.

Bills 41 and 42 must be followed with additional regulatory changes that promote redesigning our communities with resilient forms of architecture, flood engineering and infrastructure.

Community engagement on this topic is lagging. Tools such as transferable development rights, land swaps, relocation mechanisms and other adaptation strategies are still in their infancy.

Again, we sincerely commend city officials for taking the threat of sea-level rise seriously. We urge them to introduce bills to streamline resilient development and renovation islandwide, and to foster a new community vision enabling Oahu to become a resilient and safe economic hub unthreatened by the stresses of climate change.

Chip Fletcher, Ph.D., is interim dean of the School of Ocean and Earth Science and Technology, University of Hawaii-Manoa; Colin A. Lee is a climate change and resiliency policy analyst, UH-Manoa Climate Resilience Collaborative.