As sea levels slowly rise around the Hawaiian Islands, the surf eats away at oceanfront properties and threatens to make coastal roads impassible.

Even the most conservative scientific models show a half-foot of sea level rise, expected by 2030, would flood miles of highways and potentially cause hundreds of millions of dollars in economic loss.

It’s projected to worsen exponentially as sea levels rise by 1 foot by 2050 and 3 feet by the end of this century, causing an estimated $20 billion in economic loss just to physical structures. That doesn’t include compounding effects like the impact on tourism or business.

So what do we do? One option is moving our homes, businesses, hotels, roads, bridges and utilities back from the shoreline. But managed retreat, as it’s called, is no easy task.

A new state report released this week provides the most detailed look yet at the feasibility of pursuing this option in the islands.

“Managed retreat is complex to implement and given Hawaii’s exposure to both chronic and potentially catastrophic coastal hazards, we felt it was important to at least start a discussion to better understand what it could mean in Hawaii,” said Justine Nihipali, the state Office Of Planning’s Coastal Zone Management Program manager.

“The Managed Retreat Report is a first cut at a realistic analysis of the challenges and opportunities associated with managed retreat and considerations that must be examined if retreat is to be pursued in Hawaii,” she said.

The report emphasizes that this is one of three main options to adapt to sea level rise and related effects of climate change. Accommodation, which includes making assets flood-proof or elevating them, is another option. Protection is the third option, which could involve seawalls, dune restoration and beach renourishment.

The report underscores how hard it is to implement a managed retreat strategy. The political will is hard to come by, and the effort could divide communities, literally and figuratively, and cost exorbitant amounts of money.

There are fundamental questions that need to be answered. For instance, if people living in coastal homes need to move back from the shoreline, do taxpayers foot the bill or do the property owners?

The Office of Planning commissioned the 84-page report for $125,000. Consultants led by SSFM International spent 16 months studying background policies and planning work, reviewing research, developing scenarios, holding a symposium and making one major recommendation.

The report calls for creating a statewide leadership committee with experts in planning, social science, coastal hazards, economics and tax policy, legal and land use issues. That committee, presumably convened by the governor, would in turn recommend the best way for Hawaii to implement managed retreat.

In the meantime, the report lays out important do’s and don’ts and highlights a couple of examples and reasons why it could be worth the trouble of pursuing such a policy.

“Presently, there is a realization that retreat is a necessary adaptation strategy in Hawaii along with accommodation and protection but the question remains how to implement retreat and under what circumstances,” the report says.

If the state does go forward with managed retreat, the report says it’s critical for officials to make sure it’s the right strategy for the right areas and results in enhanced public access.

While the report says community outreach should be done ahead of time, it may be most doable only after a catastrophic event when money and resources are more available and political and social will is more easily found.

“The cost of land and real estate in Hawaii may make widespread use of buyouts at pre‐disaster, fair market value impossible,” the report says.

As a local example, the report recounted the 1960 tsunami in Hilo and the decisions made thereafter. Officials designated the area along the bay between Kamehameha Avenue and the ocean as a buffer zone, prohibiting building businesses there.

The government condemned and tore down the remaining businesses and planted trees to absorb the energy of future tsunamis. Hilo Bayfront Park, as it’s now called, has expanded and serves as a natural buffer between future tsunamis and downtown Hilo, as Holly Miller wrote in a 2011 report for the University of Hawaii Hilo.

Last year during Hurricane Lane, the park acted as a floodable open space, the report noted, and it’s become a popular place for residents and visitors to spend time and access the shoreline.

On the U.S. mainland, the report used Surfer’s Point in Ventura, California, as an example. A managed retreat project that began in 1995 restored the dunes and beach that had eroded along a hardened stretch of road.

The state should also change its laws to help implement the policy, such as new building restrictions and coastal armoring prohibitions, the report says.

“To rush haphazardly into retreat may waste precious and limited state, county and public sources of funds and lands and cause undesirable litigation,” the report says.

Hawaii has not yet agreed on the specifics of a retreat plan, the report notes.

“Currently, there are many state and county priorities — homelessness, food sustainability, energy neutrality, etc. — that strain resources. Thus, a more thorough, detailed understanding of retreat and what it entails is necessary.”

Read the full report below.