Every Sunday, when Pastor Tim Mason of Calvary by the Sea in Aina Haina looks out the window, it’s a reminder of a problem that is not going away anytime soon.

The church, which sits on the East Oahu shoreline, offers the congregation a sparkling ocean view during worship but must eventually confront the problem of erosion and sea level rise. It means the church, at the site for 60 years, might eventually have to sell the property and move farther inland.

“It’s not a question of if, but of when,” said Mason. “Eventually, Kalanianaole Highway, especially around Koko Marina and that area, is going to be underwater. Our counsel has begun talking about it, but talking about it in the sense of we’re going to have to do something someday.”

Mason said during the king tides last summer, ocean water rose up past a row of naupaka planted for defense along the property’s shoreline, and onto the grass. For him it was a wake-up call.

Statewide, geologists say 70 percent of Hawaii’s sandy shorelines are chronically eroding, from Kauai’s south shore to the resort areas of West Maui. On Oahu, 60 percent of shorelines are chronically eroding, from Waikiki’s tourist-laden beaches, along the Windward side to the North Shore, as well as Makaha.

Bradley Romine, coastal management and resilience specialist for Hawaii Sea Grant, said chronic erosion happens steadily over decades, in addition to short-term events like the North Shore’s monster waves in the winter, resulting in a retreat of the shoreline. It’s driven, in part, by sea level rise.

At Kualoa Beach Park

On Oahu’s Windward side, Kualoa Beach Park is one of the most rapidly receding shorelines in the state, according to geologists, having lost about 5 feet of sand per year for decades.

What was once an expansive beach is now a narrow strip dotted with the stumps of uprooted palms, with some washed into the water by the waves. From the air a visible line demarcates the ongoing erosion. On the ground, drainage pipes poke out of the sand.

Kualoa resident Irene Theoganis, who has rented a home on the shoreline since 1995, said it has gotten to the point where she needs to consider moving. She estimates having lost at least 20 feet from the yard in the past 15 years.

Theoganis, who runs the Shrimp Shack next to Ching’s Punaluu Store, said everyone along the shoreline has sandbags in preparation for flooding every time it rains.

“It’s just every year, it gets worse,” she said. “The tide comes higher and higher.”

She visits Kualoa Beach Park regularly to walk and swim, and is also saddened by the deterioration there.

Chip Fletcher, a geology professor at the University of Hawaii at Manoa, said the cause of erosion at Kualoa is the same as elsewhere on Oahu, compounded by structures put in place to harden the shoreline.

Kualoa Beach normally receives sand from the north, but for decades much of it has been trapped by a groin, according to Fletcher. As a result, the beach park has been receding rapidly. An additional row of concrete surge-breakers to slow the erosion has also been ineffective. But removing them now might make the situation worse, he said.

Over the years, the city has chopped down numerous palms at Kualoa and the windward coastline as the trees became unstable and posed a safety hazard, said Honolulu Department of Parks and Recreation Director Michele Nekota.

But neither sand pushing nor sand mattresses, which have been used as short-term solutions in Waikiki, appear to be viable solutions for Kualoa, she said.

“We know that as an island community we need to learn to work with water, rather than against it, and that hardening our shorelines or building seawalls just accelerates erosion on neighboring lands and beaches,” said Nekota in an email. “The Office of Climate Change, Sustainability and Resiliency is currently working on a resilience strategy to help guide the island as we adapt to sea level rise.”

Consequences of sea walls

Hardening a shoreline has two immediate effects, Fletcher said.

The beach in front of the sea wall begins to narrow, and will eventually disappear as sea level rises. Also, the sea wall accelerates erosion on a neighboring property without one. About 25 percent of Oahu’s shoreline beaches have either been narrowed or lost due to hardening, he said. These impacts are visible at beaches like Kahala and Lanikai.

“Look at our beaches on any weekend,” said Fletcher. “They are crowded with families. Beaches belong to our children. We are caretakers. If we keep building sea walls and destroying this legacy, we deserve to be known as a generation of thieves.”

Driving from Kualoa toward the North Shore, erosion is evident along portions of Kamehameha Highway, where chunks of missing pavement and craterlike holes are visible along the road’s edge, at Kaaawa as well as Hauula.

Sunset Beach on Oahu’s North Shore suffered from an unprecedented level of erosion during the most recent winter swell.

Giant waves in December carved a 20-foot cliffside, severely damaged a bicycle path, required the relocation of a lifeguard stand farther back and removal of a shed used to store Ocean Safety’s ATVs and equipment. Two months later the city cut down seven palms at Sunset Beach that it said were compromised by the erosion.

‘We have to get out of the way’

A recent report released by the state Climate Commission said Hawaii should plan for 3.2 feet of sea level rise in the middle to latter half of this century. The 304-page Hawaii Sea Level Rise Vulnerability and Adaptation Report also said 3.2 feet of sea level rise would result in $12.9 billion in potential economic losses and displace 13,300 residents on Oahu.

It paints a dire picture, pointing out that the “seven-mile miracle” along Oahu’s North Shore will “increasingly be eroded and permanently lost if hard structures such as roads and seawalls impede their landward migration.”

“We could look at this week by week, tree by tree and shed by shed,” said Fletcher. “That’s what happens when erosion collides with the fact that we’ve developed the shoreline. But if you look at it from a decade-to- decade point of view, there’s no doubt we have to get out of the way of rising sea level.”

Marilyn Cole, a North Shore homeowner for the past 45 years, said what used to be healthy sand dunes at Sunset Beach have been wiped out. She wishes the city would have established designated paths at the beach to help prevent foot erosion, and done more to prevent it.

Cole said she is lucky because her home is protected by reef and rock and a pair of ironwood trees with an extensive root system, so she and her husband have no plans to move. But neighboring homeowners stress out every winter, when the swells come in, fending off the waves with sandbags and tarps. In spring they get permits to push sand from the mouth of the stream back up along their homes.

In its report the state Climate Commission recommended that disclosures for vulnerable properties become mandatory, while other properties be acquired for protection and future development be planned farther landward.

While adapting is potentially costly, many have accepted there is no way to win against the changes.

“We know sea level is rising,” said Fletcher. “We know the shoreline is going to recede and move landward. In my opinion it’s our job to get out of the way.”

Mason in Aina Haina knows a decision on uprooting the church to a new location will have to be made sooner rather than later.

“The longer you wait, the more difficult issues will be,” said Mason. “We’re talking about property values.”