Balboa Island trying to outsmart a rising sea

As people stroll Balboa Island’s picturesque waterfront, some wonder how much one of those cozy cottages costs.

City officials think about another price tag: how much it will take to defend those homes against rising sea levels.

City engineers revealed last month that it could cost about $60 million to replace Balboa Island’s aging seawalls; otherwise, residents could risk more high tides washing into their streets and homes.

The island, 4 to 8 feet above sea level, represents only a small portion of coastal communities’ looming problems from climate change. Replacing all of Newport Beach’s seawalls could require nearly $500 million, engineers say, although some structures could be retrofitted, so the actual price would be less.

“The costs are a worst-case situation,” said City Councilman Ed Selich, who represents Balboa Island, where a projected 4-foot rise in sea level by 2100 would inundate homes. “We don’t know whether those projections are going to hold over the long haul, so we have to come up with a phased approach.”

Already, the city’s islands flood during extreme high tides. Crews pumped water from streets last winter after an 8-foot tide, coupled with storm surges, breached the seawalls.

Officials want to extend the walls, to 10 feet from 9 feet above the average sea level, to brace for an expected 1-foot water-level rise by 2050. On Balboa Island, that could mean replacing the 1930s-era concrete barriers with steel ones or extending the current structures.

Most of the city’s seawalls have begun to show “widespread cracking,” a public works report says.

Replacing aging infrastructure is reason enough to act now, officials say.

Newport Beach has 17 to 18 miles of seawalls, about 4.5 miles of which are in public control and 13 miles of which are privately owned.

In the conservative city, politicians often avoid talk of climate change — especially its causes — and instead point to a demonstrated sea-level rise and its threat to real estate.

Selich said he doesn’t know if climate change is “man-made or simply a long-term cycle.”

“I just know that the evidence is there that [the sea] is rising,” he said, “and we have the responsibility to deal with it.”

Selich hopes that over the next five years the city can build up the walls on Balboa Island that are already prone to flooding.

Each new seawall would be engineered to accept a 4-foot extension, in anticipation of the 2100 scenario. City officials are relying on mid-range estimates derived from projections by the Army Corps of Engineers and other tidal studies.

“We don’t want to overbuild now,” said City Engineer Dave Webb, who recommends reassessing around 2050.

Officials are focusing now on Balboa Island because its walls are the oldest and publicly owned. A citywide project could require property owners to replace private seawalls — a daunting proposal that hasn’t been vetted for funding or feasibility. Another idea is to require ground floors to be built at the 10-foot tide level.

“Right now we’re just looking at Balboa Island,” Webb said. “The money is huge.”

The Balboa Island Ferry, which takes riders from the Balboa Peninsula to the island, alone could require $3.5 million to $5 million to retrofit its landings and adjacent fuel dock.

But the consequences of inaction could also be huge. Though Newport Beach hasn’t projected property loss from extreme floods, a study commissioned by the California Department of Boating and Waterways found that rising sea levels could cost beach cities hundreds of millions of dollars in lost tourism and tax revenue.

To fund the fortifications, officials have identified a few federal and state grants. But they say money also would have to come from other sources, such as city funds and homeowner assessments.

“At some point, the property owners are going to have to kick in,” Selich said.

That might be a challenge, especially for homeowners like Donna DiBari, whose home hasn’t flooded recently. In 1985, her first year on Balboa Island, DiBari saw extensive flooding, but her seawall hasn’t been breached much since then.

“If we felt it — if the water kept going into my garage — then I’d be afraid,” she said.

Fear isn’t motivating Webb. He says the seawalls have to be replaced anyway, so the city is using the latest science to choose a height.

“We’re trying to do some advance work here,” Webb said. “We don’t want to wait until we have a problem.”

mike.reicher@latimes.com