Beach-replenishment projects such as one the state is planning later this year in Waikiki may offer the best hope the Islands have to stave off the effects of erosion and rising sea levels, which are causing shorefront property to disappear at alarming rates.

As much as 25 percent of sandy beach land on O'ahu and Maui has been lost in the past 50 years, according to University of Hawai'i scientists who compared old and new aerial photos and maps of waterfront property. The erosion is continuing in many places across the state at a rate of between 6 inches and 12 inches a year.

And that doesn't take into account the effects of rising sea levels that may be caused by global warming.

By some estimates, a rise of 1 foot in worldwide sea levels — considered likely if existing warming trends continue — could leave more than half of Waikiki under water by the end of this century; existing shorefront property throughout the state might be pushed hundreds of feet inland in the same time period.

"The problem is a lot more widespread than most people understand," said Zoe Norcross Nuu, a UH Sea Grant extension agent on Maui. "Very few people are taking it seriously yet."

In recent years, geologists and others have been able to document erosion patterns and other coastal hazards in detailed ways. The research paints a long-term picture of disappearing beaches and other threats to existing homes, hotels and other structures.

Yet comparatively little is being done to meet the rising threat, especially on O'ahu, critics said.

"It's all politics as usual. The politicians talk a good game, but it's all window-dressing. They're not really interested in protecting the beaches," said Jan Roberson, Maui chapter chair for the Surfrider Foundation.

BAND-AID SOLUTIONS

The best hope to deal with erosion, at least in the short term, may lie in beach-replenishment programs. Ultimately, though, officials say that residents will have to reconsider the value of living and building structures as close to the water as possible.

Already Maui County has adopted new setback rules that require greater distance between the oceanfront and structures in areas where erosion rates are well-documented. Kaua'i County is considering even more stringent setback rules. But in Honolulu there's no effort under way to change setbacks that allow most structures to be built within 40 feet of the shoreline.

"People still want to live near the water and are willing to pay a high price to do it, but we need to change that thinking," said Cheryl Hapke, a U.S. Geological Service coastal geologist who produced a recent report on the disappearing shoreline in the Big Island's Kaloko-Honokohau National Historical Park, Hawai'i.

"The things we're doing now are just Band-Aids. Gradually people all across the country are going to have to retreat from the coast," Hapke said.

Barbara Guild is one person, however, who has refused to retreat. For the past 20 years, Guild has led a determined effort by a small group of condominium owners on Maui's north shore who have tried to protect a public beach next to their oceanfront property.

Last year, the group was honored by the American Shore & Beach Preservation association for its efforts, which include more than $200,000 in privately funded beach restoration efforts.

Soon after Guild moved into the 18-unit Sugar Cove condominium project in Sprecklesville, the small beachfront area began to disappear. The beachfront had been heavily mined for sand used to produce lime during the previous hundred years. In an effort to stop the erosion, condominium owners spent more than $500,000 on sand bags, then a wall of tires.

Neither worked, Guild said. "Walls aren't the answer. They don't protect a beach," she said.

SEA WALLS QUESTIONED

For decades, sea walls and other shoreline structures were the official way of dealing with erosion problems in Hawai'i.

No one knows how many such walls exist, but one recent study found that in the densely developed Honokowai area of Maui, about 3,500 feet of shoreline has been hardened over a 6,000-foot stretch.

State and county officials have determined that the walls accelerate beachfront erosion. Consequently, public policy now discourages the permitting of new walls, and state and county officials actively go after people who build such structures illegally.

"We take violations very seriously. Fines can be up to $1,000 a day for placing any structure within the legal setback area," said Art Challecomb, chief of customer service for the Honolulu Department of Planning and Permitting. "Sea walls are the most egregious of all the structures because they are put right on the interface of private property and the public shoreline and have the most impact. Literally, they are contributing to the problem."

Instead, beach-replenishment programs such as the one Guild started on Maui are seen as the best short-term solution to erosion problems.

"Ultimately, it became clear that we needed a new source of sand to replace the sand that was disappearing," said Guild, who has a degree in mechanical engineering from the University of California-Berkeley.

RE-CREATING BEACHES

In 1995, the condominium association began hauling in truckloads of inland sand mined elsewhere on Maui to create a new beach. Since then, the association has spent about $200,000 dumping more than 32,000 tons of sand in the area, enough to slow the erosion and create a new beach where none existed a decade ago, Guild said.

But it's unclear how long the replenishment effort can continue. Maui is running out of available sand for such projects and other commercial uses.

An official report issued earlier this year found that the last available sand on the island could be gone within five to seven years. The sand, mined from dunes near Wailuku at a rate of more than 300,000 tons a year, is mostly shipped to Honolulu to be used in the manufacture of concrete, the report said.

In Honolulu, officials plan to pump up to 10,000 cubic yards of sand accumulated in waters off Waikiki and bring it back onto the beach in a $500,000 replenishment project slated to begin this fall.

The pumping project is likely to be far more expensive than past beach-replenishment projects using trucked-in sand. But the pumping serves as a better environmental solution, scientists said.

Similar projects across the nation have met with mixed results.

"Typically, they are very expensive and sometimes they can have severe unintended environmental consequences," said Rick Wilson, author of the Surfrider Foundation's annual State of the Beach report.

"There have been a number of horror stories where incompatible material has been brought in and the beaches end up looking a lot worse than they did originally."

In Florida, one project was so poorly done that concerned residents successfully sued to have the renourished beach removed and replaced, he said.

STOPGAP MEASURES

Elsewhere, programs have met with great success. In Queensland, Australia, for example, government officials spent more than $10 million dredging 3.5 million cubic meters of compatible beach sand and moving it through a 5-mile pipeline to nourish disappearing beaches popular with tourists.

An artificial reef also was built to help slow erosion at the beach. In North Carolina, beaches that had replenishment projects suffered far less property damage from hurricanes than beaches that had no replenishment.

"The projects definitely need to be carefully monitored to be sure they're done right," Wilson said. "Sometimes the new sand can look and feel very different, turn the water murky, damage a nearby coral reef."

But even the best beach-replenishment projects are only stopgap measures, officials say. The only lasting solution to rising sea levels is to move more people and structures away from the ocean front, something that individuals and government have been reluctant to do.

In Honolulu, efforts to create new building setback laws have been stymied for years.

"My experience is that this idea wouldn't go anywhere. We tried to create more restrictive setbacks in the 1980s, but because of all the complaints, the City Council did not take any action," said Challecomb, the customer service chief.

There's been no other major push on the issue since then, he said.

Any tightening of O'ahu's 40-foot setback likely would result in many homes and properties not being able to rebuild in the same location, if structures were damaged in a hurricane or other disaster, Challecomb said.

On Maui, however, council members approved a hotly contested change about three years ago. Under the new rules, setbacks are calculated separately for each property using projected erosion rates calculated by UH. Under the setback rules, development is limited to 20 feet from the shore plus 50 times the yearly erosion rate for that site.

"There was a lot of resistance when the proposal first came out for review, especially from coastal property owners worried that the rules would take away their right to fully use and develop their property," said UH's Norcross Nuu.

"But in the 2 1/2 years since the rules were approved, there haven't been any complaints. The issues were very well-addressed and I think people realize now that the change was in their best interest."

WATERFRONT USE

Many scientists and officials contend that the best protection will be offered by changing public perceptions of waterfront use.

"Slowly, people are starting to realize that the coastline is very dynamic and maybe there is a benefit to moving away from it, rather than fighting it," said Dennis Hwang, a Honolulu attorney and author of the Hawai'i Coastal Hazard Mitigation Guidebook, a reference guide for safe coastal development. "The key is to start planning early for hazards that we know are coming."

One place to start would be with public projects, Norcross Nuu said.

"The most important thing is that we start moving infrastructure like wastewater treatment plants, power plants and major roads and highways back from the erosion," she said. "That would send a message that we're serious about dealing with the problem."

Reach Mike Leidemann at mleidemann@honoluluadvertiser.com.