There was a time when the shoreline was mostly defined as where the green ends and the sand begins. Now state officials know better and they're hoping to convince the counties, developers and home buyers that there are better ways to figure out where it's safe to build on beachfront property.

The stakes are high, considering a mistake could mean someone's dream home eventually falling into the sea. Or if a homeowner attempts to protect his house by building a seawall, it can lead to the disappearance of beach areas enjoyed by the public.

The shoreline is certified by the state and used by the counties to determine how close to a plot's waterside edge a homeowner can build.

But it's not as easy to determine as a line in the sand. Seasonal swells can change the shape of a sandy coastline dramatically in just a few months. Some plants survive well into the wash of the waves. And different beaches can have radically different rates of erosion.

The state supports looking at multiple factors when determining shorelines and is hoping to persuade Hawai'i's counties, as well as its real estate developers to take a similar flexible, scientific approach to figuring out the safest place to build beachfront homes.

"What we'd like to do is coordinate it so that the state and the counties are on the same page and that we're providing the same message to anyone — whether they're a private landowner or large-scale developer," Chris Conger said yesterday morning, before catching a plane to speak with county planners on Kaua'i.

Conger, a shoreline specialist with the University of Hawai'i's Sea Grant Program, has worked at the state Department of Land and Natural Resources since last year to bring more science into how the state's shoreline boundaries are determined.

He and Dolan Eversole, a Sea Grant coastal geologist with the DLNR since 2003, are traveling around the state until early April to hold five workshops for everyone from county planners to prospective home buyers to help them better understand where to build, how to build and how to spot a potential problem.

Similar workshops were also held in August.

Maui has already set an example, according to Eversole. "They've gone away from a standard 40-foot setback and they're actually looking at the rate of erosion when they calculate how far from the shoreline you need to set yourself," he said.

One way used in Maui to find the local erosion rate is through plotting the changes in a beach's shoreline over the years with aerial photographs and then using a formula to estimate the size of the erosion hazard zone.

The quicker the erosion rate, the larger the hazard zone.

The state hasn't always had its current approach to looking at the shoreline. Last summer groups, including the Sierra Club, filed a lawsuit to invalidate the Board of Land and Natural Resources' definition of shoreline, which they said gave preference to the vegetation line.

The lawsuit was dropped after the board agreed to amend its rules.

Jeff Mikulina, director of the Sierra Club's Hawai'i chapter, who along with Conger and others in the department yesterday, said that he was pleased with the changes in the way the state certifies the shoreline.

Peter Young, who has headed the board and led the department since 2003, signs off on the shoreline certifications.

He said he didn't feel comfortable with surveyors being the only ones in the field charting the shoreline, which prompted him to bring the University of Hawai'i in on the process.

And with Maui already using the erosion rate to tell builders where it's safe to put their buildings, Young said he's hopeful the state's three remaining counties will soon revise their own rules.