UH team to map
erosion of beaches

Oahu data will be used as a
guide for future development

A University of Hawaii team of geologists plans to create detailed maps of the erosion patterns of Oahu beaches to help guide future development, beginning with the Windward Coast this fall.

Between 1999 and 2003, the UH's Coastal Geology Group made similar detailed comparisons of Maui's current coastlines with their changing shapes over the course of the 20th century.

The group, led by Professor Charles "Chip" Fletcher, will use a high-tech process to learn exactly how many inches or feet a year Oahu shorelines are growing or shrinking.

The Maui work took four years and cost about $500,000, Fletcher said. The Oahu job is expected to take similar time and funds, he said.

Portions of the work will be posted on the School of Ocean and Earth Science and Technology Web site,, as they become available. Detailed Maui information is there now.

Work on the coastline between Hanauma Bay and Kahuku is scheduled to begin this fall, Fletcher said.

The team uses historical aerial photos of shorelines, ground survey data and new aerial photos. The use of Global Positioning Systems and specialized computer programs yields highly accurate maps of erosion over time.

"By knowing the past history of shoreline change, we can statistically project into the future," Fletcher said.

Based on the UH group's data, Maui County last fall changed the way it decides how close to the ocean it allows development.

"It's been great. We really think that it's a big improvement to base shoreline setbacks based on historic erosion rates rather than just arbitrary numbers," said Mike Foley, Maui Planning Department director.

Since Maui County changed its rules last fall, about an equal number of building setbacks from the ocean that have been closer, farther or about the same as under former rules, Foley said.

"Oahu is not talking about changing its setback, but they are interested in getting erosion rate data," Fletcher said.

The Kailua-based Harold K.L. Castle Foundation has awarded a $100,000 grant for use on the Oahu mapping project, and the U.S. Geological Survey has committed $75,000.

Honolulu appropriated $380,000 for the work in 2003, but a contract must get a final approval from the City Council, a city Planning Department worker said.

Fletcher said he is thrilled to be able to take the project to another island: "This is among the most high-resolution shoreline change data in the world."

Eventually, he said, "we want to map erosion along every stretch of shoreline in the entire state."


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