An assessment of coastal change over the past century has found 70 percent of the beaches on the islands of Kauaʻi, Oʻahu and Maui are undergoing longterm erosion, according to a report released by the University of Hawaiʻi at Mānoa and the U.S. Geological Survey.
Scientists from UH Mānoa’s School of Ocean and Earth Science and Technology and USGS studied more than 150 miles of island coastline and found the average rate of coastal change was 0.4 feet of erosion per year from the early 1900s to 2000s.
Of the three islands, Maui beaches experienced the highest rates and greatest extent of beach erosion, with 85 percent of beaches eroding. Erosion is the dominant trend on all three islands with 71 percent of beaches eroding on Kauaʻi and 60 percent of beaches eroding on Oʻahu.
Researchers used historical data sources such as maps and aerial photographs to measure shoreline change at more than 12,000 locations. This analysis of past and present trends of shoreline movement is designed to allow for future repeatable analyses of shoreline movement, coastal erosion and land loss.
“Over a century of building along the Hawaiian shoreline, without this sort of detailed knowledge about shoreline change, has led to some development that is located too close to the ocean,” said Charles Fletcher, UH Mānoa geology and geophysics professor and lead author. “A better understanding of historical shoreline change and human responses to erosion may improve our ability to avoid erosion hazards in the future.”