Hawaii & Alaska
Storm at Waianapanapa State Park in Maui.

HI - How Wave Power Drives Coastal Erosion in Hawaii Quantified by Researchers

The average power of waves hitting a coastline can predict how fast that coast will erode.

Over millions of years, Hawaiian volcanoes have formed a chain of volcanic islands stretching across the Northern Pacific, where ocean waves from every direction, stirred up by distant storms or carried in on tradewinds, have battered and shaped the islands’ coastlines to varying degrees.

Now researchers at MIT and elsewhere have found that, in Hawaii, the amount of energy delivered by waves averaged over each year is a good predictor of how fast or slow a rocky coastline will erode. If waves are large and frequent, the coastline will erode faster, whereas smaller, less frequent waves will result in a slower-eroding coast.

Their study helps to explain the Hawaiian Islands’ meandering shorelines, where north-facing sea cliffs, experiencing larger waves produced by distant storms and persistent tradewinds, have eroded farther inland. In contrast, south-facing coasts typically enjoy calmer waters, smaller waves, and therefore less eroded coasts.

The results, published this month in the journal Geology, can also help scientists forecast how fast other rocky coasts around the world might erode, based on the power of the waves that a coast typically experiences.

“Over half of the world’s oceanic coastlines are rocky sea cliffs, so sea-cliff erosion affects a lot of coastal inhabitants and infrastructure,” says Kim Huppert ’11, PhD ’17, lead author of the study and a former graduate student in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “If storminess increases with climate change, and waves get bigger, we need to understand specifically how waves affect erosion.”

Huppert, who is now a senior research scientist at the German Research Center for Geosciences, has co-authored the paper with Taylor Perron, professor of earth, atmospheric, and planetary sciences and associate department head at MIT, and Andrew Ashton of the Woods Hole Oceanographic Institution.

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