A residence with a small sandy beach flanked with temporary hardening structures, in Punalu‘u, O’ahu. (Credit: Shellie Habel, UH Manoa- SOEST)
O‘ahu’s iconic sandy beaches could face severe erosion by the end of the century, according to a new study from the Coastal Research Collaborative (CRC) at the University of Hawai‘i at Mānoa. The research, published in Scientific Reports, warns that 81% of O‘ahu’s coastline is at risk of erosion by 2100, with 40% of shoreline loss projected to occur as early as 2030.
These new projections represent a significantly more severe threat than previous erosion forecasts for the island, highlighting the urgent need for coastal preservation and climate adaptation strategies. The study emphasizes that climate change, rising sea levels, and human activity are accelerating shoreline retreat at a pace faster than previously understood.
The findings serve as a critical call to action for policymakers, environmental agencies, and coastal communities to implement sustainable coastal management practices to safeguard O‘ahu’s beaches—vital both for tourism and environmental resilience.
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“Our findings reiterate the already observed threat of coastal erosion as a hazard to sea level rise in Hawai’i,” said Richelle Moskvichev, geospatial modeler at the CRC in the UH Mānoa School of Ocean and Earth Science and Technology and lead author of the study. “In rapidly eroding areas, communities may see damage to roads, homes, or underground infrastructure. Shorelines along the north shore and east side of Oʻahu that are backed with hard-armoring, such as seawalls, could experience total beach loss.”
To predict erosion, the researchers employed a computer model that integrated around thirty years of satellite, aerial, and drone imagery. A key innovation of this model is its direct accounting for seasonal sand dynamics, illustrated by the winter swells on Oʻahu’s north shore that shift sand along the coastline. Drawing on prior modeling efforts, their own field observations, and anecdotal evidence from residents, the team expected their model to predict erosion across many of Oʻahu’s sandy beaches.
“By including additional satellite data and seasonal modeling, our forecasts show that erosion will increase by nearly 44% above our previous estimates in the short-term, meaning that we anticipate more severe erosion sooner,” said Moskvichev.
Coastal erosion can limit beach access, damage fragile ecosystems and infrastructure, and destroy homes.
“This study provides an update on potential areas of shoreline change around Oʻahu, and can inform long-term development planning for coastal communities and infrastructure of the island,” said Chip Fletcher, interim Dean of SOEST, director of CRC, and senior author of the study.
