Scientists have discovered that parts of Oahu, Hawaii, are sinking into the ocean 40 times faster than previously estimated, putting homes and businesses in jeopardy.
Honolulu, Waikiki, and Pearl Harbor at risk
Conditions have worsened so much that low-lying areas in Honolulu, Waikiki, and Pearl Harbor could face severe flooding in the coming decades, with infrastructure damage projected to cost billions of dollars.
“In rapidly subsiding areas, sea level rise impacts will be felt much sooner than previously estimated,” said Kyle Murray, a geophysicist at the University of Hawaii at Manoa, who co-authored the study published in Communications Earth & Environment, according to Earth.com.
The research team investigated the combined effects of sinking land and rising sea levels due to climate change, which could lead to extreme flooding in Oahu.
New study shows sinking land will accelerate flooding
According to Dr. Kristina Dahl, vice president for science at Climate Central, sea level rise is already increasing coastal flood risks in low-lying neighborhoods around Honolulu. This new study indicates that land subsidence could significantly worsen those risks.
To analyze this trend, scientists examined nearly two decades of satellite data from the Hawaiian Islands. They cross-referenced this data with Global Navigation Satellite System (GNSS) measurements to calculate subsidence rates.
Using high-resolution digital elevation models and geospatial analysis, researchers mapped the coastal topography and tracked even the most subtle elevation shifts.
This allowed them to create a flooding model, which demonstrated how sinking land combined with rising sea levels would accelerate inundation in key areas.
Hawaii’s natural sinking process is accelerating at alarming rates
For millions of years, Hawaiian islands have gradually sunk due to their weight and shifting tectonic plates. However, the current rates of subsidence observed in Oahu are unprecedented.
While Oahu’s typical subsidence rate was just 0.6 millimeters per year—roughly the thickness of ten sheets of printer paper—certain coastal areas are sinking at 25 millimeters per year, 40 times faster than expected, according to a University of Hawaii at Manoa report.
This far exceeds Hawaii’s historical average subsidence rate of 1.54 millimeters per year since 1905.
Industrial areas and key infrastructure face immediate destruction
The industrial region of Mapunapuna, located on Oahu’s south shore, is particularly vulnerable due to its foundation on sediments and artificial fill, Murray explained.
“We think the majority of subsidence is related to the compaction of these materials over time,” he added.
Combined with flooding, subsidence could increase this area’s flood exposure by over 50% by 2050, potentially compressing flood preparedness timelines by up to 50 years, said Phil Thompson, study co-author and director of the University of Hawaii Sea Level Center.
By 2080, flooding will likely become more widespread in Waikiki, downtown Honolulu, and Daniel K. Inouye International Airport, causing major societal and economic consequences, SFGate reported.
Projected costs and urgent need for action
“Hawaii tourism, coastal development, and ecosystems will face major disruptions,” study authors wrote.
They estimated that over $12.9 billion worth of infrastructure is at risk from flooding and related damages on Oahu alone.
Scientists call for policy action to mitigate risk
Researchers hope their findings will help policymakers develop effective strategies to reduce the impact of future floods.
“Our research provides critical data to inform state and county decision-making, improve flood exposure assessments, strengthen infrastructure resilience, and guide long-term urban planning,” said Chip Fletcher, co-author, and director of the Climate Resilience Collaborative at the University of Hawaii at Manoa.
“This work directly serves the people of Hawaii by ensuring that local adaptation strategies are based on the best available science—ultimately protecting homes, businesses, and cultural areas,” Fletcher added.