New Study Shows Shifting Hurricane Tracks Pose Flood Risks for Hawai’i

A new study led by researchers at the University of Hawai‘i at Mānoa indicates that as climate changes over the coming decades, hurricanes have a higher chance of landfall over the Hawaiian islands. Researchers from the universityʻs School of Ocean and Earth Science said this new pattern could pose severe flood risks along the coast and further inland.

Tropical cyclones usually get weaker or shift to the south when approaching the Hawaiian Islands due to the high-pressure system to the northeast, strong wind shear, and relatively low sea-surface temperature in surrounding waters. By gathering information from computer models, the researchers estimated that the changing climate could raise sea levels and allow for closer hurricane approach.

“Of the nearly 2,500 future scenarios in our study, we selected 24 critical storm events that track near the islands to assess the probability of coastal flooding and create detailed flood maps with 100-, 200-, and 500-year return periods,” lead author of the study Ning Li said. “With high tide and the projected sea-level rise, the modeling results from a direct landfall of an Iniki-like hurricane on the south shore of Oʻahu showed extensive inundation of downtown Honolulu and Waikīkī. Other hurricanes passing near Oʻahu can also produce severe surge and high surf, causing coastal flooding.”

“The findings of our study were not a surprise,” said Kwok Fai Cheung, senior author on the study. “Our recent experience with increasing number of storms tracking closer to the islands—for example, Hurricane Guillermo in 2015, Hurricane Celia, Darby, and Lester in 2016, Hurricane Lane, and Olivia in 2018—has already confirmed the change of hurricane patterns. The damage caused by Hurricanes Lane and Olivia underscores the importance and urgency of coastal storm hazards mitigation. This research should draw attention from state and federal agencies.”

Buildings along the coast planned or designed today will generally only last through the end of 21st century, the researchers said. This study has shown climate change can potentially increase the severity of natural hazards within that time period, making these structures less safe in the future. 

“The inundation maps from this study will help assess the types of buildings and structures in the areas of Honolulu that would be exposed to increased flood risks,” Li said. “This has significant implications for engineering practice and land-use planning. If climate change effects are factored into design requirements through new regulations, an economic incentive is created for responding to climate change in planning, siting, and construction of structures. This investment in increased resilience will offset the economic consequences of inadequate performance, loss due to damage, loss of marketability, or even failures of safety.”