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map of Oahu with arrow showing wind direction

Modeled seawater level on September 12, 1992, that shows the southern wind direction, changed from originally northeast. The maxima of sea level reached 1.5 meters above the mean level from Pearl Harbor to Hawaiʻi Kai. For an animated video of the modeled seawater level, click here.

University of Hawaiʻi research utilizing storm surge data from Hawaiʻi’s most destructive hurricane and 21st century modeling techniques provides meaningful predictions of sea-level rise on Oʻahu and can be expanded to all islands. The study shows for the first time, the potential and ready-to-go applicability when the two separate yet dynamic models are used together.

Storm surge can be one of the most devastating events when a tropical cyclone makes landfall. The more intense a tropical storm or hurricane, the stronger the wind, followed by an increased storm surge. Hawaiʻi experienced this devastation firsthand in September 1992 during Hurricane Iniki.

University of Hawaiʻi at Mānoa Civil and Environmental Engineering Associate Professor Albert S. Kim explored storm inundation risk in a preliminary study using static information of the initial stages of hurricane events and specific modeling for risk assessment to better calculate how to reduce risk and loss of life and property.

Current 2D modeling may not accurately mimic storm surges, therefore Kim employed the Regional Ocean Modeling System (ROMS) and Delft3D models for the study. ROMS is a free-surface, terrain-following, primitive-equations ocean model, which is widely used for a diverse range of modeling applications such as regional ocean circulations, oil transport on ocean surfaces, intensity variation of tropical cyclones and near-shore water quality investigation. Delft3D is a hydrodynamic model (either with fully 3D or reduced 2D setup), designed to simulate unsteady currents from the real-world. A seamlessly coupled ROMS-Delft3D model can also provide weather forecast for severe storm events.

The models were used to study storm surge caused by Hurricane Iniki by comparing time series of previously observed seawater levels with the research team’s modeled seawater levels in Honolulu during the storm. Using the water-level gauge station data, the model results were validated, despite slight variations.

Combined, the models will be able to predict sea-level rises in various hurricane scenarios. In addition, the study offers a potentially better optimal method for disaster mitigation, which can mimic complex 3D phenomena.

“Water is an invaluable resource for humans, as it is also essential for food and energy production. The amount of stormwater is freely available, but its influence is devastating. Using high-performance computer simulations, UH scientists can provide reliable disaster-mitigation strategies.” said Kim.

Predictive modeling can provide critical inundation information about an approaching hurricane and its potential hydrological influences over a wide range of coastal zones.

Having prior knowledge of potential hurricane impacts on coastal areas is beneficial from engineering and planning perspectives. The data gained from the study can be used not only for urban planning but also for emergency preparedness, especially when a hurricane is approaching particular coastal areas.

The study was done in collaboration with Professor Shaowu Bao’s group at Coastal Carolina University. The team’s next steps are to secure funding to expand the study to neighbor islands and make the collected data available online for planning purposes.

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