A tsunami warning that sparked mass evacuations and traffic gridlock in many areas across the state, including Waikīkī, is drawing renewed attention to a 2022 University of Hawaiʻi study that modeled how to save lives during a short-notice tsunami event.
On July 29, a magnitude-8.8 earthquake off Russia’s Kamchatka Peninsula triggered statewide alerts in Hawaiʻi. While the most severe impacts were avoided, the fear of an incoming wave prompted thousands to flee Waikīkī, leading to significant traffic congestion on key evacuation routes. It was a real-world scenario studied and investigated by researchers in the Department of Urban and Regional Planning in UH Mānoa’s College of Social Sciences.
“The tsunami event is a powerful reminder of the need for research and training to increase preparedness and response capabilities,” Professor and study lead author Karl Kim said. “Because of the dense coastal development and exposure to tsunami and coastal hazards, we need to develop multi-modal evacuation plans. We need to encourage vertical evacuation as well as early evacuation to avoid congestion and delay.”
In their study, UH researchers simulated pedestrian, bicycle and vehicle evacuations under a catastrophic tsunami scenario in Waikīkī. The findings revealed that without changes to infrastructure or improvements in early alert systems, an estimated 38,760 lives could be lost in a worst-case event.
Research looks at evacuation options
The study evaluated four evacuation scenarios and emphasized two life-saving strategies: vertical evacuation and increased travel capacity. Simulations showed that vertical evacuation—moving to upper floors of reinforced buildings—was the most effective option, potentially saving more than 55,000 lives. Conversely, motor vehicle evacuations were found to carry the highest fatality rates due to congestion and delay.
One key intervention modeled was the addition of a new bridge over the Ala Wai Canal, connecting Kālia Road to University Avenue. The proposed bridge, which has undergone a City and County of Honolulu feasibility study, would significantly increase evacuation capacity. The study found that the bridge could save an estimated 13,860 lives by easing bottlenecks and improving flow out of Waikīkī.
The researchers also explored how reducing tsunami detection and alert times from 10 to 5 minutes could save more than 4,500 lives by giving people more time to evacuate. When both the new bridge and earlier warning times were combined, the fatality rate dropped to approximately 20%, the lowest of all simulated scenarios.
The recent tsunami alert highlighted the challenges of mass evacuation in dense urban areas and underscored the study’s recommendations: invest in infrastructure, improve early warning systems and educate the public on vertical evacuation as the safest option in a short-notice event.
“In disaster planning, every decision, from where we build to how we evacuate, can mean the difference between life and death,” PhD candidate and study co-author Farnaz Kaviari said. “This recent tsunami warning shows that what we model is not hypothetical. Technologies and simulation models allow us to test what works and what doesn’t, so every well-informed decision brings us closer to saving lives.”
