Development of a numerical model for tsunami-driven debris transport and hazard assessment in a coastal community

Abstract

Tsunamis pose a critical risk to coastal communities, not only through inundation but also via debris transport, which intensifies damage by impacting infrastructure, blocking evacuation routes, and creating damming effects. This dissertation introduces a Debris Impact Hazard Assessment (DIHA) Framework to systematically evaluate tsunami-driven debris hazards at a community scale. The DIHR integrates numerical modeling and experimental data to generate actionable hazard metrics, including debris dispersion ratios, maximum impact loads, and intensity mapping. These metrics provide critical insights into vulnerable zones and high-risk areas, supporting disaster resilience planning and infrastructure design. The framework is applied to Honolulu Harbor, Hawai‘i, under a hypothetical 2,500-year tsunami scenario, demonstrating its effectiveness in identifying hazard hotspots.The newly developed numerical model has two key features. First, it introduces a semi-analytical solution for debris transport (tracking) model enabling to simulations of DIHA at a community-scale domain. Second, it incorporates a novel "randomness" variable at debris collision. Especially, this variable account for inherent uncertainties in the debris motion tracking, such as angular momentums, and varied reflection angles, enhancing predictive reliability while maintaining computational efficiency. The model simplifies debris representation through disk-shaped elements, validated against scaled laboratory experiments, ensuring robust simulation of debris dynamics. By capturing the probabilistic nature of debris transport, the model aligns closely with observed phenomena and improves the assessment of complex, real-world scenarios. The integration of DIHA and the randomness-enhanced debris transport model represents a significant advancement in tsunami hazard modeling. The findings demonstrate the importance of coupling site-specific hazard metrics with adaptive modeling techniques, bridging gaps between theoretical research and practical disaster management applications. This dissertation contributes to the scientific understanding and mitigation of tsunami-driven debris hazards, enhancing coastal community resilience against future tsunami events.