Phase-Resolving Tsunami Modeling for the Design of Harbors and Infrastructure in the US Southwest

Abstract: Tsunamis are long period ocean waves mainly generated by large undersea earthquakes. Only a few centimeters tall as they propagate in the deep ocean, these waves can reach 10 m high or higher as they shoal and propagate shoreward. Tsunamis are classified as coastal hazards along Pacific States shorelines. In compliance with design requirements, harbors and critical infrastructure along Pacific States shorelines are required to prioritize tsunami resilience in their design.
During the past decade, Boussinesq-type wave models have been used as a reliable tool for simulating tsunamis from the basin scale to regional scale for tsunami propagation and coastal inundation. The phase resolving Boussinesq models simulate a variety of physics such as wave shoaling, refraction, diffraction, and wave frequency dispersion. Among these models, FUNWAVE-TVD has been constantly expanded in its applications, being implemented and calibrated for tsunami propagation and mapping tsunami flood extents along US shorelines, as well as for simulating the tsunami intrusion into harbors and sheltered regions. FUNWAVE-TVD has also been benchmarked by National Tsunami Hazard Mitigation Program (NTHMP), as a valid tool for tsunami modeling. HDR implemented FUNWAVE-TVD to analyze the resilience of coastal infrastructure along US southwest shorelines to tsunami waves by calculating tsunami flood extents, flow depths, and velocities based on the American Society of Civil Engineers (ASCE) 7-22 guidance. Accordingly, HDR developed model domains covering the entire project site, and the surrounding area, as well as part the ocean up to deep water (~100 m depth). The model domain is discretized into a 2D grid and forced in a phase resolving manner. The Site-Specific Modeling approach uses tsunami waveforms at a depth of 100 m as offshore wave boundary condition.
HDR will present FUNWAVE-TVD simulations quantifying tsunami risk to coastal infrastructure including harbors for the projects in the US Southwest. Accordingly, resilience design alternatives will be compared based on model outputs of extreme flow depths and velocities. Furthermore, model results of tsunami flood extents will be compared to the flood extents reported in ASCE geodatabase.

How does this project / topic contribute to the advancement of the industry and profession?: This project implements state-of-the-art coastal science in the engineering and design of harbors and coastal infrastructure, providing useful input to design tsunami-resilient harbors

Does the project / topic implement new and innovative techniques, materials, technologies, and delivery methods?: Yes, the project implements the Boussinesq wave model, FUNWAVE-TVD, in modeling tsunami flooding and underlying hazards. This model has been continuously expanded in its applications, being implemented and calibrated for tsunami propagation and mapping tsunami flood extents along US shorelines. Implementing this modeling framework for the design of tsunami-resilient harbors aligned with ASCE 7-22 design requirements is an innovative approach that we developed

What was the most challenging aspect of your project / topic and how did you handle it to ensure success?: The most challenging aspect was applying the high-resolution model to specific project sites along the US Southwest shorelines with site-specific shoreline features, as well as specific project design elements. Calibrating model coefficients and determining the optimum model domain and grid size were another part of challenge.

Who is the target audience for this paper?: Coastal engineers, coastal scientists, port engineers, port managers and stakeholders