Multi-Scale Modeling of a 500-Year CSZ Tsunami Inundation with Constructed Environment

A numerical tsunami model that can incorporate the constructed environment onshore is difficult to build either with a two-dimensional (2D) approach or a three-dimensional (3D) approach. A depth-integrated 2D approach assumes independence of the z-coordinate (in the vertical direction), thus can be oversimplified when modelling complex and variable flow. 3D models require very fine meshing near coastal structures, which dramatically increases the computational cost and makes modeling of some problems impractical. In this study, an experiment modeled after a 500-year Cascadia subduction zone (CSZ) tsunami inundation with a constructed environment is modeled and analyzed. Comparisons are made between a 2D model and a 3D model. Modeling reasonably selected subdomains is shown to alleviate the computational cost of the 3D model. The 2D model does not accurately capture the important details of the flow near initial impact due to the transiency and large vertical variation of the flow. The 3D model does a better job at a much higher cost of computational resources.