Three-dimensional modeling of tsunami forces on coastal communities

Abstract

Recent research on tsunami inundation of coastal communities has largely focused on numerical modeling of tsunami runup on two-dimensional (2D) slopes or three-dimensional (3D) topographies with more complex shorelines. The coastal bathymetry that are generally applied are based on bare earth topography. Few studies have simulated overland flow around existing macro-roughness features such as nearshore buildings and bridges. This is often due to both lack of available data and the fact that it can be computationally demanding to incorporate these additional features. A consequence of omitting the built infrastructure from models is that, to predict tsunami forces and corresponding structural demand, extrapolations from overland flow data is necessary, and for densely populated communities these flow predictions may not be appropriate. In this work, a high-resolution 3D computational fluid dynamics approach is used to model tsunami inundation of a 1:50 model-scale, idealized community, representative of the town of Seaside, OR, USA, for which existing experimental data is available. Several buildings were selected, and flow characteristics—water level, velocity, and momentum flux—in the vicinity of these buildings were validated against experimental data. Several computational domains were analyzed and it is shown that local flow characteristics can be captured using subdomains of the community, reducing computational demand. Force predictions using direct integration of predicted pressure were compared with bare earth momentum flux calculations, and the importance of incorporating the constructed environment in force prediction models is discussed. Finally, comparisons with seismic load predictions for a selected building are presented for comparison.