Numerical Analysis of Tsunami Bore–Induced Forces on Structures: Evaluating the Mitigation Potential of a Water-Filled Canal

Abstract Although tsunamis are unpredictable natural events, their impact on coastal areas can be mitigated through the implementation of effective countermeasures. Both engineered and nature-based strategies have been employed to dissipate tsunami energy to protect infrastructure near affected coastlines and safeguard human life. Among these countermeasures, water-filled canals have proven to be effective in reducing tsunami energy, as demonstrated through field investigations, experimental studies, and numerical analyses. The interaction of tsunami bores with water-filled canals and their subsequent impact on structures is a complex phenomenon that requires a detailed investigation. Understanding the flow hydrodynamics around the canal and structure, pressure distribution, and force-time history on structures is essential for optimizing such mitigation strategies. In this study, a series of calibrated numerical simulations were conducted using a prototype-scale model to investigate the effectiveness of various dimensions of water-filled canal to reduce the horizontal force exerted on a downstream column. FLOW-3D was selected as the modeling tool due to its robustness and demonstrated capability to simulate complex fluid-structure interactions. The reduction factor for a specific tsunami bore characteristic depends on the geometry of the canal. In this study, for a tsunami-like bore generated by a 4 m-deep dam-break flow, the reduction factor reached up to approximately 40% for a canal with a depth of 4.5 m and a width of 40 m. The results showed that the presence of the canal had a much greater effect on reducing the tsunami-like bore-induced force on the column during the initial impact. The results also indicate that there is a threshold for both canal width and depth, beyond which further increases do not significantly enhance force reduction on the column. Moreover, the effect of canal width on increasing the reduction factor is considerably greater than that of canal depth. These findings suggest that, in designing a canal as a tsunami mitigation countermeasure, both the absolute dimensions and the ratio of width to depth should be carefully considered.