Jazaeri, Seyed Abbas2026-03-302026-03-302026-03-30http://hdl.handle.net/10393/51482https://doi.org/10.20381/ruor-31820Tsunamis are large and powerful waves typically generated by earthquakes, landslides, or volcanic eruptions in the ocean, propagating toward coastal areas with immense energy. Upon reaching shallow coastal regions, tsunami waves undergo rapid transformation, leading to inundation flows characterized by high velocities, strong accelerations, and complex hydrodynamic interactions with coastal infrastructure. Post-event field surveys conducted in the aftermath of recent tsunamis, such as the 2004 Indian Ocean, 2010 Chile, 2011 Tohoku, and 2018 Indonesian tsunamis, have consistently identified local scour around structures as a dominant mechanism of infrastructure failure. Despite the critical importance of this phenomenon, its influence on foundation design is often neglected in existing engineering standards and guidelines. Chapter 6 of ASCE 7-22 (2022) represents the only design standard that systematically addresses tsunami loading, with a section dedicated to local scour considerations. However, the provisions in this standard are derived from a limited body of research, and the effects of essential parameters, such as wall width and wall orientation relative to the flow direction, remain largely unexamined. This limitation highlights the need for controlled experimental data and physics-based numerical modelling to improve the understanding of tsunami-induced scour processes around coastal structures. The literature on local scour around columns is extensive. However, to the best of the authors' knowledge, no prior study has specifically investigated tsunami-induced local scour around walls subjected to unsteady tsunami-like dam-break bores. Such structures are more representative of coastal infrastructure such as building facades, yet their interaction with highly transient tsunami-like flows has received comparatively limited attention. Therefore, the primary objective of this study was to fill this knowledge gap through a comprehensive series of laboratory experiments. Among the influential parameters, wall width and orientation relative to the flow were selected for detailed examination regarding their effects on local scour development. The generating impoundment depth was varied to produce tsunami-like dam-break bores with different flow depths and velocities, enabling assessment of scour behaviour under a range of hydraulic loading conditions. Furthermore, two numerical models, MIKE3 HD/ST and FLOW-3D, were employed to evaluate their capability in reproducing this complex process. The laboratory experiments were conducted in the large dam-break flume at the University of Ottawa, allowing for detailed measurements of free-surface evolution, flow velocities, and bed morphology during and after bore impact. Scour development was monitored both spatially and temporally, with particular attention given to the formation of scour holes at the upstream corners and front face of the wall, where flow separation and vortex structures are most intense. The experimental findings demonstrated that wall orientation has a significant influence on the local scour depth by controlling the formation and intensity of horseshoe vortices. Walls oriented perpendicular to the flow consistently produced the deepest scour holes, whereas wall width exhibited a relatively minor effect. Comparisons with the envelope prescribed in ASCE 7-22 (2022) for estimating scour depth indicated that normalizing scour depth by projected width may misrepresent structural vulnerability. In several cases, walls parallel to the flow direction, i.e. having smaller projected widths, exhibited greater normalized scour depths despite shallower absolute values. These findings suggest that existing design approaches may underestimate scour-related risk for certain structural configurations. The numerical simulations showed that both models reproduced the scour depth with reasonable accuracy. Although minor differences were observed in the temporal evolution of scour depth, both models successfully captured the key characteristics of the scouring process, including the maximum erosion occurring at the upstream corner of the wall. Refinement of model configurations, such as selecting an appropriate turbulence closure scheme to resolve vortical structures around the wall and refining near-bed vertical mesh resolution, significantly improved the accuracy of the results without altering sediment transport calibration parameters such as bedload and suspended load factors, which are commonly adjusted in numerical sediment transport modelling. The results of this study provide new experimental data and numerical insights into tsunami-induced local scour around walls, addressing a significant gap in the existing literature. The findings have direct implications for tsunami-resistant design and highlight the need for revisiting current design guidelines and standards related to scour depth estimation. Ultimately, this work contributes toward improving the resilience of coastal infrastructure subjected to extreme tsunami loading conditions.enTsunamiLocal ScourCoastal EngineeringASCE 7-22Thesis