A plethora of studies in the last decade described tsunami hazards and studied their evolution from the source to the target coastline but mainly focused on coastal inundation and maximum run-up. Nonetheless, anecdotal reports from eyewitnesses, photographs, and videos suggest counterintuitive flow dynamics, for example, rapid initial acceleration when the wave first strikes the initial shoreline.
Based on a set of three-dimensional Lagrangian numerical simulations, myself, Dr. Roberts Weiss and Dr. Costas Synolakis studied this acceleration in Marivela et al, (2017). This flow speed up always occurs in the proximity of the shoreline regardless of the height wave as one of the publication conclusion.
The following figures indicates that the highest destructive capacity of tsunami occurs when momentum flux reaches its maximum which takes place in the initial shoreline environment. This maximum coincides with the local maxima of the potential and kinetic energy which makes the shoreline to be the most turbulent and dangerous area from the entire breaking and inundation processes.
Therefore, momentum flux is a more important variable, over and above potential and kinetic energy, to be considered in tsunami-hazard and mitigation evaluations as well as in nearshore structure design.
Roberto Marivela, Ph.D. 