A Hydrodynamics Perspective for the 2004 Megatsunami

The megatsunami of 26 December 2004 was the first tsunami with transoceanic impact since the 1960 Great Chilean and 1964 Great Alaskan tsunamis. Because of the distribution of deaths among a large portion of the nations of the world, the 2004 Boxing Day tsunami is the first universal natural disaster of modern times. For the purpose of adequate mitigation of future tsunamis, it is important to understand which factors control most critically the final characteristics of the flooding, namely runup and inundation. Their successful modeling requires not only a credible database of inundation parameters, against which models can be tested through numerical simulation of the generation, propagation to the local shores, and final interaction of the tsunami with the target beaches, but also in situ observations that help identify unusual impact and previously unrecognized or controversial flow patterns. Here, I comment on the hydrodynamic lessons -mostly relearned- and describe remaining challenges