The following video of the Fukushima tsunami is relevant:
The Aceh tsunami
Waves tend to wash over land and very quickly run out of energy.
So-called tsunami deposits, large gravel and sand deposits, have one irritating problem – where did the detritus come from? Wave deposition of sand is a well studied phenomenon but tsunamis depositing conglomerates are another matter, for the question is where did the tsunami pick up the material in the first place.
I suspect it’s another arguing the consequent fallacy – conglomerate is a sediment, therefore water brought it to there, and since it is such a large deposit, only a tsunami could have done it.
Except that observing actual tsunamis reaching landfall, this interpretation is not supported by the facts.
And when tsunamis do reach landfall, they very quickly run out of energy and as a consequence lose their carrying capacity. Observe the behaviour of water dumped on northern Australia during the monsoon season, and look for the gravel deposits. The gravels are there in the river channels, but as I discovered at the Drysdale River Crossing in the north east Kimberley on Carson River Station, on the way to the King George River, a bulldozed sand/cobble ramp almost in the middle of the channel, doesn’t seem to show any evidence of typical sedimentary transport effects. Even after severe monsoons and cyclones in this region.
My experience dealing with the sampling of rivers and drainages for diamond indicator minerals suggests that these flow regimes may have the power to transport silt and sand sized particles and lag gravels on top of sand chocked channels, but the choked sand doesn’t move. Nor do these sand choked drainages act as jig beds during flood; the sand simply stalls between bedrock highs, and the water simply flows over them, with out picking up any sediment.
Which is why I have proposed the mechanism of magnetoturbidites, similar to the transported rock etc shown in the Star Wars Rogue One movie.
(Magnetoturbidites is an awkward neologism, and a better one should be considered).
But tsunamis don’t deposit gravels because when the do reach landfall, they have no sediment load, and when moving over land to become dissipated, the carrying capacity of the water is drastically reduced with distance, and hence the ability to transport massive volumes of gravels is absent.