[Noel Weeks] The prominent alternative explanation is that the text is referring to a local flood in the Tigris/Euphrates’ valley. However, in both the Mesopotamian flood accounts and the biblical narrative the ark ends up in the north. The problem is that floods always take things downstream. Floods never take objects upstream. If this was a normal flood in the Tigris/Euphrates’ region, the ark would have gone downstream. The fact that it landed in the north in a mountain range goes against any local flood theory.In addition to what Steve says, I would add that a massive tsunami can push things a significant way upstream. The following illustrates that point graphically - around nine or ten minutes in, you can actually see a large structure headed upstream at what appears to be about 35 mph:
That said, neither a local flood nor even a local tsunami fully accounts for the ark being moved not just upstream but upstream to a significantly higher elevation. Notice how the tsunami pushes hard upstream within the existing riverbed and even over-flows the bounds of the river bed, yet a position less than 20 feet over the top over the bank of the river remains dry.
If the ark had merely been moved 5 miles upstream, a local flood could possibly account for the ark's movement. But movement upstream and up a significant elevation requires something more than a local flood, even one having the force of a major tsunami.
Given that the fountains of the deep were opened during the great flood, I'm sure that there were tsunami events taking place. It's quite possible that some of the ark's movement was due to a tsunami surge.
Of course, all of this seems rather unnecessary. The flood was world-wide and covered the tops of the mountains. Moreover, the whole reason for the ark was to preserve the life of humans and the air-breathing animals, something that would not have been necessary, had the flood only been local.