I just have a few minutes, so this won't be very fleshed out. Some thoughts:
1) If Noah's flood was "local", and God promised never to do it again, then there might be some head-scratching going on when we think about Katrina, or the last colossal Asian Tsunami that happened a couple years ago.
2) To me, there's plenty of scientific evidence that the flood was global; it's just never put together into a Biblical worldview by secular scientists, and all of the evidence is broken up into pretty significant "local floods" throughout the world. That is, once you have a Biblical worldview, you read the news differently, and start noticing that most of the American midwest was once under water, that a colossal flood is thought to have carved the English Channel, that the Black Sea was once the site of a colossal flood, that marine fossils and what not are found on the tops of mountain ranges, and on and on.
One would almost think that all the world was once under water.
It's just that their worldview gives them fafillions and zazillions of years to work with, so maybe this whole part of the world was sunk 400,000 years ago, and this other part was deluged 2,000,000 years ago, etc. It's the time-scale that we would most disagree with, not necessarily the evidence, at least in my view.
3) If I'm not mistaken, didn't a Christian first mention plate techtonics? Either way, I would agree with the prevailing scientific worldview that the continents were once all together in one mass, and I think that the Bible actually hints at that when it talks about the waters being gathered together into one place. Why the colossal mountain ranges couldn't have been formed when this massive body broke up and the pieces were slamming into one another and ripped apart is beyond me. If so, then the water wouldn't have had to be high enough to cover Mount Everest as we now know it.
4) I think that the parallel between this and 2 Peter is poignant, as others have pointed out, and a local flood doesn't quite do it justice.
5) I think it is indicative that many people (I'm assuming, probably can't say for sure) who hold to an "old earth" also hold to a "local flood". Maybe that's a bit harsh, but some of you probably get my drift.
