The Flood story is a myth. A myth is a story that is grounded in some sort of truth but has been exaggerated and changed with time based on multiple oral re-tellings.
There is no reason to believe the Flood story is true. It doesn't even have to affect your faith, God's legitimacy, Jesus' legitimacy or the Bible's legitimacy. So why try so hard to make it true when the vast majority of evidence points to the contrary. The ONLY piece of legitimate evidence that anyone has stating the Flood is true is a collection of ancient manuscripts.
Is there ANY non-Biblical evidence to support the flood?
1) Seashells in Kansas.
I'm a geophysicist and if anyone took the time to look into plate tectonics, uniformitarianism, sedimentation or radiometric dating I feel like its incredibly IMPROBABLE that a catastrophic flood brought sea shells to Kansas and not the host of other processes in operation. I just wrote a massive paragraph which could be called Geology 101, but if anyone is interested just PM me rather than me boring you with a long post here.
2) The processes in operation today are different than they were in the past.
This argument throws science out the window. Science is based on the fact that the physical laws in existence have been constant. (For example, the gravitational constant of 6.67*10^-11 was not, at one time, smaller or larger). It uses this assumption to extrapolate data into the past and future.
Granted, this is quite a large assumption to make, but if you don't make this assumption then it devolves into Last Thursdayism. Also, we make this assumption everyday: you assume that when you wake up tomorrow the gravitational constant will not be larger than it was when you went to bed. If, however, you wake up tomorrow and find that you weigh more, the moon is closer to the earth, the earth is closer to the Sun and several satellites delicately placed in near-earth orbit have fallen into the Earth, then perhaps we need to re-evaluate science's assumptions
Okay, so AV and dad I have a question:
If you see something, do you respond to it? For example, if you see a car coming towards you, do you get out of the way?
I'm assuming you would. This is because you have a HYPOTHESIS that says that you would be seriously injured or killed if you didn't get out of the way and this HYPOTHESIS has been validated based on EVIDENCE you have gathered about what happens to people that get in the way of a moving vehicle (based off the news, stories, movies, maybe personal experience?

. Therefore, you see it as PROBABLE that, if you were to not move, your HYPOTHESIS would be validated and you would be seriously injured or killed.
This is the scientific method. And you, me and virtually everyone applies it daily. If you don't apply it, you'll probably die which is kind of ironic because it fits with natural selection
Also, one of your big arguments is that you found shells in Kansas. I thought the flood wiped out all living creatures...but there obviously were a lot of shells around. In fact, any water dwelling creature did just fine. So what does God have against land creatures? Or is he in cahoots with the sharks and dolphins? And if he just wanted to punish humans for being evil why didn't he just give us H1N1 a few thousand years before we had the medical advancements to stave it off? That way he didn't have to show favortism for the sharks versus the lions.