As the Earth's topography is today, there simply isn't enough water to flood the whole planet. If there were, the planet would be flooded. The geological column clearly shows that there has been insufficient change in the Earth's topography in the last few thousand years to even begin to allow for the possibility that the Earth was smooth enough to for the existing water on the planet to create a global flood. So the first problem is that there isn't enough water to flood the planet.
The second problem is that once you have enough water to flood a planet, that planet will remain flooded. People speak of evaporation and run-off but evaporation only adds to the water vapor in the atmosphere. Once the water vapor reaches a certain saturation level, the vapor condenses and falls back to Earth as precipitation. Run-off doesn't work because once a planet is flooded, there isn't any place not covered with water, thusly, no place for the water to "run".
The Earth loses very little water. What we do lose is in the form of molecules drifting into space and this only occurs at the magnetic poles. But we also gain water from comets which enter our atmosphere at a fairly constant rate. They vary in size from that of a bowling ball to the size of small houses composed primarily of ice. Overall, the gain in water is much more than the loss. So we have more water now than we did 5,000 years ago. Yet, we don't have enough to flood the planet.
Now certainly anyone can start tossing out miracles performed by God as solutions to the problem. But when they do so, they violate biblical accounts by adding things not proclaimed by the Bible. And if God were to just perform miracles, there would be no need for a flood, an Ark or any of the rest of the story. He could just wipe out all life, except that which he specifically chose, by speaking such an occurrence into reality, (or so we're expected to believe).
The authors of the Bible didn't demonstrate a clear and precise understanding of the hydrologic cycle. So to them it made perfect sense that it might start raining and just continue to rain until the whole Earth was flooded. According to them, there was a large reservoir of water above the Earth's atmosphere, (Genesis 1:6-7). We know today that such a reservoir doesn't and couldn't have existed. So what we read in the Bible appears to be nothing but a popular story, repeated by many cultures, which offers no basis in reality. To me, this suggests that the flood story, like the rest of the Bible, is nothing more than the thoughts, feelings, beliefs and tales of ancient men.
Suggesting that "the flood" was a local flood disarms the entire premise for the flood story because it was supposed to wipe out all life on Earth which wouldn't be achieved by a local flood. So the end result is that there was no global flood because such a flood simply isn't possible. And there wasn't any local flood fitting the Bible story because such a flood wouldn't have required the gathering of animals, an Ark or any of the other things suggested by the story. In the end, the only real possibility is that the global flood is cultural mythology. It never happened. Yet, we find it in the Bible which casts a light on the book not likely to be acceptable by those who continue to wish to believe it to be the word of God.