There are those people that believe the bible is the literal factual truth of history. And there are people that believe the bible is a metaphorical story to teach us how to live our lives without having to necessarily being factual true in terms of history.
Personally I think its far more metaphorical than literal in nature. When it talks about God creating the earth in seven days that is a metaphor, not a literal story claiming the earth was created in seven days. And lets not forget that the people 4,000 years ago when this story was first going around had a much smaller view of the size of Earth. And that's something worth noting for Noah's flood too.
Ask a child whose neighborhood got flooded last year and to them it may well have seemed like their entire world got flooded because everything they knew was suddenly under water. Who do you think would have passed on the story of the biblical flood? Would it have been Noah? Or would it have been his children and grandchildren?
An interesting thing to note about Noah's flood. Methuselah, the oldest man in the bible, died at the age of 969 years old in the same year as the flood. I did the math once just because I was bored, and confirmed it now when I looked up is name online. Just a bit of biblical trivia for you if you didn't already know that.
One thing to remember about the bible is that it wasn't written by one person. It was written by dozens of authors over hundreds of years. What does that mean? It means each one of them wrote in his or her own way, and for a different audience. So its quite possible, and quite likely, that parts of the bible are historically factual. But it is also quite likely that parts of it are more metaphorical than factual, where the lesson of the story was more important than recording the truthful events. And then there are parts of the bible that can be proven to not be historically factual at all.
The truth of the matter however is that whether or not the events of the bible literally happened as they were described shouldn't matter. When one is looking at the bible as a religious document what's important should be the message it tells in the stories, not whether or not those stories ever actually happened. And when one is looking at any book as historically accurate you most always compare to other sources. To trust one source and only one source when it comes to history is just a bad idea. And when it comes to biblical stories, there quite often is no other source, so to use the bible as a basis for the truth of history would not be a good idea.