Since the people living during that period thought the world was flat, it's not totally unthinkable that there was a world flood.
That's only one of many errors and omissions of the stories in the bible. There's not much scientific evidence for these geological conclusions based on the bible.
What people wish to believe must be based totally on faith. Trying to find any consistency or outside record of the events of the bible cannot be found. It takes much imagination to rationalize all the errors, omissions, and contradiction in the bible.
With millions of members of the christian faith, it's a common human "weakness." I'm not sure whether they believe "god is love," or they fear the rath of god. That they are able to reconcile that contradiction in their minds is a mystery for an unbeliever like me.