Or in other words, sure - a local flood would very easily expand to be a year-long disaster that only saved one pious family and drowned the rest in about four generations.
On the other hand, it could just be a stupid story that doesn't make any practical sense intended as an object lesson and taken way too seriously by god-bothering idiots who can't do basic math.
It could aso be a combination of both, or a combination of 2 or more stories combined, by retelling of both stories with the common embellishment added by each retelling until the time the story is compiled and written for posterity at which time the original story and the purpose of the telling becomes totally lost.
There is no better love between 2 people than mutual respect for each other WT Young, 2002
Who gave anyone the authority to call me an authority on anything. WT Young, 1969
Since Evolution is only ~90% correct it should be thrown out and replaced by Creation which has even a lower % of correctness. W T Young, 2008