The symbolic force of the story of Noah's Flood for the literature that we are reading operates on two main levels.
1. The story is directly relevant to "The Miller's Tale." Nicholas tells John that a rain greater than Noah's Flood will destroy the world in less than an hour! (p. 109, line l405ff). John, who prides himself on being a pious man, misunderstands the lesson of Noah's flood, and so believes Nicholas's fake story. Why does John not know the true meaning of the story of Noah's flood or why does he misinterpret the biblical story?
2. The story of Noah's Flood is also relevant indirectly to "The Miller's Tale." In persuading John to accept his plan, Nicholas seems to refer directly to the versions of the flood story found in medieval drama cycles, such as the Chester Play of Noah's Flood. Nicholas reminds John that Noah had a hard time getting his wife on board the ark. Nicholas even speculates that Mrs. Noah had her own boat! (p. 110, line 430ff). He uses this point to persuade John to lie in a separate boat from Alison. This alerts us to the fact that the wives in these two works-- "The Miller's Tale" and the Chester Play of Noah--may both be married to men who build things with wood, but as women they are very different. John, Nicholas, and the other characters in this story clearly know the medieval drama. (Absalom, for instance, imitates Herod, another well known character from these plays.) So we can expect Chaucer's readers to pick up on the differences between the wives. How can understanding this difference help you interpret "The Miller's Tale"?