The evidentiary parameters we have with regard to the wine at Cana consist
entirely of the account in John. If we had a sample of the wine preserved,
we could run additional tests and see what its appearance was. However,
the report of those who observed it is that they were out of wine and that
the new stuff came out of a cistern of water. Thus, there was some
observational evidence that it was of miraculous origin. Jesus did not
hand over a bottle and say "I made it myself, miraculously" without
evidence.
In the case of Noah's flood, the Bible does not explicitly state that any
miracles were involved in its physical achievement (although the continuous
rain is unusual), nor is it explicit as to the geographic extent (given the
flexible usage of the words rendered earth, mountain, etc.). We do have
plenty of rocks and sediment to look at, and the evidence from them is that
no global flood has occurred and that the earth is about 4.5 billion years
old.
David C.