“But there is no geological evidence — zero, zip, nada — of a single world-wide flood in recent times which covered every mountain to the depth of 23 feet, and then somehow receded again to current levels.”
To say this you must first say to yourself evidence is only evidence if it agrees with your conclusions.
A truly intellectual approach is one which looks at both sides of a controversy, weighs the evidence, and then decides which is the more plausible.
Many scholarly books have been written on the flood. Start with “In the Beginning: Compelling Evidence for Creation and the Flood” by Walt Brown. Also see “The Genesis Flood” by Whitcomb and Morris.
Sorry, but scientifically speaking, there is no controversy, and there are not two sides to consider.
There is only scientific evidence and theory on the one side, and any number of non-scientific assertions -- mostly religion based -- which by scientific rule cannot be considered, except as coincidence may suggest correlations.
As I said before, the scientific evidence is chock-full of regional and world-wide catastrophes, from asteroid strikes to volcanic eruptions to outburst floods.
But none matches precisely the Bible's Noah story, and any "scholars" who claim otherwise are simply not scientific.
Indeed, I would ask you again to consider that the point of Noah's story is to show God's Promise that no such flood will ever happen again.
So think about this: does not science prove that God's Promise can be relied on?
In that sense doesn't science, once again, confirm the Bible?
;-)