The Noahide Flood

[Anomalocaris]

I'd think alot smaller than everest.  Enough to convince an observer that a localized or regional flood was global.  Nepalese comparables are about a lake draining, not filling up - just as a bit of trivia.  

Any flood proposal is some elevation boundary defined portion of the volume of the surface of a sphere which is, for the most part, smoother than a cue ball, plus the water holding capacity of it's soils and subsurface features, plus the rate of drain through irregular or open elevation boundaries.

The minimum depth of Noachian flood required to produce such effects as would be observable by Noah may be defined by the height of mt Ararat, which is 16,500 feet above MSL.

If the flood is any shallower Noah wouldn’t need to wait for the flood water to recede to ground the ark on the slopes of Ararat.

The mean height of all land on earth above MSL is not exactly negligible.   It’s actually about 1/10 height of mt Everest or just over 1/5 the height of Mt Ararat.   If the earth is flooded to the height of Mt Ararat then the lumpiness of land would account for about 6-7% of total volume of required flood water.    That’s a error 2 orders of magnitude bigger than the error introduced by treating the total volume of flood water as a thin shell that ignores the fact that each additional foot of depth accounts for a slightly larger incremental volume.