A friend who does know Hebrew writes in response to your comments:
Sometimes we get a little too "Greek" (westernized) in interpreting Hebrew
(a more eastern style language). We want one solid meaning for each word,
but Hebrew isn't always that way. The word eretz means ground, or more
often country, or sometimes earth, depending on context. Its meaning in
Genesis 6-7 is clearly global by the context -- see Richard Davidson's
excellent article on the universality of the Flood in Origins 22(2)58-73.
Some of the most obvious clues from words in Genesis 6-8 include:
1. ha eretz used 46x in Gen 6-9 without any genitive of limitation
2. "upon the face of all the earth" (7:3; 8:9) is global, as in 1:29
and "face of the ground" 5x, in paralles with the above (cf 2:6)
3. "all flesh" 12x
("all" can express less than totality if context demands, but
with no article or posessive it indicates totality)
and "every living thing of all flesh" ... "all existence"
4. "under the whole heaven (7:19) has global meaning
as in Deut 4:19, Job 28:24, 41:11, ...
5. "all the fountains of the great deep" (7:11, 8:2) refers to the
world ocean, as in Gen 1:2 and Ps 104:6
The Hebrew word Mabbul, translated Flood, is different from other Hebrew
words for flood. It refers exclusively to this worldwide water catastrophe,
and is not used to describe local flooding.
Richard Davidson also points out
-- the major themes of Genesis 1-11 -- creation, the fall, the plan
of redemption, the spread of sin, the flood, are all global in scope.
-- the purpose given for bringing the flood (Genesis 6:7)
necessitates more than a local flood
-- the genealogical lines indicate that just as Adam was
progenitor of all pre-flood humanity, so Noah was father of all post-flood
peoples. From his descendents "the nations spread abroad on the face of
the earth after the flood" (Gen 10:32) and the same inclusive diving
blessing to be fruitful and multiply is given to Noah's family, as it was
to the first pair (Gen 1:28, 9:1)
-- striking extra-biblical evidence that all human races, not just
those in the Middle East, retain memory of the universal flood is found in
the amazing prevalence of ancient flood stories all over the world (he
gives references)
-- God's covenant (Gen 9:9-10), with the rainbow sign (Gen 9:12-17)
includes the whole earth (Gen 9:13-17)
also note: The integrity of God in keeping His promise is wrapped up in the
global extent of the Flood. God's promise not to bring another worldwide
flood is fulfilled; but if the flood was local, God's integrity would be
questioned each time a local flood occurred!
-- the enormous size of the ark would be unnecessary for a local flood and
there would be no necessity of the ark at all if there were no other escape
for air-breathing land animals from the overflowing waters.
-- the covering of "all the high mountains" is not possible in a
local flood, because water seeks its own level across the surface of the
globe; to cover even one truely high mountain would require a water level
that high all over the earth.
-- the duration of the flood does not make sesnse with local flooding
--New Testament passages concerning the Flood use global language:
Matt. 24:39 "swept them all away"
Luke 17:27 "destroyed them all"
2Peter 2:5 "did not spare the anceint world...when He brought a
flood upon the world of the ungodly."
1Peter 3:20 "few,that is eight persons,were saved through
water
Hebrews 11;7 "Noah condemned the world..."
"we have the unequivocal corroboration of the New Testament that the
destruction of the human race at the time of the flood was total..."
Archer 1985, p 208
Also, NT typology assumes and depends upon not only the historicity but
also the universality of the Flood to theologially argue for an imminent
world-wide judgment by fire (2 Peter 3:6-7)