Neither the flood or garden story is historical. Even if there was an actual singular flood that gave rise to the older Mesopotamian myths, Genesis 6-9 seems to come after, and these actual floods are nothing like what Genesis describes. It would have been very localized (e.g. Kish and Shuruppak) if it occurred.
David MacDonald: "The Mesopotamian strata, whether at Ur or at Kish and Suruppak, testify only to a local flood which clearly left behind survivors and significant cultural continuity. The Ur flood apparently did not even cover the entire mound of Ur.
. . . Flood events occurred with frequency throughout southern Mesopotamia, as the two separate early flood levels at Kish indicate. Even more so than the Ur flood, the flood levels at Kish and Shuruppak fail to fulfill the biblical or even the Mesopotamian literary descriptions. In the degree to which those descriptions are “rationalized,” any criteria for distinguishing between the biblical Flood and virtually any other flood disappear. The flood remains at Kish and Shuruppak are hardly imposing."
Genesis speaks of a universal flood. None of the evidence for any of these localized floods does the descriptions any justice whatsoever. There is no real evidence for the flood that Genesis describes even if localized:
A good article to look at: Was the Black Sea Catastrophically Flooded during the Holocene? – geological evidence and archaeological impacts. Valentina Yanko-Hombach, Peta Mudie and Allan S. Gilbert
For Genesis and the Garden story, this thread has a lot of info:
Adam has no more of a claim to historicity than Enkidu and Noah has no more claim to historicity than Utnapishtim.Genesis is recasting common ancient near eastern mythology to reflect Jewish monotheism.
Vinnie