Thanks George for this valuable information.
Another interesting source seems to me History Stack Exchange.
I think one can summarize the available archaeological evidence as follows:
Sumer experienced large and destructive floods. The possibility that there is a destructive local flood in southern Mesopotamia between 3100 and 2750 BC cannot be excluded. In particular “the city of Ur did experience a dramatic flood around 3100 BC…The clay deposits found by Woolley were 3.75 meter thick. This is to say that post flood at least (likely much more) 3.75 meters of sediment were found in the area. For that much sediment to be laid down you could expect that said flood consisted of a lot of water.” This flood fits rather well with my theory (see previous postings in this thread).
One could object that in this Ur-flood “no archaeological evidence of flood residue, of the same time period, was found just 23 kilometers (12 kilometers depending on source) from the city of Ur in the Sumerian city of Eridu.” [see History Stack Exchange].
However the question arises: Why a “dramatic flood” in Ur did not affect Eridu?
Apparently we are here in front of a paradox which has not yet been solved. Further archeological and geological work is needed to clarify how flooding may have occurred in this Hammar Marshes region. But in any case the evidence we already have speaks in favor of the region around the first Sumerian cities as location for a possible historical event behind the story of Noah’s Flood.