WHEN? Is the main question!
When is by far one of the biggest questions! A great flood whether local or global would have left a serious amount of damage in antiquity.
Five main questions have to be considered as we walk down this path are as follows …
1) Timelines of some major civilizations are well documented and as such which of any were missed or destroyed by such a catastrophe?
2) Also, what was the main purpose of the deluge?
3) Local or Global?
4) How long was the great deluge?
5) How many survived?
So lets start with number 1 : "When" was the time of the deluge. In most translation of the bible. ( Using the Masoretic Text aka MT ) Some biblical scholars select the date as 2348 , 2350 , and 2472 BCE. This calculation is based on the genealogies from Adam to the flood. The Samarian Pentateuch ( aka SP ) places the deluge date at 0000 BCE. Yet the Greek Septuagint Text ( aka the LXX ) using the same timeline states the flood started at around 3298 BCE. Why the different dates you are asking yourself? Simply put, the length of time of life for the early post flood and some pre-flood people are not the same.
Henry B. Smith Jr., Associates for Biblical Research
Many biblical scholars who interpret the genealogies of Genesis 5 and 11 as yielding a continuous chronology from Adam to Abraham claim the Hebrew Masoretic Text (MT) preserves the original begetting ages for the patriarchs. The MT’s total for this period is 2008 years. This was established by the seventeenth century Irish Bishop James Ussher and has been accepted among many of the devout.
The Samaritan Pentateuch (SP) presents markedly different chronological data for each epoch, for a grand total of 2249 years.
Calculations derived from the primary manuscripts (MSS) of the Greek Septuagint (LXX) yield a chronology of 3394 years for this period, 1386 years greater than the MT.
The MT is classically represented by the Ussher chronology, which places creation at 4004 BC and the Flood at 2348 BC.
Figures from the LXX place creation at ca. 5554 BC and the Flood at 3298 BC.