Without going into too great of detail regarding Source Theory, the two main sources of the Genesis Flood story are known as the J-source and the P-Source. The J-source is thought to have been written about the 10th Century BC. The J-source refers to God by Name – YHWH is God’s Name (this is a real name like JOHN or MARY). It was considered so sacred that it was never pronounced. Many English Bibles do not use YHWH for the Name of the Lord, but will substitute for His Name the words in all capital letters the LORD, or perhaps LORD GOD. So when you are reading Genesis 6-9 and you see the LORD know you are probably reading the J-source author. The God of the J-source is very personal and active in history. The description of the LORD is very anthropomorphic (meaning God behaves much like a human being). The LORD frequently makes promises and also will curse the disobedient. The J-source is also said to have written the second story of creation found in Genesis chapter 2 beginning with verse :4.
Another source identified by scholars is called the P-source. The P-source wrote about 550BC perhaps 400 years after the J-source. (the stories may be much older than this, 550BC is simply when scholars believe the oral stories were put into their final written form). The P-source is very concerned with Israel’s priest class and the temple. The P-sources never uses God’s name but always refers to God by the generic word “God” which is not a name but word for the divine being. The God of the P-source is far more transcendent and distant from humanity than the God described in the J-Source. This God gives many blessings for increase and fruitfulness and likes to offer both genealogies and covenants. The P-source is said also to have written the first creation account in Genesis 1:1-2:3.
The final editor who brought these two sets of stories together is also thought by scholars to have worked about the same time as the P-source. Some scholars think the P-source may also have been the final editor of the bible that we now accept as authoritative.
As you are reading these chapters take note whether the verses are referring to God as the LORD (LORD GOD) or as God. This will be one clue to help distinguish the two stories. Remember you don’t have to choose between the two stories. Those who were inspired by God to formulate our scriptures saw value in both stories and attempted to weave them together while leaving in some of the discrepancies. This may in fact tell us that the final editor inspired by God did not in fact think that a literal reading of the text which harmonizes every detail is in fact the best way to understand the story of the flood, nor the way to get the most out of the scriptural lesson. The two stories together add richness and depth to the entire narrative. And if we get past the troubling literal inconsistencies we realize there is a tremendous consistency in truth – the truth about humanity, the truth about God the LORD, and the truth about our relationship to God our LORD. Our conception of God is enriched by the very different ways that God is portrayed.
The two stories do not contradict the main point that God both attempts to rid the world of sin and to respect the free will of humanity. God does not abandon humanity to its own fate but endeavors to continue to influence events in the world for the salvation of the world. It is a story of God’s undying and steadfast love for His very wicked and rebellious creatures. It is a story which develops a major theme of scripture – God is a saving God, and God will rescue His servants even if they are but a tiny remnant on earth. God commits Himself in the story to working out His plan for His creation through the people He will save from the flood. But God also acknowledges with a sorrowful heart that His beloved humans have wickedness in their hearts from when they are young. This will be as true of the people God saves in the ark as of those destroyed in the flood. God saves them anyway as He is intent on working out His purposes in and through humanity.
So as you are reading through the chapter texts themselves (NOT when you are stopping every few verses to read my reflections but just when you are reading the Biblical text itself), try identifying those sections belonging to the J-source and to the P-source. If you feel that the verses in these chapters sometimes seem chronologically out of sync – like it moves back and forth in time, that is probably due to places in the text where the story shifts from P to J and back again. Or if you notice contradictions in details (7 pairs of animals as versus 2 pairs of animals, how many days the flood lasts, and so on), you probably are seeing the differences in the details of the two stories which give support to the Source Theory hypothesis.