Early civilizations in the ancient world, both in Egypt and Mesopotamia, depended upon the rivers of those areas to irrigate their crops; it was not uncommon for there to be a drought during the summer months. As time progressed, however, men learned to build reservoirs to contain water during the rainy months, this would supply the much needed water during the dry period. Prior to the time of reservoirs, however, men depended heavily on the rain fall. Too little rain meant draught and famine; too much rain resulted in flooding. Floods were viewed to be a judgment of the gods and subsequently became the focus of many stories and myths.

In the Bible Noah is supposed to survived a great flood. This story may have originated in Babylon, since Abraham came out of Ur (Gen.11:31).The Babylonians had a story about a man who survived a great flood for his righteousness, Utnapishtun. This story predates the life of Moses. If one were to compare the two stories, one would find many similarities though they are two completely different stories. Details such as the size of the arc and length of time differ, yet many similarities can be found. A portion of the Gilamesh epic would better demonstrate this statement:

I looked for land in vain, but fourteen leagues distant there appeared a mountain and there the boat grounded; on the mountain of Nisir the boat held fast, she held fast and did not budge. One day she held, and a second day on the mountain of Nisir she held fast and did not budge. A third day, and a fourth day she held fast on the mountain and did not budge; a fifth day and a sixth-day she held fast on the mountain.  When the seventh day dawned I loosed a dove and let her go.  She flew away, but finding no resting place she returned. I loosed a raven, she saw that the waters had abated, she ate, she flew around, she cawed, but she did not come back. Then I threw everything open to the four winds, I made a sacrifice and poured a libation on the mountain top.(1)

Archaeologists such as Leonard Wooley have excavated many of the ancient cities along the Tigris and Euphrates rivers. In the city of Ur, from which Abraham came, was found to be buried beneath ten feet of silt. The Encyclopedia Amaricana reports:

Yet in only two of the five pits that Wooley dug to virgin soil did he find the "flood"  layer. This evidence suggests that the flood in question did not cover the whole city; and we know that it made no break in the community of culture there.

Other cities in the Mesopotamian river valleys, notably Kish, Fara, and Nineveh, also show flood layers, though none of them can be closely in time. On the other hand, the excavations have found no such layer in Gilgamesh's own city of Erech (Warka). In other words, the Mesopotamian "flood" evidence is that of purely local inundations of the Tigris and Euphrates.(2)

Since there is no archaeological evidence of a world wide flood, it is most likely that the flood story of the Bible was told to relate moral injustices of a particular geographical area (presumably the city of Ur).

We need to understand that it was common for one culture to borrow from another, such as the Greeks borrowed much of their basic ideas from the Babylonians, Syrians, and Egyptians, and then expounded upon them. For example The Encyclopaedia Britanniaca states: 

Io, of Greek mythology, daughter of Inachus, the river god of Argos. Under the name of Callithyia, Io was regarded as the first priestess of Hera, the wife of Zeus. Zeus fell in love with her and, to protect her from the wrath of Hera, changed her into a white heifer and sent Argus Panoptes ("the All-Seeing") to watch her. Zeus thereupon sent the god Hermes, who lulled Argus to sleep and killed him. Hera then sent a gadfly to bother Io, who therefore wandered all over the earth, crossed the Ionian Sea, swam the strait that was thereafter know as the Bosporus (meaning Ox-Ford), and at last reached Egypt, where she was restored to her original form and became the mother of Epaphus.

 Io was thus identified with the Egyptian goddess Isis, and Epaphus with Apis, the sacred bull. Epaphus was said to have been carried off by order of Hera to Byblos in Syria, where he was found again by Io. This part of the legend connects Io with the Syrian goddess Astarte. Both the Egyptian and the Syrian parts, in fact, reflect interchange with the East and the identification of foreign with Greek gods.(3)

Understanding this exchange of basic concepts by ancient civilizations, we can consider that the Hebrews (notably Moses) borrowed from the Babylonians (see: Ancient Sumerians Conclusion). Bible scholars and religious leaders of later times likewise borrowed from these pre-existing concepts.