Inundation by Flood Water from the Nile - Egypt
Before the Dynastic period in Egypt Kingdoms of the North and of the South were established in the Valley and the Delta of the Nile, and even before that there is evidence of a distinctively Egyptian civilization from end to end of the Valley, and this again was preceded by a definite culture - the Badarian. According to Prof. Childe the latter stage was reached between 6,000 and 5,000 BC. To the Nile with its two seasons of flood and sparsest flow Egypt owes its fertility, and on its banks settled civilizations arose in very early times.
From Wonders of the Past