The first inhabitants of the area confined themselves to the higher grounds as they were afraid to go onto the plains where there was so much flooding. Eventually, the more adventurous farmers realized that to take advantage of the fertile soil in the valley, they would have to devise methods for controlling the flooding. These farmers were the first to use dikes and ditches for diverting the floods.
About the year 4000 BC, the Summerians arrived in the valley. They built on the earlier developments and established intricate networks of canals, dikes, dams, reservoirs and drainage ditches.