"Alluvial" describes rich, fertile soil deposited by rivers and streams. The alluvial desert is one created from large rivers leaving behind their rich, fertile sediments. The world's first civilization, which was Mesopotamia, developed in this region in between the Tigris and Euphrates Rivers. At one time, it was believed that they began food production here because of the rich soil. Even so, it was necessary for them to invent irrigation to successfully farm this alluvial desert.