Early civilizations were located on rivers because rivers contain fresh water needed by humans as an essential of life and for washing. Further, transportation for any long distance was so much easier on boats or rafts than by foot or on horseback or wagon. Generally, the soil in the vicinity of a river is better suited to agriculture than at higher elevations because rich topsoil tends to erode downhill toward the river bed, and the water from the river is more easily available to the farm animal