Using Shuttle Radar Topography to map ancient water channels in Mesopotamia

The literate and city-based polities of Sumer and Akkad in southern Iraq are widely regarded as among the earliest examples of successful city-based civilisation, and great strides have been made in understanding their archaeology, economy, literature and social conditions. Fundamental to the development of these societies was a network of water channels, which provided irrigation for the cultivation of food crops, and a means of transport of goods from city to city. Irrigation technology and access to a network of channels has therefore been recognised as a key component of the so-called ‘Mesopotamian advantage’ (Algaze 2001). The seemingly flat terrain of the Mesopotamian lowlands is drained by the Tigris and Euphrates rivers, which form a system of branching and locally meandering channels. Deposition of fine sand, silt and clay both within and alongside the channels results in the aggradation of levees which gradually raise the rivers until they flow several metres above plain level on low ridges (Buringh 1957). The excavation of canals to divert irrigation water from the main river channels towards fields also results in levees. Formation processes are similar to those of riverine levees, but in addition, channel excavation and cleaning operations result in the up-cast of clean-out banks alongside. As a result of these processes, both natural and artificial channels become raised above plain level to form levees up to 5m or so in height, and up to several kilometres in width. With a gentle gradient of c . 1: 10 000 to 1:15 000 towards the head of the Gulf, the plains appear virtually flat, and surface elevation appears to reflect the pattern of levee development. The excavation of new canals as well as the natural branching process of rivers has resulted in an immensely complicated network of natural, artificial and hybrid channels across the plains.