Band-e Kaisar made from material Roman concrete
Construction
Shushtar lies on a rocky plateau above the Karun, Iran's most effluent river. An early dam, built by the Sassanids to divert water for the town and its extensive irrigable hinterland, did not work properly. The irrigation scheme put into effect after the arrival of the Roman labour force included three steps: First, the river was redirected towards the Ab-i Gargar, a channel which branches off the Karun at a point upstream of the dam construction site, rejoining the main river some 50 km south; the island it forms, called Mianâb ("Paradise"), is known for its orchard plantations.Then, the Band-e Kaisar was built across the dried-up riverbed, with its foundations following a winding course in search for solid strata of sandstone. As the water flowed permanently over the top, the hydraulic structure conforms to the definition of a weir rather than a dam. Estimations of the raised water level range from a few feet to 7–10 m, but was most likely in the order of 3–4 m, which was enough to supply water for the irrigation conduits on both banks during the dry season. Despite its modest height, the weir wall was quite thick (9–10 m) to accommodate the arcaded superstructure.On top of the weir, a roadway originally supported by at least forty arches ran along its entire length of around 500 m. The pointed arches which visually dominate the present-day structure, or rather its remains, are testimony to numerous reconstruction and maintenance works executed in Islamic times. The typical clear span of the Pol-e Kaisar was between 6.6 and 9 m.The piers, protected on their upstream side by pointed cutwaters, were of rectangular shape and pierced by high-set floodways; their considerable thickness of 5 to 6.4 m restricted the waterway by nearly one-half. By comparison, pier thicknesses of Roman bridges located within the empire’s frontiers commonly made up one-fourth of the length of the bridge and did not exceed a maximum of one-third.The facing of the piers and the foundation consists of cut sandstone blocks bonded by mortar and joined by iron clamps; the interior was filled with Roman concrete, a building technique also observed in the Pa-i-pol bridge. On the upstream face, the river-bed was paved with large stone slabs, probably to prevent the current from undermining the dam base. One former Persian name of the dam, "Shadirwan", derives from this paving.Finally, another smaller barrage, the Band-e Mizan, whose construction may postdate the Roman works, was erected upstream to control the flow of water into the Ab-i Gargar canal. The time it took the Roman labour force to complete the ancient Shushtar hydraulic complex is variously reported as spanning three to seven years.The site has been referred to as "a masterpiece of creative genius" by UNESCO. Along with the hydraulic works, it also includes Selastel Castle and a tower for water level measurement, as well as a series of water mills.
constructed from material fabricated from material composed of material formed from material manufactured from material