Shushtar Bridge was made of carved cubic sandstones and the main road with the same materials with the thickness of about one meter.
Roggen saw a part of piles, made of rubble stones, bricks and concrete. The width of weir of the bridge with a height of three to four meters above water level in dry season was a little more than the width of piles. The weir, which extended throughout the cross section of the river besides raising water level, fastening the piles together.
There were different arches over the bridge in order to increase the capacity of the river cross section during overflowing.
The materials used had high quality and the places they had extracted the sandstone is still visible and can be seen the marks of peck stroke.
Shape of piles and their dimensions
All the piles of old bridges had rectangular cross section with a sharp edge opposite to the river water current. At first it looks like the dimensions of piles, are over design, but if we realize the pressure and water strokes during overflowing, we can understand the importance of this kind of design. The thickness of piles is between five to 6.40 meters and the length is a little more than the width of the road and some how less than the width of the weir bridge.
There were some small arches on the spaces between piles and the main arches (as mentioned before) in order to increase the capacity of river cross section during overflowing.
The distance between center to center of two piles were about 13 to 14 meters so the internal diameter of large arches were two times the width of their piles.
The width of the weir bridge was one or two meters longer than the length of the piles and it was eight to 12 meters. The advantage of Shushtar Bridge respect to two other important bridges in Khuzestan was its longitudinal axis, which was not in a straight line. Roggen guessed the builder tried to put the piles of the bridge on natural rocks, so the axes of bridge got out of line. The original Shushtar Weir Bridge had 40 gates and it was about 500 meters long.
The Karun River was divided into two branches at the north of Shushtar. The eastern branch called, Gargar River and the Western one Shatit. These two branches joined together in Gheer Dam site again. That is why Shushtar and the land between these two rivers became as a peninsula.
There were two tunnels under Salasel Castle about 300 meters upstream of Shushtar Bridge which joined together, 100 meters downstream and formed Darian Canal.
The other name of this canal was Mino-Ab or Darabian. It was said, this canal had been excavated by the order of Darius the Great. The width of both tunnels was three to 405 meters and on one side there was a passageway. They are all destroyed by now. By the way, the water intake bed of the tunnels was constructed as a weir. The height of the crest was about water level during dry season.
Darian Canal was divided into two branches in Band-e-Khak. The main branch went towards south, after 33km, it joined to Shatit River in Arab Hassan Weir. The topography between Shatit and Gargar Rivers were somehow that Darian Canal passed through ridges of the hills. So it was very easy to irrigate the land between these two rivers. There were many other irrigation canals passed through high lands. The second branch of Darian Canal after passing through Lashgar Bridge poured into Gargar River.
There was a dam in Band-e-Khak which store main portion of Darian Canal water discharge in original branch, because the eastern branch of Darian had 15 meters head.
Apparently they had constructed three more weirs to reduce the velocity of water. Roggen emphasized that Darian Canal had been older than the other water structures which were constructed during Shapur the First (240-270 CE), because the max. height of weir in Darian was the same as water level during dry season. Roggen concluded that there must have been a dam for taking water before constructing the Shapur Bridge and perhaps Shapur the First repaired the weir or he had completely changed it.
The above is a lightly edited version of part of a chapter entitled “River Controlling and The Method of Distributing and Using Water Power in Ancient Iran” from a book entitled, “
Water and Irrigation Techniques in Ancient Iran”, written by Gholam Reza Kuros and Majid Labbaf Khaneiki, published by Iranian National Committee on Irrigation and Drainage.