Bronze Age bridges at Dorney
Excavations were done when Eton College wanted to build a rowing lake north of the River Thames in the parish of Dorney in South Buckinghamshire. It was known that there were some sites in the area from aerial photographs, so archaeologists had to go in and do some work.
Three sets of small-scale trenches were dug in 1987, 1990 and 1994. There were three seasons of large-scale excavations in 1995, 1996 and 1997 and another in 2000. Lots of archaeology was found, dating from the Mesolithic (9000 – 4000 BC) to the medieval period (1066-1539 AD). Because the sites were close to the River Thames, some of the archaeology was waterlogged. This meant that organic materials, such as wood, were well preserved.
The most important wooden finds from the site are the remains of a series of bridges that date to the Middle and Late Bronze Age and also the Iron Age. The bridges connect areas for grazing animals with settlement. At least six bridges were built between 1400 and 300 BC. The bridges crossed some earlier channels of the River Thames, which had silted up by the Roman period.
The bridges were repaired during their use and only replaced when they were too unstable to support humans, goods and animals. The construction was similar for all the bridges. Two parallel lines of oak posts were hammered into the riverbed and banks. The upright posts were connected by planks with holes at either end. The planks formed a base for planks laid between the two rows of uprights to form the walkway.
The first bridge excavated in 1995 was made up of two rows of large oak posts at the west end (numbered 3483) and two rows of smaller, paired posts further to the east (numbered 3484). The pairs of posts were about 3m apart and there was a gap of 2m between the rows for people and animals to walk down. A wattle panel, the surface of the bridge walkway, lay horizontally between the rows of posts. Pottery and human bone were found close to the bridge in the silt of the former river channel. The larger posts were radiocarbon dated. They dated to between 1520 and 1220 BC, the Middle Bronze Age. The smaller posts were later and dated to 770-390 BC, the Early Iron Age. In the 1996 excavations, several more large timbers were found on what was the riverbed. It was thought that the Middle Bronze Age bridge probably had gone right across the river but had collapsed and was later rebuilt.
The second timber structure was found further to the north-west in 1996. This was just a jetty or footbridge, as it was made of thinner stakes than the first structure. The stake rows were set only 1m apart, with 2m between the stakes. It was 10-15m long. Later on larger posts were driven into the channel and withies had been woven around them. There was also part of a wattle panel, possibly used between uprights, nearby. Part of a wooden plough, probably dating to the Early Iron Age, 700-400BC, was found nearby.
Four more bridges were found to the north-west of the bridge found in 1995, slightly upstream. Two of the bridges (numbers 7204 and 7205) were simple constructions of two lines of single posts. There were a few paired posts and it seemed as if the second post had probably been put in later as a repair. Some of the posts of bridge 7204 were forked at the top where a branch had come off the main timber. This would have acted as a support for a handrail. Some timbers from bridge 7205 on the east bank of the channel had been taken out when the bridge was no longer in use and probably reused somewhere else. There were lost of pieces of Middle Iron Age pottery around bridge 7205, as well as part of a human burial and some animal bones.
Bridge 7202 was a simple bridge made of two lines of single posts. Bridge 7201 was the most westerly bridge before the jetty described above. It had double posts all the way along its line, similar to bridge 3484. Early Iron Age pottery was also found next to one of the posts of this bridge. A trackway was built at a later date between the upright posts of bridge 7201. Large horizontal timbers were laid between the uprights and wattle hurdles or fencing was laid flat on top of them. It was built when the channel had mainly silted up and was therefore probably a ford across a shallow river.
The wood was preserved because it was found in waterlogged conditions, which are anaerobic. Anaerobic means there is no oxygen, which the bacteria that make wood and other organics materials decay cannot live without. The bridges are therefore very significant because very few of this date have been found and don’t normally survive.
The bridges seem to have been built across this channel to link the north bank of the river to the island of gravel between this ancient channel and the modern course of the Thames. Middle Bronze Age human and animal burials and Late Bronze Age to Middle Iron Age settlements have been found on the gravel island, suggesting it was an important site.
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