Geology Site Account
Dagenham Breach, DAGENHAM, London Borough of Dagenham, TQ491827, Historical site only
Historical site only
In October 1707 an exceptional high tide swept away 14 feet of the Thames river embankment and flooded much of Dagenham Marshes. Daniel Defoe, writing about the spot a few years later, said that “the famous breach, made by an inundation of the Thames, was so great, as that it laid near 5,000 acres of land under water”. Such was the severity of the breach that it took 13 years before it was finally repaired. The breach eventually reached a width of almost 400 feet and tidal currents through it built up a sandbank in the Thames which became a threat to shipping. The final closing of the breach was said to be one of the most difficult and most celebrated feats of early civil engineering.
Of interest to the geologist is the fact that the immense current of water resulted in the removal of the top layer of marsh clay and the exposure of the underlying peat which contained large logs and mammal remains. A written record of this site was made in 1712 by Reverend William Dereham, Vicar of Upminster. He described the wood as “black and hard” and speculated that all the marshes alongside the Thames for several miles “are covered underneath with those subterraneous trees”. This was a reasonable assumption as beds “crowded with the trunks of trees” had previously been discovered at several places in the vicinity, in one case a trunk “nearly 50 feet long” had been found.
We now know that this was part of a submerged forest, about 6,000 years old which is currently exposed on the Thames foreshore at Rainham Marsh, at Purfleet and at Erith on the other side of the river. The forest, consisting of fallen tree trunks, branches and roots, is of Neolithic age, a time when sea level was much lower. Following the end of glacial conditions some 10,000 years ago, alluvium (the marsh clay and silts with seams of sand and gravel) was laid down by the River Thames on its floodplain. Trees colonised the mud flats when there were minor temporary falls in sea level and were killed when sea level rose.
When the breach was eventually dammed it left behind a lake of some 55 acres which, in the 19th century, became a popular spot for anglers. James Thorne, in his Handbook to the Environs of London (1876) said that from 1826 onwards Elizabeth Fry, the famous prison reformer, spent her summers in a cottage by the lake “surrounded by trees, mostly willows, on an open space of lawn, with beds of reeds behind them, and on either side covering the river bank”. The lake still exists today although it is much reduced in size and almost completely surrounded by industrial development. A road nearby (next to Barking Power Station) is called Breach Lane.
Nicholas Crane, in his 2007 BBC television series ‘Great British Journeys’ located the exact point of the breach during his research into Defoe’s journey round Britain.
Geologist T.V. Holmes led an Essex Field Club field meeting to the area in July 1892 and described the geology of the district around Dagenham Breach in a paper in the Essex Naturalist.
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Reference: Dereham 1712, Whitaker 1889 (p.463-465), Holmes 1892, Crane 2007.
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