Exploring Kent's Past

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Monument details

Summary

The Knelle Dam is an earth bank, some 2 - 3 m in height. It runs 2.7 km across the Rother valley from the Isle of Oxney on the Kent (north) side to the Sussex (south) side of the valley. It was built of local clay, for one purpose, and after three centuries became used for a different one. Both were essential in their own time for exclusion of the sea and the drainage of the valley. It is still today essential in controlling annual winter floods.

Monument Types

• FLOOD DEFENCES (Medieval to Unknown - 1332 AD?)

Full description

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Coastal marshes by definition lie below the level of the higher tides. Those marshes are therefore liable to flooding by water coming both from the sea and from land sources. At the west end of the Isle of Oxney, several other valleys converge into the Rother valley, bringing additional water to this area. Additional problems were caused by the fact that the river could flow either north or south of that island.

The thirteenth century is well known as an exceptionally stormy period. Very heavy rainfall lasted long periods, right through some of the summers, and on the coast by 1290 storms had broken down a shingle bank previously across the present Rye Bay, allowing the sea tides to flow right up the Rother valley as far as Bodiam. Marshland which had previously been valuable as summer pastures to provide food for an increasing population was no longer available.

By 1330 the flooding had become worse, and in 1332 two local landowners, Isabella Aucher who lived near Newenden on the Kent side, and Geoffrey de Knelle who lived in Sussex, petitioned the king for permission to make a wall at a place called Knellesflete. This was granted, and in the next few years the Knelle Dam was built where it now remains.

The Dam thus diverted the river waters and numerous tides round the north side of Oxney, There it promoted harbours at Maytham, Small Hythe, Reading Street and Appledore. These were small but of national importance to Henry V in 1415 and even Henry VII in 1517.

However, the sea deposited large quantities of sand and silt in the valley, and thus it retreated. By mid 1500s the channel was so silted it had ceased to be useful for land drainage. and much land was once again under land water.

In about 1600 the Knelle Dam broke, giving way suddenly and two men were drowned in the resulting floods.

The men of Wittersham Level, which had apparently remained relatively dry, demanded that the Dam be repaired. So not until 1635 was the Knelle Dam officially cut through, in three places, to let the Rother and various smaller channels drain along and then south towards Rye. The sea continued to break in and flow up the valleys from time to time.
(1,2,3)

<1> Ashford Borough Council, 2017, Ashford Heritage Strategy (Bibliographic reference). SKE51626.

<2> Jill Eddison, 2000, Romney Marsh, survival on a Frontier (Bibliographic reference). SKE51637.

<3> Archaeologia Cantiana, 1985, Developments in the lower Rother valleys up to 1600 (Article in serial). SKE51638.

Sources and further reading