Balt Moor Wall

Reasons for Designation

Roman and medieval flood defences were barriers designed to prevent the inundation of land by salt or freshwater floods, and to assist in the reclamation and drainage of large areas of low lying land. They normally survive as a low elongated earth bank with a ditch on the landward side. The banks were made of local clay or turf and were sometimes strengthened by internal wooden frameworks, wattling or stone facing. Regular repair of flood defences meant they often had a long life span of many hundred years with some medieval embankments still in use today. Unaltered examples, ie surviving medieval defences not subsequently reused in the post-medieval period, are comparatively rare, and Roman examples rarer still. Flood defences are one of a small number of Roman and medieval monuments to show the effects of man on water control. Their longevity and their influence on the layout and pattern of large areas of low lying land all contribute to their importance.

The Balt Moor Wall is a rare example of medieval engineering. It is well preserved having been encased in stone in the post-medieval period, overlain by a metalled road surface for part of its length, and more recently protected by a clay embankment for the remainder of its length. It is known from part excavation to contain archaeological information and environmental evidence relating to the medieval causeway all of which is complemented by contemporary documentary evidence. It is associated with the nearby burhs of Athelney and Lyng, well documented Saxon sites which played an important part in the early history of England.

Details

The monument includes a section of medieval causeway known as Balt Moor Wall located on the Somerset Levels north west of the River Tone. The Balt Moor Wall was originally constructed as a causeway and subsequently utilised as a flood defence barrier. It survives for approximately 550m as a raised embankment above the surrounding low lying ground between East Lyng to the west and Athelney Hill to the east. Broadly aligned from east to west the causeway begins at the eastern edge of East Lyng at the junction of Cutts Road with New Road. The western section of approximately 300m is overlain by Cutts Road and here its north face rises steeply to 4m high above ground level. The south side of the causeway is overlain by a gently south sloping bank with an average width of 8m which runs parallel with the road for approximately 180m. The causeway and road divide at about 15m south east of Moorside, where the road turns sharply to the south and then progresses eastwards. The raised causeway continues to the north east for approximately 50m before curving to the east and gradually petering out below the slope of the west side of Athelney Hill. This section of causeway varies in width between 6m and 10m wide and in height between 1.7m and 2m high. An investigation programme into the stability of Balt Moor Wall carried out in 1996 confirmed the medieval phase of the causeway's construction which is formed by an earthen clay bank of at least 6m wide at its base and 1.7m high above the surrounding medieval ground level. Pottery recovered during the investigation provided a 14th or 15th century date. The earliest known medieval mention of the causeway comes from a charter signed by King Stephen between 1135 and 1154 in which he refers to work carried out by the monks of Athelney Abbey as part of land drainage and reclamation of the levels and moors. The monument may be even earlier however. Balt Moor Wall causeway links the fortified burhs of Athelney, a stronghold established by King Alfred in 878 and Lyng, which is referred to in the Burghal Hideage, a list of fortified burhs which dates from the early 10th century. Contemporary documents refer to a causeway or bridge which connects the two burhs. A course of laid stone rubble located at 3.2m below the present ground level in the 1996 investigation may be the remains of the Saxon causeway or bridge to which these documents refer. Environmental samples taken from under the medieval bank in 1998 were of a 5th to 7th century date which substantiates the case for an earlier Saxon structure. The 1996 investigation also revealed that the medieval bank had later been clad with roughly coursed stonework which appears from the different bonding mortars used to have been laid in two separate phases. These two phases almost certainly relate to documentary records which refer to work on the causeway: firstly, in 1675 when an order for the bank to be faced with stone was recorded in the Quarter Session Records; and secondly in 1880 when the causeway was encased in masonry at the direction of the Somerset Drainage Commissioners. Included in the scheduling is the clay embankment which overlies the eastern end of the causeway for approximately 120m which was constructed as an emergency flood control measure in 1994 and acts as a protective barrier. All fencing, gates and gateposts, road surfaces, roadside bollards, kerbing and hard-standing, telegraph poles, sluice gates and all post-medieval structures not directly related in offering protection to the core of the medieval wall are excluded from the scheduling, although the ground beneath these features however is included.

MAP EXTRACT The site of the monument is shown on the attached map extract.

Legacy

The contents of this record have been generated from a legacy data system.

Legacy System number:

33709

Legacy System:

RSM

Sources

Books and journals
Collings, et al, Baltmoor Wall, (1996)

Other
Burden, R, Interim summary on archaeological recording at Balt Moor Wall, 1998,

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