The Mere Bank and flanking ditches

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 Mere Bank and its flanking ditches exists as an identified medieval flood defence which may have earlier, Roman, origins. It acted as a barrier to reclaim part of the wetlands of the Avon levels, a landscape which was subject to increased industrial development in the 19th century. The present Mere Bank has been provisionally dated to the 12th-13th century by partial excavation. Documentary sources would appear to support this date. Part of its length survives as a recognisable feature within the landscape, which is rare nationally and particularly within the Avon and North Somerset Levels.

Details

The monument comprises a 1.15km length of the Mere Bank, a linear flood defence of probable medieval date, and its flanking ditches. It is located within an industrial area of Avonmouth, to the north west of the M5 motorway. Although it may have Roman origins the present Mere Bank relates to medieval (probably 12th or 13th century) attempts to protect an area of land from sea and river inundation. To the south west of the bank, the present estuary of the River Avon is 2.5km away, and to the north west, the Severn Estuary is within 1.25km of the northern end of the monument. The monument comprises a low bank (the Mere Bank) with two flanking ditches. The ditch on the north eastern side of the bank, the Mere Bank Rhine, measures between 1m-3m wide. To the south west, the bank is flanked by a narrower field ditch boundary. The Bank itself is 3m-5m wide and the whole monument is approximately 9m in width. The top of the Mere Bank is only about 0.25m above the natural ground level on its south western side, but it stands about 1.3m above the base of the flanking south west ditch and 1.9m above the base of the Mere Bank Rhine on its north east side. The Mere Bank, noted from a 19th century map, extended in a straight line from the foot of the 10m contour north west of Lawrence Weston to the former Hoar Gout at ST52468017. From here the bank is not traceable, but the rhine and ditch both flank a road heading northwards to the Salt Rhine at Mitchell's Gout at ST52648105. This coastal lane is probably a continuation of the course of the bank. This boundary would have served to protect the open fields of Great Madam and Little Madam, which were a large expanse of common ground until their enclosure in 1811. Much of the northern extent of the flood defence has been lost to industrial development. The bank is known from a partial excavation to have been constructed of a series of layers of clay loam and silty clay, below which lie regular silt deposits from flooding episodes. Pottery of the 12th-13th centuries has been found beneath the bank, but the origins of the bank may date to the period of a land reclamation process started during the Romano-British occupation. All modern fences, posts and road surfaces are excluded from the scheduling although the ground beneath all these features 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:

27988

Legacy System:

RSM

Sources

Books and journals
Glamorgan Gwent Archaeological Trust Ltd, , Archaeology of the Second Severn Crossing, (1992), 84-86

Other
Avon County Council Planning Dept., County Series 1:2500,

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