Managing the Dove in the Middle Ages

Plan view of the laser scan data with timbers outlined in blue, water in the bypass channel in black

KRISTINA KRAWIEC describes how a diversion of the Dove uncovered fascinating clues about medieval river management

Archaeologists from CFA Archaeology Ltd and Trent and Peak Archaeology, in partnership with the Environment Agency (EA) and Stonbury, undertook an investigation of timbers within a palaeochannel and beneath a concrete cap of a weir of the River Dove, at Dovecliff on the Derbyshire/ Staffordshire border. The timbers were revealed during the construction of a temporary bypass channel which was excavated to divert the River Dove to allow the removal of the weir. This work was designed by EA to improve biodiversity and fish passage along the entire catchment. The initial area of excavation was located in the bypass channel which, due to severe winter flooding, had revealed a cluster of upright timbers. These timbers were densely packed forming a north-south aligned structure located within a palaeochannel visible in the LiDAR data. This represented a former course of the Dove, which had been the County boundary until 1902. Rangefinder radiocarbon dates suggested that parts of the structure dated to the late 13th to early 15th century AD. To facilitate the rapid recording of these timbers in an area that experienced substantial challenges with the water table, a terrestrial laser scan survey was carried out. This scan was able to capture the structure in three dimensions and also record the site context. The resulting data will form the main part of the archive as the majority of the timbers were left in situ. A subset of the timbers was removed which, due to their size, was undertaken using a mechanical excavator. This demonstrated that some of the mainly oak timbers were up to 5m long, representing a feat of late medieval engineering. All the upright timbers were sharpened to a point at one end. A small trench excavated in an undisturbed portion of the site demonstrated that these uprights were packed with natural brushwood to create a formidable barrier. During the removal of the concrete capping of the present-day weir, further upright and horizontal timbers were recorded. These showed several phases of building with the latest phase including the placement of spent crucible bases to form a layer of ‘rock armour’ over the timbers. Samples were recovered from the bypass channel and weir structures for dendrochronological (tree-ring) analysis. Early indications suggest that the majority of the timbers were felled between AD 1525-1550, with other groups of timbers demonstrating repair and migration of the structure to the south during the 16th and 17th centuries. It would seem that the bypass channel timbers represent an earlier form of weir and as the river migrated southwards, either by natural or manmade processes, the weir was extended until it reached its present position. Historical sources record the presence of a mill stream at the site in AD 1342 and by the 18th century this stream powered Clay Mill Forge, perhaps the source of the spent crucible bases for the weir ‘armour’. Other wooden structures of slightly later date are also recorded in the Dove valley, particularly the ‘kid weir’ (a stabilisation structure using bundles of brushwood) at Dove Bridge. This demonstrates the potential for the valley to preserve early examples of river management both within relict palaeochannels and beneath later structures. Further work is ongoing in relation to the brushwood packing, the river paleochannel sediments and the laser scanning data. It is hoped that the tree-ring analysis will also provide significant information relating to the maintenance of the weir and the exploitation of the timber resources from the surrounding landscape.