Rethinking Offa’s Dyke as a Hydraulic Frontier Work

Abstract

Building upon a fresh interpretation of Wat’s Dyke as a component of an early medieval hydraulic frontier zone rather than primarily serving as a symbol of power, a fixed territorial border or a military stop-line (Williams 2021), here, I refine and apply this approach to its longer and better-known neighbour: Offa’s Dyke. This linear earthwork’s placement, alignments and landscape context are evaluated afresh using a simple but original comparative mapping methodology. First, on the local level, I show that Offa’s Dyke was carefully and strategically positioned to connect, overlook and block a range of watercourses and wetlands at key transverse and parallel crossing points, thus observing and choreographing mobility on multiple axes. Second, I address the regional scale, showing how Offa’s Dyke interacted with, and controlled, biaxial movement through and between water catchments parallel and transverse to the monument’s principal alignments. Both these arguments inform how the Dyke might have operated on the supra-regional scale, ‘from sea to sea’ and also ‘across the sea’, by controlling the estuarine and maritime zones of the Dee Estuary in the north and the Wye/Severn confluence to the south. Integrating military, territorial, socio-economic and ideological functionality and significance, Offa’s Dyke, like its shorter neighbour Wat’s Dyke (in an as-yet uncertain relationship), configured mobilities over land and water via its hydraulic dimensions and interactions. Together, the monuments can be reconsidered as elements of a multi-functional hydraulic frontier zone constructed by one or more rulers of the middle Anglo-Saxon kingdom of Mercia and operative both in times of peace and conflict.