Evolution of a Floodplain Landscape: A Case Study of the Harnham Water Meadows at Salisbury, England

Abstract

Understanding the evolution of alluvial landscapes requires an appreciation of soils, geology, fluvial geomorphology and climate as well as ecology, history and archaeology. For bedwork water meadows systems, it is antecedent floodplain and channel morphologies that condition layout, yet these considerations are generally overlooked. This paper proposes a speculative developmental sequence for the Harnham water meadows at Salisbury from the late Pleistocene, including the construction of floated water meadows in the mid seventeenth century, on an established grazing marsh. It is argued that the 'island' formed at the split in the River Nadder at the confluence with the Avon (upon which the water meadows are situated) is a consequence of accelerated alluviation and channel pattern adjustment to the imposed sedimentary load. Sediment loading from arable agriculture was subsequently ameliorated by vegetation community establishment leading to stabilised river channel geometries that provide the basis for the present arrangement of channels, meadows and mills.