RECLAMATION and settlement of wetlands in Roman Britain is generally associated with the fenlands of East Anglia, 1 where our knowledge of Romano-British occupation is being rapidly advanced. 2 In south-west Britain, the archaeological richness and diversity of the Somerset Levels in prehistoric times 3 has perhaps distracted investigators away from the growing evidence for parallel human activity on the wetlands in the inner Bristol Channel and Severn Estuary generally, and particularly from activities of Roman date. This evidence includes villas within and on the margins of the wetlands, 4 extensive drainage ditches some of which contain pottery, 5 and pottery strews on the present-day shores. 6 Herein we give a detailed account from the Severn Levels upstream of the River Avon of six new sites where Romano-British occupation debris has been recovered, and reassess the strews at Oldbury Flats and Hills Flats, which we show to be accompanied by a hitherto unrecognized range of cultural material. As well as the widespread evidence for settlement, Hills Flats yields material proof similar to that from the Wentlooge Level for wetland drainage of early, although not definitely Roman, date. At all of our sites, including the previously reported Wentlooge Level, there are clear signs of ironmaking (iron ores (Forest of Dean) or tap slag or both), and at one locality every indication that glass was being made and/or fabricated into objects. The apparent diversity and omnipresence of these industrial activities raise substantial questions about the Roman economy of the Severn Levels and, together with the composition of our pottery assemblages, compel us to consider the possible role in trade played by the river. Although it is now clear that human intervention dates from the prehistoric period, the Severn Levels continue to this day to be profoundly influenced by natural forces. Our sites occur in the framework of a complex geological stratigraphy, the understanding of which seems essential to the sound interpretation of the archaeological evidence.
THE SETTING
Geomorphology and geologyThe Severn Estuary occupies the lower part of the Severn Vale ( fig. i 7 ). Opening to the prevailing winds, so that it is at times stormy, 8 the estuary has unusually large tides (mean springs range 12 • 3 m., Avonmouth 9 ) and is consequently swept by powerful currents. 10 Its sand banks are unstable.Marine as well as fluvial processes shaped the mainly soft bedrock during Pleistocene times into a 'valley within a valley' (fig. ia). The outer valley has a broad, relatively level floor, and on its outer margin occur gravelly river terraces. 11 The youngest of the more extensive of these features-the Main Terrace-appears originally to have filled the outer valley, but was largely removed during the last glacial stage, the terrace remnants, together with the bedrock, acquiring periglacial ice-wedge casts and involutions. 12 The Severn had by then occupied the gorgelike inner valley, traceable into the Bristol Channel. 13
