An eclectic range of stratigraphical. sedimentological, geochemical, archaeological and historical evidence relating to a tidal palaeochannel exposed at a deep erosional level in the modern intertidal zone on the Avon–Gloucestershire border demonstrates that tidal wetlands reclaimed during the Roman period ranged much further seaward than the modern coastline. Vigorous late medieval-early modern erosion, linked to the cool, disturbed conditions of the Little Ice Age, forced the coastline by the mid-seventeenth century to a location inland of its present line. A possible medieval landing place was destroyed and it was necessary to set back the flood defences. As the result of renewed mudflat-marsh growth, the coast at Hills Flats has built outward during modern times, but in three distinct stages and by no means as far seaward as its likely Roman position.