Holocene fluvial geomorphology of the River Exe (UK) from archaeological and historical data and implications for urban form

Archaeological and historical traces of the changing location and character of the channels of the River Exe are visible in many parts of the city of Exeter and the lower reaches of the Exe valley. Records of archaeological sites in the Exeter area investigated by Exeter Archaeology were interrogated to select sites with dated channel bases in order to measure and date channel change during the Middle and Late Holocene. This was combined with a series of historical maps of the city which recorded both the location of river channels and morphological changes caused by human utilization of the river over the last 426 years. The combined data reveal that the river has had a long Holocene history of avulsion and channel switching reoccupying former channels (two main channels) and confinement of the channels to form leats with eventual channel infilling by urban development. The location of the city, as the lowest bridging point in the Roman period, and the tidal influence below a pronounced bedrock step is important both geomorphologically and historically. The typical tendency of the river to anabranch in this reach structured early urban development and was responsible for the construction of a large multi-arch bridge much of which still exists today. The location of islands was, as with many other European cities, taken full advantage of through the construction of mills for a variety of agricultural and industrial purposes. Thus fluvial geomorphology facilitated the spatial separation of different proto-urban and industrial functions within growing urban settlements in the Mediaeval Period.