Variability of late Holocene braiding in Britain

Braided channel patterns are relatively rarely found in contemporary British rivers, although site studies have been undertaken for reaches in catchments ranging in size from 2.6 km ² to 2850 km ² in area. Systematic study of two major British rivers, the Tyne (2927 km ²) and the Upper Severn (1000 km ²), reveal braiding at several sites, albeit at a limited scale. An examination of historical maps and air photographs shows, however, that braiding processes have been more widely active in the eighteenth and nineteenth centuries. Episodic braiding activity is discussed for selected sites. Floodplain stratigraphy shows significant channel aggradation and transformation to braided river planforms also occurred in the late Roman period and in the thirteenth and fourteenth centuries. Possible explanations are suggested in terms of flood frequency and magnitude variations (reflecting climatic fluctuations and land-use change), alterations in sediment supply (including the impact of historic mining activities), and channelization control.