Late Holocene channel changes of the Middle Trent: channel response to a thousand-year flood record

This paper presents recent work on the floodplain sedimentology of the Middle Trent using data from gravel pits, archaeological sites and documentary sources. The Middle Trent has been unusually active during the Holocene in comparison with other large lowland rivers in the British Isles. The Holocene floodplain fill is dominated by sands and gravels with abundant structural evidence of changes in channel pattern and channel type. A thousand-year record of channel change has been reconstructed from palaeochannels and gravel units with radiocarbon dating of brushwood, palaeomagnetic dating of fine channel fills, dendrochronological dating of timber structures and dating via archaeological typologies. The Trent also has a reasonably well-recorded flood history at least since the 11th century AD. A comparison of the flood record and channel change indicates that the same degree of morphological and sedimentary response is not necessarily associated with floods of similar magnitudes, i.e, there is no constant relationship between event magnitude and landform change. Instead, the response seems dependent on the existing state of the channel and medium-term trajectory of channel change. There is evidence at bath the Hemington and Colwick reaches of a cycle of channel change involving a change in channel typology, and dating evidence that this may have migrated downstream. The results of this work provide a medium-term perspective on channel change, which may be more appropriate for large British rivers than short-term monitoring fur both model validation and planning purposes. (C) 2001 Elsevier Science B.V. All rights reserved.