Late Quaternary evolution of a lowland anastomosing river system: Geological-topographic inheritance, non-uniformity and implications for biodiversity and management
Late Quaternary evolution of a lowland anastomosing river system: Geological-topographic inheritance, non-uniformity and implications for biodiversity and management
Lowland multiple-channel rivers are characterised by floodplain-corridor heterogeneity, high ecological and heritage value, and can be in quasi-stable states. This holistic study of a surviving temperate zone example (Culm, UK) uses geomorphological mapping,
14C, direct sediment dating (OSL, fallout radionuclides), and palaeoecology. This reveals the evolution of a channel-floodplain system from an initial braided state in the Late Pleistocene to its late Holocene anastomosing state. After the Pleistocene-Holocene transition the reduced channel system incised into its braid-plain, only able to rework gravels locally due to reduced competence in relation to inherited bounding sediment calibre. This resulted in the creation of terrace islands, palaeochannels, and a stable anastomosing pattern dominated by channel junctions, bifurcations and palaeochannel intersections. Survey, coring and excavation reveal a persistence of mid-channel bars and riffles at channel junctions, and where channels crossed palaeochannel fills. In common with most other European lowland rivers this system evolves in the later Holocene due to both climate and catchment changes with a major hydrological critical transition in the mid-Holocene (c. 5300 BP). However, in the case of the Culm, the increase in fine sediment supply often seen in lowland catchments in the Middle-Late Holocene, occurred later, and was insufficient to convert the system to a single medium-low sinuosity channel-floodplain. This allowed the persistence of high heterogeneity and biodiversity (including the persistence of riffle beetles) as part of multiple-scales of non-uniformity. Indeed the pool-riffle persistence is an example of this system's non-uniformity, being due, at least in part, to the effects of previous channel history. This paper reveals why this river survived in a multichannel state, and by implication, why others did not. These results are being used in the bespoke eco-heritage management of the Culm, but could also inform the restoration of other former multi-channel lowland temperate river systems worldwide.
Catchment change, Coleoptera, Floodplain ecology, Landform non-uniformity, Rewilding, River corridors
Brown, Antony G.
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Rhodes, Edward J.
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Davis, Steve
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Zhang, Yusheng
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Pears, Ben
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Whitehouse, Nicki J.
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Bradley, Chris
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Bennett, Jenny
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Schwenninger, Jean-luc
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Firth, Antony
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Firth, Emma
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Hughes, Paul
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Walling, Des
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15 May 2021
Brown, Antony G.
c51f9d3e-02b0-47da-a483-41c354e78fab
Rhodes, Edward J.
ae4d74d1-ca61-42b1-b83f-f129c1a7f572
Davis, Steve
e538180c-a836-4366-a96d-8c0ace28bd50
Zhang, Yusheng
10ae2671-769c-49b0-8bc1-ae764a69e0ad
Pears, Ben
e80551e2-8ec4-4e7a-9501-dada7c732f39
Whitehouse, Nicki J.
d288a39c-d57e-4852-b794-a8a3d7a2c403
Bradley, Chris
8d555306-25ba-4c2e-b0fe-b335d23b5fe8
Bennett, Jenny
506406ae-3bcb-4ab9-b947-a4458627aedd
Schwenninger, Jean-luc
e5bd3170-c1e9-4be5-99ce-1342a3bda7dc
Firth, Antony
4c930846-1caf-4dde-8a21-62e552e65d4a
Firth, Emma
91b855b6-e1a1-4b98-857f-621012959294
Hughes, Paul
14f83168-b203-4a91-a850-8c48535dc31b
Walling, Des
29d2985e-385b-41de-8909-1d030eea4037
Brown, Antony G., Rhodes, Edward J., Davis, Steve, Zhang, Yusheng, Pears, Ben, Whitehouse, Nicki J., Bradley, Chris, Bennett, Jenny, Schwenninger, Jean-luc, Firth, Antony, Firth, Emma, Hughes, Paul and Walling, Des
(2021)
Late Quaternary evolution of a lowland anastomosing river system: Geological-topographic inheritance, non-uniformity and implications for biodiversity and management.
Quaternary Science Reviews, 260, [106929].
(doi:10.1016/j.quascirev.2021.106929).
Abstract
Lowland multiple-channel rivers are characterised by floodplain-corridor heterogeneity, high ecological and heritage value, and can be in quasi-stable states. This holistic study of a surviving temperate zone example (Culm, UK) uses geomorphological mapping,
14C, direct sediment dating (OSL, fallout radionuclides), and palaeoecology. This reveals the evolution of a channel-floodplain system from an initial braided state in the Late Pleistocene to its late Holocene anastomosing state. After the Pleistocene-Holocene transition the reduced channel system incised into its braid-plain, only able to rework gravels locally due to reduced competence in relation to inherited bounding sediment calibre. This resulted in the creation of terrace islands, palaeochannels, and a stable anastomosing pattern dominated by channel junctions, bifurcations and palaeochannel intersections. Survey, coring and excavation reveal a persistence of mid-channel bars and riffles at channel junctions, and where channels crossed palaeochannel fills. In common with most other European lowland rivers this system evolves in the later Holocene due to both climate and catchment changes with a major hydrological critical transition in the mid-Holocene (c. 5300 BP). However, in the case of the Culm, the increase in fine sediment supply often seen in lowland catchments in the Middle-Late Holocene, occurred later, and was insufficient to convert the system to a single medium-low sinuosity channel-floodplain. This allowed the persistence of high heterogeneity and biodiversity (including the persistence of riffle beetles) as part of multiple-scales of non-uniformity. Indeed the pool-riffle persistence is an example of this system's non-uniformity, being due, at least in part, to the effects of previous channel history. This paper reveals why this river survived in a multichannel state, and by implication, why others did not. These results are being used in the bespoke eco-heritage management of the Culm, but could also inform the restoration of other former multi-channel lowland temperate river systems worldwide.
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Late Quaternary evolution of a lowland anastomosing river system
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Accepted/In Press date: 1 April 2021
e-pub ahead of print date: 18 April 2021
Published date: 15 May 2021
Additional Information:
Funding Information:
The authors acknowledge initial funding from UKRI-NERC under NER/A/2000/00394/and later support from the Universities of Exeter and Southampton, UK. Rothamsted Research receives strategic funding from UKRI-BBSRC (UK Research and Innovation ? Biotechnology and Biological Sciences Research Council, and Y. Zhang is currently funded by project BBS/E/C/000I0330 ? Soil to Nutrition Project 3. The Historic Watercourse: River Culm project carried out by Fjordr Limited is funded by Historic England through its Heritage Protection Commissions programme. Thanks go to R. Fletcher for the pollen and macrofossil analyses, A. Ames and J. Grapes for laboratory work, Z. Ruiz for comments on chironomids, L. Basell and O. Bayer for their comments on the lithics, R. Scrivener for geological expertise. Our gratitude is also extended to the many landowners and the Woodland Trust for allowing access to the study sites and L. Aspden for cartographic assistance. Thanks also to very helpful comments by G. Nanson, P. Carling, P. Bishop. El. Wohl and S. Tooth as well as the referees. This paper is dedicated to the memory of Ken Gregory CBE (1938?2020) who both worked on the Exe/Culm and commented on this project in its early stages.
Funding Information:
The authors acknowledge initial funding from UKRI- NERC under NER/A/2000/00394/ and later support from the Universities of Exeter and Southampton, UK. Rothamsted Research receives strategic funding from UKRI -BBSRC (UK Research and Innovation – Biotechnology and Biological Sciences Research Council , and Y. Zhang is currently funded by project BBS/E/C/000I0330 – Soil to Nutrition Project 3 . The Historic Watercourse: River Culm project carried out by Fjordr Limited is funded by Historic England through its Heritage Protection Commissions programme . Thanks go to R. Fletcher for the pollen and macrofossil analyses, A. Ames and J. Grapes for laboratory work, Z. Ruiz for comments on chironomids, L. Basell and O. Bayer for their comments on the lithics, R. Scrivener for geological expertise. Our gratitude is also extended to the many landowners and the Woodland Trust for allowing access to the study sites and L. Aspden for cartographic assistance. Thanks also to very helpful comments by G. Nanson, P. Carling, P. Bishop. El. Wohl and S. Tooth as well as the referees. This paper is dedicated to the memory of Ken Gregory CBE (1938–2020) who both worked on the Exe/Culm and commented on this project in its early stages.
Publisher Copyright:
© 2021 The Authors
Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.
Keywords:
Catchment change, Coleoptera, Floodplain ecology, Landform non-uniformity, Rewilding, River corridors
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Local EPrints ID: 449383
URI: http://eprints.soton.ac.uk/id/eprint/449383
ISSN: 0277-3791
PURE UUID: f87abd7c-cd46-4358-8a8a-caa047e675e2
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Date deposited: 26 May 2021 16:32
Last modified: 17 Mar 2024 06:35
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Contributors
Author:
Edward J. Rhodes
Author:
Steve Davis
Author:
Yusheng Zhang
Author:
Ben Pears
Author:
Nicki J. Whitehouse
Author:
Chris Bradley
Author:
Jenny Bennett
Author:
Jean-luc Schwenninger
Author:
Antony Firth
Author:
Emma Firth
Author:
Des Walling
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