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The influence of geomorphology on large wood dynamics in a low gradient headwater stream

The influence of geomorphology on large wood dynamics in a low gradient headwater stream
The influence of geomorphology on large wood dynamics in a low gradient headwater stream
Understanding large wood dynamics is critical for a range of disciplines including flood risk management, ecology and geomorphology. Despite the importance of wood in rivers, our understanding of the mobility of large wood remains limited. In this study individual pieces of large wood were tagged and surveyed over a 32 month period within a third and fourth order lowland forest river. Individual pieces of wood were found to be highly mobile, with 75% of pieces moving during the survey period, and a maximum transport distance of 5.6 km. Multivariate analyses of data from this study and two other published studies identified dimensionless wood length as the important factor in explaining likelihood of movement. A length threshold of 2.5 channel widths is identified for near functional immobility, with few pieces above this size moving. In addition, for this study, wood type, branching complexity, location and dimensionless wood diameter were found to be important in determining mobility only for sinuous reaches with readily inundated floodplains. Where logjams persist over multiple years they were shown to be reworked, with component pieces being transported away and replaced by newly trapped pieces. The findings of this study have implications for river management and restoration. The high mobility observed in this study demonstrates that only very large pieces of wood of length greater than 2.5 channel widths should be considered functionally immobile. For pieces of wood of length less than the channel width the possibility of high rates of mobility and long transport distances should be anticipated.
0043-1397
9194-9210
Dixon, Simon J.
abb0d02d-6663-40ea-b3ee-07bc962cd693
Sear, David
ccd892ab-a93d-4073-a11c-b8bca42ecfd3
Dixon, Simon J.
abb0d02d-6663-40ea-b3ee-07bc962cd693
Sear, David
ccd892ab-a93d-4073-a11c-b8bca42ecfd3

Dixon, Simon J. and Sear, David (2014) The influence of geomorphology on large wood dynamics in a low gradient headwater stream. Water Resources Research, 50 (12), 9194-9210. (doi:10.1002/2014WR015947).

Record type: Article

Abstract

Understanding large wood dynamics is critical for a range of disciplines including flood risk management, ecology and geomorphology. Despite the importance of wood in rivers, our understanding of the mobility of large wood remains limited. In this study individual pieces of large wood were tagged and surveyed over a 32 month period within a third and fourth order lowland forest river. Individual pieces of wood were found to be highly mobile, with 75% of pieces moving during the survey period, and a maximum transport distance of 5.6 km. Multivariate analyses of data from this study and two other published studies identified dimensionless wood length as the important factor in explaining likelihood of movement. A length threshold of 2.5 channel widths is identified for near functional immobility, with few pieces above this size moving. In addition, for this study, wood type, branching complexity, location and dimensionless wood diameter were found to be important in determining mobility only for sinuous reaches with readily inundated floodplains. Where logjams persist over multiple years they were shown to be reworked, with component pieces being transported away and replaced by newly trapped pieces. The findings of this study have implications for river management and restoration. The high mobility observed in this study demonstrates that only very large pieces of wood of length greater than 2.5 channel widths should be considered functionally immobile. For pieces of wood of length less than the channel width the possibility of high rates of mobility and long transport distances should be anticipated.

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Accepted/In Press date: 20 October 2014
Published date: 5 December 2014
Organisations: Earth Surface Dynamics

Identifiers

Local EPrints ID: 396863
URI: http://eprints.soton.ac.uk/id/eprint/396863
ISSN: 0043-1397
PURE UUID: 9460174c-9591-4eee-a479-58670e1f5e3e
ORCID for David Sear: ORCID iD orcid.org/0000-0003-0191-6179

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Date deposited: 15 Jun 2016 08:39
Last modified: 15 Mar 2024 02:47

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Contributors

Author: Simon J. Dixon
Author: David Sear ORCID iD

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