The effect of woody vegetation on the geomorphology of a lowland floodplain: a study of a basin in southern England
The effect of woody vegetation on the geomorphology of a lowland floodplain: a study of a basin in southern England
Previously published research has not explicitly investigated lateral and vertical accretion on lowland wooded floodplains. This thesis describes how these lacunae were addressed with three field campaigns undertaken along the Highland Water, a small lowland stream that is surrounded by one of the largest areas of uncleared woodland in England.
Firstly, a catchment-scale survey identified the geomorphology of this lowland forested floodplain. Visual observations were made of floodplain features and channel characteristics; and the width of the channel, the area most recently flooded, and the maximum extent of the floodplain were measured. This survey provides the first inventory of geomorphological features found on a wooded lowland floodplain. The channel and floodplain were split into reaches that were observed to be geomorphologically homogeneous. The outcomes from this survey were that management and in-channel accumulations of woody debris appeared to be primarily responsible for changes in floodplain formation.
A second survey, similar to the first but more focused upon lateral channel change, provided evidence to suggest that lateral accretion was frequently determined by vegetation. Rates of channel change were found to be extremely low, except in the vicinity of in-channel accumulation of debris, which caused change at the reach scale (101-102m). In contrast with cleared floodplains, lateral river accretion was not focused at meander apices, but instead within zones of discrete floodplain activity directly caused by in-channel blockages of woody debris. This debris also caused significant areas of overbank flow to occur.
Thirdly, reach-scale experiments into floodplain sedimentation determined that vertical accretion did occur, but the pattern and amount of sediment deposited was a direct result of floodplain vegetation, particularly trees and LWD.
These controls of vegetation upon fluvial and floodplain processes also have implications for long-term landscape development and may explain the palaeoenvironmental history of many lowland floodplains. The findings from this thesis could also be used to design and implement sustainable forest floodplain management practices.
University of Southampton
Jeffries, Richard
4e1bc53d-7849-4a2d-bf60-27645189b468
2002
Jeffries, Richard
4e1bc53d-7849-4a2d-bf60-27645189b468
Jeffries, Richard
(2002)
The effect of woody vegetation on the geomorphology of a lowland floodplain: a study of a basin in southern England.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Previously published research has not explicitly investigated lateral and vertical accretion on lowland wooded floodplains. This thesis describes how these lacunae were addressed with three field campaigns undertaken along the Highland Water, a small lowland stream that is surrounded by one of the largest areas of uncleared woodland in England.
Firstly, a catchment-scale survey identified the geomorphology of this lowland forested floodplain. Visual observations were made of floodplain features and channel characteristics; and the width of the channel, the area most recently flooded, and the maximum extent of the floodplain were measured. This survey provides the first inventory of geomorphological features found on a wooded lowland floodplain. The channel and floodplain were split into reaches that were observed to be geomorphologically homogeneous. The outcomes from this survey were that management and in-channel accumulations of woody debris appeared to be primarily responsible for changes in floodplain formation.
A second survey, similar to the first but more focused upon lateral channel change, provided evidence to suggest that lateral accretion was frequently determined by vegetation. Rates of channel change were found to be extremely low, except in the vicinity of in-channel accumulation of debris, which caused change at the reach scale (101-102m). In contrast with cleared floodplains, lateral river accretion was not focused at meander apices, but instead within zones of discrete floodplain activity directly caused by in-channel blockages of woody debris. This debris also caused significant areas of overbank flow to occur.
Thirdly, reach-scale experiments into floodplain sedimentation determined that vertical accretion did occur, but the pattern and amount of sediment deposited was a direct result of floodplain vegetation, particularly trees and LWD.
These controls of vegetation upon fluvial and floodplain processes also have implications for long-term landscape development and may explain the palaeoenvironmental history of many lowland floodplains. The findings from this thesis could also be used to design and implement sustainable forest floodplain management practices.
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Published date: 2002
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Local EPrints ID: 464751
URI: http://eprints.soton.ac.uk/id/eprint/464751
PURE UUID: f1ed08aa-5a8f-42bc-821c-6a58b53088d3
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Date deposited: 04 Jul 2022 23:59
Last modified: 16 Mar 2024 19:43
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Author:
Richard Jeffries
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