The geomorphological performance of restored and rehabilitated rivers
The geomorphological performance of restored and rehabilitated rivers
This thesis addresses the geomorphological performance of restored and rehabilitated rivers using an ergodic approach. It questions whether qualitative geomorphological models taken from studies of alluvial channel processes can be used to predict river channel response to restoration. These suggest that restoration can significantly affect unmodified reaches downstream, and that sediment yields from these reaches may remain enhanced for some time as the river system adjusts to restoration. A test of this model has been undertaken using the recent lowland River Restoration Project in the UK. This has provided an opportunity to study the type and rate of geomorphological adjustment during and immediately after construction. Field methods used include cross section and long profile surveying, fluvial audits, bank erosion pins, floodplain sediment traps as well as vegetation colonisation sampling. Fifteen other rivers in England, Denmark and Bavaria (restored between 0 and 12 years ago) have also been assessed to identify their short and long term morphological effects. Initially, adjustment is characterised by high rates of morphological change, including growth of in-channel sediment stores and erosion of the bare bank line that modify the geometry of the restored river. Downstream impacts show aggradation of the river bed and enhanced morphological diversity. Restored rivers are still adjusting channel form up to twelve years after restoration. The qualitative model is shown to be inappropriate for restored rivers and downstream reaches, suggesting channel processes in natural rivers are not applicable to restored ones.
A study is also made of the data resolution required to capture river restoration adjustment and which of the current geomorphological assessment techniques are the most sensitive and efficient. Having established their current geomorphological status, restored rivers are appraised as to whether they have achieved their original goals and objectives. This is a difficult task since many restoration schemes lack good, pre-scheme baseline data or even rarer an 'as-built' survey.
University of Southampton
1999
Briggs, Alison Rachel
(1999)
The geomorphological performance of restored and rehabilitated rivers.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
This thesis addresses the geomorphological performance of restored and rehabilitated rivers using an ergodic approach. It questions whether qualitative geomorphological models taken from studies of alluvial channel processes can be used to predict river channel response to restoration. These suggest that restoration can significantly affect unmodified reaches downstream, and that sediment yields from these reaches may remain enhanced for some time as the river system adjusts to restoration. A test of this model has been undertaken using the recent lowland River Restoration Project in the UK. This has provided an opportunity to study the type and rate of geomorphological adjustment during and immediately after construction. Field methods used include cross section and long profile surveying, fluvial audits, bank erosion pins, floodplain sediment traps as well as vegetation colonisation sampling. Fifteen other rivers in England, Denmark and Bavaria (restored between 0 and 12 years ago) have also been assessed to identify their short and long term morphological effects. Initially, adjustment is characterised by high rates of morphological change, including growth of in-channel sediment stores and erosion of the bare bank line that modify the geometry of the restored river. Downstream impacts show aggradation of the river bed and enhanced morphological diversity. Restored rivers are still adjusting channel form up to twelve years after restoration. The qualitative model is shown to be inappropriate for restored rivers and downstream reaches, suggesting channel processes in natural rivers are not applicable to restored ones.
A study is also made of the data resolution required to capture river restoration adjustment and which of the current geomorphological assessment techniques are the most sensitive and efficient. Having established their current geomorphological status, restored rivers are appraised as to whether they have achieved their original goals and objectives. This is a difficult task since many restoration schemes lack good, pre-scheme baseline data or even rarer an 'as-built' survey.
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Published date: 1999
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Local EPrints ID: 463985
URI: http://eprints.soton.ac.uk/id/eprint/463985
PURE UUID: 9530a517-60b9-4107-95d9-5f4e8799131a
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Date deposited: 04 Jul 2022 20:59
Last modified: 04 Jul 2022 20:59
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Author:
Alison Rachel Briggs
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