Sediment‐related river maintenance: The role of fluvial geomorphology

Sear, David; Newson, Malcolm; Brookes, A.

doi:10.1002/esp.3290200706

Cited by 122 publications

(75 citation statements)

References 9 publications

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“…Ultimately, and despite repeated calls (e.g. Sear et al, 1995), we still do not properly address geomorphological processes in flood risk management studies and we desperately need tools that can predict the medium-term (annual to decadal) response of river beds and river banks to sediment delivery in order to assess flood risk impacts. This should include consideration of those types of system where aggradation issues are relevant.…”

Section: Discussionmentioning

confidence: 99%

Interactions between sediment delivery, channel change, climate change and flood risk in a temperate upland environment

Lane¹,

Tayefi²,

Reid³

et al. 2006

Earth Surf Processes Landf

217

183

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This paper uses numerical simulation of flood inundation based on a coupled one-dimensionaltwo-dimensional treatment to explore the impacts upon flood extent of both long-term climate changes, predicted to the 2050s and 2080s, and short-term river channel changes in response to sediment delivery, for a temperate upland gravel-bed river. Results show that 16 months of measured in-channel sedimentation in an upland gravel-bed river cause about half of the increase in inundation extent that was simulated to arise from climate change. Consideration of the joint impacts of climate change and sedimentation emphasized the nonlinear nature of system response, and the possibly severe and synergistic effects that come from combined direct effects of climate change and sediment delivery. Such effects are likely to be exacerbated further as a result of the impacts of climate change upon coarse sediment delivery. In generic terms, these processes are commonly overlooked in flood risk mapping exercises and are likely to be important in any river system where there are high rates of sediment delivery and long-term transfer of sediment to floodplain storage (i.e. alluviation involving active channel aggradation and migration). Similarly, attempts to reduce channel migration through river bank stabilization are likely to exacerbate this process as without bank erosion, channel capacity cannot be maintained. Finally, many flood risk mapping studies rely upon calibration based upon combining contemporary bed surveys with historical flood outlines, and this will lead to underestimation of the magnitude and frequency of floodplain inundation in an aggrading system for a flood of a given magnitude.

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Section: Discussionmentioning

confidence: 99%

Interactions between sediment delivery, channel change, climate change and flood risk in a temperate upland environment

Lane¹,

Tayefi²,

Reid³

et al. 2006

Earth Surf Processes Landf

217

183

View full text Add to dashboard Cite

show abstract

“…Reach position within a catchment also dictates the degree to which it is affected by disturbance events of various magnitude and frequency (e.g., the upstream progression of a headcut or downstream movement of a sediment slug) (Sear et al 1995). This is regulated by the degree of (dis)connectivity between reaches, determining if and where disturbance will be manifest in a catchment (Kondolf et al 2006, Fryirs et al 2007).…”

Section: Is Each Treatment Reach Appropriately Placed In Its Catchmenmentioning

confidence: 99%

Naturalness and Place in River Rehabilitation

Fryirs¹,

Brierley²

2009

E&S

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ABSTRACT. An authentic approach to river rehabilitation emphasizes concerns for the natural values of a given place. As landscape considerations fashion the physical template upon which biotic associations take place, various geomorphic issues must be addressed in framing rehabilitation activities that strive to improve river health. An open-ended approach to river classification promotes applications that appreciate the values of a given river, rather than pigeonholing reality. As the geomorphic structure of some rivers is naturally simple, promoting heterogeneity as a basis for management may not always be appropriate. Efforts to protect unique attributes of river systems must be balanced with procedures that look after common features. Concerns for ecosystem functionality must relate to the behavioral regime of a given river, remembering that some rivers are inherently sensitive to disturbance. Responses to human disturbance must be viewed in relation to natural variability, recognizing how spatial relationships in a catchment, and responses to past disturbances, fashion the operation of contemporary fluxes. These fluxes, in turn, influence what is achievable in the rehabilitation of a given reach. Given the inherently adjusting and evolutionary nature of river systems, notional endpoints do not provide an appropriate basis upon which to promote concepts of naturalness and place in the rehabilitation process. These themes are drawn together to promote rehabilitation practices that relate to the natural values of each river system, in preference to applications of "cookbook" measures that build upon textbook geomorphology.

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“…Planned maintenance may not be required and hence operators run the risk of spending resources unnecessarily, while breakdown maintenance treats local erosion and siltation problems in isolation from channel form and process at the watershed scale (Sear et al, 1995). It is this focus on the local scale that has been identified as a major problem with historic sediment management in rivers.…”

Section: Traditional Approaches To Sediment Managementmentioning

confidence: 99%

Geomorphic Approach to Regional Sediment Management in Engineered and Restored Fluvial Systems

Thorne¹,

Skinner²

2001

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SUMMARYThis document reviews contemporary practice in regional sediment management. It examines whether catchment wide sediment issues have been considered in the design of engineering and restoration/rehabilitation projects. The study has been undertaken through a review of documented literature in addition to contacting leading practitioners in the field. The results suggest that historically catchment wide sediment issues were rarely addressed in the design of schemes, leading to many project failures. Recently, however, there has been increased consideration of regional sediment issues in the design of schemes. This has been complemented by the development of an increasing number of design approaches that include sediment continuity as an integral part of their procedure. The use of these approaches is still fairly limited and they remain unproven as practical tools. Consequently, there is a need to further refine these methods and ensure that they are suitable to be adopted into widespread engineering practice.In addition, an important requirement for future practice is to enable schemes to be designed taking into account previously documented experiences. This will help projects avoid previous mistakes and define best practice for the future. As a result, an existing geomorphic PostProject Appraisal approach has been refined to focus specifically on the assessment of regional sediment issues. A Regional Sediment Appraisal Methodology has thus been developed and outlined here.Broad conclusions from the project suggest that:• Historically regional sediment management has been inadequately addressed in the design of projects and this is illustrated by the large amount of failures that have been discovered (Frissell and Nawa, 1992;O'Neill and Fitch, 1992;Beschta et al, 1994;Miles, 1998).• A number of catchment based approaches evolved during the 1990s. Their main focus has been to develop an understanding of how the watershed and drainage system operates before siting and designing river engineering projects and management schemes.• The main types of projects that have addressed sediment continuity in their design have either been demonstration projects, large interdisciplinary schemes or those that have had a significant academic involvement. Sediment continuity is seldom addressed routinely in operational projects.• Monitoring and performance appraisals of schemes are seldom undertaken in flood control projects and are still rare in river restoration programmes.Key recommendations are:• Future river management projects need to adopt a watershed approach to enable schemes to be located, and designed, appropriately to ensure sediment continuity is maintained.• Research should be performed to further test and refine catchment and reach-scale approaches to enable these techniques to be used in the design and siting of restoration projects.iv Present qualitative analyses of watershed and reach-scale should be further developed to provide the basis for quantitative sediment budgeting at the scale of the fluvial sy...

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Sediment‐related river maintenance: The role of fluvial geomorphology

Cited by 122 publications

References 9 publications

Interactions between sediment delivery, channel change, climate change and flood risk in a temperate upland environment

Interactions between sediment delivery, channel change, climate change and flood risk in a temperate upland environment

Naturalness and Place in River Rehabilitation

Geomorphic Approach to Regional Sediment Management in Engineered and Restored Fluvial Systems

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