A preliminary analysis of the morphological adjustment within and downstream of a lowland river subject to river restoration

Sear, David; Briggs, Andrew S.; Brookes, A.

doi:10.1002/(sici)1099-0755(199801/02)8:1<167::aid-aqc264>3.3.co;2-z

Cited by 13 publications

(18 citation statements)

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“…There are several different terms used in the literature for similar, or the same, processes. For example, slump (Coleman 1969;Bray and Kellerhals 1979;Douglas 1983;Sear et al 1998;Stott and Marks 1998;Trimble 2004), slough (Thorne 1982;Neller 1988;Nanson and Croke 1992;Cancienne et al 2008), and slip (Thorne 1981;Thorne and Tovey 1981;Hagerty 1991;Wood et al 2001) are widespread in the literature but sometimes used interchangeably. The classification of riverbank mass failures used in this study is similar to that used for colluvial failures (Varnes 1978;Hungr et al 2001), integrating form and process.…”

Section: Existing Understanding Of Bank Erosion Processesmentioning

confidence: 99%

Quantifying different riverbank erosion processes during an extreme flood event

Grove

Croke

Thompson

2013

Earth Surf Processes Landf

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Riverbank erosion is a major contributor to catchment sediment budgets. At large spatial scales data is often restricted to planform channel change, with little information on process distributions and their sediment contribution. This study demonstrates how multi‐temporal LiDAR and high resolution aerial imagery can be used to determine processes and volumes of riverbank erosion at a catchment scale. Remotely sensed data captured before and after an extreme flood event, enabled a digital elevation model of difference (DoD) to be constructed for the channel and floodplain. This meant that: the spatial area that could be assessed was extensive; three‐dimensional forms of bank failures could be mapped at a resolution that enabled process inference; and the volume and rates of different bank erosion processes over time could be assessed. A classification of riverbank mass failures, integrating form and process, identified a total of 437 mass failure polygons throughout the study area. These were interpreted as wet flow mass failures based on the presence of a well defined scarp wall and the absence of failed blocks on the failure floor. The failures appeared to be the result of: bank exfiltration, antecedent moisture conditions preceding the event, and the historic development of the channel. Using one‐dimensional hydraulic modelling to delineate geomorphic features within the main boundary of the macrochannel, an estimated 1 466 322 m2 of erosion was interpreted as fluvial entrainment, occurring across catchment areas from 30 to 1668 km2. Only 8% of the whole riverbank planform area was occupied by mass failures, whilst fluvial entrainment covered 33%. A third of the volume of material eroded came from mass failures, even though they occupied 19% of the eroded bank area. The availability of repeat LiDAR surveys, combined with high‐resolution aerial photography, was very effective in erosion process determination and quantification at a large spatial scale. Copyright © 2013 John Wiley & Sons, Ltd.

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Section: Existing Understanding Of Bank Erosion Processesmentioning

confidence: 99%

Quantifying different riverbank erosion processes during an extreme flood event

Grove

Croke

Thompson

2013

Earth Surf Processes Landf

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“…Underwood (1996), Biggs et al (1998), Sear, Briggs & Brookes (1998, Steinberger & Wohl (2003) Indicators: little native vegetation removed or damaged during implementation; vegetation that was removed has been replaced and shows signs of viability (e.g. seedling growth); little deposition of fine sediments because of implementation process.…”

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confidence: 99%

Standards for ecologically successful river restoration

Palmer

Bernhardt

Allan

et al. 2005

Journal of Applied Ecology

1,265

1,046

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Summary1. Increasingly, river managers are turning from hard engineering solutions to ecologically based restoration activities in order to improve degraded waterways. River restoration projects aim to maintain or increase ecosystem goods and services while protecting downstream and coastal ecosystems. There is growing interest in applying river restoration techniques to solve environmental problems, yet little agreement exists on what constitutes a successful river restoration effort. 2. We propose five criteria for measuring success, with emphasis on an ecological perspective. First, the design of an ecological river restoration project should be based on a specified guiding image of a more dynamic, healthy river that could exist at the site. Secondly, the river's ecological condition must be measurably improved. Thirdly, the river system must be more self-sustaining and resilient to external perturbations so that only minimal follow-up maintenance is needed. Fourthly, during the construction phase, no lasting harm should be inflicted on the ecosystem. Fifthly, both pre-and postassessment must be completed and data made publicly available. 3. Determining if these five criteria have been met for a particular project requires development of an assessment protocol. We suggest standards of evaluation for each of the five criteria and provide examples of suitable indicators. 4. Synthesis and applications . Billions of dollars are currently spent restoring streams and rivers, yet to date there are no agreed upon standards for what constitutes ecologically beneficial stream and river restoration. We propose five criteria that must be met for a river restoration project to be considered ecologically successful. It is critical that the broad restoration community, including funding agencies, practitioners and citizen restoration groups, adopt criteria for defining and assessing ecological success in restoration. Standards are needed because progress in the science and practice of river restoration has been hampered by the lack of agreed upon criteria for judging ecological success. Without well-accepted criteria that are ultimately supported by funding and implementing agencies, there is little incentive for practitioners to assess and report restoration outcomes. Improving methods and weighing the ecological benefits of various restoration approaches require organized national-level reporting systems.

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“…This phenomenon has been reported for other river restoration projects as well (e.g. Sear et al, 1998). The present study has documented further morphological adjustments to the channel and 10 years later erosion and sedimentation has altered the cross-sectional profiles significantly.…”

Section: Sedimentation Erosion and Bank Retreatmentioning

confidence: 99%

10 years after the largest river restoration project in Northern Europe: Hydromorphological changes on multiple scales in River Skjern

Kristensen

Kronvang

Wiberg‐Larsen

et al. 2014

Ecological Engineering

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a b s t r a c tThe lower river Skjern (Denmark) historically contained a large variation in habitats and the river ran through large areas with wetlands, many backwaters, islands and oxbow lakes. During the 1960s the river was channelized and the wetland drained. A restoration during 2001-2002 transformed 19 km of channelized river into 26 km meandering river. The short-term effects of this restoration have previously been reported and for this study we revisited the river and with new data evaluated the long-term (10 years) hydrological effects of the restoration. The evaluation was done on three different scales: (1) instream habitats, (2) channel stability and (3) re-connection with the floodplain. In-stream habitats had changed little over the past 10 years and the habitats today showed close similarity with the habitats recorded immediately after the restoration. Measurements of channel stability showed that erosion and sedimentation have changed the cross-sectional profiles over the last 10 years, resulting in a net input of sediment to the lower reaches of the river. However, the change of channel form was a slow process and predicted bank retreat over a 100 year period was only up to 6.8 m. Hence the formation of lost habitats (islands, backwaters and oxbow lakes) is a very slow process and the spontaneous development of these habitats will take centuries. Furthermore, the evaluation also showed that the restoration re-connected the river with its floodplain and large areas of riparian areas are today periodically flooded, but that the flooding is controlled and tamed due to the restoration design. The restoration of River Skjern has therefore failed to re-create the natural habitats formerly present and the natural dynamic processes that shape these habitats are slow. To speed up this process we therefore recommend restoration engineering using a natural guiding image when restoring lowland rivers in the future and through this restoring the lost habitats and the dynamic processes characteristic of natural rivers.

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A preliminary analysis of the morphological adjustment within and downstream of a lowland river subject to river restoration

Cited by 13 publications

References 0 publications

Quantifying different riverbank erosion processes during an extreme flood event

Quantifying different riverbank erosion processes during an extreme flood event

Standards for ecologically successful river restoration

10 years after the largest river restoration project in Northern Europe: Hydromorphological changes on multiple scales in River Skjern

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