River restoration and the geomorphology of flood risk

Overview

River restoration encompasses a wide variety of activities to improve physical, chemical and/or biological processes in rivers. Process-based river restoration [Beechie et al., 2010] is gaining prominence as a way to re-establish floodplain-channel connectivity, re-establish natural water and sediment fluxes, and improve aquatic and riparian ecosystems [SEPA, 2015; Dadson et al., 2017]. Most UK catchments have long histories of human interventions that have modified channel morphology [Gilvear et al., 2002; Lewin, 2013] resulting in adverse ecological and flood risk impacts. A variety of stakeholders are now implementing river restoration schemes for natural flood risk management and hydro-geomorphological improvement purposes using a continuum of process-based options. However, an under-investigated topic is the feedback between river restoration scheme morphological change and flood risk. Morphological change may occur as a scheme “beds inâ€ or is impacted by variations in upstream sediment supply.

In this project, you will learn and use state-of-the art monitoring and modelling techniques to advance understanding of the hydrodynamics and morphodynamics of high energy rivers, and will engage directly with stakeholders to deliver impact from your research.

Restoration of high energy upland rivers often focuses on realigning straightened channels to reduce the need for active sediment management to manage flood risk. Restoration practice has, however, outpaced scientific guidance [Wilcock, 2012] which can result in unintended consequences (e.g. river avulsion). The relative dearth of guidance is particularly the case in upland gravel-bed rivers where there is a lack of research on the links between sediment transport and morphological change [Raven et al., 2010]. There is a particular need to assess whether upland river restoration schemes are meeting their design objectives of reducing the need for long-term sediment management interventions and reducing flood risk. There is a need to map, quantify and model sediment connections and associated fluxes at a catchment scale and to assess how river restoration changes such fluxes. Related to this, there is a need to quantify how changes in sediment dynamics influence patterns of flooding both within a restoration scheme and to reaches downstream, particularly in the vicinity of property and critical infrastructure.

The dearth of data on the morphodynamics and sediment fluxes through river restoration schemes reflects post-project monitoring being limited or piecemeal. Qualitative monitoring provides valuable information, but repeat three-dimensional (3D) surveys, which offer complete geographic coverage and sufficiently low vertical errors to map morphological change are now both technically feasible and cost-effective [Williams et al., 2014]. Coupled with allied technologies to monitor sediment dynamics, such as time-integrated suspended sediment sampling [Perks et al., 2013], estimates of particle step lengths using RFID tagged tracer pebbles [Chapuis et al., 2015] and monitoring bedload using impact plates [Rickenmann et al., 2014], there is thus potential to derive time-integrated sediment budgets of restored reaches, to input these into morphodynamics models, and to thus shed light on the hydro-geomorphological river response to restoration.

Click on an image to expand

Image Captions

Figure1.jpg Figure 1: River restoration works at the River Nairn near Aberarder, Scotland (photo by Williams, Oct 2017)
Figure2.jpg Figure 2: River Nairn post-restoration morphology (photo by Williams, Oct 2019)

Methodology

This project involves field data collection and its analysis. It also involves using the data to provide boundary conditions for hydraulic and morphodynamic modelling. The River Nairn river restoration scheme at Aberarder, Scotland, that was implemented in October 2017, is the focus for the project. The Nairn restoration is 3 km long; unprecedented in scale for a high-energy, sediment loaded UK scheme. The student will have access to data from pre- and several post-restoration surveys, and will extend this monitoring dataset.

Field data collection and analysis:
– Mapping catchment-scale sediment connectivity
– Fluvial audit
– Mapping bar and floodplain sedimentology, including quantifying grain size distribution (physical sampling, automated grain size techniques)
– Repeat topographic surveying of restored reaches (total station, RTK-GPS, Terrestrial Laser Scanning (TLS), UAV imagery for Structure-from-Motion (SfM) photogrammetry)
– Particle tracing to establish sediment transport rates (could include RFID pebbles, painted pebbles, smart pebbles, bedload impact plates)
– Time lapse photography to monitor morphodynamics

Modelling:
– High-flow estimation modelling
– 2D hydraulic and morphodynamic modelling (e.g. using Delft3D)

Project Timeline

Year 1

– Training in key field techniques
– Meetings with stakeholders
– Field data acquisition
– Field data analysis

Year 2

– Hydrological, hydraulic and morphodynamic modelling
– Field data acquisition (repeat surveys)
– Field data analysis
– Conference attendance to present initial results
– Submission of paper based on modelling

Year 3

– Field data acquisition (repeat surveys)
– Field data analysis
– Modelling to predict range of potential future outcomes and implications for sediment management
– International conference attendance to present field results
– Submission of paper based on field results
– Analysis and write up

Year 3.5

– Final analysis and write up of thesis
– Dissemination of results to stakeholders
– Thesis submission and examination
– Share end results with key end-user groups

Training
& Skills

Field training will depend on the prior skills of the student, but will include several of the following:
– Field surveying and data analysis (differential GPS, use of Unmanned Aerial Vehicles, Terrestrial Laser Scanning, Structure from Motion techniques, echo-sounding)
– Hydrological modelling (e.g. Flood Estimation Handbook)
– Hydraulic modelling (e.g. Delft3D)
– Use of Matlab, R and/or Python for data processing and analysis. This may include the NERC Advanced Training Course ‘Statistics for Environmental Evaluation’ run by the School of Mathematics and Statistics, University of Glasgow
– Fieldwork safety (Swiftwater course run at Glenmore Lodge)

Transferable skill development: A full and progressive range of transferable skills training is accessible to the student through IAPETUS specific provision and the University of Glasgow.

Training will be delivered by world-leading experts from the Iapetus2 partners, supplemented by attending externally provided specialist courses as required.

References & further reading

Beechie, T. J., D. A. Sear, J. D. Olden, G. R. Pess, J. M. Buffington, H. Moir, P. Roni, and M. M. Pollock (2010), Process-based Principles for Restoring River Ecosystems, BioScience, 60(3), 209-222.
Bernhardt, E.S., M.A. Palmer, J.D. Allan, G. Alexander et al. 2005 Synthesizing U.S. river restoration efforts. Science 308, 636-7.
Chapuis, M., C. J. Bright, J. Hufnagel, and B. MacVicar (2014), Detection ranges and uncertainty of passive Radio Frequency Identification (RFID) transponders for sediment tracking in gravel rivers and coastal environments, Earth Surface Processes and Landforms, 39(15), 2109-2120.
Costa, J. E., and J. E. O’Connor (1995), Geomorphologically effective floods, in Natural and anthropogenic influences in fluvial geomorphology, edited by J. E. Costa, A. J. Miller, K. W. Potter and P. R. Wilcock, pp. 45-56, American Geophysical Union Washington.
Dadson, S. J., et al. (2017), A restatement of the natural science evidence concerning catchment-based ‘natural’ flood management in the UK, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science, 473, 2199.
Gilvear, D. J., K. V. Heal, and A. Stephen (2002), Hydrology and the ecological quality of Scottish river ecosystems, Science of The Total Environment, 294(1-3), 131-159.
Lewin, J. (2013), Enlightenment and the GM floodplain, Earth Surface Processes and Landforms, 38(1), 17-29.
Perks MT, Warburton J, Bracken L. 2013. Critical assessment and validation of a time integrating fluvial suspended sediment sampler, Hydrological Processes, 28(17), 4795-4807.
Raven, E. K., S. N. Lane, and L. J. Bracken (2010), Understanding sediment transfer and morphological change for managing upland gravel-bed rivers, Progress in Physical Geography, 34(1), 23-45.
Rickenmann, D., et al. (2014), Bedload transport measurements with impact plate geophones: comparison of sensor calibration in different gravel-bed streams, Earth Surface Processes and Landforms, 39(7), 928-942.
SEPA (2015), Natural Flood Management Handbook.
Wilcock, P. R. (2012), Stream Restoration in Gravel-Bed Rivers, in Gravel-Bed Rivers, edited by M. Church, P. A. Biron and A. G. Roy, pp. 135-149, John Wiley & Sons, Ltd.
Williams, R. D., J. Brasington, D. Vericat, and D. M. Hicks (2014), Hyperscale terrain modelling of braided rivers: fusing mobile terrestrial laser scanning and optical bathymetric mapping, Earth Surface Processes and Landforms, 39(2), 167-183.

Further Information

Applications: to apply for this PhD please use the url: https://www.gla.ac.uk/study/applyonline/?CAREER=PGR&PLAN_CODES=CF18-7316

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