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Quantification of bedform dynamics and bedload sediment flux in sandy braided rivers from airborne and satellite imagery

Strick, Robert J.P.; Dale, Jonathan; Ashworth, Philip J.; Sambrook Smith, Gregory H.; Nicholas, Andrew P.; Best, James L.; Lane, Stuart N.; Parsons, Daniel R.; Simpson, Christopher J.; Unsworth, Christopher A.

Authors

Robert J.P. Strick

Philip J. Ashworth

Gregory H. Sambrook Smith

Andrew P. Nicholas

James L. Best

Stuart N. Lane

Christopher J. Simpson

Christopher A. Unsworth

Jonathan Dale

Abstract

Images from specially‐commissioned aeroplane sorties (manned aerial vehicle, MAV), repeat unmanned aerial vehicle (UAV) surveys, and Planet CubeSat satellites are used to quantify dune and bar dynamics in the sandy braided South Saskatchewan River, Canada. Structure‐from‐Motion (SfM) techniques and application of a depth‐brightness model are used to produce a series of Digital Surface Models (DSMs) at low and near‐bankfull flows. A number of technical and image processing challenges are described that arise from the application of SfM in dry and submerged environments. A model for best practice is presented and analysis suggests a depth‐brightness model approach can represent the different scales of bedforms present in sandy braided rivers with low‐turbidity and shallow (< 2 m deep) water.

The aerial imagery is used to quantify the spatial distribution of unit bar and dune migration rate in an 18 km reach and three ~1 km long reaches respectively. Dune and unit bar migration rates are highly variable in response to local variations in planform morphology. Sediment transport rates for dunes and unit bars, obtained by integrating migration rates (from UAV) with the volume of sediment moved (from DSMs using MAV imagery) show near‐equivalence in sediment flux. Hence, reach‐based sediment transport rate estimates can be derived from unit bar data alone. Moreover, it is shown that reasonable estimates of sediment transport rate can be made using just unit bar migration rates as measured from 2D imagery, including from satellite images, so long as informed assumptions are made regarding average bar shape and height. With recent availability of frequent, repeat satellite imagery, and the ease of undertaking repeat MAV and UAV surveys, for the first time, it may be possible to provide global estimates of bedload sediment flux for large or inaccessible low‐turbidity rivers that currently have sparse information on bedload sediment transport rates.

Journal Article Type Article
Publication Date Mar 30, 2019
Journal Earth Surface Processes and Landforms
Print ISSN 0197-9337
Electronic ISSN 1096-9837
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 44
Issue 4
Pages 953-972
Institution Citation Strick, R. J., Ashworth, P. J., Sambrook Smith, G. H., Nicholas, A. P., Best, J. L., Lane, S. N., …Dale, J. (2019). Quantification of bedform dynamics and bedload sediment flux in sandy braided rivers from airborne and satellite imagery. Earth surface processes and landforms : the journal of the British Geomorphological Research Group, 44(4), 953-972. https://doi.org/10.1002/esp.4558
DOI https://doi.org/10.1002/esp.4558
Keywords Earth-Surface Processes; Earth and Planetary Sciences (miscellaneous); Geography, Planning and Development
Publisher URL https://onlinelibrary.wiley.com/doi/full/10.1002/esp.4558

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Copyright Statement
© 2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.




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