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

Robert J.P. Strick, Philip Ashworth, Gregory H. Sambrook Smith, Andrew Nicholas, James L. Best, Stuart Lane, Dan Parsons, Christopher J. Simpson, Chris Unsworth, Jonathan Dale

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Images from specially-commissioned aeroplane sorties (manned aerial vehicle, MAV), repeat unmanned aerial vehicles (UAVs) 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 outlined 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.
Original languageEnglish
Number of pages20
JournalEarth Surface Processes and Landforms
DOIs
Publication statusPublished - 3 Dec 2018

Fingerprint

airborne sensing
braided river
bedform
bedload
satellite imagery
sediment
sediment transport
dune
imagery
turbidity
unmanned vehicle
rate
river
image processing
planet
deep water
vehicle
spatial distribution

Bibliographical note

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.

Keywords

  • sandy braided river
  • UAV
  • Drone
  • CubeSat
  • bedforms
  • bedload transport
  • South Saskatchewan River
  • digital elevation model

Cite this

Strick, Robert J.P. ; Ashworth, Philip ; Sambrook Smith, Gregory H. ; Nicholas, Andrew ; Best, James L. ; Lane, Stuart ; Parsons, Dan ; Simpson, Christopher J. ; Unsworth, Chris ; Dale, Jonathan. / Quantification of bedform dynamics and bedload sediment flux in sandy braided rivers from airborne and satellite imagery. In: Earth Surface Processes and Landforms. 2018.
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abstract = "Images from specially-commissioned aeroplane sorties (manned aerial vehicle, MAV), repeat unmanned aerial vehicles (UAVs) 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 outlined 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.",
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note = "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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Quantification of bedform dynamics and bedload sediment flux in sandy braided rivers from airborne and satellite imagery. / Strick, Robert J.P.; Ashworth, Philip; Sambrook Smith, Gregory H.; Nicholas, Andrew; Best, James L.; Lane, Stuart; Parsons, Dan ; Simpson, Christopher J.; Unsworth, Chris; Dale, Jonathan.

In: Earth Surface Processes and Landforms, 03.12.2018.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Quantification of bedform dynamics and bedload sediment flux in sandy braided rivers from airborne and satellite imagery

AU - Strick, Robert J.P.

AU - Ashworth, Philip

AU - Sambrook Smith, Gregory H.

AU - Nicholas, Andrew

AU - Best, James L.

AU - Lane, Stuart

AU - Parsons, Dan

AU - Simpson, Christopher J.

AU - Unsworth, Chris

AU - Dale, Jonathan

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AB - Images from specially-commissioned aeroplane sorties (manned aerial vehicle, MAV), repeat unmanned aerial vehicles (UAVs) 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 outlined 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.

KW - sandy braided river

KW - UAV

KW - Drone

KW - CubeSat

KW - bedforms

KW - bedload transport

KW - South Saskatchewan River

KW - digital elevation model

U2 - 10.1002/esp.4558

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M3 - Article

JO - Earth Surface Processes and Landforms

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