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

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

doi:10.1002/esp.4558

Cited by 27 publications

(21 citation statements)

References 75 publications

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“…This technique, known as GNSS-supported aerial triangulation (GNSS-AT; Benassi et al, 2017), has been shown to result in sub-GSD horizontal accuracy without the use of GCPs (Mian et al, 2015;Fazeli et al, 2016;Hugenholtz et al, 2016;Benassi et al, 2017;van der Sluijs et al, 2018). Published applications of this technique in the geosciences are so far limited (van der Sluijs et al, 2018;Strick et al, 2018), and no studies have yet examined the appropriateness of this technique for the study of glacial dynamics.…”

Section: Introductionmentioning

confidence: 99%

High-accuracy UAV photogrammetry of ice sheet dynamics with no ground control

et al. 2019

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Abstract. Unmanned aerial vehicles (UAVs) and structure from motion with multi-view stereo (SfM–MVS) photogrammetry are increasingly common tools for geoscience applications, but final product accuracy can be significantly diminished in the absence of a dense and well-distributed network of ground control points (GCPs). This is problematic in inaccessible or hazardous field environments, including highly crevassed glaciers, where implementing suitable GCP networks would be logistically difficult if not impossible. To overcome this challenge, we present an alternative geolocation approach known as GNSS-supported aerial triangulation (GNSS-AT). Here, an on-board carrier-phase GNSS receiver is used to determine the location of photo acquisitions using kinematic differential carrier-phase positioning. The camera positions can be used as the geospatial input to the photogrammetry process. We describe the implementation of this method in a low-cost, custom-built UAV and apply the method in a glaciological setting at Store Glacier in western Greenland. We validate the technique at the calving front, achieving topographic uncertainties of ±0.12 m horizontally (∼1.1× the ground sampling distance) and ±0.14 m vertically (∼1.3× the ground sampling distance), when flying at an altitude of ∼ 450 m above ground level. This compares favourably with previous GCP-derived uncertainties in glacial environments and allows us to apply the SfM–MVS photogrammetry at an inland study site where ice flows at 2 m day−1 and stable ground control is not available. Here, we were able to produce, without the use of GCPs, the first UAV-derived velocity fields of an ice sheet interior. Given the growing use of UAVs and SfM–MVS in glaciology and the geosciences, GNSS-AT will be of interest to those wishing to use UAV photogrammetry to obtain high-precision measurements of topographic change in contexts where GCP collection is logistically constrained.

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Section: Introductionmentioning

confidence: 99%

High-accuracy UAV photogrammetry of ice sheet dynamics with no ground control

et al. 2019

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“…In addition to their previous identification at the Stoer Peninsula (e.g., Ghinassi and Ielpi, 2018), such packages were recognized across the Torridonian outcrop belt over the course of this study (n = 85). However, such packages are not conclusively diagnostic of meandering planforms because lateral accretion can occur on the flanks of mid-channel braid bars during waning flood (e.g., Best et al, 2003;Strick et al, 2018). Conversely, as all rivers have a degree of variability in planview morphology (e.g., Ethridge, 2011), it is possible that some of the lateral-accretion deposits recognized in this study record deposition in locally sinuous channels.…”

Section: Fluvial Stylementioning

confidence: 79%

Physical and biological functioning in Proterozoic rivers: evidence from the archetypal pre-vegetation alluvium of the Torridon Group, NW Scotland

McMahon

Davies

2019

SJG

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In modern rivers, vegetation affects hydrological, geomorphological and sedimentological functioning, so extant fluvial systems can provide only partial analogues for those rivers that operated before the evolution of land plants. However, pre-vegetation rivers were the norm for the first 90% of Earth's history and so a better understanding of their sedimentary product can provide insights into both the fundamental underlying mechanisms of river behaviour and the ways in which fluvial processes operated on ancient Earth. In addition to a short review of the history of research into pre-vegetation alluvium, this paper presents a fieldwork-based case study of the later Proterozoic Torridon Group, which contains some of the most extensive and easily accessible exposures of pre-vegetation alluvium worldwide. Three alluvial architectural deposits have been recognized: (1) channel-bedform deposits (c. 80%); (2) barform deposits (c. 20%); and (3) out-of-channel deposits (≪1%). Channel-bedform deposits have erosional bases and most frequently stack vertically to form thick multistorey channel-bedform sequences. The preferential preservation of these deposits, which record the deepest parts of river channels, suggests that channel migration had a dominant control on preservation in the Torridon Group. Less frequently, channel-bedform deposits pass upwards into a genetically related barform deposit. Barform preservation in these instances is interpreted to be due to channel avulsion, which protected the barforms from reworking. Channel-bar thickness, measured from the basal erosional surface of a channel-bedform deposit to the top of its associated barform deposit, indicates minimum water depths of 1.7 to 8.0 m. Downstream-accreting barform deposits are most frequent, but lateral and upstream modes of accretion are also well represented. Dominant southeastward-palaeoflow directions imply that the Torridonian rivers were sourced from the Grenvillian Mountain Belt. The preserved architectural deposits and narrow dispersal of palaeocurrent data are explained by interpreting the Torridon Group as the alluvium of dominantly low-sinuosity rivers, with signatures recording autogenic fluvial adjustments. In the few rare instances where out-of-channel deposits are preserved, they contain fossil evidence for microbial mats, which prove that not all Proterozoic river systems were wholly abiotic. The overall characteristics of the Torridon alluvium, in terms of its ubiquitous highly tabular beds of sand-grade or coarser material, make it an archetypal example of pre-vegetation alluvium as known globally.Thematic collection: This article is part of the SJG Collection on Early-Career Research available at: https://www.lyellcollection.org/cc/SJG-early-career-research

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“…The Castlegate Sandstone comprises amalgamated fluvial channel-belt deposits which, architecturally, are dominated by barforms (e.g., mid-channel bars) (Miall, 1993(Miall, , 1994). Therefore, cross-sets that we measured in the Castlegate Sandstone likely preserve bedforms that were influenced by barform migration, and it is possible that low CV(hxs) values observed in these cross-sets reflect bedform disequilibrium dynamics associated with the hierarchy hypothesis, especially given that unit bar migration typical of braided rivers can be comparable to dune migration rates (Strick et al, 2019). Conversely, fluvial strata of the Blackhawk Formation and Ferron Sandstone comprise major channelized sandstone bodies Chidsey et al, 2004;Hampson et al, 2013;Flood & Hampson, 2014) which, while abundant in barforms (e.g., laterally accreted point bar deposits; Fig.…”

Section: Implications Of the Hierarchy Hypothesis For Bedform Preservationmentioning

confidence: 98%

Field evidence for disequilibrium dynamics in preserved fluvial cross-strata: A record of discharge variability or morphodynamic hierarchy?

Lyster¹,

Whittaker²,

Hajek³

et al. 2022

Preprint

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Bedforms preserved in the rock record can provide detailed information on the morphologies and hydrodynamics of ancient fluvial systems on Earth and other planets. Existing processproduct relations for bedform preservation assume that fluvial cross strata reflect conditions under which bedforms were equilibrated with the prevailing flow, i.e., steady-state conditions. However, recent theoretical and experimental observations indicate that enhanced bedform preservation can occur in non-steady state, or disequilibrium, conditions, and it is currently unclear how prevalent disequilibrium dynamics are in preserved field-scale fluvial strata. Here we explore whether steady-state assumptions are appropriate for ancient fluvial systems by evaluating the nature of bedform preservation in well studied fluvial deposits of three Late Cretaceous (Turonian and Campanian) geologic formations in central Utah, USA: the Blackhawk Formation, Castlegate Sandstone, and Ferron Sandstone. In the field, we made systematic measurements of cross-set heights to quantify the extent to which preserved cross-sets reflect bedform preservation in steady-state conditions. Across the three formations, unanimously low coefficients of variation in preserved cross-set heights of 0.25-0.5 are inconsistent with bedform preservation in steady-state conditions, and instead point to fluvial systems in which enhanced preservation of bedforms occurred in disequilibrium conditions.Enhanced bedform preservation in fluvial strata can be explained by two independent hypotheses: the effect of flashy flood hydrographs on bedform preservation (flood hypothesis) or bedform preservation in the presence of a morphodynamic hierarchy (hierarchy hypothesis). We estimated bedform turnover timescales to quantitatively assess these competing hypotheses and contextualize their implications. Under the flood hypothesis, field measurements are consistent with enhanced bedform preservation driven by flashy flood hydrographs with flood durations ranging on the order of hours to a few days, which are consistent with perennial fluvial systems subject to heavy rains and tropical storms.Alternatively, under the hierarchy hypothesis, field measurements are consistent with bedform climb angles that range from 10 −2 to 10 −1 , reflecting rapid bar migration. Our work provides a novel way of investigating fluvial discharge variability in the geologic past, and we outline the potential next steps to disentangle the relative controls of flood variability and morphodynamic hierarchy in controlling bedform preservation in ancient fluvial systems.

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

Cited by 27 publications

References 75 publications

High-accuracy UAV photogrammetry of ice sheet dynamics with no ground control

High-accuracy UAV photogrammetry of ice sheet dynamics with no ground control

Physical and biological functioning in Proterozoic rivers: evidence from the archetypal pre-vegetation alluvium of the Torridon Group, NW Scotland

Field evidence for disequilibrium dynamics in preserved fluvial cross-strata: A record of discharge variability or morphodynamic hierarchy?

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