Estimating sand bed load in rivers by tracking dunes: a comparison of methods based on bed elevation time series

Leary, Kate; Buscombe, Daniel

doi:10.5194/esurf-8-161-2020

Cited by 25 publications

(48 citation statements)

References 48 publications

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“…However, fluctuations of the sediment thickness are known, primarily induced by sediment input from tributaries that is subsequently redistributed during controlled floods (Grams et al, 2019). Thus, general bedload sediment mobilization ( U m / U c > 1) occurs at least intermittently if not under most flows, indicated by the presence of near‐ubiquitous dunes and the low‐stage bedform migration measurements reported by Leary and Buscombe (2020) in a similar downstream reach. Consequently, regular sediment transport into the frontal scour hole results in partial filling and reduction in d s (Hong et al, 2017).…”

Section: Discussion Of Laboratory Results and Field Evidencementioning

confidence: 74%

Geometry of obstacle marks at instream boulders—integration of laboratory investigations and field observations

Schlömer

Grams

Buscombe

et al. 2021

Earth Surf Processes Landf

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Obstacle marks are instream bedforms, typically composed of an upstream frontal scour hole and a downstream sediment accumulation in the vicinity of an obstacle. Local scouring at infrastructure (e.g. bridge piers) is a well-studied phenomenon in hydraulic engineering, while less attention is given to the time-dependent evolution of frontal scour holes at instream boulders and their geometric relations (depth to width, and length ratio). Furthermore, a comparison between laboratory studies and field observations is rare. Therefore, the morphodynamic importance of such scour features to fluvial sediment transport and morphological change is largely unknown. In this study, obstacle marks at boulder-like obstructions were physically modelled in 30 unscaled process-focused flume experiments (runtime per experiment ≥ 5760 min) at a range of flows (subcritical, clear-water conditions, emergent and submerged water levels) and boundary conditions designed to represent the field setting (i.e. obstacle tilting, and limited thickness of the alluvial layer). Additionally, geometries of scour holes at 90 in-situ boulders (diameter ≥ 1 m) located in a 50-km segment of the Colorado River in Marble Canyon (AZ) were measured from a 1 mresolution digital elevation model. Flume experiments reveal similar evolution of local scouring, irrespective of hydraulic conditions, controlled by the scour incision, whereas the thickness of the alluvial layer and obstacle tilting into the evolving frontal scour hole limit incision. Three temporal evolution phases-(1) rapid incision, (2) decreasing incision, and (3) scour widening-are identified based on statistical analysis of spatiotemporal bed elevation time series. A quantitative model is presented that mechanistically predicts enlargement in local scour length and width based on (1) scour depth, (2) the inclination of scour slopes, and (3) the planform area of the frontal scour hole bottom. The comparison of field observations and laboratory results demonstrates scale invariance of geometry, which implies similitude of processes and form rather than equifinality.

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Section: Discussion Of Laboratory Results and Field Evidencementioning

confidence: 74%

Geometry of obstacle marks at instream boulders—integration of laboratory investigations and field observations

Schlömer

Grams

Buscombe

et al. 2021

Earth Surf Processes Landf

Self Cite

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“…celerity, translational speed) are still scarce, mostly because of technological and cost limitations (Aberle et al, 2012). With the advent of acoustic instrumentation, this information is increasingly available by, for example, applying cross-correlations to a sequence of bedform linear profiles extracted from bathymetric surveys (Engel and Lau, 1981;Leary and Buscombe, 2020). These technological advancements increasingly enable researchers to monitor bedform morphology and dynamics through in-situ experiments.…”

Section: Implementation Considerationsmentioning

confidence: 99%

“…The goal of the transfer is to use AMV processing protocols on time-sequenced acoustic maps acquired from MBES or ADCP bedform surveys to capture the progression of the bedform movement in cross-sectional areas. While production of the acoustic maps is quite mature, the issue of selecting the optimum data acquisition and processing protocols to accurately capture 2-D velocity fields associated with the bedform migration in field conditions is still under scrutiny (Leary and Buscombe, 2020).…”

Section: Introductionmentioning

confidence: 99%

Considerations on Acoustic Mapping Velocimetry (AMV) Application for in-situ Measurement of Bedform Dynamics

You¹,

Muste

Kim

et al. 2021

Front. Water

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Non-intrusive technologies for the in-situ measurement of river morphological features are increasingly popular in the scientific and practice communities due to their efficient and productive data acquisition. While the measurement of suspended load with optical and acoustic technologies is currently an active area of research, the measurement of bedform dynamics has not experienced similar progress. We have successfully demonstrated through laboratory experiments that, by combining acoustic mapping with image velocimetry concepts, we can characterize the planar dynamics of the bedform migration. The technique, labeled Acoustic Mapping Velocimetry (AMV), is currently transferred to field conditions using multiple-beam echo-sounders (MBES) for producing acoustic maps. During this transfer, new questions emerged because, in field conditions, many of the morphologic features targeted by AMV measurements are not a priori known. Moreover, the image velocimetry processing can be approached with several alternatives, each of them characterized by strength and limitations. This paper assembles guidelines for establishing optimal parameters for the acquisition of the acoustic maps based on analytical considerations, and for selecting essential features of the processing for image velocimetry. We test these guidelines using MBES data acquired in the Mississippi River.

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“…steady and unsteady flow), or the downstream migration of dunes, which is of paramount importance to evaluate the bedload transport component. A popular approach involves calculating transport from the geometry and celerity of migrating bedforms, extracted from time series of bed elevation profiles [8]. It is well understandable that any of the former issue related to bed forms presence involve the knowledge of their geometry.…”

Section: Introductionmentioning

confidence: 99%

Semiautomatic Algorithm for the Interpretation of the Bedforms and Statistical Analysis

Schippa

Cavalieri

2021

WIT Transactions on Ecology and the Environment

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This study presents a methodology to simplify the identification of the primary bedforms (mediumlarge dunes) present on a compound riverbed. The paper refers to a field study conducted on a straight free flow reach of an alluvial river (i.e. River Po in Italy) in January 2021. The surveys were carried out employing a multibeam echosounder which allows a large data collection, which was processed realizing river bed DTMs. The identification of the dunes along transects occurs through the implementation of a semiautomatic algorithm able to analyse the bed elevation profiles and to recognize the troughs and the crests of the primary dunes based on the threshold values of length obtained through to a spectral analysis. Once the dunes are recognized, characteristic parameters of the dunes (wavelength, wave height and steepness) are estimated, by which a statistical analysis is carried out to figure out the most frequently recurring dunes on the riverbed. The semiautomatic algorithm proves to be able to handle a large amount of data, providing a reliable interpretation of the riverbed and it is also consistent with results from previous studies. Starting from the present analysis, it is possible to develop the study of the bedforms kinematic that represents a key issue to quantify the volumes of solid bedload transport, in order to cross the typical limitations derived by the traditional bed load sampling methodologies.

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Estimating sand bed load in rivers by tracking dunes: a comparison of methods based on bed elevation time series

Cited by 25 publications

References 48 publications

Geometry of obstacle marks at instream boulders—integration of laboratory investigations and field observations

Geometry of obstacle marks at instream boulders—integration of laboratory investigations and field observations

Considerations on Acoustic Mapping Velocimetry (AMV) Application for in-situ Measurement of Bedform Dynamics

Semiautomatic Algorithm for the Interpretation of the Bedforms and Statistical Analysis

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