scholarly journals Passive acoustic measurement of bedload grain size distribution using self-generated noise

2018 ◽  
Vol 22 (1) ◽  
pp. 767-787 ◽  
Author(s):  
Teodor Petrut ◽  
Thomas Geay ◽  
Cédric Gervaise ◽  
Philippe Belleudy ◽  
Sebastien Zanker
Keyword(s):  
Grain Size ◽  
Sediment Transport ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Measurement Techniques ◽  
Bedload Transport ◽  
Transport Processes ◽  
Signal Spectrum ◽  
Inversion Method ◽  
Passive Acoustic

Abstract. Monitoring sediment transport processes in rivers is of particular interest to engineers and scientists to assess the stability of rivers and hydraulic structures. Various methods for sediment transport process description were proposed using conventional or surrogate measurement techniques. This paper addresses the topic of the passive acoustic monitoring of bedload transport in rivers and especially the estimation of the bedload grain size distribution from self-generated noise. It discusses the feasibility of linking the acoustic signal spectrum shape to bedload grain sizes involved in elastic impacts with the river bed treated as a massive slab. Bedload grain size distribution is estimated by a regularized algebraic inversion scheme fed with the power spectrum density of river noise estimated from one hydrophone. The inversion methodology relies upon a physical model that predicts the acoustic field generated by the collision between rigid bodies. Here we proposed an analytic model of the acoustic energy spectrum generated by the impacts between a sphere and a slab. The proposed model computes the power spectral density of bedload noise using a linear system of analytic energy spectra weighted by the grain size distribution. The algebraic system of equations is then solved by least square optimization and solution regularization methods. The result of inversion leads directly to the estimation of the bedload grain size distribution. The inversion method was applied to real acoustic data from passive acoustics experiments realized on the Isère River, in France. The inversion of in situ measured spectra reveals good estimations of grain size distribution, fairly close to what was estimated by physical sampling instruments. These results illustrate the potential of the hydrophone technique to be used as a standalone method that could ensure high spatial and temporal resolution measurements for sediment transport in rivers.

scholarly journals Passive Acoustic Measurement of Bedload Grain Size Distribution using the Self-Generated Noise

2017 ◽  
Author(s):  
Teodor I. Petrut ◽  
Thomas Geay ◽  
Cédric Gervaise ◽  
Philippe Belleudy ◽  
Sebastien Zanker
Keyword(s):  
Grain Size ◽  
Sediment Transport ◽  
Power Spectrum ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Bedload Transport ◽  
Transport Processes ◽  
Signal Spectrum ◽  
Inversion Method ◽  
Passive Acoustic

Abstract. Monitoring sediment transport processes in rivers is of particular interest to engineers and scientists to assess the stability of rivers and hydraulic structures. Various methods for sediment transport processes description were proposed using conventional or surrogate measurement techniques. This paper addresses the topic of the passive acoustic monitoring of bedload transport in rivers and especially the estimation of the bedload grain size distribution from self-generated noise. It discusses the feasibility of linking the acoustic signal spectrum shape to bedload-grain sizes involved in elastic impacts with the bed river treated as a massive slab. Bedload grain size distribution is estimated by a regularized algebraic inversion scheme fed with the power spectrum density of river noise estimated from one hydrophone. The inversion methodology relies upon a physical model which predicts the acoustic field generated by the collision between rigid bodies. Here it is proposed an analytic model of the acoustic power spectrum generated by the impacts between a sphere and a slab. The proposed model is written as linear system of analytic power spectra weighted by the grain size distribution. The algebraic system of equations is then solved by least square optimization and solution regularization methods. The result of inversion leads directly to the estimation of the bedload grain size distribution. The inversion method was applied on real acoustic data from passive acoustics experiments realized on the Isère River, in France. The inversion of in situ measured spectra reveals good estimations of grain size distribution, fairly close to what was estimated by physical sampling instruments. These results illustrate the potential of the hydrophone technique to be used as a standalone method that could ensures high spatial and temporal resolution measurements for sediment transport in rivers.

scholarly journals Identifying sediment transport mechanisms from grain size-shape distributions

2019 ◽  
Author(s):  
Johannes Albert van Hateren ◽  
Unze van Buuren ◽  
Sebastiaan Martinus Arens ◽  
Ronald Theodorus van Balen ◽  
Maarten Arnoud Prins
Keyword(s):  
Grain Size ◽  
Spatial Distribution ◽  
Sediment Transport ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Grain Shape ◽  
Transport Processes ◽  
Transport Mechanisms ◽  
Aeolian Transport ◽  
Transport Mode

Abstract. The way in which sediment is transported (creep, saltation, suspension), is traditionally interpreted from grain size distribution characteristics. However, the grain size range associated with transitions from one transport mode to the other is highly variable because it depends on the amount of transport energy available. In this study we present a novel methodology for determination of the sediment transport mode based on grain size and shape data from dynamic image analysis. The data are integrated into grain size-shape distributions and primary components are determined using end-member modelling. In real-world datasets, primary components can be interpreted in terms of different transport mechanisms and/or sediment sources. Accuracy of the method is assessed using artificial datasets with known primary components that are mixed in known proportions. The results show that the proposed technique accurately identifies primary components with the exception of those primary components that only form minor contributions to the samples (highly mixed components). The new method is also tested on sediment samples from an active aeolian system in the Dutch coastal dunes. Aeolian transport processes and geomorphology of these type of systems are well known and can therefore be linked to the spatial distribution of end members to assess the physical significance of the method's output. The grain size-shape distributions of the dune dataset are unmixed into three primary components. The spatial distribution of these components is constrained by geomorphology and reflects the three dominant aeolian transport processes known to occur along a beach-dune transect: bedload on the beach and in notches that were dug by man through the shore-parallel foredune ridge, modified saltation on the windward and leeward slope of the intact foredune, and suspension in the vegetated hinterland. The three transport modes are characterised by distinctly different trends in grain shape with grain size: with increasing size, bedload shows a constant grain regularity, modified saltation a minor decrease in grain regularity and suspension a strong decrease in grain regularity. These trends, or in other words, the shape of the grain size-shape distributions, can be used to determine the transport mode responsible for a sediment deposit. Results of the method are therefore less ambiguous than those of traditional grain-size distribution end-member modelling, especially if multiple transport modes occur or if primary components overlap in terms of grain size but differ in grain shape.

scholarly journals Identifying sediment transport mechanisms from grain size–shape distributions, applied to aeolian sediments

2020 ◽  
Vol 8 (2) ◽  
pp. 527-553
Author(s):  
Johannes Albert van Hateren ◽  
Unze van Buuren ◽  
Sebastiaan Martinus Arens ◽  
Ronald Theodorus van Balen ◽  
Maarten Arnoud Prins
Keyword(s):  
Grain Size ◽  
Spatial Distribution ◽  
Sediment Transport ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Grain Shape ◽  
Transport Processes ◽  
Transport Mechanisms ◽  
Aeolian Transport ◽  
Transport Mode

Abstract. The way in which sediment is transported (creep, saltation, suspension), is traditionally interpreted from grain size distribution characteristics. However, the grain size range associated with transitions from one transport mode to the other is highly variable because it depends on the amount of transport energy available. In this study we present a novel methodology for determination of the sediment transport mode based on grain size and shape data from dynamic image analysis. The data are integrated into grain size–shape distributions, and primary components are determined using endmember modelling. In real-world datasets, primary components can be interpreted in terms of different transport mechanisms and/or sediment sources. Accuracy of the method is assessed using artificial datasets with known primary components that are mixed in known proportions. The results show that the proposed technique accurately identifies primary components, with the exception of those primary components that only form minor contributions to the samples (highly mixed components). The new method is tested on sediment samples from an active aeolian system in the Dutch coastal dunes. Aeolian transport processes and geomorphology of these type of systems are well known and can therefore be linked to the spatial distribution of endmembers to assess the physical significance of the method's output. The grain size–shape distributions of the aeolian dune dataset are unmixed into three primary components. The spatial distribution of these components is constrained by geomorphology and reflects the three dominant aeolian transport processes known to occur along a beach–dune transect: bedload on the beach and in notches that were dug by man through the shore-parallel foredune ridge, modified saltation on the windward and leeward slope of the intact foredune, and suspension in the vegetated hinterland. The three transport modes are characterised by distinctly different trends in grain shape with grain size: with increasing size, bedload shows a constant grain regularity, modified saltation a minor decrease in grain regularity, and suspension a strong decrease in grain regularity. These trends, or in other words, the shape of the grain size–shape distributions, can be used to determine the transport mode responsible for an aeolian sediment deposit. Results of the method are therefore less ambiguous than those of traditional grain size distribution endmember modelling, especially if multiple transport modes occur or if primary components overlap in terms of grain size but differ in grain shape.

A 25-kyr record of East African monsoon variability: Insights from grain-size distributions and end-member modeling of siliciclastic sediments from Lake Chala

2020 ◽  
Author(s):  
Inka Meyer ◽  
Maarten Van Daele ◽  
Niels Thange ◽  
Dirk Verschuren ◽  
Marc De Batist
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
East Africa ◽  
Grain Size Distribution ◽  
Transport Processes ◽  
Monsoon Circulation ◽  
East African ◽  
African Monsoon ◽  
Sediment Fraction ◽  
End Members

<p>Terrigenous particles deposited in all kinds of sedimentary records (terrestrial, marine and lacustrine) have proven to yield valuable information for reconstruction of paleo-climate and paleo-environments. Natural sediments typically represent a mixture of deposits of diverse provenance, potentially supplied by different transport processes, expressed in a bi-or poly-modal grain-size distribution. Recently, complex mathematical-statistical end-member models have been developed to disentangle the different sub-populations within one grain-size distribution, which are then assumed to represent a distinct sediment fraction that has a single provenance and/or was transported by the same process to the site of deposition.</p><p>Here we present end-member modeling results of the terrigenous sediment fraction in a 25-kyr sediment sequence from Lake Chala (Kenya/Tanzania), revealing valuable information on climate and environmental change in equatorial East Africa since the Last Glacial Maximum (LGM). Calculated end members could be related to distinct source areas and transport processes, namely to fine aeolian dust, fine-grained soil runoff, coarser aeolian dust from proximal sources and coarse erosive material originating from the crater rim surrounding the lake. Variations in the occurrence of distal versus proximal dust is suggested to be a reliable indicator for changes in East African monsoon circulation. During Northern Hemisphere cold periods, such as the LGM and Younger Dryas (YD), wind systems associated with the Intertropical Convergence Zone (ITCZ) were pushed southward, causing a more intense influence of the NE monsoon at Lake Chala. This resulted in high amounts of fine dust originating from the Horn of Africa region. At the same time, SE monsoon circulation was diminished due to a reduced atmospheric pressure gradient between the Asian/Indian continent and the Indian Ocean. Influx of coarse dust from proximal sources, which are mostly located east of Lake Chala, was impossible due to the weaker SE monsoon circulation. After termination of the YD, rapid reestablishment of the SE monsoon in the Early Holocene is recorded by an abrupt increase in the influx of coarse dust.</p><p>Lake Chala sediments contain one of the few continuous and high-resolution climate records in East Africa spanning the past 25 kyr, providing detailed information on long-term climate variation in an area highly sensitive to hydrological variations. Subdividing the clastic sediment fraction into statistically robust end members produces multiple quantitative and independent proxies to help reconstruct this region’s climate and environmental history.</p>

scholarly journals Sediment transport modelling in riverine environments: on the importance of grain-size distribution, sediment density and boundary conditions

2018 ◽  
Author(s):  
Jérémy Lepesqueur ◽  
Renaud Hostache ◽  
Núria Martínez-Carreras ◽  
Emmanuelle Montargès-Pelletier ◽  
Christophe Hissler
Keyword(s):  
Grain Size ◽  
Sediment Transport ◽  
Size Distribution ◽  
Suspended Sediment ◽  
Grain Size Distribution ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Small Scale ◽  
Sediment Grain Size ◽  
Model Based

Abstract. Hydromorphodynamic models are powerful tools to predict the potential mobilization and transport of sediment in river ecosystems. Recent studies even showed that they are able to satisfyingly predict suspended sediment matter concentration in small river systems. However, modelling exercises often neglect suspended sediment properties (e.g. particle site distribution and density), even though such properties are known to directly control the sediment particle dynamics in the water column during rising and flood events. This study has two objectives. On the one hand, it aims at further developing an existing hydromorphodynamic model based on the dynamic coupling of TELEMAC-3D (v7p1) and SISYPHE (v7p1) in order to enable an enhanced parameterisation of the sediment grain size distribution with distributed sediment density. On the other hand, it aims at evaluating and discussing the added-value of the new development for improving sediment transport and riverbed evolution predictions. To this end, we evaluate the sensitivity of the model to sediment grain size distribution, sediment density and suspended sediment concentration at the upstream boundary condition. As a test case, the model is used to simulate a flood event in a small scale river, the Orne River in North-eastern France. The results show substantial discrepancies in bathymetry evolution depending on the model setup. Moreover, the sediment model based on an enhanced sediment grain size distribution (10 classes) and with distributed sediment density outperforms the model with only two sediment grain size classes in terms of simulated suspended sediment concentration.

scholarly journals Estimation of Bed Load Transport in River Osun, South-Western of Nigeria Using Grain Size Distribution Data

2020 ◽  
Vol 2 (2) ◽  
Author(s):  
O.S. Olaniyan
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Bedload Transport ◽  
Cross Sectional Area ◽  
Sediment Supply ◽  
Distribution Data ◽  
Sectional Area ◽  
Cross Sectional ◽  
Standard Methods

Sediment transport rate depends on bed composition, flow hydraulics and sediment supply. There is a paucity of information on bedload transport in River Osun. In this study, bedload in River Osun was estimated using grain size distribution data to predict channel migration and mitigate flooding. Grab sampler was used to collect sediment samples at the sampling point across the river designated as T1-T4. Sieve analysis was carried out in triplicate on sediment from sampling points using standard methods. Discharge and cross-sectional area were measured between December 2017 and December 2018 at sampling stations using standard methods. The seasonal and bedload were estimated using standards equations. The percentage of bed material particles above 5mm and less than or equal to 2mm were 50 and 22.49%, respectively. The average median grain (d50) size was 2.4mm. The discharge and cross-sectional area across River Osun ranged (0.53-17.46) m3/s and (3.83-47.46) m2. The seasonal suspended and bedload across the river were (206.43×103 kg/annum) and 2,538.77×103(kg/annum), respectively. The estimated sediment load of River Osun could be useful in determining the dredging period at any point across the river where deposition of sediment could be monitored.

scholarly journals Grain‐size distribution and propagation effects on seismic signals generated by bedload transport

2021 ◽  
Author(s):  
Sophie Lagarde ◽  
Michael Dietze ◽  
Florent Gimbert ◽  
Jonathan B. Laronne ◽  
Jens M. Turowski ◽  
...  
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Bedload Transport ◽  
Seismic Signals ◽  
Propagation Effects

scholarly journals Fluvial response to changes in the magnitude and frequency of sediment supply in a 1-D model

2018 ◽  
Vol 6 (4) ◽  
pp. 1041-1057 ◽  
Author(s):  
Tobias Müller ◽  
Marwan A. Hassan
Keyword(s):  
Grain Size ◽  
Sediment Transport ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
High Frequency ◽  
Sediment Supply ◽  
Pulse Period ◽  
Flume Experiments ◽  
Evacuation Time ◽  
D Model

Abstract. In steep headwater reaches, episodic mass movements can deliver large volumes of sediment to fluvial channels. If these inputs of sediment occur with a high frequency and magnitude, the capacity of the stream to rework the supplied material can be exceeded for a significant amount of time. To study the equilibrium conditions in a channel following different episodic sediment supply regimes (defined by grain size distribution, frequency, and magnitude of events), we simulate sediment transport through an idealized reach with our numerical 1-D model “BESMo” (Bedload Scenario Model). The model performs well in replicating flume experiments of a similar scope (where sediment was fed constantly, in one, two, or four pulses) and allowed the exploration of alternative event sequences. We show that in these experiments, the order of events is not important in the long term, as the channel quickly recovers even from high magnitude events. In longer equilibrium simulations, we imposed different supply regimes on a channel, which after some time leads to an adjustment of slope, grain size, and sediment transport that is in equilibrium with the respective forcing conditions. We observe two modes of channel adjustment to episodic sediment supply. (1) High-frequency supply regimes lead to equilibrium slopes and armouring ratios that are like conditions in constant-feed simulations. In these cases, the period between pulses is shorter than a “fluvial evacuation time”, which we approximate as the time it takes to export a pulse of sediment under average transport conditions. (2) In low-frequency regimes the pulse period (i.e., recurrence interval) exceeds the “fluvial evacuation time”, leading to higher armouring ratios due to the longer exposure of the bed surface to flow. If the grain size distribution of the bed is fine and armouring weak, the model predicts a decrease in the average channel slope. The ratio between the “fluvial evacuation time” and the pulse period constitutes a threshold that can help to quantify how a system responds to episodic disturbances.

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