SEDIMENT TRANSPORT IN SMALL DRAINAGE BASINS OF GRANITIC ROCKS FROM THE VIEW POINT OF GRAIN SIZE DISTRIBUTION

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.

Download Full-text

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

10.5194/hess-2018-511 ◽

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.

Download Full-text

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

Earth Surface Dynamics ◽

10.5194/esurf-6-1041-2018 ◽

2018 ◽

Vol 6 (4) ◽

pp. 1041-1057 ◽

Cited By ~ 7

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.

Download Full-text

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

10.5194/esurf-2018-34 ◽

2018 ◽

Author(s):

Tobias Müller ◽

Marwan Hassan

Keyword(s):

Grain Size ◽

Sediment Transport ◽

Size Distribution ◽

Grain Size Distribution ◽

High Frequency ◽

Sediment Supply ◽

Pulse Period ◽

Flume Experiments ◽

Evacuation Time ◽

1D 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 1D model BESMo (Bedload Scenario Model), which was configured using flume experiments with a similar scope. The model performs well in replicating the flume experiments (where sediment was fed constantly, in 1, 2 or 4 pulses) and allowed the exploration of alternative event sequences. We show that in these experiments, the ordering 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 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 lowering 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.

Download Full-text

A 2D hydrodynamic-sedimentological model for gravel-bed rivers. Part I: theory and validation

Journal of Agricultural Engineering ◽

10.4081/jae.2013.263 ◽

2013 ◽

Vol 44 (2s) ◽

Author(s):

Gabriel Kaless ◽

Mario A. Lenzi ◽

Luca Mao

Keyword(s):

Grain Size ◽

Sediment Transport ◽

Size Distribution ◽

Grain Size Distribution ◽

Gravel Bed ◽

Bed Elevation ◽

Shallow Water Flows ◽

Morphological Model ◽

Gravel Bed Rivers ◽

Transported Material

This paper presents a novel 2D-depth average model especially developed for gravel-bed rivers, named Lican-Leufú (Lican=pebble and Leufu=river, in Mapuche’s language, the native inhabitants of Central Patagonia, Argentina). The model consists of three components: a hydrodynamic, a sedimentological, and a morphological model. The flow of water is described by the depth-averaged Reynolds equations for unsteady, free-surface, shallow water flows. It includes the standard k-e model for turbulence closure. Sediment transport can be divided in different size classes (sand-gravel mixture) and the equilibrium approach is used for Exner’s equation. The amour layer is also included in the structure of the model and the surface grain size distribution is also allowed to evolve. The model simulates bank slides that enable channel widening. Models predictions were tested against a flume experiment where a static armour layer was developed under conditions of sediment starvations and general good agreements were found: the model predicted adequately the sediment transport, grain size of transported material, final armour grain size distribution and bed elevation.

Download Full-text

Variations of soil profile characteristics due to varying time spans since ice retreat in the inner Nordfjord, western Norway

Solid Earth ◽

10.5194/se-5-485-2014 ◽

2014 ◽

Vol 5 (1) ◽

pp. 485-498 ◽

Cited By ~ 7

Author(s):

A. Navas ◽

K. Laute ◽

A. A. Beylich ◽

L. Gaspar

Keyword(s):

Grain Size ◽

Size Distribution ◽

Grain Size Distribution ◽

Soil Profile ◽

Mineralogical Composition ◽

Ice Age ◽

Drainage Basins ◽

Western Norway ◽

Ice Retreat ◽

Profile Characteristics

Abstract. In the Erdalen and Bødalen drainage basins located in the inner Nordfjord in western Norway the soils were formed after deglaciation. The climate in the uppermost valley areas is sub-arctic oceanic, and the lithology consists of Precambrian granitic orthogneisses on which Leptosols and Regosols are the most common soils. The Little Ice Age glacier advance affected parts of the valleys with the maximum glacier extent around AD 1750. In this study five sites on moraine and colluvium materials were selected to examine main soil properties, grain size distribution, soil organic carbon and pH to assess if soil profile characteristics and patterns of fallout radionuclides (FRNs) and environmental radionuclides (ERNs) are affected by different stages of ice retreat. The Leptosols on the moraines are shallow, poorly developed and vegetated with moss and small birches. The two selected profiles show different radionuclide activities and grain size distribution. The sampled soils on the colluviums outside the LIA glacier limit became ice-free during the Preboral. The Regosols present better-developed profiles, thicker organic horizons and are fully covered by grasses. Activity of 137Cs and 210Pbex concentrate at the topsoil and decrease sharply with depth. The grain size distribution of these soils also reflects the difference in geomorphic processes that have affected the colluvium sites. Significantly lower mass activities of FRNs were found in soils on the moraines than on colluviums. Variations of ERN activities in the valleys were related to characteristics of soil mineralogical composition. These results indicate differences in soil development that are consistent with the age of ice retreat. In addition, the pattern distribution of 137Cs and 210Pbex activities differs in the soils related to the LIA glacier limits in the drainage basins.

Download Full-text

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

10.5194/hess-2017-171 ◽

2017 ◽

Cited By ~ 1

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.

Download Full-text

THE RELATION BETWEEN LONGSHORE VARIATIONS IN GRAIN SIZE DISTRIBUTION AND SEDIMENT TRANSPORT PROCESSES

Coastal Sediments 2019 ◽

10.1142/9789811204487_0111 ◽

2019 ◽

Author(s):

CAROLINE HALLIN ◽

BJÖRN ALMSTRÖM ◽

MAGNUS LARSON ◽

HANS HANSON

Keyword(s):

Grain Size ◽

Sediment Transport ◽

Size Distribution ◽

Grain Size Distribution ◽

Transport Processes

Download Full-text

Advanced Numerical Modeling of Sediment Transport in Gravel-Bed Rivers

Water ◽

10.3390/w11030550 ◽

2019 ◽

Vol 11 (3) ◽

pp. 550 ◽

Cited By ~ 5

Author(s):

Van Bui ◽

Minh Bui ◽

Peter Rutschmann

Keyword(s):

Grain Size ◽

Sediment Transport ◽

Size Distribution ◽

Grain Size Distribution ◽

Morphological Changes ◽

Relative Size ◽

Size Fraction ◽

New Model ◽

Gravel Bed ◽

Gravel Bed Rivers

Understanding the alterations of gravel bed structures, sediment transport, and the effects on aquatic habitat play an essential role in eco-hydraulic and sediment transport management. In recent years, the evaluation of changes of void in bed materials has attracted more concern. However, analyzing the morphological changes and grain size distribution that are associated with the porosity variations in gravel-bed rivers are still challenging. This study develops a new model using a multi-layer’s concept to simulate morphological changes and grain size distribution, taking into account the porosity variabilities in a gravel-bed river based on the mass conservation for each size fraction and the exchange of fine sediments between the surface and subsurface layers. The Discrete Element Method (DEM) is applied to model infiltration processes and to confirm the effects of the relative size of fine sediment to gravel on the infiltration depth. Further, the exchange rate and the bed porosity are estimated while using empirical formulae. The new model was tested on three straight channels. Analyzing the calculated results and comparing with the observed data show that the new model can successfully simulate sediment transport, grain sorting processes, and bed change in gravel-bed rivers.

Download Full-text