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.

Modeling shelter abundance for juvenile Atlantic salmon in a residual flow reach of a hydro power plant using SSIIM 2

2021 ◽  
Author(s):  
Spyros Pritsis ◽  
Nils Ruther ◽  
Kordula Schwarzwälder ◽  
Anastasios Stamou
Keyword(s):  
Grain Size ◽  
Atlantic Salmon ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Sediment Supply ◽  
Substrate Composition ◽  
Juvenile Atlantic Salmon ◽  
River Reach ◽  
Bed Changes ◽  
Shelter Availability

<p>Nowadays, the aquatic biodiversity is highly under pressure due to anthropogenic changes of the rivers such hydraulic structures changing the diversity of flow and aquatic fauna as well as sediment continuity. This can have severe consequences on the fish population in the river reach. Fish are strongly depending on a certain substrate composition throughout all their life stages. Juveniles for example are depending on a certain availability of shelter in the substrate in order to survive this stage.</p><p>Therefore, we investigate the effects of changes in the sediment composition at a hydropower plant in Switzerland on the availability of potential shelter for juvenile fish. By utilizing the observed correlation between parameters describing the fine tail of a riverbed’s grain size distribution and shelter abundance for juvenile Atlantic salmon, we predict the available shelter in a river reach by using a 3D hydrodynamic numerical model directly coupled to a morphodynamic model. The initial substrate composition was assumed to be spatially uniform, its parameters based on a grain size distribution curve derived from collected sediment samples.</p><p>This model can now be used for habitat improvement scenario modeling. Based on the assumption that a specific mixture of sediment coming from upstream travelling through the river reach will positively influence the potential shelter availability, different scenarios can be investigated. The baseline for comparison was the simulation of the bed changes without any sediment supply from upstream. The baseline discharge was set to 100 m<sup>3</sup> /s and was applied for 24 hours. The resulting bed changes create a map of the potential shelter availability of this grain size mixture. Then, two scenarios with sediment inflow from the upstream boundary were simulated. One coarse and one fine mixture of sediment were chosen as inputs, with the goal of investigating their impact on shelter abundance. The former designed to have a positive effect while the latter expected to reduce interstitial voids in the substrate and have a negative effect on available shelter.</p><p>The investigation is conducted as part of the EU Horizon 2020 funded project FIThydro (funded under 727830)</p>

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.

In-line Monitoring of Grain Size Distribution of Channel Poly Si used in 3D NAND Flash Memory Devices using Multiwavelength Raman Spectroscopy

MRS Advances ◽  
2016 ◽  
Vol 1 (5) ◽  
pp. 339-348 ◽  
Author(s):  
Noh Yeal Kwak ◽  
Chul Young Ham ◽  
Min Sung Ko ◽  
Sung Chul Shin ◽  
Seung Jin Yeom ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Flash Memory ◽  
Memory Devices ◽  
Nand Flash ◽  
Nand Flash Memory ◽  
Cross Sectional ◽  
Monitoring Technique

ABSTRACTFeasibility of multiwavelength Raman spectroscopy was studied as a potential in-line monitoring technique for grain size distribution in channel poly-Si used in three dimensional stacked NAND (3D NAND) Flash memory devices. Various channel poly-Si materials in 3D-NAND Flash memory devices, converted from chemical vapor deposition (CVD) grown a-Si, were characterized using non-contact, multiwavelength Raman spectroscopy and high resolution cross-sectional transmission electron microscopy (HRXTEM). The Raman characterization results were compared with HRXTEM images. The correlation between the grain size distribution characterized by multiwavelength Raman spectroscopy and “on current” (ION) of 3D NAND Flash memory devices was investigated. Good correlation between these techniques was seen. Multiwavelength Raman spectroscopy is very promising as a non-destructive in-line monitoring technique for grain size distribution in channel poly-Si used in 3D NAND Flash memory devices.

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.

scholarly journals Temporal variations of bed load transport rate and the grain size distribution of non-uniform size sediment during a constant flow rates

2018 ◽  
Vol 195 ◽  
pp. 05001
Author(s):  
Yusron Saadi ◽  
Ida Bagus Giri Putra ◽  
Agus Suroso
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Sampling Period ◽  
Degradation Process ◽  
Temporal Variations ◽  
Bedload Transport ◽  
Transport Rate ◽  
Uniform Size ◽  
Short Period

Bedload transport rates at a point using both laboratory and field measurement vary with time, from almost zero to several folds of the mean rate. The need to carry out point measurements over a sufficiently long sampling period is very important to cover inconsistency in the transport rate during a short period of observation. In this experiment the bedload was collected at a slot type sediment trap with ten-minute intervals throughout the tests. The aim was to examine the behaviour of mixed grain size sediment transportation during constant flowrates. Two hydrographs were applied to quantify the transport mode changes caused by an increase in time length as the mixtures were continuously exposed to the flow. It shows that intense bed degradation process occurred within three hours of the tests as indicated by almost identical rates of bedload transport during this period and the diminishing rate in the remaining hours. This reflects that a stable bed was achieved after three hours in which the armouring process was believed to take place. The grain size distribution suggests that the proportion of fine mode was relatively stable and the modal grain size of this mode experienced a similar pattern throughout the tests whilst the coarse mode was inconsistent and varied periodically.

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

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.

scholarly journals Comparison between experimental and numerical stratigraphy emplaced by a prograding delta

2014 ◽  
Vol 2 (1) ◽  
pp. 323-338 ◽  
Author(s):  
E. Viparelli ◽  
A. Blom ◽  
C. Ferrer-Boix ◽  
R. Kuprenas
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Mass Conservation ◽  
Bedload Transport ◽  
Experimental Results ◽  
Delta Front ◽  
One Dimensional ◽  
Future Studies ◽  
Base Level

Abstract. A one-dimensional model that is able to store the stratigraphy emplaced by a prograding delta is validated against experimental results. The laboratory experiment describes the migration of a Gilbert delta on a sloping basement into standing water, i.e., a condition in which the stratigraphy emplaced by the delta front is entirely stored in the deposit. The migration of the delta front and the deposition on the delta top are modeled with total and grain-size-based mass conservation models. The vertical sorting on the delta front is modeled with a lee-face-sorting model as a function of the grain size distribution of the sediment deposited at the brinkpoint, i.e., at the downstream end of the delta top. Notwithstanding the errors associated with the grain-size-specific bedload transport formulation, the comparison between numerical and experimental results shows that the model is able to reasonably describe the progradation of the delta front, the frictional resistances on the delta top, and the overall grain size distribution of the delta top and delta front deposits. Further validation of the model in the case of variable base level is currently in progress to allow for future studies, at field and laboratory scale, on how the delta stratigraphy is affected by different changes of relative base level.

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.

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