scholarly journals Influence of lateral embayments on suspended sediment transport under unsteady flow conditions

2018 ◽  
Vol 40 ◽  
pp. 03017 ◽  
Author(s):  
Carmelo Juez ◽  
Matthias Thalmann ◽  
Anton J. Schleiss ◽  
Mário J. Franca
Keyword(s):  
Water Discharge ◽  
Phase Fluctuation ◽  
Sediment Concentration ◽  
High Flow ◽  
Experimental Investigations ◽  
Suspended Sediment Transport ◽  
Fine Sediments ◽  
Sediment Deposits ◽  
Fluctuation Phase ◽  
Flow Phase

Local widening in a channelized river is a common practice in restoration projects. The lateral embayments built for this purpose in the river banks are partially filled up by fine sediments. This allows the formation of aquatic habitats with hydraulic and morphologic diversity. However, the design of these lateral cavities may be compromised by the fluctuations in the water discharge. To address this problem, systematic experimental investigations have been carried out with five different fluctuating hydrograph scenarios. Water depth, sediment concentration and area covered by the settled sediments are analysed in each experiment. The process of sedimentation in the lateral embayments proved to be, in general, resilient to flow fluctuations. However, there were several differences observed during the high flow phase fluctuation phase depending on the geometric configuration of the embayments and the applied hydrograph: (i) a higher peak in discharge means that more sediments are resuspended and a complete remobilization of the in-cavity sediment deposits is possible. (ii) Long and short cavities are more resilient to high flow events than cavities with an intermediate length.

Neural networks approached for modelling river suspended sediment concentration due to tropical storms

2013 ◽  
Vol 11 (4) ◽  
pp. 457-466
Keyword(s):  
Neural Network ◽  
Neural Networks ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Time Series Data ◽  
Water Discharge ◽  
Sediment Concentration ◽  
Series Data ◽  
Generalized Regression Neural Network ◽  
Event Based

Artificial neural networks are one of the advanced technologies employed in hydrology modelling. This paper investigates the potential of two algorithm networks, the feed forward backpropagation (BP) and generalized regression neural network (GRNN) in comparison with the classical regression for modelling the event-based suspended sediment concentration at Jiasian diversion weir in Southern Taiwan. For this study, the hourly time series data comprised of water discharge, turbidity and suspended sediment concentration during the storm events in the year of 2002 are taken into account in the models. The statistical performances comparison showed that both BP and GRNN are superior to the classical regression in the weir sediment modelling. Additionally, the turbidity was found to be a dominant input variable over the water discharge for suspended sediment concentration estimation. Statistically, both neural network models can be successfully applied for the event-based suspended sediment concentration modelling in the weir studied herein when few data are available.

scholarly journals Dissolved and particulate nutrient transport dynamics of a small Irish catchment: the River Owenabue

2014 ◽  
Vol 18 (6) ◽  
pp. 2191-2200 ◽  
Author(s):  
S. T. Harrington ◽  
J. R. Harrington
Keyword(s):  
Suspended Sediment ◽  
Water Discharge ◽  
Nutrient Transport ◽  
Sediment Concentration ◽  
Coefficient Of Determination ◽  
Available Phosphorus ◽  
Nitrogen And Phosphorus ◽  
Particulate Nitrogen ◽  
Monitoring Period ◽  
Nitrogen Concentrations

Abstract. The objective of this research was to investigate the relationship between water and sediment discharge on the transport of nutrients: nitrogen and phosphorus. Water discharge, suspended sediment concentration and dissolved and particulate forms of nitrogen and phosphorus were monitored on the 105 km2 River Owenabue catchment in Ireland. Water discharge was found to have an influence on both particulate and dissolved nutrient transport, but more so for particulate nutrients. The particulate portion of N and P in collected samples was found to be 24 and 39%, respectively. Increased particulate nitrogen concentrations were found at the onset of high discharge events, but did not correlate well to discharge. High concentrations of phosphorus were associated with increased discharge rates and the coefficient of determination (r2) between most forms of phosphorus and both discharge and suspended sediment concentrations were observed to be greater than 0.5. The mean TN yield is 4004 kg km−2 yr−1 for the full 29-month monitoring period with a mean PN yield of 982 kg km−2 yr−1, 25% of the TN yield with the contribution to the yield of PN and PP estimated to be 25 and 53% respectively. These yields represent a PN and PP contribution to the suspended sediment load of 5.6 and 0.28% respectively for the monitoring period. While total nitrogen and total phosphorus levels were similar to other European catchments, levels of bio-available phosphorus were elevated indicating a potential risk of eutrophication within the river.

scholarly journals Pertinent spatio-temporal scale of observation to understand suspended sediment yield control factors in the Andean region: the case of the Santa River (Peru)

2013 ◽  
Vol 17 (11) ◽  
pp. 4641-4657 ◽  
Author(s):  
S. B. Morera ◽  
T. Condom ◽  
P. Vauchel ◽  
J.-L. Guyot ◽  
C. Galvez ◽  
...  
Keyword(s):  
Suspended Sediment ◽  
Spatial Data ◽  
Sediment Yield ◽  
Water Discharge ◽  
Daily Rainfall ◽  
Sediment Concentration ◽  
Suspended Sediment Yield ◽  
Control Factors ◽  
Daily Water ◽  
Spatio Temporal

Abstract. Hydro-sedimentology development is a great challenge in Peru due to limited data as well as sparse and confidential information. This study aimed to quantify and to understand the suspended sediment yield from the west-central Andes Mountains and to identify the main erosion-control factors and their relevance. The Tablachaca River (3132 km2) and the Santa River (6815 km2), located in two adjacent Andes catchments, showed similar statistical daily rainfall and discharge variability but large differences in specific suspended-sediment yield (SSY). In order to investigate the main erosion factors, daily water discharge and suspended sediment concentration (SSC) datasets of the Santa and Tablachaca rivers were analysed. Mining activity in specific lithologies was identified as the major factor that controls the high SSY of the Tablachaca (2204 t km2 yr−1), which is four times greater than the Santa's SSY. These results show that the analysis of control factors of regional SSY at the Andes scale should be done carefully. Indeed, spatial data at kilometric scale and also daily water discharge and SSC time series are needed to define the main erosion factors along the entire Andean range.

Erodibility of fine sediment deposits in gravel bed rivers: investigation of the spatial variability

2021 ◽  
Author(s):  
Hanna Haddad ◽  
Magali Jodeau ◽  
Germain Antoine ◽  
Cédric Legoût
Keyword(s):  
Spatial Variability ◽  
Spatial Organization ◽  
Fine Sediment ◽  
Aquatic Life ◽  
Vegetation Growth ◽  
Gravel Bed ◽  
Fine Sediments ◽  
Sediment Deposits ◽  
Low Altitude ◽  
Gravel Bed Rivers

<p>Fine sediments exhibit various stages of deposition and erosion during their transport from hillslopes to the ocean. In mountainous environments, high fine sediment load during runoff or dam flushing events can lead to important amounts of deposits in gravel bed rivers. Massive deposits may lead to bar elevation, riparian vegetation growth and consequently to bar stabilization, which can increase flood risks. High amount of fine sediment deposits alters also aquatic life and habitat.</p><p>In order to better understand the dynamics of re-suspension of these deposits, and to accurately predict it with numerical modelling, field monitoring campaigns were performed to assess both the spatial variability and the controlling factors of the erodibility of fine deposits. The cohesive strength-meter (CSM) device, a pocket penetrometer and a pocket shear vane were used to evaluate the erodibility of fine sediments deposited in two rivers in the French Alps: The Isère and Galabre.</p><p>The results highlight the specificity of gravel bed rivers with an abundance of areas of deposition of fine sediments, which are discontinuous compared to estuaries and lowland rivers. A high spatial variability of the erodibility was observed and related to the spatial organization of the deposits. The location of the deposit and its elevation, the moisture and the grain sizes are inter-related and have important correlations with the erodibility. Measurements show that high altitude dry deposits and low altitude humid deposits are more easily eroded than intermediate deposits with medium moisture. The measured variables explain part of the variability of the erodibility but other processes such as the history or the origin of the deposit might also be important factors to consider.</p>

scholarly journals Comparative Assessment of Fluvial Suspended Sediment Concentration Analysis Methods

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 873 ◽  
Author(s):  
Flóra Pomázi ◽  
Sándor Baranya
Keyword(s):  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Acoustic Doppler Current Profiler ◽  
Sediment Concentration ◽  
Comparative Assessment ◽  
Danube River ◽  
Suspended Sediment Transport ◽  
Indirect Methods ◽  
Analysis Methods ◽  
Sediment Monitoring

The monitoring of fluvial suspended sediment transport plays an important role in the assessment of morphological processes, river habitats, or many social activities associated with river management. However, establishing and operating a well-functioning sediment monitoring system requires the involvement of advanced indirect methods. This study investigates the advantages and limitations of optical and acoustic devices, to quantify the uncertainties and provide a comprehensive comparative assessment of the investigated indirect methods. The novelty of this study, compared to previous ones, is that four different indirect techniques are parallel tested, i.e., the laser diffraction based LISST-Portable|XR, an infrared based optical instrument, the VELP TB1 turbidimeter, the acoustic based LISST-ABS (Acoustical Backscatter Sensor) sensor, and a 1200 kHz Teledyne RD Instruments Acoustic Doppler Current Profiler (ADCP). The calibration of all the indirect methods was performed based on more than 1000 samples taken from the Hungarian section of the Danube River within a wide suspended sediment concentration range. Implementing a comparative assessment of the different sediment analysis methods, a qualitative and quantitative characterisation of the applicability is provided. Furthermore, a proposal for an optimised sediment monitoring methodology is also suggested.

scholarly journals Field methods of a near-bed suspended sediment experiment in the Yangtze River, China

2020 ◽  
Vol 13 (21) ◽  
Author(s):  
Caiwen Shu ◽  
Guangming Tan ◽  
Yiwei Lv ◽  
Quanxi Xu
Keyword(s):  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Dynamic Equilibrium ◽  
Water Discharge ◽  
Sediment Concentration ◽  
Common Method ◽  
Sediment Discharge ◽  
Improved Method ◽  
The Common ◽  
The Impact

AbstractUsing experimental data of near-bed suspended sediment concentrations at five typical hydrometric stations of the Three Gorges Reservoir at the early reserving stage, the differences were investigated between the common method and improved method during flood seasons and non-flood seasons. The impact of taking measurements below 0.2 times the water depth on the results was discussed. The results show that the average discharges and velocities at each station calculated by the common method were slightly larger than those calculated by the improved method. Regarding the suspended sediment concentration at each station, the errors in the reservoir and downstream channels in dynamic equilibrium state were small, and the largest errors occurred where the river bed was strongly scoured in the downstream reach below the large dam. There was no significant relationship between water discharge and flow velocity, and the missed measurement phenomenon also occurred. The sediment discharge error was affected by the suspended sediment concentration, implying that errors usually occurred in channels with serious erosion during flood seasons. The correction coefficients (R2) of sediment discharge at each station were given during the experiment, which showed that the sediment discharges at the hydrometric stations where a large amount of sediment transport occurred near the river bottom, needed to be modified. Furthermore, the test methods proposed in this study were applied to calculate the sediment discharges of three rivers, and the results indicate that this method can narrow the gap between bathymetric comparisons and sediment load measurements.

On the Suspended Sediment Concentration Profile

2012 ◽  
Vol 212-213 ◽  
pp. 20-24 ◽  
Author(s):  
Chen Cheng ◽  
Zhi Yao Song ◽  
Yi Gang Wang ◽  
Jin Shan Zhang
Keyword(s):  
Boundary Condition ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Order Approximation ◽  
Sediment Concentration ◽  
Suspended Sediment Transport ◽  
Surface Boundary ◽  
Sediment Diffusion Coefficient ◽  
Surface Boundary Condition ◽  
First Order Approximation

After analyzing the surface-boundary condition of suspended sediment concentration (SSC), Cheng et al.[7] further improved the sediment diffusion coefficient which was proposed by Bose and Dey[6]. Then an improved Rouse law (IRL) was developed. This equation, which has a similar form as Rouse law, not only overcomes the zero concentration at the free surface, but also behaves generally better than Rouse law and van Rijn equation over the whole water depth in the verification analysis. In this paper, the surface-boundary condition of SSC is further analyzed. It is elucidated that IRL satisfies the surface-boundary condition more reasonably than Rouse law. In addition, a first-order approximation of IRL is developed. From this approximation, we can easily get the explicit expression of the depth-averaged SSC without any implicit integrals to be solved numerically or by the help of a chart. This is very useful in the further study of non-equilibrium suspended sediment transport (SST).

Introducing surface sampling threshold factor for suspended sediment transport: model development using Sri Lankan tropical highland river basins

2013 ◽  
Vol 46 (1) ◽  
pp. 136-155 ◽  
Author(s):  
Sandun Illangasinghe ◽  
Tilak Hewawasam
Keyword(s):  
Sri Lanka ◽  
Suspended Sediment ◽  
Transport Model ◽  
Low Cost ◽  
Model Development ◽  
Sediment Concentration ◽  
Generic Model ◽  
Suspended Sediment Transport ◽  
Surface Sampling ◽  
Threshold Factor

Estimation of suspended sediment concentration (SSC) in rivers is a prerequisite to address many issues related to hydrology. Therefore, we make an attempt in this study to introduce a low-cost technique to estimate the SSC. Both surface and depth-and-width-integrated water samples were collected and measured for SSC from eight tributaries in Sri Lanka over a complete hydrological year. A site-specific calibration curve was established between SSCs measured by two methods for each tributary where R2 varied from 0.72 to 0.99. The same relationship is developed in general for all tributaries studied in the hilly terrain of Sri Lanka. This generic model exhibits a strong correlation (R2 = 0.91), which will be useful to calculate an accurate SSC from a simply measured surface SSC. To select the appropriate gauging method, be it surface or depth-and-width-integrated sampling, a new concept of surface sampling threshold factor (SSTF) is introduced. The preliminarily analysis on SSTF using available data for the studied catchments reveals that surface sampling is only adequate for estimating a representative SSC if SSTF varies from 35 to 45. When SSTF deviates from this range, the SSC measured by surface sampling needs to be adjusted by depth-and-width-integrated sampling.

Landscape and river self-organization limit the flux of fine particles

2020 ◽  
Author(s):  
Colin Phillips ◽  
Carlos Rogéliz ◽  
Daniel Horton ◽  
Jonathan Higgins ◽  
Aaron Packman
Keyword(s):  
Suspended Sediment ◽  
Fine Particle ◽  
River Flow ◽  
Fine Particles ◽  
Strong Support ◽  
Sediment Concentration ◽  
Sediment Flux ◽  
Suspended Sediment Transport ◽  
Erosion Rates ◽  
Suspended Sediment Flux

<p>Fine particles in rivers comprise a substantial fraction (>50%) of the mass leaving a landscape, while at shorter timescales they represent significant carriers of nutrients and contaminants with the potential to both degrade and enhance aquatic habitats. Predicting fine particle dynamics within rivers remains challenging due to a complex relationship between sediment and water availability from the landscape. This inherent complexity results in watershed-specific understandings of suspended sediment dynamics, typically parameterized as empirical functions of catchment land use, geology, and climate. However, observations of significant fine particle storage within river corridors may indicate that the flux of suspended sediment depends on reach-scale hydraulics. To better understand these dynamics, we synthesized over 40 years of suspended sediment concentration (SSC), hydraulic geometry, river flow, and grainsize data collected by the US Geological Survey from hundreds of rivers spanning a large variety of environments across the continental United States. This data synthesis reveals a strong nonlinear trend between reach-scale hydraulics and the suspended sediment flux, with a secondary dependence on particle properties. The multi-site synthesis reveals that by normalizing the suspended sediment flux by the bankfull shear stress and flux results in a collapse of the observed data onto a single function that describes a self-organizing structure for suspended sediment transport in watersheds. This general relationship indicates strong support for the role of autogenic processes in setting the flux of fine particles and erosion rates of watersheds.</p>

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