scholarly journals Suspended sediment in lowland rivers – towards identifying the ratios of mineral and organic components and their variation during the year

Geologos ◽  
2021 ◽  
Vol 27 (3) ◽  
pp. 173-180
Author(s):  
Katarzyna Skolasińska
Keyword(s):  
Environmental Factors ◽  
Suspended Sediment ◽  
Individual Component ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Lowland Rivers ◽  
Spatial And Temporal Scales ◽  
Suspension Concentration ◽  
Organic Components ◽  
The Impact

Abstract Concentrations of suspended sediment transported by rivers are influenced by interactions between multiple drivers that act on a range of spatial and temporal scales. Such levels vary over the year, as well as across multi-year periods. Most conventional approaches to determining suspended load are based upon analyses of total suspended sediment concentration (SSC), i.e., the sum of mineral and organic matter. This approach makes it difficult, if not impossible, to determine the impact of multiple environmental factors on changes in suspension concentration precisely. The present paper focuses on the mineral and organic components of suspended sediment with the aim of determining how our knowledge of the share of each individual component can improve interpretations of SSC fluctuations during a hydro-logical year. The analysis conducted (personal and other researchers’ results) has shown that mineral and organic suspensions demonstrate mutually incompatible opposite trends under influence of environmental factors. This analysis of organic components identifies clear seasonal trends, which indicates that organic suspensions of autogenous origin have a strong influence on the dynamics of changes in suspension concentration; such analyses are rarely included in assessments of SSC dynamics.

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.

scholarly journals Suspended sediment fluxes in an Indonesian river draining a rainforested basin subject to land cover change

2011 ◽  
Vol 8 (4) ◽  
pp. 7137-7175 ◽  
Author(s):  
F. A. Buschman ◽  
A. J. F. Hoitink ◽  
S. M. de Jong ◽  
P. Hoekstra
Keyword(s):  
Land Cover ◽  
Suspended Sediment ◽  
River Discharge ◽  
Soil Loss ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Sediment Flux ◽  
Sediment Fluxes ◽  
Suspended Sediment Flux ◽  
The Impact

Abstract. Forest clearing for reasons of timber production, open pit mining and the establishment of oil palm plantations generally results in excessively high sediment loads in the tropics. The increasing sediment fluxes pose a threat to coastal marine ecosystems such as coral reefs. This study presents observations of suspended sediment fluxes in the Berau river (Indonesia), which debouches into a coastal ocean that can be considered the preeminent center of coral diversity. The Berau is an example of a small river draining a mountainous, relatively pristine basin that receives abundant rainfall. Flow velocity was measured over a large part of the river width at a station under the influence of tides, using a Horizontal Acoustic Doppler Current Profiler (HADCP). Surrogate measurements of suspended sediment concentration were taken with an Optical Backscatter Sensor (OBS). Tidally averaged suspended sediment concentration increases with river discharge, implying that the tidally averaged suspended sediment flux increases non-linearly with river discharge. Averaged over the 6.5 weeks observations covered by the benchmark survey, the tidally averaged suspended sediment flux was estimated at 2 Mt y−1. Considering the wet conditions during the observation period, this figure may be considered as an upper limit of the yearly averaged flux. This flux is significantly smaller than what could have been expected from the characteristics of the catchment. The consequences of ongoing clearing of rainforest were explored using a plot scale erosion model. When rainforest, which still covered 50–60 % of the basin in 2007, is converted to production land, soil loss is expected to increase with a factor between 10 and 100. If this soil loss is transported seaward as suspended sediment, the increase in suspended sediment flux in the Berau river would impose a severe sediment stress on the global hotspot of coral reef diversity. The impact of land cover changes will largely depend on the degree in which the Berau estuary acts as a sediment trap.

scholarly journals Desilting Basin Efficiency Estimation for Run-of-River Small Hydropower Plants

2019 ◽  
Vol 8 (4) ◽  
pp. 6389-6394
Keyword(s):  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Probabilistic Approach ◽  
Sediment Concentration ◽  
Operational Reliability ◽  
Maintenance Cost ◽  
Mathematical Function ◽  
Small Hydropower ◽  
The Impact ◽  
Run Of River

Suspended sediment concentration and discharge are important factors affecting the operational reliability of run-of-river small hydro power (SHP) plants. Elimination of sediment transported with the flow across the turbines of run-of-river plants is therefore a critical issue for the sustainability of the SHP industry. Comprise of a small diversion weir throughout a stream, the SHP plants does not have space to pile sediments but should be able to divert the incoming bed loads to the river downstream. Sediments in the water entering through the turbines with extreme velocity erode the contact surfaces of turbine mechanisms which results in reduced hydraulic efficiency and increased maintenance cost. Subsequently, desilting basins have become an essential part of the water conductor system of run-of-river SHP to reduce the impact of damage due to suspended sediment. Desilting basins are devised as settling basins to settle sediments larger than a targeted size. They are constructed just after power intake and discharge is despatched through them before pass into the head race tunnel. This study is aimed to estimate the sediment removal efficiency of SHP desilting basins based on data recorded at the intake of a run-of-river SHP. Considering the hydrological variability, probabilistic approach was used to obtain mathematical function for the probability density of suspended sediment concentration (SSC) based on the recorded data.

Analysis of tidal average saturated suspended sediment concentration of cohesive sediment in the Yangtze Estuary

2021 ◽  
Author(s):  
Junyu Tao ◽  
Peng Hu ◽  
Wei Li ◽  
Zhiguo He
Keyword(s):  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Cohesive Sediment ◽  
Yangtze Estuary ◽  
Shear Stresses ◽  
The Yangtze Estuary ◽  
Erosion And Deposition ◽  
Deposition Fluxes ◽  
The Impact

<p>It is generally believed that sediment erosion and deposition can’t occur simultaneously, which is also reflected in the classical Partheniades-Krone formulas used to calculate erosion and deposition flux. In this study, the erosion and deposition fluxes of cohesive sediment are integrated in the tidal period respectively, and when they are equal, the corresponding suspended cohesive sediment concentration is called ‘tidal average saturated concentration of cohesive sediment’. Theoretical analysis of the factors affecting the saturated concentration indicates that a large erosion coefficient results in a high saturated concentration level. The corresponding critical erosion and deposition shear stresses (i.e., τ<sub>e </sub>and τ<sub>d</sub>) at saturated concentration have many possibilities. Therefore, it is understandable that good agreement of suspended sediment concentration between simulation and observation have been obtained by adjusting τ<sub>e </sub>and τ<sub>d </sub>in the previous numerical simulation calibration. According to the relative magnitude of τ<sub>e </sub>and τ<sub>d</sub> at saturated concentration, the erosion and deposition fluxes of cohesive sediment can be divided into four situations: weak erosion (i.e., τ<sub>e  ></sub> τ<sub>d</sub>), intense erosion (i.e., τ<sub>e  <</sub> τ<sub>d</sub>), intense deposition (i.e., τ<sub>e  <</sub> τ<sub>d</sub>), and weak deposition (i.e., τ<sub>e > </sub>τ<sub>d</sub> ). A two-dimensional numerical model is applied to calculate the temporal and spatial variation of the saturated concentration of cohesive sediment in the Yangtze Estuary. Simulation results shows the following findings. 1) The impact of the fraction of the kth size class in the surface (top) layer of bed material on erosion flux of non-uniform cohesive sediment is necessary to be considered. Otherwise, the calculated saturated concentration of cohesive sediment is greater than the measured. 2) The differences between saturated concentration and the field calculated/measured suspended sediment concentration can be applied to infer bed erosion/deposition characteristics to some extent, and compared it with the measured erosion/deposition result, which in turn verifies the values of  τ<sub>e </sub>and τ<sub>d</sub> in the model. This finding provides insights for the following research on transport and diffusion of cohesive sediment in estuary and coastal areas.</p>

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.

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