scholarly journals DYNAMICS OF SILT IN ESTUARY, RESIDUAL CURRENT OR FLOCCULATION WHICH PREVAILS?

1980 ◽  
Vol 1 (17) ◽  
pp. 169 ◽  
Author(s):  
J.P. Lepetit ◽  
M. Davesne
Keyword(s):  
Suspended Sediment ◽  
Salt Water ◽  
Suspended Sediments ◽  
Null Point ◽  
Turbidity Maximum ◽  
Upstream Migration ◽  
Salinity Intrusion ◽  
Natural Sediment ◽  
Residual Currents ◽  
Fine Suspended Sediment

The transport of fine suspended sediment in a partly-mixed estuary has been simulated on a physical model of a schematic estuary reproducing the main geometrical and hydrodynamical characteristics of the Gironde Estuary (France). The natural sediment consisting of silt and clay is simulated using a light and fine material, gilsonite, and the flocculation-'processes in salt water and under turbulence induced by tidal currents have been reproduced by adding in salt water a flocculating salt solution (sodium pyrophosphate). Then the formation of the turbidity maximum surveyed in the field and its upstream-downstream migration in response to varying river discharge have been successfully simulated and the results of different series of tests lead to the following conclusions : - flocculation processes - which are responsible of the variation of the settling velocity with salinity and turbulence-have to be reproduced to explain the formation of the turbidity maximum ; - after high river discharges the convergence of bottom residual currents (null point) due to the salinity intrusion creates a trap for suspended sediments supplied by the river flood which accumulate in the form of the turbidity maximum. Without salinity intrusion, a large amount of sediment would escape out of the estuary to the sea ; - during low river flows, a part of the suspended sediment migrates upstream but the amplitude of this migration is small compared with the displacement of the upstream limit of the salinity intrusion ; - the upstream migration of the turbidity maximum-is increased when a transverse bottom morphology (existence of a deeper navigation channel) is represented.

scholarly journals Curvas-chave de descargas de sedimentos em suspensão no Baixo São Francisco

2020 ◽  
Vol 13 (3) ◽  
pp. 1248 ◽  
Author(s):  
Solange Cavalcanti de Melo ◽  
José Coelho de Araújo Filho ◽  
Renata Maria Caminha Mendes de Oliveira Carvalho
Keyword(s):  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Suspended Sediments ◽  
Sediment Concentration ◽  
Gradual Reduction ◽  
Sao Francisco River ◽  
Sediment Loads ◽  
São Francisco River ◽  
Historical Series ◽  
Suspended Sediment Concentrations

RESUMOO conhecimento da análise quantitativa das concentrações de sedimentos em suspensão transportados pelo rio São Francisco bem como sua relação com as vazões é de muita importância, pois pode auxiliar na identificação dos efeitos da intervenção humana e ou ocasionados pelas condições naturais da região. As regiões a jusante dos barramentos no rio São Francisco apresentam como principal consequência a regularização das vazões e a diminuição das concentrações de sedimentos. O objetivo da pesquisa foi determinar as curvas-chave de sedimentos em suspensão (CCS) nas estações fluviométricas instaladas no Baixo São Francisco (BSF) após a barragem de Xingó. Para o estabelecimento dessas curvas foram utilizados dados de vazão e concentração de sedimentos em suspensão, obtidos do sistema Hidroweb no site da Agência Nacional da Água (ANA) no período de 1999 a 2018. Foram obtidas CCS para todo o trecho do BSF as quais apresentaram bons coeficientes de determinação. Na análise dos dados também foi possível perceber que nos últimos anos, desde 2013 houve redução gradativa das vazões disponibilizadas na barragem de Xingó. Consequentemente, houve também a redução gradativa das cargas de sedimentos em suspensão geradas nas estações de Piranhas, Traipu e Propriá, ou seja, os menores valores já registrados no BSF correspondendo as menores séries históricas tanto de vazão como de sedimentos em suspensão.  Keys curves of sediment discharges in suspension in the Lower São Francisco A B S T R A C TThe knowledge of the quantitative analysis of suspended sediment concentrations carried by the São Francisco River as well as its relation with the flows is of great importance, since it can help in the identification of the effects of human intervention and/or caused by the natural conditions of the region. In the downstream regions of the São Francisco riverbanks, the main consequence was the regularization of flow rates and the reduction of sediment concentrations. The objective of the research was to determine the key curves of suspended sediments (CCS) at the fluviometric stations installed in the lower São Francisco river after Xingó dam. For the evaluation, flow data and suspended sediment concentration were used. These data were obtained from the Hidroweb system on the website of the National Water Agency (ANA) from 1999 to 2018. CCS were plotted for all stretches and presented good coefficients of determination (R2). Based on the analysis of the data it was also possible to notice that in recent years, since 2013 there has been a gradual reduction of the flows available in the Xingó dam. Consequently, there was also a gradual reduction of suspended sediment loads generated at the Piranhas, Traipu and Propriá stations, that is, the lowest values already recorded in lower São Francisco, corresponding to the lower historical series of both discharge and suspended sediments.Keywords: dam, flow, sediments 

scholarly journals Suspended Sediment Analysis: Case Study of Berounka Sources

Geografie ◽  
1997 ◽  
Vol 102 (2) ◽  
pp. 130-138
Author(s):  
Zdeněk Kliment ◽  
Jan Kopp
Keyword(s):  
Seasonal Variation ◽  
Sediment Transport ◽  
Suspended Sediment ◽  
Inorganic Material ◽  
Suspended Sediments ◽  
Suspended Load ◽  
Suspended Sediment Transport ◽  
Sediment Analysis ◽  
Load Characteristics

The article examines suspended sediment transport in Mže, Radbuza, and Úhlava Rivers over the period 1989-95. Data on suspended sediments was collected at five observing sites. The research has been carried out in collaboration with Czech Hydrometeorological Institute, Plzeň. Apart from the suspended load characteristics also the seasonal variation of suspended sediments, siltation of Hracholusky and České Údolí Lakes, and the share of inorganic material in suspended sediments have been examined.

Inferring suspended sediment carbon content and particle size at high frequency from the optical response of a submerged spectrometer 

2021 ◽  
Author(s):  
Dhruv Sehgal ◽  
Núria Martínez-Carreras ◽  
Christophe Hissler ◽  
Victor Bense ◽  
AJF (Ton) Hoitink
Keyword(s):  
Particle Size ◽  
Absorption Spectrum ◽  
Carbon Content ◽  
Suspended Sediment ◽  
High Frequency ◽  
Suspended Sediments ◽  
Ex Situ ◽  
Frequency Measurements ◽  
Component Form

<p>Manual and unattended sampling in the field and laboratory analysis are common practices to measure suspended sediment (SS) carbon content and particle size. However, one of the major drawbacks of these ex-situ methods is that they make high frequency measurements challenging. This includes restricted data collection due to limited access to the sampling locations during turbulent conditions or high flows, when the largest amount of sediments is transported downstream, introducing uncertainty in quantification of SS properties (particle size and carbon content) and sediment loads. Knowledge on SS carbon content and particle size is also important to better understand the multi-component form of suspended sediments (i.e. flocs) that directly affect sediment transport and other sediment properties (e.g. settling velocity and density). Moreover, SS carbon content and particle size exert an impact on the optical sensor readings that are traditionally used to measure turbidity. In that respect, high frequency measurements of SS carbon content and particle size could eventually help us to move from ‘local’ calibrations towards ‘global’ dependencies based on in-situ SS characterization.</p><p>In this study, we propose to use a submerged UV-VIS spectrometer to infer SS carbon content and particle size. The sensor measures the entire light absorption spectrum of water between 200 nm and 750 nm at sampling intervals as short as 2-minutes. To this end, we first test our approach under controlled conditions with an experimental laboratory setup consisting of a cylindrical tank (40-L) with an open top. An UV-VIS spectrometer and a LISST-200X sensor (to measure particle size distribution) are installed horizontally. A stirrer facilitates the homogeneous mixing of SS and prevents the settling of heavy particles at the bottom. We use the sediments sampled from 6 sites in Luxembourg with contrasting composition and representing different land use types and geological settings. The sampled sediments were wet sieved into 3 size classes to clearly recognize the effect of particle size on absorption. In our investigation, we use specific wavelengths, chemometric techniques and carbon content specific absorbance indices to infer SS composition and particle size from the absorption spectrum. Results are then validated using in-situ field data from two instrumented field sites in Luxembourg. Amid the challenge of associating laboratory and field results, the preliminary results indicate that the absorption spectrum measured with a submerged UV-VIS spectrometer can be used to estimate SS particle size and carbon content.</p>

scholarly journals Transport Mechanism of Suspended Sediments and Migration Trends of Sediments in the Central Hangzhou Bay

Water ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 2189
Author(s):  
Zekun Song ◽  
Weiyong Shi ◽  
Junbiao Zhang ◽  
Hao Hu ◽  
Feng Zhang ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Suspended Sediments ◽  
Sediment Concentration ◽  
Hangzhou Bay ◽  
The South ◽  
Transport Mode ◽  
Tidal Pumping ◽  
The North

Based on the 2013 field survey data of hydrology, suspended sediments and bottom sediments in the Central Hangzhou Bay, this paper explores the dynamic mechanism of suspended sediments in Hangzhou Bay by employing material flux decomposition. Meanwhile, the migration trends of bed sediments are also investigated by analyzing grain size trends. The results show that during an ebb or flood tide, the hydrograph of suspended sediment concentration of Hangzhou Bay is dominated by an M shape (bimodal), which is attributed primarily to the generation of a soft mud layer and a separate fluid mud layer. Laterally, the distribution of suspended sediment concentration is high in the south and low in the north. From a macroscopic perspective, the net sediment transport in the study area displays a “north-landward and south-seaward” trend, presenting a “C”-shaped transport mode. That is, the sediments are transported from the bay mouth to the bay head on the north side and from the bay head to the bay mouth on the south side. The sediment transports by advection and tidal pumping are predominant, while the sediment transport by vertical circulation makes little contribution to the total sediment transport. Moreover, the sediment transport in the center of the reach area is dominated by advection, whereas that near both sides of the banks is controlled by tidal pumping. The asymmetry of the tides, i.e., flood-dominance in the north and ebb-dominance in the south, is the primary cause of the dynamic mechanism for the overall “C”-shaped transport mode in Hangzhou Bay. Additionally, coupled with the narrow-head wide-mouth geomorphology, Hangzhou Bay remains evolving by south shore silting and north shore scouring.

scholarly journals Vertical Distribution of Suspended Sediments above Dense Plants in Water Flow

Water ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 12 ◽  
Author(s):  
Yanhong Li ◽  
Liquan Xie ◽  
Tsung-chow Su
Keyword(s):  
Vertical Distribution ◽  
Flow Velocity ◽  
Suspended Sediment ◽  
Plant Height ◽  
Water Flow ◽  
Suspended Sediments ◽  
Sediment Concentration ◽  
Turbulent Momentum ◽  
Different Diameters ◽  
Plane Displacement

Plants in natural water flow can improve water quality by adhering and absorbing the fine suspended sediments. Dense plants usually form an additional permeable bottom boundary for the water flow over it. In the flow layer above dense plants, the flow velocity generally presents a zero-plane-displacement and roughness-height double modified semi-logarithmic profile. In addition, the second order shear turbulent moment (or the Reynolds stress) are different from that found in non-vegetated flow. As a result, the turbulent momentum diffusivity of flow and thus the diffusivity of sediment will shift, which will cause the vertical profile of suspended sediment and the corresponding Rouse formula deform. A set of physical experiments with three different diameters of fine suspended sediments was conducted in an indoor water flume. These experiments investigated a new distribution pattern of suspended sediment and the correspondingly deformed Rouse formula in the flow layer over the dense plants. Experimental results showed that above the dense plants, the shear turbulent momentum of flow presented a plant-height modified negative linear profile, which has been proposed by a previous study, and the vertical distribution of fine suspended sediments presented an equilibrium pattern. Based on the plant-modified profiles of flow velocity and the shear turbulent momentum a new zero-plane and plant-height double modified Rouse formula were analytically derived. This double-parameter modified Rouse formula agrees well with the measured profile of suspended sediment concentration experimentally observed in the present study. By adjusting the Prandtl–Schmidt number, i.e., the ratio of sediment diffusivity to flow diffusivity, the double-parameter modified Rouse formula can be applied to submerged dense plant occupied flow.

scholarly journals Suspended Sediment Variability at the Solimões and Negro Confluence between May 2013 and February 2014

Geosciences ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 265 ◽  
Author(s):  
Thiago Marinho ◽  
Naziano Filizola ◽  
Jean-Michel Martinez ◽  
Elisa Armijos ◽  
André Nascimento
Keyword(s):  
Suspended Sediment ◽  
Satellite Images ◽  
Suspended Sediments ◽  
Left Bank ◽  
Sediment Samples ◽  
Negro River ◽  
The World ◽  
The Right ◽  
Sediment Variability ◽  
Solimões River

This study focuses on the confluence of two major rivers of the world, the Solimões River (white waters) and Negro River (black waters). Surface suspended sediment samples (SSC) and spectroradiometer taken along transverse profiles at 500 m intervals over a distance of 10 km, as well as satellite images (MODIS) during the hydrological year, were used to follow suspended sediment variability. In January and February, the confluence is dominated by white waters from the Solimões River in the two banks, and in June and July in the right bank by black waters from the Negro River and in the left bank by clear waters from the Solimões River. We found that indirect tools, such as reflectance obtained by spectrometer or MODIS images, can be used to determine surface suspended sediments in a contrasting zone.

Optical Properties, Suspended Sediments, and Chemistry Associated with the Turbidity Maxima of the Delaware Estuary

1983 ◽  
Vol 40 (S1) ◽  
pp. s172-s179 ◽  
Author(s):  
Robert B. Biggs ◽  
Jonathan H. Sharp ◽  
Thomas M. Church ◽  
John M. Tramontano
Keyword(s):  
Optical Properties ◽  
Trace Metals ◽  
Attenuation Coefficient ◽  
Inorganic Nitrogen ◽  
Suspended Sediments ◽  
Inorganic Phosphorus ◽  
Turbidity Maximum ◽  
Salinity Range ◽  
Delaware Estuary ◽  
High Concentrations

Two turbidity maxima were found in the Delaware Estuary and were distinct both in terms of optical properties of the water and in quantity of suspended material. The upstream maximum occurred at about 1‰ salinity. Both the diffuse attenuation coefficient (KD) and the beam attenuation coefficient (α) responded to the double turbidity maxima. The upstream maximum contains a larger number of individual mineral grains with a mean diameter of about 3 μm; the downstream maximum, which occurred at salinities of 7.5–10‰, was dominated by composite particles with a mean size of 12 μm; at salinities > 10‰, the suspended sediment population was dominated by large (10–20 μm) individual particles with few composite particles.Nutrients, productivity, particulate organic matter, and dissolved and particulate metals all showed relationships to the turbidity maxima when viewed on salinity and on geographic axes. An excess of dissolved inorganic nitrogen in relation to dissolved inorganic phosphorus was mirrored by exceptionally low particulate C/P ratios in the region of the turbidity maxima. Primary productivity appeared to be greatly reduced in the region of the downstream turbidity maximum.The trace metals Fe, Mn, Cd, Cu, Co, and Ni showed a general association with particulate phases at lowest salinities, at the upstream turbidity maximum. The more particle reactive metals (Fe, Mn, and Co) reflected this as enrichment relative to particulate aluminum. At the downstream turbidity maximum, in the mid-salinity range, the trace metals showed a minimum relative to Al, probably due to dilution by resuspended bottom sediments. In the lower estuary, the trace metals exhibited the highest enrichment (relative to aluminum) and an association with high concentrations of particulate carbon.Key words: Delaware Estuary, turbidity maxima, optical properties, suspended sediments, chemistry

scholarly journals Numerical modelling of hydro-morphological processes dominated by fine suspended sediment in a stormwater pond

2018 ◽  
Vol 556 ◽  
pp. 87-99 ◽  
Author(s):  
Mingfu Guan ◽  
Sangaralingam Ahilan ◽  
Dapeng Yu ◽  
Yong Peng ◽  
Nigel Wright
Keyword(s):  
Numerical Modelling ◽  
Suspended Sediment ◽  
Stormwater Pond ◽  
Morphological Processes ◽  
Fine Suspended Sediment
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