scholarly journals Getting information on suspended sediments in a large river from acoustic backscatter

2018 ◽  
Vol 40 ◽  
pp. 04017
Author(s):  
Adrien Vergne ◽  
Céline Berni ◽  
Jérôme Le Coz
Keyword(s):  
Suspended Sediment Concentration ◽  
Spatial Information ◽  
Suspended Sediments ◽  
Sediment Concentration ◽  
Large River ◽  
Acoustic Backscatter ◽  
Qualitative Information ◽  
Sediment Size ◽  
The Common

There has been a growing interest in the last decade in extracting information on Suspended Sediment Concentration (SSC) from acoustic backscatter in rivers. Quantitative techniques are not yet effective, but acoustic backscatter already provides qualitative information on suspended sediments. In particular, in the common case of a bi-modal sediment size distribution, corrected acoustic backscatter can be used to look for sand particles in suspension and provide spatial information on their distribution throughout a river crosssection. This paper presents a case-study where these techniques have been applied.

Acoustic Inversion Method for Profiling Suspended Sediment Concentration

2014 ◽  
Vol 687-691 ◽  
pp. 3980-3983
Author(s):  
Jun Xi Shi ◽  
Min Zhu ◽  
Yan Bo Wu ◽  
Xing Tao Sun
Keyword(s):  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Acoustic Backscatter ◽  
Inversion Method ◽  
Dual Frequency ◽  
Frequency Method ◽  
Backscatter Signal ◽  
Size Profile ◽  
Acoustic Inversion

The concentration of suspended sediment is an important parameter for the research of sediment transport. Acoustic backscatter technique has been employed to measure the concentration of suspended sediment recently. It is an inversion problem to measure the concentration from the backscatter signal. In this paper, an improved dual-frequency method is proposed for the concentration inversion of suspension sediment. It is an explicit solution with much lower computational complexity than the commonly used iterative method and with no requirement of known and constant particle size profile compared to the basic dual-frequency method.

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 Characterizing and modelling the trapping efficiency of sedimentation basins downstream of harvested peat bog

2018 ◽  
Vol 45 (6) ◽  
pp. 478-488 ◽  
Author(s):  
Myriam Samson-Dô ◽  
André St-Hilaire
Keyword(s):  
Suspended Sediment Concentration ◽  
Suspended Sediments ◽  
Sediment Concentration ◽  
Drainage Water ◽  
Organic Content ◽  
Trapping Efficiency ◽  
Peat Moss ◽  
Decomposition Level ◽  
In Series ◽  
Sedimentation Basins

Peat moss harvesting is an important industry in Canada. To harvest peat, the water table of the peatland must be lowered to allow the surficial peat layer to dry and be harvested. Drainage water can contain suspended sediments, so at most harvesting sites, the water is routed through sedimentation basins. This work focuses on characterizing and modelling their trapping efficiency. Eight basins with different volume/watershed area ratios (705 to 4170 m3/km2) were studied in three Quebec regions. Suspended sediment concentration and discharge were monitored up- and downstream of each basin during the ice-free season. Basins with high ratios of volume/drainage area, multiple basin configurations (i.e., two basins in series or in parallel), and those equipped with a flow regulation structure were more efficient than regular basins. Moreover, the nature of sediments (size, decomposition level, and organic content) influences loads, but not the trapping efficiency. Finally, two empirical models developed to predict trapping efficiency of municipal sedimentation basins were tested and adapted for basins that capture peat sediments.

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 What Discharge Is Required to Remove Silt and Sand Downstream from a Dam? An Adaptive Approach on the Selves River, France

Water ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 392 ◽  
Author(s):  
Rémi Loire ◽  
Loïc Grosprêtre ◽  
Jean-René Malavoi ◽  
Olivier Ortiz ◽  
Hervé Piégay
Keyword(s):  
Water Level ◽  
Suspended Sediment Concentration ◽  
Suspended Sediments ◽  
Sediment Concentration ◽  
Small Rivers ◽  
Management Approach ◽  
Sand Transport ◽  
Environmental Objectives ◽  
Operational Information ◽  
Operational Tests

An increasing number of scientific studies are tackling the management of discharges downstream of dams for environmental objectives. Such management is generally complex, and experiments are required for proper implementation. This article present the main lessons from a silt sand removal experiment on a bypassed reach of a dam on the Selves River (164 km²), France. Three four-hour operational tests at maximum discharge (10, 15, and 20 m3/s) were carried out in September 2016 to determine the discharge required for transporting as much silt and sand as possible without remobilizing coarser sediments. In September 2017, an additional flow release was performed over 34 h at 15 m3/s. Suspended sediment concentration and water level were recorded throughout the releases. Monitoring at the reach scale was supplemented by morphological measurements. The results demonstrate that a discharge of approximately 10 m3/s enables significant transport of suspended sediments (SS), whereas a discharge of 15 m3/s enables significant sand transport. The results provide operational information on silt and sand transport applicable to other small rivers. This study represents an important contribution to the relatively sparse existing body of literature regarding the effects of water releases and sediment state. Our study also demonstrates that it is possible to successfully undertake water releases in small rivers with an adaptive management approach.

Experimental Study on Regular Wave-Induced Scour and Settlement of a Submerged Obstacle Upon a Fluidized Sandbed

2010 ◽  
Author(s):  
Shiaw-Yih Tzang ◽  
Yung-Lung Chen ◽  
Shan-Hwei Ou
Keyword(s):  
Fluidized Beds ◽  
Suspended Sediment Concentration ◽  
Suspended Sediments ◽  
Sediment Concentration ◽  
Regular Waves ◽  
Rf Test ◽  
Total Settlement ◽  
Test Soil ◽  
Rectangular Obstacle ◽  
Wave Induced

Bed scouring and structure settlement due to interactions of regular waves and a submerged rectangular obstacle in the shallow water regions upon a fluidized fine sandy bed are experimentally investigated. Both impervious and pervious structures are installed on the test soil bed and synchronous measurements of water surface, bed surface, suspended sediment concentration and pore pressures are carried out at locations upstream and downstream. The measurements illustrate that interactions between waves and structures have relatively mild affects on the bed scouring in an unfluidized response. The interactions become more intense in the fluidized responses with significant wave decay over and increasing suspended sediments near above the fluidized beds oscillating with similar period to the loading waves. Meanwhile, the submerged structure starts to settle into the fluidized bed and significant scouring occurs. The interactions are typically greater in a RF test than in a NRF test. More than 90% of the total settlement occurs in a single event of the RF response so that the impervious and pervious structures become half buried and totally buried after the event. The settlements further affect the interactions of following loading waves and the fluidized beds. As a result, scouring on both sides of the half buried impervious obstacle is greater than those of the totally buried pervious structure.

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