Measurement of the deposition of fine sediments in a channel bed

Chamoun, Sabine; Zordan, Jessica; Cesare, Giovanni De; Franca, Mário J.

doi:10.1016/j.flowmeasinst.2016.06.008

Cited by 9 publications

(11 citation statements)

References 28 publications

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“…Three different grain sizes were used, d 50 = 200 μm (for the uniform grain size tests) and d 50 = 160 and 80 μm (for the sediment mixtures tests). The three grain sizes had the same sediments characteristics, namely, a density of 1,160 kg/m 3 , a coefficient of uniformity (i.e., D 60 /D 10 , where the D 60 and D 10 are the diameters corresponding to 60% and 10% finer in the particle-size distribution) of 1.1 and an irregular shape (checked with an optical microscope, see Chamoun et al, 2016). The mean diameter was chosen to be in the range of noncohesive fine sediment, 62-500 μm, according to Van Rijn (2007).…”

Section: Experimental Designmentioning

confidence: 99%

The Origin of Fine Sediment Determines the Observations of Suspended Sediment Fluxes Under Unsteady Flow Conditions

Juez

Hassan

Franca

2018

Water Resources Research

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Field observations in a wide range of environments have shown that sediment availability is a major control on the suspended sediment observations in streams. Here we examine, via laboratory experiments, how the amount of proximal in‐channel fine sediment storage relative to the upstream fine sediment distal supply influences the observations of suspended sediment concentrations in streams. Experiments under idealized conditions in a laboratory flume with different ratios of proximal and distal sediment supplies were conducted under a varying flow regime. In addition, the role of the sediment particle size of the supplied sediment on suspended sediment observations was explored. The combinations of proximal and distal sediment supply result in multiple responses of the channel bed and sediment quantity within the channel bed, and the responses adjust through aggradation and degradation. The signature of sediment concentration observed at the upstream section of the channel, given by the distal supply, differs from the downstream observations of the total conveyed sediment (distal and proximal), as shown by an in‐phase analysis of sediment concentration‐discharge plots. Furthermore, we show that nonuniform sediment mixtures may result in a change in the direction of the hysteresis observed between sediment concentration and discharge (i.e., from a clockwise hysteresis to a counterclockwise hysteresis). We also demonstrate that the ratio between sediment distal supply and proximal sediment availability modulates the magnitude of the aggradation/degradation processes in the channel reach and thus the joint observations of sediment concentration and discharge.

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Section: Experimental Designmentioning

confidence: 99%

The Origin of Fine Sediment Determines the Observations of Suspended Sediment Fluxes Under Unsteady Flow Conditions

Juez

Hassan

Franca

2018

Water Resources Research

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“…Note that only some of the bottom deposition electrodes are shown. They are placed throughout the flume starting 10-620 cm from the inlet and separated by 10 cm (Chamoun et al 2016c;Oehy 2003).…”

Section: Measurementsmentioning

confidence: 99%

Influence of Operational Timing on the Efficiency of Venting Turbidity Currents

2018

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Reservoir sedimentation is gaining growing attention as dams are aging, due to economic and environmental consequences. Venting of turbidity currents is one of many sediment management techniques, highly recommended when water is in shortage. The venting operation is experimentally investigated using two reservoir bed slopes. The main research questions concern the opening timing of bottom outlets and the duration of venting. The timings tested are relative to the arrival of the current at the outlet. The results showed that in-time venting, synchronized with the arrival of the turbidity current at the outlet, is more efficient than early or late venting. It is recommended to start opening the gates when the turbidity current is around 300 m upstream of the outlet, so that the evacuation is synchronized with the arrival of the current at the dam. Additionally, venting should not be stopped immediately after the end of the turbidity current flow but should instead last for a certain time in order to evacuate the muddy lake depending on the outflow discharge.

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“…De Rooij et al (1999), Oehy (2003) and Chamoun et al (2016c). Deposition is measured in space and time at 62 fixed points of the main flume.…”

Section: Experimental Measurementsmentioning

confidence: 99%

“…Deposition is measured in space and time at 62 fixed points of the main flume. An error analysis (Chamoun et al, 2016c) showed that the total error that can affect the measured thickness of the deposit is around 0.06 mm (zd 10 ). -Temperatures are measured in the head tank and in the main flume before and after the tests for two main reasons: (1) during the tests, these two temperatures should be close enough to keep the density difference solely due to the presence of suspended particles.…”

Section: Experimental Measurementsmentioning

confidence: 99%

Management of turbidity current venting in reservoirs under different bed slopes

Chamoun

Cesare

Schleiss

2017

Journal of Environmental Management

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a b s t r a c tThe lifetime and efficiency of dams is endangered by the process of sedimentation. To ensure the sustainable use of reservoirs, many sediment management techniques exist, among which venting of turbidity currents. Nevertheless, a number of practical questions remain unanswered due to a lack of systematic investigations. The present research introduces venting and evaluates its performance using an experimental model. In the latter, turbidity currents travel on a smooth bed towards the dam and venting is applied through a rectangular bottom outlet. The combined effect of outflow discharge and bed slopes on the sediment release efficiency of venting is studied based on different criteria. Several outflow discharges are tested using three different bed slopes (i.e., 0%, 2.4% and 5.0%). Steeper slopes yield higher venting efficiency. Additionally, the optimal outflow discharge leading to the largest venting efficiency with the lowest water loss increases when moving from the horizontal bed to the inclined positions.

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Measurement of the deposition of fine sediments in a channel bed

Cited by 9 publications

References 28 publications

The Origin of Fine Sediment Determines the Observations of Suspended Sediment Fluxes Under Unsteady Flow Conditions

The Origin of Fine Sediment Determines the Observations of Suspended Sediment Fluxes Under Unsteady Flow Conditions

Influence of Operational Timing on the Efficiency of Venting Turbidity Currents

Management of turbidity current venting in reservoirs under different bed slopes

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