Entrapment of fines in coarse sediment beds

Krishnappan, B. G.; Engel, Peter

doi:10.1201/9781439833865.ch85

Cited by 11 publications

(52 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As floc porosity increases with increasing floc size, there is a corresponding decrease in density. Krishnappan and Engel (2006) found that settling velocity increased when flocs were small but above a critical diameter (20µm) and settling velocities decrease with increasing size. Accordingly, Stokes Law cannot be used to estimate the settling velocity of a floc and needs to be measured directly.…”

Section: Nature Of Cohesive Sedimentmentioning

confidence: 99%

“…Using an rotating annular flume, Krishnappan and Engel (2006) demonstrated that floc density decreased as a function of increasing floc size and that particles ~45µm in diameter could have a density similar to that of water. Accordingly, to determine floc settling velocity it is necessary to understand the relationship between particle density and diameter (Lick et al, 1992;Stone and Krishnappan, 2003).…”

Section: Nature Of Cohesive Sedimentmentioning

confidence: 99%

“…Accordingly, under these conditions the clogging layer was removed and the hydraulic conductivity of the bed was increased. Krishnappan and Engel (2006) studied the entrapment potential for gravel beds under both low and high shear stress conditions and found they were similar as a clogging layer did not form. This observation suggests that larger void ratios associated with gravels are sufficient to prevent the formation of a clogged layer under the sediment concentrations used in their study.…”

Section: Entrapment Of Cohesive Sedimentsmentioning

confidence: 99%

“…Initially, these models did not include parameters to represent floc formation and transport. Knowledge of the complex and unique nature of cohesive sediment transport has been predominantly advanced through carefully controlled laboratory studies in flumes (Krishnappan and Engel, 2006). Accordingly, these studies have served to identify and quantify primary processes that govern cohesive sediment transport in aquatic systems.…”

Section: Cohesive Sediment Transport Modelsmentioning

confidence: 99%

“…Because of the need to understand the impacts of cohesive sediment and associated contaminants on aquatic biota (Ankers et al, 2003;Droppo and Stone, 1994) and the physical loss of habitat through infilling of interstitial spaces with cohesive sediment in stream beds (Cobb et al, 1992), an increasing number of recent experimental and field studies have advanced knowledge of cohesive sediment transport and storage mechanisms in aquatic systems (Droppo and Amos, 2001;Packman et al, 2000;Rehg et al, 2005;Stone and Krishnappan, 2003;Krishnappan and Engel, 2006;Krishnappan, 2007). Deposition of cohesive sediment in gravel bed streams can influence pore water chemistry and nutrient cycling (Grimm and Fisher, 1984;Nagorski and Moore, 1999;Worman et al, 2002) as well as alter the porosity and conductivity of stream beds (Packman and MacKay, 2003).…”

Section: Problem Statementmentioning

confidence: 99%

See 4 more Smart Citations

The effect of coarse gravel on cohesive sediment entrapment in an annular flume

Glasbergen¹,

Stone²,

Krishnappan³

et al. 2015

Proc. IAHS

View full text Add to dashboard Cite

Abstract. While cohesive sediment generally represents a small fraction (<0.5%) of the total sediment mass stored in gravel-bed rivers, it can strongly influence physical and biogeochemical processes in the hyporheic zone and alter aquatic habitat. This research was conducted to examine mechanisms governing the interaction of cohesive sediments with gravel beds in the Elbow River, Alberta, Canada. A series of erosion and deposition experiments with and without a gravel bed were conducted in a 5-m diameter annular flume. The critical shear stress for deposition and erosion of cohesive sediment without gravel was 0.115 Pa and 0.212 Pa, respectively. In experiments with a gravel bed, cohesive sediment moved from the water column into the gravel bed via the coupling of surface and pore water flow. Once in the gravel bed, cohesive sediments were not mobilized under the maximum applied shear stresses (1.11 Pa) used in the experiment. The gravel bed had an entrapment coefficient (ratio between the entrapment flux and the settling flux) of 0.2. Accordingly, when flow conditions are sufficient to produce a shear stress that will mobilize the armour layer of the gravel bed (>16 Pa), cohesive materials trapped within the gravel bed will be entrained and transported into the Glenmore Reservoir, where sediment-associated nutrients may pose treatment challenges to the drinking water supply.

show abstract

Section: Nature Of Cohesive Sedimentmentioning

confidence: 99%

Section: Nature Of Cohesive Sedimentmentioning

confidence: 99%

Section: Entrapment Of Cohesive Sedimentsmentioning

confidence: 99%

Section: Cohesive Sediment Transport Modelsmentioning

confidence: 99%

Section: Problem Statementmentioning

confidence: 99%

See 3 more Smart Citations

The effect of coarse gravel on cohesive sediment entrapment in an annular flume

Glasbergen¹,

Stone²,

Krishnappan³

et al. 2015

Proc. IAHS

View full text Add to dashboard Cite

show abstract

Deposition of Suspended Clay to Open and Sand‐Filled Framework Gravel Beds in a Laboratory Flume

Mooneyham

Strom

2018

Water Resources Research

View full text Add to dashboard Cite

Pulses of fine sediment composed of sand, silt, and clay can be introduced to gravel bed rivers through runoff from burn‐impacted hillslopes, landslides, bank failure, or the introduction of reservoir sediment as a result of sluicing or dam decommissioning. Here we present a study aimed at quantifying exchange between suspensions of clay and gravel beds. The questions that motivate the work are: how do bed roughness and pore space characteristics, shear velocity ( u∗), and initial concentration (C0) affect clay deposition on or within gravel beds? Where does deposition within these beds occur, and can deposited clay be resuspended while the gravel is immobile? We examine these questions in a laboratory flume using acrylic, open‐framework gravel, and armored sand‐gravel beds under conditions of varying u∗ and C0. Deposition of clay occurred to all beds (even with Rouse numbers ∼ 0.01). We attribute deposition under full suspension conditions to be an outcome of localized protected zones where clay can settle and available pore space in the bed. For smooth wall cases, protection came from the viscous wall region and the development of bed forms; for the rough beds, protection came from separation zones and low‐velocity pore spaces. Bed porosity was the strongest influencer of nondimensional deposition rate; deposition increased with porosity. Deposition was inversely related to u∗ for the acrylic bed runs; no influence of u∗ was found for the porous bed runs. Increases in discharge resulted in resuspension of clay from acrylic beds; no resuspension was observed in the porous bed runs.

show abstract

Transport of moderately sorted gravel at low bed shear stresses: The role of fine sediment infiltration

Perret

Berni

Camenen

et al. 2018

Earth Surf Processes Landf

View full text Add to dashboard Cite

A reliable estimation of sediment transport in gravel‐bed streams is important for various practical engineering and biological studies (e.g., channel stability design, bed degradation/aggradation, restoration of spawning habitat). In the present work, we report original laboratory experiments investigating the transport of gravel particles at low bed shear stresses. The laboratory tests were conducted under unsteady flow conditions inducing low bed shear stresses, with detailed monitoring of the bed topography using a laser scanner. Effects of bed surface arrangements were documented by testing loose and packed bed configurations. Effects of fine sediments were examined by testing beds with sand, artificial fine sand or cohesive silt infiltrated in the gravel matrix. Analysis of the experimental data revealed that the transport of gravel particles depends upon the bed arrangement, the bed material properties (e.g., size and shape, consolidation index, permeability) and the concentration of fine sediments within the surface layer of moving grains. This concentration is directly related to the distribution of fine particles within the gravel matrix (i.e., bottom‐up infiltration or bridging) and their transport mode (i.e., bedload or suspended load). Compared to loose beds, the mobility of gravel is reduced for packed beds and for beds clogged from the bottom up with cohesive fine sediments; in both cases, the bed shear stress for gravel entrainment increases by about 12%. On the other hand, the mobility of gravel increases significantly (bed shear stress for particle motion decreasing up to 40%) for beds clogged at the surface by non‐cohesive sand particles. Copyright © 2017 John Wiley & Sons, Ltd.

show abstract

Entrapment of fines in coarse sediment beds

Cited by 11 publications

References 9 publications

The effect of coarse gravel on cohesive sediment entrapment in an annular flume

The effect of coarse gravel on cohesive sediment entrapment in an annular flume

Deposition of Suspended Clay to Open and Sand‐Filled Framework Gravel Beds in a Laboratory Flume

Transport of moderately sorted gravel at low bed shear stresses: The role of fine sediment infiltration

Contact Info

Product

Resources

About