Erodibility of fine sediment deposits in gravel bed rivers: investigation of the spatial variability

Fine sediments exhibit various stages of deposition and erosion during their transport from hillslopes to the ocean. In mountainous environments, high fine sediment load during runoff or dam flushing events can lead to important amounts of deposits in gravel bed rivers. Massive deposits may lead to bar elevation, riparian vegetation growth and consequently to bar stabilization, which can increase flood risks. High amount of fine sediment deposits alters also aquatic life and habitat.In order to better understand the dynamics of re-suspension of these deposits, and to accurately predict it with numerical modelling, field monitoring campaigns were performed to assess both the spatial variability and the controlling factors of the erodibility of fine deposits. The cohesive strength-meter (CSM) device, a pocket penetrometer and a pocket shear vane were used to evaluate the erodibility of fine sediments deposited in two rivers in the French Alps: The Is&#232;re and Galabre.The results highlight the specificity of gravel bed rivers with an abundance of areas of deposition of fine sediments, which are discontinuous compared to estuaries and lowland rivers. A high spatial variability of the erodibility was observed and related to the spatial organization of the deposits. The location of the deposit and its elevation, the moisture and the grain sizes are inter-related and have important correlations with the erodibility. Measurements show that high altitude dry deposits and low altitude humid deposits are more easily eroded than intermediate deposits with medium moisture. The measured variables explain part of the variability of the erodibility but other processes such as the history or the origin of the deposit might also be important factors to consider.

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The Prediction of Fine Sediment Distribution in Gravel-Bed Rivers Using a Combination of DEM and FNN

Water ◽

10.3390/w12061515 ◽

2020 ◽

Vol 12 (6) ◽

pp. 1515

Author(s):

Van Hieu Bui ◽

Minh Duc Bui ◽

Peter Rutschmann

Keyword(s):

Feedforward Neural Networks ◽

Fine Sediment ◽

Sediment Distribution ◽

Gravel Bed ◽

Fine Sediments ◽

Porosity Variation ◽

Sediment Sorting ◽

Gravel Bed Rivers ◽

Bed Material ◽

The Relationship

Large amounts of fine sediment infiltration into void spaces of coarse bed material have the ability to alter the morphodynamics of rivers and their aquatic ecosystems. Modelling the mechanisms of fine sediment infiltration in gravel-bed is therefore of high significance. We proposed a framework for calculating the sediment exchange in two layers. On the basis of the conventional approaches, we derived a two-layer fine sediment sorting, which considers the transportation of fine sediment in the form of infiltration into the void spaces of the gravel-bed. The relationship between the fine sediment exchange and the affected factors was obtained by using the discrete element method (DEM) in combination with feedforward neural networks (FNN). The DEM model was validated and applied for gravel-bed flumes with different sizes of fine sediments. Further, we developed algorithms for extracting information in terms of gravel-bed packing, grain size distribution, and porosity variation. On the basis of the DEM results with this extracted information, we developed an FNN model for fine sediment sorting. Analyzing the calculated results and comparing them with the available measurements showed that our framework can successfully simulate the exchange of fine sediment in gravel-bed rivers.

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Fine sediment deposits in gravel bed rivers: Sensitivity analysis to particle properties using a 2D hydrodynamic and sediment model

River Flow 2020 ◽

10.1201/b22619-162 ◽

2020 ◽

pp. 1163-1171

Author(s):

H. Haddad ◽

M. Jodeau ◽

G. Antoine ◽

N. Claude ◽

C. Legout

Keyword(s):

Sensitivity Analysis ◽

Fine Sediment ◽

Particle Properties ◽

Gravel Bed ◽

Sediment Deposits ◽

Gravel Bed Rivers ◽

Sediment Model

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Developing sustainable environments for aquatic life: The effects of boulders on regulating sediment deposition in gravel-bed rivers

Environmental Hydraulics, Two Volume Set ◽

10.1201/b10553-192 ◽

2010 ◽

pp. 1131-1136 ◽

Cited By ~ 3

Keyword(s):

Sediment Deposition ◽

Aquatic Life ◽

Gravel Bed ◽

Gravel Bed Rivers

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Gravel Bed Composition in Oregon Coastal Streams

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f80-196 ◽

1980 ◽

Vol 37 (10) ◽

pp. 1514-1521 ◽

Cited By ~ 68

Author(s):

J. N. Adams ◽

R. L. Beschta

Keyword(s):

Regression Analysis ◽

Fine Sediment ◽

Low Flow ◽

Coast Range ◽

Oregon Coast Range ◽

Oregon Coast ◽

Gravel Bed ◽

Fine Sediments ◽

High Flows ◽

The Impact

The amount of fine sediments (generally < 1 mm in diameter) in gravel bedded streams is often used as an indicator of habitat quality and also as a measure of the impact from accelerated sedimentation resulting from land disturbance. Five streams in the Oregon Coast Range were studied to evaluate temporal and spatial variability of streambed composition, as well as the factors affecting the amount of fine sediment within the bed. The amount of fine sediments (< 1 mm) contained in frozen streambed cores and expressed as a percentage (by weight) of the total sample proved highly variable in time and space. During a 19-mo sampling period, temporal variability was caused by an occasional flushing of fines from the gravel beds during high flows. Percent fines also varied greatly between streams, between locations in the same stream, and between locations in the same riffle. Streams on 21 Coast Range watersheds were sampled during summer low flow. The amount of fines averaged 19.4% for all watersheds and ranged from 10.6 to 29.4% for streams on undisturbed watersheds. Regression analysis indicated that the watershed slope, area, relief, and land use influenced the amount of fine sediment in the bed. Bed composition varied greatly between locations in the same stream with about 75% of the within-stream comparisons indicating a significant (α = 0.05) difference. Within a single stream, gravel bed composition correlated significantly with channel sinuosity and bank-full stage. Regression analysis and field observations suggested that road construction and logging operations can increase the amount of fines; however, such increases may be temporary if high flows flush the gravelsKey words: bed sediments, forest harvesting, Oregon Coast Range, sedimentation, spawning gravels, stream channels, water quality

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Infiltration Depth of Mineral Particles in Gravel-Bed Rivers

Minerals ◽

10.3390/min11111285 ◽

2021 ◽

Vol 11 (11) ◽

pp. 1285

Author(s):

Natalia Bustamante-Penagos ◽

Yarko Niño

Keyword(s):

Relative Density ◽

Fine Particles ◽

Reynolds Numbers ◽

Fine Sediment ◽

Infiltration Depth ◽

Gravel Bed ◽

Mineral Particles ◽

Gravel Bed Rivers ◽

Relationship Of ◽

The Relationship

This article discusses the results of an experimental study of a spill of mineral particles in gravel-bed rivers due to mining accidents. The purpose of this research is to characterize the dynamics of the fine mining particles spilled on a bed of immobilized gravel as a hyper-concentrated mixture and to experimentally characterize the infiltration phenomenon. We analyzed the type of infiltration considering the dimensionless coarse to fine particle size relationship, the dimensionless weight of the fine particles, the relative density of the particles, and the relationship between the subsurface and surface velocities, in addition to the densimetric Froude and Reynolds numbers of the fine particles. We found that the dimensionless infiltration depth is not associated with hydraulic parameters or the weight of the fine sediment spilled; however, fine sediment deposition decreases with depth, and infiltration depth may increase if subsurface flow decreases over time. Finally, a relationship of the dimensionless maximum infiltration depth with the relative density of the mining particles, the ratio of the bed sediment and the mining particles sizes, and the ratio between the subsurface and surface velocities is established.

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