Erosion of Cohesive Soils

Raudkm, A.J.; Tan, Sheryl

doi:10.1080/00221688409499380

Cited by 22 publications

(9 citation statements)

References 6 publications

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“…As Shen and Julien (1992) observed, however, a review of literature on the current knowledge of cohesive sediments shows that no general relationships exist to define incipient motion of these materials. Whereas particle size and density are important parameters dominating movement of non-cohesive material, the mineralogy, surface properties and electrochemical force of clay-size sediments, and the chemistry of the eroding water, strongly affect erosion of cohesive materials (Lau and Krishnappan, 1992;Raudkivi, 1998;Raudkivi and Tan, 1984). The value of Shield's entrainment parameter [Equation (2)] is increased by new cohesive forces described as a coefficient of cohesion (Graf, 1984).…”

Section: Theoretical Considerationsmentioning

confidence: 99%

Under‐ice movement of cohesive sediments before river‐ice breakup

Milburn

Prowse²

2002

Hydrological Processes

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Abstract:A significant body of research exists on river hydraulics and sediment transport during open-water conditions, and to a lesser extent during the period of ice-cover. Most of the ice-related studies, however, are based on controlled laboratory experiments or field studies conducted under stable ice-cover conditions. They have largely ignored the most dynamic periods, such as breakup, when hydraulic conditions are most rapidly changing and energy levels are maximized. Moreover, the entire pre-breakup to ice-clearance period is virtually devoid of even standard hydrometric measurements of suspended sediment, largely because of safety and logistic problems. Some recent work has pointed to the formation of a sediment plume comprising fine-grained sediments that develops before the main breakup fracturing of the ice cover. This plume has been noted as being particularly ecologically significant because it can contain the winter-long deposition of contaminants that preferentially attach to fine-grained material. Unfortunately, however, because measurements of the critical parameters affecting sediment transport during these periods are rarely taken, much uncertainty remains about the hydraulic forces that resuspend and transport sediments under an ice cover, and particularly for cohesive fine-grained sediments. This paper describes a field experiment designed to broaden our understanding of sediment transport during this critical pre-breakup period. Detailed measurements of river stage, ice elevations, flow velocity profiles and suspended sediment were taken over a 17-day period just before the 1998 river-ice breakup at Hay River, Northwest Territories, Canada. Results indicated that just before breakup, the shear stress, which governs the beginning of sediment motion, increases dramatically and drives the development of the under-ice sediment plume of very fine-grained, cohesive sediments. The shear stress in this case became critical at a mean under-ice velocity of 0Ð4 m/s.

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Section: Theoretical Considerationsmentioning

confidence: 99%

Under‐ice movement of cohesive sediments before river‐ice breakup

Milburn

Prowse²

2002

Hydrological Processes

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“…its pH value and molar salt concentration), as shown by Raudkivi and Tan (1984). The problem is considerably simplified in the case of incoherent soil, because the well-known Shields relation for the inception of sediment erosion (Shields, 1936;Yalin, 1977) can be properly used.…”

Section: Channel Network Extractionmentioning

confidence: 98%

Identification and Analysis of Natural Channel Networks From Digital Elevation Models

Pilotti

Gandolfi

Bischetti

1996

Earth Surf. Process. Landforms

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The identification and analysis of natural channel networks from digital elevation models are discussed from the point of view of their environmental applications. An interactive, graphical software package that implements some of the most widely used techniques for the automatic recognition of channel networks and for the computation of some useful geomorphologic indices and functions is presented.

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“…Because entrainment is from the soil surface where there is negligible overburden pressure, any soil strength must be dominantly due to cohesion. Raudkivi and Tan [1984] showed experimentally that (for cohesive sediment) the effects of cohesion are far greater than that of the submerged weight of detached particles in inhibiting removal of soil. The resistance offered by the soil matrix to removal by fluid stresses exerted on it by overland flow is defined by the energy per unit mass of soil required to entrain it, J, which is called the specific energy of entrainment.…”

Section: The Process Of Sediment Entrainmentmentioning

confidence: 99%

Modeling water erosion due to overland flow using physical principles: 1. Sheet flow

Hairsine¹,

Rose²

1992

Water Resources Research

353

293

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A new model for erosion of plane soil surfaces by water is developed using physical principles.Raindrop impact and overland flow remove soil from the original cohesive soil. Once eroded soil enters overland flow, either as aggregates or primary particles, a significant proportion of it returns to the soil bed, forming a cohesionless deposited layer from which it can be removed again by the same erosion processes. The action of the eroding agents will be divided between eroding the unshielded original cohesive soil and reintroducing sediment from the deposited layer. The theory recognizes that the nature of the surface is modified by the erosion and deposition processes affecting it. Solutions of the governing differential equations describing sediment concentration are developed for two distinct equilibrium cases. The first case, when the deposited layer completely shields the original soil, appears to correspond with what has been previously called a "transport-limited" situation. The second case occurs when such shielding is incomplete, and sediment concentration is affected by the cohesive strength of the soil. The resulting equations for sediment concentration at equilibrium are compared with existing equations. Firstly, the equation for the case where the soil is lacking cohesion is shown to be similar to the semiempirical equation of Yang (1973). Secondly, when the soil is cohesive the slope length relationships are shown to be in good agreement with the universal soil loss equation over a wide range of slope steepness.

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Erosion of Cohesive Soils

Cited by 22 publications

References 6 publications

Under‐ice movement of cohesive sediments before river‐ice breakup

Under‐ice movement of cohesive sediments before river‐ice breakup

Identification and Analysis of Natural Channel Networks From Digital Elevation Models

Modeling water erosion due to overland flow using physical principles: 1. Sheet flow

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