Causes and effects of noise in landscape dynamics

Jerolmack, D. J.

doi:10.1029/2011eo440001

Cited by 22 publications

(19 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…At present we have an incomplete understanding of the packing fraction near the free surface and the motion of particles in the creep regime; these deserve further investigations that may motivate new comparisons with nonlocal rheology models. Many rivers and hillslopes are granular systems that self-organize such that they are in the vicinity of the threshold of motion [61]. Thus, a better understanding of creep dynamics will improve long-term predictions of landscape evolution.…”

Section: Discussionmentioning

confidence: 99%

Rheology of sediment transported by a laminar flow

et al. 2016

View full text Add to dashboard Cite

Understanding the dynamics of fluid-driven sediment transport remains challenging, as it occurs at the interface between a granular material and a fluid flow. Boyer, Guazzelli, and Pouliquen [Phys. Rev. Lett. 107, 188301 (2011)] proposed a local rheology unifying dense dry-granular and viscous-suspension flows, but it has been validated only for neutrally buoyant particles in a confined and homogeneous system. Here we generalize the Boyer, Guazzelli, and Pouliquen model to account for the weight of a particle by addition of a pressure P0 and test the ability of this model to describe sediment transport in an idealized laboratory river. We subject a bed of settling plastic particles to a laminar-shear flow from above, and use refractive-index-matching to track particles’ motion and determine local rheology—from the fluid-granular interface to deep in the granular bed. Data from all experiments collapse onto a single curve of friction μ as a function of the viscous number Iv over the range 3 × 10−5 ≥ Iv ≥ 2, validating the local rheology model. For Iv < 3 × 10−5, however, data do not collapse. Instead of undergoing a jamming transition with μ → μs as expected, particles transition to a creeping regime where we observe a continuous decay of the friction coefficient μ ≥ μs as Iv decreases. The rheology of this creep regime cannot be described by the local model, and more work is needed to determine whether a nonlocal rheology model can be modified to account for our findings.

show abstract

Section: Discussionmentioning

confidence: 99%

Rheology of sediment transported by a laminar flow

et al. 2016

View full text Add to dashboard Cite

show abstract

“…The traditional approach to understand the sources of bed load transport variability and the subsequent sediment organization consists in studying the variations of the fluid forces. But, the grain‐grain interactions are probably also a crucial driving factor as many analogies exist between dry granular flows and bed load transport [ Jerolmack , 2011]. More recently, fluvial geomorphologists have reintroduced explicitly granular physics concepts in the understanding of bed load and the formation of armor layer in a gravel bed [ Frey and Church , 2009, 2011].…”

Section: Discussionmentioning

confidence: 99%

Using multiple bed load measurements: Toward the identification of bed dilation and contraction in gravel‐bed rivers

Marquis

Roy

2012

J. Geophys. Res.

View full text Add to dashboard Cite

[1] This study examines bed load transport processes in a small gravel-bed river (Béard Creek, Québec) using three complementary methods: bed elevation changes between successive floods, bed activity surveys using tags inserted into the bed, and bed load transport rates from bed load traps. The analysis of 20 flood events capable of mobilizing bed material led to the identification of divergent results among the methods. In particular, bed elevation changes were not consistent with the bed activity surveys. In many cases, bed elevation changes were significant (1 to 2 times the D 50 ) even if the bed surface had not been activated during the flood, leading to the identification of processes of bed dilation and contraction that occurred over 10% to 40% of the bed surface. These dynamics of the river bed prevent accurate derivation of bed load transport rates from topographic changes, especially for low magnitude floods. This paper discusses the mechanisms that could explain the dilation and contraction of particles within the bed and their implications in fluvial dynamics. Bed contraction seems to be the result of the winnowing of the fine sediments under very low gravel transport. Bed dilation seems to occur on patches of the bed at the threshold of motion where various processes such as fine sediment infiltration lead to the maintenance of a larger sediment framework volume. Both processes are also influenced by flood history and the initial local bed state and in turn may have a significant impact on sediment transport and morphological changes in gravel-bed rivers.Citation: Marquis, G. A., and A. G. Roy (2012), Using multiple bed load measurements: Toward the identification of bed dilation and contraction in gravel-bed rivers,

show abstract

“…First, the traditional Shields diagram indicates that τ * c is rather insensitive to particle Reynolds number once flow becomes hydraulically rough around grains (Buffington, 1999). Second, because the best estimate of a given variable is usually its average, there is a tendency to attribute variability to measurement noise and uncertainty, even when that variability may be real, understandable, and important to system dynamics (Jerolmack, 2011;Buffington and Montgomery, 1997;Chen and Stone, 2008). Third, a broadly applicable model for the temporal evolution of τ * c has arguably not been developed, although progress has been made (Recking, 2012;Bunte et al, 2013;Wilcock and Crowe, 2003).…”

Section: Motivationmentioning

confidence: 99%

Gravel threshold of motion: a state function of sediment transport disequilibrium?

Johnson

2016

Earth Surf. Dynam.

View full text Add to dashboard Cite

Abstract. In most sediment transport models, a threshold variable dictates the shear stress at which nonnegligible bedload transport begins. Previous work has demonstrated that nondimensional transport thresholds (τ * c ) vary with many factors related not only to grain size and shape, but also with characteristics of the local bed surface and sediment transport rate (q s ). I propose a new model in which q s -dependent τ * c , notated as τ * c(q s ) , evolves as a power-law function of net erosion or deposition. In the model, net entrainment is assumed to progressively remove more mobile particles while leaving behind more stable grains, gradually increasing τ * c(q s ) and reducing transport rates. Net deposition tends to fill in topographic lows, progressively leading to less stable distributions of surface grains, decreasing τ * c(q s ) and increasing transport rates. Model parameters are calibrated based on laboratory flume experiments that explore transport disequilibrium. The τ * c(q s ) equation is then incorporated into a simple morphodynamic model. The evolution of τ * c(q s ) is a negative feedback on morphologic change, while also allowing reaches to equilibrate to sediment supply at different slopes. Finally, τ * c(q s ) is interpreted to be an important but nonunique state variable for morphodynamics, in a manner consistent with state variables such as temperature in thermodynamics.

show abstract

Causes and effects of noise in landscape dynamics

Cited by 22 publications

References 18 publications

Rheology of sediment transported by a laminar flow

Rheology of sediment transported by a laminar flow

Using multiple bed load measurements: Toward the identification of bed dilation and contraction in gravel‐bed rivers

Gravel threshold of motion: a state function of sediment transport disequilibrium?

Contact Info

Product

Resources

About