Unified Model of Sediment Transport Threshold and Rate Across Weak and Intense Subaqueous Bedload, Windblown Sand, and Windblown Snow

Pähtz, Thomas; Liu, Yonghui; Xia, Yuanming; Hu, Peng; He, Zhiguo; Tholen, Katharina

doi:10.1029/2020jf005859

Cited by 23 publications

(86 citation statements)

References 125 publications

(461 reference statements)

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“…[23][24][25]40 , our phase diagram in Fig. 2 is computed on the basis of a conceptually new, but phenomenologically already well tested, quantitative grain-scale model for the saltation threshold 45 . The latter model is herein generalized to account for the size disparity between saltating fine grains and coarse armouring grains.…”

Section: Resultsmentioning

confidence: 99%

“…6b in ref. 45 ), the theoretical prediction simplifies to the following analytical implicit expression (Methods):…”

Section: Resultsmentioning

confidence: 99%

“…6b in ref. 45 ), the theoretical prediction simplifies to the following analytical implicit expression (Methods): Here, , with the mean horizontal fine-grain rebound (impact) velocity, is a function of (Eq. ( M12 )), and V s is the dimensionless settling velocity, which is a known function of Ga (f) alone (Eq.…”

Section: Resultsmentioning

confidence: 99%

“…For its computation, the fine-grain motion is idealized by a periodic saltation trajectory over a coarse-grain bed. While the original periodic saltation model 45 was constructed for monodisperse sand, we here account for the size disparity between the saltating fine grains and the coarse bed grains (see below and subsequently Supplementary Information for a generalized rebound law). Saltation thresholds.…”

Section: Methodsmentioning

confidence: 99%

“…Periodic saltation model. Here, we briefly summarize relevant aspects of the periodic saltation model 45 used to quantify the motion of the saltating grains in the above threshold calculations and to analytically estimate the width of the reptation regime. While its original version was derived for monodisperse sands (d (c) = d (f) ), we here extend it to also cover the scenario of fine-grain saltation over an armouring layer of coarse grains (d (c) ≥ d (f) ).…”

Section: Methodsmentioning

confidence: 99%

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Megaripple mechanics: bimodal transport ingrained in bimodal sands

et al. 2022

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Aeolian sand transport is a major process shaping landscapes on Earth and on diverse celestial bodies. Conditions favoring bimodal sand transport, with fine-grain saltation driving coarse-grain reptation, give rise to the evolution of megaripples with a characteristic bimodal sand composition. Here, we derive a unified phase diagram for this special aeolian process and the ensuing nonequilibrium megaripple morphodynamics by means of a conceptually simple quantitative model, grounded in the grain-scale physics. We establish a well-preserved quantitative signature of bimodal aeolian transport in the otherwise highly variable grain size distributions, namely, the log-scale width (Krumbein phi scale) of their coarse-grain peaks. A comprehensive collection of terrestrial and extraterrestrial data, covering a wide range of geographical sources and environmental conditions, supports the accuracy and robustness of this unexpected theoretical finding. It could help to resolve ambiguities in the classification of terrestrial and extraterrestrial sedimentary bedforms.

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Section: Resultsmentioning

confidence: 99%

“…6b in ref. 45 ), the theoretical prediction simplifies to the following analytical implicit expression (Methods):…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Megaripple mechanics: bimodal transport ingrained in bimodal sands

et al. 2022

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Cross‐wavelet analysis of coherent wind and saltation events

Ellis

Sherman

2022

Earth Surf Processes Landf

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This paper presents high-resolution field measurements of the wind and saltation fields using miniphones and anemometers located 20-40 mm apart (bed-parallel) and 10-40 mm above the bed. The average wind speeds at the Shoalhaven Heads, Australia and the Jericoacoara, Brazil field sites are both 4.4 m s À1 , and the average saltation rates are 5.0 and 22.2 counts/mm 2 s À1 , respectively. Normalized crosscovariance analysis between the wind and saltation time series indicates a dominant saltation response time of 0 s. Cross-wavelet analysis focusing on short-duration events characterizes statistically significant wind-sand events and intervals. In the high aeolian saltation rate environment (Brazil), the events and intervals averaged 1.9 and 12.2 s. The low transport environment (Australia) resulted in 2.1 s events and 10.8 s intervals. This study demonstrates that wind-sand events occur about 15% of the time but account for about 23% of the sand transport. These results were possible because of the presentation of a wavelet-derived event time series. The criticality of tightly controlled field experiments to measure coincident wind and saltation fluctuations with co-located sensors was demonstrated. This paper emphasizes the importance of the contribution of saltation events to time-averaged transport rates, which influences sediment flux modelling.

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Nontrivial scaling in supply limited Aeolian sand transport

Kamath

Shao

Parteli

2021

Preprint

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Previous studies of wind-blown sand have considered either fully erodible or non-erodible soils, but the transport over sparsely sand-covered soils is still poorly understood. The quantitative modeling of this transport is important for the parametrization of Aeolian processes under low sand availability. Here we show, by means of particle-based numerical simulations, that the Aeolian sand transport rate Q scales with the wind shear velocity u* as Q = a.[1 + b . (u*/u*t -1)] .[?](d/g) . ρf. (u*² -u*t2), where u*t is the minimal threshold u* for sustained transport, d is particle size, g is gravity and ρf is air density, while u*t and the empirical parameters a and b depend on the sand cover thickness. Our model explains the transition from the quadratic to cubic scaling of Q with u* as soil conditions change from fully erodible to rigid and provides constraints for modeling Aeolian transport under low sand availability.

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Unified Model of Sediment Transport Threshold and Rate Across Weak and Intense Subaqueous Bedload, Windblown Sand, and Windblown Snow

Cited by 23 publications

References 125 publications

Megaripple mechanics: bimodal transport ingrained in bimodal sands

Megaripple mechanics: bimodal transport ingrained in bimodal sands

Cross‐wavelet analysis of coherent wind and saltation events

Nontrivial scaling in supply limited Aeolian sand transport

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