Bias in grainsize distribution of deposited atmospheric dust due to the collection of particles in sediment catchers
Aeolian dust ; Aeolian features ; Experimentation ; Grainsize distribution ; Instrumentation ; Sedimentology ; Statistical bias ; Wind speed
This study investigates how dust deposition samplers affect the grainsize characteristics of the sediment they catch. Some particle fractions are collected more efficiency than others, resulting in a modification of the original grainsize
distribution of the sediment. This paper presents wind tunnel results for 5 dust deposition samplers and 5 wind velocities. The catcher's effect on the grainsize was apparent in all experiences.
Aeolian deposition of dust over hills : the effect of dust grainsize on the deposition pattern
Aeolian dust ; Aeolian features ; Aeolian transport ; Belgium ; Experimentation ; Flemish Brabant ; Grainsize distribution ; Impact ; Leuven ; Topography
Wind tunnel experiments were conducted to investigate the effects of topography on the grainsize characteristics of aeolian dust deposits. Experiments were performed on 3 isolated hills having various size and aspect ratios. The longitudinal
profile of the median grain diameter was investigated for each hill. The wind tunnel experiments show that the grainsize characteristics of aeolian dust deposits are affected by topography.
A numerical model for shore-normal sediment size variation on a macrotidal beach
Coastal dynamics ; Coastal environment ; Grainsize distribution;Granulometry ; Intertidal zone ; Isle of Man ; Model ; Numerical model ; United Kingdom
This paper describes a computer simulation model which is designed to predict the selective shore-normal sorting of grainsizes in the nearshore environment. The predicted grainsize is used in an hydraulic interpretation of grainsize distribution
of the intertidal profile, based on the hydrodynamic variations over a tidal cycle on a macrotidal beach. The model is successful in predicting the broad pattern of increasing grainsize in the onshore direction which has been observed in nature.
Differential bedload transport rates in a gravel-bed stream : a grain-size distribution approach
The objective of this paper is to investigate whether the systematic variations of bedload grain-size distributions observed in Oak Creek can serve as the basis for calculations of transport rates of different size fractions. The approach will rely
on the Rosin distribution and how its parameter depend on the flow discharge and bed stress. The total transport rate, which is also a function of the discharge or stress, is then apportioned within the distribution of grainsizes of the Rosin distribution
to yield frequency curves for the differential transport rates of the spectrum of grainsizes.
Bias and precision of percentiles of bulk grainsize distributions
Carrying capacity ; Grainsize distribution ; Gravel ; Methodology ; Sampling ; Sediment transport ; Sedimentology ; Statistical distribution ; Statistics ; Stream
Grainsize analysis is a standard tool in the study of sediments. This paper presents a method for computer sampling experiments on variability in percentiles of a bulk grainsize distributions (GSD), results for commonly used size percentiles
GRADISTAT : a grainsize distribution and statistics package for the analysis of unconsolidated sediments
Computing ; Grainsize distribution ; Methodology ; Sedimentology ; Statistics
Grainsize analysis is an essential tool for classifying sedimentary environments. A computer program called GRADISTAT has been written for the rapid analysis of grainsize statistics from any of the standard measuring techniques, such as sieving
and laser granulometry. The program runs within the Microsoft Excel spreadsheet package and is extremely versatile, accepting standard and non-standard size data, and producing a range of graphical outputs including frequency and ternary plots.
Grain-size analysis by laser diffractometry : comparison with the sieve-pipette method
Clay mineral ; Grainsize distribution ; Methodology ; Soil ; Soil properties ; Soil science ; X-ray diffraction analysis
Results of a traditional sedimentation technique for grain-size analysis (the sieve-pipette method) were compared with those of a laser diffraction grain-size analyser, the Coulter LS-100. Milled quartz samples and silty soil samples were used
Shih and Komar argue here that the dimensional analysis of Diplas obscures the relationship between the transport rate and grainsize, and in fact leads to a complex implausible dependence. In contrast, their approach allows one to better focus
on the changing grain-size distributions as the flow discharge and mean bottom stress increase.
Grain-size analysis of surface material under wind erosion using the effective surface concept
Aeolian features ; Aeolian transport ; Concept ; Experimentation ; Grainsize distribution ; Methodology ; Roughness ; Wind erosion
This paper deals with the temporal variation in the grainsize of surface material using an analytical method based on the effective surface concept. This method is applied to data collected in 2 series of wind tunnel experiments. The results
are compared with findings of other studies on aeolian sediment transport rate for individual grainsize classes over time.
Mesures de la taille des grains à partir d'échantillonnage du terrain. Signature de la texture des séries de dimensions des grains. Relation entre dimension des grains et texture des images. Cartographie des dimensions des grains.
Grain-size distribution patterns of a point bar system in the Usri River, India
Bank erosion ; Grainsize distribution ; Hydrodynamics ; India ; Model ; Sedimentary structure ; Spatial distribution ; Statistics ; Stream ; West Bengal
Grain-size distribution patterns in a point bar system of the Usri River, India, were critically analysed in the light of log-normal, log-hyperbolic and log-skew-Laplace distribution models. Sand samples were collected from the cross-bedding foreset
of different sizes of bedform; the aims were to : study whether bedforms heights have any role in grain-size distribution patterns, offer a best-fit statistical model, study the downstream variation of size-sorting in a point bar system, and study the mechanism
A hybrid method for size characterisation of coarse subsurface fluvial sediments
Grainsize distribution ; Methodology ; Model ; River bed ; Sampling ; Sedimentation ; Sedimentology ; Stream
This paper introduces and evaluates a novel method for ascertaining the grain-size distribution of subsurface sediments that involves profoundly less sampling effort than standard methods. It is based on hybrid sampling principles previously applied
to the construction of synthetic surface grain-size distributions. The method is developed from an empirical demonstration of the approximate similarity of surface and subsurface grain-size distributions when compared over a common range of sizes. Subsurface hybrid
models are found to provide good facsimilies of grain-size distributions using standard criteria. The technique is presented as an expedient alternative to standard methods for large, perennial gravel-bed rivers.
Vertical distribution of grain-size parameters of drifting particles during sand storms in the Taklamakan desert, Central Asia
Aeolian features ; Arid area ; China ; Desert ; Dust storm ; Experimentation ; Grainsize distribution ; Sand ; Sedimentology ; Wind speed
The vertical distributions of grain-size parameters of drifting sand flux during sand storms in the Taklamakan Desert, were investigated through field observation and laboratory wind-tunnel tests. The results show that grain-size parameters
of the drifting sands near the ground surface are similar to those of the source deposits. Regional differences in the vertical distribution of grain-size compositions are affected by source deposits, wind speeds, and transport rates, but source has more influence
A study of river channel pattern information recorded by grainsize parameters of fluvial sediment
Using data from some Chinese rivers, an attempt has been made to express quantitavely, by using statistical methods, the connections between river channel pattern characteristics and the corresponding river bed material grainsize parameters.
A close relationship exists between the grainsize and weathering and soil forming processes. The genetic and character-modifying roles of grainsize are important. Author elaborated a new method to separate loess horizons and to eliminate
Two-dimensional analysis of dune profile and the effect of grainsize on sand dune morphology in Physics of desertification.
Theoretical consideration shows that the steady-state profile of a dune subjected to an unidirectional wind is flat, low and convex with the ratio of dune height to its upwind length = 0,05. Grainsize is another factor governing dune profile
. A coarse-grained sand dune has a greater difference in threshold velocity between the crest area and its lower level than a finer-grained sand dune of a similar profile. It will have much longer periods of erosion taking place only at or near the crest
The effects of grain abrasion and disaggregation on 137 Cs concentrations in different size fractions of soils developed on three different rock types
Australia ; Erosion ; Geochemistry ; Grainsize distribution ; Isotope analysis ; Sediment transport ; Sedimentology ; Tracer ; Victoria ; Watershed
of disaggregation and grain abrasion on the distribution of 137 Cs with respect to particle size fractions were studied in soils derived from the 3 different rock types of the Tarago catchment.
. Different sediments were used in order to study the effect of grainsize. The proposed relationship show considerable variations with grainsize and there is only a minor effect of rainfall on the transport capacity which also seems to be grainsize
sands on the basis of pollen analysis, C and archeological findings. Grain-size analyses of sediments collected in various points of the discussed area reveal differences among particular stands. Reasons for such grain-size variations should be looked
for in grain-size of the bottom sediments. It has been also found that eolian cover sands of West and Central Europe are differentiated in respect of grain-size. (L'A.).