Field rainfall simulator studies on two clay soils of the Darling Downs, Queensland. II. Aggregate Breakdpwn, sediment properties and soil erodibility

Soil Research ◽  
1983 ◽  
Vol 21 (1) ◽  
pp. 47 ◽  
Author(s):  
RJ Loch ◽  
TE Donnollan
Keyword(s):  
Overland Flow ◽  
Clay Soils ◽  
Bed Load ◽  
Flowing Water ◽  
Size Distributions ◽  
Runoff Water ◽  
Sediment Size ◽  
Soil Sediment ◽  
The Difference ◽  
Load Sediment

Size distributions of the solids in runoff water were measured for two clay soils subjected to simulated rain under a range of plot lengths and two tillage orientations. Selective transport did not appear to have affected the sediment size distributions. Therefore, these could be used as a measure of soil structure and aggregate breakdown by rainfall and runoff. There was little dispersed clay, most of the sediment remaining aggregated. For each soil, sediment size distributions were bimodal, peaks in sediment size being related to orders of aggregation in each soil. Concentrations of dispersed clay provide evidence that stresses on aggregates moved by rain impact on flowing water were greater than on those moved in rills by flowing water alone. Consistent with this, sediment size distributions showed much less breakdown to sizes <0.125 mm in rills. Suspended load (sediment < 20 �m) showed little temporal fluctuation, and little or no decrease with time, suggesting that for these soils, aggregate disruption by raindrops and overland flow provides a continuous source of suspendable material. Bed-load was more variable and saltating and contact load appeared to be complementary to some extent. Large differences between the two soils in measured sediment concentrations could not be explained by slight differences in sediment size. However, large differences between the soils in the water content and density of saturated aggregates were found. Transport equations for bed-load sediment suggest that the measured difference in aggregate density is sufficient to explain the difference between the soils in rates of sediment transport.

Evaluation of the CREAMS model. I. Sensitivity analysis of the soil erosion sedimentation component for aggregated clay soils

Soil Research ◽  
1989 ◽  
Vol 27 (3) ◽  
pp. 545 ◽  
Author(s):  
DM Silburn ◽  
RJ Loch
Keyword(s):  
Soil Erosion ◽  
Sediment Yield ◽  
Overland Flow ◽  
Clay Soils ◽  
Slope Length ◽  
Sediment Size ◽  
Total Runoff ◽  
Peak Runoff ◽  
Relative Change ◽  
Parameter Values

The sensitivity of the soil erosion component of the CREAMS model to changes in various input parameters was assessed in the range of parameter values suited to erosion from aggregated clay soils. Predictions of total sediment yield were sensitive to changes in a number of parameters, and interactions between parameter values were observed, e.g., for situations when either detachment of sediment or transport capacity of overland flow limited sediment yield. The CREAMS model was classified as: (i) sensitive to: specific gravity of sediment (Sgi), slope steepness; (ii) sensitive under some conditions, moderately sensitive under others to: total runoff (Vu); Universal Soil Loss Equation factors of erodibility (K), cover (C) and support practices (P); Manning-type available shear parameter (nbov); (iii) moderately sensitive to: peak runoff rate (�p), storm erosivity (EI30), slope length, sediment size distribution and kinematic viscosity. The model was judged to be 'sensitive' to a parameter when change in that parameter caused an equal or greater relative change in predicted sediment yield.

Effects of the amount of stubble mulch and overland flow on erosion of a cracking clay soil under simulated rain

Soil Research ◽  
1988 ◽  
Vol 26 (4) ◽  
pp. 661 ◽  
Author(s):  
RJ Loch ◽  
TE Donnollan
Keyword(s):  
Field Study ◽  
Overland Flow ◽  
Clay Soil ◽  
Soil Surface ◽  
Bare Soil ◽  
Bed Load ◽  
Simulated Rain ◽  
Wheat Stubble ◽  
Future Work ◽  
Load Sediment

A field study by using simulated rain and run-on water was carried out to determine the effects of different amounts of wheat stubble mulch (ranging from 0.1 to 3 t ha-1) and increasing discharge on erosion. Rain-flow erosion decreased with increasing amounts of stubble. Concentrations of bed-load sediment carried by rain-flow decreased with increasing plot discharge. As discharges increased, overland flow probably became too deep for drop impact to effectively disturb the soil surface and entrain sediment. Only plots carrying 0.1 t ha-1 stubble showed definite scour by overland flow. However, sediment concentrations produced by scour were well below those measured in rill flow on bare soil at this site, showing that even very small rates of stubble mulch can, in some situations, significantly reduce erosion. Discharges at which rilling develops fully must be much larger than those at which scour by overland flow is initiated. Future work will need to consider discharges much larger than those used in this study.

Sediment generation from forest roads: bed and eroded sediment size distributions, and runoff management strategies

Soil Research ◽  
1999 ◽  
Vol 37 (5) ◽  
pp. 947 ◽  
Author(s):  
R. D. Connolly ◽  
A. Costantini ◽  
R. J. Loch ◽  
R. Garthe
Keyword(s):  
Overland Flow ◽  
Fine Particles ◽  
Management Strategies ◽  
Size Distributions ◽  
Wet Season ◽  
Support Tool ◽  
Forest Road ◽  
Sediment Size ◽  
Overland Flows ◽  
Road Surfaces

A rainfall simulator and overland flow study was conducted to determine in situ and eroded sediment size distributions for a range of forest road surfaces at 2 important commercial plantation centres in subtropical south-east Queensland, Australia; and parameters necessary for running the CREAMS model to assess erosion and sediment transport from road/table drain systems. Results revealed very low concentrations of fine particles in the surface of gravel roads, and somewhat higher proportions in ungravelled (dirt) road surfaces. However, there was considerable enrichment of fine particles in sediment eroded under simulated rain, with concentrations of particles <0 . 02 mm in diameter being up to 8 g/L. Table drains were generally resistant to scour by overland flows, with the only exception being a drain bordering a newly gravelled road. This drain was bare of vegetation and contained significant quantities of loose gravel from which the fine component was easily eroded. It demonstrated the need to construct both roads and table drains at the end of the wet season when consolidation and re-vegetation can occur under lighter rains during the dry season. CREAMS model runs for a ‘standard’ road and drain configuration predicted considerable enrichment of fine particles in sediment from all road surfaces. The major factor controlling predicted concentrations of fine particles was the rate of erosion from the road surface, with gravelled surfaces showing considerably less erosion than ungravelled surfaces. Because road surfaces will be significant sources of fine sediment during erosive rains, a second part of this study was designed to model whether hillslopes could be used to infiltrate runoff, thereby controlling sediment movement. For the modelled hillslopes—typical of those used to support commercial forest plantations in south-east Queensland—design runoffs from forest road turn-out drains could be infiltrated. It is suggested that forest managers use hillslope infiltration as the primary tool for managing flows and sediments from road turn-out drains, and that vegetative filter strips be used only as a secondary support tool.

Rill erosion of a self-mulching black earth. I. Effects of tillage

Soil Research ◽  
1989 ◽  
Vol 27 (3) ◽  
pp. 525 ◽  
Author(s):  
RJ Loch ◽  
TE Donnollan
Keyword(s):  
Overland Flow ◽  
Aggregate Size ◽  
Size Distributions ◽  
Silt Loam ◽  
Rill Erosion ◽  
Tillage Practices ◽  
Sediment Size ◽  
Stubble Retention ◽  
Silt Loam Soil ◽  
Loam Soil

The effects of three tillage treatments-rough-, fine- and zero-tilled-on rill erosion of a bare, self-mulching black earth were tested to determine whether tillage practices could reduce susceptibility of such soils to entrainment and transport by overland flow. In contrast to reported results for a silt loam soil, rill erosion was greatest for zero-tilled soil, and similar for the two tilled treatments. Sediment size distributions were independent of initial dry aggregate size distributions. It seems that, for self-mulching soils, stubble retention is the only method available to increase resistance to erosion by overland flow.

Modelling of Solute Transfer to Surface Runoff

1992 ◽  
Vol 26 (7-8) ◽  
pp. 1851-1856 ◽  
Author(s):  
J. L. Lai ◽  
K. S. L. Lo
Keyword(s):  
Potassium Chloride ◽  
Surface Runoff ◽  
Laboratory Experiments ◽  
Overland Flow ◽  
Chloride Concentration ◽  
Runoff Water ◽  
Mixing Depth ◽  
Change Rate ◽  
Solute Transfer ◽  
The Media

A mixing-based model for describing solute transfer to overland flow was developed. This model included a time-dependent mixing depth of the top layer and a complete-mixed surface runoff zone. In a series of laboratory experiments, runoff was passed at various velocities and depths over a medium bed. The media were saturated with uniform concentration of potassium chloride solution. Runoff water was sampled at the beginning and end of the flume and the potassium chloride concentration analyzed. Using this model, dimensionless ultimate mixing depth and dimensionless change rate of mixing depth from experimental data were investigated and implemented. The results showed that the Reynolds number and relative roughness are two important factors.

scholarly journals Relative Transportability for Non-uniform Bed Load Sediment Transport

2018 ◽  
Vol 153 ◽  
pp. 042006
Author(s):  
Li Zhijing ◽  
Li Dazhi ◽  
Liu Xiaobin ◽  
Jin Zhongwu ◽  
Chen Dasong
Keyword(s):  
Sediment Transport ◽  
Bed Load ◽  
Load Sediment
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