Soil erosion processes.II. Settling velocity characteristics of eroded sediment

Soil Research ◽  
1991 ◽  
Vol 29 (5) ◽  
pp. 685 ◽  
Author(s):  
APB Proffitt ◽  
CW Rose
Keyword(s):  
Overland Flow ◽  
Settling Velocity ◽  
Soil Surface ◽  
Soil Types ◽  
Rill Erosion ◽  
Sheet Flow ◽  
Spatial Redistribution ◽  
Volumetric Flux ◽  
Sheet Erosion ◽  
Rill Flow

Settling velocity characteristics of sediment eroded by overland flow only, or from a combination of rainfall (100 mm h-l) and runon were measured under controlled conditions in a simulated rainfall tilting-flume facility. Two contrasting soil types were studied: a cracking clay (black earth or vertisol), and a slightly dispersive sandy clay loam (solonchak or aridisol). For a constant volumetric flux (1.0x10-1 m3 m-1 s-1) at exit from the 5.8m long flume and a slope of 0.5%, sheet erosion prevailed, whilst for the same flux at a steeper slope of 5%, rill erosion prevailed. Settling velocity characteristics of eroded sediment were found to be dependent on erosion process, flow hydraulics, soil type, and time in the erosion event. For both soil types, there was a progressive change in settling velocity characteristics with time, this change being less pronounced for sediment eroded dominantly by rill flow as opposed to sheet flow. Temporal changes in settling velocity characteristics were attributed to the development of a deposited layer of coarser, faster settling sediment on the soil surface. The net outcome of rill erosion was less size-selectivity compared with sheet erosion, as determined by the measured settling velocity characteristics of eroded sediment. This outcome was associated with the greater erosive power of rill flow compared with sheet flow. Rainfall was found to influence the settling velocity characteristics of eroded sediment substantially when sheet flow predominated. This was thought to be due to lower flow velocities under rainfall (and therefore smaller contribution to soil loss by entrainment). The findings reported in this study have important implications when assessing nutrient losses from eroded sediment, and in predicting the spatial redistribution of eroded sediment.

Soil erosion processes. I. The relative importance of rainfall detachment and dunoff entrainment

Soil Research ◽  
1991 ◽  
Vol 29 (5) ◽  
pp. 671 ◽  
Author(s):  
APB Proffitt ◽  
CW Rose
Keyword(s):  
Soil Erosion ◽  
Overland Flow ◽  
Water Flux ◽  
Equilibrium Concentration ◽  
Sediment Concentration ◽  
Soil Types ◽  
Relative Importance ◽  
Runoff Water ◽  
Erosion Processes ◽  
Volumetric Flux

Experiments carried out in a simulated-rainfall tilting-flume facility are reported in which sediment concentrations (c) in runoff water resulting from overland flow only, or from a combination of rainfall and overland flow, were measured under controlled conditions using a series of slopes (0.1, 05, 1, 3 and 5%). The mixture of rainfall (of rate 100 mm h-1) and runon of water at the top of the flume were arranged to provide a constant volumetric flux (1.0x10-3 m3 m-l s-1) at exit from the 5.8 m long flume. Two contrasting soil types were studied: a cracking clay (black earth or vertisol), and a slightly dispersive sandy clay loam (solonchak or aridisol). Two major processes which can contribute to soil erosion under rainfall are rainfall detachment and runoff entrainment. For both soil types, c was generally highest for the steepest slope and decreased with slope. For constant rainfall and/or runoff conditions, c generally decreased with time until an equilibrium concentration was reached. At this equilibrium, the relative importance of rainfall detachment and entrainment in terms of soil loss was dependent on soil type and streampower which incorporates effects of slope and water flux. For streampowers <0.1 W m-2 for the black earth, and <0.3 W m-2 for the solonchak, the greatest contribution to c was by rainfall detachment, whilst at greater streampowers entrainment was the dominant contributor to c. At any streampower, the contribution by rainfall detachment was greater for the weakly structured solonchak than for the well aggregated black earth. At lower strearnpowers, the interaction between erosion processes was found to give higher c than the sum of both sediment concentrations resulting from the separately occurring processes. At streampowers greater than approximately 0.5 W m-2, rainfall reduced eroded sediment concentration by suppressing rill development. The findings in this study suggest that both runoff entrainment and rainfall detachment can contribute to sediment concentration from 'interrill' areas.

scholarly journals Effect of tillage, slope, and rainfall on soil surface microtopography quantified by geostatistical and fractal indices during sheet erosion

2020 ◽  
Vol 12 (1) ◽  
pp. 232-241
Author(s):  
Na Ta ◽  
Chutian Zhang ◽  
Hongru Ding ◽  
Qingfeng Zhang
Keyword(s):  
Surface Roughness ◽  
Fractal Dimension ◽  
Soil Surface ◽  
Rainfall Events ◽  
Tillage Practices ◽  
Surface Microtopography ◽  
Artificial Rainfall ◽  
Soil Surface Roughness ◽  
The Difference ◽  
Sheet Erosion

AbstractTillage and slope will influence soil surface roughness that changes during rainfall events. This study tests this effect under controlled conditions quantified by geostatistical and fractal indices. When four commonly adopted tillage practices, namely, artificial backhoe (AB), artificial digging (AD), contour tillage (CT), and linear slope (CK), were prepared on soil surfaces at 2 × 1 × 0.5 m soil pans at 5°, 10°, or 20° slope gradients, artificial rainfall with an intensity of 60 or 90 mm h−1 was applied to it. Measurements of the difference in elevation points of the surface profiles were taken before rainfall and after rainfall events for sheet erosion. Tillage practices had a relationship with fractal indices that the surface treated with CT exhibited the biggest fractal dimension D value, followed by the surfaces AD, AB, and CK. Surfaces under a stronger rainfall tended to have a greater D value. Tillage treatments affected anisotropy differently and the surface CT had the strongest effect on anisotropy, followed by the surfaces AD, AB, and CK. A steeper surface would have less effect on anisotropy. Since the surface CT had the strongest effect on spatial variability or the weakest spatial autocorrelation, it had the smallest effect on runoff and sediment yield. Therefore, tillage CT could make a better tillage practice of conserving water and soil. Simultaneously, changes in semivariogram and fractal parameters for surface roughness were examined and evaluated. Fractal parameter – crossover length l – is more sensitive than fractal dimension D to rainfall action to describe vertical differences in soil surface roughness evolution.

scholarly journals Scale effect on overland flow connectivity at the plot scale

2013 ◽  
Vol 17 (1) ◽  
pp. 87-101 ◽  
Author(s):  
A. Peñuela ◽  
M. Javaux ◽  
C. L. Bielders
Keyword(s):  
Scale Effect ◽  
Overland Flow ◽  
Soil Surface ◽  
Real Field ◽  
Flow Paths ◽  
Essential Information ◽  
Elevation Data ◽  
Distributed Hydrological Models ◽  
Outflow Boundary ◽  
Degree Of Filling

Abstract. A major challenge in present-day hydrological sciences is to enhance the performance of existing distributed hydrological models through a better description of subgrid processes, in particular the subgrid connectivity of flow paths. The Relative Surface Connection (RSC) function was proposed by Antoine et al. (2009) as a functional indicator of runoff flow connectivity. For a given area, it expresses the percentage of the surface connected to the outflow boundary (C) as a function of the degree of filling of the depression storage. This function explicitly integrates the flow network at the soil surface and hence provides essential information regarding the flow paths' connectivity. It has been shown that this function could help improve the modeling of the hydrograph at the square meter scale, yet it is unknown how the scale affects the RSC function, and whether and how it can be extrapolated to other scales. The main objective of this research is to study the scale effect on overland flow connectivity (RSC function). For this purpose, digital elevation data of a real field (9 × 3 m) and three synthetic fields (6 × 6 m) with contrasting hydrological responses were used, and the RSC function was calculated at different scales by changing the length (l) or width (w) of the field. To different extents depending on the microtopography, border effects were observed for the smaller scales when decreasing l or w, which resulted in a strong decrease or increase of the maximum depression storage, respectively. There was no scale effect on the RSC function when changing w, but a remarkable scale effect was observed in the RSC function when changing l. In general, for a given degree of filling of the depression storage, C decreased as l increased, the change in C being inversely proportional to the change in l. However, this observation applied only up to approx. 50–70% (depending on the hydrological response of the field) of filling of depression storage, after which no correlation was found between C and l. The results of this study help identify the minimal scale to study overland flow connectivity. At scales larger than the minimal scale, the RSC function showed a great potential to be extrapolated to other scales.

A sheet erodibility parameter for water erosion modeling in regions with low intensity rain

2013 ◽  
Vol 44 (6) ◽  
pp. 1013-1021 ◽  
Author(s):  
Mohammad H. Hussein
Keyword(s):  
Probability Distribution ◽  
Agricultural Land ◽  
Silty Clay ◽  
Storm Events ◽  
Sheet Flow ◽  
Northern Iraq ◽  
Flow Power ◽  
Normal Rainfall ◽  
Lognormal Probability ◽  
Sheet Erosion

Soil erodibility reflects the soil effect on the detachment process by rainfall and runoff; an evaluation of this parameter for single storm events was carried out using natural runoff plot data collected for two rainfall seasons in northern Iraq. The region is characterized by a semiarid Mediterranean-type climate with normal rainfall intensity below 20 mm/h and dominant sheet erosion on agricultural land. The plots were three 30 × 3 m and three 10 × 3 m, in fallow, situated on a 6% uniform slope; the soil at the site has a silty clay loam texture and belongs to the Calciorthid suborder. Sheet erosion rate was assumed linearly proportional to the storm power and the sheet flow power; a steady-state turbulent and kinematic sheet flow was also assumed. The results indicated a dominant detachment by rainfall with a substantial variability in storm by storm calculated sheet erodibility. The two-parameter lognormal probability distribution fitted the obtained sheet erodibility values reasonably well. Using this probability distribution, a representative sheet erodibility value of 0.056 × 10−3kg/J was obtained for use at the experimental site.

Evaluation of the potential to dispose of sewage-sludge. 1. Soil hydraulic and overland-flow properties of Pinus plantations in Queensland

Soil Research ◽  
1995 ◽  
Vol 33 (6) ◽  
pp. 1041 ◽  
Author(s):  
A Costantini ◽  
RJ Loch ◽  
SF Glanville ◽  
DN Orange
Keyword(s):  
Sewage Sludge ◽  
Ground Water ◽  
Overland Flow ◽  
Water Movement ◽  
Soil Surface ◽  
Water Infiltration ◽  
Podzolic Soils ◽  
Antecedent Conditions ◽  
Ground Water Pollution ◽  
Sludge Application

The studies reported in this paper were designed to evaluate the potential for disposal of sewage sludge in commercial Pinus plantations at Beerburrum, 50 km north of Brisbane. Soil descriptions and measurements of hydraulic properties were made in three soils, covering the range of perceived site suitability for sludge application. Disc permeameters and a rainfall simulator were used to characterize surface infiltration properties both with and without sludge, and ponded rings were used to assess permeability of the upper B horizon. Although surface hydraulic conductivities were potentially high, infiltration into dry soil was reduced by water repellence associated with fungal matting at the soil surface and mycelia extending through the Al horizon. Surface runoff could be generated from dry soils by relatively low intensity rainfall events, and the rate and volume of runoff was not increased by broadcast sludge application. Hydraulic conductivities of the upper Bt horizons in the lateritic and yellow podzolic soils were high, suggesting that persistent perched watertable development was unlikely. However, the presence of bleached A2 horizons and gleyed Bt horizons with prominent mottling in these soils were interpreted as evidence of periodic regional ground-water intrusion. By contrast, hydraulic conductivity in the Bt horizon of the soloth was low, suggesting that locally restricted drainage occurs. Likely pathways of water movement were inferred for three representative soil types in the proposed sludge application project. There is potential for both Hortonian runoff when antecedent conditions are dry, and saturated runoff during prolonged wet periods. Potential off-site pollution could therefore occur if either solids or solutes from the sludge are susceptible to transport. In addition, preferential how paths of water infiltration were demonstrated, and the potential for accelerated water and solute movement to ground watertables was inferred. The studies reported in this, and the second, paper in the series were used to appraise the potential for either surface water or ground water pollution from land-based sludge disposal.

Measuring Soil Loss and Subsequent Nutrient and Organic Matter Loss on Farmland

2017 ◽  
Author(s):  
Vito Ferro ◽  
Vincenzo Bagarello
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Soil Loss ◽  
Soil Structure ◽  
Overland Flow ◽  
Organic Matter Content ◽  
Matter Content ◽  
Water Infiltration ◽  
Surface Erosion ◽  
Rill Erosion

Field plots are often used to obtain experimental data (soil loss values corresponding to different climate, soil, topographic, crop, and management conditions) for predicting and evaluating soil erosion and sediment yield. Plots are used to study physical phenomena affecting soil detachment and transport, and their sizes are determined according to the experimental objectives and the type of data to be obtained. Studies on interrill erosion due to rainfall impact and overland flow need small plot width (2–3 m) and length (< 10 m), while studies on rill erosion require plot lengths greater than 6–13 m. Sites must be selected to represent the range of uniform slopes prevailing in the farming area under consideration. Plots equipped to study interrill and rill erosion, like those used for developing the Universal Soil Loss Equation (USLE), measure erosion from the top of a slope where runoff begins; they must be wide enough to minimize the edge or border effects and long enough to develop downslope rills. Experimental stations generally include bounded runoff plots of known rea, slope steepness, slope length, and soil type, from which both runoff and soil loss can be monitored. Once the boundaries defining the plot area are fixed, a collecting equipment must be used to catch the plot runoff. A conveyance system (H-flume or pipe) carries total runoff to a unit sampling the sediment and a storage system, such as a sequence of tanks, in which sediments are accumulated. Simple methods have been developed for estimating the mean sediment concentration of all runoff stored in a tank by using the vertical concentration profile measured on a side of the tank. When a large number of plots are equipped, the sampling of suspension and consequent oven-drying in the laboratory are highly time-consuming. For this purpose, a sampler that can extract a column of suspension, extending from the free surface to the bottom of the tank, can be used. For large plots, or where runoff volumes are high, a divisor that splits the flow into equal parts and passes one part in a storage tank as a sample can be used. Examples of these devices include the Geib multislot divisor and the Coshocton wheel. Specific equipment and procedures must be employed to detect the soil removed by rill and gully erosion. Because most of the soil organic matter is found close to the soil surface, erosion significantly decreases soil organic matter content. Several studies have demonstrated that the soil removed by erosion is 1.3–5 times richer in organic matter than the remaining soil. Soil organic matter facilitates the formation of soil aggregates, increases soil porosity, and improves soil structure, facilitating water infiltration. The removal of organic matter content can influence soil infiltration, soil structure, and soil erodibility.

Subsurface Application and Shallow Incorporation of Herbicides on Cotton

Weed Science ◽  
1968 ◽  
Vol 16 (4) ◽  
pp. 494-498 ◽  
Author(s):  
A. F. Wiese ◽  
E. B. Hudspeth
Keyword(s):  
Gossypium Hirsutum ◽  
Weed Control ◽  
Sandy Loam ◽  
Soil Surface ◽  
Sandy Loam Soil ◽  
Soil Types ◽  
Loam Soil

In a 3-year study on four soil types, subsurface application just ahead of a planter with a device that removed the top from the bed, applied a band of spray, and covered the band with soil reduced weed control in cotton (Gossypium hirsutum L.) obtained with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), 2,4-bis(isopropylamino)-6-methylmercapto-s-triazine (prometryne), 3-(hexahydro-4,7-methanoindan-5-yl)-1,1-dimethylurea (norea), dimethyl-2,3,5,6-tetrachloroterephthalate (DCPA), and 1,1-dimethyl-3(α,α,α,-trifluoro-m-tolyl)urea (fluometuron) compared to applications on the soil surface. This machine improved weed control with α,α,α,-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin). Shallow incorporation, with two helical blades, after planting increased weed control with trifluralin, diuron, and DCPA by 10% or more over the surface applications. This incorporator increased weed control obtained with prometryne and norea 5%. Very shallow incorporation, with metal tines, after planting improved weed control obtained with trifluralin and DCPA 18 and 11%, respectively. Weed control with norea was increased 7%, but metal tines did not appreciably affect weed control obtained with prometryne, diuron, or fluometuron. Compared to surface applications, incorporation increased cotton injury with diuron, norea, prometryne, and fluometuron on sandy loam soil.

Effects of Near Soil Surface Characteristics on Soil Detachment by Overland Flow in a Natural Succession Grassland

2014 ◽  
Vol 78 (2) ◽  
pp. 589-597 ◽  
Author(s):  
Bing Wang ◽  
Guang-Hui Zhang ◽  
X.C. Zhang ◽  
Zhen-Wei Li ◽  
Zi-Long Su ◽  
...  
Keyword(s):  
Overland Flow ◽  
Soil Surface ◽  
Surface Characteristics ◽  
Natural Succession

Using digital photogrammetry to monitor soil erosion under conditions of simulated rainfall and wind

Soil Research ◽  
2010 ◽  
Vol 48 (1) ◽  
pp. 36 ◽  
Author(s):  
S. Moritani ◽  
T. Yamamoto ◽  
H. Andry ◽  
M. Inoue ◽  
T. Kaneuchi
Keyword(s):  
Soil Erosion ◽  
Soil Surface ◽  
Specific Area ◽  
Algorithm Analysis ◽  
Simulated Rainfall ◽  
Digital Photogrammetry ◽  
Statistical Parameters ◽  
Surface Evolution ◽  
The Mean ◽  
Sheet Erosion

We investigated a method to measure sheet erosion by characterising the soil erosion of an upland field in a dryland environment. Digital photogrammetry was used to measure the erosion rates of soil surfaces packed to different densities under simulated rainfall or wind conditions. The photogrammetry system consisted of 2 digital cameras, a rainfall simulator, a wind tunnel, and a computer program for 3-dimensional algorithm analysis. First, we assessed the accuracy of our method by comparing conventionally measured data to photogrammetric data under conditions of either no rainfall or no wind application. Two statistical parameters were used to evaluate the soil surface evolution: the mean absolute error (MAE) and the mean relative error (MRE). Their values were 0.21 mm and 15.8%, respectively. We then assessed the precision of our system under simulated rainfall conditions using 3 different dry bulk densities for the packed saturated soil surface. At densities of 0.91, 0.98, and 1.09 g/cm3, the MAE (MRE) values were 2.21 mm (392.5%), 1.07 mm (126.4%), and 0.59 mm (57.6%), respectively. It was possible to monitor and evaluate both the amount of eroded soil and the erosion mechanism in a specific area. Moreover, this system could be applied to measuring wind erosion with an MAE accuracy as high as 0.21 mm. The digital elevation models (DEMs) allowed for detailed analyses of soil surface evolution, and it was also possible to monitor sheet erosion with high spatial and temporal resolutions.

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