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1.
The objective of this study was to determine the changing characteristics of soil surface roughness under different rainfall intensities and examine the interaction between soil surface roughness and different water erosion processes. Four artificial management practices (raking cropland, artificial hoeing, artificial digging, and contour tillage) were used according to the local agriculture customs of the Loess Plateau of China to simulate different types of soil surface roughness, using an additional smooth slope for comparison purposes. A total of 20 rainfall simulation experiments were conducted in five 1 m by 2 m boxes under two rainfall intensities (0.68 and 1.50 mm min?1) on a 15° slope. During splash erosion, soil surface roughness decreased in all treatments except raking cropland and smooth baseline under rainfall intensity of 0.68 mm min?1, while increasing for all treatments except smooth baseline under rainfall intensity of 1.50 mm min?1. During sheet erosion, soil surface roughness decreased for all treatments except hoeing cropland under rainfall intensity of 0.68 mm min?1. However, soil surface roughness increased for the artificial hoeing and raking cropland under rainfall intensity of 1.50 mm min?1. Soil surface roughness has a control effect on sheet erosion for different treatments under two rainfall intensities. For rill erosion, soil surface roughness increased for raking cropland and artificial hoeing treatments, and soil surface roughness decreased for artificial digging and the contour tillage treatments under two rainfall intensities. Under rainfall intensity of 0.68 mm min?1, the critical soil surface roughness was 0.706 cm for the resistance control of runoff and sediment yield. Under rainfall intensity of 1.50 mm min?1, the critical soil surface roughness was 1.633 cm for the resistance control of runoff, while the critical soil surface roughness was 0.706 cm for the resistance control of sediment yield. These findings have important implications for clarifying the erosive nature of soil surface roughness and harnessing sloped farmland. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
2.
Water flow velocity is an important hydraulic variable in hydrological and soil erosion models, and is greatly affected by freezing and thawing of the surface soil layer in cold high-altitude regions. The accurate measurement of rill flow velocity when impacted by the thawing process is critical to simulate runoff and sediment transport processes. In this study, an electrolyte tracer modelling method was used to measure rill flow velocity along a meadow soil slope at different thaw depths under simulated rainfall. Rill flow velocity was measured using four thawed soil depths (0, 1, 2 and 10 cm), four slope gradients (5°, 10°, 15° and 20°) and four rainfall intensities (30, 60, 90 and 120 mm·h−1). The results showed that the increase in thawed soil depth caused a decrease in rill flow velocity, whereby the rate of this decrease was also diminishing. Whilst the rill flow velocity was positively correlated with slope gradient and rainfall intensity, the response of rill flow velocity to these influencing factors varied with thawed soil depth. The mechanism by which thawed soil depth influenced rill flow velocity was attributed to the consumption of runoff energy, slope surface roughness, and the headcut effect. Rill flow velocity was modelled by thawed soil depth, slope gradient and rainfall intensity using an empirical function. This function predicted values that were in good agreement with the measured data. These results provide the foundation for a better understanding of the effect of thawed soil depth on slope hydrology, erosion and the parameterization scheme for hydrological and soil erosion models. 相似文献
3.
Shaozhong Kang Lu Zhang Xiaoyu Song Shuhan Zhang Xianzhao Liu Yinli Liang Shiqing Zheng 《水文研究》2001,15(6):977-988
Soil erosion is a severe problem hindering sustainable agriculture on the Loess Plateau of China. Plot experiments were conducted under the natural rainfall condition during 1995–1997 at Wangdongguo and Aobao catchments in this region to evaluate the effects of various land use, cropping systems, land slopes and rainfall on runoff and sediment losses, as well as the differences in catchment responses. The experiments included various surface conditions ranging from bare soil to vegetated surfaces (maize, wheat residue, Robinia pseudoacacia L., Amorpha fruticosa L., Stipa capillata L., buckwheat and Astragarus adsurgens L.). The measurements were carried out on hill slopes with different gradients (i.e. 0 ° to 36 °). These plots varied from 20 to 60 m in length. Results indicated that runoff and erosion in this region occurred mainly during summer storms. Summer runoff and sediment losses under cropping and other vegetation were significantly less than those from ploughed bare soil (i.e. without crop/plant or crop residue). There were fewer runoff and sediment losses with increasing canopy cover. Land slope had a major effect on runoff and sediment losses and this effect was markedly larger in the tillage plots than that in the natural grass and forest plots, although this effect was very small when the maximum rainfall intensity was larger than 58·8 mm/h or smaller than 2·4 mm/h. Sediment losses per unit area rose with increasing slope length for the same land slope and same land use. The effect of slope length on sediment losses was stronger on a bare soil plot than on a crop/plant plot. The runoff volume and sediment losses were both closely related to rainfall volume and maximum intensity, while runoff coefficient was mainly controlled by maximum rainfall intensity. Hortonian overland flow is the dominant runoff process in the region. The differences in runoff volume, runoff coefficient and sediment losses between the catchments are mainly controlled by the maximum rainfall intensity and infiltration characteristics. The Aobao catchment yielded much larger runoff volume, runoff coefficient and sediment than the Wangdongguo catchment. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
4.
Effect of shrub-grass vegetation coverage and slope gradient on runoff and sediment yield under simulated rainfall 总被引：4，自引：1，他引：3
Evaluating the benefits of sediment and runoff reduction in different vegetation types is essential for studying the mechanisms of soil and water conservation on the Loess Plateau.The experiment was conducted in shrub-grass plots with nine levels of mixed vegetation coverage from 0%to 70%,three slopes(10,15,and 20)and two rainfall intensities(1.0 and 2.5 mm/min).The results showed that the vegetation coverage and slope gradient significantly affect runoff and sediment yield.Shrub-grass vegetation coverage had a significant effect on the runoff start-time,runoff flow velocity,runoff rate,and soil erosion rate on hillslopes.Mixed vegetation coverage could effectively delay the runoff starttime and decrease the runoff flow velocity.However,the effects of the slope gradient on runoff and sediment yield are opposite to those of vegetation coverage.Shrub-grass vegetation coverage could effectively increase runoff and sediment yield reduction benefits,while their benefits were affected by the rainfall intensity.At the 1.0 mm/min rainfall intensity,the reduction in the sediment production rate was greater than that under the 2.5 mm/min intensity.However,when the shrub-grass vegetation coverage exceeded 42%,the runoff reduction benefit was more obvious at higher rainfall intensities.The cumulative sediment yield increased with increasing cumulative runoff,and the rate of increase in the cumulative runoff was greater than that of the cumulative sediment yield with increasing of shrub-grass vegetation coverage.Moreover,there was a power function relationship between cumulative sediment yield and cumulative runoff yield(P<0.05).Our paper is expected to provide a good reference on the ecological environment and vegetation construction on the Loess Plateau. 相似文献
5.
The Qinghai–Tibet Plateau has a vast area of approximately 70×104 km2 of alpine meadow under the impacts of soil freezing and thawing, thereby inducing intensive water erosion. Quantifying the rainfall erosion process of partially thawed soil provides the basis for model simulation of soil erosion on cold-region hillslopes. In this study, we conducted a laboratory experiment on rainfall-induced erosion of partially thawed soil slope under four slope gradients (5, 10, 15, and 20°), three rainfall intensities (30, 60, and 90 mm h−1), and three thawed soil depths (1, 2, and 10 cm). The results indicated that shallow thawed soil depth aggravated soil erosion of partially thawed soil slopes under low hydrodynamic conditions (rainfall intensity of 30 mm h−1 and slope gradient ≤ 15°), whereas it inhibited erosion under high hydrodynamic conditions (rainfall intensity ≥ 60 mm h−1 or slope gradient > 15°). Soil erosion was controlled by the thawed soil depth and runoff hydrodynamic conditions. When the sediment supply was sufficient, the shallow thawed soil depth had a higher erosion potential and a larger sediment concentration. On the contrary, when the sediment supply was insufficient, the shallow thawed soil depth resulted in lower sediment erosion and a smaller sediment concentration. The hydrodynamic runoff conditions determined whether the sediment supply was sufficient. We propose a model to predict sediment delivery under different slope gradients, rainfall intensities, and thawed soil depths. The model, with a Nash–Sutcliffe efficiency of 0.95, accurately predicted the sediment delivery under different conditions, which was helpful for quantification of the complex feedback of sediment delivery to the factors influencing rainfall erosion of partially thawed soil. This study provides valuable insights into the rainfall erosion mechanism of partially thawed soil slopes in the Qinghai–Tibet Plateau and provides a basis for further studies on soil erosion under different hydrodynamic conditions. 相似文献
6.
《国际泥沙研究》2022,37(5):653-661
Granite red soil (GRS) and Quaternary red clay (QRC) are two typical erodible soils in the red-soil region of southern China. Analytical and comparative studies of the characteristics of runoff and sediment yield for the two soils at various slopes are currently needed. The purpose of the current study was to clarify the characteristics of runoff and sediment yield for GRS and QRC at different slopes and to establish models for estimating sediment yield for the two soils. Forty-eight runoff microplots with four slopes (5°, 15°, 25°, and 35°) and two soils (GRS and QRC) were established and exposed to natural rainfall. Runoff and sediment yield were measured 10 times during the study period. Runoff and sediment yield for the two soils under the various slopes had similar temporal variations, and both increased with prior cumulative erosive rainfall. Runoff for GRS and QRC was moderately temporally variable, with coefficients of variation (CVs) from 46.2% to 60.6%, and sediment yield for QRC was strongly temporally variable, with CVs from 114.8% to 145.8%. Sediment yield for GRS increased with slope, but sediment yield for QRC first increased and then decreased, with a calculated inflection point of 18°, but runoff for both soils decreased with slope. The CVs of both runoff and sediment yield with slope for the two soils ranged from 3.6% to 88.0%, lower than the temporal variabilities, indicating that rainfall may have a larger impact than slope on runoff and sediment yield for QRC and GRS. Under the various slopes, runoff and sediment yield for both soils increased with rainfall and sediment yield increased with runoff, but the proportions of effective rainfall and runoff differed. Pedotransfer-function models based on rainfall, runoff, and slope accurately estimated sediment yield for the two soils, with the model fit coefficient of determination (R2) > 0.81 and the R2 for verification >0.79. These results improve the understanding of the laws governing erosion for different soil types in the red-soil region of southern China and are important for managing the erosion of collapsing gullies and sloping farmland in the region. 相似文献
7.
Assessing the impacts of microtopography on soil erosion under simulated rainfall,using a multifractal approach 
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下载免费PDF全文 This study aimed to investigate the changing characteristics of microrelief of purple soil and its erosional response during successive stages of water erosion, including splash erosion, sheet erosion, and rill erosion. Methods employed included a rainfall simulator and the use of a laser scanner to generate a digital elevation model. Three artificial tillage practices, including conventional tillage (CT), artificial digging (AD), and ridge tillage (RT), were used to simulate different microrelief patterns. Eighteen artificial rainfall experiments were conducted using three 2 × 1 m boxes with a rainfall intensity of 1.5 mm min?1 on a 15° slope. The results showed that the soil roughness (SR) index values for the tillage slopes were RT > AD > CT. The combined effects of detachment by raindrop impact and transport by run‐off decreased the SR index, whereas rill erosion increased the SR index during rainfall event. Microtopography and drainage networks have strong multifractal behaviours. The multifractal parameters of microtopography reflect the overall characteristics as well as the characteristics of the local soil surface. Within a certain range of threshold values, higher microrelief causes less soil erosion. However, when the parameters of spatial heterogeneity of microtopography exceed the threshold values, a higher degree of microrelief can increase soil erosion. These results help clarify the effect of microtopography on soil erosion and provide a theoretical foundation to guide future tillage practices on sloping farmland of purple soil. 相似文献
8.
Water erosion on hillslopes is a worldwide environmental problem, which is a rainfall‐induced process, especially extreme rainfall. The great intensity of extreme rainfall strongly enhances the power of overland flow to detach soil and transport sediment. Plant litter is one of the most important constituents of ecosystems that often covers the soil surface and can be incorporated into topsoil. However, little attention has been paid to its effect on flow hydraulics owing to the veiled nature. This study aimed to examine the effects of incorporated litter on the hydraulic properties under extreme rainfall condition. To reach this goal, six litter rates of 0, 0.05, 0.10, 0.20, 0.35, and 0.50 kg m?2 and four litter types collected from deciduous trees, coniferous trees, shrubs, and herbs were incorporated into topsoil. Then, simulated rainfall experiments were performed on five slope gradients (5°, 10°, 15°, 20°, and 25°) with an extreme rainfall intensity of 80 mm h?1. The results showed that Froude number and flow velocity of the overland flow decreased, whereas flow resistance increased exponentially with litter incorporation rate. Litter type had an influence on flow hydraulics, which can mainly be attributed to the variations in surface coverage of the exposed litter and the litter morphology. Flow velocity and Darcy–Weisbach coefficient increased markedly with slope gradient. However, the variation of slope gradient did not modify the relationships between flow hydraulics and incorporated litter rate. The random roughness, resulting from heterogeneous erosion due to the uneven protection of surface exposed litter, increased linearly with litter incorporated rate. As rainfall proceeded, flow hydraulics varied with incorporated litter rate and slope gradient complicatedly due to the increases in flow rate and coverage of the exposed litter and the modification of soil surface roughness. 相似文献
9.
Influences of grass and moss on runoff and sediment yield on sloped loess surfaces under simulated rainfall 总被引：1，自引：0，他引：1
It is important to evaluate the impacts of grasses on soil erosion process so as to use them effectively to control soil and water losses on the Loess Plateau. Laboratory-simulated rainfall experiments were conducted to investigate the runoff and sediment processes on sloped loess surfaces with and without the aboveground parts of grasses and moss (GAM: grass and moss; NGAM: no grass and moss) under slope gradients of 5°, 10°, 15°, 20°, 25° and 30°. The results show that runoff from GAM and NGAM plots increased up to a slope gradient of 10° and decreased thereafter, whereas the runoff coefficients increased with gradient. The average runoff rates and runoff coefficients of NGAM plots were less than those of GAM plots except for the 5° slope. This behaviour may be due to the reduction in water infiltration under moss. The difference between GAM and NGAM plots in average runoff rates varied from 1·4 to 8%. At the same gradients, NGAM plots yielded significantly (α = 0·05) more sediment than GAM plots. Average sediment deliveries for different slopes varied from 0·119 to 3·794 g m−2 min−1 from GAM plots, and from 0·765 to 16·128 g m−2 min−1 from NGAM plots. Sediment yields from GAM plots were reduced by 45 to 85%, compared with those from the NGAM plots. Plots at 30° yielded significantly higher sediments than at the other gradients. Total sediments S increased with slope gradients G in a linear form, i.e. S = 9·25G − 39·6 with R2 = 0·77*, for the GAM plots, and in an exponential model, i.e. S = 40·4 exp(0·1042G) with R2 = 0·93**, for the NGAM plots. In all cases, sediment deliveries decreased with time, and reached a relative steady state at a rainfall duration of 14 min. Compared with NGAM plots, the final percentage reductions in sediment delivery from GAM plots were higher than those at the initial time of rainfall at all slopes. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
10.
The complex interactions between rainfall‐driven erosion processes and rainfall characteristics, slope gradient, soil treatment and soil surface processes are not very well understood. A combination of experiments under natural rainfall and a consistent physical theory for their interpretation is needed to shed more light on the underlying processes. The present study demonstrates such a methodology. An experimental device employed earlier in laboratory studies was used to measure downslope rain splash and ‘splash‐creep’, lateral splash, upslope splash and rainfall‐driven runoff transport (wash) from a highly aggregated clay‐rich oxisol exposed to natural rainfall in West Java, Indonesia. Two series of measurements were made: the first with the soil surface at angles of 0°, 5°, 15° and 40°; and the second all at an angle of 5° but with different tillage and mulching treatments. A number of rainfall erosivity indices were calculated from rainfall intensity measurements and compared with measured transport components. Overall storm kinetic energy correlated reasonably well with sediment transport, but much better agreement was obtained when a threshold rainfall intensity (20 mm h?1) was introduced. Rain splash transport measurements were interpreted using a recently developed theory relating detachment to sediment transport. Furthermore, a conceptually sound yet simple wash transport model is advanced that satisfactorily predicted observed washed sediment concentrations. The lack of replication precluded rigorous assessment of the effect of slope and soil treatment on erosion processes, but some general conclusions could still be drawn. The results stress the importance of experiments under conditions of natural rainfall. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
11.
Rill erosion is a serious concern in the hilly region of China with purple soil, and maize is extensively cultivated in this region. Evaluations of the dynamic mechanisms of rill erosion in sloping farmland areas are particularly important during the maize growing season to determine whether rill erosion can occur. A new ridge tillage (RT) system was designed using local agricultural methods in China. Twelve artificial rainfall experiments were conducted in three 1 × 2 m experimental plots with a slope of 15°, which is a typical slope in the study area. The rainfall intensities were designated as 1.0, 1.5, and 2.0 mm min?1. The rainfall experiments were performed in the field to determine the characteristics of run‐off and sediment transport related to rill erosion processes during different stages of maize growth and to analyse how hydraulic parameters and the sediment yield of the rill erosion process are related. The results showed that rill flow patterns were mainly classified as subcritical transition flow during all the growth stages of maize. The effects of hydrodynamic parameters on the sediment yield were ordered as follows: Reynolds number > stream power > Froude number > shear stress. The total sediment yield varied by stage as follows: seedling stage > jointing stage > mature stage > tasseling stage. The sediment yield and run‐off rate exhibited a linear relationship that was well described at the hillslope scale. To initiate soil loss in sloping farmland areas with purple soil during the maize growing season, the critical hydrodynamic shear stress and stream power must be at least 46.505 Pa and 1.541 N m?1 s?1, respectively. 相似文献
12.
Surface microrelief changes affect the soil and water conservation benefits of rainwater harvesting tillage operation during rainfall events 总被引：1，自引：0，他引：1
Reservoir tillage (RT) improves the soil rainwater harvesting capacity and reduces soil erosion on cropland, but there is some debate regarding its effectiveness. The objective of this study was to further verify the effect of RT on soil erosion and explore the reasons for this effect by analysing microrelief changes during rainfall. Rainfall intensities of 60, 90, and 120 mm/hr and three slope degrees (5, 15, and 25°, representing gentle, medium, and steep slopes) were considered. A smooth surface (SS) served as the control. The microrelief changes were determined based on digital elevation models, which were measured using a laser scanner with a 2‐cm grid before and after rainfall events. The results showed that compared with the values for the SS, RT reduced both the runoff and sediment by approximately 10‐20% on the gentle slope; on the medium slope, although RT also reduced the runoff in the 90‐ and 120‐mm/hr intensity rainfall events, the sediment increased by 158.90% and 246.08%; on the steep slope, the sediment increased by 92.33 to 296.47%. Overall, when the runoff control benefit of RT was lower than 5%, there was no sediment control benefit. RT was effective at controlling soil loss on the gentle slopes but was not effective on the medium and steep slopes. This is because the surface depressions created by RT were filled in with sediment that eroded from the upslopes, and the surface microrelief became smoother, which then caused greater soil and water loss than that on an SS at the later rainfall stage. 相似文献
13.
Analysis of surface roughness in relation to soil loss and runoff at high rainfall intensities 总被引：1，自引：0，他引：1
The decay of roughness is an important factor governing surface processes such as infiltration and soil erosion. Thus the decay of surface roughness under different surface conditions was investigated and related to quantitative amounts of soil loss, runoff and sediment concentration in a laboratory experiment. Rainfall with an intensity of 128 mm/h was applied to a bare or mulched surfaces of a sandy loam soil with known surface roughness at specified time intervals. The decay of roughness as expressed by roughness ratio, in this experiment, was better predicted when related to an exponential function of the square root of cumulative kinetic energy of rainfall rather than with the cumulative rainfall. The roughness decay equations in literature did not predict breakdown under mulched surfaces accurately. Thus the exponent parameters of the roughness decay equations were adjusted to reflect the reduced decay occurring under mulched surfaces. In a bare soil, regression equations expressing the dependent variables as a function of initial roughness index were significant, but with low coefficients of determination, being 0·39 for soil loss, 0·12 for runoff and 0·36 for sediment concentration. In addition to initial roughness index, cumulative kinetic energy of rainfall was further included in the regressions. This led to an increase in coefficients of determination, which was 0·81 for soil loss, 0·74 for runoff and 0·49 for sediment concentration. The coefficients of determination (0·87 for soil loss, 0·85 for runoff and 0·51 for sediment concentration) were further increased when the final roughness index was included in addition to initial roughness index and cumulative kinetic energy in the regressions. This work shows that soil loss and runoff could be predicted from bare soil surface provided the initial roughness and the energy of rainfall is known. However, field verifications of these relationships are needed under different tillage tools and under natural rainfall. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
14.
Effects of different spatial distributions of physical soil crusts on runoff and erosion on the Loess Plateau in China 总被引：1，自引：0，他引：1 下载免费PDF全文
下载免费PDF全文 The response of runoff and erosion to soil crusts has been extensively investigated in recent decades. However, there have been few attempts to look at the effects of spatial configuration of different soil crusts on erosion processes. Here we investigated the effects of different spatial distributions of physical soil crusts on runoff and erosion in the semi‐arid Loess Plateau region. Soil boxes (1.5 m long × 0.2 m wide) were set to a slope of 17.6% (10°) and simulated rainfall of 120 mm h?1 (60 minutes). The runoff generation and erosion rates were determined for three crust area ratios (depositional crust for 20%, 33%, and 50% of the total slope) and five spatial distribution patterns (depositional crust on the lower, lower‐middle, middle, mid‐upper, and upper slope) of soil crusts. The reduction in sediment loss (‘sediment reduction’) was calculated to evaluate the effects of different spatial distributions of soil crusts on erosion. Sediment yield was influenced by the area ratio and spatial position of different soil crusts. The runoff rate reached a steady state after an initial trend of unsteadily increasing with increasing rainfall duration. Sediment yield was controlled by detachment limitation and then transport limitation under rainfall. The shifting time of erosion from a transport to detachment‐limiting regime decreased with increasing area of depositional crust. No significant differences were observed in the total runoff among treatments, while the total sediment yield varied under different spatial distributions. At the same area ratio, total sediment yield was the largest when the depositional crust was on the upper slope, and it was smallest when the crust was deposited on the lower slope. The sediment reduction of structural crust (42.5–66.5%) was greater than that of depositional crust (16.7–34.3%). These results provide a mechanistic understanding of how different spatial distributions of soil crusts affect runoff and sediment production. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
15.
1 INTRODUCTION Soil erosion at the hilly-gully region of the Loess Plateau has obvious vertical erosion zones from watershed boundary to gully edge, i.e., sheet erosion-dominated zone, rill erosion-dominated zone and shallow gully erosion-dominated zone, from top to bottom (Chen et al., 1988). Meanwhile, upslope runoff and sediment have a significant impact on the downslope erosion process. But with the limits of research methods,there is not much data to quantify upslope runoff and sedi… 相似文献
16.
A mathematical model was developed for simulating runoff generation and soil erosion on hillslopes. The model is comprised of three modules: one for overland flow, one for soil infiltration, and one for soil erosion including rill erosion and interrill erosion. Rainfall and slope characteristics affecting soil erosion on hillslopes were analysed. The model results show that the slope length and gradient, time distribution rainfall, and distribution of rills have varying influence on soil erosion. Erosion rate increases nonlinearly with increase in the slope length; a long slope length leads to more serious erosion. The effect of the slope gradient on soil erosion can be both positive and negative. Thus, there exists a critical slope gradient for soil erosion, which is about 45° for the rate of erosion at the end of the slope and about 25° for the accumulated erosion. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
17.
Hongwu Zhang Guangquan Liu Chensu Zhao Luohao Zhang Qiang Zhang Heng Fu Shuai Cao 《国际泥沙研究》2023,38(1):24-32
A typical gully sub-basin with a complex geomorphological form is used to do a model test of gravity erosion of loess by considering the sequence of slopes in a prototype gully creating a sequence of underlying surface forms in the upper reaches. The results show that the runoff from heavy rainfall is the main external force for the erosion of loess, and also is an important influencing factor to stimulate and intensify the development of gravity erosion. The soil structure and the height of the... 相似文献
18.
Soil erosion in sloping cropland is a key water and soil conservation issue in the Loess Plateau region, China. How surface roughness influences soil detachment remains unclear due to the inconsistent results obtained from existing studies. The objectives of the present study were to evaluate the effects of tillage practices on soil detachment rate in sloping cropland and establish an accurate empirical model for the prediction of soil detachment rates. A series of movable bed experiments were conducted on sloping surfaces under three different tillage practices (manual dibbling, manual hoeing, and contour drilling), with a smooth surface (non-tillage) as a control. The research indicated that soil detachment rate significantly increased with roughness (p < 0.05) since the average soil detachment rate was the highest under the contour drilling treatment (6.762 g m−2 s−1), followed by manual hoeing (4.180 g m−2 s−1), and manual dibbling (3.334 g m−2 s−1); the lowest detachment rate was observed under the non-tillage treatment (3.214 g m−2 s−1). Slope gradient and unit discharge rate were positively correlated with soil detachment rate and proved to be more influential than soil surface roughness. Four composite hydraulic parameters were introduced to estimate soil detachment rate on tilled surfaces. Regression analyses revealed that stream power was the most effective predictor of soil detachment rate compared with unit length shear force, shear stress, and unit stream power. By integrating surface roughness as a variable, the detachment rate could be accurately described as a nonlinear function of stream power and surface roughness. The results of the present study indicate that tillage practice could influence soil loss on sloping cropland, considering the higher soil detachment rates under all tillage practices tested compared with non-tillage. The results are attributed mainly to concentrated flow caused by the high water storage levels on tilled surfaces, which could damage surface microtopography and, subsequently, the development of headcuts. 相似文献
19.
Numerical simulation experiments of water erosion at the local scale (20 × 5 m) using a process‐based model [Plot Soil Erosion Model_2D (PSEM_2D)] were carried out to test the effects of various environmental factors (soil type, meteorological forcing and slope gradient) on the runoff and erosion response and to determine the dominant processes that control the sediment yield at various slope lengths. The selected environmental factors corresponded to conditions for which the model had been fully tested beforehand. The use of a Green and Ampt model for infiltration explained the dominant role played by rainfall intensity in the runoff response. Sediment yield at the outlet of the simulated area was correlated positively with rainfall intensity and slope gradient, but was less sensitive to soil type. The relationship between sediment yield (soil loss per unit area) and slope length was greatly influenced by all environmental factors, but there was a general tendency towards higher sediment yield when the slope was longer. Contribution of rainfall erosion to gross erosion was dominant for all surfaces with slope lengths ranging from 4 to 20 m. The highest sediment yields corresponded to cases where flow erosion was activated. An increase in slope gradient resulted in flow detachment starting upstream. Sediment exported at the outlet of the simulated area came predominantly from the zone located near the outlet. The microrelief helped in the development of a rill network that controlled both the ratio between rainfall and flow erosion and the relationship between sediment yield and slope length. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
20.
Effects of rainfall and slope on runoff,soil erosion and rill development: an experimental study using two loess soils 总被引：3，自引：0，他引：3 下载免费PDF全文
下载免费PDF全文 Runoff generation and soil loss from slopes have been studied for decades, but the relationships among runoff, soil loss and rill development are still not well understood. In this paper, rainfall simulation experiments were conducted in two neighbouring plots (scale: 1 m by 5 m) with four varying slopes (17.6%, 26.8%, 36.4% and 46.6%) and two rainfall intensities (90 and 120 mm h?1) using two loess soils. Data on rill development were extracted from the digital elevation models by means of photogrammetry. The effects of rainfall intensity and slope gradient on runoff, soil loss and rill development were different for the two soils. The runoff and soil loss from the Anthrosol surface were generally higher than those from the Calcaric Cambisol surface. Higher rainfall intensity produced less runoff and more sediment for almost each treatment. With increasing slope gradient, the values of cumulative runoff and soil loss peaked, except for the treatments with 90 mm h?1 rainfall on the slopes with Anthrosol. With rainfall duration, runoff discharge decreased for Anthrosol and increased for Calcaric Cambisol for almost all the treatments. For both soils, sediment concentration was very high at the onset of rainfall and decreased quickly. Almost all the sediment concentrations increased on the 17.6% and 26.8% slopes and peaked on the 36.4% and 46.6% slopes. Sediment concentrations were higher on the Anthrosol slopes than on the Calcaric Cambisol slopes. At 90 mm h?1 rainfall intensity, increasingly denser rills appeared on the Anthrosol slope as the slope gradient increased, while only steep slopes (36.4% and 46.6%) developed rills for the Calcaric Cambisol soil. The contributions of rill erosion ranged from 36% to 62% of the cumulative soil losses for Anthrosol, while the maximum contribution of rill erosion to the cumulative soil loss was only 37.9% for Calcaric Cambisol. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献