scholarly journals Slope–Velocity–Equilibrium and evolution of surface roughness on a stony hillslope

2017 ◽  
Author(s):  
Mark A. Nearing ◽  
Viktor O. Polyakov ◽  
Mary H. Nichols ◽  
Mariano Hernandez ◽  
Li Li ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Rainfall Intensity ◽  
Overland Flow ◽  
Surface Condition ◽  
Relative Increase ◽  
Unique Function ◽  
Slope Gradient ◽  
Hydraulic Roughness ◽  
Artificial Rainfall ◽  
Discharge Rates

Abstract. Slope–velocity–equilibrium is hypothesized as a state that evolves naturally over time due to the interaction between overland flow and surface morphology, wherein steeper areas develop a relative increase in physical and hydraulic roughness such that flow velocity is a unique function of overland flow rate independent of slope gradient. This study tests this hypothesis under controlled conditions. Artificial rainfall was applied to 2 m by 6 m plots at 5 %, 12 %, and 20 % slope gradients. A series of simulations were made for each treatment with measurements of runoff rate, velocity, rock cover, and surface roughness. Velocities measured at the end of each experiment were a unique function of discharge rates, independent of slope gradient or rainfall intensity. Physical surface roughness was greater at steeper slopes. The data clearly showed that there was not a unique hydraulic coefficient for a given slope, surface condition, or rainfall rate, with hydraulic roughness greater at steeper slopes and lower intensities. This study supports the hypothesis of slope–velocity–equilibrium, implying that use of hydraulic equations, such as Chezy and Manning, in hillslope scale runoff models is problematic because the coefficients vary with both slope and rainfall intensity.

scholarly journals Slope–velocity equilibrium and evolution of surface roughness on a stony hillslope

2017 ◽  
Vol 21 (6) ◽  
pp. 3221-3229 ◽  
Author(s):  
Mark A. Nearing ◽  
Viktor O. Polyakov ◽  
Mary H. Nichols ◽  
Mariano Hernandez ◽  
Li Li ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Rainfall Intensity ◽  
Overland Flow ◽  
Surface Condition ◽  
Relative Increase ◽  
Unique Function ◽  
Slope Gradient ◽  
Hydraulic Roughness ◽  
Artificial Rainfall ◽  
Discharge Rates

Abstract. Slope–velocity equilibrium is hypothesized as a state that evolves naturally over time due to the interaction between overland flow and surface morphology, wherein steeper areas develop a relative increase in physical and hydraulic roughness such that flow velocity is a unique function of overland flow rate independent of slope gradient. This study tests this hypothesis under controlled conditions. Artificial rainfall was applied to 2 m by 6 m plots at 5, 12, and 20 % slope gradients. A series of simulations were made with two replications for each treatment with measurements of runoff rate, velocity, rock cover, and surface roughness. Velocities measured at the end of each experiment were a unique function of discharge rates, independent of slope gradient or rainfall intensity. Physical surface roughness was greater at steeper slopes. The data clearly showed that there was no unique hydraulic coefficient for a given slope, surface condition, or rainfall rate, with hydraulic roughness greater at steeper slopes and lower intensities. This study supports the hypothesis of slope–velocity equilibrium, implying that use of hydraulic equations, such as Chezy and Manning, in hillslope-scale runoff models is problematic because the coefficients vary with both slope and rainfall intensity.

Simulation of Runoff for Varying Mulch Coverage on a Sloped Surface

2013 ◽  
Vol 409-410 ◽  
pp. 339-343 ◽  
Author(s):  
Su Fang Cui ◽  
Ying Hua Pan ◽  
Quan Yuan Wu ◽  
Zhen Hua Zhang ◽  
Bao Xiang Zhang
Keyword(s):  
Soil Erosion ◽  
Rainfall Intensity ◽  
Overland Flow ◽  
Soil Surface ◽  
Northwest China ◽  
Slope Gradient ◽  
Soil Infiltration ◽  
Infiltration Capacity ◽  
Coverage Ratio ◽  
Runoff Volume

The use of thin plastic film to cover slope surfaces can lead to slope runoff and soil erosion in Loess hilly areas in northwest China. Three main factors (slope, rainfall intensity, and coverage ratio) were selected to analyze variations in runoff dynamics for a Lou soil surface and to obtain a theoretical foundation for practical application. The results indicate that for a fixed rainfall intensity and coverage ratio, a critical slope gradient close to 26.8% was observed. For a fixed coverage ratio and slope gradient, the cumulative runoff volume increased with the rainfall intensity. Overland flow varied with the coverage ratio and this can be attributed to increases in the cumulative runoff volume and runoff velocity with increasing coverage ratio. The experimental results show that for double-ridge cultivation with film mulching, the best coverage ratio is 50:150. This ratio not only reduces moisture evaporation and promotes soil conservation, but also effectively improves rainwater utilization and reduces soil erosion. In addition, for slope gradients exceeding 26.8%, runoff decreases and the soil infiltration capacity increases, so a slope gradient of 26.836.4% is optimal for the local cultivation model.

scholarly journals Effects of patterned Artemisia capillaris on overland flow resistance under varied rainfall intensities in the Loess Plateau of China

2014 ◽  
Vol 62 (4) ◽  
pp. 334-342 ◽  
Author(s):  
Guanhua Zhang ◽  
Guobin Liu ◽  
Liang Yi ◽  
Pingcang Zhang
Keyword(s):  
Rainfall Intensity ◽  
Overland Flow ◽  
Negative Relationship ◽  
Temporal Variations ◽  
Checkerboard Pattern ◽  
The Loess Plateau ◽  
Hydraulic Roughness ◽  
Artemisia Capillaris ◽  
Soil Erosion Rate ◽  
Slope Direction

Abstract In this paper simulated rainfall experiments in laboratory were conducted to quantify the effects oƒ patchy distributed Artemisia capillaris on spatial and temporal variations oƒ the Darcy-Weisbach friction coefficient (f). Different intensities oƒ 60, 90, 120, and 150 mm h-1 were applied on a bare plot (CK) and four different patched patterns: a checkerboard pattern (CP), a banded pattern perpendicular to slope direction (BP), a single long strip parallel to slope direction (LP), and a pattern with small patches distributed like the letter ‘X’ (XP). Each plot underwent two sets oƒ experiments, intact plant and root plots (the above-ground parts were removed). Results showed that mean ƒ for A. capillaris patterned treatments was 1.25-13.0 times oƒ that for CK. BP, CP, and XP performed more effectively than LP in increasing hydraulic roughness. The removal oƒ grass shoots significantly reduced f. A negative relationship was found between mean ƒ for the bare plot and rainfall intensity, whereas for grass patterned plots fr (mean ƒ in patterned plots divided by that for CK) increased exponentially with rainfall intensity. The ƒ -Re relation was best fitted by a power function. Soil erosion rate can be well described using ƒ by a power-law relationship

scholarly journals Mathematical Model of Ammonium Nitrogen Transport to Runoff with Different Slope Gradients under Simulated Rainfall

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 675 ◽  
Author(s):  
Weimin Xing ◽  
Peiling Yang ◽  
Chang Ao ◽  
Shumei Ren ◽  
Yao Xu
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Transfer Coefficient ◽  
Rainfall Intensity ◽  
Overland Flow ◽  
Nutrient Transport ◽  
Ammonium Nitrogen ◽  
Time Dependent ◽  
Nitrogen Transport ◽  
Slope Gradient

The removal of nutrients by overland flow remains a major source of non-point pollution in agricultural land. In this study, a mathematical model of ammonium nitrogen transport from soil solution to overland flow was established. The model treated the mass transfer coefficient (km) as a time-dependent parameter, which was not a constant value as in previous studies, and it was evaluated with a four-slope gradient and three rainfall intensities. The kinematic-wave equation for overland flow was solved by an approximately semi-analytical solution based on Philip’s infiltration model, while the diffusion-based mass conversation equation for overland nutrient transport was solved numerically. The results showed that the simulated runoff processes and ammonium nitrogen concentration transport to the overland flow agreed well with the experimental data. Further correlation analyses were made to determine the relationships between the slope gradient, rainfall intensity and the hydraulic and nutrient transport parameters. It turned out that these parameters could be described as a product of exponential functions of slope gradient and rainfall intensity. Finally, a diffusion-based model with a time-dependent mass transfer coefficient was established to predict the ammonium nitrogen transport processes at the experimental site under different slope gradients and rainfall intensities.

scholarly journals Phosphorus Loss through Overland Flow and Interflow from Bare Weathered Granite Slopes in Southeast China

2019 ◽  
Vol 11 (17) ◽  
pp. 4644 ◽  
Author(s):  
Deng ◽  
Fei ◽  
Sun ◽  
Zhang ◽  
Fan ◽  
...  
Keyword(s):  
Rainfall Intensity ◽  
Overland Flow ◽  
Slope Angle ◽  
Particulate Phosphorus ◽  
Limiting Factor ◽  
Southeast China ◽  
Dissolved Phosphorus ◽  
Weathered Granite ◽  
P Loss ◽  
Artificial Rainfall

Phosphorus (P) is the key limiting factor for eutrophication, and the mechanism of P loss from hillslopes is complex. Few attempts have been made to study the processes of P loss through overland flow and interflow from bare weathered granite slopes in Southeast China. Therefore, artificial rainfall simulations were performed to evaluate P loss from bare weathered granite slopes with different slope angles (5°, 8°, 15°, 25°) and different rainfall intensities (1.5, 2.0, 2.5 mm/min). The results show that overland flow increased with rainfall intensity, while it declined with slope angle. Interflow exhibited a single-peak curve with time of runoff. The interflow accounted for 28.53–89.12% of the total runoff yield, and the percentage declined with rainfall intensity and increased with slope angle. Both total phosphorus (TP) concentration (CTP) and TP load (LTP) in overland flow increased with rainfall intensity, and the percentages of LTP in each rainfall event ranged from 51% to 92%. CTP in overland flow distinctly fluctuated, with the maximum appearing on the 25° slope, while the maximum in interflow was observed on the 5° slope. LTP in overland flow was the highest on the 8° slope, and was significantly affected by runoff yield and rainfall intensity (p < 0.01). LTP in interflow was small and was significantly affected by rainfall intensity (p < 0.01). Runoff P was mainly lost through overland flow, dominantly in the form of particulate phosphorus (PP), and P loss through interflow was an important supplementation, mainly in the form of dissolved phosphorus (DP). These results provide underlying insights and scientific background for the control of P loss in bare weathered granite areas.

scholarly journals Vegetation cover effects on sediment concentration and overland flow under artificial rainfall intensity

2021 ◽  
Vol 71 (2) ◽  
pp. 135-150
Author(s):  
Mounia Boussaadi ◽  
Liatim Mouzai
Keyword(s):  
Flow Velocity ◽  
Vegetation Cover ◽  
Rainfall Intensity ◽  
Overland Flow ◽  
Plant Cover ◽  
Sediment Concentration ◽  
Mean Flow ◽  
Artificial Rainfall ◽  
The Impact ◽  
Cover Density

Soil erosion depends on a number of factors including rainfall intensity, density of plant cover, and area cover. The objective of this study is to investigate the impact of these factors on flow velocity, overland flow regimes, sediment concentration, and absolute soil detachment. The soil used in this study was sandy remolded agricultural soil. The soil is packed in a tray of 1 m2 fixed on a slope of 3%; five different intensities were simulated under different vegetation cover (density and area). The results indicated that the overland flow velocity with vegetation cover was best described by polynomial function. The mean flow velocity varied from 0.021 to 1.244 m/s. Overland flow regime is subcritical and laminar. However, there are significant relationships between the vegetation cover density and sediment concentration and absolute soil detachment. The sediment concentration ranged from 1.38 to 5.65 kg/m3 whereas the absolute soil detachment ranged from 0.021?10-3 to 1.244?10-3 kg/m2/s. Finally, the vegetation cover presented a good protector to soil sediment from erosion.

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.

The effect of rainfall intensity on soil erosion and particulate phosphorus transfer from arable soils

1999 ◽  
Vol 39 (12) ◽  
pp. 41-45 ◽  
Author(s):  
A. I. Fraser ◽  
T. R. Harrod ◽  
P. M. Haygarth
Keyword(s):  
Soil Erosion ◽  
Suspended Sediment ◽  
Rainfall Intensity ◽  
Overland Flow ◽  
Agricultural Soils ◽  
Arable Land ◽  
Significant Proportion ◽  
Particulate Phosphorus ◽  
Arable Soils ◽  
Flow Monitoring

Soil erosion, in the form of transported suspended sediment in overland flow, is often associated with high rates of particulate phosphorus (PP) (total P&gt;0.45 μm) transfer from land to watercourses. Particulate P may provide a long-term source of P for aquatic biota. Twenty-two sites for winter overland flow monitoring were selected in south-west England within fields ranging from 0.2–3.8 ha on conventionally-managed arable land. Fields were situated on highly porous, light textured soils, lacking impermeable horizons and often overlying major aquifers. Long arable use and modern cultivation methods result in these soils capping under rain impact. Overland flow was observed when rainfall intensity approached the modest rate of 0.8 mm hr−1 on land at or near to field capacity. Low intensity rainfall (&lt;2 mm hr−1) produced mean suspended sediment losses of 14 kg ha−1 hr−1, with associated PP transfer rates of 16 g ha−1 hr−1. In high intensity rainfall (&gt;9 mm hr−1) mean PP losses of 319 g ha−1 hr−1 leaving the field were observed. As might be expected, there was a good relationship between PP and suspended sediment transfer in overland flow leaving the sites. The capacity of light soils to cap when in arable use, combined with heavy or prolonged rainfall, resulted in substantial discharges, soil erosion and associated PP transfer. Storms with heavy rain, typically of only a few hours duration, were characterised by considerable losses of PP. Such events, with return periods of once or twice a winter, may account for a significant proportion of total annual P transfer from agricultural soils under arable crops. However, contributions from less intense rain with much longer duration (around 100 hours per winter in many arable districts of the UK) are also demonstrated here.

Characteristics of Non-Point Source N Export via Surface Runoff from Sloping Croplands in Northeast China

2011 ◽  
Vol 347-353 ◽  
pp. 2302-2307 ◽  
Author(s):  
Hong Xiang Wang ◽  
Yi Shi ◽  
Jian Ma ◽  
Cai Yan Lu ◽  
Xin Chen
Keyword(s):  
Point Source ◽  
Surface Runoff ◽  
Rainfall Intensity ◽  
Inorganic Nitrogen ◽  
Rainfall Amount ◽  
Organic N ◽  
Dissolved Inorganic Nitrogen ◽  
Slope Gradient ◽  
N Loss ◽  
Total N

A field experiment was conducted to study the characteristics of non-point source nitrogen (N) in the surface runoff from sloping croplands and the influences of rainfall and cropland slope gradient. The results showed that dissolved total N (DTN) was the major form of N in the runoff, and the proportion occupied by dissolved inorganic nitrogen (DIN) ranged from 45% to 85%. The level of NH4+-N was generally higher than the level of NO3--N, and averaged at 2.50 mg·L-1and 1.07 mg·L-1respectively. DIN was positively correlated with DTN (R2=0.962). Dissolved organic N (DON) presented a moderate seasonal change and averaged at 1.40 mg·L-1. Rainfall amount and rainfall intensity significantly affected the components of DTN in the runoff. With the increase of rainfall amount and rainfall intensity, the concentrations of DTN, NH4+-N and NO3--N presented a decreased trend, while the concentration of DON showed an increased trend. N loss went up with an increase in the gradient of sloping cropland, and was less when the duration was longer from the time of N fertilization.fertilization.

Spatial heterogeneity of surface roughness during different erosive stages of tilled loess slopes under a rainfall intensity of 1.5mmmin−1

2015 ◽  
Vol 153 ◽  
pp. 95-103 ◽  
Author(s):  
Qingfeng Zhang ◽  
Jian Wang ◽  
Longshan Zhao ◽  
Faqi Wu ◽  
Zhiyi Zhang ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Spatial Heterogeneity ◽  
Rainfall Intensity
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