Experimental study on dynamic mechanism of sheet erosion processes on steep grassland in the loess region of China

2021 ◽  
Author(s):  
Qi Guo ◽  
Zhanli Wang
Keyword(s):  
Shear Stress ◽  
Soil Erosion ◽  
Power Function ◽  
Erosion Rate ◽  
Dynamic Mechanism ◽  
Erosion Process ◽  
Stream Power ◽  
Study Results ◽  
Loess Region ◽  
Sheet Erosion

<p>Sheet erosion has been the major erosion process on steep grassland since the Grain-for-Green project was implemented in 1999 in the Loess Plateau with serious soil erosion, in China. Quantifying sheet erosion rate on steep grassland could improve soil erosion estimation on loess hillslopes and provide scientific support for effectively controlling soil erosion and rationally managing grassland. Simulated rainfall experiments were conducted on grassland plot with vegetation coverage of 40% under complete combination of rainfall intensities of 0.7, 1.0, 1.5, 2.0 and 2.5 mm min<sup>-1</sup> and slope gradients of 7°, 10°, 15°, 20° and 25°. Results showed that sheet erosion rate (<em>SE</em>), varying from 0.0048 to 0.0578 kg m<sup>-2</sup> min<sup>-1</sup>, was well described by binary power function equation (<em>SE</em> = 0.0026 <em>I</em><sup>1.306</sup><em>S</em><sup>0.662</sup>) containing rainfall intensity and slope gradient with <em>R<sup>2</sup></em> = 0.940. The logarithmic equation of shear stress (<em>SE</em> = 0.084 + Ln (<em>τ</em>)) and the power function equation of stream power (<em>SE</em> = 1.141 <em>ɷ</em><sup>1.073</sup>) could be used to predict sheet erosion rate. Stream power (<em>R<sup>2</sup></em> = 0.903) was a better predictor of sheet erosion than shear stress (<em>R<sup>2</sup></em> = 0.882). However, predictions based on flow velocity, unit stream power, and unit energy were unsatisfactory. The stream power was an excellent hydrodynamic parameter for predicting sheet erosion rate. The sheet erosion process of grassland slope was also affected by the raindrop impact except the dynamic action of sheet flow. The combination of stream power and rainfall kinetic energy (<em>KE</em>) among different rainfall physical parameters had the most closely relationship with the sheet erosion rates, which is also better than the stream power only, and a binary power function equation (<em>SE</em> = 0.221 <em>ω</em><sup>0.831</sup><em>KE</em><sup>0.416</sup>) could be used to predict sheet erosion rate on grassland slope with <em>R<sup>2</sup></em> = 0.930. The study results revealed the dynamic mechanism of the sheet erosion process on steep grassland in the loess region of China.</p>

scholarly journals Investigating rainfall duration effects on transport of chemicals from soil to surface runoff on a loess slope under artificial rainfall conditions

2019 ◽  
Vol 14 (No. 4) ◽  
pp. 183-194
Author(s):  
Yali Zhang ◽  
Xiaoyang Li ◽  
Xingchang Zhang ◽  
Huaien Li
Keyword(s):  
Soil Erosion ◽  
Power Function ◽  
Surface Runoff ◽  
Concentration Curve ◽  
Desorption Kinetics ◽  
Concentration Change ◽  
Rainfall Duration ◽  
Loess Slope ◽  
Artificial Rainfall ◽  
Sheet Erosion

The release and transport of soil chemicals in water erosion conditions are important for the local environment, soil and water resources conservation. According to the artificial rainfall experiments with a constant rainfall intensity of 90 mm/h and different rainfall duration (30, 60, 90, 120 and 150 min), the traits of soil PO<sub>4</sub><sup>3–</sup>, K<sup>+</sup>, and Br<sup>–</sup> release and transport from soil to surface runoff on the loess slope were analysed, and a model describing the chemical concentration change in surface runoff under soil erosion conditions was developed. The runoff coefficient quickly increased in 15 min or so, and then it was stable in the range of 0.60–0.85. The sediment intensity decreased in 30 min and soon increased after severe sheet erosion occurred on the slope. The concentration curve of Br<sup>–</sup> in surface runoff can be divided into two stages, quickly decreasing in the initial 30 min after the surface runoff occurred, and then stable. The concentration curve of PO<sub>4</sub><sup>3–</sup> and K<sup>+</sup> in surface runoff can be divided into three stages, quickly decreasing like Br<sup>– </sup>was decreasing, then stable, and increasing after severe sheet erosion began. Compared with the exponential function, the power function was found more suitable for fitting the change in chemicals in runoff with unsaturated soil; while neither of them could well fit the PO<sub>4</sub><sup>3–</sup> and K<sup>+</sup> concentration change after severe erosion occurred. The transport of chemicals under complex soil erosion conditions seems to be a dynamic release process between surface runoff and sediment. Based on the convection-dispersion mechanism and desorption kinetics, the polynomial model under soil erosion conditions was created. For adsorbed PO<sub>4</sub><sup>3–</sup> and K<sup>+</sup>, it is more suitable to simulate that process than the power function, while it is not so good for mobile Br<sup>–</sup>.  

The Sediment Erosion Rate Flume (SERF): A New Testing Device for Measuring Soil Erosion Rate and Shear Stress

2012 ◽  
Vol 35 (4) ◽  
pp. 103814 ◽  
Author(s):  
Raphael W. Crowley ◽  
David B. Bloomquist ◽  
Falak D. Shah ◽  
Courtney M. Holst
Keyword(s):  
Shear Stress ◽  
Soil Erosion ◽  
Erosion Rate ◽  
Testing Device ◽  
Sediment Erosion ◽  
Soil Erosion Rate

scholarly journals Assessment of land use impact on hydraulic threshold conditions for gully head cut initiation

2016 ◽  
Vol 20 (7) ◽  
pp. 3005-3012 ◽  
Author(s):  
Aliakbar Nazari Samani ◽  
Qiuwen Chen ◽  
Shahram Khalighi ◽  
Robert James Wasson ◽  
Mohammad Reza Rahdari
Keyword(s):  
Land Use ◽  
Shear Stress ◽  
Soil Erosion ◽  
Critical Shear Stress ◽  
Gully Erosion ◽  
Threshold Condition ◽  
Stream Power ◽  
Threshold Phenomenon ◽  
Erosion Models ◽  
Dry Farming

Abstract. A gully as an accelerated erosion process is responsible for land degradation under various environmental conditions and has been known as a threshold phenomenon. Although the effects of gullying processes have been well documented, few soil erosion models have taken into account the threshold condition necessary for gully development. This research was devoted to determining the effects of land use change on hydraulic threshold condition and stream power of water flow through an in situ experimental flume (15 m  ×  0.4 m). Results indicated that head cut initiation and detachment rates showed a better correlation to stream power indices than shear stress (τcr). The threshold unit stream power value (ωu) for head cut initiation in rangeland, abandoned land, and dry farming land was 0.0276, 0.0149, and 4.5  ×  10−5 m s−1, respectively. Moreover, the micro-relief condition of soil surface and surface vegetation affected the flow regime of discharge and velocity. It is seen that the composite hydraulic criteria of Froude number (Fr) and discharge (Q) can clearly discriminate the land uses' threshold. In fact, the remarkable decrease of τcr in dry farming was related to the effect of tillage practice on soil susceptibility and aggregate strength. The findings indicated that using the unit steam power index instead of critical shear stress could increase the models' precision for prediction of head cut development. Compared to the Ephemeral Gully Erosion Model (EGEM) equation for critical shear stress, it is important to point out that for modelling of gully erosion, using single soil attributes can lead to an inaccurate estimation for τcr. In addition, based on the findings of this research, the use of threshold values of τcr  =  35 dyne cm−2 and ωu  =  0.4 cm s−1 in physically based soil erosion models is susceptible to high uncertainty when assessing gully erosion.

scholarly journals Spatiotemporal changes in flow hydraulic characteristics and soil loss during gully headcut erosion under controlled conditions

2021 ◽  
Vol 25 (8) ◽  
pp. 4473-4494
Author(s):  
Mingming Guo ◽  
Zhuoxin Chen ◽  
Wenlong Wang ◽  
Tianchao Wang ◽  
Qianhua Shi ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Shear Stress ◽  
Energy Consumption ◽  
Soil Erosion ◽  
Soil Loss ◽  
Gully Erosion ◽  
Stream Power ◽  
Spatiotemporal Changes ◽  
Headcut Erosion ◽  
Over Time

Abstract. The spatiotemporal changes in flow hydraulics and energy consumption and their associated soil erosion remain unclear during gully headcut retreat. A simulated scouring experiment was conducted on five headcut plots consisting of upstream area (UA), gully headwall (GH), and gully bed (GB) to elucidate the spatiotemporal changes in flow hydraulic, energy consumption, and soil loss during headcut erosion. The flow velocity at the brink of a headcut increased as a power function of time, whereas the jet velocity entry to the plunge pool and jet shear stress either logarithmically or linearly decreased over time. The jet properties were significantly affected by upstream flow discharge. The Reynolds number, runoff shear stress, and stream power of UA and GB increased as logarithmic or power functions of time, but the Froude number decreased logarithmically over time. The Reynolds number, shear stress, and stream power decreased by 56.0 %, 63.8 %, and 55.9 %, respectively, but the Froude number increased by 7.9 % when flow dropped from UA to GB. The accumulated energy consumption of UA, GH, and GB positions linearly increased with time. In total, 91.12 %–99.90 % of total flow energy was consumed during headcut erosion, of which the gully head accounted for 77.7 % of total energy dissipation, followed by UA (18.3 %), and GB (4.0 %). The soil loss rate of the “UA-GH-GB” system initially rose and then gradually declined and levelled off. The soil loss of UA and GH decreased logarithmically over time, whereas the GB was mainly characterized by sediment deposition. The proportion of soil loss at UA and GH is 11.5 % and 88.5 %, respectively, of which the proportion of deposited sediment on GB reached 3.8 %. The change in soil loss of UA, GH, and GB was significantly affected by flow hydraulic and jet properties. The critical energy consumption initiating soil erosion of UA, GH, and GB is 1.62, 5.79, and 1.64 J s−1, respectively. These results are helpful for deepening the understanding of gully erosion process and hydrodynamic mechanisms and can also provide a scientific basis for the construction of gully erosion model and the design of gully erosion prevention measures.

scholarly journals Spatial-temporal changes in flow hydraulic characteristics and soil loss during gully headcut erosion

2020 ◽  
Author(s):  
Mingming Guo ◽  
Zhuoxin Chen ◽  
Wenlong Wang ◽  
Tianchao Wang ◽  
Qianhua Shi ◽  
...  
Keyword(s):  
Shear Stress ◽  
Energy Consumption ◽  
Soil Erosion ◽  
Froude Number ◽  
Soil Loss ◽  
Reynold Number ◽  
Stream Power ◽  
Spatial Changes ◽  
Headcut Erosion ◽  
Over Time

Abstract. The temporal-spatial changes in flow hydraulics and energy consumption and their associated soil erosion remain unclear during gully headcut retreat. A simulated scouring experiment was conducted on five headcut plots consisting of upstream area (UA), gully headwall (GH) and gully bed (GB) to elucidate the temporal-spatial changes in flow hydraulic, energy consumption, and soil loss during headcut erosion. The flow velocity at the brink of headcut increased as a power function of time, whereas the jet velocity entry to plunge pool and jet shear stress logarithmically or linearly decreased over time. The jet properties significantly affected by upstream flow discharge. The Reynold number, runoff shear stress, and stream power of UA and GB increased as logarithmic or power functions of time, but the Froude number decreased logarithmically over time. The flow of UA and GB was supercritical and subcritical, respectively, and transformed to turbulent with inflow discharge increased. The Reynold number, shear stress and stream power decreased by 56.0 %, 63.8 % and 55.9 %, respectively, but the Froude number increased by 7.9 % when flow dropped from UA to GB. The accumulated runoff energy consumption of UA, GH and GB positions linearly increased with time, and their proportions of energy consumption are 18.3 %, 77.7 % and 4.0 %, respectively. The soil loss rate of the UA-GH-GB system initially rose and then gradually declined and levelled off. The soil loss of UA and GH decreased logarithmically over time, whereas the GB was mainly characterized by sediment deposition. The proportion of soil loss at UA and GH are 11.5 % and 88.5 %, respectively, of which the proportion of deposited sediment on GB reached 3.8 %. The change in soil loss of UA, GH and GB was significantly affected by flow hydraulic and jet properties. The critical energy consumption initiating soil erosion of UA, GH, and GB are 1.62 J s−1, 5.79 J s−1 and 1.64 J s−1, respectively. These results are helpful to reveal the mechanism of gully headcut erosion and built headcut migration model.

Soil erosion characteristics of three-dimensional overburdened stockpiles

2019 ◽  
Vol 44 (4) ◽  
pp. 534-549
Author(s):  
Han Luo ◽  
Jiaorong Lv ◽  
Yubo Rong ◽  
Yongsheng Xie ◽  
Jianqiao Han
Keyword(s):  
Soil Erosion ◽  
Construction Projects ◽  
Three Dimensional ◽  
Erosion Process ◽  
Stream Power ◽  
Erosion Processes ◽  
Runoff Rate ◽  
Specific Source ◽  
Dimensional Shape ◽  
Three Dimensional Shape

Overburdened stockpiles, a kind of typical loose mixture composed of different proportions of soil and gravel that are created by various production and construction projects, are one of the main sources of man-made accelerated erosion. Because of their specific source of production and unique three-dimensional shape, overburdened stockpiles often present a peculiar erosion process given rainfall conditions. To study this erosion process, a stockpile platform device was designed and used to simulate three-dimensional overburdened stockpiles. A series of indoor artificially simulated rainfall experiments at different precipitation intensities were conducted using loessial soil with different gravel contents. The following key results were obtained: (a) the runoff rate and flow velocity had the same trend over time – that is, a rapid increase, followed by a slower increase and stabilization, while the three-dimensional shape resulted in smaller numerical values of the Reynolds number and Froude number than a rectangular slope; (b) the sediment yield increased exponentially in response to the increasing rainfall intensity and decreased with increasing gravel content in a logarithmic manner; and (c) stream power could be the optimal factor describing soil erosion because it produced the strongest correlation and fitting degree for soil detachment rate. These findings improve our understanding of the hydraulic characteristics and erosion processes of overburdened stockpiles and also have implications for predictive soil and water loss models.

Quantifying sheet erosion rate on steep grassland in the loess region of China

2020 ◽  
pp. 1-12
Author(s):  
Qi Guo ◽  
Zhanli Wang ◽  
Qilin Zhang ◽  
Qingwei Zhang ◽  
Nan Shen ◽  
...  
Keyword(s):  
Erosion Rate ◽  
Loess Region ◽  
Sheet Erosion

scholarly journals A Quantitative Analysis of Factors Influencing Organic Matter Concentration in the Topsoil of Black Soil in Northeast China Based on Spatial Heterogeneous Patterns

2021 ◽  
Vol 10 (5) ◽  
pp. 348
Author(s):  
Zhenbo Du ◽  
Bingbo Gao ◽  
Cong Ou ◽  
Zhenrong Du ◽  
Jianyu Yang ◽  
...  
Keyword(s):  
Land Use ◽  
Organic Matter ◽  
Soil Erosion ◽  
Soil Type ◽  
Northeast China ◽  
Black Soil ◽  
Factors Affecting ◽  
Soil Zone ◽  
Rainfed Farming ◽  
Study Results

Black soil is fertile, abundant with organic matter (OM) and is exceptional for farming. The black soil zone in northeast China is the third-largest black soil zone globally and produces a quarter of China’s commodity grain. However, the soil organic matter (SOM) in this zone is declining, and the quality of cultivated land is falling off rapidly due to overexploitation and unsustainable management practices. To help develop an integrated protection strategy for black soil, this study aimed to identify the primary factors contributing to SOM degradation. The geographic detector, which can detect both linear and nonlinear relationships and the interactions based on spatial heterogeneous patterns, was used to quantitatively analyze the natural and anthropogenic factors affecting SOM concentration in northeast China. In descending order, the nine factors affecting SOM are temperature, gross domestic product (GDP), elevation, population, soil type, precipitation, soil erosion, land use, and geomorphology. The influence of all factors is significant, and the interaction of any two factors enhances their impact. The SOM concentration decreases with increased temperature, population, soil erosion, elevation and terrain undulation. SOM rises with increased precipitation, initially decreases with increasing GDP but then increases, and varies by soil type and land use. Conclusions about detailed impacts are presented in this paper. For example, wind erosion has a more significant effect than water erosion, and irrigated land has a lower SOM content than dry land. Based on the study results, protection measures, including conservation tillage, farmland shelterbelts, cross-slope ridges, terraces, and rainfed farming are recommended. The conversion of high-quality farmland to non-farm uses should be prohibited.

scholarly journals Soil Erosion Estimates in Arid Region: A Case Study of the Koutine Catchment, Southeastern Tunisia

2021 ◽  
Vol 11 (15) ◽  
pp. 6763
Author(s):  
Mongi Ben Zaied ◽  
Seifeddine Jomaa ◽  
Mohamed Ouessar
Keyword(s):  
Soil Erosion ◽  
Soil Loss ◽  
Scientific Evidence ◽  
Field Measurements ◽  
Spatiotemporal Variability ◽  
Soil Conditions ◽  
Storm Events ◽  
Erosion Processes ◽  
Study Results ◽  
Soil Losses

Soil erosion remains one of the principal environmental problems in arid regions. This study aims to assess and quantify the variability of soil erosion in the Koutine catchment using the RUSLE (Revised Universal Soil Loss Equation) model. The Koutine catchment is located in an arid area in southeastern Tunisia and is characterized by an annual mean precipitation of less than 200 mm. The model was used to examine the influence of topography, extreme rainstorm intensity and soil texture on soil loss. The data used for model validation were obtained from field measurements by monitoring deposited sediment in settlement basins of 25 cisterns (a traditional water harvesting and storage technique) over 4 years, from 2015 to 2018. Results showed that slope is the most controlling factor of soil loss. The average annual soil loss in monitoring sites varies between 0.01 and 12.5 t/ha/y. The storm events inducing the largest soil losses occurred in the upstream part of the Koutine catchment with a maximum value of 7.3 t/ha per event. Soil erosion is highly affected by initial and preceding soil conditions. The RUSLE model reasonably reproduced (R2 = 0.81) the spatiotemporal variability of measured soil losses in the study catchment during the observation period. This study revealed the importance of using the cisterns in the data-scarce dry areas as a substitute for the classic soil erosion monitoring fields. Besides, combining modeling of outputs and field measurements could improve our physical understanding of soil erosion processes and their controlling factors in an arid catchment. The study results are beneficial for decision-makers to evaluate the existing soil conservation and water management plans, which can be further adjusted using appropriate soil erosion mitigation options based on scientific evidence.

scholarly journals Impacts of oak deforestation and rainfed cultivation on soil redistribution processes across hillslopes using 137Cs techniques

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Shamsollah Ayoubi ◽  
Nafiseh Sadeghi ◽  
Farideh Abbaszadeh Afshar ◽  
Mohammad Reza Abdi ◽  
Mojtaba Zeraatpisheh ◽  
...  
Keyword(s):  
Land Use ◽  
Magnetic Susceptibility ◽  
Soil Erosion ◽  
Erosion Rate ◽  
Land Use Changes ◽  
Soil Samples ◽  
Natural Forest ◽  
Oak Forests ◽  
Erosion Rates ◽  
Rainfed Farming

Abstract Background As one of the main components of land-use change, deforestation is considered the greatest threat to global environmental diversity with possible irreversible environmental consequences. Specifically, one example could be the impacts of land-use changes from oak forests into agricultural ecosystems, which may have detrimental impacts on soil mobilization across hillslopes. However, to date, scarce studies are assessing these impacts at different slope positions and soil depths, shedding light on key geomorphological processes. Methods In this research, the Caesium-137 (137Cs) technique was applied to evaluate soil redistribution and soil erosion rates due to the effects of these above-mentioned land-use changes. To achieve this goal, we select a representative area in the Lordegan district, central Iran. 137Cs depth distribution profiles were established in four different hillslope positions after converting natural oak forests to rainfed farming. In each hillslope, soil samples from three depths (0–10, 10–20, and 20–50 cm) and in four different slope positions (summit, shoulder, backslope, and footslope) were taken in three transects of about 20 m away from each other. The activity of 137Cs was determined in all the soil samples (72 soil samples) by a gamma spectrometer. In addition, some physicochemical properties and the magnetic susceptibility (MS) of soil samples were measured. Results Erosion rates reached 51.1 t·ha− 1·yr− 1 in rainfed farming, whereas in the natural forest, the erosion rate was 9.3 t·ha− 1·yr− 1. Magnetic susceptibility was considerably lower in the cultivated land (χhf = 43.5 × 10− 8 m3·kg− 1) than in the natural forest (χhf = 55.1 × 10− 8 m3·kg− 1). The lower soil erosion rate in the natural forest land indicated significantly higher MS in all landform positions except at the summit one, compared to that in the rainfed farming land. The shoulder and summit positions were the most erodible hillslope positions in the natural forest and rainfed farming, respectively. Conclusions We concluded that land-use change and hillslope positions played a key role in eroding the surface soils in this area. Moreover, land management can influence soil erosion intensity and may both mitigate and amplify soil loss.

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