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

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>

Modelling sheet erosion on steep slopes in the loess region of China

2017 ◽  
Vol 553 ◽  
pp. 549-558 ◽  
Author(s):  
Bing Wu ◽  
Zhanli Wang ◽  
Qingwei Zhang ◽  
Nan Shen ◽  
June Liu
Keyword(s):  
Loess Region ◽  
Steep Slopes ◽  
Sheet Erosion

The experimental research on initiation mechanism of debris flow from glacial till

2020 ◽  
Author(s):  
Yongbo Tie ◽  
Jintao Jiang ◽  
Shuai Wang
Keyword(s):  
Debris Flow ◽  
Flow Velocity ◽  
Erosion Rate ◽  
Fine Particles ◽  
Critical Value ◽  
Glacial Till ◽  
Coarse Grained ◽  
Analogue Experiments ◽  
Debris Flow Initiation ◽  
Sheet Erosion

<p>The debris flow initiate by glacial till always dangers the local residents and facilities in alpine region in southwest China. The study of debris flow initiate from glacial till can help in understanding the mechanism of glacial till transfer to debris flow, in revealing the development of alpine mountainous topography. In this study, we designed analogue experiments that simulate the initiating process of glacial till eroded by the runoff. This research focuses on the relationship between the glacial till initiating and the critical value of flow velocity by performing analogue experiments with different flow velocity under a constant slope of landform.</p><p>A particle analysis of the modeled glacial till take from field allows understanding the structure of tested soil and standardizing the critical value of debris flow initiation. After the rush of flow with different velocity, the tested glacial till reaches a failure condition (i.e., the movement of certain particle, the undercutting of soil) which was assigned as the evidence for debris flow initiating. Results show that there are three types of erosion occurred during the experiment, the sheet erosion related to flood generation, the vertical erosion related to debris flow initiation, and lateral erosion related to the volume increasing of debris flow. Results show that the time duration of debris flow initiation are negative correlated with the velocity of flow. Because of the distribution of glacial till particle, the surface of the longitudinal profile showed corrugated form after the eroding of flow, this mainly depends on the infiltration zone where the water content of glacial till are saturated.</p><p>In the early period before the formation of debris flow, the main type of soil erosion was sheet erosion, the dual peak structure of glacial till made it easy to start up the soil with fine particles in the action of runoff scouring. Therefore, the sediment content in the flood could be improved, which provided a precondition for the formation of debris flow. In this process, the influence of runoff velocity was significant. According to the statistical results of the experiment, the faster the runoff velocity was, the faster the glacial till erosion rate was; and on the contrary, the slower the glacial till erosion rate was. We show that faster the flow velocity was, relatively shorter time the flood took to form, but relatively longer time the debris flow took to start. Finally, our results demonstrate the runoff scouring first leads to the removal of fine particles in glacial till, then the coarse grained soil was unstable due to the loss of foundation support and it initiated to form debris flows.</p>

Landscape development in response to climatic change during Oxygen Isotope Stage 5 in the southern Siberian loess region

Boreas ◽  
2004 ◽  
Vol 33 (2) ◽  
pp. 164-180 ◽  
Author(s):  
Jiri Chlachula ◽  
Rob Kemp ◽  
Catherine Jessen ◽  
Adrian Palmer ◽  
Phillip Toms
Keyword(s):  
Oxygen Isotope ◽  
Climatic Change ◽  
Landscape Development ◽  
Oxygen Isotope Stage ◽  
Loess Region

scholarly journals Effect of Nitrogen Ion Implantation on the Cavitation Erosion Resistance and Cobalt-Based Solid Solution Phase Transformations of HIPed Stellite 6

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2324
Author(s):  
Mirosław Szala ◽  
Dariusz Chocyk ◽  
Anna Skic ◽  
Mariusz Kamiński ◽  
Wojciech Macek ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Stainless Steel ◽  
Ion Implantation ◽  
Phase Transformations ◽  
Erosion Rate ◽  
Cavitation Erosion ◽  
Matrix Phase ◽  
Nitrogen Ion Implantation ◽  
Stellite 6 ◽  
Nitrogen Ion

From the wide range of engineering materials traditional Stellite 6 (cobalt alloy) exhibits excellent resistance to cavitation erosion (CE). Nonetheless, the influence of ion implantation of cobalt alloys on the CE behaviour has not been completely clarified by the literature. Thus, this work investigates the effect of nitrogen ion implantation (NII) of HIPed Stellite 6 on the improvement of resistance to CE. Finally, the cobalt-rich matrix phase transformations due to both NII and cavitation load were studied. The CE resistance of stellites ion-implanted by 120 keV N+ ions two fluences: 5 × 1016 cm−2 and 1 × 1017 cm−2 were comparatively analysed with the unimplanted stellite and AISI 304 stainless steel. CE tests were conducted according to ASTM G32 with stationary specimen method. Erosion rate curves and mean depth of erosion confirm that the nitrogen-implanted HIPed Stellite 6 two times exceeds the resistance to CE than unimplanted stellite, and has almost ten times higher CE reference than stainless steel. The X-ray diffraction (XRD) confirms that NII of HIPed Stellite 6 favours transformation of the ε(hcp) to γ(fcc) structure. Unimplanted stellite ε-rich matrix is less prone to plastic deformation than γ and consequently, increase of γ phase effectively holds carbides in cobalt matrix and prevents Cr7C3 debonding. This phenomenon elongates three times the CE incubation stage, slows erosion rate and mitigates the material loss. Metastable γ structure formed by ion implantation consumes the cavitation load for work-hardening and γ → ε martensitic transformation. In further CE stages, phases transform as for unimplanted alloy namely, the cavitation-inducted recovery process, removal of strain, dislocations resulting in increase of γ phase. The CE mechanism was investigated using a surface profilometer, atomic force microscopy, SEM-EDS and XRD. HIPed Stellite 6 wear behaviour relies on the plastic deformation of cobalt matrix, starting at Cr7C3/matrix interfaces. Once the Cr7C3 particles lose from the matrix restrain, they debond from matrix and are removed from the material. Carbides detachment creates cavitation pits which initiate cracks propagation through cobalt matrix, that leads to loss of matrix phase and as a result the CE proceeds with a detachment of massive chunk of materials.

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 Co-variation of silicate, carbonate and sulfide weathering drives CO2 release with erosion

2021 ◽  
Vol 14 (4) ◽  
pp. 211-216
Author(s):  
Aaron Bufe ◽  
Niels Hovius ◽  
Robert Emberson ◽  
Jeremy K. C. Rugenstein ◽  
Albert Galy ◽  
...  
Keyword(s):  
Erosion Rate ◽  
Global Climate ◽  
Stream Water ◽  
Sulfide Oxidation ◽  
Silicate Weathering ◽  
Emission Rates ◽  
Mountain Ranges ◽  
Weathering Rates ◽  
Southern Taiwan ◽  
Co2 Release

AbstractGlobal climate is thought to be modulated by the supply of minerals to Earth’s surface. Whereas silicate weathering removes carbon dioxide (CO2) from the atmosphere, weathering of accessory carbonate and sulfide minerals is a geologically relevant source of CO2. Although these weathering pathways commonly operate side by side, we lack quantitative constraints on their co-variation across erosion rate gradients. Here we use stream-water chemistry across an erosion rate gradient of three orders of magnitude in shales and sandstones of southern Taiwan, and find that sulfide and carbonate weathering rates rise with increasing erosion, while silicate weathering rates remain steady. As a result, on timescales shorter than marine sulfide compensation (approximately 106–107 years), weathering in rapidly eroding terrain leads to net CO2 emission rates that are at least twice as fast as CO2 sequestration rates in slow-eroding terrain. We propose that these weathering reactions are linked and that sulfuric acid generated from sulfide oxidation boosts carbonate solubility, whereas silicate weathering kinetics remain unaffected, possibly due to efficient buffering of the pH. We expect that these patterns are broadly applicable to many Cenozoic mountain ranges that expose marine metasediments.

scholarly journals Buoyancy-driven dissolution of inclined blocks: Erosion rate and pattern formation

2020 ◽  
Vol 5 (5) ◽  
Author(s):  
Caroline Cohen ◽  
Michael Berhanu ◽  
Julien Derr ◽  
Sylvain Courrech du Pont
Keyword(s):  
Pattern Formation ◽  
Erosion Rate

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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