The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
P I A Kinnell - One of the best experts on this subject based on the ideXlab platform.
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Technical note: Detachment and transport limiting systems operate simultaneously in Raindrop driven erosion
CATENA, 2021Co-Authors: P I A KinnellAbstract:Abstract Soil erosion involves two liked processes, detachment of particles held within the soil surface by cohesive forces and inter-particle friction, and the transport of the detached material away from the site of detachment. It is commonly thought that erosion is either detachment limited or transport limited but this is not true for surfaces where Raindrop driven sediment transport occurs. When detachment occurs by Raindrop Impact, transport away from the site of detachment can occur in the air and in rain-Impacted flow. Splash transports both fine and coarse particles aerially. In rain Impacted flows, fine material travels in completed suspension and at velocities that are at, or near the velocity of the flow. Coarse material may travel by Raindrop induced saltation and rolling, or if flow conditions are appropriate, by flow driven saltation and rolling. Transport by splash and by Raindrop induced saltation and rolling ceases when Raindrop Impact ceases even if previously detached material has not been discharged. Consequently, sediment transport limits erosion whenever Raindrop Impact is involved in transporting detached soil material over the soil surface. However, the amount of material available for transport is controlled by the ability of the Impacting Raindrops to cause detachment and the ability of the cohesive soil surface to resist detachment. Consequently, the discharged of coarse material by rain-Impacted flows is both detachment limited and transport limited at the same time. Raindrop driven erosion is a complex process and the spatial and temporal variations in the transport mechanisms need to be considered when experiments involving Raindrop driven erosion experiments are designed and the results analysed.
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Simulations demonstrating interaction between coarse and fine sediment loads in rain‐Impacted flow
Earth Surface Processes and Landforms, 2006Co-Authors: P I A KinnellAbstract:Rain-Impacted flows dominate sheet and interrill erosion and are important in eroding soil rich in nutrients and other chemicals which may have deleterious effects on water quality. Erosion in rain-Impacted flow is associated with Raindrop detachment followed by transport either by the combination of flow velocity and Raindrop Impact (Raindrop-induced flow transport, RIFT) or the inherent capacity of the flow to transport detached material. Coarse particles tend to be transported by RIFT, while fine particles tend to be transported without any assistance from Raindrop Impact. Because the transport process associated with coarse particles is not 100 per cent efficient, it generates a layer of loose particles on the soil surface and this layer protects the underlying soil from detachment. Simulations were performed by modelling the uplift and downstream movement of both fine and coarse particles detached from the soil surface by individual Raindrop Impacts starting with a surface where no loose material was present. The simulations produced a flush of fine material followed by a decline in the discharge of fine material as the amount of loose material built up on the bed. The decline in the discharge of fine material was accompanied by an increase in the discharge of coarse material. The relative amounts of coarse and fine material discharged in the flow varied with flow velocity and cohesion in the surface of the soil matrix. The results indicate that the discharge of various sized sediments is highly dependent on local soil, rain and flow conditions and that extrapolating the results from one situation to another may not be appropriate. Copyright © 2006 John Wiley & Sons, Ltd.
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Raindrop Impact induced erosion processes and prediction a review
Hydrological Processes, 2005Co-Authors: P I A KinnellAbstract:Raindrop-Impact-induced erosion is initiated when detachment of soil particles from the surface of the soil results from an expenditure of Raindrop energy. Once detachment by Raindrop Impact has taken place, particles are transported away from the site of the Impact by one or more of the following transport processes: drop splash, Raindrop-induced flow transport, or transport by flow without stimulation by drop Impact. These transport processes exhibit varying efficiencies. Particles that fall back to the surface as a result of gravity produce a layer of pre-detached particles that provides a degree of protection against the detachment of particles from the underlying soil. This, in turn, influences the erodibility of the eroding surface. Good understanding of rainfall erosion processes is necessary if the results of erosion experiments are to be properly interpreted. Current process-based erosion prediction models do not deal with the issue of temporal variations in erodibility during a rainfall event or variabilities in erodibility associated with spatial changes in dominance of the transport processes that follow detachment by drop Impact. Although more complex erosion models may deal with issues like this, their complexity and high data requirement may make them unsuitable for use as general prediction tools. Copyright © 2005 John Wiley & Sons, Ltd.
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SEDIMENT CONCENTRATIONS RESULTING FROM FLOW DEPTH/DROP SIZE INTERACTIONS IN SHALLOW OVERLAND FLOW
Transactions of the ASAE, 1993Co-Authors: P I A KinnellAbstract:Flow depth influences the erosive stress applied by Raindrop Impact to the surface under shallow flow. An analysis of data from laboratory experiments shows the sediment concentration associated with drops of a given size to decrease exponentially with flow depth within two regimes when the susceptibility of the surface to erosion remains constant. In the first regime, Raindrop size has a non-significant effect because the height of the water surface above the bed constrains the height to which particles are lifted in the flow. In the second regime, which occurs when flows are deeper than a critical depth that varies with the energy of the Impacting drops, drop size and velocity influence sediment concentration from the sediment transport perspective. These effects need to be considered in experiments designed to evaluate the susceptibility of soil to erosion when Raindrop Impact is a dominant force in the erosion process. They also need to be considered in models designed to predict Raindrop-driven erosion.
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Soil/slope gradient interactions in erosion by rain-Impacted flow
Transactions of the ASAE, 1993Co-Authors: P I A Kinnell, D. CummingsAbstract:Slope gradient is a factor influencing interrill erosion. Results of laboratory experiments using artificial rainfall with 20 soils with widely differing susceptibilities to interrill erosion were analyzed in terms of the effect of slope gradient on interrill erosion through a model that considers the effects of both Raindrop Impact and surface water flow on interrill erosion.
Fenli Zheng - One of the best experts on this subject based on the ideXlab platform.
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Interactive effects of Raindrop Impact and groundwater seepage on soil erosion
Journal of Hydrology, 2019Co-Authors: Gang Liu, Fenli Zheng, Lu Jia, Yafei Jia, Xunchang Zhang, Jiaqiong ZhangAbstract:Abstract Raindrop Impact (RI) and groundwater seepage (GWS) play important roles in slope erosion processes. However, reliable quantification of their interactive effects on erosion is still lacking. Therefore, a laboratory study was conducted to reveal the effects of RI and GWS on hillslope erosion. A soil box (5.0 m long, 0.5 m wide, and 0.5 m deep) was subjected to rainfall simulation experiments under free drainage (FD) and GWS conditions. The effect of RI was studied by dissipating Raindrop energy, i.e. without Raindrop Impact (WRI). The results indicated that compared with WRI, RI increased the runoff rate, soil loss and sediment concentration by about 3–14%, 74–696%, and 64–560%, respectively. With a higher runoff rate of 27–54%, GWS increased soil loss and sediment concentration about 70–588% and 27–411% compared with FD, respectively. A power function relation were found between soil losses and runoff rate. The increasing rate of soil loss increased with runoff followed the order: GWS + RI > FD + RI > GWS + WRI > FD + WRI. The erosion and sediment yield seemed to be detachment-limited. As a result of crust formation, RI, compared with WRI, marginally enhanced the average flow velocity and shear stress, and reduced the resistance coefficient. The effects of GWS on flow parameters were more pronounced than RI. The mean weight diameter of aggregates was reduced by about 13–69% because of breakdown by Raindrop Impact or slaking. The loss of
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the effects of Raindrop Impact and runoff detachment on hillslope soil erosion and soil aggregate loss in the mollisol region of northeast china
Soil & Tillage Research, 2016Co-Authors: Fenli Zheng, Feng BianAbstract:Soil aggregates profoundly influence soil fertility and soil erosion. A large number of studies have showed that soil aggregate loss was mainly affected by Raindrop Impact and runoff detachment during hillslope erosion process; however, few attempts have been made to investigate which one plays the dominant role in soil aggregate loss. Therefore, a laboratory study was conducted to quantify the effects of Raindrop Impact and runoff detachment on soil erosion and soil aggregate loss during hillslope erosion processes. A soil pan (8 m long, 1.5 m wide, and 0.6 m deep and with an adjustable slope gradient of 0–35°) was subjected to rainfall simulation experiments under two soil surface conditions: with and without Raindrop Impact through placing nylon net over soil pan. Two rainfall intensities (50 and 100 mm h−1) of representative erosive rainfall and two slope gradients (5 and 10°) in the Mollisol region of Northeast China were subjected to two soil surface conditions. The results showed that Raindrop Impact played the dominant role in hillslope soil erosion and soil aggregate loss. Soil loss caused by Raindrop Impact was 3.6–19.8 times higher than that caused by runoff detachment. The contributions of Raindrop Impact to hillslope soil erosion were 78.3% to 95.2%. As rainfall intensity and slope gradient increased, soil loss caused by Raindrop Impact and runoff detachment both increased. The loss of each size aggregate was greatly reduced by 46.6–99.4% after eliminating Raindrop Impact. Meanwhile, the contributions of Raindrop Impact to the >2, 1–2, 0.5–1, 0.25–0.5 and <0.25 mm soil aggregate loss were 79.1% to 89.7%. Eliminating Raindrop Impact reduced rainfall intensity effect and increased slope gradient Impact on aggregate loss.
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The effects of Raindrop Impact and runoff detachment on hillslope soil erosion and soil aggregate loss in the Mollisol region of Northeast China
Soil and Tillage Research, 2016Co-Authors: Fenli Zheng, Feng BianAbstract:Soil aggregates profoundly influence soil fertility and soil erosion. A large number of studies have showed that soil aggregate loss was mainly affected by Raindrop Impact and runoff detachment during hillslope erosion process; however, few attempts have been made to investigate which one plays the dominant role in soil aggregate loss. Therefore, a laboratory study was conducted to quantify the effects of Raindrop Impact and runoff detachment on soil erosion and soil aggregate loss during hillslope erosion processes. A soil pan (8 m long, 1.5 m wide, and 0.6 m deep and with an adjustable slope gradient of 0–35°) was subjected to rainfall simulation experiments under two soil surface conditions: with and without Raindrop Impact through placing nylon net over soil pan. Two rainfall intensities (50 and 100 mm h−1) of representative erosive rainfall and two slope gradients (5 and 10°) in the Mollisol region of Northeast China were subjected to two soil surface conditions. The results showed that Raindrop Impact played the dominant role in hillslope soil erosion and soil aggregate loss. Soil loss caused by Raindrop Impact was 3.6–19.8 times higher than that caused by runoff detachment. The contributions of Raindrop Impact to hillslope soil erosion were 78.3% to 95.2%. As rainfall intensity and slope gradient increased, soil loss caused by Raindrop Impact and runoff detachment both increased. The loss of each size aggregate was greatly reduced by 46.6–99.4% after eliminating Raindrop Impact. Meanwhile, the contributions of Raindrop Impact to the >2, 1–2, 0.5–1, 0.25–0.5 and
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The role of soil surface water regimes and Raindrop Impact on hillslope soil erosion and nutrient losses
Natural Hazards, 2013Co-Authors: Fenli Zheng, Mathias J M Romkens, Qingsen Yang, Leilei Wen, Bin WangAbstract:Few investigations have addressed the interaction between soil surface water regimes and Raindrop Impact on nutrient losses, especially under artesian seepage condition. A simulation study was conducted to examine the effects on nitrogen and phosphorus losses. Four soil surface water regimes were designed: free drainage, saturation with rainfall, artesian seepage without rainfall, and artesian seepage with rainfall. These water regimes were subjected to two surface treatments: with and without Raindrop Impact through placing nylon net over soil pan. The results showed saturation and seepage with rainfall conditions induced greater soil loss and nutrient losses than free drainage condition. Nutrient concentrations in runoff from artesian seepage without rainfall condition were 7.3–228.7 times those from free drainage condition. Nutrient losses by runoff from saturation and seepage with rainfall conditions increased by factors of 1.30–9.38 and 2.81–40.11 times, and the corresponding losses with eroded sediment by 1.37–7.67 and 1.75–9.0 times, respectively, relative to those from free drainage condition. Regardless of different soil surface water regimes, Raindrop Impact increased 20.90–94.0 % nutrient losses with eroded sediment by promoting soil loss, but it only significantly enhanced nutrient transport to runoff under free drainage condition.
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Investigating the Role of Raindrop Impact on Hydrodynamic Mechanism of Soil Erosion Under Simulated Rainfall Conditions
Soil Science, 2012Co-Authors: Fenli ZhengAbstract:AbstractFew studies have addressed the role of Raindrop Impact on hydrodynamic mechanism of soil erosion. In this study, rainfall simulation experiments were conducted to evaluate the role of Raindrop Impact on processes of runoff and sediment yield, flow-hydraulic characteristics, and dynamic mecha
Gang Liu - One of the best experts on this subject based on the ideXlab platform.
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Effects of Raindrop Impact on the resistance characteristics of sheet flow
Journal of Hydrology, 2021Co-Authors: Enshuai Shen, Gang Liu, Yafei Jia, Chenxi Dan, Mohamed A.m. Abd Elbasit, Chang Liu, Hongqiang ShiAbstract:Abstract Raindrops Impact (RDI) can disturb the flow structure of sheet runoff and thus change the flow resistance. In this study, multiple experimentally simulated rainfalls were applied on a flat and smooth flume with variable slopes. To identify the RDI effect, one half of the data was collected with the flume covered by a gauze screen near runoff surface. Comparisons of results indicated that RDI increased the flow resistance, reduced flow velocity and increased flow depth. Darcy-Weisbach resistance and Manning coefficient decreased in the slope range 2–12%, and kept almost constant in higher slope range. Corresponding approximately to 12% slope, Reynolds number, Re = 800 appears to be a critical value separating the laminar and turbulent flow regime under rainfall conditions. Empirical equations relating Darcy-Weisbach resistance coefficient and Manning coefficient to Reynolds number and rainfall intensity were obtained. In addition, empirical equations of the incremental resistance, due to RDI were established for laminar flows. This study revealed some aspects of RDI in the rainfall-runoff hydrologic processes.
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Interactive effects of Raindrop Impact and groundwater seepage on soil erosion
Journal of Hydrology, 2019Co-Authors: Gang Liu, Fenli Zheng, Lu Jia, Yafei Jia, Xunchang Zhang, Jiaqiong ZhangAbstract:Abstract Raindrop Impact (RI) and groundwater seepage (GWS) play important roles in slope erosion processes. However, reliable quantification of their interactive effects on erosion is still lacking. Therefore, a laboratory study was conducted to reveal the effects of RI and GWS on hillslope erosion. A soil box (5.0 m long, 0.5 m wide, and 0.5 m deep) was subjected to rainfall simulation experiments under free drainage (FD) and GWS conditions. The effect of RI was studied by dissipating Raindrop energy, i.e. without Raindrop Impact (WRI). The results indicated that compared with WRI, RI increased the runoff rate, soil loss and sediment concentration by about 3–14%, 74–696%, and 64–560%, respectively. With a higher runoff rate of 27–54%, GWS increased soil loss and sediment concentration about 70–588% and 27–411% compared with FD, respectively. A power function relation were found between soil losses and runoff rate. The increasing rate of soil loss increased with runoff followed the order: GWS + RI > FD + RI > GWS + WRI > FD + WRI. The erosion and sediment yield seemed to be detachment-limited. As a result of crust formation, RI, compared with WRI, marginally enhanced the average flow velocity and shear stress, and reduced the resistance coefficient. The effects of GWS on flow parameters were more pronounced than RI. The mean weight diameter of aggregates was reduced by about 13–69% because of breakdown by Raindrop Impact or slaking. The loss of
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Soil internal forces contribute more than Raindrop Impact force to rainfall splash erosion
Geoderma, 2018Co-Authors: Jingfang Liu, Gang Liu, Zhihua Yang, Xinmin Liu, Shiwei ZhaoAbstract:Abstract Soil internal forces, including electrostatic, hydration and van der Waals, play critical roles in aggregate stability, erosion, and other processes related to soil and water. However, the extent to which soil internal forces influence splash erosion during rainfall remains unclear. In the present study, we used cationic-saturated soil samples to quantitatively separate the effects of soil internal and Raindrop Impact forces (external) on splash erosion through simulated rainfall experiments. An electrolyte solution was employed as rainfall material to represent the combined effects of soil internal and external forces on splash erosion. Ethanol was used to simulate the sole effect of soil external force on splash erosion. The soil splash erosion rate increased with increasing rainfall kinetic energy in experiments with electrolyte solution and ethanol and was also greatly influenced by soil internal forces. Moreover, the soil splash erosion rate increased first (from 1 to 10−2 mol L−1) then leveled off (from 10−2 to 10−4 mol L−1) with decreasing electrolyte concentration in the bulk solution. This finding was in agreement with the theoretical analysis of soil internal forces. The contribution rate of soil internal forces on splash erosion was >65% at a low electrolyte concentration ( 50%. Hence, soil internal forces exerted higher contribution to rainfall splash erosion than Raindrop Impact force under most field conditions. This work provides new understanding of the mechanism of soil splash erosion and establishes the possibility of controlling splash erosion by jointly regulating the soil internal and external forces.
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Soil internal forces initiate aggregate breakdown and splash erosion
ELSEVIER SCIENCE BV, 2018Co-Authors: Jingfang Liu, Gang Liu, Shiwei Zhao, Zilong Wang, Zhao, Sw Author), Northwest A&f Univ, Inst Soil Water Conservat, State Key Lab Soil Eros Dryland Far China.Abstract:Soil erosion is a severe ecological and environmental problem and the main cause of land degradation in many places worldwide. Soil aggregate breakdown is the first key step of splash erosion and is strongly influenced by soil internal forces, including electrostatic, hydration, and van der Waals forces. However, little is known about the influence of soil internal forces on splash erosion. In this study, we demonstrated that both splash erosion rate (SER) and soil aggregate breaking strength (ABS) were significantly affected by soil internal forces. SER and ABS increased first (from 1 to 10(-2) mol L-1) then became stable (from 10(-2) to 10(-4) mol L-1) with decreasing electrolyte concentration in bulk solution. The electrolyte concentration of 10(-2) Mol L-1 in bulk solution was the critical point for both soils in splash erosion and soil aggregate stability. The experimental results can be well interpreted by the theoretical analysis of soil internal forces. The surface potential and electric field around soil particles increased with decreasing electrolyte concentration, thereby increasing the electrostatic repulsive force among soil particles. This phenomenon led to soil aggregate breakdown and release of fine soil particles. Soil splash erosion rate and aggregate stability showed a linear relationship (R-2 = 0.83). Our results suggest that soil internal forces induce soil aggregate breakdown and then release of fine soil particles when the soil was wetted, supplying the original material for splash erosion. Furthermore, the Raindrop Impact force is the driving mechanism causing soil particle movement. In summary, splash erosion could be due to the coupling effects of soil internal forces and the Raindrop Impact force. Our study provides a possible internal controlling method for reducing splash erosion by adjusting soil internal forces between soil particles
Artemi Cerdà - One of the best experts on this subject based on the ideXlab platform.
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Particle size distribution of sediment detached from rills under Raindrop Impact in semi-arid soils
Journal of Hydrology, 2020Co-Authors: Ali Reza Vaezi, Nasrin Sadeghian, Artemi CerdàAbstract:Abstract Limited information is available on the role of Raindrop Impact (RI) in the particle size distribution of sediment (PSDs) and the homogeneous of sediment particles eroded in rills under slope gradients particularly in semi-arid soils. Toward this, a laboratory experiment was designed with three dominant semi-arid soils consist of loamy sand, clay and sandy clay, at four slope gradients (5, 10, 15, and 20%) under two soil surface conditions (SSC) i.e, with Raindrop Impact (RI) and without RI using a rainfall simulator with 90 mm h−1 in intensity for 30 min. Forty eight rainfall events were setted up to soil samples packed into the flumes with 0.4 m width by 4 m length. Runoff and sediment ratio for the two SSC was computed using the ratio of values with RI to their values without RI in each time interval from starting runoff. Based on the results, the soils appeared different behavior in runoff and sediment ratio during runoff generation time. In clay and sandy clay, contribution of RI in runoff and sediment increased during runoff generation in the rills which was associated to higher percentage of water-stable aggregates. The two soils produced higher runoff and sediment under RI with increasing slope gradient. The sediment selectivity by concentrated flow was determined using the comparison between PSDs in steady-state runoff and the PSD of original soil (PSDo). The PSDs curves of loamy sand were similar for the two SSC at slope gradients and overlapped almost with the PSDo, indicating lower importance of RI in the sediment transport selectivity in the soil with lower water-stable aggregates. Enrichment ratio of particles in sediment (ERs) varied with both soil texture and slope gradient. The contribution of RI in variation of ERs was more obvious in sand, indicating lower selectivity of sand to detachment by concentrated flow. The geometric mean diameter (dg) and standard deviation (δg) of the sediment particles were defined as a measure to determination of the homogeneity of sediment. Values of these indices increased under RI, indicating the contribution of RI in the transportability of all soil particles especially coarse particles. This study revealed that the RI is the major factor controlling runoff, sediment, the selectivity of soil particle by concentrated flow and sediment homogeneity in semi-arid soils. These variables can be quantified by PSDs, ERs, dg and δg for the two soil surface conditions and compared with the original soil.
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Contribution of Raindrop Impact to the change of soil physical properties and water erosion under semi-arid rainfalls
The Science of the total environment, 2017Co-Authors: Ali Reza Vaezi, Morvarid Ahmadi, Artemi CerdàAbstract:Soil erosion by water is a three-phase process that consists of detachment of soil particles from the soil mass, transportation of detached particles either by Raindrop Impact or surface water flow, and sedimentation. Detachment by Raindrops is a key component of the soil erosion process. However, little information is available on the role of Raindrop Impact on soil losses in the semi-arid regions where vegetation cover is often poor and does not protect the soil from rainfall. The objective of this study is to determine the contribution of Raindrop Impact to changes in soil physical properties and soil losses in a semiarid weakly-aggregated agricultural soil. Soil losses were measured under simulated rainfalls of 10, 20, 30, 40, 50, 60 and 70mmh-1, and under two conditions: i) with Raindrop Impact; and, ii) without Raindrop Impact. Three replications at each rainfall intensity and condition resulted in a total of 42 microplots of 1m×1.4m installed on a 10% slope according to a randomized complete block design. The contribution of Raindrop Impact to soil loss was computed using the difference between soil loss with Raindrop Impact and without Raindrop Impact at each rainfall intensity. Soil physical properties (aggregate size, bulk density and infiltration rate) were strongly damaged by Raindrop Impact as rainfall intensity increased. Soil loss was significantly affected by rainfall intensity under both soil surface conditions. The contribution of Raindrop Impact to soil loss decreased steadily with increasing rainfall intensity. At the lower rainfall intensities (20-30mmh-1), Raindrop Impact was the dominant factor controlling soil loss from the plots (68%) while at the higher rainfall intensities (40-70mmh-1) soil loss was mostly affected by increasing runoff discharge. At higher rainfall intensities the sheet flow protected the soil from Raindrop Impact.
Carine Lucas - One of the best experts on this subject based on the ideXlab platform.
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Pressure and shear stress caused by Raindrop Impact at the soil surface: Scaling laws depending on the water depth
Earth Surface Processes and Landforms, 2016Co-Authors: Amina Nouhou Bako, Frédéric Darboux, Francois James, Christophe Josserand, Carine LucasAbstract:Raindrop Impact is an important process in soil erosion. Through its pressure and shear stress, Raindrop Impact causes a significant detachment of the soil material, making this material available for transport by sheet flow. Thanks to the accurate Navier-Stokes equations solver Gerris, we simulate the Impact of a single Raindrop of diameter D, at terminal velocity, on water layers of different thickness h: D 10 , D 5 , D 3 , D 2 , D, 2D, in order to study pressures and shear stresses involved in Raindrop erosion. These complex numerical simulations help to understand precisely the dynamics of the Raindrop Impact, quantifying in particular the pressure and the shear stress fields. A detailed analysis of these fields is performed and self-similar structures are identified for the pressure and the shear stress on the soil surface. The evolution of these self-similar structures are investigated as the aspect ratio h/D varies. We find that the pressure and the shear stress have a specific dependence on the ratio between the drop diameter and the water layer thickness and that the scaling laws recently proposed in fluid mechanics are also applicable to Raindrops, paving the road to obtain effective models of soil erosion by Raindrops. In particular , we obtain a scaling law formula for the dependance of the maximum shear stress on the soil on the water depth, quantity that is crucial for quantifying erosion materials.
