Influence of Heavy Fuel Oil on the Thermo-Physical and Erodibility Properties of Earthen Materials

This study focuses on the use of heavy fuel oil in construction material in Burkina Faso. Its mixture with silty or clayey soil is used as a coating to reinforce the walls of raw earth constructions which are very sensitive to water. The interest of this study is to determine erodibility, water content, while highlighting the influence of the porosity accessible by water on thermal diffusion in construction material containing heavy fuel oil. The heavy fuel oil was mixed with a silty-clayey soil, in different proportions, and water to make bricks samples on which tests were carried out. At the end of the experimental tests, it appears that the water content increases gradually, but not significantly with the addition of heavy fuel oil, which causes a slight increase in the speed of heat propagation through the material with reduced porosity, particularly those containing higher quantities of heavy fuel oil. Conversely, we note a good performance of heavy fuel oil in terms of water resistance properties such as porosity accessible by water and erodibility. This allows us to conclude that the mixture of heavy fuel oil and silty-clayey soil used as a coating material could greatly reduce water infiltration into the walls of housing constructions with raw earthen materials.

A review of soil erodibility in water and wind erosion research

Soil erodibility is an important index to evaluate the soil sensitivity to erosion. The research on soil erodibility is a crucial tache in understanding the mechanism of soil erosion. Soil erodibility can be evaluated by measuring soil physiochemical properties, scouring experiment, simulated rainfall experiment, plot experiment and wind tunnel experiment. We can use soil erosion model and nomogram to calculate soil erodibility. Many soil erodibility indices and formulae have been put forward. Soil erodibility is a complex concept, it is influenced by many factors, such as soil properties and human activities. Several obstacles restrict the research of soil erodibility. Firstly, the research on soil erodibility is mainly focused on farmland; Secondly, soil erodibility in different areas cannot be compared sufficiently; and thirdly, the research on soil erodibility in water-wind erosion is very scarce. In the prospective research, we should improve method to measure and calculate soil erodibility, strengthen the research on the mechanism of soil erodibility, and conduct research on soil erodibility by both water and wind agents.

Assessment of soil erodibility and aggregate stability for different parts of a forest road

We measured erodibility and mean weight diameter （MWD） of soil aggregates in different parts of a forest road. Samples of topsoil were collected from cutslope, fillslope, road surface and forest ground to assess the texture, bulk density, moisture, CaCO3 and organic matter. Soil aggregate stability was determined by wet sieving. Soil erodibility on the road surface was 2.3 and 1.3 times higher than on the fillslope and cutslope, respectively. The forest soil had the lowest erodibility. Aggregate stability of cutslope and road surface were low and very low, respectively. There was a significant negative relationship between cutslope erodibility with CaCO3 and sand content. Cutslope erodibility increased with increasing silt, clay and moisture content. On fillslopes, MWD increased with in-creasing rock fragment cover, plant cover, litter cover, organic matter and sand. There was a strong negative correlation between fillslope erodibility and organic matter, sand and MWD. There was no significant difference between erodibility of bare soil and soils beneathRubus hyrcanusL. and Philonotis marchica （Hedw.） Brid.

Effects of land uses on soil physic-chemical properties and erodibility in collapsing-gully alluvial fan of Anxi County,China

the National Key Technologies R＆D Program of China during the 12th Five-Year Plan period （2011BAD31B00）

Evaluation of soil erodibility factor(k)for loess derived landforms of Kechik watershed in Golestan Province,North of Iran

The technique proposed by Wischmeier & Smith for estimating the soil erodibility factor is among the most important methods in this regard.Given the high amounts of silt and lime content in loess soils of eastern parts of Golestan province in Iran,this study aims to evaluate the ability of Wischmeier & Smith index to estimate the soil erodibility of this region.Soil erodibility was first obtained by Wischmeier nomograph and then was compared with the actual values obtained by selecting six plots and then performing physical and chemical tests on these samples.Using the nomograph,Wischmeier index was calculated to be about.0.5-0.092 Mg h MJ-1 mm-1.The results showed that Wischmeier index was 182,4.11,6 and 0.35 times than actual value in field with half-hour rainfall,Fournier index,SWAT value with half-hour rainfall and SWAT value with Fournier index,respectively.Obtained results showed that erodibility estimated by Wischmeier & Smith index was higher than the actual measured value.Poor performance of this index in loess soils indicates the need for further research in this field.

Determining relative block structure rating for rock erodibility evaluation in the case of non-orthogonal joint sets

The most commonly used method for assessing the hydraulic erodibility of rock is Annandale's method.This method is based on a correlation between the erosive force of flowing water and the capacity of rock resistance. This capacity is evaluated using Kirsten's index, which was initially developed to evaluate the excavatability of earth materials. For rocky material, this index is determined according to certain geomechanical factors related to intact rock and rock mass, such as compressive strength of intact rock, rock block size, discontinuity shear strength and relative block structure. To quantify the relative block structure, Kirsten(1982) developed a mathematical expression that accounts for the shape and orientation of the blocks relative to the direction of flow. Kirsten's initial concept for assessing the relative block structure considers that the geological formation is mainly fractured by two joint sets forming an orthogonally fractured system. An adjusted concept is proposed to determine the relative block structure when the fractured system is non-orthogonal where the angle between the planes of the two joint sets is greater or less than 90°. An analysis of the proposed relative block structure rating shows that considering a non-orthogonally fractured system has a significant effect on Kirsten's index and, as a consequence, on the assessment of the hydraulic erodibility of rock.

Wind erodibility indices of aeolian sandy soils impacted by different vegetation restoration:a case study from the Shannan valley of the Yarlung Zangbo River

Controlling aeolian desertification is a key ecological target on the Tibetan Plateau,especially within the widespread river valleys.Vegetation recovery can change the near-soil surface characteristics,which thus may influence wind erodibility of soils.However,these potential effects are not sufficiently evaluated for aeolian sandy soils.This study selected the Shannan valley of the Yarlung Zangbo River on the southern Tibetan Plateau as a case to investigate the variations in wind erodibility of aeolian sandy soils impacted by different vegetation restoration,since many ecological measures have been implemented in recent decades in the river valley.Eight vegetated sandy lands with different restoration types and ages and two bare sandy lands(as controls)were chosen as test sites.Four vegetated sandy lands were covered by Artemisia wellbyi,Hedysarum scoparium,Sophora moorcroftiana,and Populus L.with the similar restoration age of 10 years.For Sophora moorcroftiana and Populus L.communities,two restoration ages of 6 and over 30 years were also selected respectively.Wind erodibility was reflected by wind erodible fraction(EF),mean weight diameter of dry aggregates(MWD),capillary water capacity(CWC),soil cohesion(CS),and soil penetration resistance(PR)from different aspects.A comprehensive wind erodibility index(CWEI)was further produced by a weighted summation method to combine those five indices together and comprehensively quantify the effects of vegetation restoration on wind erodibility of aeolian sandy soils.The results showed that revegetation was efficient to reduce wind erodibility of aeolian sandy soils.EF generally decreased,while MWD,CWC,CS,and PR increased after vegetation restoration on the aeolian sandy lands.The CWEI of vegetated sandy lands varied greatly from 0.850 to 0 under different restoration types and ages and decreased by 14.4%to 100%compared to the control.Under the four different restoration types,Populus L.had the relatively minimum CWEI,followed by Artemisia wellbyi,Sophora moorcroftiana and Hedysarum scoparium.With succession from 6 to over 30 years,CWEI gradually declined for both the Populus L.and Sophora moorcroftiana restored sandy lands.The decreases in wind erodibility(reflected by CWEI)on vegetated sandy lands were dominantly controlled by the improvement of soil texture and the increases of organic matter and calcium carbonate contents with vegetation restoration.The combined vegetation measure of Populus L.mixed with shrubs and grasses was suggested as the optimal restoration type for mitigating wind erodibility of aeolian sandy soils in the Shannan valley of the Yarlung Zangbo River.

A method to determine relevant geomechanical parameters for evaluating the hydraulic erodibility of rock

Among the methods used for evaluating the potential hydraulic erodibility of rock,the most common methods are those based on the correlation between the force of flowing water and the capacity of a rock to resist erosion,such as Annandale’s and Pells’methods.The capacity of a rock to resist erosion is evaluated based on erodibility indices that are determined from specific geomechanical parameters of a rock mass.These indices include unconfined compressive strength(UCS)of rock,rock block size,joint shear strength,a block’s shape and orientation relative to the direction of flow,joint openings,and the nature of the surface to be potentially eroded.However,it is difficult to determine the relevant geomechanical parameters for evaluating the hydraulic erodibility of rock.The assessment of eroded unlined spillways of dams has shown that the capacity of a rock to resist erosion is not accurately evaluated.Using more than 100 case studies,we develop a method to determine the relevant geomechanical parameters for evaluating the hydraulic erodibility of rock in unlined spillways.The UCS of rock is found not to be a relevant parameter for evaluating the hydraulic erodibility of rock.On the other hand,we find that the use of three-dimensional(3D)block volume measurements,instead of the block size factor used in Annandale’s method,improves the rock block size estimation.Furthermore,the parameter representing the effect of a rock block’s shape and orientation relative to the direction of flow,as considered in Pells’method,is more accurate than the parameter adopted by Annandale’s method.

Soil Erodibility of Slope Farmland in Guizhou Mountain Areas

This paper studied soil erodibility of slope farmland in Guizhou mountain areas by the plot runoff method,analysis and test. Results show that the variation coefficient of erodibility K value calculated according to formula introduced by Sharply is low and relatively stable and accurate,so it is a suitable method for calculating erodibility K value of slope farmland in Guizhou mountain areas. K value of layer A slope farmland decreases with increase of years. The erodibility of entire soil layer is high,and the erosion resistance is weak. From the influence of different planting system and use types in 4 years,K values of different soil layers decrease,average reduction of A,B and C layers reaches 3. 17%- 11. 64%( 1. 26%- 12. 34% for layer A,1. 29%- 13. 80% for layer B,and 1. 26%- 10. 80% for layer C). Except engineering terraced treatment,the decline of K value of grassland,zoning crop rotation,economic fruit forest,grain and grass intercropping,plant hedge, and mixed forest treatment is higher than farmers' treatment,and the decline level is grassland > zoning crop rotation > economic fruit forest > grain and grass intercropping > plant hedge > and mixed forest treatment. Planting grass and trees is favorable for lowering erodibility of slope farmland and improving farmland quality. Interplanting of corns with other plants can increase plant coverage and species,so it is favorable for improving erodibility of slope farmland.

Establishment and Application of Soil Erodibility Index Based on Energy

By a simulated rainfall and runoff scouring test with typical corrosive soils in main water erosion regions of China, the erosion processes of soil were analyzed from the energy point of view, and a new soil erodibility indicator was proposed. The results show that there is a good relation- ship between the rate of sediment yield and energy consumption of slope runoff, and the erodibility coefficients of four soils are stable, being shown as follows 〉 loess 〉 black soil 〉 purple soil 〉 red soil.

Variation of Soils Erodibility in Mbe Agropastoral Area in Relation with Land Utilization, Central Cameroon

The study of the soils from Mbé and Wack is carried out in the framework of the knowledge of soils from the Adamawa Region of Cameroon and their erodibility was investigated using erodibility indices obtained through physico-chemical data. Eleven topsoils (0 - 20 cm) samples were collected on different land use and their susceptibility to erosion was assessed. The water dispersible clay (34.92 - 121.75 g•kg−1), the clay dispersion ratio (0.45 - 0.84) and the dispersion ratio (0.75 - 0.89) were high in the studied soils while the clay aggregation (13.16 - 42.27g•kg−1) and the clay flocculation index (0.16 - 0.55) were low to moderate indicating their high erodibility. The soils under natural vegetation, more clayey, displayed the highest amount of water dispersible clay while cropped soils recorded the smaller ones. Globally, in cropped soils, those under cereals displayed the highest clay dispersion indices than those under tubers. This suggests that tubers cropping practices in studied soils enhance their erodibility. Statistical analyses revealed that amorphous Al and Fe are elements which limit soils erodibility while K+ and promote soils particles dispersion. Sustainable management of these soils will consist on limiting runoff through agricultural practices such as direct seedling and orienting tillage perpendicularly to slope gradient.

Effect of Land Uses on Soil Erodibility in the Njala Area of Southern Sierra Leone

Soil loss through erosion continues to pose serious challenges to increasing the smallholder agricultural productivity in Sierra Leone. While emphasis on sustainable land use practices continue to gain attention among land users, however, the rate of adoption among smallholder farmers is still very low and hence, in most part of the country soil fertility has been declining at alarming rates. In the Njala area, studies have shown that soil loss ranges from moderate to high. Though soil erosion has been identified as a major soil fertility declining factor, however, the effect of land use practices on the inherent resistance of soil materials to erosion is lacking. This study was therefore conducted to assess the effect of land uses on soil erodibility. The results showed that the soils are coarse sandy loam with high sand content. The dispersion ratios and erosion indices of soils under cassava, plantain, maize and guava were above the minimum thresholds of 15.0 and 10.0 respectively, thus indicating that these soils are highly erodible compared to soils under fallow and sweet potato which have dispersion ratios and erosion indices below the minimum thresholds. Clay content was inversely proportional to and significantly correlated with dispersion ratio and erosion index while the correlations between silt + clay, dispersion ration and erosion index, and silt, silt + clay and dispersion ratio were negative and non-significant. Considering the coarse nature of soils, landscape features and high erodibility indices, these soils would need special soil and water conservation practices to counter further degradation. These may include following, agroforestry, silvi-pasture, controlled and rotational grazing. In addition, awareness of sense of self-responsibility and forest policies and regulations are needed.

Effect of Sustainable Land Management Practices on the Soil Erodibility at the Plateau of Abomey (Centre of Benin)

The soils of Benin in general and those of the department of Zou, in particular, are highly degraded. This study aimed to evaluate the effectiveness of sustainable land management practices on soil erodibility in two villages in the Plateau of Abomey. Soil samples were collected on plots under Sustainable Land Management (SLM) measures (direct seeding, maize residue management and soybean-cereal rotation) and on their adjacent control. The soil samples were prepared and analyzed in laboratory to determine variables such as soil permeability, organic matter content, and particle size. Soil erodibility was determined as proposed by Wischmeier & Smith. The effect of SLM practices was significant (0.02) on soil permeability. On plots under SLM measurements, soil permeability is higher with an average of 93.97 mm/h at Folly and 82.43 mm/h at Hanagbo. SLM measurements significantly (0.04) added organic matter to the soil. The average organic matter of the plots under SLM measures in Folly varies from 0.73% to 1.39% while it varies from 0.49% to 0.73% in the control plots. In Hanagbo, the average organic matter of the plots under SLM measures varies from 1.86% to 2.48% against 1.41% to 1.66% for the control plots. Regarding soil erodibility, it was found that the influence of SLM measures is significant in both villages. In villages, direct seeding and maize residue management significantly (0.008) reduced soil erodibility compared to their adjacent controls, while the soybean-cereal rotation measure increased soil erodibility compared to plot witnesses. The average soil erodibility of plots under SLM measures varies by 0.21 t⋅h/Mj⋅mm at 0.38 t⋅h/Mj⋅mm in the village of Hanagbo and 0.25 t⋅h/Mj⋅mm at 0.38 t⋅h/Mj⋅mm in the village of Folly. It varies from 0.24 t⋅h/Mj⋅mm at 0.28 t⋅h/Mj⋅mm for the control plots at Hanagbo and 0.31 t⋅h/Mj⋅mm at 0.37 t⋅h/Mj⋅mm in Folly. These practices can therefore be used for the sustainable use of agricultural land.

Influence of inflow discharge and bed erodibility on outburst flood of landslide dam

Accurate prediction of the hydrographs of outburst floods induced by landslide dam overtopping failure is necessary for hazard prevention and mitigation. In this study, flume model tests on the breaching of landslide dams were conducted. Unconsolidated soil materials with wide grain size distributions were used to construct the dam. The effects of different upstream inflow discharges and downstream bed soil erosion on the outburst peak discharge were investigated. Experimental results reveal that the whole hydrodynamic process of landslide dam breaching can be divided into three stages as defined by clear inflection points and peak discharges. The larger the inflow discharge, the shorter the time it takes to reach the peak discharge, and the larger the outburst flood peak discharge. The scale of the outburst floods was found to be amplified by the presence of an erodible bed located downstream of the landslide dam. This amplification decreases with the increase of upstream inflow. In addition, the results show that the existence of an erodible bed increases the density of the outburst flow, increasing its probability of transforming from a sediment flow to a debris flow.

Evaluation of soil loss severity and ecological restoration approach for sustainable agriculture in the Hindu Kush, Karakoram and Himalaya region

Soil erosion has resulted in removal of the topsoils containing fine soil particles and plant nutrients, causing decrease in soil fertility in the Hindu Kush, Karakoram and Himalaya(HKH) region. The existing production of cereal crop grains has been reduced to one third of the potential crop grains production owing to land degradation and poor farming practices. It is necessary to assess risk of soil loss and identify appropriate controlling measures to address issues of low agriculture productivity and water insecurity in the region. In the present study, severity of soil loss was predicted using Revised Universal Loss Equation(RUSLE) and ecological measures were identified for sustainable mountain agriculture in the HKH region of Upper Indus Basin, Pakistan. Overall 62.6% area was found to have very low risk of soil loss, i.e., <5 t/(ha·yr), 15.8% area low risk, i.e., 5-25 t/(ha·yr) and 7.5% area moderate risk, i.e., 25-50 t/(ha·yr) in the region. The risk was high, i.e., 50-100 t/(ha·yr) and very high, i.e., >100 t/(ha·yr) in about 6.8% and 7.4% areas respectively. The mean rate of soil loss was about 41.9 t/(ha·yr) in the Hindu Kush, 31.1 t/(ha·yr) in the Himalayas, 18.8 t/(ha·yr) in the Karakoram and overall 29.7 t/(ha·yr) in the three HKH ranges. As such no considerable measures have been adopted by the communities for restoration of the degraded areas except raising fruit/farm trees and supporting limited social forestry for their livelihoods. The slopes cleared for cultivation and susceptible to erosion may be stabilized through sowing/planting of multi-purpose plant species and formation of proper bench terraces. The conservation of forest ecosystem and pastures at higher elevations would help in reducing overland water flow, risk of flash flood hazard and minimizing sediment loads in the downstream. It is essential to adopt site-specific resource conservation techniques and restore possible ecosystem health for sustainable agriculture and economic development in the region in future.

Assessment of soil erosion in the Irga watershed on the eastern edge of the Chota Nagpur Plateau,India

Human activities to improve the quality of life have accelerated the natural rate of soil erosion.In turn,these natural disasters have taken a great impact on humans.Human activities,particularly the conversion of vegetated land into agricultural land and built-up area,stand out as primary contributors to soil erosion.The present study investigated the risk of soil erosion in the Irga watershed located on the eastern fringe of the Chota Nagpur Plateau in Jharkhand,India,which is dominated by sandy loam and sandy clay loam soil with low soil organic carbon(SOC)content.The study used the Revised Universal Soil Loss Equation(RUSLE)and Geographical Information System(GIS)technique to determine the rate of soil erosion.The five parameters(rainfall-runoff erosivity(R)factor,soil erodibility(K)factor,slope length and steepness(LS)factor,cover-management(C)factor,and support practice(P)factor)of the RUSLE were applied to present a more accurate distribution characteristic of soil erosion in the Irga watershed.The result shows that the R factor is positively correlated with rainfall and follows the same distribution pattern as the rainfall.The K factor values in the northern part of the study area are relatively low,while they are relatively high in the southern part.The mean value of the LS factor is 2.74,which is low due to the flat terrain of the Irga watershed.There is a negative linear correlation between Normalized Difference Vegetation Index(NDVI)and the C factor,and the high values of the C factor are observed in places with low NDVI.The mean value of the P factor is 0.210,with a range from 0.000 to 1.000.After calculating all parameters,we obtained the average soil erosion rate of 1.43 t/(hm^(2)•a),with the highest rate reaching as high as 32.71 t/(hm^(2)•a).Therefore,the study area faces a low risk of soil erosion.However,preventative measures are essential to avoid future damage to productive and constructive activities caused by soil erosion.This study also identifies the spatial distribution of soil erosion rate,which will help policy-makers to implement targeted soil erosion control measures.

Predicting the spatial distribution of soil erodibility factor using USLE nomograph in an agricultural watershed,Ethiopia

Soil erosion in the northwestern Amhara region,Ethiopia has been a subject of anxiety,resulting in a major environmental threat to the sustainability and productive capacity of agricultural areas.This study tried to estimate soil erodibility factor(Kfactor)using Universal Soil Loss Equation(USLE)nomograph,and evaluate the spatial distribution of the predicted K-factor in a mountainous agricultural watershed.To investigate the K-factor,the 54 km2 study watershed was divided into a 500 m by 500 m square grid and approximately at the center of each grid,topsoil samples(roughly 10 to 20 cm depth)were collected over 234 locations.Sand,silt,clay and organic matter(OM)percentage were analyzed,while soil permeability and structure class codes were obtained using the United States Department of Agriculture(USDA)document.The resulting coefficient of variation(CV)of the estimated K-factor was 0.31,suggesting a moderate variability.Meanwhile,the value of nugget to sill ratio of K-factor was 0.32,which categorized as moderate spatial autocorrelation.Prediction accuracy and model fitting effect of the Gaussian semivariogram approach was best,suggesting that the Gaussian ordinary Kriging model was more appropriate for predicting Kfactor.The resulting value of the mean error(ME)was 0 and the mean squared deviation ratio(MSDR)was nearly 1,which indicates the Gaussian model was unbiased and reproduced the experimental variance sufficiently.The values of K-factor were smaller(0.0217 to 0.0188)in the northern part and gradually increased(0.0273 to 0.033 Mg h MJ^(-1)mm^(-1))towards the central and south of the study watershed.

Influence of particle shape on the erodibility of non-cohesive soil： Insights from coupled CFD-DEM simulations

Soil erosion is a critical process that is being studied in soil science, hydraulic engineering, and geotech- nical engineering. Among many societal and environmental impacts, soil erosion is a major cause for the failures of bridges. The erodibility of soil is determined by its physical and geochemical properties and is also affected by surrounding biological activities. In most of the current models for soil erosion, erodibility of non-cohesive soil is characterized by its median grain size （Dso）, density, and porosity. The contribution to erodibility of the irregular shape of soil grains, which plays an important role in the mechanical and hydraulic properties of coarse-grained soils, is generally ignored. In this paper, a coupled computational fluid dynamics and discrete element method model is developed to analyze the influence of the shape of sand grain on soil erodibility. A numerical model for the drag force on spherical and non-spherical particles is verified by using the results from physical free settling experiments. Erosion of sand grains of different shapes is simulated in a virtual erosion function apparatus, a laboratory device used to mea- sure soil erodibility. The simulation results indicate that the grain shape has major effects on erodibility. Spherical particles do not show a critical velocity because of their low rolling resistance, but a critical velocity does exist for angular particles owing to grain interlocking. The erosion rate is proportional to the flow velocity for both spherical and non-spherical particles. The simulation result for angular particle erosion is fairly consistent with the experimental observations, implying that grain shape is an important factor affecting the erodibility of non-cohesive soils.

Soil erodibility mapping using three approaches in the Tangiers province–Northern Morocco

Soil erodibility is a key factor in assessing soil loss rates.In fact,soil loss is the most occurring land degradation form in Morocco,affecting rural and urban vulnerable areas.This work deals with large scale mapping of soil erodibility using three mapping approaches:(i)the CORINE approach developed for Europe by the JRC;(ii)the UNEP/FAO approach developed within the frame of the United Nations Environmental Program for the Mediterranean area;(iii)the Universal Soil Loss Equation(USLE)K factor.Our study zone is the province of Tangiers,North-West of Morocco.For each approach,we mapped and analyzed different erodibility factors in terms of parent material,topography and soil attributes.The thematic maps were then integrated using a Geographic Information System to elaborate a soil erodibility map for each of the three approaches.Finally,the validity of each approach was checked in the field,focusing on highly eroded areas,by confronting the estimated soil erodibility and the erosion state as observed in the field.We used three statistical indicators for validation:overall accuracy,weighted Kappa factor and omission/commission errors.We found that the UNEP/FAO approach,based principally on lithofacies and topography as mapping inputs,is the most adapted for the case of our study zone,followed by the CORINE approach.The USLE K factor underestimated the soil erodibility,especially for highly eroded areas.

Determination of rill erodibility and critical shear stress of saturated purple soil slopes

The hydrological conditions near the soil surface influence the soil erosion process,as determined by the soil erodibility and critical shear stress.The soil erodibility and critical shear stress of saturated purple soil slopes were computed and compared with those of unsaturated purple soil slopes.The detachment capacities computed through the numerical method(NM),modified numerical method(MNM)and analytical method(AM),from rill erosion experiments on saturated purple soil slopes at different flow rates(2,4,and 8 L min-1)and slope gradients(5,10,15,and 20°),were used to comparatively compute the soil erodibility and critical shear stress.The computed soil erodibilities and critical shear stresses were also compared with those of unsaturated purple soil slopes.At the different slope gradients ranging from 5°to 20°,there were no significant differences in the soil erodibilities of the saturated purple soil and also in those of the unsaturated purple soil.The critical shear stresses slightly varied with the slope gradients.The saturated purple soil was relatively significantly more susceptible to erosion.The NM overestimated the soil erodibility of both saturated and unsaturated soils by 31%and underestimated the critical shear stress.The MNM yielded the same soil erodibility and critical shear stress values as the AM.The results of this study supply parameters for modeling rill erosion of saturated purple soil slope.