| Loess Plateau in China is the most serious soil erosion areas in the world, and the erosionhas resulted in serious impacts and threats to the local sustainable development and securityof the downstream areas of Yellow River. Sheet erosion especially for the steep slope is one ofthe important erosion processes existing in a large area in the Loess Plateau, and the sheetflow from the large areas is the main power of various gullies erosion. Chemical regulation onerosion is a non-traditional measure of water and soil conservation. Jag S and Jag C162aretwo kinds of new chemicals. Researches of the regulation of Jag S and Jag C162on dynamicsheet processes on loess hillslope can help understand the dynamic sheet processes, and alsoreveal the effect of Jag S and Jag C162on dynamic sheet processes. The study can promotethe further development of the theory of sheet erosion and supply scientific basis for theerosion control.Regulations of Jag S and Jag C162on the dynamic processes of sheet erosion on loesshillslope are studied under simulated rainfall experiments with the rainfall intensities of1.0mm/min,1.5mm/min,2.0mm/min and slopes of10°,15°,20°and dosage of1g/m2,3g/m2,5g/m2and the cast way of dry spreading and spraying. The study focuses on the effect of JagS and Jag C162on the processes of sheet erosion, top soil characteristics and hydrodynamiccharacteristics. The main results are as follows:1. Based on the the effect of Jag S and Jag C162on runoff, erosion and the relationshipof runoff and erosion, the regulations of Jag S and Jag C162on the sheet erosion are analyzed:(1) For the treatments of dry spreading and spraying Jag S and Jag C162, the variations ofrunoff rates with times are similar with that of bare slope, in the trends of a rise in thebeginning and then going to a stability or a low-slope rise; Compared with bare soil, runoffsof5g/m2Jag S increase by6%to25%and with an average increase of18%under the way ofdry spreading, and increase by9%to23%and with an average increase of14%under the wayof spraying(excepting a decrease of32%under1.0mm/min), and in the other treatments, thehigher the doses, the less runoffs, and runoffs decrease by6%to24%and with an averagedecrease of15%under the way of dry spreading Jag S(excepting a increase of4%under1.0mm/min), and decrease by18%to57%and with an average decrease of32%under the way of spraying Jag S, and decrease by25%to81%and with an average decrease of51%underthe way of dry spreading Jag C162, and decrease by48%to79%and with an averagedecrease of64%under the way of spraying Jag C162; The decrease effect of spraying is betterthan dry spreading, and the increase effect of dry spreading is better than spraying for5g/m2Jag S;(2) For the treatments of dry spreading and spraying Jag S and dry spreading Jag C162,the variations of erosion rates with times are similar with that of bare slope, in the trends of arapid rise in the beginning and a rapid fall and then going to a stability, and erosion rates ofspraying Jag C162behaves the trend of a progressive rise and then going to a stability; Thestarting times of dry spreading and spraying Jag S and dry spreading Jag C162are earlier thanthat of bare slope while that of dry spreading Jag C162is unfixed; Compared with bare soil,all the treatments can decrease erosion, and the higher the doses, the less erosions, anddecrease by32%to72%and with an average decrease of57%under the way of dry spreadingJag S, and decrease by19%to69%and with an average decrease of46%under the way ofspraying Jag S, and decrease by44%to71%and with an average decrease of55%under theway of dry spreading Jag C162, and decrease by28%to61%and with an average decrease of44%under the way of spraying Jag C162; The decrease effect of spraying is better than dryspreading;(3) For all treatments, erosion modulus increases with runoff depth, behaving inthe same way with bare slope; The higher the doses, the less the increase, showing greaterreduction effect on sediment than runoff (there’s little difference between spraying1g/m2and5g/m2Jag C162and bare slope, showing same reduction effect of sediment than runoff).2. Based on the effect of Jag S and Jag C162on>0.25mm water stable aggregates andsoil shear strength, the regulations of Jag S and Jag C162on soil characteristics(closelyassociated with the anti-erosion) are analyzed:(1) Treatments of dry spreading and sprayingJag S and Jag C162can increase the content of aggregates, and the higher the doses, thehigher the content; Compared with bare slope, aggregates increase by3.0%to16.1%and witha total increase of39.8%under the way of dry spreading Jag S, and increase by0.3%to21.3%and with a total increase of41.9%under the way of spraying Jag S, and increase by0%to21.1%and with a total increase of21.1%under the way of dry spreading JagC162(excepting a>5mm content of0%under1g/m2), and increase by0.9%to24.9%andwith a total increase of42.8%under the way of spraying Jag C162; The increase effect ofspraying is better than dry spreading;(2) All treatments can increase the shear strength, andthe higher the doses, the higher the shear strength; Compared with bare slope, shear strengthincrease by25.0%to111.0%and with an average increase of63%under the way of dryspreading Jag S, and increase by92.9%to241.7%and with an average increase of169%under the way of spraying Jag S, and increase by60.0%to65.5%and with an average increase of63%under the way of dry spreading Jag C162, and increase by173.3%to305.4%and with an average increase of237%under the way of spraying Jag C162; The increaseeffect of spraying is better than dry spreading.3. Based on the the effect of Jag S and Jag C162on flow velocity, runoff depth,Darcy-Weisbach coefficient, Reynolds number, Froude number, and the relationships betweenerosion and hydrodynamic parameters including shear stress, stream power and unit streampower, regulations of Jag S and Jag C162on hydrodynamic parameters are analyzed:(1) Forthe treatments of dry spreading and spraying Jag S and Jag C162, the variations of hydraulicparameters with times are similar with those of bare slope but a little difference in processes;(2) Compared with bare slope, all treatments can decrease flow velocity, runoff depth,Reynolds number and Froude number(excepting a increase of flow velocity and Froudenumber under5g/m2Jag S, and excepting a increase of runoff depth under dry spreading5g/m2Jag S): an average decrease of11%,7%,20%,8%respectively under the way of dryspreading Jag S, and the higher the doses, the less the decrease, and an average decrease of18%,18%,24%,7%respectively under the way of spraying Jag S, and the higher the doses,the less the decrease, and an average decrease of36%,15%,50%,30%respectively under theway of dry spreading Jag C162, with order of the decrease:3g/m2>5g/m2>1g/m2, and anaverage decrease of36%,47%,67%,10%respectively under the way of spraying Jag C162,and the higher the doses, the more the decrease; Jag C162increases Darcy-Weisbachcoefficient by86%averagely under the way of dry spreading and by11%underspraying(excepting decrease by5%under1g/m2), with order of the decrease:3g/m2>5g/m2>1g/m2; The decrease effect on flow velocity, runoff depth, Reynolds number andDarcy-Weisbach coefficient of spraying is better than dry spreading(excepting the increaseeffect on Froude number of spraying Jag C162is better than dry spreading), and the decreaseeffect on Froude number of dry spreading is better than spraying(excepting the decreaseeffect of spraying1g/m2Jag C162is better than dry spreading, and excepting the increaseeffect of spraying5g/m2Jag S is better than dry spreading);(3) For all treatments includingbare slope, stream power is the closest hydrodynamic parameter related to sheet erosion,showing Jag S and Jag C162can not change the erosion power; Sheet erosion modulusincrease with average stream power, behaving the same way as bare slope but lower sloperises with higher doses(excepting1g/m2Jag C162), showing greater reduction effect onsediment than stream power; Compared with bare slope, all treatments can decrease streampower, stream power decrease by19%to24%(excepting a11%increase under5g/m2) andwith an average decrease of21%under the way of dry spreading Jag S, and decrease by21%to39%(excepting a6%increase under5g/m2) and with an average decrease of30%under the way of spraying Jag S, and decrease by30%to48%and with an average decrease of41%under the way of dry spreading Jag C162, and decrease by52%to72%and with an averagedecrease of63%under the way of spraying Jag C162, showing the decrease effect of sprayingis better than dry spreading(excepting the decrease effect of dry spreading is better thanspraying under5g/m2Jag S).4. The regulations of Jag S and Jag C162on the dynamic process of sheet erosion areanalyzed: Water erosion depends on hydrodynamic forces and soil resistance to erosion. Jag Sand Jag C162can effectively reduce the erosion by effectively improving top soilcharacteristics (closely associated with the anti-erosion) including>0.25mm soil water stableaggregates and soil shear strength, and by effectively reducing hydrodynamicparameter-stream power closely associated with the anti-erosion. |
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