| Loessal slope in western Shanxi can cause severe soil erosion due to its widely distributed landform of hilly and gully and concentrated short-duration rainstorm.Based on the different combinations of slope lengths and artificial rainfall intensities in the laboratory and field,taking the bare slope of the loessal soil in western Shanxi as the object,this study researched the characteristics of runoff and sediment yield,and evaluated the applicability of EUROSEM in the process of soil erosion in study area.Based on the comparative analysis of laboratory and field soil erosion modulus,the reasons for the differences were analyzed,and a preliminary conversion was carried out.The main conclusions are as follows:1.The runoff and sediment yield increased with the increase of rainfall intensity and slope length,under the condition of 2-5m slope length and rainfall intensity was from50mm/h to 120mm/h.There was an exponential relationship between them and rainfall intensity(R~2>0.95),and a linear relationship with slope length(R~2>0.84).When the slope length was extended in increment of 1m,there was no significant change of the increment of runoff and sediment yield under various rainfall intensities,but peaks always appeared when the slope length increased from 3m to 4m and 4m to 5m.In view of this,it is recommended to arrange soil and water conservation measures at an interval of 4m to slow down the soil erosion on the bare slope of loessal soil in western Shanxi.2.After the rapid increase of runoff yield,with the extension of runoff duration,the growth rate slowed down and finally tended to be stable.When the rainfall intensity was50-80mm/h,the sediment yield tended to increase,while when it was 90-120mm/h,the value tended to fluctuate,and the fluctuation degree increased with the increase of rainfall intensity and slope length.When the slope length was 2-5m and the rainfall intensity is greater than60mm/h,the sediment yield increased significantly.Therefore,60mm/h may be the lower limit of rainfall intensity for the significant increase of soil and water loss in the area.3.Both the field measured runoff rate and the simulated value of EUROSEM increased first and then tended to be stable with the extension of rainfall duration,but the peak time of them was slightly different.The measured sediment rate increased sharply in the initial stage of runoff duration and then stabilized in fluctuations,while the simulated value showed a stable trend after the fluctuation growth,and the first peak time was about 5 minutes earlier than the actual one.Under the condition of 4m slope length,the simulated values of runoff and sediment yield were almost greater than the measured one,and the measured and simulated values had a significant linear relationship(R~2were greater than 0.984).The efficiency coefficients ME were 0.978 and 0.974 respectively,and the relative error Re range between the simulated and the measured value were-12.95%-9.04%and-14.72%-24.13%.Therefore,the simulation effect of this model on the runoff yield is better than that of the sediment yield.In summary,the model was well applied to loessal slope in the area.4.Under the experimental conditions,the sediment discharge of unit width of laboratory and field increased first and then tended to be stable with the runoff duration,but the laboratory value and its fluctuation were grater than those in the field,and the response time was shorter.The results of runoff modulus and erosion modulus in the laboratory experiment were both larger than those in the field,and the ratio of runoff and sediment yield in the field and laboratory was not the ratio of the two areas,so it is impossible to simply multiply laboratory results by area to predict the amount of soil erosion in the field.It is preliminarily concluded that the conversion coefficient of erosion modulus of laboratory and field is 0.48. |
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