Application Of WEPP Model (hillslope Version) To The Hillslopes Of Expressway Of Purple Soil Of Water And Soil Loss

The research on soil erosion prediction model is of great significance to the soil and water conservation plan formulation and layout of soil and water conservation monitoring. As a model based on the erosion process, water erosion prediction model WEPP can provide detailed and comprehensive description related to soil water erosion process. The application of WEPP model on purple soil area also is less, so there is practical significance to predict the water erosion of purple soil area. Based on WEPP(Slope Vision), highway slope water and soil erosion prediction of purple soil area under rainfall condition is studied, and the Model validity ME(Nash- Sutcliffe Model Efficiency) is used to the evaluation of the applicability of WEPP. WEPP model(slope version) is finally applied to the highway construction projects named liangping-zhongxian to forecast runoff and sediment yield, which is aimed to layout of soil and water loss monitoring, and provide reference for the establishment of soil and water conservation measures.Main contents and results include:①The analyses of soil particle size, organic, cation exchange capacity are carried out to get the basic parameters of purple soil area. The percentage of rock, sand, silt and clay is separately 5.70%, 34.21%, 56.73% and 3.36%.The percentage of organic is 2.448% and CEC is meq/100 g. The soil parameters needed in WEPP model is calculated by the formula, the albedo is 0.59, SAT is 52.25%, rill erodibility is 0.0144s/m, soil critical shear stress 0.5683 Pa and effective hydraulic conductivity is 6.3461 mm/l.②The files of soil, climate, slope and management which is needed to run WEPP is established. Based on the measured data of 20 rainfall in slopes of 15°,the runoff and sediment yield are predicted. As the results show, there is little difference between the measured data and predicted data. The percentage of relative error less than 30% of runoff and sediment yield are separately 80.95% and 42.84%. And the ME of runoff and sediment yield are respectively 0.9288、0.7862. Therefore, in the prediction of single rainfall in purple soil, the accuracy of the WEPP model simulation on sediment yield is lower than on the runoff, but the predicted values and measured values can still show the same change trend which can reflect the single rainfall erosion in a certain degree. As a result, the WEPP model has certain applicability in the purple soil slope area.③Based on WEPP model, the single runoff, sediment yield, runoff for many years and sediment yield for many years with different slope and management is predicted. And the change laws with slope are analyzed. In the condition of a single rainfall process parameters unchanged, runoff shows little volatility and sediment yield first increases and then decreases with the increase of slope.The sort of sediment yield growth is R5,10>R10,15> R15,20>… …> R65,70. Through parameter sensitivity analysis of the rainfall process, sensitive sort is defined: rainfall amount > max intensity > rainfall duration >TP.④The WEPP model is applied to 50 slopes of liangping-zhongxian project to predict the runoff and sediment yield. The simulation results show that the runoff and sediment yield of XP29, XP35, XP44, XP50 are at a higher level, which should be of the key monitoring and protection sites in the process of construction.