Evolution Of Microrelief Features During Rainfalls And Etablishment Of 3D Models For Different Soil Surface Roughness

As an indicator to reflect the form of microrelief and physical characteristics, soil surface roughness plays an important part in water and soil conservation and the soil erosion research. However, the quantitative information about the soil surface roughness in erosion process is very limited. The paper made three different soil surface roughness according to the soil samples of purple soil aggregates which are 3-5mm,2-3mm and less than 2mm. From the measurable changing aspect of soil surface roughness and MDS in hydraulic erosion process, the paper also studied the temporal and spatial variation features of the soil surface roughness and MDS for the three different soil surface roughness in the different parts of slope throughout the indoor artificial rainfall so as to make sure the changes in the erosion process and its function. The research of the influence of microrelief on the erosion process and its change during the process has great significance on establishing the soil erosion model based on the process.What's more, it enriched the quantitative research on the process and mechanism of soil erosion by improving Gaussian model and Fractal model and establishing the simulate model that can be suitable for different soil surface roughness.1.Roughness index was selected by evaluating the applicability of random roughness, microrelief index an peak frequency, tortuosity, mean upslope depression and limiting elevation different and slope in the microzone. The method of calculating MDS was evaluated by J&D algorithm and M&V algorithm.The results indicated limiting elevation different and slope was the best roughness index, the difference between MDS calculated by J&D algorithm and calculated by M&V algorithm was not statistically significant, the higher the sampling precision was, the more small depression can be obtained, and the more precise MDS can be.2.Using laser scan to study quantitatively the changes of characteristics of microrelief during rainfalls. The results illustrated that the temporal and spatial variation features of roughness and MDS of different parts of slope under different slopes for three different soil surface roughness showed inconsistency. Slopes had significant effects on the changes of characteristics of microrelief for smooth soil surface, the medium rough soil surface took second place, and the rough soil surface had minimum effects on the changes of characteristics of microrelief. With the increase of slope, the roughness and MDS of different parts of slope for three different soil surface roughness showed an increasing trend. The roughness and MDS of different parts of slope for one slope showed the trend:the middle of slope decreased larger or increased smaller than the bottom of slope, the bottom of slope dropped off larger or increased less than the upper of slope.3.The MDS and LD·LS of rough soil surface simulated with MNG were equal to observed soil. Although there were differences on frequency distributions of heights, coefficient of skewness, semivariogram between simulated soil surface and observed soil, the simulated requirements according to the features of microrelief were reached. Thus the method was fit for the simulation of rough soil surface. The MDS and LD·LS of the medium rough and smooth soil surface simulated with MRMD were equal to observed soil.Besides, there were a little differences on semivariogram between simulated soil surface and observed soil.Therefore this method was fit for the simulation of medium rough and smooth soil surface.