PROCESS OF RAINFALL EROSION AND SEDIMENT VIELD ON SILTY SLOPE AND ITS DYNAMIC MECHANISM

The Loess Plateau of China is facing a series of ecological environment problems and geological disasters,such as serious degradation of ecological environment and frequent superficial disasters on slopes. It is of great significance to study the rainfall erosion process and dynamic mechanism of silty soil slope in the Loess Plateau for local soil and water conservation work. In this paper,the erosion process,morphology and dynamic characteristics of slope erosion process under different rainfall intensity(60h^-1,90h^-1,120h^-1),slope(30°,34°,38°) and vegetation coverage(30%,60%)were studied by field simulated rainfall experiments on typical experimental slopes. The main research results are as follows: (1)The initial runoff time of slope under different experimental conditions is between 56s and 100s; slope infiltration,runoff and sediment yield change obviously with rainfall intensity,slope and vegetation coverage; the runoff yield is a power function,and the sediment yield shows the characteristics of rapid increase at first and then slow decrease. (2)After rainfall,the morphological parameters of rills change obviously. Combined with the DEM data,the rills on the slope show the characteristics of narrow and shallow in the upper part but wide and deep in the lower part. In general,the rill development degree is the highest under 90h^-1 rainfall intensity. (3)The average velocity of rill flow on the slope increases with the increase of rainfall intensity and slope,and decreases with the increase of vegetation coverage. According to the calculated hydraulic parameters,the characteristics of slope flow are "turbulent slow flow". (4)There is a significant linear correlation between the average sediment yield rate and the average runoff shear force,the average runoff power and the unit runoff power,and the unit runoff power is more suitable to describe the process of sediment yield in the study area.