关键词: 坡面侵蚀;微地形因子;断续降雨;细沟形态;

Abstract: In this paper, aiming at topographic information of grid units on loess slope at different stages of intermittent rainfall, an artificial simulated rainfall test is carried out with 12 segments of 30 min and intensity of 60 mm/h, and the interaction between micro slope, micro slope direction, erosion process of loess slope and rill shape evolution is studied.The results show that the changes of micro slope gradient and micro slope direction are mainly concentrated in the initial stage of precipitation(0～30 min),while the changes in subsequent stages(30～360 min) are small.The changes of micro slope gradient and micro slope direction are significantly positively correlated with the erosion amount during periods.After the formation of rill network, the proportion of grids in the areas with slope less than 15° and above 45° increases slowly, which mainly occurs in the interior of the rill.The platform of sediment accumulation and steep slope will generate during the development of the rill interior.The development process of rills is a non-uniform development process in which the erosion by runoff in rills and collapse of unstable soil mass at the side walls work together.The erosion of runoff and collapse of soil mass promote each other and accelerate the development process of rills, thus causing fluctuations of erosion amount.During the course of rill erosion, the micro direction of rill is dominated by the gradient direction of slope, and the proportion of gradient grid remains unchanged after 30 min, while the total surface area of rills gradually increases, which indicates that the number of rill grids having the same direction with the slope increased.A bottom of certain width will generate in the rill, and rill section is transformed from V to U shape.Except for the north outward direction, the changes of grid number of rill directions are significantly related to the density of rills, the cleavage degree, the complexity of rills, the accumulated length of rills and the average width of rills.The number of grid of rill direction can better reflect the changes of the form of rills on the slope surface.

Key words: slope erosion; micro terrain factor; intermittent rainfall; rill morphology;