Study on spatial and temporal characters of rill erosion on slope

Combined with the runoff scouring method and the rare earth element (REE) technology,the temporal and spatial variation laws of the sediment yield on slope are studied in this paper.The results show that the process of sediment yield on slope can be divided into the following three stages,interrill erosion stage,intensive rill erosion stage and rill erosion declining stage.The results indicated that the ratio of the amount of sediment yield in the various period to the amount of total sediment yield augments at the beginning and decreases at last during the runoff scouring experiment under the different flow discharge and the different slope gradients Under the same flow discharge,the maximum value of the ratio shows a tendency of appearing in advance with the slope gradient increasing.The intensive rill erosion stage accounts for the main sediment yield,which contribute 52%~75% to the total sediment yield in the whole experiment.The relative erosion mass of the different section a long the slope decreases at first and increases at last during the runoff scouring experiment Experiment on the steeper slope with smaller flow discharge indicates that the relative erosion mass of the different section along the slope is similar to that on the gentle slope.When the flow discharges is larger,the relative erosion mass decreases with the length of slope increasing.The temporal variation of sediment yield on slope is that the relative erosion mass at the bottom section of the slope decreases with experimental time length of the experiment,while the relative erosion mass on other section increases fluctuantly.