A Preliminary Quantitative Analysis of Soil Erosion Intensityon Loess Plateau since the Holocene

Since the Holocene the soil erosion process in the Loess Plateau can be divided into 5 stages, of which starting times are 11, 7.0, 0.7, 0.3 and 0.15 ka B P. The regression equations of some parameters of modern rivers in the plateau are established by using the data of grain size of sediments, sediment discharge of river, annual runoff and precipitation. Based on the measured data of the samples in each terraces the paleoerosion intensity and paleosediment discharge in various stage of the Holocene are calculated from the regression equations. The study result indicate the difference of the factor forcing soil erosion: tectonic forcing during 11 000~7000 a BP, climatic forcing during 7 000~2 000 a BP, manmade forcing during 2 000~700 and in the past 300 a BP, and coupled forcing during 700~300 a BP. Clipping change of natural process is stronger generally than that of human activity, but the soil erosion intensity caused by human is bigger by 45.5% than that by natural factors at present. 