In order to explore long term evolution of soil erosion from Benggang-derived sediment deposits

indoor simulated rainfall experiment was conducted with a 30。slope of the Benggang deposit and rainfall erosion intensity of 3.33 mm/min

which represented a typically higher rain intensity in the study region. The experiment was repeated with 20 times and the erosion processes of the deposit was carefully recorded. Under the experimental conditions

the average contribution rate of rainfall splash and runoff flush to sediment yield was 47.6% and 52.4%

respectively. The sediment yield of colluvial deposits decreased exponentially in the process of erosion. The sediment yield was correlated with Froude number

Runoff power and Darcy-weisbach resistance coefficient

and these parameters could be used to quantitatively describe the efficiency of runoff sediment yield when the source of sediment was sufficient. Four stages of the erosion process from the colluvial deposits were founded

including (1) sheet erosion stage on the whole slope

the sediment concentration was 0.099 kg/L

and the sheet erosion was dominant

but the slope surface was not coarsening; (2) Initial formation stage of rill erosion

the sediment concentration was from 0.052 to 0.101 kg/L

mainly with rill erosion

but the slope coarsening was not obvious; (3) Stage of frequent expansion of rills with coarse slope

the sediment concentration was from 0.011 to 0.064 kg/L

mainly with rill erosion

and the coarsening of slope surface appeared; (4) The stage with frequent collapsed rills even forming ephemeral gully

the sediment concentration was from 0.008 to 0.036 kg/L

and there was no obvious dominant erosion mode

and the slope surface continued to coarsening. The separation and transportation of colluvial deposits by rainfall and its runoff results in the coarsening of the slope

and the coarsening of the slope

which in turn reduced the rainfall and runoff sediment yield.