Study on Variation Characteristics of Eroded Sediment in Purple Soil Steep Slope Land Based on Simulated Rainfall

The response characteristic of eroded sediment in 25° runoff plots was studied based on three different simulated rainfall intensity which were 0.285 mm/min,0.978 mm/min and 1.737 mm/min,respectively.The results were as follows: The quantity of runoff sediment increased firstly and then reduced gradually and tended to be stable finally with the runoff duration extended during rainfall process.The time of peak quantity of eroded sediment occurred brought forward constantly along with the increase of rainfall intensity during runoff generation process.Accumulative sediment-runoff of slope runoff showed a relationship of power function with the increase of runoff duration.Accumulative sediment runoff with large rainfall intensity was obviously larger than that of small rainfall intensity.With the same runoff duration,when rainfall intensity were 0.285 mm/min,0.978 mm/min and 1.737 mm/min,the content of sand in eroded sediment decreased roughly,and the content of clay and silt increased roughly with the increase of runoff duration.But the variation of particle size composition of eroded sediment was obvious different under different rainfall intensities.The larger rainfall intensity was,the better eroded sediment particle size composition and runoff duration regression model fit.