On the basis of scouring experiments indoors

the mechanism of the drop pit'genesis and development during the process of slope erosion is analyzed

and the relationship among headcut

bank landslip and downcut has been expounded. The variation regularity of the runoff and the sediment yield in each discharge was studied

and the relationship among the sediment

the runoff and the proportion of the rill area was obtained. Analyzing each erosion stress on the slope during the scouring

we get the runoff shearing sediment equation. The study shows that the sediment yield from runoff shearing take on a good positive correlation with the average runoff shear stress

and the critical shear stress of the runoff

by which the soil grain can just be dispersed

is 0.258 N/m2.