The shape and depth of scour pit after debris flow sabo dam is one of the weak links in the research of debris flow erosion.Therefore

this paper discussed this point by a series of indoor flume experiment.The longitudinal cross-sections present shape characteristics as deep at the middle and shallow at the ends and the site of the deepest point is moving to lower reaches with the increase of the longitudinal gradient at same experimental conditions.The lower reaches’ slope in the scour pit is slower than the upper’s.Compared the slopes in the scour pit in viscous silt and non-viscous silt with the same grain composition

the former is much steeper than the later.The maximum depth of the scour pit is affected by the longitudinal slope

the volumetric weight of debris flow and the property of the silt on the bed.Under definite experimental conditions

it increases with the increase of the longitudinal slope of flume and decreases with the increase of the volumetric weight of debris flow.The results show that the viscosity of the silt reduces the depth of the scour pit greatly.