A debris flow broke out on July 8

2004 in Qieduke gully of Seda county

Sichuan province

and caused economic loss. “7.8”debris flow in Qieduke gully is classified as moderate-scale and moderate-hazardous catchment. The debris flow

with maximum velocity of 10.4 m/s

maximum discharge of 156 m3/s

and runout deposits of 70

000 m3

had the characteristics of high density

strong impact and straight movement. So “7.8” debris flow in Qieduke gully was of viscosity. This paper made a quantitative research on the evolution stage

hazardousness and the maximal dangerous boundary of the debris flow in Qieduke basin. Countermeasures against debris flow of Qieduke gully include constructing protection wall against erosion at the bend of the gully and building a valley shop at the upper stream in Sequ river.