Abstract: Because Shenfu dongsheng minesite is located in arid and semiarid transition region, there are undulate and incoherent terrain, the ground surface material is loose and ready for weathering, the vegetation covered degree is low, the soil suffer various erosion, natural disasters take place frequently and its eco environment is fragile. Based on the fragile eco environment, coal mining and construction have brought out some new environmental problems since 1986. Man made debris flow problem is the most serious of them, which is caused by coal mining, construction of raiway and highway as well as exploiting stone. The man made debris flows threaten the existance and sustaining development of coal mine, the security of inhabitant, the smooth of communications and transportation Because of the particularity of forming process of man made debris flow, the watershed geomorphy of it is very distortional.According to extensive field investigation in the region and 1:10 000 topographic map measure, and systemtically analying every landform factors of the watershed, the results show as follows: ① the gully bed gradient takes convex shape as the dominant, this is a unique form of man made debris flow gully; ② regional area ratio is the largest in converge water region, and the fan shaped watershed makes up 80 percent of the total sample gullies, it is favourable to water concentration, a particular demand of motive power of debris flow in semiarid area. ③ the landform's rugged coefficient of watershed is smaller and the area of providing water for gully formation is larger in semiarid region than in moist region. According to information entropy principle and fractal dimensions values, debris flow gullies are divided into four evolution phases: infancy phase, youth phase, mature phase and old phase. Most of debris flow gullies in the region are at infancy and youth phase, which pointed out that debris flow potential danger would be very serious. One watershed is an integrated system in which every topographic factors influences each other. The affect on debris flow happening of various topographic factors are different. According to fuzzy information evaluation principle, the connected degree of various factors to debris flow happening were evaluated. The results of evaluating predominant indicators, watershed area (S₁), gully length(S₂), gully bed gradient(S₃), information dimension (S₄), shape coefficient of basin(S₅), rugged coefficient (S₆) and slope length (S₇), show an order: S₃ > S₂ > S₁ > S₄ > S₇ > S₅ > S₆.

Key words: semiarid region, man made debris flow gully, watershed geomorphologic factors, information dimensions, connected degree