Hazard assessment of debris flow is the necessary prerequisite for the control schemes and project designs of debris flows. The four large-scale debris flow gullies of Banzi

Taoguan

Dengji and Chediguan distributed along Minjiang river greatly threaten the safety of the highway bridges cross the gullies. The debris flow hazard assessment results show that Dengji

Banzi and Taoguan gullies are of high hazardousness with hazard values of 0.74

0.69 and 0.68 respectively

which may cause large disasters and huge damages. Chediguan gully has hazard value of 0.50

belonging to moderate hazardousness. The debris flow gullies of Banzi

Taoguan and Chediguan generate low frequency and low viscous debris flows or hyper-concentrated flows with an average interval of 20～50 years. Dengji gully has a high frequency of occurrence of debris flows or hyper-concentrated flows with an average interval of 5～10 years. Once the quarries in Banzi and Taoguan gullies have been stopped

there are no evidences indicating that there might be an increasing trend of debris flow activities in these gullies.