Mechanism and mitigation of catastrophic debris flow disaster at Zhouqu county, Gansu

In the evening of 2010.8.7 at 23:00,there fell intense storm unexpectedly in Sanyanyu valley and Luojiayu Valley of Zhouqu County,Tibetan Autonomous Prefecture of Gannan,Gansu Province.There were two flood currents formed at Sanyanyu tributary and Luojiayu upper reaches.After 40 minutes,catastrophic debris disasters were formed in the two debris valleys.Because of the specific pointed mountain peak and deep valley terrain,additionally abundant loose matters at the surface of side slope,dropping intense storm in rainy season induced the occurrence of this debris.This paper analyses the forming causes of this debris flow from the potentiality of the debris valley's formation,the rainfall inducing factor of debris flow and the unreasonable construction and development of urban.As debris frequent happen area,we can take monitoring and prediction measure,reinforce the management to restrain human activities,and implement engineering treatment synthetically method which can decrease and avoid the occurrence of the condition of disaster.