The Activity Characteristics And Engineering Prevention And Control Measures Of Gangou Debris Flow In Longtou Town, Ludian County, Yunnan Province

The Gangou Debris Flow Gully in Longtoushan Town,Ludian County,Yunnan Province is located on the right bank of the Longquan River,a primary tributary of the Niulan River.There were large-scale debris flows that occurred at 19:25 on May 8 in 1997 and on July 27 in 1997.They were extremely large-scale geological disasters and this place was identified as one of the key geological disaster control projects in Zhaotong Municipality,Yunnan Province in 2013.Due to the fragile geological environment and affected by the earthquake hit in Ludian County in August 3,the provenance of the debris flow in the post-earthquake basin has increased suddenly in a short time,the damage degree of the debris flow has strengthened and the likehood of the recent large-scale outbreak has also increased.Moreover,the main threat of the debris flow has been changed to the post-earthquake reconstructions.The main research work and results are stated as follows:(1)The Gangou debris flow is diluted during the development period(the mature age).The pre-earthquake proneness is moderate,and the post-earthquake proness is extremely large.The rainstorm intensity index is dangerous and the activity intensity is "strong".(2)The risk of debris flow activity is divided into three zones;the accumulation areas are highly dangerous,the circulation areas in the middle and lower reaches are dangerous,and the external slopes are affected.The overall activity of Gangou debris flow is a serious hazard and the probability of disaster occurrence is also large.(3)The check dams under construction have been silted up;the dams are in an overloaded state and comprehensive prevention measures need to be taken.(4)Through comprehensive analysis and combined with previous successful experience,comprehensive prevention and control measures for the bank slope protection project with dams,drain and guide ditches,and the rock blasting are recommended.