Development Characteristics And Hazard Assessment Of Daniubagou Debris Flow In Jiuzhaigou County

Daniubaogou debris flow is located in Xinyang Village,Wujiao Township,Jiuzhaigou County,Sichuan Province.It is about 28 km away from the county town.S205 Provincial Road passes through the mouth of the valley.The disaster site is on the left bank of Tangzhu River.The area of the valley is about 18×104 m2 and the length of the main Valley is 800 m.It is a slope-type debris flow.The disaster body is located on the left bank of tangzhu river.The debris flow gully broke out twice in 1976 and 2003.Afterwards,affected by the “5.12” and “8.8” earthquakes,the scope of debris flow gradually expanded,and the loose solid sources in the gully increased.Under the action of runoff,the gentle slope area in the upper reaches of the gully has obviously collapsed downward.It is predicted that a large-scale debris flow disaster will occur when the rainfall reaches the stimulating rainfall,which will directly threaten the lives and property of about 248 villagers in 73 households downstream of the gully.At the same time,the roads and rivers located at the gully will also be threatened by siltion and congestion.Therefore,it is of great practical significance to study the development characteristics and risk assessment of the debris flow in Daniubagou in detail.The main contents of this paper are as follows:(1)Through on-site investigation and collection of relevant data,the natural and geological environment conditions of Daniubagou debris flow and the distribution of provenances in the gully area were identified.(2)The development characteristics of the Danubagou debris flow are analyzed,which are mainly the basin characteristics and formation conditions of the Danubagou debris flow.According to the topography and material source characteristics,the Daniubagou debris flow basin is divided into clear water area,circulation area and accumulation area.By means of engineering geological survey,geophysical prospecting and trench exploration,the source types and distribution characteristics in Daniubagou are determined,and the forming conditions are analyzed in detail.(3)Calculating the motion characteristic parameters of Danubagou debris flow,That is to calculate quantitatively the parameters of volume weight,velocity,flow rate and total amount of debris flow process.it is concluded that the Danubagou debris flow belongs to the viscous debris flow on the slope and is in the stage of development.(4)Based on the study of the development characteristics of debris flow and the calculation of dynamic characteristic parameters,the risk assessment model of single gully debris flow improved by Liu Xilin and the evaluation model based on analytic hierarchy process are used to evaluate the risk of Daniubagou debris flow.The evaluation results of the two methods are compared with the quantitative scoring results of field investigation.It is concluded that the evaluation results based on the analytic hierarchy process are in good agreement with the field investigation results.It also shows that the analytic hierarchy process can accurately get the dangerous grade of Daniubagou debris flow.(5)According to the development characteristics,dangerous grade and protection object of the debris flow in Daniubagou,the engineering control measures of "drainage channel + flood dike" are put forward,and the comprehensive control of debris flow in Daniubagou is carried out in combination with biological control measures.