| Meinv watershed is located in Xiacun village,Lihui county,Liangshan,Sichuan province,which is one branch of Yanjia River at left bank.Two debris-flows occurred in1976 and 1990,of which a large scale occurred on May 31,1990.The debris-flow destroyed more than 10 houses,clogging culverts and overspreading highways. According to the investigation and evaluation,the debris flow gully is highly likely to cause debris flow again,which directly threatens the safety of life and property of residents in the village,the rural roads and power lines,with potential economic losses of about 23 million yuan.Therefore,it is necessary to control the debris flow.This paper carried out the investigation of environmental geological conditions,formation and development characteristics of debris flow in the watershed,the calculation and evaluation of debris flow vulnerability,and the calculation and evaluation of debris flow characteristic parameters.The work and achievements of the paper are as follows.1.Through field investigation,the environmental and geological conditions of the Meinv watershed were found out.The watershed is a tributary of the left bank of Yanjia river.The gully area is 3.54 km~2,the main gully length is 3.32 km,the average longitudinal slope is 252‰,and 4 branches are mainly developed.The water catchment area of the formation zone is large,with steep topography on both sides of the main channel and abundant material sources.In the flow zone,there are deep gully,steep bank slope and poor vegetation development.In the accumulation zone,the slope of the upper segment is steep,the groove of the lower segment is wide and flat,and a large amount of loose debris flow material is accumulated in the upper segment gully.The average annual precipitation in the watershed is about 1147.8 mm,mainly concentrated in May to September and mostly in heavy rain.The good conditions of debris flow are found in topography,material source and water source.2.There are mainly five types of material sources in the Meinv watershed,including slag deposit source,highway waste residue source,slope erosion source,collapse and landslide accumulation source,and gully deposit source.The total content of material sources is about 21.19x10~4 m~3,and the dynamic reserves are 4.37 x10~4 m~3,providing abundant material sources for the formation of Meinv debris-flow.3.Meinv gully is a low-frequency debris flow gully,which is in the development stage with a scale of medium size,and the probability of occurrence of debris flow is high.The danger of debris flow is predicted.Heavy rain is the main cause of debris flow induced in steep terrain and abundant source conditions.4.According to relevant specifications,the parameters such as selfweight of debris-flow mass,flow rate,flow volume,amount of flow and amount of solid material at one-time debris-flow,as well as the overall impact pressure,climb and maximum impact height of debris flow are calculated.The result can provide basic parameters for the design of debris flow prevention project.5.According to the management idea of combination of stabilization,obstructing and drainage,two kinds of debris flow control schemes are proposed.Through comparison of the two type of scheme from technology and economy,the project plan of“2 drains+1 parapet wall+1 comb dam+drain channel”is adopted.It can provide scientific basis for effective control of debris flow in Meinv watershed. |
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