The Evolutionary History And Evaluation Of Risk Of The Daseer Debris Flow In Lixian

Due to lack of understanding of the law of debris flow activity, coupled with topography influence by the mountains of Southwest China, people often built towns or factories in some relatively open terrain of old debris flow accumulation fan.After the debris flow bring back to life, it destroys buildings, landfill factories and mines, often resulting in heavy losses. And the old densely populated county town is building in the tail of the river mouth,which involved large-scale multi period of ancient debris flow fan, if the outbreak of debris flow is similar to the historical scale, the consequences will be unimaginable. The study of history has a certain reference for the upper reaches of the Minjiang River debris flow evolution and the evolution analysis of debris flow. And whether the river will happen the history of the size of the debris flow is a very important issue of real significance.on the basis of collecting and sorting geological information, of ancient debris flow accumulation status and landslides after the earthquake situation carries on the investigation and study, we analysis of the evolution of ancient mud rock flow and modern debris flow formation conditions, using single debris flow evaluation model of debris flow evaluation and forecast the future scale of debris flow. The main results are as follows:(1)Through the old debris flow body to conduct a detailed investigation, from old to new make VII stage. The old debris flow accumulation body IV, VI, VII stage respectively, and new tectonic movement of 200 kaBP, 30-50 kaBP, 10 kaBP corresponding to the Western Sichuan plateau. Lixian County loess, glacier, lake sediments reveale the effects of climate change on debris flow.(2)Through the evolution from historical angle to predict development scale, old debris flow affected by tectonic movement and glacial action obviously. Because of the Zagunao glacier retreat and tectonic movement stability,the debris flow scale will not exceed old debris flow scale. Debris flow will play from the glacial debris flow to rainstorm debris flow.(3) "the 7.6 debris flow" is a low frequency, large, heavy rain gully debris flow, the debris flow development stage is the development period now. Characteristics: the channel length, channel width and white, scouring and silting and or overlay, debris flow in channel deposits. Source of loose solids in the basin is rich, the cumulative proportion of small ditch, source of reserves is still large.(4)to evaluate the debris flow hazard, using the Liu Xilin model of evaluation, evaluation result is the main gully debris flow and 1# ditch, ditch3#, ditch 4# is moderate risk, 6# ditch is high risk.(5)compared to the occurrence of 7.6 debris flow source investigation results and the present debris flow source survey results, through the source estimation method in the prediction of the debris flow scale; comprehensive stormwater method of debris flow scale according to the actual calculation of the future finally obtains to get the prediction scale result: oriented ditch: 5191 million; 1#:1.05 million; 3#:1.335 million; 4#:0.505 million square 6#:1.32 million.