| Since the wenchuan earthquake in 2008,the secondary geological disasters in the earthquake-stricken areas are still very active,especially the debris flow disaster occurred frequently,the scale is huge,and the impact period is long time.It has been more than 11 years from the earthquake,but the post earthquake geological disaster has not recovered to the pre-earthquake level,and landslide are resurrected,expanded,even turned into a solid loose material source to join the activities of debris flow under the action of heavy rainfall and other external environments.At present,the post-seismic effects of geological disasters are still very obvious,but the continuous study on the evolution of landslide debris flow disasters after the earthquake is still insufficient,there is a lack of quantitative analysis of geological disasters in different periods and the analysis of evolutionary mechanism,and the study on the quantitative erosion and transport characteristics of seismic avalanche material source is still in a weak link.This paper is mainly aimed at wenchuan earthquake landslides erosion transportation and evolution characteristics of the problem,unmanned aerial vehicle(UAV)digital photogrammetry technology was used to study the earthquake landslides erosion Characteristics,combination of multiphase high resolution remote sensing image of debris flow in the basin in the study area of landslide and other content source for interpretation,explore the time and space distribution characteristics of earthquake debris flow provenance,at the same time using multiphase typical remote sensing image study landslides evolution rule,and apply Geo Flow-SPH numerical simulation method,on the erosion rule and accumulation characteristics of debris flow were studied.The main conclusions of this paper are as follows:(1)Investigation and statistics were conducted on typical landslide accumulation bodies in the research area,and the basic characteristics and erosion characteristics of landslide bodies were described.After the earthquake,most of the landslides are composed of loose materials with exposed surface.Under the action of rainfall and runoff,the material of the accumulation bodies is transported into the debris flow gully by scouring and erosion,providing sufficient material source for the debris flow starting.The erosion types of landslides in the study area include rain splash erosion,sheet erosion and gully erosion.Gully erosion is the main mode transportation of loose material after earthquake.(2)UAV remote sensing technology was applied to the landslides quantitative erosion research.Based on the aerial survey data of uav acquired before and after the rainy season,the erosion sediment yield of landslide body was quantitatively studied on the basis of DEM data of two phases on the Arc GIS platform.The single factor analysis was carried out by the control variable method,and the correlated landslide area,slope and surface runoff were selected as the influencing factors of the erosion amount.Through regression analysis,the quantitative erosion model of post-earthquake landslide was constructed.(3)In the period 2008-2018 years,which based on the data of remote sensing image to the study of the six goals in the small watershed in the landslides manual interpretation,based on the space-time distribution of debris source were analyzed,found that after the earthquake landslides,developmental advantage of pushing the height from 1300-1600 m to 1900-2200 m,the landslides were concentrated in the slope range of 30-50 degree,E,SE and S dominant slope collapse area remain relatively large,which were the dominant slope direction for the development of the landslides.The landslide area was negatively correlated with the distance from the main river,when more than 800 m from the river distance,The river's control of landslide activity is reduceed.(4)Based on the multi-temporal remote sensing image and combined with the debris flow occurrence event,From the historical image of the whole and part of two aspects,analyzed landslides transport and supply evolution characteristics by debris flow event.The results show that there will be a process of transition from loose to locally stable to basically stable.During this period,there is a medium and long-term transport effect in the loose material sources in the basin,which will occur continuously for a period of time,until the ecological environment in the valley returns to a stable state.(5)The geoflow-sph numerical simulation software was used to simulate the mass debris flow on "8.13" in 2010 in yingxiu town by selecting 6 debris flow gully in yingxiu area as the prototype.The erosion along the debris flow was considered in the numerical simulation.The simulation results were verified to be accurate with the actual situation of debris flow events.The results show that the method can be used to predict the debris flow activities after the earthquake reasonably,which provides a scientific basis for the early warning and prediction of the debris flow disaster and the engineering management in wenchuan earthquake area. |
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