| Earthquakes disasters occur frequently in China. China is one of the most intenseseismic activity and the most serious earthquake damaged national in the world.5.12Wenchuan Earthquake-induced collapses and a large number of landslides and othergeological disasters. It is estimated that the earthquake disastertriggered landslidesand collapses have50,000or more, nearly a thousand ofpotential debris flow, andposes a direct threat to the safety of the people of disaster risks at the point of morethan12,000, its wide distribution, the type of complex, massive destruction, rare inthe world.Earthquake led to a large number of mountain crack, causing a largeaccumulation of loose body, the formation ofpotentially unstable slopes, highly covert,constitute hazards, it is difficult to estimate the number.These potentially unstableslopes, under certain conditions will induce sudden debris flows, the new settlementsof people’s lives and property as a major threat. Therefore, use of new techniques andmethods to quickly identify the hardest hit by the unexpected distribution of debrisflow hazards and trait characteristics,to take the risk of zoning and early warning andforecasting measures,there are important scientific significance and practical value.In this paper as Wenchuan County of Minjiang River upper reaches of a studyarea, and most areas of earthquake damage–Yingxiu to the Tiger Mouth area for theexperimental area, in the full analysis on the basis of previous data, using3Stechnology,the multi-scale multi-source high-precision DEM and remote sensingimage as data source to calculate theentropy of the study area watershed topographyinformation,extracted information on geological disasters.combined with geological,geographical, hydrological, meteorological information, by studying geologicalhazard information of remote sensing and digital image processing and interpretationoffield survey verification,identified the characteristics of the study area and geological disaster spatial distribution of traits,on this basis,using a variety of methodsfor the study area for debris flow potential risk of sudden and Evaluation Division.Thesis research content and made innovations in the following areas:(1) Give full play to the characteristics of RS,GIS&GPS technology, use ofearthquake-precision, multi-type, multi-temporalremote sensing images, throughremote sensing image processing and information extraction of geologicaldisasters,combined with site survey,detailed interpretation of the importance of thestudy area of the geological hazard information.Interpretation of the image area of414.25km2,extract/interpret the53landslides,collapses1575, geological disasterarea76.58km2.Geological disasters in the study area and spatial distribution of traitscharacteristic features generally been identified.(2) Study the use of5.12high-precision earthquake UAV remote sensing images,by all-digital photogrammetry to extract high-precision DEM after the earthquake.The DEM used in the study area after the earthquake,debris flow hazard assessment inthe terrain,topography and other analysis.using The power spatial analysiscapabilities of GIS to extract the study area watershed, slope, elevation and otherimportant information, in particular, use of this high-precision earthquake extractedDEM,produced geological interpretation of remote sensing images three-dimensionalvisualization and analysis of series of dynamic images,provide a viable technology forextraction of geological disasters and on-site investigation.Practice has proved that theproduction target of remote sensing images of3D dynamic observation ofgeologicaldisasters can improve the accuracy of interpretation,benefit from the globalmacro-and micro-local study of geological hazards on individual and group propertycharacteristics and spatial distribution analysis,draw conclusions consistent with theactua.(3) Studies using a variety of different levels of regional and debris flow hazardassessment theory and methods.Based on basin-scale debris flow risk assessment incatchment threshold respectively200,000and300,000and400,000is divided into thevalley basin debris flow hazard assessment,according to different scales of the studyarea into sub-basins and calculate the landscape entropy.Evaluation of the sub-basinas a unit, used AHP to determine the weight.Using the elevation difference, terrainslope,lithology, earthquake intensity, topography information entropy, the maximumdaily rainfall,vegetation cover,11evaluation factors of the study area for debris flowrisk zoning and evaluation. The risk of landslides in Wenchuan county is divided intofive-level. The results show that, along the Minjiang River and the main proximal sudden debris flows extremely dangerous, especially of ginkgo Township andYingxiu town and other areas that merit more attention.(4) In the earthquake zone Yingxiu-Tiger Mouth potential sudden debris flowhazard zonation Research,Use of fuzzy comprehensive evaluation method based onthe debris flow hazard zonation and evaluation theoryand methods,use thehigh-precision DEM after the earthquake,the experimental unit is divided into31and67sub-basins,Debris flow hazard assessment for debris flow scale as the mainfactor,Sub-basin area,elevation difference, the average slope, the cumulative amountof convergence,basin cut density,material source area, flat material source area,mainchannel length, the proportion of unstable gully, gullylongitudinal fall, landscapeinformation entropy such as other factors,established evaluation factors set, with graysystem and fuzzy mathematics ideas, use of gray correlation method to determine theweights of evaluation factors,use fuzzy comprehensive evaluation method for theexperimental area of the potential for debris flow risk zonin.Research results to thisarea of the risk of sudden debris flow warning and forecast provide a scientific basis. |
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