Vulnerability Assessment Of B Uildings To Debris Flow In Mountain Area Of The Upper Reaches Of Min River

The region of the upper reaches of Min River,which is made of Wenchuan,Heishui,Lixian,Maoxian,Songpan and Dujiangyan successively,gain a great fame over the world for its typical mountain landscape.Continuous geological activities,engineering,farming,grazing and settling result in the fragile environment of that area.Thousands of thousands losses of financial have been causing by the hazards events triggered by the extremely unstable environment years by years.The buildings,as the most important property,are always being threatened by the hazards events seriously.So,this thesis focus on the assessment of the vulnerability of buildings in the upper reaches of Min River using an integrated method including geography,geology,RS and numerical simulation,and draw the conclusions as follows:The stream net of the upper Min River is extracted by using the hydrological analysis module of ArcGIS based on the DEM data of this region featured by a resolution of 15m.Then,this thesis works out the locations of the debris flows in this area by watershed analysis,and get the latitude and longitude of all the debris flows.After that,the dataset are verified by ours field investigation,Google Earth navigation and the historical statistics.There are 249 debris flows in the upper reaches of Min River in total.There are 34 debris flows in Wenchuan within 34 counties,53 in Heishui within 53 counties,38 in Lixian within 37 counties,70 in Maoxian within 67 counties,while 54 in Songpan within 54 counties.This paper tried to cluster those debris flows to simplify the vulnerability assessment of buildings in this region by the watershed form,the area,and the slope,but failed to find that its vulnerability differs for the same buildings in the different debris flows.It's necessary to make a specific analysis in a specific condition.This paper extract the range of the buildings of this area in the 1995,2005 and 2015 by the NDVI(normalized differential vegetation index)using the ENVI software,and then build the shape files of the buildings under the assistance of the topographic map by the ArcGIS.It's 200994 shape files in total which shares 85%of the buildings in the upper reaches of Min River.The statics shows that the buildings area is among 50 m2 and 200 m2.the large buildings stands on the center of economic and transportation of this region,whose percent less than 10%.We can also know that some of the buildings are residence,some commercial,some public service,while some schools.And the residence buildings take the most shares,while the schools least.There is an interrelation between the materials and the constructions,the buildings with a Frame structures are always made of bricks and steel,while buildings with a masonry structure are made of bricks.Furthmore,the distance of buildings differs from 50m to 1000m,it is the compromise made by the residents while choosing the places to build the buildings to the surroundings.All the buildings of this region risk a high vulnerability,the highest vulnerability and the high vulnerability take 28 percent and 53 percent respectively.We compare the buildings vulnerability within the same county,and find that the vulnerability of the Dujiangyan County differs sharply,while it is similar in the Lixian County.This thesis draw a conclusion that the center of economic and transportation,the lager buildings and the buildings standing close to debris flows hold a higher vulnerability.The last chapter of this paper,we evaluate the buildings vulnerability of the Qipan gully using the SOM method based on girds.The commercial buildings vulnerability ranks the highest,and the residence buildings fellow closely.The results also shows that the vulnerability of different parts of the same building differs,take the inner space and the wall as an example,the vulnerability of the inner space is higher than that of the wall for the different materials.The buildings is the most vulnerable property in the upper Min River region,so it is reasonable and necessary to assessment the vulnerability of it.And the results can be a policy decision support for the governor.