| Lvchun county is located in the south of Yunnan province.It is a typical mountainous county.Located on a thin ridge,the county of Lvchun is banded along the east-west direction,and the building is built along the ridge.Lvchun county urban complex geological structure,stratum lithology in sand slate,easy weathering and softening,gully development,erosion cutting,retrogressive erosion strong,intensive human activities,geological disasters,which seriously restrict the development of Lvchun county economy and society.In recent years,in the face of severe geological disaster threat,from 2008,11 key areas of geological disaster comprehensive control have been carried out gradually,the effect is obvious.However,due to the fragile geological environment and the increasing human engineering activities,the geological disaster in the county area is in the trend of "remarkable control effect and the dynamic development of the disaster situation".Therefore,it is necessary to carry out geological disaster risk assessment in Lvchun County,and the evaluation results can provide the basis for the planning,disaster prevention and disaster reduction of Lvchun county.This paper on the development of Lvchun County District 54 disaster point(43,11 landslide debris flow)to carry out a detailed investigation,analysis of the formation and development of law,city disaster mechanism and influence factors on the basis of the combination of urban geological disaster prevention project of control effect.Based on the qualitative evaluation of the geological disaster risk in Lvchun County,the corresponding evaluation index and evaluation model are selected,and the risk assessment is carried out by using the spatial analysis function of GIS.On the basis of the vulnerability assessment of Lvchun county area,the influence scope and vulnerability assessment of disaster area are combined.The risk assessment results of geological disaster in Lvchun county are obtained by unifying them into the risk evaluation model.The main achievements are as follows:(1)The landslide and debris flow develop in Lvchun County: landslides mainly develope in the South and North Slope of Shanliangzi;debris flow is mainly distributed on the right bank of Guidong river.In the weak rock mass area with slate and chill slate,the range of 30 ~ 40 ° slope,the area of human engineering activity and the debris flow gully,the ditch bank slope belt are the high prone area of landslide disaster..(2)The effect of geological disaster prevention control are eveulated by qualitative and quantitative methods,that is from the three aspects of the implementation and operation,the effectiveness evaluation and the benefit of the control project..The control project effect of24 disaster spots in Lvchun county has been obtained.Except for the individual disaster point,only a simple treatment project having been carried out,the treatment effect is general,and the rest of the treatment projects are better or good.(3)On the basis of the detailed investigation of the landslide and debris flow in Lvchun county,risk qualitative evaluation of development characteristics,stability of the status quo of Lvchun County existing landslide formation mechanism,influencing factors and the degree of harm,and the effect of landslide control project.The weight of the influencing factors of landslide in Lvchun county are determined by quantitative method,and the spatial analysis ability of GIS software is used to superimpose the weight,the zoning map of landslide susceptibility in Lvchun county being obtained.Combined with the qualitative evaluation results of landslide hazard,the risk of landslide in Lvchun county is divided into three areas: moderate risk,low risk and extremely low risk..The moderate risk area is 2.33km2,accounting for 7.57% of the study area;low risk area is 8.73km2,accounting for 28.34%;low risk area is19.74km2,accounting for 64.09%.On the basis of qualitative analysis of the debris flow,Liu Xilin model of the risk assessment of single debris flow gully debris flow is adopt.The main factors: the maximum amount of the debris flow at a time,the frequency of the debris flow,and the secondary factors:the watershed area,the main channel length,the maximum relative height difference of the basin,the cutting density of the basin,and the unstable cave bed ratio are taken to evaluate the risk assessment of the 11 debris flow in Lvchun County.It is concluded that N4,N7,N8 and N10 are low risk areas.N1,N2,N3,N5,N6,N9 and N11 are extremely low risk areas.(4)From the three aspects of society,material and economy,the population,road,land use status,housing construction and GDP are selected,using AHP to get the weight of each index and GIS platform for stacking calculation getting the zoning map of regional landslide vulnerability assessment.And with the previously obtained landslide influence range map superimposed,the final vulnerability distrubited map of the study area are got.The high vulnerability area is 0.388km2,accounting for 1.29% of the study area;moderate is 0.606km2,accounting for 2.01%;low vulnerable area 0.978km2,accounting for 3.26%;the extreme low vulnerability 28.01km2,accounting for 93.43%.Based on the result of the vulnerability assessment,it may be closer to the actual vulnerability if the disaster affected area was considered.In this paper,the landslide areal density is used to indirectly represent the influence range of the landslide and overlaps with the previous regional vulnerability toobtain the final landslide vulnerability map.According to the damage characteristics of debris flow,Liu Xilin model for vulnerability assessment of debris flow is chosen.Combined with the interpreted debris flow basin,the influence range of debris flow accumulation body is determined and vulnerability assessment of debris flow disaster in Lvchun County is completed.N2,N4,N6,N7,N8 and N9 are medium vulnerability.N1,N3,N5,N10 and N11 have low vulnerability.(5)Based on the theory of geological hazard risk assessment and ArcGIS spatial analysis function,the spatial superposition of landslide risk and vulnerability of Lvchun county is analyzed,and the risk of landslide in Lvchun county is divided into three districts:moderate risk zone,Low risk zone and very low risk zone.Medium risk area are 0.746km2,accounting for 3.44% of the study area;low risk area is 2.54km2,accounting for 9.22%;the area of low risk area is 26.64km2,accounting for 86.49%..The risk assessment of debris flow is based on the risk assessment model of single ditch debris flow.The risk and vulnerability of single ditch debris flow are superimposed by GIS spatial analysis,and the risk of debris flow in Lvchun county is obtained.Except for the risk of N3 and N11 is very low,the others are low. |
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