Application On Investigation And Evaluation Of Geohazard By High-precision Satellite Remote Sensing Technique

Remote sensing technique is extremely essential to investigation and evaluation of geohazard,owing to increasingly serious geohazard and limitation of time to emergency disaster relief. It can runthrough the entire process, which includes in turn investigation and evaluation of geohazard, monitoringand early warning, disaster evaluation and control. So it is the inevitable tendency of modern high-techdevelopment. Although the application of remote sensing technique to investigation and evaluation ofareal geohazard had made lots of successful experiences, most of them were only restricted to theextraction of geohazard zone, macroscopical evaluation, and so on. At present, Geohazard analysis ofsolo zone mostly relies on aerial photographs. Application of high-precision satellite remote sensingtechnique to accurate interpretation and evaluation of geohazard is very limited. Especially, its sucessfulapplicatons are very less to geohazard monitoring. Based on many factual examples, including Xuanhanlandslide, debris flow near the dam of Luding hydropower station, bank collapse of Three Gorges andproposed Lixiang railway, following research findings were attained through systematical research work.(1) Relative systematical method system was preliminarily established for the application ofhigh-precision satellite remote sensing technique to geohazard of collapse, landslide and debris flow.Identification mark and interpretation method of remote sensing for geohazard were revised anddeveloped according to the genesis and activity characteristics of geohazard (collapse, landslide anddebris flow). Advantage and limitation of remote sensing technique in geohazard research field wereexplained. Application of remote sensing technique to geohazard investigation, evalution, emergencydisaster relief and remedy designation of engineering was illustrated by examples.(2) Key remote sensing technique for geohazard (collapse, landslide and debris flow) was explainedin detailes. Discussion was made in this paper for selection of data source, image spectrum correction,image geometry correction, image ortho-rectification, 3D model establishment of remote sensing andradar interference technique. Different processing methods of remote image were put forward fordifferent study object, study stage and study degree of geohazard.(3) Some popular image fusion techniques at present were illustrated with factual examples ofimages. According to the characteristics that the extraction of deformation and failure trail was veryimportant for the study of geohazard, resolution fusion technique that was based on specific volume wasput forward for remote sensing interpretation. Consequently, image texture features could be enhancedwith this technique. Resolution fusion technique that was based on GramSchmidt transform or principalcomponent transform was used when image was made, which enabled spectral characteristics ofmulti-spectral image to be preserved to the maximum extent. At the same time, a new technique of colortransform was put forward for SPOT image.(4) Lots of high-precision satellite remote sensing photographs were collected about geohazard(collapse, landslide and debris flow). Plane shape, internal structure and activity characteristics ofgeohazard were deeply studied based on previous results. Interpretation mark and method of remote image were supplied and developed. A new estimation method of landslide volume was put forward.According to two examples of Baiyian landslide and debris flow ditch near the dam of Ludinghydropower station, extraction technique of geohazard detailed characteristics from QuickBird imageand its quantitative evaluation method were put forward.(5) Based on the project of remote sensing interpretation to railway engineering geology conditionsfrom Lijiang to Xianggelila, using the combination between aerial photographs and SPOT images whoseresolution was 5m after fusion, inducing hazard conditions in study zone and development conditions ofgeohazard (collapse, landslide and debris flow) were extracted. Distribution characteristics of geohazardalong this proposed railway were appraised. Based on the advantage of remote sensing technique to theextraction of geohazard evaluation index, reliable evalution index was established, using simplemathematics evalution model as following. GM=(multiply from i=1 to n P_i)^1/nClosely combining engineering geology conditions and formation mechanism of geohazarddevelopment (collapse, landslide), regional hazard evaluation was made to geohazard (collapse,landslide) of study zone. Comparative analysis of the results indicated that the evaluation model wasrelatively reliable. Analysis results kept a strong agreement with the factual development conditions ofgeohazard, so it had some practical value.(6) By virtue of IKNOS and QuickBird satellite photographs with multi-time phase and highresolution, comparative analysis of characteristics was made for Xuanhan landslide during its differentstage, that is, before landslide deformation, after landslide deformation and after remedy. Formingconditions, developing characteristics, deformation and failure mark and main hazard conditions wereanalysed. High precision 3D remote sensing model of landslide zone was established, which providedlots of reference data to landslide remedy.(7) It was the first time that the collapse of reservior bank was monitored by virtue of QuickBirdsatellite photographs of multi-time phase. Remote sensing technique and method system was establishedto monitor the collapse of bank. Remote sensing interpretation of Three Gorges reservior zone wasdeveloped. Comparative study of QuickBird satellite remote sensing photographs had been made twicefor part of Three Gorges reservior zone. Distribution scope of bank collapse was determined for 139mwater level, which arose from ponding of above one year. Feasibility and accuracy of application of highprecision satellite remote sensing to monitoring of bank collaspe scope were analysed. Lots of referencedata were provided for the forecast of bank collaspe scope at 156m and 175m water level in ThreeGorges reservior.