三峡库区地质灾害空间评价预警研究

Assessment and early warning on geo-hazards in the Three Gorges Reservoir region of Changjiang River

通过全面野外调查(比例尺1∶100,000),填表登录了三峡库区(19县(区),54175km2)地质灾害点5706处,其中,滑坡3830处、不稳定斜坡1107处、崩塌549处、泥石流90处、地面塌陷85处、地裂缝45处。采用1∶250,000数字化地形底图,通过编制三峡库区工程地质图层,建立了基于MapGIS的三峡库区地质灾害空间数据库和分层图形库。在研究了三峡库区地质灾害分布与地形(高程、坡度)、水系、植被、工程地质岩组、地质构造形迹、斜坡类型、降雨量分布和地震活动等的统计关系基础上,筛选提取了地质灾害空间评价预警研究的发育因子(响应因子)、基础因子、诱发因子和易损因子体系。划分了三峡库区干、支流库岸的斜坡结构类型,预测建立了未来三峡水库在145～175m水位变动期水库库岸斜坡可能出现冲刷—坍塌、整体滑移、溶蚀垮塌和侵蚀—剥蚀等4种类型变形失稳模式。采用2 5km×2 5km(图面1cm×1cm)的网格剖分整个区域,共形成9309个网格。基于区域地质灾害评价预警的递进分析理论与方法(AMFP),分别计算了三峡库区地质灾害"发育度"、"潜势度"、"危险度"和"危害度"(简称"四度")。采用图斑合并方法分别编制了相应的"四度"区划图。根据"四度"区划结果,分别提出了三峡库区地质灾害监测预警与防治区划和地质环境开发利用的对策。

It has been 40 years since the surveying, monitoring, studying and controlling for geo-hazards started in the Three Gorges of Changjiang River, and contributed more with the construction of the Three Gorge projects and the protection in ecological geo-environment of the region. However, there are some problems in those works in late studies and migration engineering constructions, such as, there was little guidance directly in development and protection of the geological environment, and then, there were much repeated works or the lower level of study. Geo-hazards field investigation of Three Gorges Reservoir region has been completed overall in scale 1∶100,000 for two years since 1999, which consists of 19 counties (54175km^2). Six types of geo-hazards of the total 5706, including landslips(3830), unstable slopes(1107), breakdowns(549), debris-flows (90), collapses(85)and ground fissures(45), are checked in table and inputted spatial database. Information system (GGIS)of geo-hazards is set up by mapping engineering geological map layers of Three Gorges Reservoir region utilizing digital terrain map in scale 1∶250?000. For researching on the interrelation between geo-hazard distribution and all related factors, e.g. terrain altitude, height difference, river system, vegetation, engineering geological lithological suites, anticline, faults structures, slope types, rainfall distribution and seismic activity etc., authors screen out assessment factor system including geo-hazard distribution characteristics, geological environments, induced factors and vulnerable aspect such as human and wealth of society of Three Gorges Reservoir region. Four types of bank slope deformation model, erosion fall-down, whole slipping, karst collapse and weather-denudation, are classified by to study on rock and soil structure of bank slopes in Changjiang River and its branches when water level of Three Gorges Reservoir would change time after time between 145～175m. The Three Gorges Region of Changjiang River is meshed to form 9309 squared grids in 2.5km×2.5km (1cm×1cm in map).Using 'analysis method by four parameters' forward step by step for short AMFP, calculates respectively geo-hazards 'distribution parameter', 'potentiality parameter', 'dangerous parameter' and 'risk or harmfulness parameter' of every grid based on the GIS, and works out 'four parameters' zoning maps by to merge borderings on squared grids with equal or similar parameters. Finally, the strategy and plan are put forward to mitigate geo-hazards in Three Gorges Reservoir region including the people observation and special monitoring network for early warning, policy for emergency events and important geo-hazards control projects.