| Owing to varied terrain, complex geological conditions, frequent tectonic activity, landslides, collapses, debris flow and other geological hazards are widely distributed and high-frequency. And they cause a great threat to social stability, people’s daily life and property, so using advanced technology and new way to carry out investigation and research of geological hazard is particularly important. Remote sensing technology applying in the investigation of geological hazards is macroscopical, fast, accurate and reflects the real situation of geological hazards. So RS has become an important means of geological hazard research. Based on powerful information management and spatial analysis function of GIS technology, we could establish database to store and manage information of geological disasters. With efficiency and accuracy, GIS has been widely used in geological hazard survey, risk assessment, hazard zoning, monitoring, warning and forecasting, emergency command. In recent years, with continuous enrichment of remote sensing data’s source, continuous improvement of spatial resolution and development of GIS visualization technology, the use of remote sensing and three-dimensional GIS technology for geological hazard survey can observe geological hazard and its surrounding terrain fast, accurately. At the same time, we can has multi-angle and all-round view of it. using of remote sensing and three-dimensional GIS not only has incomparable advantages of traditional investigation, but also overcomes the inadequacies of the two-dimensional interpretation of remote sensing. So it has been the hotspot of current geological hazard’s research.Plenty of geological hazards occur in The Three Gorges area of the Yangtze River because of its extremely complex terrain conditions, tectonic movement, coupled with deep valleys and intense rainstorm. Zigui County, the first county in the Three Gorges Reservoir area, is traversed by the Yangtze River across the territory from west to east. Zigui County has great hypsography changes, steep terrain, and development of fault zones, complex tectonic condition, coupled with the construction of the Three Gorges Dam leading to change of certain geological condition. So geological hazards including landslide, collapse, debris flow develop frequently in Zigui County, such as Xintan Landslide, Qianjiangping Landslide and Lianziya Crag. They cause a great threat to local people’s daily life and property. The remote sensing interpretation in the survey of landslides, collapses, debris flow in Zigui County is of great significance for its prevention and mitigation of geological hazard in future.This paper takes Zigui County, Yichang City in Hubei Province as research object. Based on the iTelluro network Figure developed by Dida Information Engineering Co., Ltd. in Wuhan, we use ALOS image, DOM, DEM and other vector data of Zigui County to build a three-dimensional visual platform of remote sensing interpretation, and interpret landslides, collapses, debris flow, and then analysis developmental state and distribution rule of geological hazard. We hope to explore the method and technical route of using of RS and three-dimensional GIS for the survey of geological hazard. The main results of the paper are:(1) Based on three-dimensional visual platform of remote sensing interpretation and using of its contrast function of ALOS and DOM, we establish three-dimensional interpretation marks of landslide, collapse, debris flow in study area to interpret245spot geological hazards, including198spot landslides,37spot collapses,10spot debris flow.(2) Combined with relationship of geological hazards and townships of Zigui County, topography, stratum and lithology, geological structure, rivers, human engineering and economic activity, we obtain the spatial distribution rule of geological hazards:The number of geological hazards in South towns of the Yangtze River is more than of north towns. The threat of geological hazards in south region of the Yangtze River is significantly greater than that in north region. And the number of geological hazards diminishes from both sides of the Yangtze River to the north and south town.The Number of geological hazards decreases with increasing of elevation from the Yangtze River to both sides. They are mainly in the Yangtze River valley and cross-strait hilly areas below500m elevation.200-500m elevation are the most prone to develop landslide, collapse, debris flow.Geological hazards develop mainly in the slope of25～35°. This slope is more susceptible to be under threat by geological hazards. greater threat. The slope more prone to develop landslide, collapse, debris flow is respectively gradient of25～35°,45～55°,35～45°.Geological hazards have occurred in every aspect, and the aspect most prone to develop geological hazards is westward.The stratums which is easy to slip and collapse are Triassic and Jurassic, including second-class strata of Patong group(T2b), and Shaximiao group(J2s). The most landslide-prone strata is Jurassic, and Triassic is the most prone to develop collapse and debris flow. The vast majority of geological hazards are in sedimentary rocks. The reason is related to that Zigui mainly develop sedimentary rocks.lithology easy to slip and collapse have structure with characteristics of the weak base or and interbedded soft-and-hard layers.Zigui syncline, Xiannvshan fault zone, Xinhua fault zone are prone to develop geological hazards.Geological hazards present zonal distribution along the river on both sides, and both sides of the Yangtze River are of the most geological hazards, followed by Qinggan river, secondary tributary of the Yangtze River. As distribution of the Yangtze River and its tributaries is like centipede, distribution of geological hazards appears to be mainly EW zonal distribution pattern, and supplemented by SN on the whole.Geological hazards are prone to develop in areas related to human engineering and economic activities including towns, residents,roads and farmland reclamation area. Most of geological hazards are located along the roads.The results show that:Zigui County develops landslides, collapses, debris flow seriously, especially landslides. Spatial distribution pattern of geological hazards is greatly affected by topography, lithology, geological structure, river system, human engineering and economic activity. And topography, lithology, geological structure is internal factors. |
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