Research On Bank Collapse In Zhongxian County In The Three Gorges Reservoir Area Based On GIS

Reservoir bank collapse by the agency of the water immersion, shock waves, currents erosion, the alternating of wet and dry role, so that the reservoir shoreline retreat, and within reservoir neighboring wave area form shoal, the phenomenon was known as reservoir collapse, the factors prompted the phenomenon was defined as the bank collapse role. Savarenski, Fiodor Petrovich, the academician of USSR-Russia academy of sciences, put forward the problem of reservoir bank collapse in 1935. Henceforward, the problem is recognized further. Many scholars have conducted a lot of research on the bank collapse mechanism, the inducing factors, bank collapse width forecast methods and the bank collapse numerical model and has achieved some important research achievement. In recent decades, many bank collapse width forecast methods have been developed. Previous researchers have shown that each method has its own merits. For the bank collapse do great threat to the life and property of the coast people and damage to the water resources facilities for the accession of the silt, and many nations defray abundant financial revenue to deal with the bank collapse annually. Therefore, many engineers and scientists is attaching importance to that all along.The Yangtze Gorges Reservoir is a long and narrow channel. A lot of the existed landslide will be reactivated for the water storage and operation of the hydraulic junction project. At the same time, the new bank collapses and landslides can be induced and the river will be blocked up, merchant shipping is discontinued. The surges produced by the landslides and bank collapses endanger the projects, directly destroy facilities. For the minimum of the loss caused by bank collapse and the guarantee of the safety of the local people's life and properties in reservoir area, the significance of the study on bank collapse is great.Application of GIS with the study of geological disasters at home and abroad has done a lot of work. From 1980s, the application of GIS technology includes the data management, multi-source data sets digital input and graphics output, DTM and DEM model use, the integration of GIS and disaster evaluation model analysis of the expansion of GIS, Decision Support System (DSS) integration and Web-GIS, the development of the in-depth application is progressive. However, the research of bank collapse based on the GIS, especially 3D GIS technology is rarely. The thesis relies on the item of the Ministry of Land and Resources P.R.C, the research on the geologic condition of Three Gorges reservoir area(Kai County, Zhong County, Shizhu, Fengdu, Wulong, Fuling, Changshou), the code is【2003】14-1-3 ,3L1040334424.The dissertation researched on the bank slopes in Zhongxian County. The existed bank collapse and geologic condition induce bank collapse were investigated in detail. After the field datum are analyzed, the factors influencing bank collapse are discussed, such as hydro geological condition, terrain and landform, the physical makeup and structural feature of the bank slope and human activities. And the influence of is the most outstanding. The bank slopes in reservoir area are classified according to the physical makeup of the bank slope, attitude of rocks, hardness degree of rock and stretch of the river. As a whole, there are 15 sorts (Fig.2-1). The main geology phenomena (gravity deformation, bank collapse, landslides, calcareous shell, and so on) developed in the bank slopes and geological properties of every bank slope are generalized. And by the means of SQLite database engine, the Zhongxian forecast parameters of the bank collapse were input the database, and the data was associated with every bank topographic map. The program was produced by the use of VC procedures language. In the process of the program, the reservoir banks collapse monitoring spots with the redeployment of topographical maps, which included in the bank collapse monitoring and forecast its forecast reading of GIS information, can be automatically searched, and identify various bank collapse types of every point of the bank, and then choose the collapse forecasting methods. At last, the bank collapse forecast width and height are calculated, the specific results table 3-4,3-5,3-6. At the same time, the forecasting parameters are analyzed, that offers reliable foundation for the future research of bank collapse forecasting on the region.At present, 3D-GIS is the hotspots of the region of the research on the GIS. The 3D-GIS definition applied on the bank collapse is present by the deeply analysis of the definition and present situation of 3D-GIS: the 3D-GIS was applied in bank collapse research areas. In the system of 3D-GIS the terrain data will be input, storage, edited and form three-dimensional terrain modeling. This model forma realistic simulation of three-dimensional topographical map through a 3D display means. In this simulated map, bank collapse of spatial analysis and simulation are processed, when it is necessary to form decision support analysis of the computer system, and the system can provide decision support of the relocation of migrants from the reservoir area and the collapse treatment. Among the 5 modern 3D terrain models (digital elevation model, digital terrain model, digital ground model, VR- digital ground model, VR-GIS model) the digital terrain model(DTM) is used in common. The DTM involved on the thesis is generated by mapping the texture on the digital elevation model (DEM), and the texture is produced according to the landform and terrain properties. The modeling methods of the present 3D-DEM include triangulated irregular network (TIN) and grid. Contrast to the two modeling methods the TIN is more accurate, and the method of Delaunay TIN is more applicable than the other one. The program of Delaunay Tin based on contour was done by the means of WINDOWS XP and VC 6.0. To make the present terrain be reflected to the great degree in the 3D-DEM, the facture of the texture was discussed. And the texture of Huanghuacheng bank was accomplished by the software of Photoshop based on the CAD map. 3D GIS terrain model with OpenGL display technology were integrated, a complete 3D GIS bank collapse simulation system was developed. In the bank collapse GIS the reservoir water level to rise and the corresponding changes in elevation were demonstrated into the dynamic process. And the system provide dynamic 3D visual display graphics and make the shift from data to the three-dimensional graphics, more intuitive and three-dimensional, more conducive to the understanding and management of decision makers. So the 3D-GIS was applied on the research of the bank collapse successfully, that is an innovation.Thus it can be seen that the theories of the bank collapse were investigated deeply by the analysis of the detail field data, and by the means of computer programming the 3D-GIS and OpenGL were applied on the study of the bank collapse. To some degree both the contents and achievement are innovative.