Study On Landslide Hazard Zonation Based On GIS

Lanzhou is located in the narrow valley areas of the Yellow River, in the western of the Longxi Loess Plateau. The topography of the area is greatly undulate, and gully freely, complex geological structure, strong new tectonic movement, low covered with a thick layer of loose loess, under which widely distributed weak layer of rock. These special landform, lithology and tectonic conditions make the extremely fragile geological environment, combined with some unique environmental factors:the concentrated rainfall, sparse vegetation, and the surrounding area is seismically active, and thus since the ancient times, Lanzhou is the geological disasters areas.Landslides, avalanches, landslides are the main types of geological disasters in the city of Lanzhou, especially the landslide hazard is the most frequent and hardest hit. So a specialized research on the key issues of the landslide hazard based on the assessment of regional geological hazard, will help us to recognise the development and the activity rule of geological disasters in Lanzhou from a deeper level, and will provide a more solid scientific basis for the formulation of disaster prevention and reduction. Through the investigation and analysis of geological disasters in Lanzhou, collected topography and geomorphology, geological structure, rock type and so on related information of the study area, to understand the predecessors of GIS in geological hazard assessment and the present zoning, to identify the distribution, the type and the characteristic of landslides, and to analyse the landslide conditions of topography,geological structure,rock type,meteorological characteristics, hydrological characteristics, vegetation characteristics and other factors. Choose the diagram of1:50000DEM for research, and through the DEM map data processing of study area, extract the thematic layers, and analyze it. The application of GIS technology to extract hazard statistics, through the statistics and the superposition space analysis function, according to the study of the development of landslide disaster of disasters-causing factors in the study area, combined with the theories and models of multivariate analysis of the instability index, to obtain the relative weight of disasters-causing factors. By using GIS space analysis functions, obtained the landslide risk distribution map of Lanzhou, and divided it. Use of the analytical method of ROC curve to test the predictive model, get a higher accuracy of the test results, see that the analytical methods of instability index of multivariate can be applied to the city of Lanzhou, for the landslide risk assessment and the regionalization, and with a certain research value and practical value.The paper will divide the risk of landslide in the city of Lanzhou into four types:areas of high risk, areas of risk, areas of low risk and areas of less risk, and make a summary of the evaluation, to provide a solid scientific advice and basis for the formulation of disaster prevention and reduction in the study area.