GIS COMPONENT BASED 3D LANDSLIDE HAZARD ASSESSMENT SYSTEM：3DSLOPEGIS

In this paper ,based on a new Geographic Information System(GIS) grid-based three-dimensional (3D) deterministic model and taken the slope unit as the study object ,the landslide hazard is mapped by the index of the 3D safety factor ,Compared with the one-dimensional(1D) model of infinite slope,which is now widely used for deterministic model based landslide hazard assessment in GIS,the GIS grid-based 3D model is more acceptable and is more adapt-able for three-dimensional landslide.Assuming the initial slip as the lower part of an ellipsoid ,the 3D critical slip surface in the 3D slper stability analysis is obtained by means of a minimization of the 3D safety factor using the Monte Carlo random simulation.Using a hydraulic model tool for the watershed analysis in GIS,an automatic process has been devel-oped for identifying the slope unit from digital elevation model(DEM)data,Compared with the grid-based landslide hazard mapping method ,the slope unit possesses clear topograhical meaning,so its results are more credible,All the calcula-tions are implemented by a computational program,3DSlopeGIS,in which a GIS component s used for fulfilling the GIS spatial analysis function.and all the data for the 3D slope safety factor calculation are in the from of GIS data (the vector and the grid layers).Because of all these merits of the GIS-based 3D landslide hazard mapping method,the complex algo-rithms and iteration procedures of the 3D problem can also be perfectly implemented.