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Abstract
3D Landslide Hazard Mapping using MapObjects
Track: Mining and Geosciences
Author(s): MOWEN XIE, Tetsuro Esaki, Guoyun Zhou, Yashuhiro Mitani
The assessment of landslide instability and risk has become a topic of major interest for both geoscientists and engineering professionals as well as for the community and local administrations in many parts of world. In the recent years, Geographic Information Systems (GIS), with its excellent spatial data process ability, has attracted great attention in natural disasters assessment@too. The stability calculation for landslide assessment can be performed within or outside the GIS. To overcome the data conversion difficult outside of GIS and the difficult of complex algorithms within GIS, here, a GIS component is used in Visual Basic program for assessing the landslide.
In this paper, based on a column based three-dimensional (3D) slope stability analysis model, a new Geographic Information Systems (GIS) grid based 3D deterministic model is developed. Assumed the initial slip as lower part of ellipsoid, the 3D critical slip surface in the 3D slope stability analysis is performed by the means of a minimization of the 3D safety factor by using Monte Carlo random simulation. All the functions for the 3D safety factor have been implemented into a computer program called 3DSLOPEGIS. In this system, the GIS component (MapObjects of Esri) is sued for fulfilling the demanded GIS function, all the slope related GIS data can be managed and analyzed effectively just as the same in the ordinary GIS software. All the data for the 3D slope safety factor calculation are in the form of GIS data (for example, the vector and grid layers), so itfs not necessary to convert the data between GIS data form and the form of other program. At the same time, the complex algorithms and iteration procedures of the 3D problem can be perfectly implemented.
The other important problem for the landslide hazard assessment is the study object, but this topic has not received adequate attention in the literature. Many researchers take the pixel (or grid) as certain study object, just because the grid-based object can be easily gotten and managed. Landslide has closed relation to the geological and geomorphologic aspect of study area and is namely as a Slope instability problem. So in this research, Slope Unit is taken as study object. Slope unit, as basic study object in this study, namely, the portion of land surface that contains a set of ground conditions that differ from the adjacent units, possesses an explicit topographical (break line, stream, aspect and slope) and geological concept. In this study, the hydraulic model tool is employed to draw divided lines for forming slope units. By using hydraulic model tool, the watershed (the size can be determined by user defined) can be gotten from digital elevation model (DEM) data. From the point of topological aspect, the outline of the watershed polygon is just the ridge line. For detecting the valley line, the reverse DEM data is used. By the DEM grid analysis, turn the high DEM value to low value, and turn the low DEM value to high value, then the original valley line can be just turn to ridge line. So by using this reverse DEM data, the valley line can be gotten too by watershed analysis.
The system 3DSLOPEGIS is an independent GIS system for the landslide 3D hazard assessment. All the input data and results are in the form of GIS (vector or raster). Besides the function of mapping landslide hazard, the basic GIS functions such as viewing, legend editing, querying and outputting are implemented in this system too.
MOWEN XIE
Institute of Environmental Systems, Kyushu University
Hakozaki 6-10-1
Higashi Ku , Fukuoka 812-8581
Japan
Phone: :+81-92-642-431
Fax: +81-92-642-3848
E-mail: xie@ies.Kyushu-u.ac.jp
Tetsuro Esaki
Institute of Environmental Systems, Kyushu University
Hakozaki 6-10-1
Higashi Ku , Fukuoka 812-8581
Japan
Guoyun Zhou
Institute of Environmental Systems, Kyushu University
Hakozaki 6-10-1
Higashi Ku , Fukuoka 812-8581
Japan
Yashuhiro Mitani
Institute of Environmental Systems, Kyushu University
Hakozaki 6-10-1
Higashi Ku , Fukuoka 812-8581
Japan