| dc.description.abstract | This study uses slope unit as mapping unit for landslide susceptibility assessment. The delineation of slope unit must consider topographic meaning. In the past, most of slope units applied to landslide susceptibility assessment were delineated by combining the watershed by DEM and the watershed by reverse DEM. Further editing and merging work is usually required and it needs much manual work. The process is times consuming, and containing too much subjective comment. This study follows Chien(2011) using an object-oriented analysis method to automatically generate slope unit. I have modified the processes of slope unit delineation and checked the slope unit quality by statistical methods. In the study area, Shihmen Reservoir catchment area, we first classified the flat area, and using sub-catchment for the former limits. Finally, I use slope aspect as an important component in the object-oriented analysis software, Definiens. According to the weight and the heterogeneity index of image layer, slope units are delineated. Then we calculated standard deviation of slope aspects and normal vectors in each slope unit. I choose two of sub-catchment in the study area for comparison and discussion. The result shows that the delineation methods of our study can get a better result.
Then we use the slope unit for landslide susceptibility assessment. Standard deviation of elevation, steep slope ratio, wetness index, slope roughness, the maximum rainfall intensity, and total rainfall of Aere typhoon were adopted in a logistic regression analysis. Because slope units belonging to landslide group or non-landslide group had no conclusive judgment previously, so I will choose different landslide area ratio of slope unit to determine the slope units belong to which group. It reveals that a 5% landslide area ratio of slope unit is good for the threshold. The result shows success rate of the model is fairly good with an AUC of 0.786. | en_US |