| dc.description.abstract | The Typhoon Morakot brought extreme rainfall and induced numerous landslides in Gaoping catchment in August, 2009. To realize the feature of landslides and the potential problems involved in the landslide susceptibility analysis under an extreme rainfall event, this study uses landslide inventories interpreted from FORMOSA-2 images before and after the Morakot typhoon event. The landslide inventories were checked by examining rectified aerial photographs, high resolution topographic maps, so as to establish an event-based landslide inventory. This study uses rainfall data of the Typhoon Morakot as trigger factor, and uses topographic factors and geological factors as causative factors, and then uses logistic regression as analytical method to establish a susceptibility model. Because this extreme rainfall event induces a large number of deep slides, to identify them carefully and to exclude them from the landslide inventory are necessary. The event-based landslide inventory shows that most landslides locate at moderate slopes（22°~38°） instead of scarp slope. Because the differences of mechanism between shallow landslides and rockfalls, we exclude rockfall region from the shallow landslide susceptibility analysis.
To clarify the issue of landslide susceptibility analysis under an extreme rainfall event, this study compares five different models (model A1, model A2, model A3, model B, and model C). The results show that modle A1 established with traditional method is still suitable, the other models have not shown any advantages. Model A1 shows that AUCs of the success rate curves for hill terrain and for mountainous terrain are 0.830 and 0.721, respectively. It also shows that AUCs of the validation rate curves for hill terrain and for mountainous terrain are 0.790 and 0.729, respectively in the Haitang event. The results are all satisfactory.
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