Abstract
Landslide susceptibility assessment is crucial for mitigating and preventing landslide disasters. Most landslide susceptibility studies have focused on creating landslide susceptibility models for specific rainfall or earthquake events, but landslide susceptibility in the years after specific events are also valuable for further discussion, especially after extreme rainfall events. This research provides a new method to draw an annual landslide susceptibility map in the 5 years after Typhoon Morakot (2009) in the Chishan River watershed in Taiwan. This research establishes four landslide susceptibility models by using four methods and 12 landslide-related factors and selects the model with the optimum performance. This research analyzes landslide evolution in the 5 years after Typhoon Morakot and estimates the average landslide area different ratio (LAD) in upstream, midstream, and downstream of the Chishan River watershed. We combine landslide susceptibility with the model with the highest performance and average annual LAD to draw an annual landslide susceptibility map, and its mean correct ratio ranges from 62.5% to 73.8%.
Highlights
Deaths and economic losses due to natural disasters have drastically increased in Taiwan over the past two decades, especially after the 1999 Chichi earthquake [1]
Note: PLCR and PNLCR refer to the predicted landslide correct ratio and the predicted non-landslide correct ratio, respectively, PLWR and PNLWR refer to the predicted landslide wrong ratio and predicted non-landslide wrong ratio, respectively, and MCR and MWR refer to the mean correct ratio and mean wrong ratio, respectively
Numerous landslides were induced by Typhoon Morakot in the Chishan River watershed
Summary
Deaths and economic losses due to natural disasters have drastically increased in Taiwan over the past two decades, especially after the 1999 Chichi earthquake [1]. In Taiwan, landslides and debris flows are the major causes of serious rainfall-induced disasters. The death toll due to Typhoon Morokot in 2009 was around 703, and the death toil due to the associated landslides and debris flow disasters was over 500, including 465 deaths caused by the Xiaolin deep landslide [2]. The number and intensity of the heavy rainfall events are expected to increase in the future in Taiwan [3], and the occurrences of landslides and debris flows over the decade are expected to increase. Landslide susceptibility assessment models can be created based on heuristic, deterministic, and statistical approaches. Among these approaches, statistical methods are the most popular because of the development of geographic information systems and remote sensing techniques. The prediction accuracy of most statistical landslide susceptibility models can exceed 70% [4,5,6,7]
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