Assessment of Possible Landslide Susceptibility Under Climate Change: A Case in the Chishan River Watershed in Southwestern Taiwan

This study investigated the future spatiotemporal distribution of landslide susceptibility in the Chishan river watershed (CRW) in southwestern Taiwan under four future climate change scenarios. On the basis of 10 landslide-related factors, landslide susceptibility models were constructed using the frequency ratio method and logistic regression method, and the model with better performance was selected for subsequent analysis. This study estimated past (2000–2023) and future (2024–2100) daily CRW rainfall values with return periods of 5, 10, 25, 50, 100, and 200 years. Daily rainfall is expected to increase considerably in the mid-future under the Shared Socioeconomic Pathway (SSP) 3-7.0 scenario and in the far future under the SSP 1-2.6, SSP 2-4.5, SSP 3-7.0, and SSP 5-8.5 scenarios. Under these four scenarios, daily rainfall with a return period of 50–100 years in the far future is expected to exceed the daily rainfall in the CRW during Typhoon Morakot (917.8 mm) in 2009. The intensity and frequency of extreme rainfall events in the CRW are expected to increase in the far future under climate change. Finally, areas with high landslide susceptibility are expected to be distributed in the upstream regions of the CRW.