Distributed probability of slope failure in Thailand under climate change

Landslides are more widespread compared to any other geological hazards in Thailand. The steep slope and high elevation areas have more potential for landslide hazards. However, weather extremes, particularly extreme rainfall, play a major role in the occurrence of landslides in Thailand. The objective of the present study is to analyze the changes in the probability of landslide occurrences in Thailand due to climate change. For this purpose, probabilistic landslide hazard maps for extreme rainfall values for 5-, 10-, 50-, and 100-year return periods are developed for historical and future climatic conditions, derived from 10 global climate models (GCMs) under two representative concentration pathway (RCP) scenarios, namely, RCP 4.5 and RCP 8.5. The results reveal that the 5-year return period extreme rainfall amount will reach 200 mm/month in the eastern and southern provinces for RCP 4.5 and the northwestern, eastern, and southern provinces for RCP 8.5. The increase in extreme rainfall will cause a sharp increase in the landslide probability in Thailand, except in low altitude regions. The probability of 100-year return period landslide will increase by 90% in 40% and 80% of the areas in Thailand under RCP 4.5 and RCP 8.5, respectively. It is expected that the landslide hazard maps developed in this study will help policy makers take necessary measures to mitigate increasing landslide events due to climate change.