Taiwan has amassed a comprehensive inventory of landslides that have occurred in the region. These inventories can be used to calculate annual landslide ratios and investigate how landslide distributions have evolved in each basin. The present study examined 20-year landslide ratios across 45 basins with high landslide concentrations and identified four distinct evolution patterns: declining, event-affected, Morakot-affected, and fluctuating, with each closely tied to geographic location. Basins in southern and southeastern Taiwan were severely affected by typhoon Morakot in 2009, and most landslide ratios in these areas have not fully returned to their pre-Morakot values. Further analysis of yearly landslide ratios post-typhoon revealed recovery times ranging from 10 to 90 years, with the time influenced by each basin’s conditions. In the initial 5 years post-typhoon, recovery levels were unstable, with most
basins regaining only 50% of their ratios. The following 15 years represented a transitional phase, during which most
basins recovered 70%–90%. After 15 years, basins are expected to enter a stable declining phase. Future typhoons of similar magnitude to Morakot will likely have comparable long-term effects, affecting basin stability for decades.
Key Words: Landslide ratio, landslide recovery, typhoon Morakot, recovery time, recovery level.