The potential impact of climate change on typhoon-triggered landslides in Taiwan, 2010-2099

In the western North Pacific, including Taiwan, typhoons (tropical cyclones) and rainfall rates are predicted to intensify as a result of climate change. Because typhoons are the major triggers of shallow landslides in Taiwan, landslide activity is expected to increase as global warming continues. To assess the worst scenario of landslide occurrence in a mountainous watershed till the end of the century, this study developed a method to select a global climate model (GCM) from 21 available GCMs and correct its monthly precipitation data, before downscaling annual maximum (24-h) rainfall from the corrected GCM data as input to the factor-of-safety model for landslide prediction. Average annual maximum rainfall is expected to increase from 322. mm in 1960-2008 to 371. mm in 2010-2099. Average total unstable area is expected to increase from 1135. ha in 1960-2008 to 1280. ha in 2010-2099, a 12% increase. As a first attempt to assess landslide activity due to global warming, this study is useful as a reference for watershed management in Taiwan. The results must be evaluated in light of uncertainties caused by the correction and downscaling of GCM data and the input parameters to the slope stability model.