Due to the trend of climate change, the extreme rainfall event could last for a long duration with a high intensity. Such extreme rainfall event is likely to trigger severe landslides and debris flows. Typhoon Kalmaegi with a high rainfall intensity and an accumulated rainfall of more than 1000 mm caused severe landslides and debris flow hazard in southern Taiwan in 2008. Typhoon Morakot with different rainfall pattern also caused extensive landslides and debris flow hazard in southern Taiwan in 2009 with an accumulated rainfall of more than 3000 mm. The study area includes five debris flow torrent basins in southern Taiwan with debris flow triggered in both events. Field investigation and numerical simulations of the debris flow were conducted on the five basins of the two typhoon events. The analysis results show that the higher accumulated rainfall leads to larger debris deposition volume, inundated area, and deposition depth, which consists with the field investigation results, and suggests a higher impact to debris flow basin. The effect of high accumulated rainfall is more significant for small basin, and no correlation was found for rainfall intensity. A linear relation can be found for deposition volume versus basin area caused by extreme events, and the data were higher compared to worldwide dataset by Marchi et al. (2018). It is suggested that the extreme events might not fit the general trend, and properly estimating debris volume related hazard would require more comprehensive consideration of the precipitation characteristics. The high accumulated rainfall induced by climate changes would cause more severe hazard and should be taken into account for mitigation strategy.