This study analyzes the significant impacts of Typhoon Morakot on land cover and hydrology. The occurrence of typhoons following debris flow is a major indicator of natural disturbance. The hydrological response for Linbian Watershed to land use change was assessed from 2006 to 2012. Land use changes were assessed by three satellite images corresponded to the typhoon in the southern part of Taiwan. Hydrological processes response is also assessed as the change in quantities of runoff and runoff coefficient. The aim of this study is to investigate the land use change influence on the change in runoff coefficient at the Linbian Watershed. The analysis comprises two approaches including temporal and spatial changes. Land cover change and monthly rainfall distribution of the watershed were analyzed before and after the typhoon. The study watershed was dominated by high vegetation cover before the typhoon. Land cover results indicated that 30% of the vegetation has been converted to bare land after Typhoon Morakot, representing the largest area decrease during the study period. Highest monthly rainfall (3916mm) was recorded in the month of August 2009, due to the typhoon. Rainfall and runoff relationship was used to estimate the upper and midstream runoff, which was used to predict the runoff coefficient. This study found that decreasing vegetation area in the basin affected the increase of runoff and runoff coefficient. Three years after the typhoon, the land cover showed that vegetation cover has been recovering. Similarly runoff coefficient and runoff values were stabilized after the typhoon. This analysis reveals that there is a relationship between the vegetation cover and the runoff. This proposed approach also successfully quantifies the effect of typhoons on land cover and the impact on hydrology.
