In this study, we studied and monitored a watershed (Pu-tun-pu-nas) with an area of 7 km2 in southern Taiwan which was seriously affected by the major typhoon Morakot in 2009,. This typhoon brought extreme and long duration rainfall, for instance the cumulated rainfall around the study area was approximately 2,425 mm, and consequently caused severe landslides and debris flows. So after the typhoon Morakot, a large amount of landslide yielding materials had been reactivated resulted in active debris flows during recent years. The purpose of this study is to investigate the sediment budgets related to landslides and debris flows after the typhoon Morakot by using the difference of High Resolution DTM (DoD) method to perform subtraction on the DTMs before and after typhoons. To perform this study we acquired three DTMs generated by the aerial images taken by Unmanned Aerial Vehicle (UAV) and Airborne Digital Sensors (ADS) between 2010 to 2015. The results of this study provides not only geomatics and GIS datasets to monitor the terrassic evolution but also essential geomorphological key information to optimize the hazard mitigation planning.