Taitung County with the total area of 3,515.24 km2 lies in the eastern Taiwan. The topography of hillslopes at Taitung County is quite steep combined with fragile geological structure. After Typhoon Morakot, Taimali watershed located at the southern part of Taitung County was selected as major study area. The mechanism, behavior, and scale of sediment disasters are analyzed to rule out their interaction of the factors regarding to the debris flow occurrence in Taitung area. In this study, 522 disaster prevention engineering sites were investigated from the field and analyzed by using the Multiple Linear Regression Analysis. Finally, GPS/GIS/RS integrated with the digital terrain data was used to establish risk assessment model which can be utilized as an indication of sediment disasters occurred at Taimali watershed attacked by Typhoon Morakot in 2009. The accuracy of this model estimation is more than 80%. All results established by this study can help Taitung Country set up its own disaster prevention system and keep well development of rural and city in the eastern Taiwan.