SDAS stands for Spatial Decision Assistance of Watershed Sedimentation. It is a set of functions that produce (instantly) tool to predict annual erosion rate and sediment yield of a watershed. SDAS embedded with some TauDEM executables which is developed at Utah State University (USU) (may be obtained from http://hydrology.usu.edu/taudem/taudem5.0/). This makes SDAS capable to complete hydrological spatial analysis such as hydrologic digital elevation model analysis , river network and watershed delineation from raw Digital Elevation Model (DEM). In other words SDAS is designed to be a “one-button” Geographic Information System (GIS) modeling toolbox.