This document describes how to generate a drainage line in ArcGIS using spatial analyst and ArcHydro tools. It involves calculating the aspect, flow direction, and flow accumulation from a digital elevation model, then using ArcHydro tools to define streams, segment streams into grids, and convert the stream links grid into vector drainage line features. The key steps are 1) preparing elevation and other raster data, 2) calculating hydrology rasters, and 3) using ArcHydro tools to extract and convert stream networks into vector drainage lines.