Basins can be defined simply by the flow directions of water that falls on the study area. As you know, the flow directions are defined by the elevations and slopes.
____ 19. Start the Basin tool. Note that the only input is FlowDir2. Call the output UniqueBasins. How many are there? ________. Zoom to full extent.
____ 20. Using the Raster to Polyline tool, convert the raster dataset StrmChannels to the feature class shapefile Strms.shp. Browse so you can put it in the Hydrology_Data_SA folder. Display Strms.shp with bright yellow. Turn all layers off except Strms.shp and Unique_Basins. It should be pretty clear how the basins are delineated.
Set the Unique Basins layer at 85 percent transparency. (Wait! Wait! Don’t tell me! It’s in my Fast Facts File.16
) In the T/C put Strms.shp at the top, UniqueBasins next, and ElevSurface2 third. Turn those three on and every other layer off so you can get a picture of why the basins are the way they are, in terms of elevation, and why the streams form as they do.