Identifying Basins
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.
____ 21. 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.
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