Visualization of Flowpaths

Once the D8 Terrain Processing tool finishes running, the outputs are automatically added to the map document. In the Table of Contents (TOC) you can see the filled DEM, the flow direction raster, the flow accumulation raster, and the hillshade.

There are several techniques that can be used to begin visualizing overland flowpaths. Visualizing flow is traditionally done using the Flow Accumulation raster using either a stretched renderer or creating classes of values. You can use a stretch renderer by following these steps:

  1. Highlight the Flow Accumulation raster in the TOC and right-click to open the Symbology tab. By default, the raster is stretched in grey tones. This can be changed by using the pull-down to the right of the color ramp, scroll to a new choice to add color.
  2. For Stretch Type, we suggest standard deviation or histogram equalize.
  3. Change the Statistics type, change to DRA.  This will use the local view extent to build the statistics for display; changing the view extent will change the manner in which the raster is displayed.
  4. Press "Apply," then "OK."

Here is another way to visualize flow using a classified renderer:

  1. Highlight the Flow Accumulation raster in the TOC and right-click to open the Symbology tab.
  2. Choose the Classify renderer.
  3. Change classes from 5 to 2.
  4. In the Classes list, change the first break point to a value equal to 1 acre of flow accumulation. This would be 1,000 for a 2m DEM (4,046 sq meters/acre and 4 square meters per cell).
  5. Change the color for the first class (<= 1,000) to No color.

Now pan around and you’ll see everywhere that flow accumulation paths are being generated.

For more information you can watch this video (runtime 6:03):