Identify ridgelines from a DEM

Summary

The instructions provided describe how to identify ridgelines from a DEM. Spatial Analyst and the Hydrology Toolset can be used to identify and extract ridgeline features from an elevation raster (DEM) in the same manner as a stream network can be created by reversing the DEM cell values.

Procedure

1. Fill the DEM using the Fill tool in the Hydrology Toolset.
   
   

   Note:
   For more information on the Fill tool read Creating a depressionless DEM.

   
   
2. Switch the high/low values in the Fill DEM by using the Raster Calculator to multiply the Fill DEM by -1.
   
   
3. Run the Flow Direction tool using the output raster from step 2 as the 'Input surface raster' and checking 'Force all edge cells to flow outward'.
   
   

   Note:
   For more information on this tool read Flow Direction (Spatial Analyst).

   
   
4. Run the Flow Accumulation tool using the output raster from step 3 as the 'Input flow direction raster'.
   
   • Make sure to set the output data type to Integer, rather than Float.
   

   Flow Accumulation tool

   
   
   

   Note:
   For more information on this tool read Flow Accumulation (Spatial Analyst).

   
   
5. Set the Flow Accumulation threshold and create the stream network raster using the Raster Calculator.
   
   
   For 9.3.1:
   
   For 10.0:
   
   
   
   
6. Create a Stream Order raster using the stream network raster (step 5) for the 'Input steam raster' and the Flow Direction raster (step 3) for the 'Input flow direction raster'.
   
   
   

   Note:
   For more information on this tool read Stream Order (Spatial Analyst).

   
   
7. Create a ridgeline shapefile by running the Stream to Feature tool with the Stream Order raster as the 'Input stream raster'.
   
   
   

   Note:
   For more information on this tool read Stream to Feature (Spatial Analyst).