How To: Identify ridgelines from a DEM
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.
This workflow uses Map Algebra and the Hydrology Toolset to derive ridgeline features from a DEM.
- Fill the DEM using the Fill tool in the Hydrology Toolset.
For more information on the Fill tool read Creating a depressionless DEM.
- Switch the high/low values in the Fill DEM by using the Raster Calculator to multiply the Fill DEM by -1.
- 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'.
For more information on this tool read Flow Direction (Spatial Analyst).
- 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
For more information on this tool read Flow Accumulation (Spatial Analyst).
- Set the Flow Accumulation threshold and create the stream network raster using the Raster Calculator.For 9.3.1:
- 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'.
For more information on this tool read Stream Order (Spatial Analyst).
- Create a ridgeline shapefile by running the Stream to Feature tool with the Stream Order raster as the 'Input stream raster'.
For more information on this tool read Stream to Feature (Spatial Analyst).