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How To: 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

This workflow uses Map Algebra and the Hydrology Toolset to derive ridgeline features from a DEM.

  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.
    [O-Image] Raster Calculator Image
  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

    [O-Image]
    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:
    [O-Image]
    For 10.0:
    [O-Image]

  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).