Module 03


Yesterday in the Great Smokies
Webcam archive
GEO 509: Workshop in Geospatial Technologies

03: Inundation


Assume that floods have a maximum height above stream and that the floodplain is all adjacent areas below that height.* Using relative elevation models (REM), calculate and visualize potential inundation areas for a given floodplain.

Methods overview

  • Query for stream in your watershed.
  • Correct stream alignment against aerial imagery.
  • Sample ground elevations along stream.
  • Interpolate elevations to create a relative elevation model.
  • Calculate and visualize extent of inundation.

Edit candidate stream

  • Stream alignment may not match aerial imagery. Edit stream for best results for analysis.

Task 3

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  • Relative Elevation Model
  • Height above river in AOI.

Step 1

  • Sample elevations
  • along stream at a regular interval, e.g. 40ft.
  • That's why are river flowline is so important!

Step 2

  • Interpolate Surface
  • IDW – Inverse Distance Weighting
  • using sampled elevations along river.
  • Creates a surface of gradual elevation change.

Step 3

  • Subtract REM from DEM, e.g., DEM - REM.
  • to find height above river.


  • Find and symbolize areas that are below a certain height above the river.
  • Query REM, e.g., REM < 25.


  • This analysis has complicated output.
  • Let's animate it in ArcGIS Pro!