Arc Export Raster to asc

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TUFLOW can directly read elevation data from a Digital Elevation Model (DEM). The format recognised by TUFLOW is ESRI ASCII Grid (.asc), this is an open text format that is recognised by a wide range of software including ArcGIS, MapInfo and Quantum GIS. The instructions below outline the process for exporting from a raster layer in ArcMap to a ESRI ASCII grid.

TUFLOW can also read .asc format data for setting a number of model parameters including, initial water level (Read GRID IWL == ), Soil Type (Read Grid Soil == ), roughness (Read Grid CnM == ), storage reduction factor (Read Grid SRF == ).


  1. Open the raster layer that you wish to convert.
  2. In the Arc Toolbox menu, select Conversion Tools >> From Raster >> Raster to ASCII

  3. Arc raster to asc.jpg
  4. In the dialogue, select the desired input raster and set the output filename. Note, there is no set extension for this file type, both .asc and .txt are widely used.
    Arc raster to asc 2.jpg
  5. The DEM file is ready for reading into TUFLOW.


To convert between the .asc and .flt format the TUFLOW utility "asc_to_asc" can be used.

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