Slope calculation using ArcGIS

By Vincent Anderson,2014-12-23 20:59
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Slope calculation using ArcGIS

    GIS for Watershed Modeling Exercise

Slope calculation using ArcGIS

Save the following to a text file elev.txt

ncols 5

    nrows 4

    xllcorner 0

    yllcorner 0

    cellsize 100

    NODATA_value -9999

    57 55 47 48 48

    53 67 56 49 52

    53 52 45 42 43

    51 58 40 41 40

Based on the elevation grid:

    1. Manually assign eight direction pour point model grid

    2. Draw flow direction grid

    3. Hand calculate flow accumulation grid

    4. Hand draw drainage line

Open ArcMap and ArcToolbox. Use the tool Conversion Tools ; To Raster ; ASCII to Raster to import this grid file into

    ArcMap. Specify a name and location for the Output raster (such as elev) and specify the Output data type as FLOAT.





Use the Identify button on the grid created to verify that the numbers correspond to the values in the table above.

Open Tools ; Extensions and verify that the Spatial Analyst function is available and checked.


Select Spatial Analyst ; Surface Analysis ; Slope on the Spatial Analyst toolbar.

    At the dialog that appears select your output raster (elev )as the input surface and select the output in Degree or Percent. You will get something like the following:



You can make the slop raster permanent by right click the layer slope of elev, then select Make Permanet:

Calculating Aspect:

    Select Spatial Analyst ; Surface Analysis ; Aspect on the Spatial Analyst toolbar. At the dialog that appears select elev as the input surface.




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