GIS for Watershed Modeling Exercise I

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.



to be continued
Previous
Next Post »