r.topidx.1grass - Man Page
Creates a topographic index (wetness index) raster map from an elevation raster map.
Keywords
raster, hydrology, wetness, topographic index
Synopsis
r.topidx
r.topidx --help
r.topidx input=name output=name [--overwrite] [--help] [--verbose] [--quiet] [--ui]
Flags
- --overwrite
Allow output files to overwrite existing files
- --help
Print usage summary
- --verbose
Verbose module output
- --quiet
Quiet module output
- --ui
Force launching GUI dialog
Parameters
- input=name [required]
Name of input elevation raster map
- output=name [required]
Name for output topographic index raster map
Description
r.topidx creates topographic index (wetness index), ln(a/tan(beta)), map from elevation map
where
a: the area of the hillslope per unit contour length that drains through any point,
tan(beta): the local surface topographic slope (delta vertical) / (delta horizontal).
Input maps may have NULL values. For example, if you have a MASK for a watershed (basin map from r.water.outlet), the following command will create a masked elevation map (belev):
r.mapcalc "belev = if(isnull(basin), basin, elev)"
r.stats -Anc prints out averaged statistics for topographic index.
Example
Running the command below will generate the topographic index map shown in the figure:
g.region raster=elevation -p r.topidx input=elevation output=topidx_elevation
Figure: topographic index map derived from elevation map
References
Cho, H., 2000. GIS Hydrological Modeling System by Using Programming Interface of GRASS. Master’s Thesis, Department of Civil Engineering, Kyungpook National University, Korea.
Moore, I.D., R.B. Grayson, and A.R. Ladson, 1991. Digital Terrain Modeling: A Review of Hydrological, Geomorphological, and Biological Applications. Hydrological Processes 5:3-30.
See Also
r.topmodel, r.water.outlet, r.mapcalc
Known issues
Authors
Huidae Cho
Hydro Laboratory, Kyungpook National University, South Korea
Based on GRIDATB.FOR by Keith Beven.
Source Code
Available at: r.topidx source code (history)
Accessed: Thursday Jul 20 05:48:28 2023
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