r.water.outlet(1grass) GRASS GIS User's Manual r.water.outlet(1grass)
NAME
r.water.outlet - Creates watershed basins from a drainage direction
map.
KEYWORDS
raster, hydrology, watershed
SYNOPSIS
r.water.outlet
r.water.outlet --help
r.water.outlet input=name output=name coordinates=east,north [--over-
write] [--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 drainage direction map
output=name [required]
Name for output watershed basin map
coordinates=east,north [required]
Coordinates of outlet point
DESCRIPTION
r.water.outlet generates a watershed basin from a drainage direction
map and a set of coordinates representing the outlet point of water-
shed.
Input drainage direction map indicates the "aspect" for each cell. Mul-
tiplying positive values by 45 will give the direction in degrees that
the surface runoff will travel from that cell. The value -1 indicates
that the cell is a depression area. Other negative values indicate that
surface runoff is leaving the boundaries of the current geographic re-
gion. The absolute value of these negative cells indicates the direc-
tion of flow. This raster map is generated from r.watershed.
Output raster map values of one (1) indicate the watershed basin. Val-
ues of zero (0) are not in the watershed basin.
NOTES
In the context of this program, a watershed basin is the region up-
stream of an outlet point. Thus, if the user chooses an outlet point on
a hill slope, the resulting map will be a thin silver of land repre-
senting the overland slope uphill of the point.
EXAMPLE
A watershed in the North Carolina sample dataset region:
g.region raster=elev_lid792_1m -p
# the watershed outlet position should be placed on a stream (from
# accumulation map):
r.watershed elev_lid792_1m threshold=5000 accumulation=accum_5K drainage=draindir_5K basin=basin_5K
r.water.outlet input=draindir_5K output=basin_A30 coordinates=638740.423248,220271.519225
d.mon wx0
d.rast map=accum_5K
d.rast map=basin_A30
# overlay with transparency
r.colors map=basin_A30 color=grey
d.his h=accum_5K i=basin_A30
# report outlet size in ha
r.report map=basin_A30 units=h
Figure: Watershed draped over flow accumulation
SEE ALSO
r.wateroutlet.lessmem (addon), d.where, r.basins.fill, r.watershed,
r.topidx
AUTHOR
Charles Ehlschlaeger, U.S. Army Construction Engineering Research Labo-
ratory
SOURCE CODE
Available at: r.water.outlet source code (history)
Accessed: unknown
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GRASS 7.8.7 r.water.outlet(1grass)
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