NAME
r.divergence - Computes divergence of a vector field defined by magnitude and direction
KEYWORDS
raster,
divergence
SYNOPSIS
r.divergence
r.divergence --help
r.divergence magnitude=name direction=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:
- magnitude=name [required]
- Name of input raster map representing magnitude
- direction=name [required]
- Name of input raster map representing direction
- Direction is in degrees ccw from the east
- output=name [required]
- Name of output divergence raster
Module
r.divergence computes the divergence of a vector field
given by
magnitude and
direction raster maps.
Direction is in degrees counterclockwise from the east
and can be computed using
r.slope.aspect.
This module can be used for estimating erosion and deposition rates for a steady state overland flow
using USPED (Unit Stream Power based Erosion Deposition) model.
Net erosion/deposition is estimated as a change in sediment flow rate
expressed by a divergence in sediment flow.
In North Carolina sample dataset, we compute net erosion/deposition.
g.region raster=elev_lid792_1m -p
r.slope.aspect elevation=elev_lid792_1m slope=slope aspect=aspect
r.flow elevation=elev_lid792_1m flowaccumulation=flowacc
# exponents m=1.3 and n=1.2
# multiply flowaccumulation by cell area/resolution to get contributing area per unit width
r.mapcalc "sflowtopo = pow(flowacc * 1.,1.3) * pow(sin(slope),1.2)"
# Compute sediment flow by combining the rainfall, soil and land cover factors
# with the topographic sediment transport factor.
# We use a constant value of 270. for rainfall intensity factor.
r.mapcalc "sedflow = 270. * soils_Kfactor * cfactorbare_1m * sflowtopo"
r.divergence magnitude=sedflow direction=aspect output=erosion_deposition
# set suitable color table
r.colors map=erosion_deposition rules=- << EOF
0% 100 0 100 #dark magenta
-100 magenta
-10 red
-1 orange
-0.1 yellow
0 200 255 200 #light green
0.1 cyan
1 aqua
10 blue
100 0 0 100 #dark blue
100% black
EOF
r.slope.aspect
Anna Petrasova,
NCSU GeoForAll Lab
Helena Mitasova,
NCSU GeoForAll Lab
SOURCE CODE
Available at:
r.divergence source code
(history)
Latest change: Tuesday Nov 05 09:35:47 2024 in commit: f00067506253c89598cffadc3c7fa07cff7233fd
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GRASS Development Team,
GRASS GIS 8.4.1dev Reference Manual