[GRASS-SVN] r64985 - grass-addons/grass7/raster/r.divergence

[svn_grass at osgeo.org]

Author: annakrat
Date: 2015-04-04 13:27:43 -0700 (Sat, 04 Apr 2015)
New Revision: 64985

Modified:
   grass-addons/grass7/raster/r.divergence/r.divergence.html
Log:
r.divergence: add example

Modified: grass-addons/grass7/raster/r.divergence/r.divergence.html
===================================================================
--- grass-addons/grass7/raster/r.divergence/r.divergence.html	2015-04-04 14:47:14 UTC (rev 64984)
+++ grass-addons/grass7/raster/r.divergence/r.divergence.html	2015-04-04 20:27:43 UTC (rev 64985)
@@ -4,10 +4,45 @@
 Direction is in degrees counterclockwise from the east
 and can be computed using <em><a href="r.slope.aspect.html">r.slope.aspect</a></em>.
 
+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.
+
 <h2>EXAMPLES</h2>
+In North Carolina sample dataset, we compute net erosion/deposition.
 
-TBD
+<div class="code"><pre>
+g.region raster=elev_lid792_1m
+r.slope.aspect elevation=elevation slope=slope aspect=aspect
+r.flow elevation=elevation 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
+</pre></div>
+
 <h2>SEE ALSO</h2>
 
 <em><a href="r.slope.aspect.html">r.slope.aspect</a></em>