Geologic-Scale Erosion

Posted: Thursday, August 11th, 2005

100 iterations of mass removal based on preferential flow of water as calculated by r.topidx in GRASS. Notice how landform is cutdown most in stream channels, least at the ridges. The basins between ridges appear to "fill" with sediment near the 50th iteration as the entire landform is lowered to sea level (0m). Absolute change in elevation is visble in the elevation profiles below. Example GRASS commands below. Here is a link to a movie, containing all 100 iterations.

Note that this is *not* a direct measure of sediment removal, mearly one means of visualizing the qualitative effects of sediment removal. Actual sediment flow values could possibly be calculated with r.terraflow and some expert knowledge of the area. In addition, sediment transport models such as RUSLE, USPED, and SIMWE will provide a quantitative erosion AND deposition estimate. Details here:

Elevation profiles for selected time steps.

Initial Landform
10 Iterations
50 Iterations
100 Iterations
 r.topidx in=elev_meters out=ti
for x in `seq 0 1 100`
  do r.mapcalc "e = if( float(elev_meters - float($x*ti)) > 0.0 ,float(elev_meters - float($x*ti) ), 0.0 )"
 r.shaded.relief map=e shade=s1
 d.rast s1
 d.barscale at=0,0
 d.out.png out=e_$x res=1
convert `ls *.png | sort -n -k2 -t"_"` movie.mpg
#make an elevation profile
r.profile in=e100 profile=663451.38153808,4038227.40942676,663719.16510544,4041226.58538121 > e100.profile


Raster Operations

GRASS GIS: raster, vector, and imagery analysis

Geologic-Scale Erosion