## DESCRIPTION

r.carve accepts vector stream data as input, transforms them to raster, and subtracts a default-depth + additional-depth from a DEM. If the given width is more than 1 cell, it will carve the stream with the given width. With the -n flag it should eliminate all flat cells within the stream, so when and if the water gets into the stream it will flow. The points option generates x,y,z for points which define the stream with the z-value of the bottom of the carved-in stream. These points can then be combined with contours to interpolate a new DEM with better representation of valleys.

## NOTES

r.carve does not create a depressionless DEM because many depressions are in flat areas and not in the streams.

## EXAMPLE

North Carolina sample dataset:

    # set computational region
    g.region raster=elev_lid792_1m -p

    # digitize a ditch for the farm pond
    echo "L  3 1
     638692.93595422 220198.90026383
     638737.42270627 220149.74706926
     638984.43306379 220148.19158842
     1     1" | v.in.ascii -n input=- output=ditch format=standard

    # visualize original data
    d.mon wx0
    d.rast elev_lid792_1m
    d.vect ditch

    # carve
    r.carve raster=elev_lid792_1m vector=ditch output=carved_dem width=3 depth=0.5

    # visualize resulting carved DEM map
    d.rast carved_dem

    # visualize
    r.relief input=elev_lid792_1m output=elev_lid792_1m_shaded
    r.relief input=carved_dem output=carved_dem_shaded
    d.rast elev_lid792_1m_shaded
    d.erase
    d.rast carved_dem_shaded

    # flow accumulation
    r.watershed elevation=elev_lid792_1m accumulation=elev_lid792_1m_accum
    r.watershed elevation=carved_dem accumulation=carved_dem_accum
    d.rast elev_lid792_1m_accum
    d.erase
    d.rast carved_dem_accum

    # differences
    r.mapcalc "accum_diff = elev_lid792_1m_accum - carved_dem_accum"
    r.colors accum_diff color=differences
    d.erase
    d.rast accum_diff

Fig: Original 1m LiDAR based DEM with vector streams map on top | Fig: Original 1m LiDAR based DEM shown as shaded terrain
Fig: Carved 1m LiDAR based DEM | Fig: Carved 1m LiDAR based DEM shown as shaded terrain
Fig: Flow accumulation in original 1m LiDAR based DEM | Fig: Flow accumulation in carved 1m LiDAR based DEM

## KNOWN ISSUES

The module does not operate yet in latitude-longitude coordinate reference system. It has not been thoroughly tested, so not all options may work properly - but this was the intention.

## REFERENCES

Terrain modeling and Soil Erosion Simulations for Fort Hood and Fort Polk test areas, by Helena Mitasova, Lubos Mitas, William M. Brown, Douglas M. Johnston, GMSL (Report for CERL 1999)

## SEE ALSO

r.flow, r.fill.dir, r.watershed

## AUTHORS

Bill Brown (GMSL)
GRASS 6 update: Brad Douglas