Slope Units Delineation
The software r.slopeunits requires a DEM, an optional raster layer showing alluvial plains, and the following user-defined parameters :
the initial flow accumulation area threshold (t in square meters),
the reduction factor r (integer, >1), that is used to calculate, iteratively, new values for the flow accumulation area threshold (t = t-t/r). Values larger than 5 are recommended.
the minimum surface area for the slope-units (a in square meters),
the minimum circular variance of terrain aspect within a slope-units (c, varies between 0 and 1, where 0 means no variance, i.e. cells dip in the same direction, and 1 means maximum variance)
the maximum surface area for the slope-units (maxarea, in square meters, optional),
threshold area value for the cleaning procedures (cleansize, in square meters, used to remove very small slope units that may occur give some geomorphological conditions)
We provide a compressed location for GRASS GIS 7.0 that can be used to test the code.
GRASS GIS 7.0, Python, Bash
Installation and run
The software have been tested on a Ubuntu 14.04 LTS server but should run on a generic GNU/Linux machine.
The two files provided must be copied inside the “scripts” folder of the GRASS GIS installation directory. The must be set executable. A typical approach, for the installation, is:
#open a bash shell
#move to the download folder, e.g.
#move the files
mv r.slopeunits /usr/lib/grass70/scripts
mv clean_method_3.sh /usr/lib/grass70/scripts
#give execution rights
chmod ugo+x /usr/lib/grass70/scripts/r.slopeunits
chmod ugo+x /usr/lib/grass70/scripts/clean_method_3.sh
#Run GRASS GIS, move in the location containing the digital elevation model type and:
#to see the options. The minimal command line to obtain a slope-units delineation is
r.slopeunits demmap=[dem] slumap=[output_SU_map] thresh=[t, square meters] circularvariance=[c] areamin=[a, square meters] reductionfactor=[r, r>2] maxiteration=[max number of iterations]
#see M. Alvioli, I. Marchesini, P. Reichenbach, M. Rossi, F. Fiorucci, F. Ardizzone, F. Guzzetti
#(2015) for explanations and additional options.
#please address comments, questions and gux fixes rquests to: ivan.marchesini[AT]irpi.cnr.it;