The availability of high resolution Digital Elevation Models (DEM)
at a regional scale enables the analysis of topography with high
levels of detail. Hence, a DEM-based geomorphometric approach becomes
more accurate for detecting potential rockfall sources. Potential
rockfall source areas are identified according to the slope angle
distribution deduced from high resolution DEM crossed with other
information extracted from geological and topographic maps in GIS
format. The slope angle distribution can be decomposed in several
Gaussian distributions that can be considered as characteristic of
morphological units: rock cliffs, steep slopes, footslopes and plains.
A terrain is considered as potential rockfall sources when their
slope angles lie over an angle threshold, which is defined where
the Gaussian distribution of the morphological unit "Rock cliffs"
become dominant over the one of "Steep slopes". In addition to this
analysis, the cliff outcrops indicated by the topographic maps were
added. They contain however "flat areas", so that only the slope
angles values above the mode of the Gaussian distribution of the
morphological unit "Steep slopes" were considered. An application
of this method is presented over the entire Canton of Vaud (3200
km2), Switzerland. The results were compared with rockfall sources
observed on the field and orthophotos analysis in order to validate
the method. Finally, the influence of the cell size of the DEM is
inspected by applying the methodology over six different DEM resolutions.