Automatic optimization and delineation of nested slope units with r.slopeunits v2.0

Slope unit delineation falls under the wider domain of geomorphological surface classification, with a few peculiarities. Surface classification is mostly achievable with variations of segmentation methods, requiring data of different nature, while (automatic) slope unit delineation only depend on the information in a digital elevation model. In particular, slope units strongly relate to the stream network in an area, which requires an extra bit of knowledge with respect to simple segmentation of the surface into areas with similar local properties. A slope unit encompasses a region of the surface of size typically ranging from a fraction to a few square kilometers, and is recognizable in the field as a hillslope. For automatic slope unit delineation, we rely on specialized software. This work introduces an updated version of the r.slopeunits software. The previous version of r.slopeunits, a GRASS GIS module published in 2016, represented a common choice for slope unit delineation in the literature. The new software introduces new features, especially the optimization of input parameters and multilayer delineation capabilities. We briefly describe the new software, and describe preliminary results for a multi-layer slope unit map of Italy.