Nation-wide, general-purpose delineation of geomorphological slope units in Italy

Slope units are portions of terrain, defined by the general requirement of maximizing homogeneity within a single unit and heterogeneity between different ones. Slope units are being used to describe a variety of processes and to assess different natural hazards. An unambiguous and reproducible definition of slope units based on quantitative hydrologic and topographic criteria was previously provided by the r.slopeunits software to automatically draw slope unit polygons on a digital surface. The software contains an adaptive algorithm allowing for a flexible yet well-defined slope unit delineation, by means of an iterative procedure. It requires a digital elevation model and a few input parameters, whose values must be optimized in a sound way, by means of multiple software runs and a proper objective function. The code is designed to quickly produce results on large areas, and in this work we devised an optimization algorithm to delineate slope units over the whole Italian peninsula. We outline the rationale of the optimization procedure for a general purpose slope unit delineation within very large areas. We present preliminary results in Central Italy, specifically a slope unit mosaic in the whole area affected by the 2016 earthquake sequence. The procedure represents a well-defined framework for slope unit delineation over the whole of Italy.