The initiative

r.slope.stability is a common initiative including scientists from Austrian and Italian universities and research institutes. Explore the philosophies and rationales of the initiative and learn more about its logical framework and the desired outcomes.

Summary

The master goal of r.slope.stability is to provide a GIS-based, free and open source slope stability model

  • following geotechnical principles;
  • being able to deal with varying geologic conditions and landslide geometries, ranging from shallow soil slips to deep-seated mass movements in geologically compex areas;
  • being suitable for large areas, including tens to hundreds of square kilometres or more;
  • appropriately accounting for the natural variability of the governing parameters.

The software therefore goes far beyond the classic infinite slope stability or statistical approaches usually applied with GIS-based landslide susceptibility models. r.slope.stability considers the 3D geometry of the sliding surface and evaluates the factor of safety (FoS) or the probability of slope failure (Pf) for a large number of randomly selected potential slip surfaces, ellipsoidal or truncated in shape. For each pixel of the study area, the lowest value of FoS or the highest value of Pf out of all tested slip surfaces touching the pixel is applied, giving an estimate of the landslide susceptibility in the study area.

The model input consists in a DEM, one or more maps of lithological classes and/or layers, and the geotechnical and geohydraulic parameters associated to each class and layer. For Pf, ranges of geotechnical parameter values derived from laboratory tests and - optionally - a range of possible truncated depths are used as input. Different strategies are available for sampling of the parameters. Probability density functions are exploited to assign Pf to each ellipsoid.

Yielding representative results usually requires testing a very large number of slip surfaces (for large study areas, several hundreds of millions). Appropriate strategies are needed to keep the computing time at an acceptable level. For this reason, r.slope.stability includes the option to split the study area into a defined number of tiles, allowing to exploit multiple processors (cores) and therefore a parallel computational approach. Tests have shown that this type of strategy may reduce the computing time by a factor >20.

In contrast, r.slope.stability can also be used to analyze single landslides or slopes.

r.slope.stability is open source, distributed under the GNU General Public Licence. It is developed as a C- and Python-based raster module of the software GRASS GIS. The software further includes a validation and visualization module building on the R Project for Statistical Computing.

Logical framework
Longitudinal section