r.slope.stability is evaluated for the Collazzone Area in Umbria, central Italy.
The Collazzone Area in Umbria, central Italy, serves as a laboratory for testing r.slope.stability. Landslides are frequent and abundant and landslide, morphological and geological information is available.
The area extends for 78.9 square kilometres, the terrain elevation ranging from 145 m asl along the Tiber River flood plain to 634 m asl at Monte di Grutti. The landscape in the Collazzone area is hilly, and the lithology and the strike and dip of the lithologic layers control the morphology of the slopes. Sedimentary rocks, Lias to Holocene in age, crop out in the area, with most of the area covered by continental sediments (including gravel, sand and clay), Pliocene to Pleistocene in age. Fine to medium texture soils characterized by a xeric moisture regime typical of the Mediterranean climate mantle the area with thicknesses in the range from a few decimetres to more than 1.5 m. Cultivated areas, woods and abandoned areas are most common. The total annual rainfall averages at approx. 900 mm, with a maximum in autumn. Snow fall occurs on average every 2–3 years. Intense or prolonged rainfall periods are the primary natural triggers of landslides in the area, followed by the rapid melting of snow. Landslides range in age, type, morphology and volume from very old, partly eroded, large and deep-seated slides to young and shallow slides and flows. The recent landslides are most abundant in the cultivated areas and rare in the forested terrain, indicating a relationship with agricultural practices.
Information on landslides is abundant in the Collazzone Area. The landslide information was obtained through visual interpretation of multiple sets of aerial photographs, orthophotos, hillshade images obtained from Lidar DEMs, monoscopic and stereoscopic VHR optical (panchromatic and multi-spectral) satellite images and repeated field surveys.
Further, a 5 m DEM is available for the Collazzone Area. Lithological information obtained through field mapping aided by the interpretation of medium-scale aerial photographs is available, too. The bedding planes of the lithological layers were reconstructed by field mapping of the bedding traces, used for modelling of the subsurface geometry of the corresponding layers. The geotechnical characteristics of the area were invesigated by an extended campaign of field sampling and laboratory analyses (geotechnical, granulometric and mineralogic parameters). Analysis of the data revealed a significant variability in the properties of the geological materials present in the study area.
More details on the data used and the results obtained are given by