Landslide susceptibility map of Slovenia at scale 1 : 250,000

Abstract

Based on the extensive landslide database that was compiled and standardised at the national level, and analyses of landslide spatial occurrence, a Landslide susceptibility map of Slovenia at scale 1 : 250,000 was completed. Altogether more than 6,600 landslides were included in the national database, of which roughly half are on known locations. Of 3,257 landslides with known location, random but representative 65 % were selected and used for the univariate statistical analyses (χ2 ) to analyse the landslide occurrence in relation to the spatio-temporal precondition factors (lithology, slope inclination, slope curvature, slope aspect, distance to geological boundaries, distance to structural elements, distance to surface waters, flowlength, and landcover type) and in relation to the triggering factors (maximum 24-h rainfall, average annual rainfall intensity, and peak ground acceleration). The analyses were conducted using GIS in raster format with the 25 × 25 m pixel size. Five groups of lithological units were defined, ranging from small to high landslide susceptibility. Also critical slopes for the landslide occurrence, other terrain properties and landcover types that are more susceptible to landsliding were defined. Among triggering factors critical rainfall and peak ground acceleration quantities were defined. These results were later used as a basis for the development of the weighted linear susceptibility model where several models with various factor weights variations based on previous research were developed. The rest of the landslide population (35 %) was used for the model validation. The results showed that relevant precondition spatio-temporal factors for landslide occurrence are (with their weight in linear model): lithology (0.3), slope inclination (0.25), landcover type (0.25), slope curvature (0.1), distance to structural elements (0.05), and slope aspect (0.05).