The Importance of Landsliding in a Flysch Geomorphic System: The Example of the Goriska brda Hills (W Slovenia)

In geomorphology flysch regions are well known for landsliding. In Slovenia, Eocene flysch is found in the south-western part of the country. In these low-lying Mediterranean regions landslides are frequent and permanent phenomena influencing both morphology and human society. The aim of the article is to show how landslide susceptibility maps may be applied in geomorphology. This study presents one of the first evaluations of the long-term geomorphic evolution using the relative landslide rate map and soil erosion data. Firstly, data on 800 landslides in a flysch region of Goriska brda Hills were used to evaluate landslide Susceptibility. Landslide susceptibility was calculated by different models using the geographic information systems. Secondly, presumed landslide volume in a known reference period, calculated by the means of the landslide susceptibility map, was compared to the Volume of eroded soil that had been measured on small-scale erosion plots. The results show that landslides are important morphogenetic factors due to their relatively frequent occurence. Since soil erosion is mostly limited to deforested and cultivated hilltops and mostly contributes to their lowering, landslides mainly transform lower parts of slopes. In some cases they may have significantly contributed to recent (e.g. post-Pleistocene) valley evolution, especially by transforming the Upper-most parts of the valleys and by widening their lower reaches.