Diversity of Materials in Landslide Bodies in the Vinodol Valley, Croatia

Abstract

Numerous landslides of different types present common hazardous phenomena in the Vinodol Valley (64.57 km²), situated near the City of Rijeka in coastal part of Croatia. During the previous and present geological investigations in the Vinodol Valley almost all landslide types were identified: falls, topples, slides and flows. The Vinodol Valley is characterized by irregular shape and a range of different landforms due to complex geological and geomorphological conditions. The inside of the valley is built of Paleogene siliciclastic (flysch) deposits, which is surrounded by the relatively steep carbonate borders composed of Upper and Cretaceous limestone. Along the most part of the NE border vertical rocky cliffs occur. The lower parts and the bottom of the valley (i.e., flysch deposits) are covered by heterogeneous Quaternary superficial deposits. In the Vinodol Valley more than 200 active and dormant landslides in soils were identified. Most of the active landslides are covered by dense forest vegetation. Original landslide topographies of dormant landslides are significantly modified by the anthropogenic agricultural activities. For this reason, the appropriate landslide identification and mapping method is the visual interpretation of the high-resolution LiDAR-derived imagery. Identified landslides are generally shallow to moderate shallow, with slip surface depth of several meters, and small to moderate small, with volumes in a range of 10³–10⁵ m³. Due to the diversity of geological conditions in the Vinodol Valley and the large number of identified landslides, the index and classification properties of soils from the landslide-forming materials were investigated. Soil samples were taken and laboratory tested according to the rules of the European Soil Classification System. In this paper, results of preliminary investigations of the relationship between the different types of landslides and the landslide-forming materials are presented.