Multi-year slope processes following the main event and large-scale reactivation of a complex avalanche: the evolution of the Ciprnik avalanche between 2000 and 2023 in the Julian Alps, Slovenia
The Ciprnik complex avalanche was triggered during the night of 18-19 November 2000 as a result of the geological structure (the intrusion of highly fractured carbonate and fine-grained clastite layers is parallel to the slope) and the heavy and prolonged rainfall (613.6 mm in November). The avalanche had a complex transport mechanism, with the material released moving first as a translational slide, then as a debris flow and, in the last stage, as a preconsolidated flow. The volume of the avalanche is estimated at 80,000 m3. During the night of 24-25 October 2023, a large area was reactivated as a result of short but intense rainfall (104.2 mm of rainfall in 24 hours). Such rainfall has a return period of five years in the study area.
The analysis of the changes in the landslide surface between 2006 and 2023 was carried out using digital elevation models created from aerial and drone imagery using the structure-from-motion photogrammetric method. Fourteen sediment samples were collected along the transport and deposition area of the 2023 event and one sample from the 2000 event area, and granulometric analysis was carried out. At the same time, we examined in more detail the data on trigger rainfall events from the Rateče meteorological station.
We found that the landslide area has remained unstable since 2000, moving between 1000 and 3500 m per year.3 material. The October 2023 event had the same transport mechanism as the event twenty-three years ago and measured approximately 26,000 m3. The key difference between trigger rains is their duration, intensity and return periods. The first event was triggered by a record long duration, low intensity rainfall event, while the second event was triggered by relatively frequent, short duration but intense rainfall events.
Summarised from the article NOVAK, Andrej, VRABEC, Marko, ŠMUC, Andrej. Long-term post-event processes and major reactivation of a complex landslide: 2000-2023 evolution of the Ciprnik landslide, Julian Alps, Slovenia. Landslides : Journal of the international consortium on landslides. [Print ed.]. 2025, pp. 1-15. ISSN 1612-510X. DOI: 10.1007/s10346-025-02598-5. [COBISS.SI-ID 246472963]