The feasibility studies of mitigation measures for landslides located above the Koroška Bela settlement in Northwest Slovenia

This study represents the feasibility study on landslide mitigation measures above the settlement of Koroška Bela in northwestern Slovenia. The settlement of Koroška Bela is very densely populated (about 2,100 inhabitants) and has a well-developed industry and infrastructure. The area above Koroška Bela has been recognized as one of the most active landslide-prone areas in Slovenia. It attracts attention due to historical evidence of past debris flows in recent geological history. The first recorded event occurred in the 18th century and caused the partial or complete destruction of more than 40 buildings and devastated cultivated areas in the village of Koroška Bela. In recent decades, two more events have occurred: In April 2017, part of the Čikla landslide turned into a debris flow, and in August 2023, the reactivation of the Urbas landslide led to the disruption of alarm systems and the triggering of emergency sirens. Each event was associated with prolonged and intense rainfall.

To reduce the landslide risk in Koroška Bela, a comprehensive engineering, geological and hydrogeological characterization of landslide-prone areas was required to prepare feasibility studies for mitigation and remediation strategies. So far, no specific remediation measures have been implemented, as the existing check dams do not have the necessary capacity to effectively manage sediment and debris flows.

Our findings highlight the need for holistic mitigation measures in order to protect residents and infrastructure. Key areas include stabilizing the Čikla and Urbas landslides and controlling sediment transport in the associated torrent systems. Given the complexity of these landslides, we propose a combination of traditional gray engineering (structural) measures alongside with hybrid solutions that integrate both gray and green elements. For debris- flow management, gray measures such as debris- flow barriers and flexible barriers are essential. To stabilize landslide-prone areas, hybrid solutions combining torrent channel works, drainage systems, and vegetative stabilization should be implemented.

As these landslides are situated in mountainous areas designated as Natura 2000 protected area, mitigation measures should incorporate green design principles that support both visual integration and ecological functions.

Acknowledgments: This research was funded by Slovenian Research And Innovation Agency through research project “J6-4628 - Evaluation of hazard-mitigating hybrid infrastructure under climate change scenarios” and research program “P1-0419 - Dynamic Earth”. Additional financial support was provided by the Ministry of Environment and Spatial Planning, and the Municipality of Jesenice.