3D Rockfall Analyses of Marl Slopes in Brovinje, Croatia

Summary

Abstract

Rockfall is a geohazard involving the downslope movement of detached rock fragments by falling, rolling, or sliding. It is driven by factors such as weathering, dynamic triggers, hydrological changes, andanthropogenic driversand is increasingly influenced by climate change, which accelerates erosion and weakens rock mass properties. The coastal site of Brovinje in the Istria Peninsula, Croatia, is particularly vulnerable due to its geological composition and exposure to marine processes. Although slope stability analyses indicate the absence of large-scale instability, the presence of detached rock blocks necessitates a detailed hazard assessment to evaluate rockfall risks. An integrated dataset including geotechnical laboratory testing, geophysical surveys, and high-resolution terrain models from UAV imagery and handheld LiDAR scanning was used. Slope stability was evaluated, confirming stability even under projected sea-level rise. Subsequently, 3D rockfall analyses were conducted using RocFall3 software. Two types of line seeders represented rock sources: limestone blocks from the slope crest and marl blocks from the eroded lower slope. Material properties and rigid body dynamics were applied to simulate trajectories and impacts. The simulations revealed highly energetic rockfall events, characterized by substantial velocities, elevated kinetic energy, and long runout distances. A significant proportion of simulated trajectories reached the beach area, indicating a direct hazard to people. Heatmap analysis identified zones with concentrated rockfall endpoints, which correspond well with field observations of fallen blocks on the beach and in the sea.The slope presents significant rockfall hazardwhich may be exacerbated by climate change. The study highlights the value of high-resolution data and 3D modelling for identifying hazard zones and supports the development of risk maps and mitigation measures.