Effectiveness of Direct Protection Forests in Rockfall Mitigation: A Risk- and Cost-Based Assessment in Baunei (Sardinia, Italy)

Rockfalls represent a widespread natural hazard that threatens infrastructures and settlements in mountainous and coastal areas. In Baunei (Sardinia, Italy), steep carbonate cliffs above the SS125 road frequently generate block detachments that endanger traffic and nearby urban areas. The present work adopts a quantitative risk assessment framework, consistent with the Swiss PLANAT guidelines, to evaluate the protective effectiveness of direct-protection forests in combination with engineered barriers. The framework integrates the key components of hazard, exposure, and vulnerability to quantify direct-impact risk and associated economic loss. Using Rockyfor3D simulations, three scenarios were analysed: bare slope, forest only, and forest plus protective works. The results demonstrate that vegetation markedly reduces both runout distance and kinetic energy of falling blocks, halving the direct-impact risk compared to bare-slope conditions. The addition of barriers further decreases residual exposure, with most trajectories intercepted and remaining impacts limited to low-energy classes. Monetised risk estimates confirm an 84% reduction with forest cover alone and near-complete mitigation when complemented by fences, except in short discontinuous segments. The proposed approach offers a replicable and cost-effective tool for rockfall risk management and sustainable protection forest planning in Mediterranean settings.