Risk-mitigation priorities for road networks exposed to slow-moving landslides at municipal scale

Road networks are typically the main component of transportation systems, acting as critical lifelines for mobility, emergency response, and access to essential services. In mountainous and hilly regions, these infrastructures are frequently threatened by slow-moving landslides, which can lead to progressive ground deformation and long-term serviceability loss. Despite the need for continuous operability, local authorities often face significant challenges in risk management due to budget limitations and lack of complete and accurate information. This study proposes a framework aimed at identifying risk-mitigation priorities for road networks exposed to slow-moving landslides at municipal scale by integrating the assessment of landslide exposure with the analysis of criticality along the road network. The exposure assessment follows a matrix-based approach combining three indicators: a statistical susceptibility index, displacement measurements derived from Advanced Differential Synthetic Aperture Radar Interferometry (A-DInSAR), and damage severity derived from virtual surveys using Google Street View. The criticality of the road stretches is quantified based on the reduction in network efficiency under disruption scenarios. The methodology was applied to the road networks in the municipalities of Vaglio Basilicata, Brindisi Montagna and Trivigno (Basilicata region, southern Italy), which are highly affected by slow-moving landslides. The results indicate that, although approximately 31% of the network intersects slow-moving landslides, only 5% of the road stretches are classified at very high level of priority. This highlights the critical role of network topology in influencing risk-mitigation priorities. The proposed framework provides a cost-effective, flexible tool for local administrations to optimize resource allocation and prioritize site-specific investigations.