Risk assessment of bridges affected by subsidence and landslides using ground and spaceborne monitoring: a global study

Bridges are a core element of transport systems, enabling connectivity and supporting access to employment, education, medical care and emergency response. Despite this central role, they are also among the most fragile assets in these networks, as they are frequently exposed to natural hazards whose occurrence and intensity are expected to grow under changing climatic conditions. Although assessing geo-hazard risk to bridges is essential for meeting the United Nations Sustainable Development Goals, current risk evaluation practices rarely account for how structural vulnerability evolves over time. In particular, they overlook the contribution of continuous monitoring technologies such as Structural Health Monitoring (SHM) sensors and Interferometric Synthetic Aperture radar (InSAR), which can provide ongoing information on bridge condition. Furthermore, while SHM installations remain limited, the global capacity of InSAR to complement these systems for bridge surveillance has not yet been systematically quantified.

This study introduces a new framework for assessing bridge geo-hazard risk worldwide that explicitly incorporates the availability of both ground-based SHM and satellite-derived monitoring. The assessment integrates subsidence and landslide hazards with measures of exposure and structural vulnerability.

A global analysis of satellite monitoring coverage reveals a substantial shortfall in current observation capability. Only a small fraction of long-span bridges is equipped with SHM systems, whereas InSAR observations from Sentinel-1 could potentially cover a far larger share of the global bridge inventory. Expanding the use of this spaceborne data could therefore lower overall geo-hazard risk and reduce the number of bridges categorised as high risk. Many of the structures that would remain in the high-risk category are also well-suited to satellite-based monitoring, underlining the value of InSAR for improving safety and resilience, particularly in low-income and resource-constrained regions. By linking risk with monitoring suitability, the proposed framework highlights that the presence of SHM and InSAR sensors enables more dynamic and time-sensitive risk evaluation, providing practical guidance for prioritising satellite monitoring, SHM deployment, and on-site inspections within a risk-informed decision-making process.