Two pilot case studies for indirect bridge scour monitoring using low-cost remote sensing for river flow characterisations

Bridge scour is a leading cause of bridge failures worldwide, exacerbated by climate change and increasing flood risks. Real-time data collection plays a critical role in effective flood risk management and decision-making, ultimately enhancing infrastructure resilience. The EU-funded RAMOBRIS (Risk Assessment and Monitoring for Bridges under Scour Hazard) project investigated cost-effective monitoring approaches to develop a novel, multidisciplinary strategy for assessing the risk of critical bridges exposed to scour. This manuscript outlines the monitoring strategy developed during the project, with a focus on the application of cost-effective sensors for hydraulic monitoring. The adopted methodology employs an indirect approach using low-cost remote sensing sensors to assess hydraulic properties and estimate scour depth through advanced formulas. Two pilot case studies were conducted on high-risk masonry bridges over the River Nith in Scotland. Various sensors were installed to evaluate their effectiveness in capturing hydraulic data and monitoring scour dynamics. Data from low-cost sensors were evaluated against data collected from higher-cost sensors or other available datasets. The results showed that low-cost sensors for measuring water levels provided accuracy comparable to high-cost radar systems, while being more cost-effective and easier to install. Video data from solar cameras enabled extensive measurements of surface velocity and discharge, improving the understanding of flow dynamics. The study confirmed the feasibility of using image velocimetry techniques for long-term estimation of river velocity and discharge, although further validation is required. These findings highlight the potential of low-cost and innovative sensor technologies. The open-access dataset generated in this study, which will be periodically updated with new data, provides a valuable resource of real-world information for ongoing research in hydraulic monitoring and bridge safety assessment.