Digital Flood Surveys Help Network Rail Reopen Bridges Faster

More than 500 bridges on the UK rail network are classed as high risk for scour – erosion around foundations caused by fast-flowing rivers.

When water levels rise above set thresholds, these structures must be closed until inspections confirm they are safe, often leading to costly disruption.

Closures can generate significant “delay minute” charges for Network Rail, particularly on busy routes. Traditionally, post-flood inspections rely on divers, who must wait for safe conditions and often work in poor visibility, meaning bridges can remain shut for days.

Some regions are now using a sonar and laser-based survey system from specialist Ultrabeam to speed up assessments. The technology captures detailed underwater bathymetric scans alongside above-water laser data to create a 3D digital model of the bridge and riverbed. Engineers then use hydraulic modelling to assess scour risk with far greater precision than traditional manual surveys.

The system proved its value during flooding at Evesham Viaduct on the River Avon in November 2024. Ultrabeam arrived within 24 hours and completed a survey and data analysis in four hours, enabling the bridge to reopen the same day. Divers were unable to enter the water for another seven days, with Network Rail estimating the rapid reopening avoided around £3.5M in delay costs.

Beyond emergency response, the technology is being used to refine scour risk classifications. Of the 508 bridges on Network Rail’s high-risk register, some may be downgraded following detailed surveys, potentially reducing unnecessary precautionary closures.

Engineers say the approach represents a significant step forward in balancing safety with operational efficiency, particularly as extreme weather events become more frequent.