Specialist engineers have worked on 50 structures to safeguard them against scour damage over the past four years.
Scour damage occurs when fast-flowing water erodes material around the foundations and is the leading cause of bridge failures on the railway over the last 100-years, which can result in having restrictions placed on them.
Working mainly from river level, much of the work at each bridge involved setting up a portable dam system to reduce the water flow.
A scour mattress was laid to the contours of the riverbed and the pockets were filled with concrete. The mattress was then covered with the original riverbed material so the area looks the same as it did prior to work starting.
It's all designed to extend the lifespan of these structures, as the majority were built in the late 19th century, while helping to protect them against weather damage as part of a wider maintenance programme.
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Inver Viaduct, which carries passenger and freight services on the Highland Mainline over the River Braan in Dunkeld, is the last bridge to be completed. The line there has been closed three times over the last two years due to the river breaching safe levels and disrupting services.
Alex Hynes, managing director of Scotland's Railway, said: "We have a responsibility to make sure assets that play such a vital role on our network are maintained to help minimise the impact of rising water levels during extreme weather, allowing us to keep trains running.
"This is all part of our commitment to dealing with the impact of climate change on Scotland's Railway. The team has done a superb job in delivering this vital work, it'll help further improve the operational resilience, safety, and performance of the railway for our customers."
Jeremy Spence, Route Delivery Director, said: "Scour protection can be one of the more challenging elements of our renewals programme, as it involves working from river level much of the time and often in areas with challenging topography that can make access difficult for our teams.
"This has been a huge undertaking by the team since the work started in 2019 and it's great to see the successful completion of all 50 structures. The collaborative effort by Network Rail and Story has not only delivered this project on time but means we won't need to carry out repairs on this scale for many years to come."
